Isolated, Transient, Pneumocephalus-Induced Oculomotor Neuropathy after Microvascular Decompression of the Trigeminal Nerve

Background Pneumocephalus is a common radiographic finding after posterior fossa craniotomy. In contrast, cranial neuropathies related to pneumocephalus are extremely rare, with only a handful of previous reports. Case Description We present the rare case of a right partial oculomotor mononeuropathy occurring in a 26-year-old woman 4 hours after a microvascular decompression of her right trigeminal nerve. Postoperative imaging revealed pneumocephalus in the interpeduncular cisterns with an air bubble close to the cisternal segment of the right oculomotor nerve, trapped by a fetal right posterior cerebral artery. The patient was placed on 100% Fio₂ (fraction of inspired oxygen) and encouraged to remain in the Trendelenburg position. She was discharged with only modest improvement in her pupil-involved partial oculomotor palsy, but she improved over the course of clinical follow-up and her deficit had completely resolved at 6 months. Conclusions Cranial neuropathy secondary to pneumocephalus is a rare and usually self-limiting condition. Although high-concentration oxygen therapy hastens resolution of pneumocephalus, recovery from pneumocephalus-related neuropathies may take weeks to months. To properly treat pneumocephalus-induced cranial neuropathies, further studies into the mechanism of injury are needed.