Relevance of residual histologic and electrocorticographic abnormalities for surgical outcome in frontal lobe epilepsy.

PURPOSE: To estimate the significance of residual electrocorticographic and neuropathologic abnormalities on seizure control after surgery for frontal lobe epilepsy with the purpose of determining their relevance in deciding the extent of the surgical procedure. METHODS: The presence of epileptiform discharges in intraoperative electrocorticograms (ECoGs) and the nature and extent of neuropathologic abnormalities were reviewed for 35 patients who underwent frontal lobe resections for the treatment of epilepsy at our institution. The relations between surgical outcome and presence of the following features were studied: (a) presence of abnormal tissue at the limits of the resection; (b) presence of sporadic spikes and seizure patterns in the preresection ECoG; (c) their abolition in the postresection ECoG; and (d) the topography of residual discharges with respect to the margins of the resection. RESULTS: On neuropathologic examination, 18 patients showed focal cortical dysplasia (CD), and 17 showed other abnormalities (non-CD). Ten CD patients and 11 non-CD patients experienced a favourable outcome. Seizure patterns were significantly more common in patients with focal cortical dysplasia than in those without, with a sensitivity of 94% and a specificity of 75%. Abolition of seizure patterns was associated with a favourable surgical outcome (p = 0.031). Abolition of sporadic spikes or their presence in the postresection ECoG did not influence outcome. There was no clear relation between outcome and location of residual sporadic discharges. Seizure patterns persisted in the postresection ECoG in three CD patients, were located at the margins of the resection in all three, and these patients had a poor outcome. Incomplete removal of abnormal tissue was not associated with a poorer outcome in either patient group or in the complete sample. CONCLUSIONS: Seizure patterns were significantly more common in patients with cortical dysplasia, and their abolition on postresection ECoG recordings was associated with a favourable surgical outcome. Persistence of sporadic ECoG spikes and incomplete removal of histologic abnormalities did not affect outcome significantly.

Prognostic factors in presurgical assessment of frontal lobe epilepsy.

OBJECTIVES: To determine predictors for surgical outcome in the presurgical assessment of frontal lobe epilepsy. METHODS: Thirty seven patients were operated on for frontal lobe epilepsy between 1975 and 1996. Their medical records were reviewed for ictal semiology, age at onset, duration of the epilepsy, age at operation, preoperative interictal and ictal encephalographic findings, and abnormalities on neuroimaging and neuropsychological testing. In addition, type of resection and pathology were compared with surgical outcome. RESULTS: Univariate statistical analysis showed that the presence of a focal abnormality on neuroimaging was associated with favourable outcome. The presence of the following ictal findings was associated with poor outcome: autonomic manifestations, eye deviation, head version contralateral to the operated side, and bilateral or multifocal ictal onset. Fifteen patients had secondarily generalised interictal discharges and, interestingly, their presence was not associated with poor outcome. Multivariate logistic regression showed that the presence of a focal abnormality on neuroimaging was significantly associated with a favourable outcome while contralateral head version was the only variable significantly associated with poor surgical outcome. CONCLUSIONS: A focal abnormality on neuroimaging was the only variable which was significantly associated with a favourable surgical outcome, whereas contralateral head version was the most significant predictor for a poor outcome. The presence of generalised discharges before surgery was not associated with poor outcome.

Volumetric determination of the U/O ratio in uranium oxides.

A method is given for determining the general formula UO(2+x), of sintered uranium dioxide pellets and uranium dioxide powders. Uranium(VI) is reduced by titration with iron(II) ammonium sulphate, after which the total amount of uranium is oxidized by titration with potassium dichromate. The end-points of both titrations are detected electrometrically. Determination of x in the range 0.0001-1.00 is possible.

Microdetermination of oxygen, carbon and water in inorganic materials using a carrier-gas technique.

A description is given of the accurate determination of small quantities of oxygen, carbon and water in inorganic compounds. Oxygen and carbon are determined by a conductimetric technique and water by a coulometric technique. The limits of detection of the different methods are: 0.1 microg of oxygen, 0.1 microg of carbon and 0.03 microg of water. This is accomplished by taking special care to obtain a low blank and by using stable instruments. A suggestion is made for the simultaneous determination of water and hydrogen.