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1.  Do brainstem omnipause neurons terminate saccades? 
Saccade-generating burst neurons (BN) are inhibited by omnipause neurons (OPN), except during saccades. OPN activity pauses before saccade onset and resumes at the saccade end. Microstimulation of OPN stops saccades in mid-flight, which shows that OPN can end saccades. However, OPN pause duration does not correlate well with saccade duration, and saccades are normometric after OPN lesions. We tested whether OPN were responsible for stopping saccades both in late-onset Tay–Sachs, which causes premature saccadic termination, and in individuals with cerebellar hypermetria. We studied gaze shifts between two targets at different distances aligned on one eye, which consist of a disjunctive saccade followed by vergence. High-frequency conjugate oscillations during the vergence movements that followed saccades were present in all subjects studied, indicating OPN silence. Thus, mechanisms other than OPN discharge (e.g., cerebellar caudal fastigial nucleus–promoting inhibitory BN discharge) must contribute to saccade termination.
PMCID: PMC3438674  PMID: 21950975
Tay–Sachs disease; saccades; omnipause neurons; fastigial nucleus; Müller paradigm
2.  Pain in Ischemic Ocular Motor Cranial Nerve Palsies 
The British journal of ophthalmology  2009;93(12):1657-1659.
Pain is a common feature of microvascular ischemic ocular motor cranial nerve palsies (MP). The natural history of pain in this condition has not been studied. The purpose of this report is to define the spectrum of pain in isolated MP, with special reference to diabetics versus nondiabetics.
Design and methods
Retrospective and prospective chart review was performed on 87 patients with acute onset MP of a single cranial nerve (CN III = oculomotor, CN IV = trochlear, or CN VI = abducens) that progressively improved or resolved over 6 months.
Five of the 87 patients had two events, making the total number events 92. There were 48 (52.2%) CN VI palsies, 39 (42.4%) CN III palsies, and 5 (5.4%) CN IV palsies. Thirty-six (41%) patients had diabetes. Pain was present in 57 (62%) events. The majority of diabetics and non-diabetics had pain. Pain preceded diplopia by 5.8 days (± 5.5) in one third of events. There was a trend towards greater pain with CN III palsies but this was not statistically significant. Patients who experienced severe pain tended to have pain for a longer duration of time (26.4 ± 21.7 days compared to 10.8 ± 8.3 and 9.5 ± 9 days for mild and moderate pain, respectively). There was no correlation between having diabetes and experiencing pain.
The majority of MP are painful, regardless of the presence or absence of diabetes. Pain may occur prior to or concurrent with the onset of diplopia. Nondiabetics and diabetics presented with similar pain characteristics, contrary to the belief that diabetics have more pain associated with MP.
PMCID: PMC2998753  PMID: 19570771
Microvascular; cranial nerve; pain
3.  Mirror Movements Identified in Patients with Moebius Syndrome 
Moebius syndrome is a rare disorder with minimum clinical criteria of congenital facial weakness in association with impairment in abduction of one or both eyes. Mirror movements are not known to be associated with Moebius syndrome.
Case Report
We present three patients who meet minimum criteria for a diagnosis of Moebius syndrome and who also display mirror movements.
This case series suggests that Moebius syndrome may be associated with mirror movements. Further investigation to delineate the genetic etiologies of Moebius syndrome is ongoing. Patients with Moebius syndrome and mirror movements may represent a specific subclass of this disorder.
PMCID: PMC4107286  PMID: 25120946
Mirror movements; Moebius syndrome
4.  Progressive Supranuclear Palsy-Like Syndrome After Aortic Aneurysm Repair: A Case Series 
Tremor and Other Hyperkinetic Movements  2013;3:tre-03-201-4686-1.
The syndrome of progressive supranuclear palsy-like syndrome is a rare complication of ascending aortic aneurysm repair. We report two patients with videos and present a table of prior reported cases. To our knowledge there is no previously published video of this syndrome. The suspected mechanism is brainstem injury though neuroimaging is often negative for an associated infarct. We hope our report will increase recognition of this syndrome after aortic surgery, especially in patients with visual complaints.
PMCID: PMC3859893  PMID: 24386607
Progressive supranuclear palsy; supranuclear gaze palsy; aortic aneurysm repair
5.  Atypical Chédiak-Higashi syndrome with attenuated phenotype: three adult siblings homozygous for a novel LYST deletion and with neurodegenerative disease 
Mutations in LYST, a gene encoding a putative lysosomal trafficking protein, cause Chédiak-Higashi syndrome (CHS), an autosomal recessive disorder typically characterized by infantile-onset hemophagocytic syndrome and immunodeficiency, and oculocutaneous albinism. A small number of reports of rare, attenuated forms of CHS exist, with affected individuals exhibiting progressive neurodegenerative disease beginning in early adulthood with cognitive decline, parkinsonism, features of spinocerebellar degeneration, and peripheral neuropathy, as well as subtle pigmentary abnormalities and subclinical or absent immune dysfunction.
In a consanguineous Pakistani kindred with clinical phenotypes consistent with attenuated CHS, we performed SNP array-based homozygosity mapping and whole gene sequencing of LYST.
We identified three individuals homozygous for a novel six base pair in-frame deletion in LYST (c.9827_9832ATACAA), predicting the loss of asparagine and threonine residues from the LYST transcript (p.Asn3276_Thr3277del), and segregating with the phenotype in this family.
We further characterize the neurologic features of the attenuated form of CHS, and discuss pathophysiologic mechanisms underlying the neurodegenerative components of CHS. Attenuated CHS is phenotypically heterogenous and should be considered when young adults develop neurodegenerative disease and have pigmentary abnormalities. We briefly discuss surveillance and management of patients with CHS-related neurodegeneration.
PMCID: PMC3610301  PMID: 23521865
Chédiak-Higashi syndrome; LYST; Lysosomal; Amyloid; Oxidative stress; Parkinsonism; Neurodegenerative disease
6.  Ocular motor anatomy in a case of interrupted saccades 
Progress in brain research  2008;171:563-566.
Saccades normally place the eye on target with one smooth movement. In late-onset Tay—Sachs (LOTS), intrasaccadic transient decelerations occur that may result from (1) premature omnipause neuron (OPN) re-activation due to malfunction of the latch circuit that inhibits OPNs for the duration of the saccade or (2) premature inhibitory burst neuron (IBN) activation due to fastigial nucleus (FN) dysregulation by the dorsal cerebellar vermis. Neuroanatomic analysis of a LOTS brain was performed. Purkinje cells were absent and gliosis of the granular cell layer was present in the dorsal cerebellar vermis. Deep cerebellar nuclei contained large inclusions. IBNs were present with small inclusions. The sample did not contain the complete OPN region; however, neurons in the OPN region contained massive inclusions. Pathologic findings suggest that premature OPN re-activation and/or inappropriate firing of IBNs may be responsible for interrupted saccades in LOTS. Cerebellar clinical dysfunction, lack of saccadic slowing, and significant loss of cerebellar cells suggest that the second cause is more likely.
PMCID: PMC2752380  PMID: 18718354
fastigial nucleus; omnipause neurons; burst neurons; latch circuit; brainstem
7.  Mechanism of interrupted saccades in patients with late-onset Tay-Sachs disease 
Progress in brain research  2008;171:567-570.
In late-onset Tay-Sachs disease (LOTS), saccades are interrupted by one or more transient decelerations. Some saccades reaccelerate and continue on before eye velocity reaches zero, even in darkness. Intervals between successive decelerations are not regularly spaced. Peak decelerations of horizontal and vertical components of oblique saccades in LOTS is more synchronous than those in control subjects. We hypothesize that these decelerations are caused by dysregulation of the fastigial nuclei (FN) of the cerebellum, which fire brain stem inhibitory burst neurons (IBNs).
PMCID: PMC2750844  PMID: 18718355
fastigial nucleus; omnipause neurons; burst neurons; latch circuit
8.  Contrast Sensitivity, First-Order Motion and Initial Ocular Following in Demyelinating Optic Neuropathy 
Journal of neurology  2006;253(9):1203-1209.
The ocular following response (OFR) is a measure of motion vision elicited at ultra-short latencies by sudden movement of a large visual stimulus. We compared the OFR to vertical sinusoidal gratings (spatial frequency 0.153 cycles/° or 0.458 cycles/°) of each eye in a subject with evidence of left optic nerve demyelination due to multiple sclerosis (MS). The subject showed substantial differences in vision measured with stationary low-contrast Sloan letters (20/63 OD and 20/200 OS at 2.5% contrast) and the Lanthony Desaturated 15-hue color test (Color Confusion Index 1.11 OD and 2.14 OS). Compared with controls, all of the subject's OFR to increasing contrast showed a higher threshold. The OFR of each of the subject's eyes were similar for the 0.153 cycles/° stimulus, and psychophysical measurements of his ability to detect these moving gratings were also similar for each eye. However, with the 0.458 cycles/° stimulus, the subject's OFR was asymmetric and the affected eye showed decreased responses (smaller slope constant as estimated by the Naka-Rushton equation). These results suggest that, in this case, optic neuritis caused a selective deficit that affected parvocellular pathways mediating higher spatial frequencies, lower-contrast, and color vision, but spared the field-holding mechanism underlying the OFR to lower spatial frequencies. The OFR may provide a useful method to study motion vision in individuals with disorders affecting anterior visual pathways.
PMCID: PMC2408647  PMID: 16649097
optic neuritis; multiple sclerosis; saccades; pursuit
9.  Motor neuronopathy with dropped hands and downbeat nystagmus: A distinctive disorder? A case report 
BMC Neurology  2006;6:3.
Eye movements are clinically normal in most patients with motor neuron disorders until late in the disease course. Rare patients are reported to show slow vertical saccades, impaired smooth pursuit, and gaze-evoked nystagmus. We report clinical and oculomotor findings in three patients with motor neuronopathy and downbeat nystagmus, a classic sign of vestibulocerebellar disease.
Case presentation
All patients had clinical and electrodiagnostic features of anterior horn cell disease. Involvement of finger and wrist extensors predominated, causing finger and wrist drop. Bulbar or respiratory dysfunction did not occur. All three had clinically evident downbeat nystagmus worse on lateral and downgaze, confirmed on eye movement recordings using the magnetic search coil technique in two patients. Additional oculomotor findings included alternating skew deviation and intermittent horizontal saccadic oscillations, in one patient each. One patient had mild cerebellar atrophy, while the other two had no cerebellar or brainstem abnormality on neuroimaging. The disorder is slowly progressive, with survival up to 30 years from the time of onset.
The combination of motor neuronopathy, characterized by early and prominent wrist and finger extensor weakness, and downbeat nystagmus with or without other cerebellar eye movement abnormalities may represent a novel motor neuron syndrome.
PMCID: PMC1351204  PMID: 16409626
10.  Neuro-ophthalmologic aspects of multiple sclerosis: Using eye movements as a clinical and experimental tool 
Ocular motor disorders are a well recognized feature of multiple sclerosis (MS). Clinical abnormalities of eye movements, early in the disease course, are associated with generalized disability, probably because the burden of disease in affected patients falls on the brainstem and cerebellar pathways, which are important for gait and balance. Measurement of eye movements, especially when used to detect internuclear ophthalmoplegia (INO), may aid diagnosis of MS. Measurement of the ocular following response to moving sinusoidal gratings of specified spatial frequency and contrast can be used as an experimental tool to better understand persistent visual complaints in patients who have suffered optic neuritis. Patients with MS who develop acquired pendular nystagmus often benefit from treatment with gabapentin or memantine.
PMCID: PMC2701138  PMID: 19668480
multiple sclerosis; eye movements; ocular motor disorders

Results 1-10 (10)