Longitudinal assessment of intellectual functioning following unilateral temporal lobectomy

Abstract

INTRODUCTIONAlthough evidence for the presence of lateralized cognitive deficits in man is not unequivocal(8), acute destructive lesions of the dominant cerebral hemisphere have been shown to produce selective verbal impairment while nondominant hemisphere lesions have been associated with visuospatial dysfunction", l a ) . Such differential patterns of psychological test performance have appeared more consistently in cases with lateralized posterior lesions @). Furthermore, the verbal deficits arising out of left hemisphere involvement have been more clearly measurable in the presence of aphasic disturbances ( I ) , although more incisive assessment procedures have revealed subtle verbal deficits without gross impairment of verbal functioning(5, 9, li, l6).Since many of these investigations have operationally defined the independent lateralization variable by sampling representative neurological groups, factors such as nature of the neuropathological process, interruption of function through cerebral edema or intracranial pressure, lesion-induced changes in vascular supply to other areas, and pre-existing diffuse cerebral deterioration have not been amenable to direct surveillance and control. As a consequence, these factors have probably been confounded with the lateralization variable to obscure higher order interactions among such dimensions and, in so doing, have served to produce seemingly contradictory findings("). On the other hand, systematic investigation of lateral hemispheric differences in intellectual function has been actualized through cognitive assessment before and after unilateral temporal lobectomy in the neurosurgical treatment of temporal lobe epilepsy. Since the epileptogenic lesions in such patients are typically rather static in nature and, thus, less complicated by such irrelevant variables, resection of the anterior temporal lobe has provided a basis for more precise determination of lateral differences in cerebral dysfunction. 9 , a general tendency toward higher subtest scores in patients with epileptogenic foci of predominantly right temporal lobe origin was observed preoperatively, especially on the verbal tests. One month postoperatively, their nondominant group showed an increased superiority on all subtests largely as a function of a verbal subtest decline in the dominant group. This finding led to the postulation of a dysphasic basis for the obtained result. By contrast, Milner(lO) reported a deficit on the Picture Arrangement subtest of the Wechsler-Bellevue Form I before and after unilateral temporal lobectomy, but she did not mention any differential deficit between the left and right temporal lobectomy groups. A similar defect in the sequential ordering of complex pictorial stimuli was found in a small group of cases with acutely destructive right as compared with the left anterior temporal lobe lesions(la). However, none of the previous pre-to postoperative comparisons were made over a significant time interval longitudinally so that transient operative effects might have b...

A selective and critical review of neuropsychological deficits and the frontal lobes

“…Again, no references are given to support this contention. It should be noted, however, that several investigators (Meier and French, 1966;Milner, 1954;Reitan, 1955a) have commented that impairment in the ability "to size up a social situation appropriately," as manifested by explicit results on instruments such as the Wechsler Picture Arrangement subtest and the McGill Picture Anomalies Test, is related to nonfrontal rather than frontal lesions.…”

Early and late cognitive changes following temporal lobe surgery for epilepsy

“…9,10 Of concern, one study reported that 2 to 5 years after RTL surgery there is an increasing deficit on a nonmemory perceptual analyses task, suggesting late decline on a task associated with the right hemisphere. 11 Studies of very long cognitive sequelae of surgery are even more rare, 12 with little information available as to the cognitive stability of temporal lobe surgical patients as they age.…”

Changes in Intelligence Following Temporal Lobectomy: Relationship to EEG Activity, Seizure Relief, and Pathology

“…Since surgical treatment of medically refractory epilepsy can be desirable in certain patients whose seizures are suspected to originate in a focal fashion (for review see, Purpura et al, 1975) and since intellectual status may change for better or worse following the operation (Meyer and Yates. 1955: Meier and French. 1966: Milner, 1975.…”