Cognitive impairment in adults with epilepsy: The relationship between subjective and objective assessments of cognition.

AIM: This study aimed to assess the relationship between objective measures of cognition and subjective perception of cognitive functioning reported by patients with epilepsy and their caregivers.

METHODS: One hundred patients with epilepsy attending hospital neurology outpatient clinics and their caregivers were enrolled in this study. The EpiTrack (version 1) brief cognitive screening tool was used to measure objective impairment, the ABNAS questionnaire (A-B Neuropsychological Assessment Schedule) to assess subjective cognitive performance, and a version of the ABNAS designed to be completed by caregivers (C-ABNAS) to document caregivers' views. Patient anxiety and depression were measured using the Hospital Anxiety and Depression Scale (HADS) and considered as covariates. Patients with an uncertain diagnosis of epilepsy or likely severe comorbid mood or anxiety disorders were excluded.

RESULTS: Data from 82 patients were analyzed after exclusion of patients with uncertain diagnoses or likely severe comorbid mood or anxiety disorders. Fifty-nine (72%) had a degree of objective cognitive impairment. Fifty (84.7%) of these 59 patients had 'high' ABNAS scores concordant with the objective assessment, and 43 (72.9%) had high C-ABNAS scores matching the abnormalities detected by objective screening. Of the 23 (28%) patients without objective cognitive impairment, seven (30.4%) had concordantly low ABNAS scores, and 10 (43.4%) had concordantly low C-ABNAS scores. Patient memory impairment was more often reported by patients themselves than by caregivers (p=0.011). Carers were significantly more likely to rate patients as having impaired motor coordination than patients themselves. A small part of the variance of the EpiTrack score was predicted by the C-ABNAS. Objective cognitive performance did not predict ABNAS or C-ABNAS scores.

CONCLUSIONS: Self-report or caregiver report questionnaires identify patients with epilepsy and objective cognitive impairment more accurately than patients with intact cognition. Those without objective evidence of cognitive impairment may, nevertheless, perceive themselves as having memory dysfunction; it is these patients, therefore, who most require both subjective and objective assessments of cognition, including carers' assessments, in order to establish the nature of their symptoms. None of these assessment measures can be used as a reliable proxy for another, each contributes individually to a comprehensive assessment of cognition, and all must be used in conjunction with measures of mood and anxiety.