Faculty Bibliography

Currently available digital EEG equipment provides considerably greater opportunities for clinical data analysis than is generally appreciated especially when appropriate software is used. Data from 7 different laboratories that had been obtained for routine diagnostic evaluations on 7 different EEG instruments and stored on compact disks were investigated. Since the instruments do not filter the data at input, ultra slow activity down to 0.01 Hz is currently being recorded but the attenuation factor is instrument dependent. Nevertheless, relevant clinical information is potentially available in these data and needs to be explored. Several examples in regard to epilepsy are presented. Determination of seizure onset may depend on the frequencies that are examined. The use of appropriate filter settings and viewing windows for the clinical question to be answered is stressed. Differentiation between simple and complex spike wave discharges, as well as spread of spikes, can readily be achieved by expanding the time base to 1 or 2 seconds and placing a cursor on the peak of the negative spike. Latencies in the millisecond range can then become apparent. EEGs co-registered with MEG should be evaluated with the same software in order to allow an adequate assessment of the similarities and differences between electrical and magnetic activity. An example of a comparison of EEG, planar gradiometers and magnetometers for an averaged spike is shown

OBJECTIVE: To examine the relationship between the degree of handedness and hemispheric language dominance in patients with epilepsy. METHODS: The authors examined the relationship between degree of handedness and hemispheric language dominance in 174 epilepsy surgery candidates using the intracarotid amobarbital procedure and results from a modified version of the Edinburgh Handedness Inventory. RESULTS: The incidence of atypical language dominance increased linearly with the degree of left-handedness, from 9% in strong right-handers (laterality quotient [LQ] = +100) to 46% in ambidextrous individuals and 69% in strong left-handers (LQ = -100). CONCLUSIONS: The incidence of atypical language dominance depends not only on the direction but also on the degree of handedness. In addition, direction of language dominance varies with hemisphere of seizure focus and degree of handedness. A familial history of sinistrality may have an additional effect on the likelihood of atypical dominance

OBJECTIVE: Tuberous sclerosis complex (TSC) is associated with medically refractory epilepsy and developmental delay in children and usually results from cortical tubers. Seizures that begin in young patients are often refractory and may contribute to development delay. Functional outcome is improved when seizures are controlled at an early age. Previous reports have shown modest benefit from surgical resection of single tubers/seizure foci in older children; however, many children with TSC develop uncontrolled seizures before age 1. To identify patients who might benefit from surgery and to maximize outcome, we used a novel surgical approach in young children that consists of invasive intracranial monitoring, which is typically 3-staged and often bilateral. METHODS: Of 110 consecutive children who underwent epilepsy surgery by a single surgeon in the past 6 years, 25 patients (9 boys and 16 girls) had TSC. At the time of their first surgery at our institution, they were a median age of 4.0 years. A total of 31 separate admissions for epilepsy surgery in these 25 patients were identified. Bilateral electrode placement was performed in 13 children whose seizures could not be lateralized definitively preoperatively, and 22 patients underwent 3-stage surgeries. RESULTS: At 6 months or longer after the initial resection, 21 (84%) children were class I, 2 (8%) children were class II, and 2 (8%) children were class IV. At a mean follow-up of 28 months, 17 (68%) children were class I, 6 (24%) were class II, and 2 (8%) were class III. Four of the 5 children who initially were rejected as surgical candidates because of multifocality and who required initial bilateral electrode study are now seizure-free. CONCLUSIONS: This approach can help to identify both primary and secondary epileptogenic zones in young TSC patients with multiple tubers. Multiple or bilateral seizure foci are not necessarily a contraindication to surgery. Long-term follow-up will determine whether this approach has durable effects

OBJECTIVE: To report the technique of subpectoral (SP) implantation of the vagus nerve stimulator (VNS) generator. METHODS: We retrospectively reviewed and compared demographics and complications from patients receiving either subcutaneous (SQ; n = 107) or SP (n = 138) VNS implants, performed by one surgeon (WKD) between 1999 and 2003. Selection of implant location was made during the preoperative surgeon-patient consultation on the basis of surgeon recommendation and patient preference. RESULTS: The standard VNS generator implantation is performed within a SQ pocket in the left infraclavicular region of the chest. We have modified this technique by placing the generator into a deeper pocket SP, beneath the pectoralis major muscle, while tunneling the electrodes SQ in the usual fashion. The SP group was substantially younger (median age 19 yr) compared with the SQ group (median age 29 yr). At an average follow-up of 52 months for SQ implants and 28.4 months for SP implants, there were 2.9% infections per patient in the SQ group and 2.5% infections per patient in the SP group. There were three cases of excessive generator mobility in the SQ group; no cases occurred in the SP group. CONCLUSION: The SP implantation technique provides an attractive alternative to SQ VNS implantation. With increased soft tissue coverage, we provide improved cosmesis, increased wound durability to tampering and trauma, and a comparable infection rate with the SQ group