Hydatid cyst of the brain: Typical MRI findings


     Hydatid cyst ((HC) of the brain results from arterial embolism secondary to ingestion of multiple larvae . Intracranial hypertension and motor weakness due to increased intracranial pressure are the most common clinical manifestations. Most commonly, cerebral HC are single lesions and locate anywhere within the brain, but are especially located in the middle cerebral artery territory. The parietal lobe is the most frequently involved region. HC of the brain are usually single, spherical, unilocular, and may be large ; in rare instances, they can be multiple and embolic. Both CT and MRI demonstrate a spherical and well-defined, smooth, thin walled, homogeneous cystic lesion with fluid density similar to the cerebrospinal fluid, with or without septations or calcification. The cyst wall usually showed a rim of low signal intensity on both T1- and T2-weighted images. Compression of the midline structures and ventricles are seen in most of the cases, however surrounding oedema and rim enhancement are usually absent in untreated or uncomplicated cases. The HC is usually hypointense in diffusion weighted images and Proton MR Spectroscopy demonstrate lactate, alanine and pyruvate within the lesion. Pyruvate is very characteristic of hydatid cyst. This metabolite may be a marker of parasitic etiology and perhaps that of viability of such intracranial cysts. The serologic tests are of little practical value in confirming the diagnosis of cerebral echinococcal disease. Surgery is the standard and most effective treatment for intracranial HC.


Written by: Dr. Hasni Bouraoui I, Imaging Department, Sahloul Hospital, Tunisia


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