A 51-year-old woman with PRS presented with an 8-year history of binocular horizontal diplopia on right lateral gaze exacerbated during exercise. Her diplopia on exertion would resolve shortly after cessation of exercise while cooling off. The patient denied eye pain, floaters, photopsia, decreased vision, paresthesias, or motor deficits of the extremities. The patient's history of PRS was characterized as progressive left-sided facial atrophy for a period of 10 years following infection with herpes zoster and postherpetic neuralgia in the distribution of the ophthalmic division (V1) of the trigeminal nerve. Examination showed atrophy involving the left temporal region and alopecia localized to the left frontal parietal region, corresponding with V1. There was minimal hyperpigmentation of skin over the left vivum dermatome and a linear hypopigmented scar (coup de sabre) was observed. On neurologic examination, speech was fluent without dysarthria or aphasia, and cognitive functions were intact. Tongue and uvula were midline. Motor examination showed normal tone, no evidence of drift, and 5/5 strength bilaterally. Coordination and gait were intact. Deep tendon reflexes were 2+ bilaterally and plantar responses were flexor. Sensory examination was normal and intact to light touch and pin prick testing. The patient's past medical history was significant for Hashimoto's thyroiditis, migraine headaches, and recurrent outbreaks of herpes simplex labialis. Medications included levothyroxine 50 mcg daily. Family history was significant solely for migraines in the patient's sister.
On ophthalmologic examination, best-corrected visual acuity was 20/20 in both eyes. Applanation tonometry measured intraocular pressures of 12 in both the right and the left eyes. Fundus examination was normal appearing without evidence of pallor or edema. Pupils were equal and reactive to light with no afferent pupillary defects. Color vision assessment on Ishihara plate testing showed 15/15 OD and 13/15 OS. Ocular motility examination was significant for 30-degree limited adduction of the left eye on right lateral gaze.
Autoimmune panel was positive for antinuclear antibody (ANA) (1:40 speckled pattern, normal range <1:40) and negative for beta 2 glycoprotein and cardiolipin immunoglobulins (IgA, IgG, and IgM). Vitamin B12 and Vitamin E levels were within normal limits. Magnetic resonance imaging (MRI) of the brain showed multiple white matter lesions including the left frontal lobe, left parieto-occipital area, and periventricular areas of the left frontal and left posterior horns of the lateral ventricles (Figures 1(a)-1(c)). In addition, FLAIR/T2 hyperintensity of the midbrain region corresponding to the area of the MLF was seen (Figure 1(d)). MRI of the orbits (Figure 2) showed normal positioning of the globes bilaterally without evidence of proptosis or extraocular muscle fibrosis or atrophy. MRI of the spinal cord showed no evidence of spinal lesions.
Given recurrent outbreaks of herpes simplex labialis, the patient was started on valacyclovir 500 mg PO BID. On follow-up 3 months later, the patient indicated that her heat-induced diplopia was completely resolved. Ocular motility examination was significantly improved with less than 10-degree limited adduction of the left eye on right lateral gaze.