Complete washout of a colloid cyst on MRI after partial removal by endoscopic approach

Abstract

Dear Sir, We would like to bring to your attention a case of progressive disappearance of a colloid cyst after endoscopic resection of a minor portion of the lesion, as documented by magnetic resonance imaging (MRI). This right-handed 50-year-old male presented with general fatigue associated with disturbance of concentration and intermittent headache. Clinical neurological examination was normal. A computed tomography (CT) and an MRI of the brain revealed a cystic lesion in the area of the foramen of Monro in the roof of the third ventricle. On CT, the lesion was hyperdense. On MRI, the lesion was hyperintense on T1-weighted images and hypointense on T2-weighted images. The cyst obstructed the foramen of Monro (Fig. 1) leading to hydrocephalus of both lateral ventricles. Image-guided endoscopic removal of the lesion was performed through a right frontal approach under general anaesthesia (Fig. 2). Only a minor portion of the lesion was removed by the endoscopic approach considering the risk of traction on the fornix through the chosen trajectory. No complication occurred during surgery. Histological examination showed the typical aspect of a colloid cyst. A postoperative MRI, performed 48 h after the surgery, revealed only a slight decrease of the dimensions of the cyst (Fig. 3). There was a clear decrease in the size of the lateral ventricles, suggesting a better permeability of the foramen of Monro. Postoperatively, the symptoms of the patient disappeared and he was discharged 5 days later. Postoperative MRIs performed at 3 months and every year until 4 years after surgery surprisingly revealed a progressive disappearance of the colloid cyst with complete permeability of the foramen of Monro (Fig. 4). Third ventricular colloid cysts are rare benign lesions which are typically hyperintense on T1 and hypointense on T2-weighted MRI [1–9]. The correlation of the T1weighted MR imaging hyperintensity of the cyst and a high concentration of cholesterol in colloid cyst has been documented by Maeder et al. [7]. This was also confirmed in our patient at histological examination. Although recurrence of colloid cysts after total removal is exceptional, the postoperative radiological follow-up of a partially removed lesion has not been reported in the literature [5, 6, 10–12]. Our case shows that even partial removal of a colloid cyst can result in total washout of the lesion without recurrence during a 4-year follow-up. T. Robert (*) :M. Levivier :C. Pollo Department of Neurosurgery, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland e-mail: Thomas.robert43@gmail.com