We report the results of serial computerized tomography (CT) and magnetic resonance imaging (MRI) in a 9-month-old Japanese girl with the rare disorder, congenital sensory neuropathy with anhidrosis (CSNA). She developed a prolonged high fever, anorexia, and weight loss with laboratory findings of hemoconcentration and elevated levels of GOT, LDH and creatine phosphokinase (CK) in May 1995, and was hospitalized. The cerebrospinal fluid (CSF) was normal on admission. Elevation of CSF myelin basic protein on the 16th hospital day suggested a destruction of the myelin sheath. The first MRI performed on the 16th hospital day revealed no marked abnormalities when the patient exhibited a high fever, generalized tonic-clonic convulsions, and impaired consciousness. The patient had a persistent high fever, and developed a second generalized tonic clonic convulsion and became comatose. A second MRI on the 20th hospital day showed a bilateral symmetrical paracentral hypo-intensity of the white matter with occipital hypo-intensity on T2-weighted images. MRI findings were considered to represent the complications of the high fever with a loss of water from the cerebral cortices and deep white matter. MRI and CSF findings indicated the presence of brain damage due to the high fever.