Abstracts

RATIONALE: Cognitive deficits attributable to seizures are an important marker of epilepsy severity. Patients with subtle deficits may be missed with routine testing, yet comprehensive testing is time consuming, expensive, and not always available. Tests that can rapidly assess cognitive functions yet are sensitive enough to detect subtle deficits, facilitate monitoring effectiveness of care while providing efficiencies in time and cost.
METHODS: We previously reported a group of patients with frequent frontal and frontotemporal subclinical electrographic discharges (SEDs) and deficits on formal cognitive testing. In this study, we focused on two tests routinely used to rapidly assess mental status (digit span and serial 7s) and monitored cognitive performance. Because frontally predominant SEDs might delay responses, prospective measurements included time to completion as well as accuracy on Serial 7s (not routinely done in formal cognitive testing). Qualitative techniques were used to analyze the data due to small sample size and varying numbers of samples/patient. Performance over time was compared with severity of SEDs (as a percentage of total time/EEG or as duration of bursts/EEG).
RESULTS: Responses were collected from 9 patients over intervals up to 13 years. [underline]Digit Span testing revealed[/underline]: 5/9 patients (56%) evidenced sustained improvement as SEDs abated (3/9 improved [gte]2 digits and 2/9 improved 1 digit); 1/9 improved but returned to baseline with recurrent SEDs; 3/9 tested only once. [underline]Performance on Serial 7s revealed[/underline]: 6/9 patients (67%) improved both accuracy and time to complete [italic]or[/italic] accuracy alone if time was not recorded. Of these, 4/6 patients[ssquote] performance followed SED severity. 1/9 (11%) failed a second test of serial 7s. 2/9 (22%) were tested only once. Substantial intra- and inter-patient differences in time to completion were noted (nearly 7 fold for one patient), which usually correlated with SED severity. [underline]Combined testing revealed[/underline]: Among patients with multiple tests, 3/6 patients (50%) improved both digit span and serial 7 accuracy (if time to completion was not tracked); 2/6 patients (33%) improved digit span and both serial 7 accuracy and time to completion; 1/6 patients improved digit span and serial 7 accuracy but correlation with SEDs wasn[ssquote]t possible due to long inter-test intervals.
CONCLUSIONS: 1) Peformance on digit span and serial 7s can reflect SED severity. 2) To the extent impaired attention reflects frontal dysfunction, these tests can be valuable [dsquote]bedside tools[dsquote] for assisting clinicians in monitoring effects of frontal SEDs. 3) Time to completion of serial 7s can add valuable insights into level of functioning not reflected by accuracy of response alone.