Hennric Jokeit

Language lateralization by Wada test and fMRI in 100 patients with epilepsy

Comparing the determination of language dominance using fMRI with results of the Wada test in 100 patients with different localization-related epilepsies, the authors found 91% concordance between both tests. The overall rate of false categorization by fMRI was 9%, ranging from 3% in left-sided temporal lobe epilepsy (TLE) to 25% in left-sided extratemporal epilepsy. Language fMRI might reduce the necessity of the Wada test for language lateralization, especially in TLE.

Long term effects of refractory temporal lobe epilepsy on cognitive abilities: a cross sectional study

OBJECTIVE Intractable epilepsy is related to various transient and chronic brain electric and neurochemical disturbances. There is increasing evidence that chronic epilepsy induces secondary neuronal metabolic and structural decline. However, there is no convincing evidence that the cognitive abilities of patients deteriorate with increasing duration of intractable epilepsy. METHODS To examine whether duration of refractory temporal lobe epilepsy (TLE) is related to generalised cognitive impairment, psychometric intelligence based on the full scale intelligence quotient (FSIQ, WAIS-R) was determined in 209 patients with unilateral TLE. For analyses of variance (ANOVA) patients were grouped into three categories: <15, 15–30, and >30 years of refractory TLE. RESULTS An ANOVA and a multiple regression analysis showed that duration of TLE affects FSIQ. Patients with >30 years of TLE performed worse than patients with 15 or 30 years of TLE. The factors side of seizure origin and type of lesion on MRI did not reach significance. A second ANOVA including education as factor showed that in patients with higher educational attainment, the mean FSIQ was stable for a longer duration of TLE than in less educated patients. Retesting 6 months after anterior temporal lobectomy seizure free patients (n=85 of 127) had an higher FSIQ but showed a similar duration effect before and after anterior temporal lobectomy. The variables age at epilepsy onset, education, frequency of interictal epileptiform discharges, frequency of habitual and generalised seizures, serum concentration of antiepileptic drugs, and polypharmacy were statistically controlled. CONCLUSIONS Psychometric intelligence of patients with a longer duration of refractory TLE were most severely impaired. Consequently, refractory TLE seems to be associated with slow but ongoing cognitive deterioration. It is assumed that epilepsy related noxious events and agents exhaust the compensatory capacity of brain functions. However, as in dementia and Alzheimer’s disease, higher educational attainment as an indicator of higher brain reserve might delay the cognitive decline.

Memory fMRI lateralizes temporal lobe epilepsy.

Background: The assessment of mesial temporal lobe (MTL) function is important for the diagnosis and treatment of temporal lobe epilepsy (TLE) and other brain diseases. Declarative memory depends on the integrity of the MTL region. Objective: To investigate hemispheric asymmetries of MTL activity in patients with symptomatic TLE. Methods: With use of blood oxygenation level-dependent fMRI, hemispheric asymmetries in MTL activation of 30 individual patients with refractory symptomatic TLE and 17 healthy control subjects were studied. Activation was induced by a task employing mental navigation and recall of landmarks based on the retrieval of individually familiar visuospatial knowledge. Results: The study demonstrated that the memory task used reliably activated MTL structures in individual control subjects and patients with refractory TLE including children, older subjects, and patients with low formal IQ. Interhemispheric differences in MTL activation lateralized the side of seizure onset in 90% of patients with symptomatic unilateral TLE. In contrast, healthy control subjects did not show a systematic asymmetry of MTL activation. Correlations between MTL activation and neuropsychological measures suggest that the fMRI-detectable MTL changes were specifically related to memory rather than to memory-independent visuospatial abilities. Conclusion: fMRI of memory-induced MTL activation lateralizes the side of seizure onset in patients with refractory symptomatic TLE and may provide complementary information for presurgical evaluation.

Functional organization of the brain with malformations of cortical development

We examined the localization of cerebral functions in 28 patients with focal epilepsy and malformations of cortical development (MCDs). Polymicrogyria occurred in nine, hemimegalencephaly in four, heterotopia in eight, and focal cortical dysplasia (FCD) in nine cases. We used simple (sensomotor, visual) or complex (language, memory) functional magnetic resonance imaging (fMRI) paradigms. Two thirds of MCDs were activated by simple fMRI paradigms, whereas they less frequently showed activity during complex cognitive fMRI paradigms. During simple paradigms, all disturbances of cortical organization (polymicrogyria, schizencephaly, and mild‐type FCD) showed activity, whereas other MCDs (disturbances of earlier steps of cortical development: hemimegalencephaly, Taylor‐type FCD, and heterotopia) showed activity in only 44% (p < 0.01). The association between the pathophysiology and morphology of MCDs confirms the recently proposed classification system. Both focal neurological signs (p < 0.05) and focal electroencephalogram slowing (p < 0.05) independently correlated with MCD inactivity, confirming that fMRI showed neuronal functions of MCDs. Conclusively, fMRI visualizes the MCD functions and their relationship to the eloquent cortex, providing useful information before epilepsy surgery. Surgery of cortical organization disturbances should be cautiously performed because these malformations may participate to some degree in brain functions. Ann Neurol 2003;53:759–767

Effects of chronic epilepsy on intellectual functions

Intractable epilepsy is related to various transient and chronic brain electric and neurochemical disturbances. There is increasing evidence that long-lasting chronic epilepsy may induce secondary neuronal loss and metabolic dysfunctions. Still a matter of controversy is, however, whether cognitive abilities of patients deteriorate with increasing duration of intractable epilepsy. We present results from two independent cross-sectional studies dealing with measures of global cognitive performance in two different ways. The first study investigated in 78 patients with refractory temporal lobe epilepsy (TLE) the influence of duration of epilepsy on the difference between an estimated measure of former or pre-morbid intelligence and the current performance in an intelligence test. The second study aimed at duration of epilepsy-dependent effects on current IQ measures of 209 patients with refractory TLE. Both studies showed that the duration of epilepsy contributes to the explanation of interindividual variability in IQ measures of adult TLE patients to a higher degree than age and age of epilepsy onset. Similar to several studies on hippocampal neuronal density, hippocampal volume, and glucose metabolism, the presented cross-sectional data demonstrate that a duration of chronic epilepsy exceeding two decades is associated with worse cognitive abilities. Consequently, refractory TLE seems to induce a very slow but ongoing cognitive deterioration. It is assumed that epilepsy-related noxious events and agents exhaust the compensatory capacity of brain functions. A high cognitive reserve capacity, however, might delay the onset of deterioration.

Functional MRI Predicts Memory Performance after Right Mesiotemporal Epilepsy Surgery

Summary:  Purpose: Anterior temporal lobe resection (ATR) is a treatment option in drug‐resistant epilepsy. An important risk of ATR is loss of memory because mesiotemporal structures contribute substantially to memory function. We investigated whether memory‐activated functional MRI (fMRI) can predict postoperative memory loss after anterior temporal lobectomy in right‐sided medial temporal lobe epilepsy (MTLE).

Amplitude envelope correlation detects coupling among incoherent brain signals.

&NA; Cognitive processing involves γ‐activation over broad cortical regions. Phase coupling of these activities has rarely been reported for areas far apart. Other forms of coupling are generally not detected by conventional measures. Here, we use amplitude envelope correlation (AEC), which can detect signal coupling without phase coherence, even among different frequencies. We apply it to subdural recordings from humans performing a visual delayed match‐to‐sample task and systematically compare it with spectral amplitude and coherence. The different measures often show divergent results. In particular, AEC reveals γ‐coupling completely missed by coherence. We argue that coherence and AEC are adapted to different cortical mechanisms of short‐ and long‐range interactions, respectively.

EEG predicts surgical outcome in lesional frontal lobe epilepsy

Background: Because of the relatively poor results of frontal lobe epilepsy (FLE) surgery, identification of prognostic factors for surgical outcome is of great importance. Methods: To identify predictive factors for FLE surgery, we analyzed the data of 61 patients (mean age at surgery 19.2) who had undergone presurgical evaluation and resective surgery in the frontal lobe. Postoperative follow-up ranged from 0.5 to 5 years (mean 1.78). Fifty-nine patients had MRI-detectable lesions. Histopathologic examination showed dysplasia (57.4%), tumor (16.4%), or other lesions (26.2%). Thirty postoperatively seizure-free patients were compared with 31 non–seizure-free patients with respect to clinical history, seizure semiology, EEG and neuroimaging data, resected area, and postoperative data including histopathology. Results: Three preoperative and two postoperative variables were related to poor outcome: generalized epileptiform discharges, generalized slowing, use of intracranial electrodes, incomplete resection detected by MRI, and postoperative epileptiform discharges. The only preoperative factor associated with seizure-free outcome was the absence of generalized EEG signs. Multivariate analysis showed that only the absence of generalized EEG signs predicts the outcome independently. Moreover, the occurrence of a somatosensory aura, secondarily generalized seizures, and negative MRI was identified as additional independent risk factors for poor surgical results. Conclusions: The absence of generalized EEG signs is the most predictive variable for a seizure-free outcome in FLE surgery. Furthermore, nonlesional MRI, somatosensory aura, and secondarily generalized seizures are risk factors for poor surgical results.

Individual prediction of change in delayed recall of prose passages after left-sided anterior temporal lobectomy

Prognostic variables for individual memory outcome after left anterior temporal lobectomy (ATL) were studied in 27 patients with refractory temporal lobe epilepsy. The difference between pre- and postoperative performance in the delayed recall of two prose passages (Story A and B) from the Wechsler Memory Scale served as measure of postoperative memory change. Fifteen independent clinical, neuropsychological, and electrophysiological variables were submitted to a multiple linear regression analysis. Preoperative immediate and delayed recall of story content and right hemisphere Wada memory performance for pictorial and verbal items explained very well postoperative memory changes in recall of Story B. Delayed recall of Story B, but not a Story A, had high concurrent validity to other measures of memory. Patients who became seizure-free did not differ in memory change from patients who continued to have seizures after ATL. The variables age at epilepsy onset and probable age at temporal lobe damage provided complementary information for individual prediction but with less effectiveness than Wada test data. Our model confirmed that good preoperative memory functioning and impaired right hemispheric Wada memory performance for pictorial items predict a high risk of memory loss after left ATL. The analyses demonstrate that the combination of independent measures delivers more information than Wada test performance or any other variable alone. The suggested function can be used routinely to estimate the individual severity of verbal episodic memory impairment that might occur after left-sided ATL and offers a rational basis for the counseling of patients.

Mesial Temporal Lobe Epilepsy Impairs Advanced Social Cognition

Summary:  Purpose: Although memory, language, and executive functions have been extensively studied in patients with mesial temporal lobe epilepsy (MTLE), investigations into advanced social cognitive abilities have been neglected. In the present study, we investigated the ability to detect social faux pas and studied possible mediating clinical and demographic variables in patients with MTLE compared with patients with an epilepsy not originating within the MTLE and healthy controls.