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Biomedical subjects

R Abbott

Publications and source records attributed to R Abbott.

At least 55 records · Page 3Linked to original sources

Introduction of a second working portal for neuroendoscopy. A technical note.

The introduction of a second portal during endoscopic procedures in presented. This second portal allows passage of larger instruments while the surgical field is viewed with an endoscope placed through the first portal. This dual portal technique provides an angled view of the operative site, thus avoiding optical obstruction by tissue being pulled toward the endoscope. We report the use of this technique in 6 endoscopic cases.

Adolescent↗

Intrinsic tumors of the medulla: predicting outcome after surgery.

Twenty-four children and young adults who underwent surgery for intrinsic tumors of the medulla were studied, correlating preoperative symptoms to postoperative brain stem dysfunction. 75% harbored benign tumors with a mean survival of 3.6 years, while the remaining 25% with anaplastic tumors had a mean survival of 3.2 years. Six patients required postoperative ventilatory support for an extended period of time, and 9 required feeding gastrostomies. Those patients who experienced frequent symptoms of upper respiratory tract infection, preoperative pneumonia, or an alteration in their voice were at risk of postoperative ventilatory dependency. Those without such symptoms did not experience such a fate. Difficulty in swallowing food or liquids seems to predict the need for postoperative feeding gastrostomies, and a lack of such a history was correlated with no such need 100% of the time. There seem to be preoperative signs and symptoms which predict postoperative brain stem dysfunction for an extended period of time in those undergoing brain stem surgery for tumors intrinsic to the medulla.

Adolescent↗

Sensory rhizotomy for the treatment of childhood spasticity.

Sensory rhizotomy in the treatment of spasticity has been evolving over the past century since its first use in 1888. This paper reviews its historical evolution, current physiologic basis, range in current surgical technique, and the outcome, along with complications seen over the past decade since its repopularization.

Child↗

Residual spasticity after selective posterior rhizotomy.

The technique used in performing selective posterior rhizotomies to treat spastic cerebral palsy remains controversial. One hundred nine children who had undergone selective posterior rhizotomies were studied 6 months after their surgery. Their residual spasticity was correlated to the number of roots and whether or not abnormally responding roots were left, in order to validate the surgical technique used to treat spastic cerebral palsy at most neurosurgical centers in North America. The children were divided into three groups (group A: children who had their L2-S1 roots tested and selectively lesioned, n = 15; group B: children who had their L2-S2 roots tested and selectively lesioned, n = 62; group C: children who had their L2-S2 roots tested and whose lesioning was directed both by the response to the stimulation and mapping of the S1-S3 dorsal roots for afferent pudendal nerve activity, n = 32). Clinically significant residual spasticity was present in the gastrocnemius in 33% of the group A children, 11% of the group B children, and 6% of the group C children. We found that there was no significant increase in residual spasticity in the group C children when abnormally responding roots were not cut in order to preserve pudendal nerve activity. This study shows that the inclusion of the S2 roots decreases the amount of residual spasticity (P < 0.01). It also shows that leaving abnormally responding S2 roots to preserve pudendal nerve activity does not affect the incidence of postoperative spasticity (P > 0.1).

Adolescent↗

Complications of fourth-ventricular shunts.

Fourth-ventricular shunting is commonly used to treat symptomatic posterior fossa cysts of the Dandy-Walker malformation and trapped fourth ventricle. Although the benefits of this procedure have been widely reported, there is a paucity of data on the pitfalls of posterior fossa shunting in the neurosurgical literature. During the 4-year period from July 1989 to June 1993, we placed fourth-ventricular shunts in 12 patients. Remarkably, 5 patients suffered complications related to posterior fossa catheter placement (42% rate). Three of these patients developed new cranial nerve dysfunction caused by direct injury to the floor of the fourth ventricle, 1 patient suffered an intracystic hemorrhage and acute shunt malfunction, and 1 patient had the catheter tip in the brainstem on postoperative studies without new neurological deficit. We conclude that placement of fourth-ventricular shunts can be fraught with complications which we believe is related to technique. We propose that altering the trajectory of the ventricular catheter from our usual midline technique to a more lateral position will lessen the chances for injury to the floor of the fourth ventricle. In this manner we hope to decrease our incidence of complications for this procedure.

Adult↗

Differential impact of age, sex steroid hormones, and obesity on basal versus pulsatile growth hormone secretion in men as assessed in an ultrasensitive chemiluminescence assay.

A chemiluminescence-based GH assay with 30- to 100-fold increased sensitivity recently disclosed combined basal and pulsatile GH secretion in men. However, how age, sex steroid hormones, and obesity singly and jointly influence the basal vs. pulsatile modes of GH release is not known. We used the foregoing assay (detection threshold, 0.002-0.005 microgram/L) and high sensitivity and specificity (> or = 90% each) deconvolution analysis to quantitate basal and pulsatile GH secretion from 24-h serum GH concentration profiles in 26 healthy lean and obese men, whose ages spanned 18-63 yr and whose percentage body fat ranged from 12-47%. Concentrations of serum insulin-like growth factor I (IGF-I), IGF-I-binding protein-1 (IGFBP-1), and IGFBP-3 were related to specific measures of basal or pulsatile GH release. We observed that mean (24-h) serum GH concentrations embraced a 140-fold range from 0.013-1.8 micrograms/L and were related negatively to age (r = -0.50; P < 0.01), percentage body fat (r = -0.620; P < 0.01), and their interaction (r = -0.610; P < 0.01). In contrast, testosterone was a robustly positive statistical determinant of mean serum GH values (r = 0.628; P = 0.0006). Stepwise multivariate regression analysis disclosed that percentage body fat alone and jointly with the serum testosterone concentration controlled, respectively, 38% and 50% of the total variability in GH levels (P = 0.0013 and P = 0.0008). As assessed by deconvolution analysis, GH secretory burst mass was negatively related to percentage body fat (r = -0.621; P < 0.01) and positively to serum testosterone (r = 0.529; P = 0.0054). The calculated half-life of GH correlated positively with serum estradiol (r = 0.447; P = 0.032), and negatively with percentage body fat (r = -0.437; P = 0.048). Basal GH secretion rates were negatively related to serum estradiol (r = -0.485; P = 0.016). In contrast, GH secretory burst frequency and duration were unrelated to age, percentage body fat, or sex steroids. The fraction of total GH secreted in bursts was negatively correlated with the body mass index (r = -0.540; P < 0.01). Serum IGF-I concentrations were positively related to total pulsatile GH secretion (r = 0.690; P = 0.0011) and negatively to age (r = -0.597; P = 0.007) and percentage body fat (r = -0.611; P = 0.009).(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗

Brain stem mapping: neurophysiological localization of motor nuclei on the floor of the fourth ventricle.

We have improved upon a brain stem mapping technique that can be used to locate cranial motor nuclei on the floor of the fourth ventricle. This technique helped to intraoperatively locate the facial colliculus and the motor nuclei of cranial nerves IX/X and XII in 14 patients undergoing removal of brain stem tumors. The motor nuclei of these cranial nerves are usually located relative to specific anatomic landmarks on the ventricular floor. These landmarks were not evident in most patients studied because of the distorting effects of the tumor. Different points of the floor of the fourth ventricle were electrically stimulated while electromyographic responses were recorded with electrodes inserted in the orbicularis oculi and orbicularis oris muscles, the lateral posterior pharyngeal wall, and the intrinsic muscles of tongue. Mapping was performed before and after tumor resection. The technique was found to be useful for locating cranial motor nuclei before tumor resection. It enabled surgeons to avoid damaging the nuclei when entering the brain stem. This technique, however, has certain limitations. Because this is a mapping technique, not a monitoring technique, continuous monitoring during tumor resection was unavailable. Also, the presence of a muscle response after tumor resection did not always indicate preservation of immediate postoperative function (7 days after surgery) because damage to the corticobulbar tract and/or the underlying neural circuitry was not detectable by mapping. Further research is needed to determine the point of stimulation in the functional motor circuitry and the relationship between intraoperative recordings and postoperative function in the long term.

Adolescent↗

Intramedullary spinal cord lipomas.

Spinal cord lipomas are rare lesions, accounting for approximately 1% of all spinal cord tumors. True intramedullary spinal cord lipomas are extremely rare and are represented in the literature as scattered, single case reports. The authors present a series of six patients with intramedullary spinal cord lipomas managed at our institution from July, 1985 to July, 1993. The patients' ages ranged from 8 to 45 years. Four patients presented with newly diagnosed tumors and two had undergone previous surgery. Patients usually presented with long histories of disability followed by rapid progression of their symptoms. Most patients were in poor neurological condition on presentation. Presenting symptoms included spinal pain, dysesthetic sensory changes, gait difficulties, weakness, and incontinence. Three patients had cervical tumors, two had cervicothoracic tumors, and one patient had a thoracic tumor. Diagnostic studies, including magnetic resonance imaging, were obtained in all patients. No patient exhibited any form of spinal dysraphism or had a dural defect. All patients underwent decompressive, subtotal resections of 40% to 70% of their lesions. Follow-up times ranged from 12 to 96 months. All patients had resolution of their pain, but they generally showed no neurological improvement. As of their most recent follow-up visit, none of the patients was neurologically normal; three can function independently, although with neurological deficits. The other three patients cannot function independently and have severe neurological deficits. The authors conclude that patients with intramedullary spinal cord lipoma who present with significant neurological compromise have a very poor prognosis with regard to neurological function and generally show no improvement with surgical resection.

Adolescent↗

Vitamin A, folate, and iron concentrations in cord and maternal blood of intra-uterine growth retarded and appropriate birth weight babies.

OBJECTIVES: (i) To evaluate the relationship between the levels of vitamin A, folate and iron in maternal blood and cord blood from mother-baby pairs who had intra-uterine growth retardation (IUGR) and appropriate birth weight (ABW) for gestational age. (ii) To assess low or marginal levels of vitamin A, folate and iron as risk factors for IUGR. DESIGN: Retrospective unmatched case-control study. SETTING: Maternidade de Campinas, Universidade Estadual de Campinas, Pontificia Universidade Catolica de Campinas, Hospital Albert Sabin. SUBJECTS: 356 mother-baby pairs who had IUGR and 356 mother-baby pairs who had ABW for gestational age. INTERVENTIONS: Newborns were classified as being IUGR according to the Lubchenco classification. Gestational age of the newborns was evaluated by the Capurro method. Vitamin A, folate, ferritin, and haemoglobin were measured respectively by high performance liquid chromatography (HPLC), radioimmunoassay, immunoenzymetric assay and by the cyanmethaemoglobin method. RESULTS: The percentages of IUGR babies with abnormal levels of nutritional indices compared with ABW babies were 33.1 vs 14.6 for vitamin A, 25.7 vs 19.9 for red blood cell (RBC) folate, 37.0 vs 21.4 for haemoglobin, but similar for ferritin. The percentages of IUGR mothers with abnormal levels of nutritional indices compared to ABW mothers were similar (1.1 vs 1.4) for vitamin A, and 36.8 vs 32.1 for RBC folate. IUGR mothers were less often anaemic (43.2 vs 50.8), but tended to have higher levels of ferritin (37.6 vs 23.9) compared to ABW mothers. CONCLUSIONS: These results indicate marked differences in cord blood between IUGR and ABW with small differences in maternal levels. They suggest that micronutrient deficiency is the result of being born small rather than vice versa. The high levels of ferritin in IUGR mothers may reflect subclinical maternal infection contributing to IUGR. Maternal micronutrient deficiency is unlikely to be a causative factor for IUGR in this population. SPONSORSHIP: ODA (Overseas Development Agency), United Kingdom; CNPq (Conselho Nacional de Desenvolvimento Cientifico e Tecnologico), Brazil.

Birth Weight↗

Survival of split calvarial bone grafts in a dog model.

To gain a better understanding of the strength and long term viability of split calvarial bone graft, nine mongrel dogs each received four trephine craniotomies (1.5 mm diameter). The harvested bone plugs were split through the diploe and a partial-thickness plug was returned to each craniotomy site. The unused partial-thickness plugs underwent strength testing. After 90-150 days the dogs were sacrificed, bone scans and X-rays of the graft recipient sites performed, and the grafted plugs harvested for strength testing and histologic examination. Bone scanning showed increased osteoblastic activity within the grafts, strength testing showed a progressive loss in strength over the 150 days, and histologic examination demonstrated a creeping substitution. These results imply a similar evolution in strength and remodeling to that seen in long-bone grafts, whose remodeling typically spans 1 year.

Animals↗

Concentrations of vitamins A and E in amniotic fluid, extraembryonic coelomic fluid, and maternal serum in the first trimester of pregnancy.

Paired samples of amniotic fluid and coelomic fluid were obtained by transvaginal ultrasound guided amniocentesis from 15 women with an ultrasonographically normal pregnancy between 8 and 12 weeks' gestation. Vitamins A and E were measured in the two pregnancy fluids and in maternal serum by high performance liquid chromatography with detection by ultraviolet absorption and fluorimetry respectively. Concentrations of vitamins A and E were higher in maternal serum than in coelomic fluid and were generally undetectable in amniotic fluid. All differences in concentration were significant. The vitamin E/cholesterol ratio was similar in maternal serum and coelomic fluid. No correlation was shown between the vitamin concentrations in the three fluids. These findings suggest that the coelomic cavity plays a part in the maternofetal exchange of these vitamins.

Amniotic Fluid↗

The use of motor evoked potentials in the diagnosis of psychogenic quadriparesis. A case study.

We present a case illustrating the usefulness of motor evoked potentials (MEPs) in differentiating psychogenic from organic postoperative paralysis. Discussed is a 12-year-old girl who underwent surgery for the repair of a recurrent syringomyelia. On the 6 day after a proximal revision of her syringoperitoneal shunt she returned to the hospital with deep quadriparesis, bowel and bladder incontinence, and complaining of severe headache. An MRI scan showed the syrinx to be collapsed, and removal of the shunt had no impact on her clinical symptoms. Repeat somatosensory evoked potentials (SEPs) showed no change in comparison to those obtained at the end of her preceding surgery. MEPs were normal for the lower extremities, a finding which is inconsistent with a severe upper motor neuron lesion. She was diagnosed with psychogenic paralysis, and fully recovered within 1 month. We propose that a neurophysiological evaluation including MEPs is useful in the differential diagnosis of psychogenic and organic motor weakness.

Child↗

Management of hydrocephalus in children with medulloblastoma: prognostic factors for shunting.

Patients with medulloblastoma frequently present with hydrocephalus. While not all patients with medulloblastoma will continue to suffer from hydrocephalus after tumor resection, there is a significant proportion who will require a permanent shunt. We have retrospectively reviewed a group of children with medulloblastoma not shunted preoperatively, and have identified several characteristics which are associated with a requirement for permanent shunt. We studied 42 patients and found that 17 patients (40%) required permanent shunts within 4 weeks of craniotomy. The shunted patients were younger (5.4 +/- 2.9 vs. 10.0 +/- 5.7 years; p < 0.01), had larger ventricles (p < 0.05), and had more extensive tumors (Chang's stage T3 and T4; p < 0.01). These variables were all independently significant. In addition, we found that the patients requiring postcraniotomy shunts had a much higher rate of morbidity including a postoperative pseudobulbar syndrome. Of interest, we found that none of our patients without the above characteristics required a shunt. In particular, we found that no patient older than 10 years required a shunt. Thus, we conclude that younger patients with moderate to severe preoperative hydrocephalus and extensive tumors may benefit from perioperative CSF diversion. Other patients not meeting the above criteria can probably be safely managed with perioperative corticosteroids alone.

Adolescent↗

Focal tectal tumors: management and prognosis.

A 7-year review at our institution identified 12 children with midbrain tectal tumors. All presented with signs of increased intracranial pressure, had hydrocephalus on initial imaging, and were treated with ventriculoperitoneal (VP) shunts. Three had clinical and radiographic progression of disease. Two were treated with radiation and chemotherapy, with progression of disease in one. The third received radiation alone. All patients are alive, with a median follow-up of over 4 years. Median progression-free survival is at least 24 months and median total survival is beyond 50 months. The tectal glioma syndrome is a relatively benign variant of the brainstem glioma. The majority of patients may be managed with a VP shunt alone.

Adolescent↗

Inclusion of the S2 dorsal rootlets in functional posterior rhizotomy for spasticity in children with cerebral palsy.

Many neurosurgeons have made a practice of sectioning the S2 dorsal roots during selective posterior rhizotomy for the treatment of spasticity in children with cerebral palsy, but the efficacy of this treatment has not previously been proven. S2 afferents are involved in reflex arcs of the plantar flexors (PFs), so that S2 lesioning should in theory reduce PF spasticity. To test this assumption, we determined the frequency of postoperative residual spasticity in the PFs when S2 lesioning was or was not performed. We assessed 85 children for whom 6-month follow-up was available. Functional rhizotomy from L2-S1 was performed on 13 of them (26 legs with PF spasticity) and from L2-S2 on 72 (141 legs with PF spasticity). Rootlets were lesioned if there was an abnormal response to intraoperative electrical stimulation. In 20 patients, lesioning of the S2 rootlets was assisted by the "pudendal neurogram," a technique previously shown to prevent bladder dysfunction during sectioning of the sacral roots. When S2 roots were excluded from the lesioning process, residual PF spasticity was detected in 35% of the legs that had it preoperatively, leaving 5 (38%) of 13 children with functionally impairing spasticity. When S2 roots were included, 6% of legs that had PF spasticity retained it postoperatively (P < 0.001), leaving 8 (11%) of 72 patients with functionally limiting spasticity (P < 0.05). Thus, the addition of the S2 roots to the procedure resulted in an 81% reduction in the number of legs with residual PF spasticity and a 71% reduction in the number of patients with residual PF spasticity.(ABSTRACT TRUNCATED AT 250 WORDS)

Afferent Pathways↗