Microsurgical outlet restoration in isolated fourth ventricular hydrocephalus: a single-institutional experience

Isolated fourth ventricles as a consequence of shunted posthemorrhagic hydrocephalus can cause significant brainstem compression and subsequent clinical deficits in children. Several treatment options have been described. We report the clinical and radiological outcome after microsurgical fenestration of fourth ventricular outlet foramen via a suboccipital approach.

In nine patients (age, 9 to 87 months; median age, 21 months), microsurgical reopening of formerly occluded outlet foramen of the fourth ventricle was performed under electrophysiological monitoring. Pre- and postoperative clinical outcome as well as radiological results are reported.

Mean follow-up for all children was 25 months. Three children older than 3 years were less significantly involved, the remaining six showed tremendous long tract signs and lower cranial nerve deficits. All children exhibited a remarkable improvement of their preexisting neurological deficits post-surgery. Despite successful fenestration, one child required additional internal drainage of fourth ventricle to the lateral ventricles due to malabsorption. Median diameters of the fourth ventricle changed markedly after surgery with anterior-posterior (a.p.) extension from 3.8 to 2.9 cm, lateral extension from 4.2 to 2.8 cm (p = 0.018), and craniocaudal extension from 5.8 to 4.7 cm, respectively. Also, the pontine a.p. diameter increased significantly from 0.8 to 1.5 cm (p = 0.022).

The clinical and radiological outcomes after microsurgical fenestration in children with an isolated fourth ventricle are very promising. This treatment modality is a safe and effective shunt-free option when electrophysiological monitoring and thorough preoperative neuroradiological work-up are applied.