Nonconvulsive status epilepticus in the elderly: a case-control study.

BACKGROUND: Nonconvulsive status epilepticus (NCSE) is a usually underdiagnosed and potentially treatable cause of altered awareness in the elderly. To assess etiologies, associations with other medical problems, and prognosis of NCSE in a population aged >75 years we performed a nested case-control study.

METHODS: We retrospectively evaluated the clinical manifestations and EEG findings in 19 consecutive elderly patients (mean age 83.3 years) presenting with NCSE and compared them with 34 elderly patients (mean age 83.3 years) with altered mental status but without EEG evidence of NCSE. The variables compared included brain lesions on CT or MRI, number of concomitant chronic active diseases, previous neurological disorders, acute medical problems, the use and withdrawal of medications, and outcome. Statistical analysis was performed using chi-square test, t-test, Fisher's exact two-tailed test, and Wilcoxon rank sum test.

RESULTS: The etiology of NCSE was epilepsy in 2, acute medical disorders in 14, and a cryptogenic cause in 4. The NCSE group had a more frequent history of epilepsy, 35% versus 8.8% (p = 0.028); tramadol use, 31% versus 0% (p = 0.00151); longer hospitalization, 25 days versus 7 days (p = 0.0004); and unfavorable outcome, 50% versus 5.8% (p = 0.00031). No significant differences were found in the other variables. Unfavorable outcome was associated with a higher number of comorbidities (>2) and to a severely altered mental status.

CONCLUSIONS: NCSE is a serious cause of altered mental status in the elderly. Although its direct role in brain damage is controversial, elderly patients with NCSE have higher morbidity and worst prognosis than those with altered mental status without NCSE.