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Biomedical subjects

D L Schomer

Publications and source records attributed to D L Schomer.

14 recordsLinked to original sources
PubMed1991

Broca's aphasia following damage to Wernicke's area. For or against traditional aphasiology?

Classic aphasiology has been challenged by studies that have employed cranial computed tomography to test predicted anatomic-behavioral correlations. We treated a patient who developed a classic Broca's aphasia but whose computed tomographic scan revealed damage to Wernicke's area, thus seeming to contradict the principles of traditional aphasiology. However, subsequent information obtained by magnetic resonance imaging, intracarotid amobarbital (Amytal) testing, and electrophysiologic studies, including cortical stimulation, demonstrated that the brain-behavior correlations in this patient can be understood in terms of the formulations of traditional aphasiology.

Adult↗
PubMed1991

128-channel cable-telemetry EEG recording system for long-term invasive monitoring.

A 128-channel cable-telemetry EEG monitoring system has been developed for use on patients undergoing intensive neurodiagnostic monitoring with invasive intracranial electrodes. A unique head mounted preamplifier/multiplexor design allows continuous recording from any combination of intracerebral, subdural, epidural or surface electrodes. A computer is used to delay or buffer all 128 channels by 2 min or more. This computer is connected to a fileserver via a local area network and is used exclusively for data acquisition. Seizure files created by the activation of the seizure/event push button or detected by a second computer containing on-line seizure/spike detection algorithms are written directly on to the fileserver by the acquisition computer. The 128 channels of EEG recorded on the fileserver can then be remotely reviewed on a high resolution graphics terminal, printed out on a laser jet printer, archived or played out on paper, 16 channels at a time on any EEG machine. A time of day signal is also generated by the computer to permit time correlation with a continuous audio/video VCR unit which permits comparison of the EEG and clinical events. This system allows continuous EEG monitoring of extensive multichannel arrays not previously possible with conventional 16-, 32- or even 64-channel systems.

Electroencephalography↗
PubMed1991

High resolution EEG output using a laser printer.

With increasing computerization, digitization and complexity of 64- to 128-channel long-term monitoring (LTM), new problems have arisen with data presentation. We describe customized software that allows for high resolution EEG output on a standard laser printer. This system can display from 1 to 128 channels of EEG on standard or legal size paper with freedom to alter both time and amplitude scales as desired. This technique is inexpensive and provides a high resolution rectilinear paper record of selected EEG events that is convenient for review and storage.

Computers↗
PubMed1991

Right hemisphere advantage for evaluating emotional facial expressions.

The ability to evaluate the intensity of emotional facial expressions was investigated in patients undergoing the intracarotid sodium amytal procedure. It was found that when the hemisphere non-dominant for language (usually right) was anesthetized, the patients' ratings of the intensity of emotional expressions in photographs were lower than baseline ratings of these expressions. Such an effect was not seen with anesthetization of the hemisphere dominant for language (usually left). Ratings of shades of gray (which served as control stimuli) showed no such effect. The findings are interpreted in terms of a right hemisphere superiority in the perception and evaluation of emotional expression.

Adolescent↗
PubMed1990

MEG versus EEG localization test using implanted sources in the human brain.

It is believed that the magnetoencephalogram (MEG) localizes an electrical source in the brain to within several millimeters and is therefore more accurate than electroencephalogram (EEG) localization, reported as 20 mm. To test this belief, the localization accuracy of the MEG and EEG were directly compared. The signal source was a dipole at a known location in the brain; this was made by passing a weak current pulse simulating a neural signal through depth electrodes already implanted in patients for seizure monitoring. First, MEGs and EEGs from this dipole were measured at 16 places on the head. Then, computations were performed on the MEG and EEG data separately to determine the apparent MEG and EEG source locations. Finally, these were compared with the actual source location to determine the MEG and EEG localization errors. Measurements were made of four dipoles in each of three patients. After MEGs with weak signals were discounted, the MEG average error of localization was found to be 8 mm, which was worse than expected. The average EEG error was 10 mm, which was better than expected. These results suggest that the MEG offers no significant advantage over the EEG in localizing a focal source. However, this does not diminish other uses of the MEG.

Adult↗
PubMed1990

Abnormal pulsatile secretion of luteinizing hormone in men with epilepsy: relationship to laterality and nature of paroxysmal discharges.

We compared the pulsatile secretion of luteinizing hormone (LH) between 13 men with clinically and electrographically documented temporal lobe seizures and 8 age-matched controls. Serum for LH measurement was drawn every 15 minutes during 8 hours of EEG telemetry in both groups. The 2 groups did not differ significantly in average mean baseline LH secretion, total LH secretion, or average pulse amplitude. The group with seizures, however, showed a significantly greater (p less than 0.05) variability of baseline LH secretion and pulse frequency. Among the men with unilateral paroxysmal EEG findings, pulse frequency was significantly greater (p = 0.05) with right epileptiform discharges or left slowing (6.4 +/- 0.4) than with left epileptiform discharges or right slowing (3.0 +/- 1.3). The relationship of pulse frequency to the nature and laterality of paroxysmal discharges makes it unlikely that endocrine abnormalities can be attributed to medication alone and strengthens the notion that temporal lobe epileptiform discharges may disrupt hypothalamic regulation of pituitary secretion.

Adolescent↗
PubMed1990

Visual neglect during intracarotid amobarbital testing.

The unilateral suppression of hemispheric function by sodium amobarbital may result in hemispatial visual neglect, as measured by performance on a random letter cancellation task. Our study not only investigates this hypothesis but also attempts to identify more precisely the anatomic locus of control for directed attention to extrapersonal space by correlating scanning performance with EEG activity. Forty-eight consecutive patients with epilepsy underwent preoperative intracarotid amobarbital tests. The results indicated that disruption of scanning and contralateral neglect occurred only after right-hemisphere suppression and seemed specifically related to changes in right frontal lobe EEG activity. This pattern of performance held not only for right-handed subjects, but also for those who were left-handed, and even for those who had right-hemisphere language dominance.

Adolescent↗
PubMed1989

Long-term tolerability, pharmacokinetic and preliminary efficacy study of lamotrigine in patients with resistant partial seizures.

Four adult men with resistant partial seizures underwent an intensive open-label protocol designed to evaluate long-term add-on lamotrigine (LTG) therapy. Following an 8-week baseline, LTG was added to their background medication(s) (carbamazepine in three; carbamazepine and phenytoin in one). Incremental LTG doses of 50, 100, 150, and 200 mg every 12 h were given on days 58-60, 61-63, 64-127, and 128-176, respectively. The patients were hospitalized during and after each of the dose increases for a total of 25 days. Frequent outpatient visits were performed biweekly, weekly, or monthly, depending on the phase of the protocol. Frequent clinical, electrocardiographic (ECG), and laboratory evaluations were performed. Serial blood levels and 24-h urine collections were performed sequentially. In patients 1, 2, and 3, LTG was well tolerated at 200 mg b.i.d. Patient 4 did not tolerate 150 mg, b.i.d., but tolerated and maintained complete seizure control on 100 b.i.d. All four patients tolerated LTG and continued to receive it for 39, 46, 105, and 104 weeks, respectively. Serial 12-h plasma LTG levels were obtained on days 63, 70, and 133. On these days, the mean (+/- SD) LTG clearances (dose/AUC) were 0.0436 +/- 0.0171, 0.0468 +/- 0.0093, and 0.0575 +/- 0.0160 L/h/kg, respectively. Some 43-87% of the LTG was recovered in the urine, predominantly as the glucuronide metabolite. In the four patients, the mean weekly seizure frequency per patient was 6.5 in baseline, 5.0 on submaximal LTG doses, and 3.5 on the maximum administered doses. Three of the four patients eventually experienced a greater than 50% decrease in seizure frequency. In conclusion, when given for long periods of time (9.5 months to 2 years), LTG was well tolerated in doses up to 400 mg/day and mean trough levels of 3.0 +/- 0.6 microgram/ml; LTG has a favorable pharmacokinetic profile and appears to exhibit first-order linear kinetics during long-term chronic dosing; LTG shows preliminary evidence of efficacy during long-term administration; and to date, our patients represent the longest reported experience of continuous and closely monitored LTG therapy in the literature.

Adult↗
PubMed1988

A 6-pole filter for improving the readability of muscle contaminated EEGs.

A multi-channel switched-capacitor 6-pole filter for significantly reducing the EMG artifact present during seizures recorded by long-term monitoring procedures has been implemented for routine use. This permits repeated replay of the seizures with different filter settings. All of the channels can be simultaneously dialed to any cut-off frequency (3 dB down) between 8 Hz and 70 Hz and the event replayed for filtering and write-out onto any standard EEG machine. The advantage of the 6-pole switched-capacitor filter is that it does not require a complex design with high precision RC components. The cut-off frequency is determined by the frequency of a simple clock that is used to select the same cut-off point for all 16 channels. By changing the clock frequency, the operator moves the cut-off point linearly. The dramatic improvement obtained by off-line digital filtering that was recently reported (Gotman et al. 1981) indicates that more efficient filtering of EMG contaminated seizures is diagnostically significant in selected cases. This approach is limited by the availability and expense of not only the computer's hardware but also the dedicated software. Specially designed 4-pole analog filters (Barlow 1984) are less expensive than digital filtering, but are difficult to design even at specific frequencies and do not allow for a range of frequencies. The switched-capacitor 6-pole filters have all the advantages of the above but are even more efficient in reducing EMG artifact. They also do not have any of the above disadvantages and cost only a few dollars per channel.

Adult↗
PubMed1988

Surgical approaches to epilepsy.

Medically intractable epilepsy may be treated successfully with surgery in a high proportion of patients following appropriate clinical and diagnostic evaluation. Recent technical advances provide more precise diagnostic methods, especially for localizing the areas of seizure origin in the cerebral cortex. The excision of epileptogenic cortex remains the main surgical treatment for partial forms of epilepsy, while commissurotomies are appropriate for some patients with a secondary, generalized type of epilepsy. Limited experience with a variety of stereotaxic lesions and the modality of cerebellar stimulation has not yet provided definite evidence of efficacy of these techniques. Following surgical excisions, two thirds of the patients are significantly improved and over one third become seizure free, with morbidity-mortality rates of less than 0.5%.

Cerebral Cortex↗
PubMed1986

Reproductive endocrine disorders in women with partial seizures of temporal lobe origin.

Of 50 consecutive women with partial seizures of temporal lobe origin (temporal lobe epilepsy [TLE]) evaluated for reproductive dysfunction, 28 had menstrual problems. Of those, 19 had reproductive endocrine disorders. Polycystic ovarian syndrome and hypogonadotropic hypogonadism occurred significantly more often in women with TLE than in the general female population. Polycystic ovarian syndrome was associated with predominantly left-sided lateralization of interictal epileptic discharges; hypogonadotropic hypogonadism was more commonly found with right-sided discharges. Hyposexuality occurred more often in women with predominantly right-sided interictal epileptic discharges and was associated with low serum luteinizing hormone levels. There are several possible interpretations: epileptic discharges in medial temporal limbic structures may disrupt hypothalamic regulation of pituitary gonadotropin secretion; anovulatory cycles of reproductive endocrine disorders may promote the development of epileptic discharges; and TLE and some associated reproductive endocrine disorders may represent the parallel effects of prenatal factors common to the development of the brain and the reproductive system.

Adult↗
PubMed1986

Reproductive endocrine disorders in men with partial seizures of temporal lobe origin.

Twenty consecutive men with partial seizures of temporal lobe origin were evaluated for sexual or reproductive dysfunction. Eleven (55%) had diminished sexual interest or reduced potency. Nine of them had reproductive endocrine disorders, with features of hypogonadotropic hypogonadism in five, hyperprolactinemia in two, and hypergonadotropic hypogonadism in two. Among these nine were cases in which the reproductive endocrine abnormalities could not readily be attributed to antiseizure medication use. Other possible interpretations are as follows: epileptic discharges in medial temporal lobe structures may disrupt hypothalamic regulation of pituitary secretion, hypogonadism may promote the development of epileptic discharges, and temporal lobe epilepsy and associated reproductive endocrine disorders may represent the parallel effects of prenatal factors common to the development of both the brain and the reproductive system.

Adult↗
PubMedDate not supplied

Phenytoin-induced elevation of serum estradiol and reproductive dysfunction in men with epilepsy.

Reproductive and sexual dysfunction in men with epilepsy has been attributed to androgen deficiency. Low serum free testosterone (FT) levels occur in both hypogonadotropic and hypergonadotropic hypogonadism. Antiepileptic drugs (AEDs) have been implicated. Proposed mechanisms include induction of increased sex hormone binding globulin (SHBG) resulting in decreased FT, as well as dysfunction or premature aging of the hypothalamopituitary-gonadal axis. In an investigation comparing serum reproductive steroid levels among 20 men receiving phenytoin (PHT) monotherapy for complex partial seizures, 21 untreated men with complex partial seizures, and 20 age-matched normal controls, total estradiol levels were significantly higher in the PHT group (56.3 +/- 29.4 pg/ml, mean +/- SD) than in the untreated (32.4 +/- 27.4 pg/ml, p less than 0.01) and normal control (34.3 +/- 12.7 pg/ml, p less than 0.05) groups. The physiologically active non-SHBG-bound serum estradiol levels were also significantly higher in the medicated group (45.1 +/- 21.7 pg/ml) than in the untreated (29.9 +/- 17.2 pg/ml, p less than 0.01) and normal control (31.1 +/- 11.4 pg/ml, p = 0.05) groups. These findings suggest that PHT may lower FT by induction of aromatase, enhancing FT conversion to estradiol, as well as SHBG synthetase. Estradiol exerts a potent inhibitory influence on luteinizing hormone secretion and has been suggested to play a major role in negative feedback in men as well as women. Suppression of LH secretion results in hypogonadotropic hypogonadism. Chronically low FT leads to testicular failure and hypergonadotropic hypogonadism. Finally, estradiol has been shown to produce premature aging of the hypothalamic arcuate nucleus, which secretes gonadotropin-releasing hormone.

Adult↗