Pneumocephalus and pneumoventricle are most commonly found following trauma or intracranial surgery. Tension pneumoventricle is rare and may lead to reversible clinical deterioration. We report a case of tension pneumoventricle occurring after transsphenoidal surgery.

A 30-year-old male underwent transsphenoidal surgery for resection of a craniopharyngioma. The post-operative result was good (Figure 1). He developed a cerebral spinal fluid (CSF) rhinorrhea post-operatively that required repair. Nine days following the initial operation, the patient experienced a rapid decline in the level of consciousness. An urgent computed tomography (CT) head was ordered (Figure 2). The CT scan revealed extensive pneumocephalus in the suprasellar cistern, third ventricle, and lateral ventricles. He was started on high flow oxygen and taken for external ventricular drain (EVD) placement.

Figure 1: (A) Pre- and (B) post-operative imaging of the patient’s craniopharyngioma. Sagittal and coronal pituitary views with T2 and T1 post-gadolinium sequences are included.

Figure 2: (A) Axial and (B) coronal CT images showing extensive tension pneumoventricle.

Operatively, placement of the drain was confirmed using attachment of the EVD to a syringe filled with saline, and bubbling of air was seen. Multiple passes were required. The patient tolerated the procedure well and improved post-operatively. He required two nasal septal flap operations with fat grafting and fascia lata. He was discharged 2 weeks after his second repair.

Tension pneumoventricle is rare. ^{Reference Radhziah, Lee and Ng1} Tension pneumoventricle results in intracranial hypertension within the ventricle and can result in rapid deterioration in the level of consciousness. ^{Reference Armocida2} Two mechanisms have been proposed: (1) Dandy’s ball valve mechanism and (2) Horowitz’s inverted soda bottle mechanism. ^{Reference Perrin and Bernstein3} In our case, given the CSF leak and extensive cisternal air, the inverted soda bottle mechanism seems to explain the finding, with the floor of the third ventricle being the entry point. This type of surgery should be considered high risk due to disruption of the basal cisterns near the floor of the third ventricle. Tension pneumoventricle has been seen after trauma, ^{Reference Tsai, Cheng, Tsai and Tsai4} spontaneously with suprasellar lesions, ^{Reference Ghimire, Shapey, Bodi, Connor, Thomas and Barkas5,Reference Lai and Lai6} skull base surgery ^{Reference Gonçalves, Nunes, Melo, Guimarães, Klescoski and Landeiro7,Reference Gupta, Rath, Mahajan, Dube and Sharma8} and shunt placement. ^{Reference Perrin and Bernstein3,Reference Krishnan, Manuel and Vasudevan9}

Identifying the tension pneumoventricle is crucial to allow for treatment. The mainstay of treatment is ventriculostomy. Perrin et al. also described a technique of gentle rotation of the patient’s head to displace air to the least dependent region with irrigation of fluid. ^{Reference Perrin and Bernstein3} As this condition has a high mortality associated with it at around 10%, a high degree of clinical and radiographic suspicion must be exercised to ensure correct treatment. ^{Reference Armocida2}

We had some difficulty with the placement of the drain due to the absence of CSF flow. We eventually attached a blunt-ended syringe filled with saline to the end of the tubing and were able to visualize bubbling of air after placement of the EVD.

The patient improved dramatically after placement of the ventriculostomy tube. His GCS returned to 15, and he was successfully weaned off of his EVD following two trans-sphenoidal skull base repairs.

Tension pneumoventricle is a rare condition that may occur secondary to transsphenoidal surgery. Ventriculostomy is the mainstay of treatment.

Our key points in publication of this case are that tension pneumoventricle should be suspected in patients with rapid decline following transsphenoidal pituitary surgery and that drain placement may be assisted using a saline-filled syringe to check for bubbling of air.