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1.  The pattern and diagnostic criteria of sensory neuronopathy: a case–control study 
Brain  2009;132(7):1723-1733.
Acquired sensory neuronopathies encompass a group of paraneoplastic, dysimmune, toxic or idiopathic disorders characterized by degeneration of peripheral sensory neurons in dorsal root ganglia. As dorsal root ganglia cannot easily be explored, the clinical diagnosis of these disorders may be difficult. The question as to whether there exists a common clinical pattern of sensory neuronopathies, allowing the establishment of validated and easy-to-use diagnostic criteria, has not yet been addressed. In this study, logistic regression was used to construct diagnostic criteria on a retrospective study population of 78 patients with sensory neuronopathies and 56 with other sensory neuropathies. For this, sensory neuronopathy was provisionally considered as unambiguous in 44 patients with paraneoplastic disorder or cisplatin treatment and likely in 34 with a dysimmune or idiopathic setting who may theoretically have another form of neuropathy. To test the homogeneity of the sensory neuronopathy population, likely candidates were compared with unambiguous cases and then the whole population was compared with the other sensory neuropathies population. Criteria accuracy was checked on 37 prospective patients referred for diagnosis of sensory neuropathy. In the study population, sensory neuronopathy showed a common clinical and electrophysiological pattern that was independent of the underlying cause, including unusual forms with only patchy sensory loss, mild electrical motor nerve abnormalities and predominant small fibre or isolated lower limb involvement. Logistic regression allowed the construction of a set of criteria that gave fair results with the following combination: ataxia in the lower or upper limbs + asymmetrical distribution + sensory loss not restricted to the lower limbs + at least one sensory action potential absent or three sensory action potentials <30% of the lower limit of normal in the upper limbs + less than two nerves with abnormal motor nerve conduction study in the lower limbs.
doi:10.1093/brain/awp136
PMCID: PMC2702838  PMID: 19506068
sensory neuronopathy; sensory ganglionopathy; sensory neuropathy; paraneoplastic neurological syndrome; cisplatin
2.  Towards a concept of disorders of “higher vestibular function” 
Background: Vestibular disorders are commonly characterized by a combination of perceptual, ocular motor, postural, and vegetative manifestations, which cause the symptoms of vertigo, nystagmus, ataxia, and nausea. Multisensory convergence and numerous polysynaptic pathways link the bilaterally organized central vestibular network with limbic, hippocampal, cerebellar, and non-vestibular cortex structures to mediate “higher” cognitive functions.
Anatomical classification of vestibular disorders: The traditional classification of vestibular disorders is based on the anatomical site of the lesion. While it distinguishes between the peripheral and the central vestibular systems, certain weaknesses become apparent when applied clinically. There are two reasons for this: first, peripheral and central vestibular disorders cannot always be separated by the clinical syndrome; second, a third category, namely disorders of “higher vestibular function”, is missing. These disorders may be caused by peripheral as well as central vestibular lesions.
Functional classification: Here we discuss a new concept of disorders of higher vestibular function which involve cognition and more than one sensory modality. Three conditions are described that exemplify such higher disorders: room tilt illusion, spatial hemineglect, and bilateral vestibulopathy all of which present with deficits of orientation and spatial memory.
Conclusions: Further elaboration of such disorders of higher multisensory functions with respect to lesion site and symptomatology is desirable. The room tilt illusion and spatial hemineglect involve vestibular and visual function to the extent that both conditions can be classified as either disorders of higher vestibular or of higher visual functions. A possible way of separating these disorders in a first step is to determine whether the causative lesion site affects the vestibular or the visual system. For the vestibular system this lesion site may be peripheral or central. The criterion of “higher function” is fulfilled if cognition or senses other than the primarily affected one come into play.
doi:10.3389/fnint.2014.00047
PMCID: PMC4041089  PMID: 24917796
central vestibular disorders; vestibular cognition; higher vestibular functions; room-tilt illusion; spatial neglect
3.  Cerebellar ataxia, areflexia, pes cavus, optic atrophy, and sensorineural hearing loss (CAPOS): a new syndrome. 
Journal of Medical Genetics  1996;33(5):419-421.
There are a large number of well recognised syndromes comprising cerebellar ataxia in association with other neurological features. We report three family members who presented with a relapsing, early onset cerebellar ataxia, associated with progressive optic atrophy and sensorineural deafness. All three patients have areflexia (in the absence of a peripheral neuropathy), a pes cavus deformity, and show varying degrees of severity. Extensive neurological investigations have been normal, and the aetiology and pathophysiology of this disorder remain unclear. This may represent a separate syndrome of early onset cerebellar ataxia with associated features ("cerebellar ataxia plus"), which is likely to either have an autosomal dominant or maternal mitochondrial pattern of inheritance. The recognition of this association under the acronym of CAPOS (cerebellar ataxia, areflexia, pes cavus, optic atrophy, and sensorineural deafness) may help in the delineation of a new syndrome.
PMCID: PMC1050615  PMID: 8733056
4.  Can loss of muscle spindle afferents explain the ataxic gait in Riley–Day syndrome? 
Brain  2011;134(11):3198-3208.
The Riley–Day syndrome is the most common of the hereditary sensory and autonomic neuropathies (Type III). Among the well-recognized clinical features are reduced pain and temperature sensation, absent deep tendon reflexes and a progressively ataxic gait. To explain the latter we tested the hypothesis that muscle spindles, or their afferents, are absent in hereditary sensory and autonomic neuropathy III by attempting to record from muscle spindle afferents from a nerve supplying the leg in 10 patients. For comparison we also recorded muscle spindles from 15 healthy subjects and from two patients with hereditary sensory and autonomic neuropathy IV, who have profound sensory disturbances but no ataxia. Tungsten microelectrodes were inserted percutaneously into fascicles of the common peroneal nerve at the fibular head. Intraneural stimulation within muscle fascicles evoked twitches at normal stimulus currents (10–30 µA), and deep pain (which often referred) at high intensities (1 mA). Microneurographic recordings from muscle fascicles revealed a complete absence of spontaneously active muscle spindles in patients with hereditary sensory and autonomic neuropathy III; moreover, responses to passive muscle stretch could not be observed. Conversely, muscle spindles appeared normal in patients with hereditary sensory and autonomic neuropathy IV, with mean firing rates of spontaneously active endings being similar to those recorded from healthy controls. Intraneural stimulation within cutaneous fascicles evoked paraesthesiae in the fascicular innervation territory at normal stimulus intensities, but cutaneous pain was never reported during high-intensity stimulation in any of the patients. Microneurographic recordings from cutaneous fascicles revealed the presence of normal large-diameter cutaneous mechanoreceptors in hereditary sensory and autonomic neuropathy III. Our results suggest that the complete absence of functional muscle spindles in these patients explains their loss of deep tendon reflexes. Moreover, we suggest that their ataxic gait is sensory in origin, due to the loss of functional muscle spindles and hence a compromised sensorimotor control of locomotion.
doi:10.1093/brain/awr168
PMCID: PMC3212710  PMID: 22075519
congenital insensitivity to pain; familial dysautonomia; HSAN; microneurography; muscle spindles; peripheral nerve; Riley–Day syndrome
5.  Hereditary sensory neuropathy type I 
Hereditary sensory neuropathy type I (HSN I) is a slowly progressive neurological disorder characterised by prominent predominantly distal sensory loss, autonomic disturbances, autosomal dominant inheritance, and juvenile or adulthood disease onset. The exact prevalence is unknown, but is estimated as very low. Disease onset varies between the 2nd and 5th decade of life. The main clinical feature of HSN I is the reduction of sensation sense mainly distributed to the distal parts of the upper and lower limbs. Variable distal muscle weakness and wasting, and chronic skin ulcers are characteristic. Autonomic features (usually sweating disturbances) are invariably observed. Serious and common complications are spontaneous fractures, osteomyelitis and necrosis, as well as neuropathic arthropathy which may even necessitate amputations. Some patients suffer from severe pain attacks. Hypacusis or deafness, or cough and gastrooesophageal reflux have been observed in rare cases. HSN I is a genetically heterogenous condition with three loci and mutations in two genes (SPTLC1 and RAB7) identified so far. Diagnosis is based on the clinical observation and is supported by a family history. Nerve conduction studies confirm a sensory and motor neuropathy predominantly affecting the lower limbs. Radiological studies, including magnetic resonance imaging, are useful when bone infections or necrosis are suspected. Definitive diagnosis is based on the detection of mutations by direct sequencing of the SPTLC1 and RAB7 genes. Correct clinical assessment and genetic confirmation of the diagnosis are important for appropriate genetic counselling and prognosis. Differential diagnosis includes the other hereditary sensory and autonomic neuropathies (HSAN), especially HSAN II, as well as diabetic foot syndrome, alcoholic neuropathy, neuropathies caused by other neurotoxins/drugs, immune mediated neuropathy, amyloidosis, spinal cord diseases, tabes dorsalis, lepra neuropathy, or decaying skin tumours like amelanotic melanoma. Management of HSN I follows the guidelines given for diabetic foot care (removal of pressure to the ulcer and eradication of infection, followed by the use of specific protective footwear) and starts with early and accurate counselling of patients about risk factors for developing foot ulcerations. The disorder is slowly progressive and does not influence life expectancy but is often severely disabling after a long duration of the disease.
doi:10.1186/1750-1172-3-7
PMCID: PMC2311280  PMID: 18348718
6.  Recessive C10orf2 mutations in a family with infantile-onset spinocerebellar ataxia, sensorimotor polyneuropathy, and myopathy 
Neurogenetics  2014;15(3):171-182.
Recessive mutations in chromosome 10 open reading frame 2 (C10orf2) are relevant in infantile-onset spinocerebellar ataxia (IOSCA). In this study, we investigated the causative mutation in a Korean family with combined phenotypes of IOSCA, sensorimotor polyneuropathy, and myopathy. We investigated recessive mutations in a Korean family with two individuals affected by IOSCA. Causative mutations were investigated using whole exome sequencing. Electrophysiological analyses and muscle and nerve biopsies were performed, along with magnetic resonance imaging (MRI) of the brain and lower extremities. Compound heterozygous mutations c.1460C>T and c.1485-1G>A in C10orf2 were identified as causative of IOSCA. Skeletal muscle showed mitochondrial DNA (mtDNA) deletions. Both patients showed a period of normal development until 12–15 months, followed by ataxia, athetosis, hearing loss, and intellectual disability. Electrophysiological findings indicated motor and sensory polyneuropathies. Muscle biopsy revealed variations in the size and shape of myofibers with scattered, small, and angulated degenerating myofibers containing abnormal mitochondria; these observations are consistent with myopathy and may be the result of mtDNA deletions. Sural nerve biopsy revealed an axonal neuropathy. High-signal-intensity lesions in the middle cerebellar peduncles were correlated with clinical severity, and MRI of the lower legs was compatible with the hypothesis of length-dependent axonal degeneration. We identified novel compound heterozygous mutations of the C10orf2 gene as the cause of IOSCA with sensorimotor polyneuropathy and myopathy. Signs of motor neuropathy and myopathy were discovered for the first time in IOSCA patients with C10orf2 mutations. These results suggest that the clinical spectrum of IOSCA caused by C10orf2 mutations may be more variable than previously reported.
Electronic supplementary material
The online version of this article (doi:10.1007/s10048-014-0405-1) contains supplementary material, which is available to authorized users.
doi:10.1007/s10048-014-0405-1
PMCID: PMC4102772  PMID: 24816431
C10orf2; Whole exome sequencing (WES); Infantile-onset spinocerebellar ataxia (IOSCA); Neuropathy; Myopathy; Mitochondria
7.  Axonal neuropathy associated with monoclonal gammopathy of undetermined significance 
OBJECTIVE—The neuropathy associated with monoclonal gammopathy of undetermined significance (MGUS) is typically a predominantly demyelinating process that may have additional features of axonal degeneration. Sixteen patients with MGUS and a pure or predominantly axonal neuropathy are reported and compared with 20 consecutive patients with demyelinating neuropathy and MGUS who were seen during the same period.
METHODS—Retrospective review of a consecutive series of patients with neuropathy and MGUS evaluated during a five year period.
RESULTS—The axonal group had mild, symmetric, slowly progressive, predominantly sensory neuropathy, usually limited to the legs. There were no differences in the age of onset or duration of symptoms at the time of presentation, initial symptoms, or the severity of weakness between the axonal and demyelinating cases. However, the axonal process was associated with less vibration and proprioceptive loss, did not include leg ataxia (present in 55% of patients with demyelinating type), less often had generalised areflexia (19% v 70%), IgM gammopathy (19% v 80%), and anti-MAG antibodies (0% v 40%), and had lower CSF protein concentrations (mean, 49 v 100mg/dl). The illness was also generally milder with less disability (mean Rankin score 2.1 v 2.8). Fewer patients with axonal neuropathy improved with immunomodulating therapy (27% v 75%).
CONCLUSION—There is an axonal neuropathy associated with MGUS that is clinically and electrophysiologically distinct from the more typical demyelinating pattern.


PMCID: PMC2169654  PMID: 9285452
8.  The genetics of ataxia: through the labyrinth of the Minotaur, looking for Ariadne’s thread 
Journal of Neurology  2014;261(Suppl 2):528-541.
Among the hereditary cerebellar ataxias (CAs), there are at least 36 different forms of autosomal dominant cerebellar ataxia (ADCAs), 20 autosomal recessive cerebellar ataxias (ARCAs), two X-linked ataxias, and several forms of ataxia associated with mitochondrial defects. Despite the steady increase in the number of newly discovered CA genes, patients, especially those with putative ARCAs, cannot yet be genotyped. Moreover, in daily clinical practice, ataxia may present as an isolated cerebellar syndrome or, more often, it is associated with a broad spectrum of neurological manifestations including pyramidal, extrapyramidal, sensory, and cognitive dysfunction. Furthermore, non-neurological symptoms may also coexist. A close integration between clinical records, neurophysiological, neuroradiological and, in some instances, biochemical findings will help physicians in the diagnostic work-up (including selection of the correct genetic tests) and may lead to timely therapy. Some inherited CAs are in fact potentially treatable, and the efficacy of the therapy is directly related to the severity of the cerebellar atrophy and to the time of onset of the disease. Most cases of CA are sporadic, and the diagnostic work-up remains a challenge. Detailed anamnesis and deep investigation of the family pedigree are usually enough to discriminate between acquired and genetic conditions. In the case of ADCA, molecular testing should be guided by taking into account the main associated symptoms. In sporadic cases, a multi-disciplinary approach is needed and should consider the following points: (1) onset and clinical course; (2) associated features; (3) neurophysiological parameters, with special attention to the occurrence of peripheral neuropathy; (4) neuroimaging results; and (5) laboratory findings. A late-onset sporadic ataxia, in which other possible causes have been excluded by following the proposed steps, might be attributable to metabolic disorders, which in some instances may be treatable. In this review, we will guide the reader through the labyrinth of CAs, and we propose a diagnostic flow chart.
doi:10.1007/s00415-014-7387-7
PMCID: PMC4141148  PMID: 25145890
Ataxia; Cerebellum; Diagnosis; Genes; Metabolism
9.  Neurophysiological testing correlates with clinical examination according to fibre type involvement and severity in sensory neuropathy 
Objective: To investigate a comprehensive battery of neurophysiological tests for objective evaluation of sensory neuropathies including fibre type involvement and severity, and to determine the relation between neurophysiological data and clinical examination.
Methods: 45 patients referred for sensory neuropathy were studied using a standardised clinical evaluation of large and small fibre symptoms and an original neurophysiological battery. Clinical evaluation included: assessment of tactile, vibratory, and pin sensation; tendon reflexes; toe position sense; ataxia score; pain level; and presence of trophic, vasomotor, or sudomotor abnormalities. The neurophysiological battery included: recording of large fibre and small fibre components of the sural sensory nerve action potential; somatosensory evoked cortical potentials and soleus H reflex following tibial nerve electrical stimulation; laser evoked potentials following Nd:YAG laser stimulation of the foot; and plantar sympathetic skin response to median nerve stimulation. Neuropathy was classified according to the predominantly affected fibre type, and a severity score was established based on clinical and neurophysiological abnormalities.
Results: On clinical examination there were 22 patients with large fibre sensory neuropathy (LFSN), 18 with mixed sensory neuropathy (MSN), and five with small fibre sensory neuropathy (SFSN). Neurophysiological classification identified 25 patients with LFSN, 13 with MSN, and seven with SFSN. Clinical and neurophysiological classifications and severity scores were correlated, whatever the type of neuropathy.
Conclusions: The correlation between clinical examination and the results of an original neurophysiological test battery offers a comprehensive clinical and neurophysiological approach to the objective assessment of peripheral neuropathies according to fibre type involvement and overall severity.
doi:10.1136/jnnp.2003.019208
PMCID: PMC1738954  PMID: 14966158
10.  Neuro-Otological Aspects of Cerebellar Stroke Syndrome 
Cerebellar stroke is a common cause of a vascular vestibular syndrome. Although vertigo ascribed to cerebellar stroke is usually associated with other neurological symptoms or signs, it may mimic acute peripheral vestibulopathy (APV), so called pseudo-APV. The most common pseudo-APV is a cerebellar infarction in the territory of the medial branch of the posterior inferior cerebellar artery (PICA). Recent studies have shown that a normal head impulse result can differentiate acute medial PICA infarction from APV. Therefore, physicians who evaluate stroke patients should be trained to perform and interpret the results of the head impulse test. Cerebellar infarction in the territory of the anterior inferior cerebellar artery (AICA) can produce a unique stroke syndrome in that it is typically accompanied by unilateral hearing loss, which could easily go unnoticed by patients. The low incidence of vertigo associated with infarction involving the superior cerebellar artery distribution may be a useful way of distinguishing it clinically from PICA or AICA cerebellar infarction in patients with acute vertigo and limb ataxia. For the purpose of prompt diagnosis and adequate treatment, it is imperative to recognize the characteristic patterns of the clinical presentation of each cerebellar stroke syndrome. This paper provides a concise review of the key features of cerebellar stroke syndromes from the neuro-otology viewpoint.
doi:10.3988/jcn.2009.5.2.65
PMCID: PMC2706413  PMID: 19587812
cerebellar stroke; vertigo; hearing loss; pseudo-APV; head impulse test
11.  Trigeminal isolated sensory neuropathy (TISN) and FOSMN syndrome: despite a dissimilar disease course do they share common pathophysiological mechanisms? 
BMC Neurology  2014;14(1):248.
Background
Patients presenting with bilateral trigeminal hypoesthesia may go on to have trigeminal isolated sensory neuropathy, a benign, purely trigeminal neuropathy, or facial-onset sensory motor neuronopathy (FOSMN), a malignant life-threatening condition. No diagnostic criteria can yet differentiate the two conditions at their onset. Nor is it clear whether the two diseases are distinct entities or share common pathophysiological mechanisms.
Methods
Seeking pathophysiological and diagnostic information to distinguish these two conditions at their onset, in this neurophysiological and morphometric study we neurophysiologically assessed function in myelinated and unmyelinated fibres and histologically examined supraorbital nerve biopsy specimens with optic and electron microscopy in 13 consecutive patients with recent onset trigeminal hypoesthesia and pain.
Results
The disease course distinctly differed in the 13 patients. During a mean 10 year follow-up whereas in eight patients the disease remained relatively stable, in the other five it progressed to possibly life-threatening motor disturbances and extra-trigeminal spread. From two to six years elapsed between the first sensory symptoms and the onset of motor disorders. In patients with trigeminal isolated sensory neuropathy (TISN) and in those with FOSMN neurophysiological and histological examination documented a neuronopathy manifesting with trigeminal nerve damage selectively affecting myelinated fibres, but sparing the Ia-fibre-mediated proprioceptive reflex.
Conclusions
Although no clinical diagnostic criteria can distinguish the two conditions at onset, neurophysiological and nerve-biopsy findings specify that in both disorders trigeminal nerve damage manifests as a dissociated neuronopathy affecting myelinated and sparing unmyelinated fibres, thus suggesting similar pathophysiological mechanisms.
doi:10.1186/s12883-014-0248-2
PMCID: PMC4301795  PMID: 25527047
Trigeminal nerve; Neuronopathy; Trigeminal neuropathy; FOSMN; Facial pain
12.  Autosomal recessive spastic ataxia of Charlevoix Saguenay (ARSACS): expanding the genetic, clinical and imaging spectrum 
Background
Mutations in SACS, leading to autosomal-recessive spastic ataxia of Charlevoix-Saguenay (ARSACS), have been identified as a frequent cause of recessive early-onset ataxia around the world. Here we aimed to enlarge the spectrum of SACS mutations outside Quebec, to establish the pathogenicity of novel variants, and to expand the clinical and imaging phenotype.
Methods
Sequencing of SACS in 22 patients with unexplained early-onset ataxia, assessment of novel SACS variants in 3.500 European control chromosomes and extensive phenotypic investigations of all SACS carriers.
Results
We identified 11 index patients harbouring 17 novel SACS variants. 9/11 patients harboured two variants of at least probable pathogenicity which were not observed in controls and, in case of missense mutations, were located in highly conserved domains. These 9 patients accounted for at least 11% (9/83) in our series of unexplained early onset ataxia subjects. While most patients (7/9) showed the classical ARSACS triad, the presenting phenotype reached from pure neuropathy (leading to the initial diagnosis of Charcot-Marie-Tooth disease) in one subject to the absence of any signs of neuropathy in another. In contrast to its name “spastic ataxia”, neither spasticity (absent in 2/9=22%) nor extensor plantar response (absent in 3/9=33%) nor cerebellar ataxia (absent in 1/9=11%) were obligate features. Autonomic features included urine urge incontinence and erectile dysfunction. Apart from the well-established MRI finding of pontine hypointensities, all patients (100%) showed hyperintensities of the lateral pons merging into the (thickened) middle cerebellar peduncles. In addition, 63% exhibited bilateral parietal cerebral atrophy, and 63% a short circumscribed thinning of the posterior midbody of the corpus callosum. In 2 further patients with differences in important clinical features, VUS class 3 variants (c.1373C>T [p.Thr458Ile] and c.2983 G>T [p.Val995Phe]) were identified. These variants were, however, also observed in controls, thus questioning their pathogenic relevance.
Conclusions
We here demonstrate that each feature of the classical ARSACS triad (cerebellar ataxia, spasticity and peripheral neuropathy) might be missing in ARSACS. Nevertheless, characteristic MRI features – which also extend to supratentorial regions and involve the cerebral cortex – will help to establish the diagnosis in most cases.
doi:10.1186/1750-1172-8-41
PMCID: PMC3610264  PMID: 23497566
Ataxia; Recessive ataxia; Spastic ataxia; Early onset ataxia; Spasticity; Genetics; Magnetic resonance imaging; Electrophysiology; Thin corpus callosum; Charcot Marie Tooth; Hereditary spastic paraplegia
13.  Diagnostic approach to peripheral neuropathy 
Peripheral neuropathy refers to disorders of the peripheral nervous system. They have numerous causes and diverse presentations; hence, a systematic and logical approach is needed for cost-effective diagnosis, especially of treatable neuropathies. A detailed history of symptoms, family and occupational history should be obtained. General and systemic examinations provide valuable clues. Neurological examinations investigating sensory, motor and autonomic signs help to define the topography and nature of neuropathy. Large fiber neuropathy manifests with the loss of joint position and vibration sense and sensory ataxia, whereas small fiber neuropathy manifests with the impairment of pain, temperature and autonomic functions. Electrodiagnostic (EDx) tests include sensory, motor nerve conduction, F response, H reflex and needle electromyography (EMG). EDx helps in documenting the extent of sensory motor deficits, categorizing demyelinating (prolonged terminal latency, slowing of nerve conduction velocity, dispersion and conduction block) and axonal (marginal slowing of nerve conduction and small compound muscle or sensory action potential and dennervation on EMG). Uniform demyelinating features are suggestive of hereditary demyelination, whereas difference between nerves and segments of the same nerve favor acquired demyelination. Finally, neuropathy is classified into mononeuropathy commonly due to entrapment or trauma; mononeuropathy multiplex commonly due to leprosy and vasculitis; and polyneuropathy due to systemic, metabolic or toxic etiology. Laboratory investigations are carried out as indicated and specialized tests such as biochemical, immunological, genetic studies, cerebrospinal fluid (CSF) examination and nerve biopsy are carried out in selected patients. Approximately 20% patients with neuropathy remain undiagnosed but the prognosis is not bad in them.
doi:10.4103/0972-2327.41875
PMCID: PMC2771953  PMID: 19893645
Axonal demyelination; diagnosis; nerve conduction; peripheral neuropathy
14.  Spinocerebellar ataxias – genotype-phenotype correlations in 104 Brazilian families 
Clinics  2012;67(5):443-449.
OBJECTIVE:
Spinocerebellar ataxias are neurodegenerative disorders involving the cerebellum and its connections. There are more than 30 distinct subtypes, 16 of which are associated with an identified gene. The aim of the current study was to evaluate a large group of patients from 104 Brazilian families with spinocerebellar ataxias.
METHODS:
We studied 150 patients from 104 families with spinocerebellar ataxias who had received molecular genetic testing for spinocerebellar ataxia types 1, 2, 3, 6, 7, 8, 10, 12, 17, and dentatorubral-pallidoluysian atrophy. A statistical analysis of the results was performed using basic descriptive statistics and the correlation coefficient (r), Student's t-test, chi-square test, and Yates' correction. The statistical significance level was established for p-values <0.05.
RESULTS:
The results show that the most common subtype was spinocerebellar ataxia 3, which was followed by spinocerebellar ataxia 10. Moreover, the comparison between patients with spinocerebellar ataxia 3, spinocerebellar ataxia 10, and other types of spinocerebellar ataxia revealed distinct clinical features for each type. In patients with spinocerebellar ataxia 3, the phenotype was highly pleomorphic, although the most common signs of disease included cerebellar ataxia (CA), ophthalmoplegia, diplopia, eyelid retraction, facial fasciculation, pyramidal signs, and peripheral neuropathy. In patients with spinocerebellar ataxia 10, the phenotype was also rather distinct and consisted of pure cerebellar ataxia and abnormal saccadic eye movement as well as ocular dysmetria. Patients with spinocerebellar ataxias 2 and 7 presented highly suggestive features of cerebellar ataxia, including slow saccadic ocular movements and areflexia in spinocerebellar ataxia 2 and visual loss in spinocerebellar ataxia 7.
CONCLUSIONS:
Spinocerebellar ataxia 3 was the most common subtype examined, followed by spinocerebellar ataxia 10. Patients with spinocerebellar ataxia 2 and 7 demonstrated highly suggestive features, whereas the phenotype of spinocerebellar ataxia 3 patients was highly pleomorphic and spinocerebellar ataxia 10 patients exhibited pure cerebellar ataxia. Epilepsy was absent in all of the patients with spinocerebellar ataxia 10 in this series.
doi:10.6061/clinics/2012(05)07
PMCID: PMC3351252  PMID: 22666787
Spinocerebellar Ataxias; Cerebellar Ataxia; Cerebellar Atrophy; SCA3; SCA10
15.  Sensory neuronopathy complicating systemic lupus erythematosus: a case report 
Introduction
Systemic lupus erythematosus is a multi-system connective tissue disorder. Peripheral neuropathy is a known and underestimated complication in systemic lupus erythematosus. Ganglionopathy manifests when neuronal cell bodies in the dorsal root ganglion are involved. Autoimmune disorders are a known etiology, with systemic lupus erythematosus being a rare cause.
Case presentation
A 32-year-old South Asian woman presented with oral ulceration involving her lips following initiation of treatment for a febrile illness associated with dysuria. She had a history of progressively worsening numbness over a period of 4 months involving both the upper and lower limbs symmetrically while sparing the trunk. Her vibration sense was impaired, and her reflexes were diminished. For the past 4 years, she had had a bilateral, symmetrical, non-deforming arthritis involving the upper and lower limbs. Her anti-nuclear antibody and anti-double-stranded deoxyribonucleic acid status were positive. Although her anti-Ro antibodies were positive, she did not have clinical features suggestive of Sjögren syndrome. Nerve conduction studies revealed sensory neuronopathy. A diagnosis of systemic lupus erythematosus complicated by sensory neuronopathy was made. Treatment with intravenous immunoglobulin resulted in clinical and electrophysiological improvement.
Conclusion
Peripheral neuropathy in systemic lupus erythematosus can, by itself, be a disabling feature. Nerve conduction studies should be considered when relevant. Neuropathy in systemic lupus erythematosus should be given greater recognition, and rarer forms of presentation should be entertained in the differential diagnosis when the clinical picture is atypical. Intravenous immunoglobulin may have role in treatment of sensory neuronopathy in systemic lupus erythematosus.
doi:10.1186/1752-1947-8-141
PMCID: PMC4229803  PMID: 24884917
Dorsal root ganglionopathy; Intravenous immunoglobulins; Sensory neuronopathy; Systemic lupus erythematosus
16.  Spinocerebellar ataxia type 6: genotype and phenotype in German kindreds 
OBJECTIVE—Spinocerebellar ataxia type 6 (SCA6) is an autosomal dominant cerebellar ataxia (ADCA) of which the mutation causing the disease has recently been characterised as an expanded CAG trinucleotide repeat in the gene coding for the α1A-subunit of the voltage dependent calcium channel. The aim was to further characterise the SCA6 phenotype
METHODS—The SCA6 mutation was investigated in 69 German families with ADCA and 61 patients with idiopathic sporadic cerebellar ataxia and the CAG repeat length of the expanded allele was correlated with the disease phenotype.
RESULTS—Expanded alleles were found in nine of 69 families as well as in four patients with sporadic disease. Disease onset ranged from 30 to 71 years of age and was significantly later than in other forms of ADCA. Age at onset correlated inversely with repeat length. The SCA6 phenotype comprises predominantly cerebellar signs in concordance with isolated cerebellar atrophy on MRI. Non-cerebellar systems were only mildly affected with external ophthalmoplegia, spasticity, peripheral neuropathy, and parkinsonism. Neither these clinical signs nor progression rate correlated with CAG repeat length.
CONCLUSIONS—This study provides the first detailed characterisation of the SCA6 phenotype. Clinical features apart from cerebellar signs were highly variable in patients with SCA6. By comparison with SCA1, SCA2, and SCA3 no clinical or electrophysiological finding was specific for SCA6. Therefore, the molecular defect cannot be predicted from clinical investigations. In Germany, SCA6 accounts for about 13% of families with ADCA. However, up to 30% of SCA6 kindreds may be misdiagnosed clinically as sporadic disease due to late manifestation in apparently healthy parents. Genetic testing is therefore recommended for the SCA6 mutation also in patients with putative sporadic ataxia.


PMCID: PMC2169927  PMID: 9436730
17.  CMT2C with vocal cord paresis associated with short stature and mutations in the TRPV4 gene 
Neurology  2010;75(22):1968-1975.
Background:
Recently, mutations in the transient receptor potential cation channel, subfamily V, member 4 gene (TRPV4) have been reported in Charcot-Marie-Tooth Type 2C (CMT2C) with vocal cord paresis. Other mutations in this same gene have been described in separate families with various skeletal dysplasias. Further clarification is needed of the different phenotypes associated with this gene.
Methods:
We performed clinical evaluation, electrophysiology, and genetic analysis of the TRPV4 gene in 2 families with CMT2C.
Results:
Two multigenerational families had a motor greater than sensory axonal neuropathy associated with variable vocal cord paresis. The vocal cord paresis varied from absent to severe, requiring permanent tracheotomy in 2 subjects. One family with mild neuropathy also manifested pronounced short stature, more than 2 SD below the average height for white Americans. There was one instance of dolichocephaly. A novel S542Y mutation in the TRPV4 gene was identified in this family. The other family had a more severe, progressive, motor neuropathy with sensory loss, but less remarkable short stature and an R315W mutation in TRPV4. Third cranial nerve involvement and sleep apnea occurred in one subject in each family.
Conclusion:
CMT2C with axonal neuropathy, vocal cord paresis, and short stature is a unique syndrome associated with mutations in the TRPV4 gene. Mutations in TRPV4 can cause abnormalities in bone, peripheral nerve, or both and may result in highly variable orthopedic and neurologic phenotypes.
GLOSSARY
= compound muscle action potential;
= Charcot-Marie-Tooth;
= Charcot-Marie-Tooth Type 2C;
= hereditary motor and sensory neuropathy;
= nerve conduction velocity;
= restriction fragment length polymorphism;
= spinal muscular atrophy;
= sensory nerve action potential;
= scapuloperoneal spinal muscular atrophy.
doi:10.1212/WNL.0b013e3181ffe4bb
PMCID: PMC3014233  PMID: 21115951
18.  DNMT1 mutation hot spot causes varied phenotypes of HSAN1 with dementia and hearing loss 
Neurology  2013;80(9):824-828.
Background:
Mutations in DNA methyltransferase 1 (DNMT1) have been identified in 2 autosomal dominant syndromes: 1) hereditary sensory autonomic neuropathy with dementia and hearing loss (HSAN1E); and 2) cerebellar ataxia, deafness, and narcolepsy. Both syndromes have mutations in targeting sequence (TS) domain (exons 20–21), which is important in mediating DNA substrate binding to the DNMT1 catalytic domain. Frontal lobe hypometabolism has been documented in an HSAN1E family, but memory loss has been the primary cognitive complaint. The chromosomal location of the DNMT1 gene at 19p13.2 has been linked to familial late-onset Alzheimer disease.
Methods:
We sequenced 41 exons of DNMT1 and their flanking regions in 1) 2 kindreds with HSAN1E; 2) 48 patients with HSAN1 alone without dementia and hearing loss; and 3) 5 probands of familial frontotemporal dementia (FTD) kindreds. We also sequenced exon 20 and 21 in 364 autopsy-confirmed late-onset Alzheimer disease cases.
Results:
Mutations in DNMT1 were specific to 2 HSAN1E kindreds with dementia and hearing loss (no narcolepsy). One family carried previously identified mutation Tyr495Cys; the other carried a novel Tyr495His, both in the TS domain. The symptoms of these patients include prominent personality, psychiatric manifestations, and seizures in one and the onset time is later than the previously reported cases.
Conclusion:
Clinicians should consider DNMT1 mutations in patients presenting with FTD or primary memory decline who also have sensory neuropathy and hearing loss. Amino acid Tyr495 is a hot spot for HSAN1E, distinct from exon 21 mutations associated with narcolepsy.
doi:10.1212/WNL.0b013e318284076d
PMCID: PMC3598458  PMID: 23365052
19.  A variant of multifocal motor neuropathy with acute, generalised presentation and persistent conduction blocks 
Objective:Multifocal motor neuropathy with persistent conduction blocks is classically described as a chronic neuropathy with progressive onset, and acute forms have not previously been characterised. We report four cases of severe motor impairment with acute and generalised onset and with persistent motor conduction blocks.
Patients and results:An acute tetraparesis with diffuse areflexia but little or no sensory disturbance was the clinical picture. Serial electrophysiological tests showed persistent multifocal motor conduction blocks with absent F waves in most tested motor nerves. No or minor abnormalities of the sensory nerve action potentials were observed. Cerebrospinal fluid contained normal or mildly increased protein levels (<1 g/l) without cells. Campylobacter jejuni serology was negative in three patients and consistent with past infection in one patient. Anti-ganglioside antibodies were positive in three patients. A five day course of intravenous immunoglobulins produced nearly complete symptom resolution in three patients and was ineffective in one patient.
Conclusion:Because of the persistence of multifocal motor conduction blocks for several weeks or months as the isolated electrophysiological feature, these cases could not be consistent with Guillain–Barré syndrome or chronic inflammatory demyelinating polyneuropathy. They suggest an original variant of multifocal motor neuropathy with an acute and generalised initial presentation and persistent motor conduction blocks affecting all four limbs.
doi:10.1136/jnnp.74.11.1555
PMCID: PMC1738247  PMID: 14617715
20.  Treatable childhood neuronopathy caused by mutations in riboflavin transporter RFVT2 
Brain  2013;137(1):44-56.
Childhood onset motor neuron diseases or neuronopathies are a clinically heterogeneous group of disorders. A particularly severe subgroup first described in 1894, and subsequently called Brown-Vialetto-Van Laere syndrome, is characterized by progressive pontobulbar palsy, sensorineural hearing loss and respiratory insufficiency. There has been no treatment for this progressive neurodegenerative disorder, which leads to respiratory failure and usually death during childhood. We recently reported the identification of SLC52A2, encoding riboflavin transporter RFVT2, as a new causative gene for Brown-Vialetto-Van Laere syndrome. We used both exome and Sanger sequencing to identify SLC52A2 mutations in patients presenting with cranial neuropathies and sensorimotor neuropathy with or without respiratory insufficiency. We undertook clinical, neurophysiological and biochemical characterization of patients with mutations in SLC52A2, functionally analysed the most prevalent mutations and initiated a regimen of high-dose oral riboflavin. We identified 18 patients from 13 families with compound heterozygous or homozygous mutations in SLC52A2. Affected individuals share a core phenotype of rapidly progressive axonal sensorimotor neuropathy (manifesting with sensory ataxia, severe weakness of the upper limbs and axial muscles with distinctly preserved strength of the lower limbs), hearing loss, optic atrophy and respiratory insufficiency. We demonstrate that SLC52A2 mutations cause reduced riboflavin uptake and reduced riboflavin transporter protein expression, and we report the response to high-dose oral riboflavin therapy in patients with SLC52A2 mutations, including significant and sustained clinical and biochemical improvements in two patients and preliminary clinical response data in 13 patients with associated biochemical improvements in 10 patients. The clinical and biochemical responses of this SLC52A2-specific cohort suggest that riboflavin supplementation can ameliorate the progression of this neurodegenerative condition, particularly when initiated soon after the onset of symptoms.
doi:10.1093/brain/awt315
PMCID: PMC3891447  PMID: 24253200
childhood neuronopathy; Brown-Vialetto-Van Laere syndrome; riboflavin therapy; RFVT2; SLC52A2
21.  The relationship of nerve fibre pathology to sensory function in entrapment neuropathy 
Brain  2014;137(12):3186-3199.
The impact of peripheral entrapment neuropathies on target innervation remains unknown. Using quantitative sensory testing, neurophysiology and skin biopsies, Schmid et al. demonstrate that carpal tunnel syndrome affects large fibres and their nodal complexes, but is also associated with a reduction in the number and functioning of small sensory axons.
Surprisingly little is known about the impact of entrapment neuropathy on target innervation and the relationship of nerve fibre pathology to sensory symptoms and signs. Carpal tunnel syndrome is the most common entrapment neuropathy; the aim of this study was to investigate its effect on the morphology of small unmyelinated as well as myelinated sensory axons and relate such changes to somatosensory function and clinical symptoms. Thirty patients with a clinical and electrophysiological diagnosis of carpal tunnel syndrome [17 females, mean age (standard deviation) 56.4 (15.3)] and 26 age and gender matched healthy volunteers [18 females, mean age (standard deviation) 51.0 (17.3)] participated in the study. Small and large fibre function was examined with quantitative sensory testing in the median nerve territory of the hand. Vibration and mechanical detection thresholds were significantly elevated in patients with carpal tunnel syndrome (P < 0.007) confirming large fibre dysfunction and patients also presented with increased thermal detection thresholds (P < 0.0001) indicative of C and Aδ-fibre dysfunction. Mechanical and thermal pain thresholds were comparable between groups (P > 0.13). A skin biopsy was taken from a median nerve innervated area of the proximal phalanx of the index finger. Immunohistochemical staining for protein gene product 9.5 and myelin basic protein was used to evaluate morphological features of unmyelinated and myelinated axons. Evaluation of intraepidermal nerve fibre density showed a striking loss in patients (P < 0.0001) confirming a significant compromise of small fibres. The extent of Meissner corpuscles and dermal nerve bundles were comparable between groups (P > 0.07). However, patients displayed a significant increase in the percentage of elongated nodes (P < 0.0001), with altered architecture of voltage-gated sodium channel distribution. Whereas neither neurophysiology nor quantitative sensory testing correlated with patients’ symptoms or function deficits, the presence of elongated nodes was inversely correlated with a number of functional and symptom related scores (P < 0.023). Our findings suggest that carpal tunnel syndrome does not exclusively affect large fibres but is associated with loss of function in modalities mediated by both unmyelinated and myelinated sensory axons. We also document for the first time that entrapment neuropathies lead to a clear reduction in intraepidermal nerve fibre density, which was independent of electrodiagnostic test severity. The presence of elongated nodes in the target tissue further suggests that entrapment neuropathies affect nodal structure/myelin well beyond the focal compression site. Interestingly, nodal lengthening may be an adaptive phenomenon as it inversely correlates with symptom severity.
doi:10.1093/brain/awu288
PMCID: PMC4240296  PMID: 25348629
entrapment neuropathy; carpal tunnel syndrome; skin biopsy; nodes of Ranvier; small fibres; quantitative sensory testing
22.  Whole-Exome Sequencing Identifies Homozygous AFG3L2 Mutations in a Spastic Ataxia-Neuropathy Syndrome Linked to Mitochondrial m-AAA Proteases 
PLoS Genetics  2011;7(10):e1002325.
We report an early onset spastic ataxia-neuropathy syndrome in two brothers of a consanguineous family characterized clinically by lower extremity spasticity, peripheral neuropathy, ptosis, oculomotor apraxia, dystonia, cerebellar atrophy, and progressive myoclonic epilepsy. Whole-exome sequencing identified a homozygous missense mutation (c.1847G>A; p.Y616C) in AFG3L2, encoding a subunit of an m-AAA protease. m-AAA proteases reside in the mitochondrial inner membrane and are responsible for removal of damaged or misfolded proteins and proteolytic activation of essential mitochondrial proteins. AFG3L2 forms either a homo-oligomeric isoenzyme or a hetero-oligomeric complex with paraplegin, a homologous protein mutated in hereditary spastic paraplegia type 7 (SPG7). Heterozygous loss-of-function mutations in AFG3L2 cause autosomal-dominant spinocerebellar ataxia type 28 (SCA28), a disorder whose phenotype is strikingly different from that of our patients. As defined in yeast complementation assays, the AFG3L2Y616C gene product is a hypomorphic variant that exhibited oligomerization defects in yeast as well as in patient fibroblasts. Specifically, the formation of AFG3L2Y616C complexes was impaired, both with itself and to a greater extent with paraplegin. This produced an early-onset clinical syndrome that combines the severe phenotypes of SPG7 and SCA28, in additional to other “mitochondrial” features such as oculomotor apraxia, extrapyramidal dysfunction, and myoclonic epilepsy. These findings expand the phenotype associated with AFG3L2 mutations and suggest that AFG3L2-related disease should be considered in the differential diagnosis of spastic ataxias.
Author Summary
Mitochondria are cellular organelles important for converting sugar or fats into energy that cells can use for their functions and survival. Many neurological diseases are the result of mitochondrial dysfunction as affected cells are unable to cope with lowered energy supplies and increased oxidative stress. These deficiencies cause accumulation of cellular damage and eventually cell death. Spastic ataxias are neurological disorders involving cells with large energy requirements, the cerebellar Purkinje cells and the cerebral upper motor neurons. When these cells function improperly or die, individuals develop symptoms of incoordination (ataxia) and abnormal muscle tone in their legs (spastic paraplegia). Using emerging techniques of whole-exome sequencing we discovered that homozygous mutations in the AFG3L2 gene caused spastic ataxia in two brothers of a consanguineous family. AFG3L2 encodes a subunit of mitochondrial matrix proteases (m-AAA proteases) that regulate the functional integrity of mitochondria. Heterozygous mutations in AFG3L2 were previously found to cause a disorder involving the Purkinje cells of the cerebellum resulting in ataxia. Interestingly, another isoform of m-AAA proteases consists of AFG3L2 complexing with paraplegin, a similar protein associated with a hereditary spastic paraplegia. Our analysis provides insight into why different mutations in m-AAA protease subunits cause different neurological disorders.
doi:10.1371/journal.pgen.1002325
PMCID: PMC3192828  PMID: 22022284
23.  Zellweger Spectrum Disorder with Mild Phenotype Caused by PEX2 Gene Mutations 
JIMD Reports  2012;6:43-46.
The Zellweger spectrum disorders (ZSDs) are known to be severe disorders with onset in the newborn period or later in childhood, frequently resulting in death during childhood or adolescence. Here, we report a case of ZSD due to mutations in the PEX2 gene, with very mild phenotype. A 51-year-old Italian man was referred to us because of a clinical picture characterized by ataxia, areflexia, nystagmus, and strabismus, with childhood onset and slowly progressive course. The patient showed no cognitive impairment. Neurological examination revealed gait ataxia, dysarthria, dysmetria, areflexia, and bilateral pes cavus. Nerve conduction studies indicated a severe axonal sensorimotor polyneuropathy. Brain MRI showed marked cerebellar atrophy and absence of white matter involvement. MR spectroscopy uncovered a decreased N-acetyl aspartate peak. Biochemical analyses suggested a mild peroxisomal defect. Sequence analysis of the PEX2 gene identified two heterozygous mutations. The clinical phenotype of our patient differs from previously reported ZSD patients with PEX2 gene mutations and suggests that genetic screening of PEX2 is warranted in children and adults with otherwise unexplained autosomal recessive ataxia. MRI findings diverged from the “classic” spectrum observed in ZSDs. The moderate impairment in peroxisome biogenesis seems to affect predominantly neuronal cells in cerebellum, leading to cerebellar atrophy.
doi:10.1007/8904_2011_102
PMCID: PMC3565677  PMID: 23430938
24.  ‘Costa da Morte’ ataxia is spinocerebellar ataxia 36: clinical and genetic characterization 
Brain  2012;135(5):1423-1435.
Spinocerebellar ataxia 36 has been recently described in Japanese families as a new type of spinocerebellar ataxia with motor neuron signs. It is caused by a GGCCTG repeat expansion in intron 1 of NOP56. Family interview and document research allowed us to reconstruct two extensive, multigenerational kindreds stemming from the same village (Costa da Morte in Galicia, Spain), in the 17th century. We found the presence of the spinocerebellar ataxia 36 mutation co-segregating with disease in these families in whom we had previously identified an ∼0.8 Mb linkage region to chromosome 20 p. Subsequent screening revealed the NOP56 expansion in eight additional Galician ataxia kindreds. While normal alleles contain 5–14 hexanucleotide repeats, expanded alleles range from ∼650 to 2500 repeats, within a shared haplotype. Further expansion of repeat size was frequent, especially upon paternal transmission, while instances of allele contraction were observed in maternal transmissions. We found a total of 63 individuals carrying the mutation, 44 of whom were confirmed to be clinically affected; over 400 people are at risk. We describe here the detailed clinical picture, consisting of a late-onset, slowly progressive cerebellar syndrome with variable eye movement abnormalities and sensorineural hearing loss. There were signs of denervation in the tongue, as well as mild pyramidal signs, but otherwise no signs of classical amyotrophic lateral sclerosis. Magnetic resonance imaging findings were consistent with the clinical course, showing atrophy of the cerebellar vermis in initial stages, later evolving to a pattern of olivo-ponto-cerebellar atrophy. We estimated the origin of the founder mutation in Galicia to have occurred ∼1275 years ago. Out of 160 Galician families with spinocerebellar ataxia, 10 (6.3%) were found to have spinocerebellar ataxia 36, while 15 (9.4%) showed other of the routinely tested dominant spinocerebellar ataxia types. Spinocerebellar ataxia 36 is thus, so far, the most frequent dominant spinocerebellar ataxia in this region, which may have implications for American countries associated with traditional Spanish emigration.
doi:10.1093/brain/aws069
PMCID: PMC3338928  PMID: 22492559
spinocerebellar ataxia; NOP56; expansion mutation; founder effect; Galicia
25.  Xeroderma Pigmentosum/De Sanctis-Cacchione Syndrome: Unusual Cause of Ataxia 
Case Reports in Neurology  2014;6(1):83-87.
Introduction
Xeroderma pigmentosum (XP) is a rare autosomal recessive disorder of DNA repair, with a prevalence of 1 in 1 million. It may also be a cause of neurological symptoms including sensorineural hearing loss, peripheral neuropathy, ataxia, and chorea. Severe neurological symptoms including mental retardation, short stature, and hypogonadism invoke De Sanctis-Cacchione syndrome (DCS).
Case Report
The patient was a 55-year-old woman with a history of mental retardation who developed chorea at age 32 and ataxia at age 37. She had numerous facial scars from 10 prior basal cell carcinoma excisions as well as diminished deep tendon reflexes, bilateral hearing loss, dysphagia, and skin freckling. Brain MRI revealed severe cortical, cerebellar, and brainstem atrophy. Supportive treatment and prevention of further damage from UV light is the mainstay of treatment in XP and DCS.
Conclusion
XP and related disorders should be considered in the setting of neurological disorder and multiple cutaneous cancers.
doi:10.1159/000362115
PMCID: PMC4000305  PMID: 24803908
Xeroderma pigmentosum; De Sanctis-Cacchione syndrome; Cutaneous cancer; Mental retardation

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