Faculty Bibliography

BACKGROUND: Contrast acuity (identification of low-contrast letters on a white background) is frequently reduced in patients with demyelinating optic neuropathy associated with multiple sclerosis (MS), even when high-contrast (Snellen) visual acuity is normal. Since visual evoked potentials (VEPs) induced with high-contrast pattern-reversal stimuli are typically increased in latency in demyelinating optic neuropathy, we asked if VEPs induced with low-contrast stimuli would be more prolonged and thus helpful in identifying demyelinating optic neuropathy in MS. METHODS: We studied 15 patients with clinically definite MS and 15 age-matched normal controls. All subjects underwent a neuro-ophthalmologic assessment, including measurement of high-contrast visual acuity and low-contrast acuities with 25%, 10%, 5%, 2.5%, and 1.25% contrast Sloan charts. In patients with MS, peripapillary retinal nerve fiber layer (RNFL) thickness was determined using optical coherence tomography. Monocular VEPs were induced using pattern-reversal checkerboard stimuli with 100% and 10% contrast between checks, at 5 spatial frequencies (8-130 minutes of arc). RESULTS: VEP latencies were significantly increased in response to low- compared with high-contrast stimuli in both groups. VEP latencies were significantly greater in patients with MS than controls for both high- and low-contrast stimuli. VEP latencies correlated with high- and low-contrast visual acuities and RNFL thickness. VEPs were less likely to be induced with low- than with high-contrast stimuli in eyes with severe residual visual loss. CONCLUSIONS: Visual evoked potentials obtained in patients with multiple sclerosis using low-contrast stimuli are increased in latency or absent when compared with those obtained using high-contrast stimuli and, thus, may prove to be helpful in identifying demyelinating optic neuropathy.

AIM: Pain is a common feature of microvascular ischaemic 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 diabetic versus non-diabetic patients. 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; CN VI, abducens) that progressively improved or resolved over 6 months. RESULTS: Five of the 87 patients had two events, making the total number events 92. There were 39 (42.4%) CN III palsies, five (5.4%) CN IV palsies and 48 (52.2%) CN VI palsies. Thirty-six (41%) patients had diabetes. Pain was present in 57 (62%) events. The majority of diabetic and non-diabetic patients had pain. Pain preceded diplopia by 5.8 (SD 5.5) days 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 (26.4 (SD 21.7) days compared with 10.8 (SD 8.3) and 9.5 (SD 9) days for mild and moderate pain, respectively). There was no correlation between having diabetes and experiencing pain. CONCLUSIONS: 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. Non-diabetic and diabetic patients presented with similar pain characteristics, contrary to the belief that diabetic patients have more pain associated with MP.

Many neuro-ophthalmologic conditions may result from systemic disease or its treatments. This article provides an update on optic neuropathies, eye movement disorders, and intracranial visual pathway lesions that occur most commonly with systemic disease, are clinical emergencies, or have been identified or clarified in recent publications.

A 70-year-old woman with a history of diabetes mellitus and arterial hypertension presented with bilateral abduction deficits consistent with bilateral sixth nerve paresis. A diagnostic evaluation including magnetic resonance imaging and lumbar puncture was unrevealing. The bilateral sixth nerve paresis spontaneously resolved suggesting ischemic or microvascular disease as the underlying etiology.

The Miller Fisher syndrome (MFS) is a variant of Guillain-Barre syndrome with the clinical triad of areflexia, ataxia, and ophthalmoparesis. The classic pathologic mechanism of disease is considered to be peripheral nerve demyelination. We present a patient with binocular diplopia and a diagnosis of myasthenia gravis from 15 years prior. Electrophysiologic studies revealed a decremental response on repetitive nerve stimulation, suggesting recurrent myasthenia. However, pupillary light-near dissociation and areflexia were present and positive anti-GQ1b antibodies confirmed MFS. This patient highlights a developing recognition of impaired neuromuscular transmission in MFS. His presentation is discussed in the context of the animal and human literature on neuromuscular junction abnormalities in MFS.