Full-Length Original Research
Low prevalence but high specificity of material-specific memory impairment in epilepsy associated with hippocampal sclerosis
Article first published online: 23 AUG 2013
Wiley Periodicals, Inc. © 2013 International League Against Epilepsy
Volume 54, Issue 10, pages 1735–1742, October 2013
How to Cite
Epilepsia, 54(10):1735–1742, 2013
- Issue published online: 1 OCT 2013
- Article first published online: 23 AUG 2013
- Manuscript Accepted: 13 JUL 2013
- FAPESP. Grant Number: 2005/56464-9
- Mesial temporal sclerosis;
- Temporal lobe epilepsy;
Material-specific memory impairment is used as a lateralizing tool in the evaluation of temporal lobe epilepsy. Lateralizing ability of material-specific memory deficits in temporal lobe epilepsy remains controversial.
We studied memory impairment profiles of verbal and nonverbal memory deficits with eight memory subtests of four neuropsychological instruments (two verbal and two nonverbal) in 87 right-handed patients with epilepsy associated with unilateral mesial temporal sclerosis (MTS; 44 right – R, 43 left – L) and 42 controls, with an IQ >70, at least 8 years of education, and without comorbidities.
Selective verbal memory impairment was noted in 11 of 43 or 25.6% of left MTS cases, with 82.2% specificity, whereas selective nonverbal memory impairment was noted in 11 of 42 or 26.2% of right MTS cases, with 92% specificity. Nonlateralizing profiles of memory performance were seen in the remaining 65 of 87 patients. Approximately half (46/87 or 52.9%) of the patients had intact memory function in both modalities, equally distributed between patients with right MTS (23/44) and left MTS (23/43). Global impairment of both memory types was seen in 12 of 87 or 13.8% of patients, equally distributed between the two groups (7/43 left and 5/44 right).
Lateralizing profiles of selective verbal and nonverbal memory deficits are highly specific for left and right MTS, although infrequently encountered in our patients. Nonlateralizing profiles predominated in this population. These findings suggest hemispheric asymmetry memory function, with complex functional interaction of the hippocampi, and possible compensatory mechanisms in the setting of a unilateral lesion.