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We present the case of a 76 year old right-handed lady admitted with seizure and acute left-sided weakness. Brain MRI revealed bilateral subdural collections with left parietal superficial siderosis. An MRI of the spine was subsequently arranged to look for CSF leak as a cause of intracranial hypotension, which showed an intradural nodule at the T6 spinal level. CT myelography demonstrated a dural tear around this lesion as a potential source of CSF leak.During the resection of the thoracic lesion, which was confirmed as a meningioma, the surrounding dura was noted to be abnormally thickened, and biopsied intra-operatively. The samples revealed eosinophilic, anucleate material without evidence of inflammation or malignancy.The patient subsequently developed worsening mobility and progressive cognitive impairment characterised by word-finding and short-term memory difficulties and executive dysfunction. Repeat MR imaging showed extensive leptomeningeal contrast enhancement. She became markedly hypothyroid.The dural sample was re-examined and stained with Congo red, revealing a characteristic apple-green birefringence consistent with a presumptive diagnosis of central nervous system amyloidosis. Genetic testing found her to be the heterozygous carrier of a variant of unknown significance in the TTR gene (c.296G>C).Hereditary TTR amyloidosis typically causes symptoms affecting peripheral nerves, but there is early brain accumulation of the defective transthyretin protein. We discuss this unusual route to diagnosis, the significance of the novel genetic variant, and the limited evidence for treatment.rbb29@cam.ac.uk