Demyelinating lesions behaving like aggressive tumours on advanced MRI techniques.

Tumefactive demyelinating lesions are a rare disorder in which inflammatory demyelination manifests as solitary or multiple focal brain lesions (greater than 2 cm in size), which can be mistaken for glioma, lymphoma, metastasis and in some cases even brain abscess. The symptomatology of tumefactive demyelinating lesions depends on the white matter area involved and includes quickly progressing neurological deterioration of motor, sensory and visual function, praxis, language and mood impairment, as well as seizures. Recognising the key imaging features in a patient with a prior history of demyelination may expedite appropriate management. Preoperative diagnosis or at least the consideration of a demyelinating process is important to avoid unnecessary surgery. We report three patients with demyelinating lesions who presented with findings suggestive of demyelination on conventional magnetic resonance imaging studies. However, in all patients the lesions showed high perfusion and in two high permeability, which are findings generally seen with high-grade neoplasias. In rare instances, tumefactive demyelinating lesions may show increased perfusion and high permeability, imaging findings more commonly seen in high-grade gliomas. We suggest that if white matter lesions on conventional magnetic resonance imaging are compatible with tumefactive demyelinating lesions, atypical findings of high perfusion/permeability should not dissuade the radiologist from suggesting the presence of tumefactive demyelinating lesions rather than high-grade gliomas.