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Biomedical subjects

R P Lesser

Publications and source records attributed to R P Lesser.

At least 55 records · Page 3Linked to original sources
PubMed1986

Cortical potentials related to voluntary and passive finger movements recorded from subdural electrodes in humans.

Movement-related potentials were recorded from subdural electrodes placed on the precentral and postcentral cortex in 3 patients undergoing operation for intractable epilepsy. With self-initiated index finger movement, a negative potential of 25 to 50 microvolts in amplitude, preceding onset of the electromyographic activity by 60 to 95 ms (or onset of movement by 150 to 230 ms), was recorded from the hand somatosensory postrolandic area in all 3 patients. A similar potential preceding the movement was recorded from the precentral hand motor area in one subject who was the only patient in whom the precentral electrodes were placed on the hand motor area. Following active and passive movements, a clearly defined positivity (18 to 32 ms after a photometer trigger) that reversed phase across the central fissure was recorded. The premovement potentials are most probably generated by pyramidal tract neurons and motor-function-related neurons located in the post- and prerolandic areas. The postmovement positivity is most probably due to short-latency kinesthetic reafferent activation of the posterior bank of the central fissure (equivalent to P2 of the somatosensory evoked potentials).

Brain Mapping↗
PubMed1986

The value of closely spaced scalp electrodes in the localization of epileptiform foci: a study of 26 patients with complex partial seizures.

Twenty-seven patients with complex partial seizures were studied electrographically utilizing a large number of closely spaced scalp electrodes around the epileptogenic focus. Skull roentgenograms were made with the electrodes in place in order to relate the electrode positions to underlying brain anatomy. Field distribution maps were constructed from reference montages employing the closely spaced electrode set. Electrodes other than 10-20 were maximal most often and the single electrodes most often maximal were D9-D10, anterior temporal in location. This method of localization is of help in the evaluation of patients with complex partial seizures who may be surgical candidates.

Adolescent↗
PubMed1986

Four dichotic speech tests before and after temporal lobectomy.

Thirty patients were tested with four dichotic speech tests before and after temporal lobectomy for control of intractable seizures. Ipsilateral ear scores improved on all tests postoperatively; these improved scores reached statistical significance for the Staggered Spondaic Word Test and for consonant-vowel syllables. This result, combined with a nonsignificant decrease for contralateral ear scores, produced postoperative increase in the ipsilateral minus contralateral ear difference scores, similar to previous literature. Preoperative tests for a larger group of patients showed significantly poorer performance than for normal subjects, for all four tests. Total correct scores, used as a measure of overall auditory processing capacity, were impaired for these patients, but unchanged or slightly improved after surgery.

Adolescent↗
PubMed1986

Mental deterioration in epilepsy.

A variety of factors could potentially influence the occurrence of mental deterioration in epilepsy, including seizure type, age of seizure onset, seizure duration, and seizure severity. The available literature suggests that measures of severity are more predictive of progressive decreases in intellectual functioning. There is also evidence suggesting that seizure severity and cognitive deterioration might both be the result of underlying pathophysiologic abnormalities in some cases. In the majority of patients with epilepsy, however, with relatively less severe disease, there is little evidence for cognitive deterioration. Total seizure number also has an inverse correlation with level of psychosocial functioning in some studies, whereas others have found that patients with emotional difficulties have fewer seizures. In the case of emotional deterioration, the impact of interpersonal relationships and other environmental factors upon psychosocial outcome seems clear, and the evidence for specific pathophysiologic explanations for emotional deterioration, less convincing.

Adult↗
PubMed1986

Basal temporal language area demonstrated by electrical stimulation.

We report on a 38-year-old patient with intractable complex partial seizures originating in the dominant left medial temporal region. In the work-up for seizure surgery, arrays of subdural electrodes were placed, and electrical stimulation revealed marked language interference in a 2 X 2-cm area in the left basal temporal fusiform gyrus (3.5 to 5.5 cm posterior to the temporal tip). Complete receptive and expressive aphasia, inability to repeat, agraphia, and alexia were elicited, but visual memory was preserved, and no constructional apraxia was noted. Stimulation of the basal temporal gyrus at lower stimulus intensities produced a relatively selective and severe anomia.

Adult↗
PubMed1986

The lateralizing significance of versive head and eye movements during epileptic seizures.

We studied 37 patients who had head and eye turning during 74 spontaneous epileptic seizures. Videotapes and EEGs were analyzed independently. Turning movements were classified without knowledge of EEG or clinical data as either versive (unquestionably forced and involuntary, resulting in sustained unnatural positioning) or nonversive (mild, unsustained, wandering, or seemingly voluntary). Videotape observations were then correlated with the EEG location of seizure onset. Contralateral versive head and eye movements occurred during 61 seizures in 27 patients, but ipsilateral versive movements did not occur. Nonversive lateral head and eye movements occurred ipsilaterally and contralaterally with equal frequency and were nonlocalizing, but versive movement was a reliable lateralizing sign.

Adolescent↗
PubMed1986

Electrical stimulation of Wernicke's area interferes with comprehension.

Arrays of subdural electrodes were placed over the lateral convexity of the dominant hemisphere for propositional language in four patients with epilepsy as part of an evaluation prior to cortical resections. Stimulation was performed over several days. When we stimulated the posterior temporal language area, reading and comprehension of complex verbal information were impaired, but comprehension of nonverbal and simple verbal data was not affected. Impairment produced by stimulation seemed to be due to language comprehension difficulties, rather than impaired praxis or initial word storage.

Adolescent↗
PubMed1986

Memory for objects presented soon after intracarotid amobarbital sodium injections in patients with medically intractable complex partial seizures.

We evaluated the abilities of 36 patients with intractable temporal lobe epilepsy and left hemisphere dominance for language to later recognize objects presented in the confusional phase after left intracarotid amobarbital injection. Eighteen of 24 patients with left, but only 4/12 with right, temporal lobe epilepsy recognized at least two-thirds of objects during a post-test. These results demonstrate that the initial muteness and apparent confusion after amobarbital injection do not prohibit the formation of new memories; this gives further support to the idea that consciousness can be retained despite transient disruption of function of the language-dominant hemisphere.

Adolescent↗
PubMed1986

Ipsilateral forced head and eye turning at the end of the generalized tonic-clonic phase of versive seizures.

We studied 61 spontaneous seizures in 27 epileptic patients with simultaneous EEG and video recording. Each seizure had an initial forced turning (versive) head and eye movement contralateral to the EEG location of seizure onset. Twelve of the 27 secondarily generalized versive seizures also had ipsilateral head and eye version at the end of the generalized convulsion. Initial contraversion and late ipsiversion both appeared to result from ictal activation of frontal contraversive areas in the hemisphere that, at the time, was predominantly involved in the seizure discharge. During initial contraversion, ictal activation was predominant in the hemisphere of seizure onset; during late ipsiversion, in the hemisphere involved by secondary generalization. Late version, unlike initial version, is frequently ipsilateral and cannot be assumed to indicate seizure onset in the contralateral hemisphere.

Adolescent↗
PubMed1986

Intraoperative spinal somatosensory evoked potential monitoring.

The relationship of intraoperative monitoring of spinal cord somatosensory evoked potentials and postoperative deficit in 220 cases (121 with scoliosis, 41 with neoplasms, and 58 others) is reported. Bilateral posterior tibial nerve stimulation was used in 181 cases and unilateral median nerve stimulation in 39. Spinal cord (interspinous ligament needles), subcortical (neck surface), and cortical (scalp surface) SEP's were monitored. Seven patients had worsening of neurological function after surgery, three of whom demonstrated significant changes in SEP's monitored. In an additional four cases, there was more than a 50% decrease in amplitude of subcortical/cortical SEP's during monitoring, but no change in neurological status postoperatively. Combined monitoring of spinal cord, subcortical, and cortical SEP's enhanced the certainty of detecting spinal cord dysfunction even though there was a significant number of false-negative and false-positive results. A marked change in the SEP's indicated a high chance of developing a neurological deficit (three or 43% of seven cases), and if there was no change the chance of any neurological postoperative deficit was extremely low (four or 1.87% of 213 cases). These data justify the use of intraoperative SEP monitoring.

Adolescent↗
PubMed1986

Effect of etomidate on the electroencephalogram of patients with epilepsy.

Etomidate was given intravenously to 12 epileptic patients undergoing craniotomy for surgical removal of their seizure focus. Electroencephalograms were recorded by means of subdural electrodes. Nine of the 12 patients showed an increase in epileptiform activity. In six of the nine patients, the activity was marked.

Adolescent↗
PubMed1985

The second sensory area in humans: evoked potential and electrical stimulation studies.

A patient with intractable seizures originating from a right frontal focus was evaluated for surgical treatment. This evaluation was carried out using a chronically implanted array of 96 stainless steel electrodes 1 cm apart and covering the perirolandic and frontal areas. Somatosensory evoked potentials and electrical stimulation of the subdural electrodes localized the primary sensory hand area. Evoked potentials of identical waveform but of lower amplitude and 2.4 ms longer latency were recorded in the inferior frontal gyrus immediately anterior to the face area of the motor strip. Electrical stimulation of that area elicited: (1) a "paralyzing" feeling in the left arm and face; (2) inhibition of rapid alternating movements of left fingers, left hand, and tongue; (3) inability to maintain a strong voluntary muscle contraction of the left hand or tongue; and (4) speech arrest. This appears to be the first report of a secondary sensory area in humans demonstrated by both electrical stimulation and evoked potential studies. Electrical stimulation showed that the secondary sensory area overlapped an area of complex motor control, suggesting that the secondary sensory area provides direct sensory feedback information for appropriate motor integration.

Adult↗
PubMed1985

Choosing an antiepileptic drug. The case for individualized treatment.

The range of drugs available for seizure control is broad, but selection of the drug and the dosage most likely to be effective for an individual patient is complex. In general, drug choice is determined by type of seizures involved and total daily dosage is based on milligrams per kilogram, so that plasma levels for all patients can be easily interpreted. Optimal seizure control is often possible with use of a single drug; in fact, in most patients with epilepsy, single-drug therapy is more effective than multiple-drug therapy and more desirable.

Adolescent↗
PubMed1985

Optimizing stimulating and recording parameters in somatosensory evoked potential studies.

Methods to increase the signal:noise ratio of evoked potentials are reviewed, dividing them into three groups: (1) increasing the number of stimuli averaged; (2) decreasing the noise (muscle relaxation, filters, intermittent artifact reject methods); and (3) increasing the amplitude of the signal (stimulus intensity, nerves stimulated, bilateral versus unilateral stimulation, stimulus modality, and montage). Examples of these different methods applied to recording of somatosensory evoked potentials are given, and it is concluded that, for optimal recording of somatosensory evoked potentials, a combination of all these methods should be used.

Electric Stimulation↗