Background: Pneumoencephalus (PC) is the presence of intracranial air, its development following neuroaxial anesthesia is extremely rare and most cases due to epidural block have been associated with loss-of-resistance to air (LORA) technique. Seizures in the post-operative setting have multiple causes.
Case report: 60-year-old female, ASA III (class III obesity, hypertension, diabetes mellitus and lumbar spondylolisthesis) admitted electively for total knee replacement surgery. After 5 attempts a sequential anesthesia with the LORA technique was performed. The patient was sedated with midazolam (4mg) and was on spontaneous ventilation and hemodynamically stable throughout the peri-operative period. Post-operative analgesia was made with epidural morphine. Was discharged from the PACU after 5 hours without incidents. 13 hours after the anesthesia was intubated and ventilated by the emergency medical team after a generalized tonic-clonic seizure. PC was discovered on evaluation and there was cooperation from anesthesiology, ICU and neurosurgery The reevaluation revealed severe hypercapnia and respiratory acidosis. After acknowledgement that the patient was always asymptomatic and given the time lapse between the sequential anesthesia and the symptoms, the hypercapnia was admitted as a major cause. There was resolution of the respiratory acidosis and hypercapnia and the patient was uneventfully extubated. Afterwards, a history of obstructive sleep apnea (OSA) was recognized and the patient continued follow-up by pulmonology. Remained asymptomatic and was discharged home 8 days later. 
Discussion: The probable cause of the seizure was multifactorial with the OSA, sedation and opioid as major possibilities. Although the patient didn’t report any symptoms suggestive of PC and there were more probable causes for the seizure, the PC finding was incidental and induced a fixation error. 
References: Kozikowski, G. P. Cohen, S. P. (2004) Lumbar Puncture Associated with Pneumocephalus: Report of a Case. Anesth Analg 98:524–6
Chau, H. M. Mokhlesi, B. Chung, F. (2013) Obesity Hypoventilation Syndrome and Anesthesia. Sleep Med Clin. 8(1): 135–147.
Learning points: PC is very rare, even when using the LORA technique, usually has early symptoms and seizure is an infrequent sign. A multidisciplinary approach of post-operative complications allows for early recognition of its real causes and minimizes the fixation errors.

Pneumoencephalus and seizure after sequential anesthesia: cause or incidental finding - a case report