A dorsolateral medullary lesion causing persistent down-beating nystagmus

Abstract

A 59-year-old woman presented with a 3-year history of recurrent spontaneous disequilibrium lasting hours (worse lying down), throbbing occipital headaches with nausea, and non-pulsatile left-sided tinnitus, following a holiday in Africa. When assessed, the patient’s gait was normal with unsteady tandem walking, and a positive matted Romberg test. Limb examination was normal with no appendicular ataxia or long-tract signs. There was no spontaneous or post-headshaking nystagmus, but subtle persistent torsional nystagmus in the left Dix–Hallpike position. Her initial MRI brain was normal. The audiogram showed mild presbycusis with a left-sided hearing loss at 500 Hz. The head-impulse test was negative. A diagnosis of vestibular migraine (VM) was considered, and Prothiaden (25 mg) was prescribed. Nine months later, the patient returned with increasing positional dizziness and nausea. Spontaneous left-beating torsional nystagmus was observed in the primary position (with fixation denied), which was enhanced in the left Dix–Hallpike position, with an additional up-beating component. Audiometry remained unchanged, with normal caloric test. Saccades and visual pursuit were normal; however, vestibulo-ocular reflex (VOR) suppression was mildly reduced. Cervical vestibular-evoked myogenic potentials (VEMP) were absent from the left ear. Ocular VEMPs, caloric tests, video head-impulse test, and auditory brainstem responses were normal (Fig. 1a–d). Repeat MRI brain was normal. Left posterior-canal cupulolithiasis or VM causing central positional vertigo was considered. Multiple Epley manoeuvres in in left posterior-canal plane were undertaken on the Epley–Omniax rotator with no symptom resolution [1]. A diagnosis of central vertigo was considered; she trialled cinnarizine, flunarizine, pizotifen, topiramate, acetazolamide, and sodium valproate with no symptom relief. One year after initial presentation, she returned with oscillopsia, nausea, and imbalance. She now demonstrated primary position leftward torsional down-beating nystagmus, and down-beating nystagmus post-headshake (Supplementary file 1, Fig. 1e). Nystagmus remained unchanged in left and right gaze. Horizontal saccades were normal, pursuit was interrupted by nystagmus, and VOR suppression was reduced. There was no oculo-palatal tremor or palatal deviation. There was left finger-nose and heel–shin ataxia, and difficulty tandem walking. A 3 T MRI brain revealed a left dorsolateral medullary hypo-intensity on T1and T2-weighted imaging, and hyper-intense calcified lesion on CT, in keeping with a cavernoma (Fig. 1h, i). Whole-body PET CT showed numerous small nodes above and below the diaphragm, suggestive of well differentiated lymphoma or sarcoidosis; biopsy of an axillary node demonstrated reactive changes only. A lumbar puncture showed cerebrospinal fluid had a minor elevation of protein at 0.48; however, glucose, cell count, cytology, all infective serology (Strongyloides, Toxoplasmosis, and Borreliosis) and atypical serology were negative. Colonoscopy revealed two 15 mm pedunculated polyps in sigmoid, were excised, and found to be benign. Serial sinusoidal rotation tests showed progressive loss of vestibulo-ocular reflex (VOR) suppression (Fig. 1f). Serial subjective visual-horizontal testing over 5 years showed rightward bias on all but two tests, coupled with the absent cVEMP indicate a chronic otolith dysfunction (Fig. 1g). Progress MRI and whole-body PET scans remained unchanged. * Miriam S. Welgampola [email protected]