Introduction The usual manifestations of Behc¸ et’s disease are oral and genital ulceration, uveitis, and skin lesions. Other organ systems may also be affected, including the nervous system [1]. Central nervous system (CNS) involvement is well defined [2, 3, 4]. It can be divided into two major types: parenchymal, which is mainly a meningoencephalitis, and involvement of CNS vessels leading to neurological dysfunction [5]. The former is usually manifested as a brain-stem syndrome with pyramidal findings, cognitive impairment, ataxia and sphincter disturbance [6], whereas the latter usually causes raised intracranial pressure (RICP) due to dural sinus occlusion or, very rarely, an arterial stroke syndrome [7]. MRI is a useful tool for detecting CNS lesions in Behc¸et’s disease [4, 8], and small series have been pub- lished. The lesions are usually in the brain-stem, basal ganglia or deep hemisphere white matter [8, 9, 10]. A recent report of MRI findings in 65 patients supports these observations [11]. A few longitudinal studies G. Akman-Demir S. Bahar O. Coban B. Tasci P. Serdaroglu Cranial MRI in Behc ¸ et’s disease: 134 examinations of 98 patients Received: 6 June 2003 Accepted: 15 August 2003 Published online: 14 October 2003 Ó Springer-Verlag 2003 Abstract Two observers, blinded to the patient’s neurological status, re- viewed 134 MRI studies of 98 con- secutive patients with Behc¸et’s disease (BD), to define imaging pat- terns and to look for any relation- ship between the MRI findings and the timing of the examination in patients with differing courses of disease. There were 43 patients with overt parenchymal central nervous system (CNS) involvement, 22 with attacks and remissions, 15 with sec- ondary progressive and six with primary progressive disease; 14 had raised intracranial pressure (RICP). Of the remaining 41 patients with- out specific neurological complaints, 16 had abnormalities on examina- tion (silent CNS involvement) and 25 did not. During an acute CNS attack, the most common finding was a large lesion in the brain-stem or basal ganglia, extending to the diencephalon. On MRI performed after remission of an acute attack or during secondary progression, the same sites were affected, but the le- sions were smaller or scattered, with less clearly defined margins. In pri- mary progressive disease or silent CNS involvement, the cerebral white matter was most commonly in- volved, but almost half the MRI studies were normal. The brain parenchyma was abnormal in only one of the patients with RICP. MRI was normal in all but three patients without clinical CNS involvement, in whom it showed a few millimetric white-matter lesions. Brain-stem atrophy was seen in 15 patients examined >1 year after an initial parenchymal CNS episode, with secondary progressive cases predominating. Keywords Behc¸ et’s disease Æ Neuro- logical involvement Æ Magnetic resonance imaging Part of this work was presented at the Eighth International Conference on Behc¸et’s Disease, Reggio Emilia, October 1998 and at the Eighth Meeting of the European Neurological Society, Nice, June 1998 Neuroradiology (2003) 45: 851–859 DOI 10.1007/s00234-003-1102-1 DIAGNOSTIC NEURORADIOLOGY G. Akman-Demir (&) Æ S. Bahar O. Coban Æ B. Tasci Æ P. Serdaroglu Department of Neurology, Istanbul Medical Faculty, Istanbul University, Capa, 34390 Istanbul, Turkey E-mail: akmandemir@turk.net Tel.: +90-212-4142000 Fax: +90-212-5334393