Atypical Presentation of Pneumocephalus Post Ventriculoperitoneal Shunt in a Patient With a History of Endoscopic Endonasal Skull Base Approach: A Case Report.

Pneumocephalus, commonly seen after trauma, surgical intervention, or meningitis, is rarely associated with ventriculoperitoneal shunt (VPS) procedures. We present a unique case of tension pneumocephalus in a 26-year-old female who experienced two distinct episodes of pneumocephalus. She presented with right-sided facial numbness, hearing loss, blurry vision, and gait disturbance. Magnetic resonance imaging (MRI) revealed a large extra-axial lesion at the right petrous apex extending to the middle cranial fossa. The patient underwent an extended endoscopic endonasal approach for tumor resection, and the pathological diagnosis revealed an epidermoid cyst. Postoperatively, she improved. However, she developed abducens nerve palsy followed by extensive pneumocephalus with intraventricular extension, necessitating skull base defect repair. Six weeks later, she presented with acute hydrocephalus secondary to meningitis from Klebsiella pneumoniae, confirmed by positive cerebrospinal fluid (CSF) cultures. She was treated with external ventricular drainage and antibiotic therapy, after which a VPS was inserted. Three days post-shunt insertion, the patient developed left-sided hemiparesis and swallowing dysfunction due to localized pneumocephalus within the tumor cavity compressing the brainstem. Following additional surgical intervention, her hemiparesis and other symptoms resolved. This case highlights the potential for tension pneumocephalus following ventriculoperitoneal shunt insertion for hydrocephalus. The siphon effects of CSF shunting can cause excessively negative intracranial pressure. Combined with a postoperative skull base defect, this can lead to air ingress through the defect (ball valve mechanism), causing pneumocephalus.