Verbal memory impairment after right temporal lobe surgery: role of contralateral damage as revealed by 1H magnetic resonance spectroscopy and T2 relaxometry.

We assessed performance on selected tests of verbal memory in 48 patients who had undergone either anterior temporal lobectomy or selective amygdalo-hippocampectomy for the relief of pharmacologically intractable epilepsy. We related performance both to the side of surgical excision and to the presence or absence of abnormalities in the contralateral, unoperated, temporal lobe, as revealed by proton magnetic resonance spectroscopy (1H MRS) or T2 relaxometry. There were abnormalities on the unoperated side detected by 1H MRS in 50% of the 34 patients who successfully underwent spectroscopy, and by T2 relaxometry in 33% of the complete series of 48 patients. There was no systematic relationship between seizure outcome and the presence or absence of abnormalities on the unoperated side. Verbal memory deficits were present in patients with left-sided excision, regardless of whether there were abnormalities on the unoperated side. The patients with right-sided excision also had verbal memory deficits, but only in the group with magnetic resonance abnormalities on the contralateral (ie, left) side and only on delayed recall. The study extends previous findings on the role of the temporal lobes in memory and highlights the role of these new magnetic resonance techniques in relating cognitive processes to brain structures.