Third Ventricle Floor Variations and Abnormalities in Myelomeningocele-Associated Hydrocephalus: Our Experience with 455 Endoscopic Third Ventriculostomy Procedures.

AIM To evaluate the incidence of anatomical variations and abnormalities of the third ventricle floor encountered during the endoscopic third ventriculostomy (ETV) procedure in myelomeningocele-associated hydrocephalus (MAH) cases. MATERIAL AND METHODS A retrospective analysis was performed on 455 pediatric MAH cases that had been treated with ETV. This case series consisted of the patients who were initially treated with ETV and also those who were treated with ETV for the management of cerebrospinal fluid shunt dysfunction. Variations and anomalies of the third ventricle floor were determined by reviewing the video records of the ETV procedures. RESULTS The analysis of the data revealed that the rate of the MAH cases with variations and abnormalities of the third ventricle floor was 41.1%. The most common anatomical features were "thick and prominent massa intermedia" (37.1%) and "narrow tuber cinereum" (33.1%). CONCLUSION This study documents the most common anatomical variations and abnormalities of the third ventricle floor in cases with MAH. Various anatomical situations and specific ventricular configuration of MAH cases may add an operative factor of difficulty which should be well recognized by the neurosurgeon who plans and executes an ETV procedure in this patient population.