In vitro evaluation of brain lesioning electrodes (Leksell) using a computer-assisted video system.

Radiofrequency (RF) generated thermal brain lesions are widely used in functional neurosurgery. The size, shape and development of the lesions depends on system parameter settings and the electrode configuration. Difficulties in studying the effect of these factors in vivo stimulated us to develop an in vitro system for standardized comparison between different electrodes and physical parameters. A computer-assisted video system was set-up allowing continuous video recording of RF-generated coagulations in either a standard albumin solution or in the fresh white of a hen's egg as transparent test substrates. Ten lesions were made with each test electrode (two bipolar and three monopolar) in each of the two substrates at 70 degrees, 80 degrees and 90 degrees C (t = 60 sec). Due to the better homogeneity the lesions in the albumin solution were much more regular and reproducible. This made it possible to calculate the size (width 2.2 +/- 0.1 to 5.3 +/- 0.1 mm and length 3.0 +/- 0.1 to 8.7 +/- 0.3 mm) as well as the volume (8.5 +/- 1.4 mm3 to 133.5 +/- 26.8 mm3). It is concluded that this in vitro system offers a reproducible way to study and document the effect of different electrode configurations and RF-generator settings on the formation of a heat lesion. Even if the results are not directly applicable to the living human brain they give an estimate of the form and size of a coagulation lesion and can be of value for standardized comparisons between different electrodes.

Health-related quality of life after epilepsy surgery: a Swedish multicenter study.

PURPOSE: To investigate health-related quality of life (HRQOL) in relation to seizure outcome as part of a multicenter follow-up of epilepsy surgery in Sweden. METHODS: A battery including the SF-36 Health Survey and the Hospital Anxiety and Depression scale (HAD) was distributed to all patients older than 16 years. Mean follow-up time was 4 years (range, 2-13 years) and response rate, 91% (103 of 113 patients). HRQOL data were related to seizure frequency and severity (Chalfont Seizure Severity Scale). RESULTS: Seventy-six percent considered their global health to be better than it was before surgery. Degree of improvement in seizure control correlated with improved satisfaction with health (Spearman's r = 0.44). Higher SF-36 scores (higher HRQOL ratings) correlated with percentage reduction of seizure frequency for all scales and was strongest for perception of general health (Spearman's r = 0.46). When the patients were divided into four categories [A, completely seizure free (n = 29); B, seizure free with aura (n = 18); C, > or =75% reduction in seizure frequency (n = 24); and D, <75% reduction in seizure frequency (n = 32)], a strong positive association was found between higher SF-36 scores (with the exception of physical functioning) and better seizure control. Health-related limitations in role performance differentiated best between the outcome categories. For patients with > or =75% reduction in seizure frequency, low seizure severity correlated with higher HRQOL ratings for scales measuring social function, vitality, and mental health. Depression levels (HAD scale scores) were on average low. Anxiety (HAD) increased significantly from A to D. CONCLUSIONS: HRQOL seems to be scored as a continuum in relation to seizure frequency. Seizure severity measures give complementary information.

Changes in cerebral blood flow after stereotactic thalamotomy.

Regional cerebral blood flow (rCBF), a parameter of neuronal activity in the brain, was measured by the 133Xe inhalation method in 43 patients undergoing stereotactic thalamotomy. A postoperative flow reduction of about 2% in the operated hemisphere was found, persisting in further measurements performed after a year. There was no consistent change in the pattern of regional flow distribution. The results indicate a diminished level of activity in the hemisphere subjected to thalamotomy, but the change could not be linked to any specific area or function.

Recovery of the hypothalamus-pituitary-adrenal axis after short term high dose corticosteroid treatment in neurosurgical practice.

The recovery of the hypothalamus-pituitary-adrenal axis after high-dose short-term steroid treatment was investigated in 18 patients undergoing stereotactic thalamotomy during local anaesthesia, in whom perioperative betamethasone was given in a high dose for 4-5 days and withdrawn without tapering. There were no untoward clinical effects of the abrupt withdrawal of the steroid. Seven patients undergoing the same operation without steroid treatment served as controls. The recovery of the hypothalamus-pituitary-adrenal axis after steroid treatment was studied by basal plasma cortisol levels. In 12 patients the reserve capacity of the system was investigated by the cortisol response to insulin induced hypoglycemia as well. It was found that the basal plasma cortisol levels had normalized 2 days after the abrupt withdrawal of betamethasone. In spite of normalized basal cortisol levels the capacity to respond to stress was reduced for a further 3 days. Six to seven days after the steroid withdrawal the stress response was, however, completely restored. It is concluded that high dose, short term steroid treatment can be withdrawn abruptly, omitting the usual tapering of the dose. During the first week after steroid withdrawal the cortisol response to stress is reduced even in the presence of normal basal cortisol levels. During this period extra corticosteroids must be supplied in case of an emergency situation or an operation.

Stereotaxic lesion as a model of brain edema.

Repeated computed tomographic (CT) examinations after thalamotomy showed a lesion vrying in size over time. This variation was interpreted as indicating presence of an edema. The effect of steroid treatment upon such an edema was tested in a pilot study of 28 patients, 16 of whom were given betamethasone. The diameter of the lesion as observed on CT was used as a measure of the amount of edema. The mean diameter was significantly lower in the steroid-treated group as compared with controls (p less than 0.01, Mann-Whitney U test). The groups were comparable with respect to other variables that might influence lesion size. It is concluded that steroid treatment has an edema-preventing effect.

Changes in regional cerebral blood flow following stereotactic psychosurgery.

Serial measurements of regional cerebral blood flow by the 133Xe inhalation method were performed in a pilot study in 6 patients undergoing stereotactic psychosurgical procedures (anterior capsulotomy, cingulotomy, frontobasal tractotomy). Average hemispheric flow did not change significantly from pre- to post-operative, but changes were seen in the patterns of regional flow distribution. The most striking finding was frontal flow reduction following capsulotomy. In view of the coupling of blood flow and function in the brain, the results indicate that this method offers a new way for exploring the effects of functional neurosurgery on brain activity.