Transthyretin amyloidosis and superficial siderosis of the CNS.

OBJECTIVE: To describe a previously unreported clinical and radiologic presentation of hereditary transthyretin (TTR)-related amyloidosis.
BACKGROUND: Unexplained cerebellar ataxia, pyramidal syndrome, and hearing loss are observed in some patients with TTR-related amyloidoses.
METHODS: We performed clinical, radiologic, and pathologic examinations of three family members with TTR-related (Ala36Pro) amyloidosis.
RESULTS: The patient was a 69-year-old woman with vitreal amyloid deposits, progressive sensorineural deafness, cerebellar ataxia, pyramidal syndrome, and recurrent transient neurologic symptoms. Cranial MRI showed symmetric thin rims of low signal intensity in T2- and T2*-weighted images in the cortex of the sylvian fissures, of the cerebellar hemispheres and vermis, and in the quadrigeminal plate consistent with superficial siderosis of the CNS. Her older daughter had vitreal amyloid deposits, acute Brown-Sequard syndrome at C4, acute sensorineural deafness, and recurrent transient neurologic symptoms. Cranial MRI at age 48 revealed a rim of low signal intensity in T2- and T2*-weighted images in the superior vermis folia and the right sylvian cortex. In addition, two small hemosiderin deposits were seen in the left parietal cortex. Lumbar puncture yielded colorless CSF with increased ferritin content and was followed by fourth ventricle hemorrhage. Cranial MRI 11 months later showed progression of brain hemosiderin deposits. The younger daughter had vitreal deposits, sensorimotor polyneuropathy, and acute sensorineural hearing but no evidence of siderosis on cranial MRI. She died at age 43 years of posterior fossa subarachnoid hemorrhage, and the neuropathologic examination showed amyloid deposition in the leptomeningeal spaces and vessels.
CONCLUSION: Transthyretin-related amyloidosis may cause superficial siderosis of the CNS through subarachnoid bleeding related to meningovascular amyloid deposition.