Visual discrimination after anterior temporal lobectomy in humans

OBJECTIVE: To determine whether right anterior temporal lobectomy (RTL) results in perceptual deficits, and whether the perception of particular stimulus features (i.e., shape, motion, color) is affected differentially. BACKGROUND: RTL results in abnormal visual discrimination, recognition, and recall of pictorial material that cannot be easily specified verbally, such as designs and faces. It is unclear whether stimuli must be conceptually meaningful to elicit perceptual deficits. METHODS: Tests were constructed to assess a wide spectrum of basic visual discrimination abilities with simple, meaningless stimuli. The performance of nine patients who underwent left temporal lobectomy (LTL) and nine patients who underwent RTL were compared with that of normal control individuals. The mean excision size along lateral cortex was 3.7 cm for the LTL group and 5.6 cm for the RTL group; mean mesial excision size was 5.2 cm for LTL and 4.6 cm for RTL. RESULTS: Basic visual discrimination capacities were demonstrated to be essentially intact after LTL and RTL, except for a mild loss of blue color discrimination after RTL. CONCLUSIONS: There is little evidence that RTL produces perceptual impairments limited to the domain of pattern perception, or generalizable to nonmeaningful stimuli. The perceptual loss after RTL may be largely restricted to extraction of meaning, and related to the disruption of the circuits that connect the outcome of visual analysis to previously stored semantic information.     

Olfactory memory in patients with anterior temporal lobectomy.

Right and left temporal lobectomy patients, matched in age and intelligence, made more errors in odor recall than a control group. Patients with right temporal lobe excisions recalled significantly fewer odors correctly than patients with left temporal lobe excisions. Olfactory memory scores were not related to other memory deficits associated with left or right temporal lobe dysfunction or to intelligence or lesion size. However, in patients with right temporal lobectomy, percent of odors recalled correctly correlated positively with a general memory index. The findings presented are consistent with previous reports that the right temporal lobe is more involved with nonverbal memory than the left temporal lobe.     

Specificity of memory deficits after right or left temporal lobectomy

An impairment of verbal memory has consistently been associated with resection of the left dominant temporal lobe, whereas non-verbal memory deficits have been less reliably observed following resection of the right temporal lobe. Such a dissociation may be due to material-specific differences of processing between verbal and non-verbal information. Alternatively, the influence of the left and right limbic structures may vary according to the stage of memory processing. The aim of the study was to test these hypotheses by comparing verbal and spatial learning in patients with left or right temporal lobe resection for intractable epilepsy, using verbal and visuospatial memory tasks with the same design: control of encoding, multiple trial learning, free and cued recall, short and long delays. The results showed: (1) a similar pattern of learning and recall in the two groups; (2) a higher performance in spatial learning for patients with left temporal lobe resection and in verbal learning for patients with right temporal lobe resection; (3) material-specific effects characterized by a higher sensitivity to cues in the verbal domain and a better retention of information during delays in the spatial domain. These results suggest parallel processing of the two temporal lobes at the various memory stages, rather than an interaction between memory stage and side of the lesion similar to that already proposed for the frontal lobes. They also confirm a double dissociation between verbal/spatial information processing and side of temporal lobe resection.     

Predictors of postoperative memory function after left anterior temporal lobectomy

Patients who undergo left anterior temporal lobectomy (ATL) for intractable epilepsy are at risk of postoperative memory decline. This study attempts to identify the best predictors of memory after ATL using preoperative tests. Thirty-two consecutive patients who underwent left ATL with preoperative and postoperative neuropsychological testing were retrospectively identified. The following independent variables were analyzed by multiple regression: age of onset of seizures, age of temporal lobe damage, gender, MRI results, preoperative memory testing, and intracarotid amytal procedure (IAP) results. Neuropsychological measures of verbal and nonverbal memory served as dependent variables. Male gender (P<0.005), failing the IAP with both left and right hemispheres (P<0.001), and higher logical memory (LM) scores preoperatively (P<0.001) were associated with greater declines in LM after surgery. Our data demonstrate that the IAP predicts postoperative memory independent of other factors known to affect memory after left ATL.     

Crossed aphasia after right anterior temporal lobectomy. A case report

The occurrence of crossed aphasia as a complication after temporal lobe epilepsy surgery is extremely rare. We report the case of a 47-year-old right-handed patient with drug-resistant mesial temporal lobe epilepsy (MTLE) who developed a transitory aphasic syndrome after a right temporal anterior lobectomy. This syndrome was characterized by anomia, poor verbal fluency, verbal perseveration, and verbal comprehension difficulties. He also showed writing difficulties, reading substitutions, and calculation task errors. The patient was regularly assessed with language tasks, and showed a spontaneous and progressive recovery of his symptoms, with remaining naming difficulties. We discuss the role that epileptogenic zone could play in cortical reorganization of the language systems.     

Nonverbal memory functioning following right anterior temporal lobectomy: a meta-analytic review.

PURPOSE: Studies investigating nonverbal memory functioning following right anterior temporal lobectomy (RATL) in patients with intractable temporal lobe epilepsy have resulted in conflicting findings, as nonverbal memory deficits have been reported for some, but not all patients. To examine the association between nonverbal memory deficits and RATL, the present study employed meta-analytic principles in a quantitative review of the literature. METHODS: Thirteen studies, reporting pre- and postoperative nonverbal memory performance for a total of 324 RATL patients, were identified. Effect sizes were calculated to measure the extent of nonverbal memory deficit in patients following RATL. Additionally, effect sizes for primary studies comprising a common dependent variable were combined using standard meta-analytic procedures. RESULTS: Of the 22 dependent variables utilized to assess nonverbal memory, 14 indicated postoperative declines in functioning while 8 demonstrated postoperative improvements in performance. All resultant effect sizes were relatively small. Mean effect sizes calculated for dependent variables used in multiple studies identified the Warrington Recognition Memory Test for Faces as the only nonverbal memory measure which produced consistent results. CONCLUSIONS: Overall, the collective findings demonstrate the inability of the current research to provide any consistent evidence as to the nature of nonverbal memory outcome following RATL. Problems with nonverbal memory measures are discussed and suggestions for future research are proposed.     

The functional anatomy of non-verbal (pitch memory) function in left and right anterior temporal lobectomy patients

An fMRI pitch memory task was administered to left and right anterior temporal lobectomy (ATL) patients. The goal was to verify the neuroanatomical correlates of non-verbal memory, and to determine if pitch memory tasks can identify cognitive risk prior to ATL. The data showed that the bilateral posterior superior temporal lobes implement pitch memory in both ATL patients and NCs (normal controls), indicating that the task can be accomplished with either anterior temporal lobe resected. NCs activate the posterior temporal lobes more strongly than ATL patients during highly accurate performance. In contrast, both ATL groups activate the anterior cingulate in association with accuracy. While our data clarifies the functional neuroanatomy of pitch memory, it also indicates that such tasks do not serve well to lateralize and functionally map potentially “at risk” non-verbal memory skills prior to ATL.     

The Wada memory test and prediction of outcome after anterior temporal lobectomy

We reviewed the records of 77 Chinese-speaking adult patients to investigate the relationship between the Wada memory test and outcomes after anterior temporal lobectomy (ATL). The ipsilateral memory scores, contralateral memory scores and Wada asymmetry index (WAI) were calculated to evaluate their relationships with seizure and cognitive outcomes. The seizure outcomes did not correlate with the unilateral memory scores or the WAI. Patients who had a smaller WAI tended to have a post-operative decline in verbal intelligence quotient (VIQ) (odds ratio: 13.54, 95% confidence interval: 1.17–156.11, p = 0.037). The seven patients who failed the Wada memory test after ipsilateral injection had a higher percentage of VIQ deterioration than the 70 who passed (p = 0.039). However, no patient displayed global amnesia after surgery. The Wada memory test was a predictor for post-operative VIQ changes in our study. Patients who failed the Wada memory test still benefitted from the ATL and showed good seizure outcomes.     

Memory outcome after left anterior temporal lobectomy in patients with expected and reversed Wada memory asymmetry scores

PURPOSE: The ideal candidate for anterior temporal lobectomy surgery shows a Wada memory asymmetry (WMA) score characterized by better memory performance in the hemisphere contralateral to the seizure focus relative to the ipsilateral (surgical) hemisphere. However, some surgical candidates show a reversed WMA or better Wada memory performance in the hemisphere of surgical interest relative to the hemisphere contralateral to the seizure focus. To date, no data are available contrasting memory and seizure outcome for these two Wada groups. The present study compared memory and seizure outcome after left anterior temporal lobectomy (L-ATL) in patients showing expected and reversed WMA scores, and also examined the relationship of the individual hemisphere Wada memory scores for predicting verbal memory outcome after L-ATL. METHODS: We compared 6-month postoperative verbal memory change scores and seizure outcome in L-ATL patients with either an expected (n=12) or reversed WMA (n=9) pattern on Wada memory testing. RESULTS: L-ATL patients showing a reversed WMA score had a poorer verbal memory outcome and poorer seizure control after surgery compared with patients showing a WMA score in the expected direction. CONCLUSIONS: L-ATL patients with a reversed WMA score have a greater risk for memory morbidity and poorer seizure outcome than do patients with a WMA score in the expected direction. The WMA score was the best predictor of memory outcome after L-ATL. When the WMA score is not considered, both individual Wada hemisphere scores (contralateral and ipsilateral) provided significant and independent contribution to predicting postoperative verbal memory functioning. These findings are discussed in the context of the functional reserve and hippocampal adequacy models of memory change after temporal lobectomy.     

Visual outcomes after anterior temporal lobectomy and transsylvian selective amygdalohippocampectomy: A quantitative comparison of clinical and diffusion data

Objective

Anterior temporal lobectomy (ATL) and transsylvian selective amygdalohippocampectomy (tsSAHE) are effective treatment strategies for intractable temporal lobe epilepsy but may cause visual field deficits (VFDs) by damaging the optic radiation (OpR). Due to the OpR's considerable variability and because it is indistinguishable from surrounding tissue without further technical guidance, it is highly vulnerable to iatrogenic injury. This imaging study uses a multimodal approach to assess visual outcomes after epilepsy surgery.

Methods

We studied 62 patients who underwent ATL (n = 32) or tsSAHE (n = 30). Analysis of visual outcomes was conducted in four steps, including the assessment of (1) perimetry outcome (VFD incidence/extent, n = 44/40), (2) volumetric OpR tractography damage (n = 55), and the (3) relation of volumetric OpR tractography damage and perimetry outcome (n = 35). Furthermore, (4) fixel-based analysis (FBA) was performed to assess micro- and macrostructural changes within the OpR following surgery (n = 36).

Results

Altogether, 56% of all patients had postoperative VFDs (78.9% after ATL, 36.36% after tsSAHE, p = .011). VFDs and OpR tractography damage tended to be more severe within the ATL group (ATL vs. tsSAHE, integrity of contralateral upper quadrant: 65% vs. 97%, p = .002; OpR tractography damage: 69.2 mm³ vs. 3.8 mm³, p = .002). Volumetric OpR tractography damage could reliably predict VFD incidence (86% sensitivity, 78% specificity) and could significantly explain VFD extent (R² = .47, p = .0001). FBA revealed a more widespread decline of fibre cross-section within the ATL group.

Significance

In the context of controversial visual outcomes following epilepsy surgery, this study provides clinical as well as neuroimaging evidence for a higher risk and greater severity of postoperative VFDs after ATL compared to tsSAHE. Volumetric OpR tractography damage is a feasible parameter to reliably predict this morbidity in both treatment groups and may ultimately support personalized planning of surgical candidates. Advanced diffusion analysis tools such as FBA offer a structural explanation of surgically induced visual pathway damage, allowing noninvasive quantification and visualization of micro- and macrostructural tract affection.     

Visual field deficits in conventional anterior temporal lobectomy versus amygdalohippocampectomy

OBJECTIVE: To evaluate and identify the incidence of visual field defects (VFD) after anterior temporal lobectomy (ATL) versus amygdalohippocampectomy (AH). VFD occur frequently after ATL and are usually superotemporal quadrantanopias. Little is known about the incidence of VFD after AH and this surgical method offers the possibility of a seizure-free survival without visual loss. METHODS: Patients with similar characteristics were examined. All patients had intractable seizures and mesial temporal sclerosis, small tumors localized to only the uncus, amygdala, or hippocampus, or no known pathology. Postoperative kinetic field testing using the I4e isopter on a Goldmann perimeter was performed 30 days or more after surgery. RESULTS: Of 29 patients examined, 14 underwent AH and 15 had ATL. Four of 14 AH patients (28%) had a VFD at 10 degrees from center and 11/14 (78%) had VFD at 40 degrees. One of 15 ATL patients (7%) had a VFD at 10 degrees from center and 11/15 (73%) had VFD at 40 degrees. There was no significant difference between surgery types. CONCLUSIONS: AH in this study was associated with a significant number of VFD. No significant difference was found between the frequency of VFD produced from AH and ATL. The mechanism of injury is due to direct trauma to the optic radiations while accessing the mesial temporal structures. Because all patients in the study were asymptomatic for VFD, it remains to be determined whether these VFD are clinically significant.     

Material-specific memory changes after anterior temporal lobectomy as predicted by the intracarotid amobarbital test

Summary: Purpose: The intracarotid amobarbital test (IAT) has been shown to predict verbal memory changes after anterior temporal lobectomy (ATL). Seeking to extend these findings, we examined two questions: (a) What is the relationship between material‐specific aspects of IAT memory and material‐specific memory changes after ATL? and (b) Which IAT memory score(s) optimally predict memory changes after surgery, the memory score after injection ipsilateral to the seizure focus, the memory score after injection contralateral to the seizure focus, or the IAT asymmetry score, comprising the ipsilateral minus contralateral injection scores? Methods: Seventy left hemisphere language‐dominant patients undergoing ATL for treatment of medically refractory seizures were administered a verbal and visuospatial recognition memory test before surgery and 3 weeks after surgery. IAT memory recognition scores for words and designs were used to predict verbal and visuospatial memory changes after surgery. Results: After surgery, left ATL patients declined in verbal memory, whereas right ATL patients declined in visuospatial memory. IAT total recognition memory scores (collapsed across all types of materials) and IAT word memory scores were associated with postoperative verbal memory decline. This relationship was significant for the IAT ipsilateral injection memory scores and the IAT hemispheric asymmetry scores. IAT memory performances were not related to visuospatial memory changes. Conclusions: Results indicate IAT memory measures to be related to postoperative verbal, but not visuospatial, memory change. A specific relationship was found between postoperative verbal memory change and IAT verbal memory after injection ipsilateral to the seizure focus, when relying primarily on the contralateral hemisphere. This finding is consistent with the functional reserve model of memory change in ATL.     

Reliability and normative data for the Benton Visual Form Discrimination Test

Visuoperceptual disorders are a common consequence of brain disease. The Visual Form Discrimination Test is a task designed to assess the ability to make fine visual discriminations. Although its validity to assess the visuoperceptual impairments in patients with different neurological conditions has been well established, the normative data base for the test has remained small. The clinical use of the test has been limited by the scanty normative data available. Thus, with the aim of assisting the clinicians in interpreting more accurately the performances of their patients we investigated the test-retest reliability of the Benton's VFDT and also provide normative data obtained on a sample of 397 healthy individuals.     

Visual memory deficits after damage to the anterior commissure and right fornix.

A 47-year-old right-handed woman suffered an accidental dural perforation in the course of intranasal drainage of a right-sided sphenoid mucocele. Radiological examination revealed a small hematoma involving the anterior commissure, the right foramen of Monro, and the right fornix, resulting in severe anterograde amnesia for visual stimuli. Visual retention disturbances were manifested by a loss of the ability to conjure up new visual images, loss of topographical memory, and the cessation of dreaming. Dissociation was striking between severe deficits on tests exploring anterograde visual memory, revisualization, visuospatial organization, construction abilities, and normal or mildly impaired performance on tests implying verbal material and verbal memory. In agreement with experimental findings, it is postulated that combined damage to the anterior commissure and fornix on the right side could cause severe deficits in visual retention in humans.     

Preoperative FDG-PET temporal lobe hypometabolism and verbal memory after temporal lobectomy

OBJECTIVE: To examine the relationship of preoperative fluorodeoxyglucose (FDG)-PET asymmetry in temporal lobe metabolism and memory outcome after anterior temporal lobectomy (ATL). METHODS: In a university-based epilepsy surgery center, 60 ATL patients (27 left, 33 right) were divided into two groups: no/mild (n = 21) or moderate/ severe (n = 39) asymmetry in temporal lobe hypometabolism as determined by FDG-PET. All patients were nonretarded, at least 18 years of age, left-hemisphere speech dominant, without MRI abnormalities other than hippocampal atrophy, and with unilateral temporal lobe origin of intractable complex partial seizures. Neuropsychological measures of intelligence and verbal and visual memory function were assessed preoperatively and 6 months postoperatively. RESULTS: Left ATL patients with no/mild asymmetry in FDG-PET temporal lobe metabolism exhibited significantly greater verbal memory decline compared with left ATL patients with moderate/severe hypometabolism. There was no significant relationship between PET asymmetry and pre- to postsurgical IQ change. No significant relationship was observed between extent of PET hypometabolism and memory outcome for right ATL patients. CONCLUSIONS: FDG-PET asymmetry can be added to the preoperative clinical markers that appear useful in predicting verbal memory decline after left ATL.     

Risk to verbal memory following anterior temporal lobectomy in patients with severe left-sided hippocampal sclerosis

BACKGROUND: Previous investigations indicate low risk for memory loss following anterior temporal lobectomy (ATL) in patients with severe hippocampal sclerosis (HS) compared with patients with mild HS. However, these conclusions have been established primarily with group-level analyses. OBJECTIVE: To investigate individual base rate risk for verbal memory loss following ATL in patients who have pathologically verified mild, moderate, or severe HS. PATIENTS AND METHODS: One hundred fifteen patients with unilateral temporal lobe epilepsy (68 with left-sided and 47 with right-sided epilepsy) were included. Acquisition, retrieval, and recognition components of verbal memory, as measured by the California Verbal Learning Test, were assessed before and after ATL. Postoperatively, the degree of neuronal loss and reactive gliosis of the hippocampus was assessed via a 3-tiered rating system establishing mild, moderate, and severe pathologic features. Patients with preoperative magnetic resonance imaging-based evidence of lesions outside the mesial temporal area (side of surgical resection) were excluded. RESULTS: Neither seizure laterality nor severity of HS was associated with preoperative verbal memory performance. Postoperatively, the left-sided ATL group demonstrated significant decline across the acquisition (P<.01), retrival (P<.001), and recognition (P<.001) verbal memory components compared with the right-sided ATL group. Patients who underwent left-sided ATL and had mild HS displayed the largest magnitude and percentage proportion of postoperative decline across all verbal memory components. However, 28 (48%) of the 58 patients who underwent left-sided ATL and who had moderate and severe HS displayed statistically reliable declines on retrieval aspects of verbal memory. Most patients undergoing right-sided ATL, regardless of the extent of hippocampal pathologic features, displayed no postoperative memory change. CONCLUSIONS: Substantial individual heterogeneity of memory outcome exists across groups of patients undergoing ATL, with various degrees of pathologically verified HS. Patients undergoing left-sided ATL who have mild HS seem at greatest risk for broad-spectrum verbal memory decline. However, when examining outcome on a patient-by-patient basis, many patients undergoing left-sided ATL who have moderate to severe HS were also vulnerable to verbal memory loss. This risk seems selective to a retrieval-based aspect of verbal memory.     

难治性颞叶癫痫术后生活质量的评估

目的调查药物难治性颞叶癫痫术后患者生活质量的改善情况,评估手术对该类患者生活质量的影响。方法将自理能力、学习能力、工作能力、经济收入四个指标作为生活质量的评定标准,对比168例药物难治性颞叶癫痫患者手术前后生活质量的变化,并进行统计学分析。结果 168例药物难治性颞叶癫痫患者经过严格的术前评估均行前颞叶切除,随访1-3年,术后生活质量较术前明显改善,有统计学意义。结论药物难治性颞叶癫痫患者术后生活质量明显改善,手术显示出良好的性价比,有手术指证的患者应积极手术治疗。     

Memory outcome 2 years after anterior temporal lobectomy in patients with drug-resistant epilepsy

PURPOSE: Memory decline is often observed after anterior temporal lobectomy (ATL), particularly in patients with dominant hemisphere resections. However, the follow-up length has been 1 year or less in most studies. Our aims were to examine postoperative memory changes over a longer period and to identify baseline demographic and clinical predictors of memory outcome. METHODS: We administered material-specific memory tests at baseline, and 1 and 2 years after surgery to 82 consecutive right-handed patients (52% males) who underwent ATL for drug-resistant temporal lobe epilepsy (TLE) (35 left, 47 right) after a non-invasive presurgical protocol. Repeated measures multivariate analysis of variance (RM-MANOVA) was used to examine the relationship between changes in memory tests scores over time and side of TLE and pathology. Also, standardized residual change scores were calculated for each memory test and entered in multiple linear regression models aimed at identifying baseline predictors of better memory outcome. RESULTS: RM-MANOVA revealed a significant change in memory test scores over time, with an interaction between time and side of surgery, as 2 years after surgery patients with RTLE were improved while patients with LTLE were not worse as compared with baseline. Pathology was not associated with changes in memory scores. In multiple regression analysis, significant associations were found between right TLE and greater improvement in verbal memory, younger age and greater improvement in visuospatial memory, and male gender and greater improvement in both verbal and visuospatial memory. CONCLUSIONS: Our results suggest that the long-term memory outcome of TLE patients undergoing ATL without invasive presurgical assessment may be good in most cases not only for right-sided but also for left-sided resections.     

Evaluating the contributions of state-of-the-art assessment techniques to predicting memory outcome after unilateral anterior temporal lobectomy

PURPOSE: Although anterior temporal lobectomy (ATL) is an effective treatment for many patients with medically refractory temporal lobe epilepsy (TLE), one risk associated with this procedure is postsurgical decline in memory. A substantial number of past studies examined factors that predict memory decline after surgery, but few have investigated multiple predictors simultaneously or considered measures that are currently in use. METHODS: This study compared the relative contributions made by presurgical neuropsychological test scores, MRI-based hippocampal volumetric analysis, and Wada test results to predicting memory outcome after ATL in a group of 87 patients. RESULTS: Logistic regression analyses indicated that noninvasive procedures (neuropsychological testing and MRI) made significant contributions to improving the prediction of memory outcome in this sample. The results from the Wada procedure did not significantly improve prediction once these other factors were considered. The only exception was in predicting memory for visual information after a delay, in which Wada results improved prediction accuracy from 78% to 81%. CONCLUSIONS: Current neuropsychological tests and MRI volumetric measures predict changes in verbal and visual memory after ATL. The relatively small change in correct classification rates when Wada memory scores are considered calls into question the benefits of using Wada test results to predict memory outcome when the results of noninvasive procedures are available.