On the surgical treatment of refractory epilepsy in tuberous sclerosis complex

Using the pig as a model, it was shown that stimulation of the distal nerve ending of the pudendal nerve leads to the isolated stimulation of the external anal sphincter muscle. No difference in pressure response was noted after application of between 0.5 and 1.5 mA unilateral or bilateral stimulation. Major advantages observed using between 1.5 and 2.5 mA bilateral stimulation; with a stimulation between 2.0 and 2.5 mA the pressure response was twice as high compared to unilateral stimulation. Continuous stimulation of the striated anal sphincter muscle leads to fatigue, reaching 50% fatigue after a median time between 40-90 s. In cyclic stimulation (alternation every 15 s, duration 20 min) a fatigue reaction was also seen. The peak pressure decreased after 20 min for a median of 11%, the final pressure was lowered in 15% following a logarithmic curve pattern. The experimental application of variable impulse ranges also caused pressure differences. Increasing the impulse range from 200 to 450 microseconds (peak pressure) vs. 400 microseconds (final pressure) resulted in a statistically significant pressure increase. Therefore, it was proven that selective stimulation of the external anal sphincter muscle can lead to a transient pressure increase, which possibly improves fecal continence.     

A resonator impedance de-embedding procedure

In many contemporary high-frequency circuits, a dielectric resonator is coupled to a microstrip line section, the ends of which constitute a two-port. A detailed procedure is presented for recovery of impedance values associated with the resonator from S-parameter measurements on the two-port with a vector network analyzer. The procedure is suitable for computer-assisted numerical processing, takes into account lossy propagation and moderate impedance vagaries along the microstrip line, and includes discontinuities in the coax-to-microstrip transitions. Resonant frequency, unloaded Q, and effective coupling coefficient can be determined subsequently from the de-embedded impedance values     

Pulse shaping for low-noise, charge preamplifiers

Pulse shaper circuits are often needed to reduce noise levels and condition signals for processing. The noise attributes of several time-invariant and time-variant pulse shapers are compared for a charge preamplifier designed for atomic calorimetry measurements. Pulse shapers reviewed are equally applicable to a wide range of measurement applications. Previous work examining the noise attributes of pulse shapers has been based on simplistic noise modeling. The contribution of this work is a comparison of the noise characteristics of a reasonably complete set of pulse shaper configurations using the noise modeling available through the SPICE circuit simulator. A pulse shaper is selected for fabrication, and experimental results are discussed     

A multicenter study of the efficacy of the ketogenic diet

OBJECTIVE: To determine the efficacy of the ketogenic diet in multiple centers. DESIGN: A prospective study of the change in frequency of seizures in 51 children with intractable seizures who were treated with the ketogenic diet. SETTING: Patients were enrolled from the clinical practices of 7 sites. The diet was initiated in-hospital and the patients were followed up for at least 6 months. PATIENTS: Fifty-one children, aged 1 to 8 years, with more than 10 seizures per week, whose electroencephalogram showed generalized epileptiform abnormalities or multifocal spikes, and who had failed results when taking at least 2 appropriate anti-epileptic drugs. INTERVENTION: The children were hospitalized, fasted, and a 4:1 ketogenic diet was initiated and maintained. MAIN OUTCOME MEASURES: Frequency of seizures was documented from parental calendars and efficacy was compared with prediet baseline after 3, 6, and 12 months. The children were categorized as free of seizures, greater than 90% reduction, 50% to 90% reduction, or lower than 50% reduction in frequency of seizures. RESULTS: Eighty-eight percent of all children initiating the diet remained on it at 3 months, 69% remained on it at 6 months, and 47% remained on it at 1 year. Three months after initiating the diet, frequency of seizures was decreased to greater than 50% in 54%. At 6 months, 28 (55%) of the 51 initiating the diet had at least a 50% decrease from baseline, and at 1 year, 40% of those starting the diet had a greater than 50% decrease in seizures. Five patients (10%) were free of seizures at 1 year. Age, sex, principal seizure type, and electroencephalogram were not statistically related to outcome. CONCLUSION: The ketogenic diet is effective in substantially decreasing difficult-to-control seizures and can successfully be administered in a wide variety of settings.     

Asymmetries in the effect of side of seizure onset on recognition memory following intracarotid amobarbital injection

OBJECTIVE: To report gross anatomic examination of the canine myocardial bridge (MB), a muscular band found above the coronary artery (CA), with respect to its occurrence, location, vascularization, and innervation. SAMPLE POPULATION: 629 canine hearts obtained within 1 to 3 hours after euthanasia. PROCEDURE: After an incision was made at the left fifth intercostal space, the pericardial sac was cut open, and if an MB was present, the heart, lungs, and annexed structures were removed together and subsequently subjected to macroscopic examination of MB musculature and innervation after formalin fixation. Vascular casting was performed by use of methyl methacrylate perfusion. RESULTS: Of the 629 canine hearts examined, 189 (30%) had MB, occurrence of which was independent of sex, age, and breed. Among 13 MB-containing specimens examined in detail, there was great variation in thickness (0.11 to 2.24 mm; mean, 0.45 mm) of MB and distance (24 to 236 microns; mean, 103 microns) between the MB and the paraconal interventricular branch of the left CA (PIBL). One pair or 2 pairs of blood vessels from the PIBL supplied the MB muscle. Venous blood returned to the coronary circulation via the branches of the great coronary vein coursing on both sides of the PIBL, in close contact with the PIBL and the groove wall. The 2 veins rejoined at the upper portion of the PIBL and passed obliquely to the coronary groove under the left auricle, and finally drained the blood through the coronary sinus into the right ventricle. Innervation to the MB muscle was derived from nerve branches of the middle cervical ganglion and left vagus nerve. CONCLUSION: Prevalence and localization of MB in dogs and human beings are similar. Vascularization of the MB muscle originates from the PIBL. The cervical ganglion and vagus nerve control the MB muscle.     

Introducing undergraduates to the moment method

Four application problems are presented which have been found to facilitate introductory instruction on numerical methods for undergraduate electrical engineering students. The method of moments (MOM) is introduced at the level of first principles, preparing students for subsequent advanced topics in matrix methods and developments through linear vector space theory. The problems are such that the associated computer programming assignments are straightforward, minimizing distraction from the mathematical concepts. Numerical solutions may be obtained, or verified, with a pocket calculator in some cases. Computer programs to obtain more sophisticated graphics output and to expedite solution of equations with large matrices can be progressively added as supplementary student exercises     

Virtual Chesapeake Bay: interacting with a coupledphysical/biological model

The Chesapeake Bay Virtual Environment (CBVE) is a multidisciplinary, collaborative project that fuses 3D visualizations of numerically generated output, observations and other data products into a large-scale, interactive virtual world that supports investigation of coupled physical/biological and environmental processes. Although still under development, CBVE provides an application framework for integrating circulation and biological models with the computer visualization paradigm of the virtual world. In this article, we first briefly describe the physical environment and the observed effects of winds, tides and river runoff on the Chesapeake Bay system. Then we describe the CBVE components and conclude with our efforts directed at understanding how environmental variability may affect the recruitment and retention of the larval phase of certain local marine species     

Corpus callosotomy for medically intractable seizures

To identify factors influencing outcome and morbidity in patients selected for corpus callosotomy, we retrospectively reviewed 23 patients with intractable generalized seizures who underwent corpus callosotomy between 1991 and 1994. Three patients had a complete corpus callosotomy, while 20 had an anterior callosotomy. Three of those patients subsequently had completion of the anterior callosotomy. Overall, 41% of patients were nearly or completely free of the seizure types targeted for surgical treatment, while another 45% had seizures less than half as frequently. Four patients developed simple partial motor seizures after callosotomy. A transient disconnection syndrome was observed in 57% of patients. The best predictor of good outcome was a normal preoperative MRI. Mentally retarded patients had poorer outcomes. Outcome was not predicted by extent of callosal section or lateralization on neurological examination, EEG, MRI, and SPECT. Completion of anterior callosotomy resulted in significant reductions in seizure frequency. Though most patients do not become seizure-free after corpus callosotomy, worthwhile palliation of an otherwise intractable illness can be achieved. An analysis of prognostic factors should lead to better selection of patients for surgery.     

Effects of temporal lobe epilepsy on spatial and figural aspects of memory for a complex geometric figure

The preoperative delayed memory performance on the Rey-Osterrieth Complex Figure (Lezak, 1983) of 54 patients with complex partial seizures of temporal lobe origin was analyzed using 3 different indices. One index (composite) was derived using a common scoring method that included both spatial and figural aspects of memory in its score. The other two indices were derived emphasizing either spatial or figural aspects of memory for the elements of the figure separately. All 3 indices distinguished between individuals with right-sided (RTLE) and left-sided (LTLE) seizure onset. However, spatial memory was significantly lower than figural memory in individuals with RTLE as compared to those with LTLE. Both the spatial and figural memory indices were significantly lower in the presence of magnetic resonance imaging (MRI) evidence for hippocampal sclerosis in individuals with RTLE. Results suggest that while both the spatial and figural aspects of nonverbal memory are sensitive to right hippocampal dysfunction, figural memory may be less vulnerable to the effects of RTLE.