+ HIT, + Skew, Unidirectional Nystagmus: Central Acute Vestibular Syndrome Due to Wallenberg Syndrome

This is a 45-year-old woman who presented to the ED with acute prolonged vertigo and vertical diplopia. She was seen as an outpatient 1 month after her ED visit, and double vision and balance were improving by that time. Her HINTS testing showed the following (seen in the video): 1) Head Impulse - Abnormal to the right; seen with peripheral>>central conditions; 2); Nystagmus - Unidirectional horizontal-torsional nystagmus, least in right gaze, most in left gaze (Alexander's law); usually seen with peripheral but can be seen with small unilateral central vestibular lesions; 3); Test of Skew - A 3 prism diopter left hypertropia was seen with cover-uncover testing, in addition to a slight head tilt to the right, and ocular counterroll (excyclodeviation OD and incyclodeviation OS) seen with ophthalmoscopy (skew + ocular counterroll + head tilt = ocular tilt reaction); seen with central>>peripheral conditions. Her 3 PD LH decreased to 1 PD LH when measurements were repeated with Maddox rod testing, which again is suggestive of a skew deviation - i.e., when supine, there is less utricle-ocular motor pathway asymmetry as the gravitational forces that act upon the utricles are lessened. Regardless of the "peripheral" appearance of the head impulse and nystagmus, the presence of a skew deviation makes this central until proven otherwise. That being said, a small, transient skew deviation can rarely be seen acutely with otherwise typical vestibular neuritis. MR angiogram of the head and neck and MR with diffusion weighted imaging done acutely in the ED (within hours of onset) was negative, although it is thought that up to 20% of small brainstem strokes can be missed by MR-DWI in the first 24 hours. In summary, this was either 1) a small brainstem lesion and imaging was done too soon for the lesion to be seen or 2) a rare instance of vestibular neuritis with a small skew deviation (i.e., the utricle fibers are affected within the peripheral vestibular nerve). However, her skew deviation persisted for much longer than what would be expected with a "peripheral" skew deviation (4 weeks in her case, whereas "peripheral" skews should resolve within days unless a severe, destructive utricle injury - as in bacterial labyrinthitis or vestibular nerve section - has occurred), and additionally, there was mild (ipsilesional) ocular lateropulsion to the right and hypometric (contralesional) saccades to the left, both of which are commonly seen with a right lateral medullary (Wallenberg) syndrome (ipsilesional hypermetric saccades can also be seen, but were not appreciated in her case). She was diagnosed with an MRI negative right medullary lesion, probably related to a stroke, and cardiac work-up to investigate a cardioembolic etiology was ordered.