Sarcoid tumour: continuing diagnostic problems in the MRI era.

The eVects of sarcoidosis on the nervous system are protean. They include involvement of the meninges (cranial nerve palsies, pituitary, and hypothalamic eVects), peripheral nerves (symmetric polyneuropathy, multifocal neuropathy), and brain parenchyma (lesions of brain and spinal cord without obvious meningeal involvement); and also secondary effects of systemic disease, such as intracerebral haemorrhage related to sarcoid induced thrombocytopenia. Solitary sarcoid mass lesions of the CNS, mimicking tumours, have been described but are rare, with less than 100 cases in the world literature. They may either arise from the dura or be located entirely within the parenchyma, with radiological appearances which resemble meningioma and glioma respectively. Computerised tomography was generally not helpful in distinguishing these lesions from other intracerebral masses and it was therefore hoped that the advent of MRI would be useful in the diVerentiation of sarcoid tumours. We present two patients with solitary intracerebral mass lesions which were thought to be tumours, in whom the diagnosis of neurosarcoidosis was entirely unexpected until histological specimens were available, despite appropriate MRI. Case reports