A 26-year-old woman gave a 2-year history of intermittent and worsening headaches. MR scan of brain showed a 1.1 cm cystic, peripherally enhancing lesion in the third ventricle, causing obstructive hydrocephalus at the interventricular foramen of Monro (figure 1A, B). She underwent endoscopic intraventricular resection through a left frontal burr hole. Pathological examination confirmed a colloid cyst.

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Figure 1

(A, B) Preoperative MRI, T1 with gadolinium: axial and coronal images show ventriculomegaly and a rounded, peripherally enhancing cystic lesion at the foramen of Monro. (C, D) Postoperative MRI, T1 with gadolinium: axial and coronal images show resection of the colloid cyst.

Colloid cysts are histologically benign lesions thought to arise from a pouch-like evagination of the diencephalic roof during embryonic development.1 An epithelial layer of varying composition contains the thick, gelatinous cyst contents, which may comprise mucin, blood breakdown products or cholesterol crystals. In 1921, Walter Dandy resected a colloid cyst using an open, transcortical approach through the frontal lobe. Since then, surgeons have used several approaches, including transcallosal, to resect these lesions.2 ,3 Although the interhemispheric transcallosal approach provides access to the third ventricle with less cortex manipulation, it carries an increased risk of postoperative seizures, hydrocephalus and cortical venous injury.4 ,5 Endoscopic technologies offer neurosurgeons new and less invasive ways to remove such lesions safely. Our video (see online supplementary material) shows endoscopic intraventricular views and demonstrates the steps involved in the patient's surgical procedure.

Following endoscopic surgery, she recovered well (figure 1C, D show postoperative MRI) with improvement in her headache symptoms.