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1.  The video head impulse test 
Neurology  2009;73(14):1134-1141.
Background:
The head impulse test (HIT) is a useful bedside test to identify peripheral vestibular deficits. However, such a deficit of the vestibulo-ocular reflex (VOR) may not be diagnosed because corrective saccades cannot always be detected by simple observation. The scleral search coil technique is the gold standard for HIT measurements, but it is not practical for routine testing or for acute patients, because they are required to wear an uncomfortable contact lens.
Objective:
To develop an easy-to-use video HIT system (vHIT) as a clinical tool for identifying peripheral vestibular deficits. To validate the diagnostic accuracy of vHIT by simultaneous measures with video and search coil recordings across healthy subjects and patients with a wide range of previously identified peripheral vestibular deficits.
Methods:
Horizontal HIT was recorded simultaneously with vHIT (250 Hz) and search coils (1,000 Hz) in 8 normal subjects, 6 patients with vestibular neuritis, 1 patient after unilateral intratympanic gentamicin, and 1 patient with bilateral gentamicin vestibulotoxicity.
Results:
Simultaneous video and search coil recordings of eye movements were closely comparable (average concordance correlation coefficient rc = 0.930). Mean VOR gains measured with search coils and video were not significantly different in normal (p = 0.107) and patients (p = 0.073). With these groups, the sensitivity and specificity of both the reference and index test were 1.0 (95% confidence interval 0.69–1.0). vHIT measures detected both overt and covert saccades as accurately as coils.
Conclusions:
The video head impulse test is equivalent to search coils in identifying peripheral vestibular deficits but easier to use in clinics, even in patients with acute vestibular neuritis.
GLOSSARY
= bilateral vestibular loss;
= head impulse test;
= inertial measurement unit;
= intratympanic gentamicin;
= video head impulse test;
= vestibular neuritis;
= vestibulo-ocular reflex.
doi:10.1212/WNL.0b013e3181bacf85
PMCID: PMC2890997  PMID: 19805730
2.  Sensory neuropathy as part of the cerebellar ataxia neuropathy vestibular areflexia syndrome 
Neurology  2011;76(22):1903-1910.
Objective:
The syndrome of cerebellar ataxia with bilateral vestibulopathy was delineated in 2004. Sensory neuropathy was mentioned in 3 of the 4 patients described. We aimed to characterize and estimate the frequency of neuropathy in this condition, and determine its typical MRI features.
Methods:
Retrospective review of 18 subjects (including 4 from the original description) who met the criteria for bilateral vestibulopathy with cerebellar ataxia.
Results:
The reported age at onset range was 39–71 years, and symptom duration was 3–38 years. The syndrome was identified in one sibling pair, suggesting that this may be a late-onset recessive disorder, although the other 16 cases were apparently sporadic. All 18 had sensory neuropathy with absent sensory nerve action potentials, although this was not apparent clinically in 2, and the presence of neuropathy was not a selection criterion. In 5, the loss of pinprick sensation was virtually global, mimicking a neuronopathy. However, findings in the other 11 with clinically manifest neuropathy suggested a length-dependent neuropathy. MRI scans showed cerebellar atrophy in 16, involving anterior and dorsal vermis, and hemispheric crus I, while 2 were normal. The inferior vermis and brainstem were spared.
Conclusions:
Sensory neuropathy is an integral component of this syndrome. It may result in severe sensory loss, which contributes significantly to the disability. The MRI changes are nonspecific, but, coupled with loss of sensory nerve action potentials, may aid diagnosis. We propose a new name for the condition: cerebellar ataxia with neuropathy and bilateral vestibular areflexia syndrome (CANVAS). Neurology® 2011;76:1903–1910
doi:10.1212/WNL.0b013e31821d746e
PMCID: PMC3115806  PMID: 21624989
3.  Bilateral total deafness due to pontine haematoma. 
A 64 year old woman with a predominantly midline pontine tegmental haemorrhage presented with bilateral total deafness. One week later reasonable pure-tone thresholds appeared but she still had total bilateral loss of speech discrimination. At that time contralateral acoustic reflexes were bilaterally absent, whereas ipsilateral acoustic reflexes and waves IV and V of the brainstem auditory evoked potential were bilaterally preserved. It is proposed that this patient's hearing deficit was due to inactivation of the ventral acoustic striae decussating in the trapezoid body. This case supports the contention that in humans the ventral pontine acoustic decussation carries most of the neural signals required for hearing and perhaps all the neural signals required for speech perception.
Images
PMCID: PMC486661  PMID: 8971114
4.  Myogenic potentials generated by a click-evoked vestibulocollic reflex. 
Electromyograms (EMGs) were recorded from surface electrodes over the sternomastoid muscles and averaged in response to brief (0.1 ms) clicks played through headphones. In normal subjects, clicks 85 to 100 dB above our reference (45 dB SPL: close to perceptual threshold for normal subjects for such clicks) evoked reproducible changes in the averaged EMG beginning at a mean latency of 8.2 ms. The earliest potential change, a biphasic positive-negativity (p13-n23), occurred in all subjects and the response recorded from over the muscle on each side was predominantly generated by afferents originating from the ipsilateral ear. Later potentials (n34, p44), present in most but not all subjects, were generated bilaterally after unilateral ear stimulation. The amplitude of the averaged responses increased in direct proportion to the mean level of tonic muscle activation during the recording period. The p13-n23 response was abolished in patients who had undergone selective section of the vestibular nerve but was preserved in subjects with severe sensorineural hearing loss. It is proposed that the p13-n23 response is generated by activation of vestibular afferents, possibly those arising from the saccule, and transmitted via a rapidly conducting oligosynaptic pathway to anterior neck muscles. Conversely, the n34 and p44 potentials do not depend on the integrity of the vestibular nerve and probably originate from cochlear afferents.
PMCID: PMC1072448  PMID: 8126503
5.  The relationship between head and eye movement in congenital nystagmus with head shaking: objective recordings of a single case. 
Head shaking and congenital nystagmus were recorded in a patient presented with visual tasks. When she was at rest the nystagmus took a 6 cycles per second saw-tooth wave-form. When she was attentive the nystagmus beat at a 2 to 2.6 cycles per second with a saddle-shaped deformation which permitted foveation. The head shaking occurred occasionally when the patient was attentive and was phase-locked to the nystagmus with resemblances in wave form and direction. Deceleration of the head shaking to zero velocity and peak displacement (to the left) coincided with the onset of the saddle of the nystagmus and hence assisted foveation; all other parts of the head-shaking cycle were detrimental to vision. It is proposed that the head shaking has a common pathological origin with the nystagmus and that, just as an isolated congenital nystagmus wave form becomes altered with attention to permit periods of foveal fixation, the pattern of combined head and eye nodding in this patient provided similar peroids of fixation.
PMCID: PMC1043279  PMID: 687550
6.  Tremor, the cogwheel phenomenon and clonus in Parkinson's disease. 
Resting and postural tremor, intention and action tremor, clonus and the cogwheel phenomenon in Parkinson's disease have been characterised in terms of frequency content using spectral analysis. Typical resting tremor ranged in peak frequency from 4 to 5.3 HZ with tremor in each individual varying only by 0.2 to 0.3 HZ. The peak frequency of postural tremor ranged between 6 and 6.2 HZ. Intention tremor appeared to be an exaggeration of postural tremor. Clonus evoked by active or passive stretch at the wrist had a frequency of 6 HZ and appeared to be a continuation of postural tremor. The cogwheel phenomenon was found at frequencies between 6 and 6.5 HZ and between 7.5 to 9 HZ. Action tremor was indistinguishable from the cogwheel phenomenon. Some patients had either a symptomatic resting tremor with a concurrent 6 HZ component of smaller amplitude or a symptomatic postural tremor with a 4-5 HZ component of smaller amplitude. These combinations would produce two peaks in the power spectrum. When this occurred EMG studies showed that individual muscles had two types of rhythmical activation suggesting that the tremors have separate mechanisms. Likewise some patients had a symptomatic 6 HZ tremor on posture with a second peak at 8-10 HZ in the physiological band. Therefore, the 6 HZ postural tremor is not an exaggeration of physiological tremor. On the basis of wave form and frequency similarities postural tremor, the low frequency type of active or passive cogwheeling, intention tremor and clonus possibly involve a common spinal mechanism. Higher frequency cogwheel phenomenon and action tremor may be an exaggeration of physiological tremor. More than 80% of patients with Parkinson's disease manifest tremors at both 4-5 HZ and 6 HZ. This combination would appear to be the strongest objective criterion for the diagnosis of basal ganglia disease.
PMCID: PMC491035  PMID: 7276968
7.  Clinical signs of visual-vestibular interaction. 
Visual suppression of vestibulo-ocular reflexes (induced vestibular nystagmus) differs between normal subjects and patients with various neurological disorders. Abnormalities of VOR suppression were associated consistently with abnormalities of the visual and/or vesitibular oculomotor reflexes and in particular with abnormal smooth pursuit eye movements in the direction of abnormal suppression. Absent VOR suppression in a gaze position of, and in the same direction as, a spontaneous nystagmus was found exclusively in patients with spontaneous nystagmus of central nervous system origin. Conversely, ability to suppress in these circumstances was found only in patients with spontaneous nystagmus of peripheral labyrinthine origin. Suppression of VOR was abnormal ipsilaterally in patients with unilateral cerebral hemisphere lesions and abnormal in both the horizontal and vertical planes in patients with basal ganglia lesions. Failure of VOR suppression in the absence of spontaneous nystagmus indicates a supratentorial lesion.
Images
PMCID: PMC490367  PMID: 315999
8.  Pseudotumour cerebri syndrome due to cryptococcal meningitis. 
Three cases are reported of the pseudotumour cerebri syndrome-that is, intracranial hypertension without mass lesion or enlarged ventricles, due to cryptococcal meningitis. In these patients the papilloedema was successfully treated with optic nerve sheath decompression, and the intracranial hypertension with lumboperitoneal CSF shunting. These cases support the concept that pseudotumour cerebri is a syndrome of intracranial hypertension that can be due to any disorder producing obstruction of the CSF pathways at the level of the arachnoid villi. This concept is important because it directs therapy to normalise the intracranial pressure and preserve vision.
Images
PMCID: PMC486704  PMID: 9010409
9.  Secondary cluster headache responsive to sumatriptan. 
A patient was seen with secondary cluster headache whose acute pain responded promptly to sumatriptan. The headaches started after injury to the vertebral artery. This finding provides clinical affirmation of the existence of the trigeminal/cervical nuclear overlap that is central to this condition.
PMCID: PMC1073762  PMID: 7500105
10.  Eye blink reflexes to sudden free falls: a clinical test of otolith function. 
Conventional neuro-otological tests measure only semi-circular canal function and not otolith function. A clinically acceptable test of otolith function was developed. Previous studies suggested that muscle responses which occur less than 100 ms after release into free-fall are part of a startle reflex originating in the otoliths. With a couch capable of producing sudden, safe, comfortable free-falls it was shown that in normal subjects orbicularis oculi muscle responses (that is eyeblinks) invariably began within 45 ms of this stimulus and confirmed that these eyeblink reflexes are part of a generalised startle reflex, as they cross-habituate with eyeblink reflexes elicited by supraorbital nerve stimulation. Eyeblink reflexes to free-fall may prove a useful clinical test of otolith function.
PMCID: PMC1027568  PMID: 6619892
11.  Abnormal head movements. 
Abnormal head movements have been studied in a variety of diseases using objective recording techniques and the data analysed with respect to the frequency content of the movement. Flopping, nodding, tic, chorea, myoclonic jerks, and most head tremors involve frequencies of approximately 2 and 4 Hz which correspond to the natural fundamental and second harmonic resonances of the head as determined by the mechanical properties of the head/neck system. These findings provide a basis for classification of abnormal head movements as well as an explanation of the characteristics of those arising from hypotonia of the neck muscles. The similarities between tremor frequencies and natural resonances suggest that in the case of the head, tremor arises from disorders of neural mechanisms normally responsible for the fine control of voluntary head movement and for stabilisation of the head during disturbance of posture. Head movements in cases of congenital nystagmus were found to be of two types. Some were of bizarre waveform, in no way assisted vision, and were taken to be of primarily pathological origin and classified as tremors. Others were learned adaptive responses which assisted vision either by interrupting the nystagmus, as in the case of spasmus nutans, or by compensating for the nystagmus with an inverse waveform and were called nodding. A prerequisite for true compensatory nodding is modified vestibulo-ocular reflex.
PMCID: PMC490303  PMID: 490176

Results 1-11 (11)