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Biomedical subjects

D A Shewmon

Publications and source records attributed to D A Shewmon.

At least 37 records · Page 2Linked to original sources
PubMed1992

The persistent vegetative state in children: report of the Child Neurology Society Ethics Committee.

Increasing concern about children in a persistent vegetative state (PVS) prompted a survey of members of the Child Neurology Society regarding aspects of the diagnosis and management of this disorder. Major findings of those responding to this survey (26% response rate) were as follows: (1) 93% believed that a diagnosis of PVS can be made in children, but only 16% believed that this applied to infants younger than 2 months and 70% in the 2-month to 2-year group; (2) a period of 3 to 6 months was believed to be the minimum observation period required before a diagnosis of PVS could be made; (3) 86% believed that the age of the patient would affect the duration of time needed to make the diagnosis of PVS; (4) 78% thought a diagnosis of PVS could be made in children with severe congenital brain malformations; (5) 75% believed that neurodiagnostic studies would be of value and supportive of the clinical diagnosis of PVS; (6) members' opinions as to the average life expectancy (in years) for the following age groups after the patients were considered vegetative were: newborn to 2 months, 4.1; 2 months to 2 years, 5.5; 2 to 7 years, 7.3; and more than 7 years, 7.4; (7) 20% believed that infants and children in a PVS experience pain and suffering; and (8) 75% "never" withhold fluid and nutrition from infants and children in a PVS and 28% "always" give medication for pain and suffering.(ABSTRACT TRUNCATED AT 250 WORDS)

Advisory Committees↗
PubMed1992

Treatment of infantile spasms: medical or surgical?

Although infantile spasms were initially described in 1841, remarkably little progress has been made in understanding the pathophysiology of this "peculiar form of infantile convulsions." Consequently, our ability to treat infantile spasms is limited. Infantile spasms are classified as a "generalized" seizure disorder in the international classification system, which suggests that the underlying brain abnormality causing the seizures also must be diffuse or generalized. As the classification suggests, there are many diffuse, or multifocal, brain disorders related to infantile spasms, e.g., inborn errors of metabolism, hypoxic-ischemic brain injury, and developmental brain defects such as tuberous sclerosis or Aicardi's syndrome. On the other hand, infantile spasms have been reported in which a localized brain abnormality was present, e.g., tumor, stroke, and trauma. On rare occasions, removal of a tumor has resulted in cessation of the generalized infantile spasms. This finding suggests that focal cortical abnormalities can cause infantile spasms and that removing the abnormality can stop the seizures. At University of California, Los Angeles, the Pediatric Epilepsy Surgery Program has developed new approaches to the treatment of infantile spasms. The principal underlying concepts are (a) children with medically refractory infantile spasms may have an area of cortical defect (called the zone of cortical abnormality) that causes the seizures and (b) infantile spasms are usually generalized seizures. Thus, the goal of the surgical assessment is not the identification of the focus of seizure onset but rather the identification of the zone of cortical abnormality.

Adrenocorticotropic Hormone↗
PubMed1992

Temporal and extended temporal resections for the treatment of intractable seizures in early childhood.

In our series of 33 children who underwent temporal and extended temporal lobe resections because of seizures, the average age at surgery was 7 years, 11 months. Sixteen cases (48%) were diagnosed as having tumors: low-grade astrocytoma (6), hamartoma (5), and ganglioglioma/neuroma (5). Other pathologic diagnoses included one or more cytoarchitectural abnormalities and/or reactive changes. Due to a more aggressive and early radiologic and electrophysiologic investigation of children with seizures, a resectable focus, e.g. neoplasm or structural abnormality, was found in a much younger age group of patients than previously reported. In children who had intractable seizures but normal radiologic studies, positron emission tomography was of great value in localizing the seizure focus. In a group of children with infantile spasms, seizures were controlled following the identification and resection of a focal lesion. Prompt detection and precise localization of lesions in the temporal lobe in the pediatric population may lead to surgical management and seizure control.

Adolescent↗
PubMed1992

Intractable seizures, compulsions, and coprolalia: a pediatric case study.

A 10-year-old girl with intractable complex partial seizures developed aphasia, coprolalia, and repetitive motor behaviors involving touching, sexual touching, and aggressive acts. Her symptoms subsided following surgical resection of a left anterior temporal lobe ganglioglioma and control of seizures. Possible neurobehavioral implications of the reversibility of this patient's symptoms are discussed.

Brain Neoplasms↗
PubMed1990

Infantile spasms: I. PET identifies focal cortical dysgenesis in cryptogenic cases for surgical treatment.

Positron emission tomography (PET) of local cerebral glucose metabolism in 13 children with infantile spasms of undetermined cause (cryptogenic spasms) revealed unilateral hypometabolism involving the parieto-occipito-temporal region in 5 female infants. Cranial computed tomography showed normal findings in all infants. Magnetic resonance imaging (MRI) demonstrated a normal appearance in 4 of the 5 infants; in 1 infant, MRI revealed a subtle abnormality consisting of poor demarcation between occipital gray and white matter. Surface electroencephalography (EEG) in 4 showed hypsarrythmia at some time in the patients' courses, but at other times showed localized or lateralized abnormalities corresponding to areas of PET-detected hypometabolism. Because of poor seizure control, 4 infants underwent surgical removal of the cortical focus guided by intraoperative electrocorticography and were seizure free postoperatively. Neuropathological examination of resected tissue in each showed microscopic cortical dysplasia. Our findings indicate that in infants with cryptogenic spasms, PET can effectively identify those due to unsuspected focal cortical dysplasia, for which resective surgery offers improved prognosis.

Cerebral Cortex↗
PubMed1990

What is a neonatal seizure? Problems in definition and quantification for investigative and clinical purposes.

Despite the clinical and basic scientific importance of neonatal seizures, a standard operational definition of them is lacking. Virtually all quantitative studies of phenomenology, prevalence, treatment efficacy, and prognosis have been undermined by inadequate or inconsistent criteria for the object of investigation. This is not so much a fault of the studies, however, as a consequence of the very nature of neonatal seizures themselves, which seem to defy universally applicable definitions and criteria for quantification. The main obstacles to formulating such definitions are reviewed, and directions for further research are suggested.

Electroencephalography↗
PubMed1989

Transient impairment of visual perception induced by single interictal occipital spikes.

We have previously reported that focal occipital interictal epileptiform discharges (spikes) cause transiently prolonged reaction time (RT) and increased nonperception of stimuli, especially in the visual field contralateral to the spike. One subject with very frequent spikes was capable of carrying out a visual recognition task along with the RT task. During central fixation, computer-generated random digits were flashed for 150 ms at random locations on a screen. Some stimuli were delivered during spikes, by means of an amplitude-threshold trigger, whereas control stimuli were delivered at random times between spikes. Following each stimulus, the subject had to press a button for RT and then report the digit perceived. There was a statistically significant increase in nonresponse rate (nonperception) during spikes compared to controls, and this effect was maximal contralateral to the spike. Moreover, among the responses, perceptual accuracy (correct vs incorrect) was significantly impaired during spikes, again predominantly in the visual field contralateral to the spike. Thus, not all focal interictal spikes are necessarily "subclinical;" at least some induce a transient cortical dysfunction of the same kind as produced more enduringly from a structural lesion in the same location. These findings may have clinical relevance in patients, especially children, with very frequent epileptiform discharges and higher cortical dysfunction.

Action Potentials↗
PubMed1989

Early prognosis in anoxic coma. Reliability and rationale.

As desirable as it might be to predict early in the course of coma whether a patient will do well or poorly, all studies of coma prognosis are plagued by inherent methodologic problems that tend to diminish the utility of the derived criteria: especially the tendency of poor prognoses to be self-fulfilling, the rapid drop-off in patient population due to death from nonneurologic causes, and the need to lump, for the sake of statistical significance, outcome categories that ought to be kept distinct for purposes of ethical decision making. Even for a methodologically ideal study, if 100 per cent of the N patients fulfilling a particular criterion experienced the same poor outcome, the probability of a false prediction of poor outcome in the next patient meeting that criterion is approximately 1/(N + 2), which is hardly negligible for a realistically sized study. Moreover, there is a 50 per cent chance of at least one false-positive prediction among the next (N + 1) patients fulfilling the criterion. Given this inherent unreliability of early predictors for individual patients, given that decisions to continue life support are reversible, whereas decisions to withdraw it are usually not, and given that the death of a patient with potential for recovery is a more serious error than the (typically) transient prolongation of life of a patient destined soon to die anyway or (much less commonly) to remain in a chronic vegetative state, it would seem prudent to continue life support for all patients during the first few weeks or months of coma or vegetative state, regardless of early indicators of poor outcome. Early prognostication can still serve other useful purposes, however, including the counseling of families, triage and DNR decisions, and future clinical investigations of brain-resuscitative measures.

Coma↗
PubMed1988

Focal spike-induced cerebral dysfunction is related to the after-coming slow wave.

By means of a computerized system of spike detection, presentation of visual stimuli, and registration of reaction times (RTs), we have shown previously that focal posterior interictal spikes cause transiently prolonged RT and increased nonperception and misperception of stimuli, especially contralateral to the spike. We report here the temporal profile of this phenomenon, ascertained by systematically increasing a delay between spike and stimulus-flash, until the latter was well beyond the limits of the entire spike-wave complex. In each of two subjects, the spike effect began just before the spike and ended with the termination of the after-coming slow wave. For stimuli with identical delays following spikes, RTs were significantly prolonged if the end of the slow wave overlapped the stimulus, and not otherwise. In one subject, who had an amplitude dissociation between spikes and after-coming slow waves, the prolongation of RT was associated with the larger waves, regardless of spike amplitude. These findings suggest that the after-coming slow wave (surround hyperpolarization) transiently disrupts aspects of cortical functioning, in addition to whatever effect the spike itself may have. Focal spike-wave-induced cortical dysfunction may be relevant to a variety of interictal cognitive disorders.

Adult↗
PubMed1988

The effect of focal interictal spikes on perception and reaction time. I. General considerations.

The effect of focal interictal spikes on visual perception and reaction time (RT) was studied in 3 subjects, by means of a computerized system of spike detection, presentation of visual stimuli, and timing of a button press. A total of 8646 such trials were analyzed, comparing spike-locked and control performances within the same subject. For stimuli locked to spikes involving visual cortex, both the rate of non-responses (non-perceptions) and the RTs of responses were increased (P less than 0.0001) in all 3 subjects. The magnitude of this effect was roughly proportional to the amplitude and breadth of field of the spike. Focal spikes in cortical areas uninvolved in the visual motor task did not impair performance. These findings indicate that single focal interictal spikes transiently disrupt aspects of cortical functioning, at least in the few subjects studied so far. This may have developmental and therapeutic implications for patients with very frequent interictal spikes, even thought they may not have seizures or their seizures may be well controlled.

Action Potentials↗
PubMed1988

The effect of focal interictal spikes on perception and reaction time. II. Neuroanatomic specificity.

By means of a computerized system of spike detection, presentation of visual stimuli, and timing of a button press, we showed previously that single posterior interictal spikes resulted in transient prolongation of reaction time and increased non-response rate in 3 subjects. By varying the response hand and the visual field of stimulus, conditions with maximum spike effect were defined more precisely, in relationship to the location of the spike. In general, spike-induced dysfunction was most pronounced when either response hand or visual field of stimulus was contralateral to the spike. This not only was true across all 3 subjects, but held even for independent right and left occipital spikes within the same subject. Also, perceptual versus motor aspects were differentially affected by the anterior-posterior location of the spike. These findings indicate that focal interictal spikes may transiently disrupt aspects of cortical functioning corresponding to their neuroanatomical location.

Action Potentials↗
PubMed1988

Surgical treatment of intractable neonatal-onset seizures: the role of positron emission tomography.

We have performed positron emission tomography (PET) with 2-deoxy-2[18F]fluoro-D-glucose (FDG) in eight infants and children (aged 18 days to 5 years) with medically refractory epilepsy of neonatal onset. It was hypothesized that in at least some of these infants a surgical approach (focal resection, cerebral hemispherectomy) might be of benefit in achieving seizure control, and that PET might assist in surgical selection. In three of the eight subjects, interictal PET revealed unilateral diffuse hypometabolism; following cerebral hemispherectomy in these three patients, all seizures ceased and there were no adverse effects. In one child, ictal PET showed hypermetabolism in the left frontal cortex, left striatum, and right cerebellum; a partial left cerebral hemispherectomy guided by intraoperative electrocorticography was performed, following which all seizures ceased. One infant had relative hypermetabolism in the right temporal and occipital lobes, right thalamus, and left frontal lobe on ictal PET, and EEG telemetry revealed a right occipitotemporal epileptic focus; this infant died from anesthetic complications following right occipitotemporal cortical resection. Of the three unoperated patients, one is a potential candidate for right frontal lobectomy, but the other two were not considered to be surgical candidates due to bilateral epileptogenicity. Neuropathologic correlation in our series revealed that PET is a sensitive test capable of detecting cytoarchitectural disturbances whereas CT and MRI failed in this regard. In addition, PET provides a very unique and important assessment of the functional integrity of brain regions outside the area of potential resection.

Brain↗
PubMed1986

Infantile spasms. Comparative trial of nitrazepam and corticotropin.

Fifty-two patients were enrolled in a four-week randomized multicenter study comparing nitrazepam and corticotropin in the treatment of infantile spasms. The drugs' efficacy was evaluated in 48 patients, all less than 2 years of age. Both treatments resulted in a statistically significant reduction in spasm frequency from that at baseline, but the difference between treatments was not significant. The number of patients who experienced side effects was similar in the two treatment groups, but the adverse effects encountered among the patients treated with corticotropin were qualitatively more severe and required the discontinuation of treatment in six patients.

Adrenocorticotropic Hormone↗