Hearing Loss, Imbalance, and Diplopia in a 44-Year-Old Man

A 44-year-old man sought care for new right-sided tinnitus and sensorineural hearing loss. He was treated with high-dose oral prednisone and acyclovir. Later, mild, intermittent dizziness developed, which progressed to constant, moderate dizziness and was exacerbated by sudden head movements. He participated in vestibular rehabilitation with only mild improvement. Within 5 months of tinnitus onset, horizontal binocular diplopia also developed. Examination showed spontaneous left-beating torsional nystagmus in primary gaze, down-beating nystagmus with leftward gaze, and right-beating torsional nystagmus in rightward gaze. Head impulse testing to the right produced a catch-up saccade. Dix-Hallpike maneuver in both positions led to leftward torsional nystagmus followed by down-beating nystagmus. He had full range of eye motion. There was evidence of asymmetric hearing loss on the right and moderate gait unsteadiness; he was able to complete only a few steps in tandem. Neurologic examination findings were otherwise normal. Oculomotor testing demonstrated abnormalities supportive of a central nervous system disorder. These included excessive square-wave jerks, impaired smooth pursuit, and direction-changing nystagmus. Results of cerebrospinal fluid studies included a normal opening pressure, pleocytosis, and increased protein concentration. Serum and cerebrospinal fluid paraneoplastic evaluations showed a unique immunofluorescence staining pattern on rodent brain tissue by patient immunoglobulin G, which was later confirmed to be immunoglobulin G antibodies to kelch like family member 11. Whole-body positron emission tomography showed a single anterior mediastinal mass, which was then resected. The patient was diagnosed with a paraneoplastic anti-kelch like family member 11 rhombencephalitis with an extratesticular seminoma. After removal of the mediastinal mass, intravenous methylprednisolone was started. The patient had symptom stabilization but no clinical improvement. Cyclophosphamide was added to the weekly pulse-dose intravenous corticosteroids. He had mild improvement in vertigo and gait imbalance. For symptomatic management of the vertigo, he received baclofen, citalopram, and vestibular rehabilitation. He continued to have slow improvement. After approximately 1 year of cyclophosphamide treatment, his gait normalized and nystagmus diminished, although he had persistent neurologic deficits including spontaneous down-beating nystagmus and a few intermittent square-wave jerks. The intravenous methylprednisolone infusions were tapered, with continued examination stability. After stable symptoms and examination findings, cyclophosphamide was discontinued. After discontinuation of cyclophosphamide, new central sensorineural hearing loss developed suddenly in his left ear. This improved with additional intravenous methylprednisolone treatment. Mycophenolate mofetil was also started, and corticosteroids were tapered. Repeated positron emission tomography of the body showed no recurrence of seminoma. Symptoms and audiography findings were stable after 10 months, so the patient elected to discontinue immunosuppression again and has remained stable. Kelch like family member 11 autoimmunity is a distinct paraneoplastic syndrome associated with encephalitis and testicular germ cell tumors (including seminoma).