Biomedical subjects
Publications and source records attributed to S J Schneider.
A newborn presented with a cerebral ganglioglioma. This is a rare diagnosis in a neonate. The imaging appearance (hyperdense on CT, hyperintense on T1-weighted and hypointense on T2-weighted MRI) is very unusual for this type of tumor.
The long-term outcome of 75 children who underwent methyl methacrylate cranioplasty over a 15-year period is presented. Forty-two patients underwent cranioplasty for posttraumatic skull defects and 33 for nontraumatic causes. Within 8 years following initial cranioplasty procedure, a total of 17 (23%) complications occurred. Several factors correlated with the development of complications, including postoperative radiotherapy, the size of the defect, involvement of the frontal sinus, and the presence of prior infection. The authors currently recommend avoiding methyl methacrylate cranioplasty in selected patients who have received postoperative radiation therapy, in patients with large cranial defects, involvement of the frontal sinus, or any history of prior infection.
Radical surgery is the most important treatment modality for ependymoma. The benefit of adjuvant radiotherapy and/or chemotherapy following a gross total resection of a low grade intracranial ependymoma is uncertain. Since 1990 we elected to defer adjuvant therapy in 7 pediatric patients with a median age of 7 years (range 3-16 years) who had a radical resection of an intracranial ependymoma and no evidence of central nervous system metastases. The primary tumor site was the cerebral hemisphere (6) and the cerebellum (1). A gross total resection was radiologically confirmed in 5 of the 7 patients. Two of the patients had a blood clot in the resection site on the postoperative magnetic resonance imaging scan. All patients are alive after a median follow-up of 44 months and the median progression-free survival is 38+ months. Five of the patients remain in continuous remission. The 2 patients with postoperative blood clots developed subclinical local recurrences, 10 and 11 months, respectively, after diagnosis. They remain in remission for 13+ and 27+ months after subsequent radical surgical procedures. Involved field radiotherapy was administered to 1 patient. After a limited period of follow-up, radical surgery alone appears to be sufficient for the majority of children with low grade ependymomas diagnosed at > 3 years of age when postoperative imaging confirms a gross total resection. This is more likely to occur in supratentorial ependymomas arising in older children.
OBJECTIVE AND IMPORTANCE: Intracranial shunts are commonly placed in children and frequently require replacement during the child's growing years. Severe signs of increased intracranial pressure often are the first indication of shunt displacement and malfunction. Subtle neuro-ophthalmic signs in children are usually overlooked. CLINICAL PRESENTATION: Two cases are described in which homonymous hemianopsia resulted from unsuspected movement of the shunt catheter in growing children. In one male patient, the catheter tip impaled the optic tract, and in the other male patient the shunt became embedded in the midbrain tegmentum and shunt failure led to compression of the posterior cerebral artery. INTERVENTION: In the presence of optic atrophy, papilledema may go unnoticed without serial examinations. This stresses the importance of detecting other early warning signs of shunt displacement and increased intracranial pressure, including visual field changes and subtle abnormalities of motility. CONCLUSION: Because early diagnosis and shunt revision may allow visual recovery, children with shunts should be followed with visual fields and serial disc photographs.
This study was conducted to investigate the relationship between the indicators of psychiatric disorders of individuals and their choice of either cocaine or heroin, drugs that differ markedly in their pharmacological effects. Cocaine acts as an intense stimulant, and heroin has profound sedative effects. This investigation examined the relationship between preference for heroin or cocaine and indicators of psychiatric impairment. Data from 282 subjects were grouped according to drug of choice and analyzed. Ninety-three percent of these subjects were African-American, 32% were female, and the average age was 34. Univariate and multivariate statistical analyses, such as discriminant analyses, were used to determine group differences. The results are evaluated and interpreted in relation to both the current empirical findings and to the hypotheses and theories postulated as a result of earlier clinical observations on drug of choice and psychopathology. Discriminant analysis yielded an overall correct classification rate of 75%. The discriminant function suggests that members in the cocaine drug of choice group as contrasted with members in the heroin preference group can be characterized as more socially inhibited and more self-defeating after adjusting for differences in age, duration of use of illicit substances, and marital status. Those who favored cocaine as contrasted with those who favored heroin were more likely to have never married, be younger, and have used illicit substances for a shorter period of time.
Neurological deterioration in the tethered cord syndrome has been postulated to result from a compromise of blood flow in the distal spinal cord. In order to evaluate vascular perfusion in human subjects, a new technique of laser-Doppler flowmetry was used to monitor continuously the microcirculation of the distal spinal cord during surgery for tethered cord release in 10 children. For further comparison, five children undergoing selective dorsal rhizotomy were also monitored. In the tethered cord syndrome group, spinal cord blood flow before untethering was a mean of 12.6 ml/min per 100 g of tissue and increased in all cases after release to a mean of 29.4 ml/min per 100 g of tissue. All patients improved neurologically. The selective dorsal rhizotomy group had a preoperative mean spinal cord blood flow of 30.8 ml/min per 100 g of tissue, which was not altered by the operative procedure. Significant improvement occurs in distal spinal cord blood flow after tethered cord release, which may be representative of an important mechanism in the pathophysiology of the tethered cord syndrome.
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A stress management program that used computerized, telephone-based technology was offered to the public via a free, "800" telephone number. The program was intended to reach a very large number of persons, while requiring a minimum of staff time. The program used an interactive telephone system, employing natural sounding, digitized voice, and touch tone recognition of callers' responses. The program was available 24 hours a day. It composed each message to suit the individual needs and expectations of each caller. A controlled evaluation of the program was conducted to determine how the messages could be worded and presented most effectively. The results suggest that subjects were most likely to find the messages in the program helpful, to carry out the stress management instructions, and to continue calling when the messages were personalized and contained homework assignments.
The lambdoid phages are a group of related temperate bacteriophages that lysogenize by site-specific recombination with the bacterial chromosome. Various members of the group have different specific chromosomal insertion sites, despite the fact that the enzymes catalyzing the insertion (integrases) appear to be all descended from a common ancestor. Insertion sites are not located randomly on the E. coli chromosome but are restricted to one segment of the map; also, most prophages are oriented in the same direction along the chromosome. Lambdoid phage 21 inserts within the isocitrate dehydrogenase gene and introduces an alternative 165 bp 3' end for that gene. A defective element (e14) inserts at the same position. We suggest that this mode of insertion arose from insertion of an ancestral phage to the right of icd which then picked up part of the icd gene by abnormal excision and speculate that, at an earlier time, phages may have arrived at their present locations by a process of chromosomal walking.
Twenty children with vein of Galen malformations and hydrocephalus required a ventriculoperitoneal shunt. Shunt placement was associated with a 70% incidence of complications that included status epilepticus in 3 patients, intraventricular hemorrhage in 7 patients, and subdural hematoma or hygroma in 5 patients. Based upon this experience, the authors recommend the use of preoperative prophylactic anticonvulsants and the placement of medium pressure frontal ventriculoperitoneal shunts. This report will address the overall experience with and the basis on which these therapeutic recommendations were made.
The echographic characteristics of 186 suspected intramedullary spinal cord tumors were reviewed. Ultrasonography was found to be specific in distinguishing the tumor type, the extent of the lesion, and the presence and type of associated cysts. Ultrasonography greatly facilitates the selection of respective sites for the placement of a myelotomy, and for initiation of the resection. Additionally, this indispensable adjunct provides ongoing images that allow the preoperative plan to be precisely followed in a surgical field where anatomical landmarks are limited and the margin for error is minimal.
Comparison of the nucleotide sequence of the integrase genes of lambdoid phages 21 and 434 with the published sequences of phages HK022 and lambda shows that lambda and 434 are very closely related (98% base sequence identity), whereas HK022 and 21 respectively show 73% and 48% identity to lambda. It is likely that several homologous recombination events occurred in the int gene and flanking DNA among the progenitors of these phages. Sequence divergence to different alternative sequences at a common site (tL4) suggests that tL4 has been repeatedly used as a recombination site, despite the very limited homology it provides. A minor constitutive transcript that terminates at tL4 of lambda has been identified. We propose that the principal selective force acting to conserve tL4 is for terminator function, but that the use of tL4 as a recombination site has allowed the formation of selectively favored recombinants. By extension, we suggest that conservation of microhomologies at functional sites serves to keep lambdoid phages within a common gene pool despite extensive drift and divergence.
A case of transdural herniation of a cervical disk is presented. The diagnosis was most clearly established by magnetic resonance imaging. The literature is reviewed and possible mechanisms of transdural herniation are discussed.
Two cases of posterior lumbar vertebral rim fracture and associated disc protrusion in adolescents are presented. Disc compliance and developing vertebral structure were thought to be primarily responsible for this unusual injury. Occurring primarily in adolescent males, this entity most commonly affects the L-4 vertebra. One of the cases involved disc rupture at three levels. This injury is thought to be due in part to union of the anuli by the posterior longitudinal ligament, and in part to rim fracture and limited prolapse rather than frank single-level herniation in an adolescent. A review of the embryology, literature, and theoretical mechanism for occurrence at multiple levels is included.
Melanotic neoplasms of the spinal nerve root are rare but well-documented occurrences. The authors report the case of a 68-year-old woman with a malignant melanotic neoplasm containing premelanosomes and melanosomes and lacking a basal lamina. This tumor was found in a lumbar nerve root and is believed to represent an instance of a primary melanoma arising in a spinal nerve root. The differential diagnosis of pigmented lesions of spinal nerve root includes melanoma, pigmented nerve sheath tumor, blue nevus, melanotic clear-cell sarcoma, and meningeal melanocytoma. Surgeons should be aware of the potential for encountering unexpected malignant lesions involving spinal nerve roots.
Computer conferencing has become popular as an alternative to face-to-face conferencing in many kinds of organizations. Since users can participate at any time, from any terminal, computer conferencing makes communication very convenient, though many find the medium to be impersonal. This paper discusses the potential of computer conferencing to increase the number of people who participate in self-help groups, such as groups to help people lose weight or stop smoking. The kinds of interactions that make for successful self-help groups might be encouraged by a computer-conferencing format, even though there is no direct, face-to-face contact. The results of a trial smoking-cessation program which employed computer conferencing suggest that computer conferencing could play a useful role in health promotion.
Smoke, a computer program written in BASIC, uses interactive direct mail to assist smokers who do not wish to attend formal face-to-face smoking cessation therapy. The effectiveness of the program was evaluated in a yearlong study. Of 1044 smokers who expressed interest in smoking treatment, only 11.2% wished to participate in formal therapy. The rest received mail-based treatment. A total of 21.2% of the subjects who were assigned to the computerized direct mail group participated in this treatment. The abstinence rates of the participants in the computerized direct mail and face-to-face groups were similar. The results suggest that computerized direct mail could be a useful addition to smoking cessation campaigns.
Data from a smoking cessation program were analyzed to identify the variables that best predicted posttreatment abstinence. Nonsmoking immediately following treatment was predicted by lower daily pretreatment intake of nicotine and total particulate matter (TPM), as well as higher score on the "handling" scale of the "Why Do You Smoke" scale. Abstinence at any time in the 6 months following treatment was also predicted by lower pretreatment nicotine and TPM intake; other predictors were lower scores on the "craving" scale, greater number of weeks spent participating in the program, citing reasons for wanting to quit smoking other than to overcome an addiction, and lower self-rated craving for cigarettes. Abstinence was not predicted by subjects' adherence to the treatment rules calling for changing the times, occasions and feelings that are associated with the heaviest smoking. Daily cigarette consumption dropped during treatment at similar rates for the smokers who would eventually be abstinent and those who would not. These results replicate the finding that a behavioral self-control program can bring about a reduction in smoking in many smokers, though relatively few actually quit smoking. Also, smokers who find the manipulations involved in smoking to be rewarding are more likely to be abstinent, at least temporarily, following a behaviorally oriented program than are smokers who are most rewarded by the self-administration of nicotine. Smoking cessation programs might benefit by tailoring treatment to such pretreatment subject characteristics.