[A case of HTLV-1 associated myelopathy with diffuse white matter lesion of the frontal lobe and continuous lesion of the pyramidal tract on cranial MRI].

: In this report, the characteristic findings of cranial MRI of a case with HTLV-1 associated myelopathy (HAM) is described. The patient was a 62-year-old woman with 6 years history of paraplegia. Her main clinical signs were bilateral spastic paraplegia in the lower limb girdle muscles and extremities, paresthesia below the tenth thoracic cord level and urinary disorder. There was bilateral blepharoptosis. Hyperreflexia was observed in the examination of the cranial nerves and upper extremities. She showed no dementia or any other higher cortical dysfunctions. Positive anti-HTLV-1 antibody in the serum and cerebrospinal fluid established a diagnosis of HAM. T2 weighted MRI study revealed the symmetrical diffuse hyperintensity in the subcortical white matter of the frontal lobe and temporal lobe. The hyper-intensity was also observed in the bilateral internal capsule-peduncular base junction and pontine base, which indicated the continuous lesions in the intracranial pyramidal tracts. These MRI findings were different from those of reported cases of scattered lesion in central nervous system. There are some speculations for the nature of the diffuse lesion in the white matter, i.e., fusion of solitary gliosis and/or perivascular cuffing, or diffusely advanced spongy state. The continuous lesion of the pyramidal tract is suspected a systemic demyelination. Although the pathomechanism still remains uncertain, HTLV-1 infection generally affects the spinal pyramidal tract. It seems that this case is selectively affected in the pyramidal tracts in CNS.