Olfactory groove colloid cyst – A case report in an unusual location

ABSTRACT Colloid cysts are benign cystic lesions, commonly seen within the third ventricle with characteristic radiological appearance. The extraventricular location of these cysts is very rare and includes cerebral and cerebellar hemisphere, cavum veli interpositi, sella and brainstem. Amongst the reported extraventricular cysts, colloid cysts in the olfactory region cysts are very rare and only two cases have been reported so far. Hereby, we present a 29-year-old female with complaints of right-sided frontal headache for 2 weeks of duration. Magnetic resonance imaging showed a well-defined altered signal intensity cystic lesion in the region of the right olfactory groove appearing hyperintense on T2/FLAIR. Histopathology examination revealed a benign cyst lined by ciliated pseudostratified epithelium. Although rare, colloid cysts should be included in the differential diagnosis of cystic lesions in the anterior cranial fossa. The outcome depends on the location and erosion of dura, which may pose an imminent danger for cerebrospinal fluid leak. The identification of these cysts in extraventricular location will help for better understanding of the origin and histogenesis.