Progressive Spastic Paraparesis in a Woman from Guyana

A 66-year-old woman originally from Guyana presents because she can no longer walk. For 3 years she has had progressive bilateral leg numbness and tingling, stiffness, heaviness, and urinary incontinence. She first needed a cane, then a walker, and now cannot stand without assistance.

She reports intermittent low back pain but no recent fever, rash, or acute infectious illness. Her history includes lumbar disc herniation and a remote knee ligament injury. She takes no medications. On examination, mental status is intact. Tone is markedly increased in both lower extremities with clear spasticity. Iliopsoas strength is 3/5 bilaterally, while knee extension, ankle dorsiflexion, and plantar flexion are 4/5. Reflexes are diffusely brisk with bilateral Hoffman's signs and upgoing toes. Vibratory sensation is reduced at the feet and ankles.

MRI of the total spine shows only moderate degenerative changes without cord compression, cauda equina syndrome, or another structural lesion to explain the examination. EMG and nerve conduction studies demonstrate a distal sensorimotor axonal neuropathy with some demyelinating features, but these findings do not fully account for the severe spastic paraparesis. Lumbar puncture is then performed and shows a mild lymphocytic pleocytosis with modestly elevated protein. Neurology asks for an infectious diseases evaluation, and a broader workup is sent including HIV, RPR, and HTLV-1 testing from serum and CSF.