[HTLV-I associated myelopathy (HAM) with cerebellar atrophy presenting a down-beat nystagmus].

A 67-year-old woman began to have difficulty in walking due to spastic paraparesis, sensory impairment in the lower limbs and instability on standing at the age of 59 years. Eight years later, she developed complete spastic paraplegia and urinary incontinence. On examination, she was found to have down-beat nystagmus and ocular hypermetria. Brain CT scan and MRI revealed cerebellar atrophy, predominantly in the vermis. HTLV-I antibody titer was increased in both serum and cerebrospinal fluid (CSF). She was diagnosed as having HAM and placed on prednisolone, salazosulfapyridine and high-dose vitamin C. Her symptoms including gait disturbance, nystagmus and ocular hypermetria improved but did not completely disappear. In parallel with clinical improvement, the antibody titer to HTLV and the ratio of CD4/CD8 lymphocyte subsets in blood decreased. The above observations suggest that the cerebellar signs and cerebellar atrophy share the same etiology with HAM. The presence of nystagmus and prominent cerebellar signs plus the CT and MRI findings strongly suggest that the lesions in HAM are not limited to the spinal cord but extend to the brainstem and cerebellum.