Tension pneumoventricle after excision of third ventricular tumor in sitting position

Occurrence of tension pneumoventricle (symptomatic intraventricular air) can result in rapid clinical deterioration in an otherwise stable patient. It is a rare clinical entity, mentioned in relation to cerebrospinal fluid (CSF) diversion procedures, during the late postoperative period. We present a patient with posterior third ventricular tumor who underwent excision by midline suboccipital craniotomy in sitting position. Neurological status of the patient deteriorated rapidly in the immediate postoperative period owing to development of tension pneumoventricle. The condition improved after twist-drill burr-hole evacuation of air under water-seal. Pre-existing gross hydrocephalus, exploration of third ventricle in sitting position, and residual tumor in third ventricle were possibly the factors responsible for this complication.