HIPPOCAMPAL CELL LOSS AND GLIOSIS - RELATIONSHIP TO PREOPERATIVE AND POSTOPERATIVE MEMORY FUNCTION

The authors examined the relationship between neuronal densities, glia l cell densities, and the glial cell/neuron ratio in the CA1 and CA4 h ippocampal subfields and preoperative and postoperative memory functio n in 47 patients who had undergone a temporal lobectomy (23 right, RTL ; 24 left, LTL) for the relief of medically intractable epilepsy. The LTL group performed more poorly than the RTL group on a list learning and story recall task, preoperatively and postoperatively. Both the RT L and LTL groups performed more poorly on the story recall task postop eratively. In the LTL group, neuronal densities in the CAL subfield we re significantly correlated with the preoperative scores on the immedi ate (r = 0.53, p < 0.01) and delayed (r = 0.53, p < 0.01) recall of th e story. There were no significant correlations in the LTL group betwe en the CA1 and CA4 cell counts and Verbal IQ or scores on a measure of naming ability. None of the cell density measures in the CA1 and CA4 subfields were significantly correlated with the preoperative neuropsy chological test scores in the RTL group. Postoperative decline in verb al recall was associated with the excision of a relatively intact left hippocampus, with high neuronal and low glial cell densities in the C A1 subfield. The excision of a relatively intact right hippocampus was also associated with a postoperative deterioration in verbal recall.