Endoscopic Fenestration of Enlarging Symptomatic Thalamic Cysts: Twin Cases

This operative video (Video 1) report demonstrates 2 cases of endoscopic fenestration for enlarging symptomatic thalamic cysts causing obstructive hydrocephalus. A literature review of 29 cases (1987-2026)^1-17 reveals hydrocephalus present in the majority of cases. Common presentations include headache, gait disturbance, and cognitive changes. The first case involves a 62-year-old female with progressive proprioceptive deficits and imbalance due to a 2.5 cm right thalamic cyst protruding into the third ventricle. The second case involves a 59-year-old female presenting with altered mental status and headaches from an enlarging right thalamic cyst. In both cases, a frontal transcortical endoscopic approach was utilized to fenestrate the cysts into the lateral and third ventricles in combination with an endoscopic third ventriculostomy. To ensure precise access, 2 separate trajectories were employed: one providing a straight-line path to the cyst wall and another to the floor of the third ventricle. Fenestration was achieved using blunt dissection and Fogarty balloon dilation, followed by further enlargement with alligator clamps. Postoperatively, both patients experienced complete resolution of symptoms and mass effect. These cases illustrate that while benign thalamic neuroepithelial cysts are rarely symptomatic,¹⁰ they can be effectively treated with endoscopic fenestration. While treatment approaches in the literature vary, endoscopic or microsurgical fenestration remains the most common intervention. This technique, utilizing a high-resolution rigid endoscope coupled with stereotactic navigation and preoperative trajectory planning, allows for safe and effective treatment of these deep cystic lesions.