Differential diagnosis of posterior fossa multiple sclerosis lesions--neuroradiological aspects.

Various infratentorial pathological conditions can mimic multiple sclerosis (MS) both clinically and radiologically. We review the inflammatory, vascular, neoplastic and metabolic conditions which show features similar to those of MS on magnetic resonance imaging (MRI). Behcet's disease, Lyme disease, progressive multifocal leukoencephalopathy, neurosarcoidosis, Whipple's disease, listeria rhombencephalitis, Bickerstaff's brainstem encephalitis, vasculitis due to systemic lupus erythematosus, and acute disseminated encephalomyelitis produce inflammatory lesions similar to those of MS in the brainstem and cerebellum. Neoplastic diseases, in particular pontine gliomas and lymphomas, can mimic MS. Vascular ischaemic lesions, either due to infarction produced by occlusion of a major posterior circulation artery or due to small vessel vasculopathy, can lead to posterior fossa lesions. The MRI changes of central pontine myelinolysis can also mimic MS. Diffuse axonal injury, radiation and chemotherapy induce lesions that resemble MS, however the clinical history will exclude these possibilities. Finally, we discuss a few conditions which are similar to MS in clinical presentation but have different MRI appearances, such as brainstem cavernomas, posterior fossa tumoural lesions, aneurysms and vascular loops producing neurovascular conflicts. Analysis of the MRI findings with clinical history and laboratory data helps to narrow down the diagnosis of the infratentorial pathology.