Postoperative nonconvulsive encephalopathic status: identification of a syndrome responsible for delayed progressive deterioration of neurological status after skull base surgery

Abstract

Object Over a 10-year period, the authors have observed a rare but recurring syndrome manifested by a delayed, postoperative, progressive decline in the level of consciousness to deep coma that is time-limited to several days with abrupt awakening. Extensive evaluation and workup demonstrated an abnormality on continuous electroencephalographic monitoring that implied nonconvulsive status epilepticus after the exclusion of structural, perfusion, infectious, or metabolic causes. This state has been very refractory to treatment with antiepileptic medication. In this article, the authors raise the awareness of this syndrome and its diagnosis, management, and outcome. Methods The authors reviewed the medical records of a cohort of 7 patients who exemplified this syndrome who were treated during the last 5 years. Results All 7 patients were women with a mean (± SD) age of 55 ± 15 years. The mean duration of surgery was 8.9 ± 1.8 hours. All patients had a stereotypical course of delayed progressive decline in their level of consciousness after surgery (average 3.3 ± 4.3 days) leading to deep coma. The unconscious state was time-limited, lasting on average 17.3 ± 13.7 days. Continuous electroencephalographic monitoring demonstrated a generalized abnormality with periodic discharges and abundant slow delta activity. A rather abrupt awakening occurred a few days after cessation of electrographic seizure activity. Structural, vascular, infectious, or metabolic causes were excluded based on an extensive workup. Conclusions In this study, the authors delineate and raise the awareness of an unusual syndrome. Recognition of this syndrome is important as a cause for delayed coma after surgery. The authors stress the need for respiratory, hemodynamic, and nutritional support for these patients until recovery. The origin of this syndrome remains enigmatic and is likely to be multifactorial with a prominent pharmacological role related to anesthetic agent or medication in a setting of craniotomy that is associated with alteration of the blood-brain barrier.