Transventricular Endoscopic

Intraventricular endoscopy uses rigid or flexible endoscopes passed through a burr hole into the lateral ventricle and, through the foramen of Monro, into the third ventricle. Endoscopic third ventriculostomy (ETV) creates an opening in the floor of the third ventricle into the interpeduncular and prepontine cisterns, bypassing an obstruction at or below the aqueduct and avoiding a shunt.

• Obstructive hydrocephalus from aqueductal stenosis, tectal and pineal-region tumours, and posterior-fossa lesions.
• Biopsy of intraventricular and paraventricular tumours, often combined with ETV in pineal-region tumours^[1].
• Fenestration of suprasellar, intraventricular and quadrigeminal arachnoid cysts.
• Septostomy for isolated lateral ventricles, and removal of selected colloid cysts.

In childhood hydrocephalus, the success of ETV depends mainly on the patient's age, the cause of hydrocephalus and whether a shunt has been placed before. Kulkarni and colleagues combined these factors into the ETV Success Score, which predicts the chance that ETV will work, and showed that children with high scores do better with ETV than with a shunt after the early postoperative period, whereas those with low scores fare better with a shunt^[2,3]. Infants under six months, post-infectious and post-haemorrhagic hydrocephalus have lower success rates.

Entering the lateral ventricle, the foramen of Monro is found by following the choroid plexus and the thalamostriate and septal veins forward to their junction; the fornix forms its anterior and superior border. In the floor of the third ventricle, the mammillary bodies lie posteriorly and the infundibular recess anteriorly; the stoma is made in the thin, often translucent tuber cinereum in the midline just in front of the mammillary bodies, above the clivus and in front of the basilar apex^[4].

• Supine, head neutral and slightly flexed; burr hole just anterior to the coronal suture in the mid-pupillary line, planned on MRI or navigation for a straight line through the foramen of Monro to the floor.
• Cannulate the frontal horn and introduce the endoscope; irrigate with warmed Ringer's solution.
• Identify the foramen of Monro and pass into the third ventricle without stretching the fornix.
• Perforate the floor in the midline between the mammillary bodies and the infundibular recess, away from the basilar artery, using a blunt instrument; dilate the opening with a balloon catheter.
• Inspect the prepontine cistern and open any underlying membrane (Liliequist's membrane) to ensure free flow.

• Basilar artery injury, the most dangerous complication: perforate the floor in the midline anterior to the basilar apex and avoid thermal energy near the artery.
• Fornix injury and memory loss from excessive torque at the foramen of Monro.
• Hypothalamic injury causing diabetes insipidus, hyperphagia or electrolyte disturbance.
• Late failure from closure of the stoma; sudden late deterioration has been reported and patients need follow-up.