Teaching Video NeuroImage: HTLV-1-Associated Myelopathy With Downbeat Nystagmus

A 54-year-old woman presented from the Dominican Republic for evaluation of 18 years of progressive lower extremity weakness and urinary incontinence. Her examination was notable for spastic weakness of the lower extremities, absent distal vibration sense, pathologic hyperreflexia, and downbeat nystagmus in all directions of gaze (Video 1) without dysmetria or other cerebellar deficits. MRI showed severe spinal cord atrophy (Figure). HTLV-1 antibodies were present in CSF and serum. The CSF IgG index was elevated, and >5 CSF-specific oligoclonal bands were present. Nutritional and serum/CSF autoantibody testing, including for anti-GAD65, was unrevealing. Although HTLV-1 is classically associated with myelopathy and hematologic malignancies, it is also critical to recognize HTLV-1-associated spinocerebellar syndromes, including ataxia and nystagmus, in patients from HTLV-endemic regions.(1,2,e1-2) Downbeat nystagmus can be seen in patients with not only HTLV-1 but also cerebellar flocculus or cervicomedullary junction lesions, spinocerebellar ataxias, drug toxicities, and immune-mediated cerebellar degeneration.