Allen R. Wyler

Amnesia after unilateral temporal lobectomy: a case report.

Summary: We report a mixed handed (L>R) patient with exclusive right cerebral language representation who de–veloped a permanent anterograde amnestic syndrome after right anterotemporal lobectomy. Preoperative neuropsychological performance consisted of impaired verbal memory and normal nonverbal memory. Wada memory performance was asymmetrical for objects presented soon after amobarbital injection in conjunction with no memory asymmetry for items presented later in the Wada evaluation. Preand postoperative magnetic resonance imaging (MRI) scans showed no structural lesions; however, postoperative MRI hippocampal volume measurements suggested decreased hippocampal volume for the nonresected temporal lobe. These results confirm the risk of anterograde amnesia after unilateral temporal lobectomy and demonstrate that baseline neuropsychological testing may falsely literalize material‐specific memory functions in patients with atypical cerebral language dominance.

Neuropsychological outcome of anterior temporal lobectomy

Reviews of the literature have suggested that, following anterior temporal lobectomy (ATL) for treatment of medically intractable epilepsy, most cognitive functions remain unchanged, some exhibit a relative loss compared to preoperative levels, and some cognitive functions improve. The purpose of this investigation was to identify more precisely the nature and degree of this postoperative cognitive stability, loss, and gain. Thirty-eight patients undergoing ATL received an extensive neuropsychological evaluation both preoperatively and 6 months postoperatively. Utilizing an operational definition of neuropsychological test change that was hypothesized to be sensitive to performance alterations of probable clinical significance, we found that 77% of the neuropsychological measures remained unchanged following ATL. Of the cognitive change that occurred, 58% of the changes reflected significant cognitive improvement, whereas 42% of the changes reflected relative cognitive declines. Specific results are presented in regard to nine cognitive domains (psychometric intelligence, academic achievement, language function, visuoperceptual and visuospatial ability, memory and learning ability, problem-solving skills, sensorimotor ability, auditory-perceptual function, and complex attention/concentration skills). Only the area of memory/learning showed more cognitive loss than gain, and the area of novel problem-solving ability showed the most improvement. The clinical and theoretical implications of these findings are discussed.

Chronic subdural strip electrode recordings for difficult epileptic problems

We report a prospective series of 100 consecutive patients who underwent recordings with chronic subdural strip electrodes to resolve difficult diagnostic and treatment issues regarding medically refractory epilepsy. All patients had previously undergone chronic EEG/video monitoring with scalp with or without sphenoidal electrodes. After subdural strip electrode recordings 62 patients were found to have unilateral epileptogenic foci amenable to surgical resection. These include two patients previously diagnosed as having pseudoseizures. Forty-five patients underwent focal resection and were followed for at least 6 months; 96% are seizure-free or significantly improved. Of the 38% who did not have a focus diagnosed, 22 were found to be candidates for anterior corpus callosotomy. Four patients had inconclusive monitoring results, and 11 patients were found not to be surgical candidates. There has been no morbidity or mortality in this series of patients. We conclude that subdural strip electrode recording is a relatively safe and effective method for resolving difficult diagnostic issues involving the treatment of medically refractory epilepsy.

Comparative results of dominant temporal lobectomy under general or local anesthesia: Language outcome

For surgical candidates with intractable seizures of dominant temporal lobe origin, concerns are often raised regarding the potential effects of anterior temporal lobectomy (ATL) on language function. While a variety of surgical procedures exist, there are no data regarding their comparative effects on language ability. This report presents the results of a prospective controlled study, which assessed pre- and postoperative (6 months) language function in a consecutive series of 26 patients who underwent dominant hemisphere ATL. Thirteen consecutive patients received surgery under local anesthesia in conjunction with intraoperative cortical mapping of language function, and 13 subsequent consecutive patients underwent surgery under general anesthesia. A standardized battery assessed multiple aspects of language ability so that the comparative effects of language outcome could be determined. The results revealed that patients who underwent ATL under general anesthesia received significantly less lateral temporal lobe resection, exhibited more postoperative gains in various aspects of language function, were more likely to be rendered totally seizure-free, but showed a mild nontransient postoperative dysnomia. The clinical and theoretical implications of these findings are discussed.

Comparative results of temporal lobectomy under local or general anesthesia: Seizure outcome

One-hundred patients underwent temporal lobectomy for control of epilepsy and had follow-up 1.5–12 years later. Fifty cases were operated on under local and 50 under general anesthesia. Seventy-two percent of general anesthesia patients were seizure-free from surgery, whereas only 54% of local anesthesia patients were seizure-free. Although this difference is not statistically significant, it shows a clinically meaningful trend toward an improved seizure outcome for the general anesthesia group. There was no difference in morbidity between the two groups. Because we can find no demonstrable advantage to routine temporal lobe epilepsy surgery under local anesthesia, we now resect all mesial temporal lobe foci under general anesthesia, even when they reside within the speechdominant hemisphere.

Morbidity of long-term seizure monitoring using subdural strip electrodes: A follow-up

We report the third arm of a prospective study of morbidity associated with long-term seizure monitoring using subdural strip electrodes. The first group of 175 patients received antibiotics intravenously during the entire period the electrodes were implanted, and a second group received one dose of antibiotics on the morning of surgery. The overall rate of serious complications in these two groups was 0.85%. There was no significant difference in infection rates between the two groups. We now conclude the study with a third arm of 217 patients who received no antibiotics. Again, the complications related to implantation were only infectious with a complication rate of 2.7%. Although these numbers are too small to be rigorously tested statistically, this threefold increase in infectious complications leads us to use prophylactic use of antibiotics (one dose preoperatively).

Strip electrodes in acute electrocorticography

Strip electrodes have been used to augment acute cortical electrocorticography (ECoG) in 100 consecutive surgeries for epilepsy. The strip electrodes have been especially helpful in defining the extent of mesial temporal and mesial frontal foci. When dealing with temporal lobe foci, strip electrodes can help identify epileptiform activity residing in posterior regions of hippocampus which should be removed. Thus, we have found that strip electrodes can significantly augment information gained during acute ECoG recordings as well as decrease the time needed for recordings.