Number processing in temporal lobe epilepsy

BACKGROUND: Specific cognitive impairments have been found in association with mesial temporal lobe epilepsy (TLE), such as deficits in declarative memory or verbal abilities. No attention has been paid so far to possible deficits in number processing. OBJECTIVE: To investigate deficits in number processing in patients with TLE. METHODS: Numerical abilities were assessed in 28 right handed patients with medically intractable unilateral TLE and in a control group. RESULTS: No differences between patients and controls were found in analogue number processing with Arabic input, in a comparison task, or in simple addition and simple subtraction; however, there were significant group differences in tasks with verbal input, in simple division, in complex mental calculation, in a semantic knowledge task, and in conceptual tasks. Only minor differences were found between patients with right and left TLE. CONCLUSIONS: While numerical deficits may be expected in patients with left sided TLE, it is open for discussion why patients with right sided TLE also show numerical deficits.