Nonconvulsive seizures in patients presenting with altered mental status: an evidence-based review.

Definitive diagnosis of nonconvulsive seizures (NCS) can be made only by electroencephalography, and delay in diagnosis can increase morbidity, resource utilization, and length of hospitalization. We performed an evidence-based literature review to estimate the prevalence of NCS in patients with altered mental status (AMS) of unknown cause. PUBMED, EMBASE, the Cochrane Library, and other resources were searched for studies that included AMS and seizure as topics. The resulting 276 articles were screened for predetermined inclusion and exclusion criteria, leaving 5 studies enrolling 478 patients for review. The prevalence of NCS in patients with AMS ranged from 8 to 30% (overall prevalence of 21.5%, 95% CI: 18-25%), suggesting that the prevalence of NCS is sufficiently high to consider routine use of urgent electroencephalography in such patients. However, methodological weaknesses limit the generalizability of the results. A large, prospective study enrolling and screening for NCS in all patients who present with acute AMS is needed.