Magnetic resonance imaging of simple and infected hydatid cysts of the brain.

Hydatid cyst of the brain is more common in children than adults. The cyst is always solitary unless the primary site is the brain. Cerebral hydatid cyst (CHCy) is most frequently supratentorial involving the territory of the middle cerebral artery, especially the parietal lobe. This study included 16 patients who were treated for CHCy. They were 11 male patients (68.75%), and 5 female patients (31.25%), ranging in age from 6 to 40 years with an average age of 14.7 years. Most of the patients were children-12 patients (75%), between 6 to 16 years of age. All patients were from rural areas. Headache, vomiting and seizures were the predominant symptoms. Papilloedema was present in 12 patients (75%). CT and MRI were performed in all patients. The cysts were all located in the cerebral hemispheres, except one in the posterior fossa, (Rt. cerebellar hemisphere). One lobe alone was affected in 7 patients (43.8%), two lobes in 6 patients (37.5%) and 3 lobes in two patients (12.5%). Round, or oval well defined cystic lesions isointense to the CSF in T1 and T2WI, with hypointense walls in T2WI and no surrounding perifocal edema or evidence of contrast enhancement were seen in 12 patients (75%) and were classified as simple or non-complicated CHCy. Cystic lesions with surrounding, T2 hyperintense area of perifocal edema, complete and incomplete (segment) rim of contrast enhancement were seen in 4 patients (25%), and were labeled as complicated or infected cysts (cysts with superadded pyogenic infection). All patients were treated surgically, hydatid birth (delivery of unruptured cyst) was achieved in 10 patients, cyst rupture occurred in 6 patients (37.5%), with subsequent recurrence (3 patients with recurrent multiple cysts and 3 patients with recurrent solitary cysts). All the recurrent cysts were surrounded by perifocal edema and showed ring enhancement. MRI has proved to be an excellent means of studying CHCy. It will be more widely used for diagnosis and surgical planning. It provided information about the exact cyst localization, cyst contents and presence or absence of superadded cyst infection.