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A 63-year-old man with a history of well-controlled hypertension, lumbar stenosis, and hip arthroplasty with revisions presented with bilateral loss of vision and hearing for several weeks. He also reported a history of painful paresthesias at his feet beginning about 1 year prior.
On examination, his visual acuity was initially 20/80 OD and 20/200 OS; it deteriorated over the next 2 months to finger counting bilaterally. The Weber test gave a nonlateralizing result, and bone conduction hearing was absent bilaterally. There was length-dependent loss of vibratory sensation and absent reflexes at both lower extremities. Magnetic resonance imaging demonstrated abnormal enhancement of bilateral optic nerves (Figure, A). Optical coherence tomography and fluorescein angiogram were normal. Nerve conduction studies showed mild sensory axonal polyneuropathy. Laboratory tests were notable for elevated thyrotropin (63 mlU/ml), low levels of free thyroxine (T4) (0.2 ng/dL), and elevated levels of cerebrospinal fluid protein (94 mg/dL). Cerebrospinal fluid IgG index, oligoclonal bands, aquaporin 4 antibody, paraneoplastic panel, and protein electrophoresis test results were all normal. He was treated empirically with high-dose steroids and plasmapheresis, with no improvement in symptoms.
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D. Cobalt toxicity
The patient’s prior hip replacement surgeries raised the possibility of cobalt toxicity as a cause of his constellation of symptoms. The patient had his first hip replacement surgery 7 years prior to presentation with a ceramic-on-ceramic implant and had required 2 revision surgeries. During the revisions, which occurred 2 years prior to presentation, extensive soft-tissue metallosis was noted. Given this history of failed hip replacement, serum cobalt levels were checked and were consistently elevated, ranging between 280 to 779 ng/mL (a normal level is less than 1.5 ng/mL). A plain-film radiographic image of the hip showed that the hardware was intact, and there was heterotopic ossification in the surrounding soft tissue (not shown). Magnetic resonance imaging demonstrated a pseudotumor of metallosis (Figure, B). The patient was referred to orthopedic surgery for revision but died before surgical intervention.
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Corresponding Author: Perry B. Shieh, MD, PhD, Department of Neurology, University of California, Los Angeles, 710 Westwood Plaza, Los Angeles, CA 90095 (email@example.com).
Published Online: July 23, 2018. doi:10.1001/jamaneurol.2018.1868
Conflict of Interest Disclosures: None reported.
Additional Contributions: We thank the family of the patient for granting permission to publish this information.
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