A 39-year-old woman had sudden onset of severe left posterior neck pain, left face numbness, and left-sided incoordination. She veered to the left, vomited on numerous occasions, and had drooping of her left eyelid. Subsequently, she noted impaired heat perception on the right hemibody and dysesthesias of the right leg. She had no vertigo, diplopia, dysarthria, tinnitus, hearing loss, or hiccups. She had had no prior spinal manipulations or neck injuries.

Our patient had a classic history of a lateral medullary (Wallenberg) syndrome. She had a left vertebral artery dissection. In addition to her residual dysesthetic sensory symptomatology, she had a preganglionic left Horner syndrome due to involvement of the hypothalamospinal pathway at the dorsolateral brainstem tegmentum. A Horner syndrome results from underactivity of the oculosympathetic pathway and is characterized by miosis, partial eyelid ptosis, and at times facial anhidrosis. The anisocoria is more pronounced in darkness, a typical feature of Horner compared to other forms of anisocoria (Fig. 79.1). The affected pupil dilates more slowly than the normal pupil (dilation lag). Other neuro-ophthalmological manifestations of vertebrobasilar dissections include diplopia, nystagmus, oscillopsia, ocular misalignment, skew deviation, ocular motor nerve palsies (CN III, IV, and VI), lateral gaze palsy, internuclear ophthalmoplegia, and homonymous visual field defects.