Intracranial lipomas: importance of localization

Intracranial lipomas are rare congenital malformations. They are usually pericallosal asymptomatic midline lesions. Other brain malformations are often seen in association with intracranial lipomas. We describe the findings of imaging studies, including computed tomography (CT), magnetic resonance (MR) imaging, and MR angiography, along with a brief review of the literature. The frequency and the spectrum of the associated brain malformations are also discussed. We retrospectively reviewed CT and MR findings of 24 patients (14 female, 10 male, mean age 38.6 years) diagnosed with intracranial lipoma between December 2000 and June 2004 in two different radiology departments. Seventeen of the patients were diagnosed using cranial MR and seven with cranial CT. The CT density of all lesions was measured. Imaging characteristics of lipomas, morphological findings and associated malformations were described. The intracranial locations of the lipomas were left-sided quadrigeminal cistern (n=3), right-sided quadrigeminal cistern (n=4), interpeduncular cistern (n=1), sylvian fissure (n=3), interhemispheric fissure (n=3), choroid plexus (n=2), intercerebellar fissure (n=3), corpus fornicis (n=1) and the periphery of the corpus callosum (n=4). Eighteen of the intracranial lipomas were tubulonodular; six were curvilinear. Associated anomalies were observed in six patients. All of the patients with sylvian fissure lipoma had seizures. The two preferential sites of intracranial lipomas were pericallosal and dorsal mesencephalic. Most intracranial lipomas are found incidentally during neuroradiological investigations. CT and MR examination usually lead to the diagnosis, because of the very low attenuation values of lipomas on CT and the short T1 and T2 on MR. Midline anomalies and other malformations such as aneurysms are frequently associated with intracranial lipomas. Careful radiologic evaluation is therefore necessary to evaluate associated pathologies. Sylvian fissure lipomas should be considered in the differential diagnosis of patients with epilepsy.