Emergencies in Neuro-Ophthalmology: A Case Based Approach

can cause SNP in patients with signs of subarachnoid hemorrhage, papilledema, or other cranial neuropathies.

Dr. Lee. The traditional teaching is that an isolated SNP in a vasculopath that is resolving or has resolved does not need neuroimaging or other evaluation besides treatment of the vasculopathic risk factors. Some authors, given the low risk of MRI, disagree however with this “traditional” teaching. In several papers, a low but not zero rate of treatable etiologies (e.g. meningioma, brainstem ischemia, demyelinating disease) have been discovered through imaging at onset. Although I recognize the results of these studies, I personally still hold to the traditional approach as the most cost-effective means of evaluating isolated acute and presumed vasculopathic palsies. It has been my experience that vasculopathic patients with SNP who are also harboring an underlying nonischemic intracranial etiology either have non-neurologically isolated SNP or do not improve over the observational period and therefore will eventually undergo the appropriate imaging study. In these patients with meningiomas and other chronic lesions, the short delay in the diagnosis does not generally change management.

On the other hand, the chronic SNP is a well known “harbinger” of serious and potentially treatable intracranial disease. I image with cranial MRI with contrast and with constructive interference in steady state (CISS) sequences to follow the entire course of the sixth cranial nerve. Patients who worsen, do not improve, are not isolated, or who develop new neurologic signs and symptoms should undergo evaluation, including neuroimaging for alternative etiologies for the sixth nerve dysfunction.

REFERENCES

Galetta SL, Smith JL. (1989) Chronic isolated sixth nerve palsies. Arch Neurol 46:79–82.

Jacobson DM. (1996) Progressive ophthalmoplegia with acute ischemic abducens nerve palsies. Am J Ophthalmol 122:278–279.

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Acute Painless Isolated Sixth Nerve Palsy

Patel SV, Mutyala S, Leske DA, et al. (2004) Incidence, associations, and evaluation of sixth nerve palsy using a population-based method. Ophthalmology 111:369–375.

Savino PJ, Hilliker JK, Casell GH, et al. (1982) Chronic sixth nerve palsies: Are they really harbingers of serious intracranial disease? Arch Ophthalmol 100:1442–1444.

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