Verbal memory impairment resulting from hippocampal neuron loss among epileptic patients with structural lesions

Abstract

We recently demonstrated statistically significant correlations between presurgical memory impairment and hippocampal volumetric cell densities (in CA3 and the hilar area only) for patients with idiopathic left temporal lobe epilepsy who exhibited marked hippocampal neuron loss. In the present research we determine whether the same relationship exists for patients with structural lesions, in whom hippocampal neuron loss was minimal. Rank-order correlations of verbal memory test results (ie, Long Term Retrieval score of the verbal Selective Reminding Test, Percent Retention index of the Logical Memory subtest of the Wechsler Memory Scale) and hippocampal volumetric cell densities (subfields CA1, CA2, CA3, the hilar area, and the granule layer of area dentata) were computed for 22 patients with structural lesions and medically refractory epilepsy of temporal lobe onset (11 left, 11 right). There were statistically significant correlations between Long Term Retrieval and the volumetric cell density of CA1 (r = 0.62, p < 0.05) and between percent retention and the volumetric cell density of CA2 (r = 0.60, p < 0.05) for patients with left hemisphere lesions. No other correlations were found for patients with left or right temporal lobe lesions.

Correlation between calbindin expression in granule cells of the resected hippocampal dentate gyrus and verbal memory in temporal lobe epilepsy

“…In the literature, left HS was correlated with deficiency of verbal, right HS with impairment of visuo-spatial memory, and the severity of memory deficits was related to the degree of HS detected with MRI or 1 H MRS [41][42][43]. In addition, the degree of pyramidal cell loss in Ammon's horn and loss of hilar neurons and granule cells of the dentate gyrus correlated to memory impairments [44,45,[47][48][49]. In the present study, we show that not only neuronal loss but also a more subtle, morphological and neurochemical alteration, namely decreased CB expression in the granule cells of the dentate gyrus, is associated with a deficit in memory functions.…”

“…The severe neuronal loss, typical for HS, may also be responsible for memory impairments, as shown earlier [44][45][46][47][48][49]. Therefore, patients were separated into two groups by the etiology and MRI findings.…”

“…Proton magnetic resonance spectroscopy ( 1 H MRS), which is assumed to be suitable for providing information about neuronal loss and gliosis, revealed correlation between 1 H MRS values and verbal memory scores [43]. Postoperative histological studies showed that pyramidal cell loss in the removed hippocampal formation significantly correlated with preoperatively detected memory impairments of patients [44][45][46][47][48][49]. Loss of hilar neurons and granule cells as well as lower proliferative capacity of neuronal precursor stem cells of the subgranular layer of the dentate gyrus was correlated with impaired memory function [44,45,47,49,50].…”

Is the Right Amygdala Involved in Visuospatial Memory? Evidence from MRI Volumetric Measures

“…Following resection of their epileptogenic temporal lobes, cell densities in different areas of the hippocampus were determined and correlated with cognitive performances. Scores on verbal memory tests were found to correlate with the cell density in the left hippocampal areas CA1 [Rausch and Babb, 1993;Sass et al, 1995], CA2 [Sass et al, 1995] as well as CA3 and the hilar region [Sass et al, , 1990. These findings were further demonstrated to be specific to mnestic function since correlations could not be found between neurone densities and tests of confrontation naming or IQ [Rausch and Babb, 1993;Sass et al, 1992].…”

Circuits and systems in stress. II. Applications to neurobiology and treatment in posttraumatic stress disorder

“…On a biological level, memory impairments of this kind have been found to be attributable to hippocampal damage specifically and are correlated with hippocampal volumetric cell densities [Sass et al, 1990[Sass et al, , 1992[Sass et al, , 1995. In this series of studies, Sass et al demonstrated in patients with idiopathic left temporal lobe epilepsy statistically significant correlations between presurgical memory impairment (Long Term Retrieval and percent retention on the Wechsler Memory Scale) and hippocampal volumetric cell densities (in CA1, 2, and 3 areas), showing a structural-functional relationship between memory loss and hippocampal volume.…”