NONCONVULSIVE STATUS EPILEPTICUS IN OLDER PEOPLE: A DIAGNOSTIC CHALLENGE AND A TREATABLE CONDITION

Abstract

To the Editor: Lacking the typical phenotypic features of seizures and the adverse systemic consequences of prolonged convulsions, nonconvulsive status epilepticus (NCSE) was incorrectly assumed not to cause neuronal injury.1 Unfortunately, NCSE is associated with morbidity and mortality due to neuronal damage from abnormal electrical activity and its association with the acute neurological disorders that may precipitate it.2,3 This becomes more apparent in the geriatric population, in which impaired baseline mental status hampers diagnosis even further, and the brain parenchyma is more sensitive to prolonged abnormal electrical activity. To determine the prevalence, clinical features, and course of NCSE in the elderly population, an observational prospective study was conducted of all consecutive patients with acute unexplained change in mental,cognitive, or behavioral status or confusion that was the cause of hospitalization or had occurred during hospitalization in the Department of Geriatrics, Shaare Zedek Medical Center, over a 24-month period. Typical electroencephalogram (EEG) changes were required to establish the diagnosis of NCSE.4 Clinical improvement was defined as resumption of the previous (baseline) mental status and disappearance of epileptic activity on EEG. Within a 2-year period seven of 307 hospitalized patients, aged 73 and older, were diagnosed with NCSE (Table 1). Of the seven patients (4 women and 3 men, aged 73–90, mean age 82.7), only one had a previous history of epilepsy; three had renal insufficiency. All patients presented with acute altered mental state: confusion, stupor or coma, without concomitant clinical convulsive activity. In three patients, the presenting symptom was refusal to eat. Time until diagnosis ranged from 1 to 5 days (mean 3 days). All seven patients had generalized NCSE on EEG that disappeared with intravenous diazepam injection (5–8 mg) in the five patients to whom it was given and in all patients on follow-up. None of the patients had focal status epilepticus on EEG. Patients were treated with an intravenous loading dose of phenytoin (800–1,000 mg) or valproic acid (20 mg/kg) followed by a maintenance dose. In six patients, clinical improvement was achieved within 1 to 4 days (mean 2.2 days). None of the medications that the patients were taking are known to cause seizures. In the patients with renal failure, the clinical and encephalographic improvement was chronologically related to the antiepileptic treatment and not to renal function improvement. One patient died of sepsis 19 days after the diagnosis of NCSE. All other six patients were discharged from the hospital after they regained their previous mental and neurological status. We describe seven elderly patients with generalized NCSE. Although the diagnosis was delayed in all, they improved after diagnosis and appropriate treatment. Several features characterize the present series: old age (6 of 7 patients aged ≥80), high incidence (2.3%) of NCSE,5,6 only one patient with a previous history of epilepsy (unlike in other series in which up to 50% of patients were known to suffer from a convulsive disorder),2,3,7 and a benign outcome. Impairment of baseline cognitive abilities and confusion was the presenting symptom in five of seven patients. The fact that NCSE in most of the patients occurred under medical conditions that can cause acute mental status change highlights the diagnostic difficulty and the important role of EEG (sometimes at least as important as imaging) in the evaluation of abrupt mental or behavioral changes in the elderly population. Although the outcome of NCSE is variable, mortality has been reported to reach 50% in critically ill patients,6,8 and in the geriatric age group, NCSE might cause permanent neurological damage.9 Whether the good outcome in our series can be attributed, in part, to the fact that, in all these patients, epileptic activity was generalized and not focal, remains speculative. In addition, because a systemic, metabolic, or infectious condition (renal insufficiency, sepsis, or hypothermia) could have triggered the NCSE in five of seven, the reversibility of these causes may account, in part, for the relatively benign outcome. Although intravenous treatment of seizures is considered to be associated with morbidity and mortality in older people because of hypotensive, cardiac depressant and sedative effects of antiepileptic drugs,10 our experience suggests that, with the appropriate indications and when taking the proper precautions, such therapy is well tolerated in elderly patients with NCSE.