Hydatid cyst is the most common parasitic disease in the Mediterranean region, the Middle East and South America. It is also a medical and economic problem in Turkey. The agents responsible for hydatid disease are Echinococcus granulosus and E. multilocularis. Intracranial extradural localization of a hydatid cyst is very rare. There are only two previously published case reports concerning both supra-and infra-tentorial localization of cysts (Beskonakli et al. 1996, Turgut 1997), but the present case is the first report in the literature of removal of a complete cyst without rupture.
A 23-year-old man was admitted to our clinic complaining of headache, nausea, vomiting and imbalance. Physical examination revealed softness in the left occipital region. There was bilateral papilledema, abnormal left cerebellar tests and ataxia. Laboratory tests were normal except for elevation of the erythrocyte sedimentation rate (45 mm/h). Plain roentgenograms of the cranium showed a defect in the left occipital bone. Cranial computerized tomography (CT) images revealed a cystic lesion of similar density to cerebro-spinal fluid (CSF) in the posterior fossa and a focal defect in the adjacent occipital bone (Fig. 1A,B). Due to the patient's previous trauma history, it was first evaluated as a leptomeningeal cyst. Magnetic resonance (MR) images revealed a hypo-intense cystic mass in the left occipital region in T1(relaxation time)-weighted and hyper-intense in T2-weighted MR projections. The cyst extended above and below the tentorium and had an extradural location (Fig. 2). During surgery, after performing a large parieto-occipital skin flap, the cyst wall was seen through the occipital bone defect. The borders of the defect were carefully extended along the occipital and suboccipital regions. The extradural cyst was removed completely without rupture using Dowling's technique (Carrea et al. 1975). After the cavity was entirely irrigated with hypertonic solution, cranioplasty was performed in the area of the craniectomy defect.