The ambulatory outpatient with electrographic SE

The wide range of clinical presentation of patients with the absence form of NCSE, from those with no clinical signs and normal appearance to those who are stuporous and barely responsive, is well documented (1; see Thomas et al., Chapter 7, this volume). It is the former group, estimated to account for 19% of cases of ASE (see Thomas et al., Chapter 7, this volume), in which there is often a long delay to diagnosis but in which cognitive deficits, often subtle, are found once the individuals are tested. These deficits may be eliminated over time as electrographic seizure discharges are suppressed, as the following case illustrates.

case 1 A 64-year-old man had sustained three episodes of generalized NCSE, the first two episodes 3 weeks apart and the last 7 years later. An EEG obtained during the third episode in December 1990 showed bilaterally synchronous 2- to 2.5-Hz spike-and-slow-wave discharges frontotemporally, occupying 33% of total EEG time (Figure 9.1). During the EEG recording the patient appeared “normal;” during a 52-second run of spike-and-slow-wave discharges he subtracted from 100 to 0 by 1 s, with two mistakes. Divalproex sodium (Depakote) was started in December 1990, and the percentage of spike-and-wave discharges per EEG decreased to 2%–4% from October 1992 to September 1994, during which time the patient continued to take divalproex sodium. His last EEG in 1996 showed less than 1% spike-and-slow-wave discharges. Neuropsychological testing over a 9-year period, from May 1987 to June 1996, showed a progressive, 23-point increase in full-scale IQ (from 102 to 125), with an increase in verbal IQ from 103 to 133. Frontal executive function deficits also normalized, and this coincided with a reduction in the amount of spike-and-slow-wave discharges on the EEG. The patient died in April 1999 at age 64; no further information regarding his death is available.

Figure 9.1.  

This ambulatory patient showed marked cognitive improvement as electrographic spike-and-slow-wave discharges were suppressed over a 9-year period. This EEG was obtained during the patient's third episode of NCSE, in which bilaterally synchronous, 2–2.5 Hz spike-and-slow-wave discharges were present frontotemporally, occupying 33% of total EEG time. The spike-and-slow-wave discharges lasted from 0.5 to 52 seconds; during the 52-second run of spike-and-slow-wave discharges the patient appeared “normal” and subtracted from 100 to 0 by 1 s, with two mistakes.

This case has been reported in detail (4) and illustrates the fact that ambulatory outpatients may have episodes of NCSE without clinical manifestations, so that an EEG is required to establish the diagnosis. Moreover, persistent cognitive impairment, or epileptiform encephalopathy, that is caused by but is not simply time-locked to seizure discharges may persist for years in the setting of frequent electrographic seizure discharges. This patient's history suggests that if spike-and-slow-wave discharges are substantially reduced or eliminated, substantial cognitive improvement can occur over a prolonged period of time. This observation requires confirmation by further studies of similar patients.