Peter F. Bladin

Preoperative MRI predicts outcome of temporal lobectomy: An actuarial analysis

we used actuarial methods to study outcome after temporal lobectomy in 135 consecutive patients classified into subgroups according to preoperative MRI findings. Sixty months after surgery, 69% of patients with foreign tissue lesions, 50% with hippocampal sclerosis, and 21% with normal MRIs had no postoperative seizures. An eventual seizure-free state of 2 years or more, whether the patient was seizure-free since surgery or not, was achieved by 80% of patients with foreign tissue lesions, 62% of those with hippocampal sclerosis, and 36% of those with normal MRIs. Outcome was worse in those with normal MRIs than in the other two groups. Early postoperative seizures with later remission (the “mming down” phenomenon) occurred in all groups. Late seizure recurrence was present only in the hippocampal sclerosis group. These data show that preoperative MRI is a useful predictor of outcome and that actuarial analysis provides insight into different longitudinal patterns of outcome in MRI subgroups. This information can now be used in preoperative counseling.

Hippocampal sclerosis can be reliably detected by magnetic resonance imaging

Two independent blinded observers reported the preoperative MRIs in a series of 81 consecutive patients with intractable temporal lobe epilepsy who were undergoing temporal lobectomy. We then compared the nature and lateralization of the MRI abnormalities with the pathologic diagnosis and the side of lobectomy. The MRI criteria of hippocampal sclerosis were an increased T2-weighted signal and the signals confinement to a unilaterally small hippocampus. Imaging was performed in coronal and axial planes, specially orientated along and perpendicular to the long axis of the hippocampal body. We found diagnostic MRI abnormalities in 25 of the 27 cases with pathologically proven hippocampal sclerosis (sensitivity 93%, specificity 86%). In addition, we detected all 13 foreign tissue lesions on MRI. Overall, we detected lateralized lesions on MRI that correctly predicted the side of the epileptogenic temporal lobe in 72 cases (89%), with 2 possible errors. A learning effect in appreciating the relatively subtle MRI changes of hippocampal sclerosis was apparent in our later cases, as shown by an improved correlation between the 2 observers. This study demonstrates that hippocampal sclerosis can be identified on MRI with a high degree of sensitivity and specificity.

Gelastic seizures and hypothalamic hamartomas Evaluation of patients undergoing chronic intracranial EEG monitoring and outcome of surgical treatment

We retrospectively studied 12 consecutive patients with gelastic seizures and hypothalamic hamartomas who, because of intractable epilepsy, underwent chronic intracranial EEG monitoring or epilepsy surgery. All patients had medically refractory seizures that included laughter as an ictal behavior (gelastic seizures). The hypothalamic hamartomas were identified with neuroimaging studies (12 of 12) and by pathologic verification (four of 12). Associated clinical features included behavioral disorders (n = 5), developmental delay (n = 4), and precocious puberty (n = 2). Interictal extracranial EEG predominantly showed bihemispheric epileptiform changes suggesting a secondary generalized epileptic disorder. Intracranial EEG recordings, performed in eight patients, indicated the apparent focal onset of seizure activity (anterior temporal lobe [n = 7] and frontal lobe [n = 1]). None of the seven patients who underwent a focal cortical resection, however, experienced a significant reduction in seizure tendency. An anterior corpus callosotomy, performed in two patients with symptomatic generalized epilepsy, resulted in a worthwhile reduction in drop attacks. Results of this study may modify the surgical strategies in patients with gelastic seizures and hypothalamic hamartomas.

Dystonia, clinical lateralization, and regional blood flow changes in temporal lobe seizures

We analyzed the lateralizing value of ictal dystonia and head-turning in temporal lobe epilepsy, and sought the biologic basis of these clinical signs by studying the regional changes in perfusion with ictal single-photon emission computed tomography (SPECT). We identified unilateral temporal lobe epilepsy in 40 of 42 patients undergoing evaluation for temporal lobe surgery, and with ictal SPECT all 40 showed striking hyperperfusion of the epileptogenic temporal lobe. Twenty-five of the 40 patients showed unilateral or predominantly unilateral upper limb dystonia, which was opposite the epileptic temporal lobe in all cases. Analysis of regional count ratios in cases with ictal dystonia, compared with those without, showed significant changes only in the basal ganglia. Specifically, we found that ictal dystonia was associated with a relative increase in perfusion of the basal ganglia opposite the dystonic limb. Although we found 26 cases with head-turning, the sign was of no lateralizing value, even when only those with major or “tonic” versions (n = 11) were analyzed. Slight increases in cortical blood flow on the side opposite the direction of version were associated with head-turning, irrespective of the side of seizure focus. In clinical practice, ictal SPECT is a highly accurate aid in the lateralization of temporal lobe foci, in addition to providing a new method to investigate the pathophysiology of clinical signs in focal seizures.

Patterns of postictal cerebral blood flow in temporal lobe epilepsy Qualitative and quantitative analysis

We used single-photon emission computed tomography (SPECT) to study postictal cerebral blood flow (CBF) in 51 patients with temporal lobe epilepsy. There were 78 seizures studied, 77 by early postictal injection of Tc-99m HMPAO (delay from seizure onset = 4.3 ± 4.5 min) and one by ictal injection. Increased focal temporal lobe uptake, predominantly confined to the anteromesial region, was present in 83% and declined rapidly over 5 minutes. Reduced activity in the lateral temporal lobe accompanied the mesial increase in 80% of studies, extending over much of the ipsilateral hemisphere and closely associated with the degree and extent of postictal EEG slow waves. These patterns enabled correct seizure localization by blinded analysis in 69% (31/45) of the patients with a unilateral EEG focus. The remainder showed bilateral or no changes. One of six patients with bitemporal EEG foci had unilateral perfusion changes. The positive predictive value for the correct localization of a unilateral focus by postictal SPECT was 97% (31/32). Postictal CBF imaging with SPECT can be used to support noninvasive electrographic localization and may decrease the need for invasive electrode studies.

SPECT in the localisation of extratemporal and temporal seizure foci.

The yield of ictal, postictal, and interictal SPECT was compared in the localisation of seizure foci in 177 patients with partial epilepsy. In 119 patients with known unilateral temporal lobe epilepsy ictal SPECT (97% correct localisation) was superior to postictal SPECT (71% correct), which was better than interictal studies (48% correct). Similarly, in cases of known or suspected extratemporal epilepsy the yield of ictal SPECT studies was high (92%). By contrast, the yield of postictal studies was much lower (46%) and usually only very early postictal studies were diagnostic. Interictal SPECT was of little value. The accuracy of ictal SPECT in localising temporal lobe seizures is now well established. Extratemporal seizures are often brief and difficult to localise. This report shows that ictal SPECT also has a high diagnostic yield in a wide range of extratemporal epilepsies. The brevity of many extratemporal seizures means that true ictal SPECT examinations can be difficult to achieve, but the high diagnostic yield justifies the special organisational effort needed to obtain such studies.

Psychosocial Difficulties and Outcome After Temporal Lobectomy

Summary: One hundred fifteen consecutive patients in the Austin Hospital Comprehensive Epilepsy Program (Melbourne, Australia) were surveyed to document the psychosocial and rehabilitation difficulties after temporal lobectomy. During the follow‐up period (mean 4 years) 3 patients died, 5 patients were lost to follow‐up, and 107 patients with family and friends were interviewed. Eighty‐four patients (78%) had been seizure‐free for the year preceding the interview; 13 others had seizure reduction >75%. Success in ablation or reduction in seizures correlated with the amount of postoperative gain, but in this series, analysis of work and dependency out‐come did not emphasize areas of success. Although improvement in work and financial status, interpersonal relations and sexuality were all recorded, successful patients deemed that most advance had been made in the areas of newly acquired independence, enhanced career potential, and social freedom. Significant postoperative anxiety, especially after left temporal lobectomy, was noted, possibly explained by benzodiazepine antiepileptic drug (AED) discontinuation. Although 1 patient committed suicide, neither depression nor psychosis was common in the rehabilitation period, in contrast to results in previous series. Significant sociodomestic problems emerged from this survey, however: 35% of patients considered successes reported postoperative problems stemming from the necessity to restructure family dynamics; in 6%, this resulted in divorce. Moreover, 20% of patients and relatives reported significant behavioral problems in coping with the seizure‐free lifestyle. Finally, the problems of the worsened situation after surgical failure indicated the counterproductive potential of ineffective lobectomy. These results indicate the necessity for a pre‐operative counseling program to prevent these problems.

Lateralization of verbal memory and unilateral hippocampal sclerosis : evidence of task-specific effects

This study retrospectively investigated the effect of left (LHS) versus right (RHS) hippocampal sclerosis on verbal memory, measured by means of the Paired Associate Learning and Logical Memory subtests of the Wechsler Memory Scale (WMS) administered as part of a routine preoperative assessment. Patients were selected for the presence of unilateral hippocampal sclerosis by means of preoperative magnetic resonance imaging (MRI) and postoperative neuropathology. The LHS patients (n = 20) were significantly worse on paired associate learning than RHS patients (n = 18), the performance of RHS patients being consistent with normative standards. In contrast, no laterality effect was seen on the immediate and delayed recall of passages; the evidence suggests that both groups performed at a mildly impaired level. It was suggested that the laterality of verbal memory is conditional upon specific task demands in patients with damage to mesial temporal structures.

Postictal switch in blood flow distribution and temporal lobe seizures.

The ictal increase of regional cerebral blood flow has yet to be fully utilised in the investigation of focal seizures. Although single photon emission tomography (SPECT) is being increasingly used in the localisation of epileptic foci, the evolution and time courses of the peri-ictal perfusion changes have yet to be clarified. We performed serial SPECT studies in the interictal, ictal and immediate postictal states in 12 patients with refractory temporal lobe epilepsy to define the patterns and duration of peri-ictal cerebral blood flow changes. Visual analysis showed a constant pattern of unilateral global increases in temporal lobe perfusion during seizures which suddenly switched to a pattern of relative mesial temporal (hippocampal) hyperperfusion and lateral temporal hypoperfusion in the immediate postictal period. Quantitative analysis confirmed the visual assessment. Lateral temporal cortex ictal/normal side to side ratios were increased by mean 35.1% (95% confidence interval 21.8% to 48.4%) more in the ictal studies than in the interictal studies and mesial temporal cortex ratios increased by mean 30.8% (22.4% to 39.2%). In the postictal state, however, lateral temporal ratios were reduced by mean 7.7% (-15.8% to 0.4%) compared with interictal values, whereas mesial temporal perfusion was maintained compared with the interictal studies. These observations provide critical information for interpreting scans which can be used in the localisation of epileptic foci. This postictal switch in blood flow patterns may reflect the underlying metabolic processes of neuronal activation and recovery and have implications for understanding the neurobiology of human epileptic seizures.

A prospective study of lacunar infarction using computerized tomography

Sequential computed tomography (CT) scans were performed for up to 7 months on patients who presented with clinical evidence of lacunar infarction or ischemia. Sixty-nine percent of the patients showed lacunar infarction, and a negative scan did not suggest a better prognosis in stroke patients. Of patients with transient ischemic attacks (TIA) (lacunar), those with repeated bursts of hemiplegia (capsular warning syndrome) were more likely to be CT-positive (p < 0.01). The clinical features of patients with lacunar infarction were examined and correlated with the features of infarction. Partial syndromes were found in 32% of the cases and included examples of monoparesis and dysarthria alone.