Faculty Bibliography

Opsoclonus consists of bursts of involuntary, multidirectional, back-to-back saccades without an intersaccadic interval. We report a 60-year-old man with post-concussive headaches and disequilibrium who had small amplitude opsoclonus in left gaze, along with larger amplitude flutter during convergence. Examination was otherwise normal and brain MRI was unremarkable. Video-oculography demonstrated opsoclonus predominantly in left gaze and during pursuit in the left hemifield, which improved as post-concussive symptoms improved. Existing theories of opsoclonus mechanisms do not account for this eye position-dependence. We discuss theoretical mechanisms of this behavior, including possible dysfunction of frontal eye field and/or cerebellar vermis neurons; review ocular oscillations in traumatic brain injury; and consider the potential relationship between the larger amplitude flutter upon convergence and post-traumatic ocular oscillations.

BACKGROUND:The optic nerve is a frequent site for involvement in multiple sclerosis (MS). Optical coherence tomography (OCT) detects thinning of the retinal nerve fiber layer (RNFL) in eyes of patients with MS and in those meeting criteria for clinically or radiologically isolated demyelinating syndromes. Current international diagnostic criteria for MS do not include the optic nerve as an imaging lesion site despite the high prevalence of acute optic neuritis (ON), or occult optic neuropathy, among early MS and clinically isolated syndrome patients; as well as most MS patients over the course of the disease. We sought to determine optimal thresholds for intereye difference in peripapillary RNFL thickness that are most predictive of a unilateral optic nerve lesion. METHODS:We analyzed spectral domain OCT data of 31 healthy volunteers and 124 patients with MS at a single center as part of an ongoing collaborative investigation of visual outcomes. Intereye differences in peripapillary (360°) RNFL thickness were calculated as the absolute value of the difference. First, we determined the 95th percentile value of intereye difference for the healthy volunteers. This value was applied to the convenience sample group of MS patients as a validation cohort determining how well this threshold could distinguish patients with vs without a history of unilateral ON. The relation of intereye differences in peripapillary RNFL thickness to binocular low-contrast letter acuity scores was also examined. RESULTS:Among healthy volunteer participants (n = 31), the 95th percentile value for intereye difference (upper boundary of expected for normal controls) was 6.0 μm. This value was applied to the convenience sample group of MS patients (n = 124, validation cohort). Positive predictive value, negative predictive value, sensitivity, and specificity for identifying MS patients with a history of unilateral ON were calculated for the 6-μm threshold value in a 2 × 2 table analysis with the application of χ tests (P < 0.0001). The 6-μm threshold was predictive of worse binocular low-contrast acuity scores at 2.5% (P = 0.03) and 1.25% (P = 0.002 by linear regression analyses). A receiver operating characteristic curve analysis demonstrated an optimal intereye difference threshold of 5 μm for identifying unilateral ON in the MS cohort. CONCLUSIONS:An intereye difference of 5-6 μm in RNFL thickness is a robust structural threshold for identifying the presence of a unilateral optic nerve lesion in MS.