Test Your Knowledge - The Acute Vestibular Syndrome and Ptosis

What is the most likely localization in this patient presenting with vertical diplopia and acute onset prolonged vertigo? A. Right medial longitudinal fasciculus (MLF) B. Left medial longitudinal fasciculus C. Right medulla D. Left medulla E. Left midbrain A. Incorrect. A right MLF lesion (stroke, MS, other) may cause vertical-torsional spontaneous nystagmus, but the torsional component of the nystagmus will be ipsiversive - i.e., the top poles will beat toward the right ear. B. Incorrect. A left MLF lesion may cause spontaneous vertical-torsional nystagmus with ipsiversive torsional fast phases (top poles toward the left ear) as in this case, but a left internuclear ophthalmoplegia (INO) would be expected as well. Furthermore, mild ptosis from oculosympathetic tract injury would be unlikely with an MLF localization. If the MLF lesion is particularly rostral, the patient may have a partial 3rd nerve palsy as well, but there were no motility deficits or a mydriatic pupil OD in her case. Instead, there was a miotic pupil OD (not well seen in the video). C. Correct. This patient suffered a right lateral medullary stroke causing the acute vestibular syndrome (acute onset prolonged vertigo, spontaneous nystagmus, unsteadiness, head motion intolerance, nausea), and on exam had a skew deviation (responsible for right hypotropia and vertical diplopia), right Horner's syndrome (right ptosis and miosis), and spontaneous nystagmus with left and up-beating components, in addition to a prominent torsional nystagmus with top poles beating toward the left ear. This pattern of spontaneous nystagmus is incompatible with an acute right peripheral vestibulopathy such as vestibular neuritis. D. Incorrect. A left (lateral) medullary localization might cause a left Horner's syndrome (the oculosympathetic tract is uncrossed) and/or a left hypotropia due to a skew deviation - i.e., both opposite to what is seen in the video. E. Incorrect. A left midbrain lesion could cause a right 4th nerve palsy (the 4th nerve exits the midbrain dorsally and then decussates so that a contralesional 4th nerve palsy can be seen with unilateral caudal midbrain injury), manifest as a right hypertropia as opposed to a right hypotropia (seen in the video). Since the anterior semicircular canal afferents travel through the brachium conjunctivum (aka, superior cerebellar peduncle) in addition to the medial longitudinal fasciculus and ventral tegmental tract, a midbrain lesion can cause a ‘central' (nucleus or fascicle) 4th nerve palsy and spontaneous upbeat-torsional nystagmus (1). Since the horizontal semicircular canal afferents have already synapsed at the 6th nuclei in the pons, there shouldn't be a significant horizontal component to the spontaneous nystagmus. Summary: This patient suffered a right vertebral artery dissection causing a right lateral medullary stroke and the acute vestibular syndrome with ocular motor signs including: skew deviation (right hypotropia); spontaneous left-beating, up-beating, and torsional (top poles toward left ear) nystagmus; ipsipulsion (deviation of eyes to the right - toward the side of the stroke - under closed eyelids) with hypermetric saccades to the right and hypometric saccades to the left (saccadic dysmetria not seen in the video); and a right Horner's syndrome (right upper and lower lid ptosis and miosis). 1. Makki AA, Newman NJ. A trochlear stroke. Neurology 2005;65:1989.