LAUSR

The causal relationship has been well established between anti-GQ1b antibody and Fisher syndrome (FS), Guillain–Barre syndrome with ophthalmoplegia, acute ophthalmoparesis without ataxia, ataxia without ophthalmoplegia, and Bickerstaff brainstem encephalitis [1–3]. However, nystagmus or abnormal eye movements are also found in more than half of those with anti-GQ1b antibody-associated diseases that cannot be classified to one of the above disorders [4]. Occasional observation of abnormal head-impulse tests (HITs) [5] and caloric paresis [6–8] in patients with anti-ganglioside antibodies suggests a peripheral vestibular involvement in the disorders associated with anti-ganglioside antibodies. We report positive anti-GQ1b and antiGD1b antibodies in a patient with typical features of acute unilateral peripheral vestibulopathy. A 45-year-old woman presented spontaneous vertigo for a day. She had suffered from cough and myalgia for a week before the presentation. Examination showed spontaneous nystagmus beating rightward, upward and clockwise (from the patient’s perspective, Fig. 1a). The nystagmus increased during rightward gaze, and decreased during leftward gaze. HITs were positive for left anterior and horizontal canals (Fig. 1b). Bithermal caloric tests showed left canal paresis of 93% (Fig. 1c). She showed decreased ocular vestibular-evoked myogenic potentials (VEMPs) during left ear stimulation with an interaural difference at 41.7% (normal range < 21.5%). Cervical VEMPs and pure-tone audiometry were normal. Brain MRIs and MR angiography were also normal. Anti-GQ1b IgG (% ratio = 72%, normal range < 50%) and anti-GD1b IgG (% ratio > 100%, normal range < 50%) antibodies were positive, while anti-GM1 antibodies were negative (GanglioCombi ELISA, BÜHLMANN Laboratories, Switzerland). The patient was arranged for oral methylprednisolone 60 mg per day for a week, and was discharged with improvement of the vertigo 5 days later. Follow-up video-oculography 1 month later showed resolution of spontaneous nystagmus, canal paresis, and HITs along with negative conversion of serum anti-GQ1b and anti-GD1b antibodies. Our patient with anti-ganglioside antibodies presented the features of acute unilateral peripheral vestibulopathy mimicking vestibular neuritis (VN). Previously, the authors reported nystagmus and ataxia in isolation in patients with anti-GQ1b and anti-GD1b antibodies [9]. Given the nature of the nystagmus, i.e., periodic alternating nystagmus or central positional nystagmus, nystagmus in patients with antiganglioside antibodies have been ascribed to dysfunction of caudal brainstem or vestibulocerebellum [10, 11]. Indeed, anti-GQ1b or anti-GD1b antibodies have been found to bind with the cerebellar granular and molecular layers, and the dentate, vestibular and olivary nuclei in humans or rats [12]. In our patient, positive HITs only for ipsilesional horizontal and anterior canals and absence of gaze-evoked nystagmus indicate involvement of the vestibular pathway distal to the vestibular nucleus [13]. Indeed, the vestibular nerve may be preferentially involved in FS [6]. The higher expression of GQ1b ganglioside in the vestibular nerve also suggests vulnerability of the vestibular nerve in anti-GQ1b antibody syndrome [14]. Even though this report on a single patient does not provide strong evidence, the causal relationship between anti-ganglioside antibodies and acute unilateral peripheral vestibulopathy may be inferred by the nearly complete absence of anti-GQ1b and anti-GD1b serum antibodies * Ji-Soo Kim [email protected]