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A 69-year-old man presented to the Emergency Department with 1 day of acute spontaneous vertigo, left-sided tinnitus and hearing loss. He had no otalgia, previous vertigo or hearing problems but did have a background of diabetes and hypertension. On examination, with fixation, there was no nystagmus, but without visual fixation (using Frenzel’s goggles), there was primary position left-beating nystagmus. The horizontal head-impulse test was negative, but his left Dix-Hallpike positional test was positive, provoking a paroxysm of up-beating, torsional nystagmus with vertigo. Otoscopy was normal with no vesicles. Weber’s test was positive to the right and Rinne’s was bilaterally negative. Smooth pursuit, saccades and cerebellar examinations were normal. Audiometry identified a left-sided profound and high-frequency and moderate-to-severe mid-frequency sensorineural hearing loss; right-ear audiometry identified only a mild high-frequency sensorineural hearing loss (figure 1A). He had acoustic reflexes in both ears at normal thresholds. Figure 1 (A) Asymmetric audiogram at initial presentation. Right ear shows a mild high-frequency sensorineural hearing loss, while the left ear shows a sloping mild-to-profound sensorineural hearing loss. (B) Left vestibular loss. Three-dimensional video head impulse at initial presentation shows isolated reduced left posterior semicircular canal vestibulo-ocular reflex gain (0.19) with catch-up saccades. (Gain values are listed to the top right of each individual head-impulse test.) (C) Repeat audiometry at 2 months. In comparison with the original audiogram, the right-ear results showed new upsloping severe-to-mild sensorineural hearing loss below 1 kHz and mild hearing loss above 1 kHz. The left-sided hearing has returned to normal at the low-to-mid frequencies after corticosteroid treatment. (D) Home audiometry over 45 days showing marked fluctuations in the right ear across the low-to-mid frequencies (≤1 kHz, red and orange traces). (E) The left ear shows little fluctuation in hearing loss. (F) Timeline of treatment. There was marked response in the left hearing loss, as …

Susac's syndrome (SS) is the triad of encephalopathy, branch retinal artery occlusions and sensorineural hearing loss. While rare, it has become increasingly recognised since characteristic ‘snowball’ corpus callosum lesions were appreciated on MRI.1 We present clinical and histopathological findings on three patients with SS. Our findings demonstrate a T-cell-mediated inflammatory contribution to lesion pathogenesis. Treatment with the tumour necrosis factor (TNF) inhibitor, infliximab was beneficial in two patients, including in one previously reported,2 and in another who failed rituximab. This report provides a histological rationale for the observed benefit of infliximab, and suggests that infliximab should be considered as an adjunct therapy in patients with refractory SS. Three patients with SS most recently diagnosed among the authors’ practices who had undergone brain biopsy as part of their diagnostic clinical workup were identified. The clinical features, radiology, treatment and outcomes for the three patients are presented as online supplementary data (tables S1–S5 and figures S1 and S2). Extensive serum autoantibody screening was negative. Headache was present in all patients, highlighting the fact that it is a common manifestation of encephalopathy in SS. All three cases reported relatively non-specific auditory and visual symptoms, emphasising that fluorescein angiography±audiology testing should be considered in the diagnostic workup of patients with unexplained encephalopathy. Two patients underwent cerebellar biopsies and one a frontal lobe biopsy. One biopsy was from a treatment-naive patient (case 1). All contained variable numbers of wedge-shaped microinfarcts surrounded by microglia. In cerebellar biopsies (cases 1 and 3), …