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Biomedical subjects

R M Scott

Publications and source records attributed to R M Scott.

At least 73 records · Page 4Linked to original sources
PubMed1996

Immunohistochemically identifiable tissue plasminogen activator in cavernous angioma: mechanism for re-hemorrhage and lesion growth.

The mechanisms governing growth of cavernous angiomas of the brain and their propensity to hemorrhage remain unknown. Repetitive hemorrhage with neovascularization during clot organization and maturation of new vessels into a larger cavernous angioma has been hypothesized as one mechanism. This hypothesis is largely based on the histopathological similarity between the organizing clot surrounding cavernous malformations and the organizing phase of the membranes surrounding chronic subdural hematoma. The presence of tissue plasminogen activator (TPA) in the vascular endothelium of vessels contained within chronic subdural membranes has been used to argue that an intrinsic thrombolytic process is responsible, in part, for rebleeding within chronic subdural cavities. By analogy, we sought to identify whether TPA is located in tissues in and around cavernous angiomas. Cavernous malformations, surgically removed and pathologically confirmed by standard staining techniques, were immunohistochemically stained for TPA. Eleven of thirteen lesions (85%) studied contained vascular endothelial cells which stained for TPA. Of the 2 lesions which did not contain TPA, 1 was non-hemorrhagic and calcified; 7 of 11 (64%) lesions which contained TPA presented clinically with hemorrhage. These data support the hypothesis that a local thrombolytic process may be responsible for the frequent hemorrhagic nature of cavernous angiomas. Alternatively, since local elaboration of TPA is common to both chronic subdural membranes and cavernous angiomas, this finding may represent a more global characteristic of fibrinolytic homeostasis in cerebral tissues.

Adolescent↗
PubMed1996

Jugular foraminal stenosis in Crouzon syndrome.

We describe a 4-year-old boy with Crouzon syndrome, with associated acanthosis nigricans and Chiari-I malformation, who developed increased intracranial pressure necessitating posterior cranial expansion. Postoperatively, an arteriovenous fistula appeared over the mastoid region. Cerebral angiography demonstrated bilateral atresia of the jugular veins and occlusion of the left sigmoid and right transverse sinuses. We propose that increased intracranial venous pressure, secondary to bilateral jugular foraminal stenosis, caused hydrocephaly and venous dilation in the scalp vasculature. The latter set the stage for a traumatic arteriovenous fistula of the scalp, probably resulting from laceration of an adjacent artery and vein. Jugular atresia is a basilar malformation common to achondroplasia and certain eponymous syndromic craniosynostoses. Our patient has a mutation in fibroblast growth factor receptor 3, a different locus in the same gene mutated in achondroplasia.

Acanthosis Nigricans↗
PubMed1996

Moyamoya and Down syndrome. Clinical and radiological features.

BACKGROUND AND PURPOSE: Moyamoya disease is a chronic occlusive cerebrovascular disorder characterized by progressive stenosis of the supraclinoid internal carotid artery, with the secondary development of enlarged basal collateral vessels. It may occur as a primary disease or as a syndrome in association with a variety of conditions, and its pathogenesis remains unexplained. There are relatively few reports describing the occurrence of moyamoya in Down syndrome. The aim of this study is to describe the clinical and radiological features of moyamoya syndrome associated with Down syndrome (MM-DS) and to explore theories of moyamoya pathogenesis in these patients. METHODS: Seven children with MM-DS underwent brain imaging, transfemoral angiography, and serial neurological exams. Neurological deficits, poststroke recovery, radiographic infarct characteristics, and angiographic abnormalities were reviewed. RESULTS: The clinical and radiological features of primary moyamoya disease overlap with those of MM-DS. Hemiplegia and aphasia were the most common presentations. Motor recovery was excellent in five of seven cases. Cerebral infarcts were superficial or deep and can occur in a watershed distribution. Angiography demonstrated involvement of the internal carotid artery and its branches bilaterally in all seven cases and the posterior cerebral arteries in four cases. CONCLUSIONS: The clinical and radiological features of MM-DS overlap with primary moyamoya disease. We postulate that a protein encoded on chromosome 21 may be related to the pathogenesis of moyamoya disease. Although the neuronal substrate is abnormal in Down syndrome patients, recovery from hemiplegic stroke in patients with MM-DS is comparable to recovery in patients with primary moyamoya.

Adolescent↗
PubMed1996

Acquired cerebral arteriovenous malformation in a child with moyamoya disease. Case report.

The authors report a unique case involving a 2-year-old child with idiopathic moyamoya disease who presented with cerebral infarctions and seizures. On initial evaluation, computerized tomography (CT) showed a left parietal infarct and angiograms demonstrated early moyamoya disease with no evidence of arteriovenous malformation (AVM). Approximately 9 years later, angiography and magnetic resonance (MR) imaging revealed an AVM centered on the same region of the left parietal lobe. Angiographic, CT, and MR images are presented that demonstrate the progression of moyamoya disease and de novo development of the AVM in the infarct site. The possible role of angiogenesis in the etiology of acquired AVMs and moyamoya disease is discussed.

Cerebral Angiography↗
PubMed1995

Nonrandom chromosomal gains in pilocytic astrocytomas of childhood.

Low-grade astrocytomas are the most common central nervous system (CNS) tumor occurring in the pediatric age group. Although many of these tumors are karyotypically normal, various studies have reported gains of chromosomes in a significant proportion of cases. We have the opportunity to karyotype two pilocytic astrocytomas occurring in 5- and 15-year-old children. These tumors were characterized by stemlines of 49,XY,+4,+7,+8 and 48,XX,+7,+8. Using these patients as index cases and based on additional karyotypic data that have been published, we performed fluorescence in situ hybridization on 25 additional cases of low-grade astrocytomas in children using pericentromeric probes for chromosomes 4, 6, 7, 8, 9, 10, 11, 12, 15, and 17. Six of 18 (excluding the two index cases), or one third, of the pilocytic astrocytomas were characterized by chromosomal gains, most commonly chromosomes 7 and 8, suggesting that trisomy 7 and 8 are relatively common events in the tumorigenesis of pilocytic astrocytomas. In contrast, chromosomal trisomies were not detected in seven well-differentiated fibrillary astrocytomas with any of the probes chosen.

Adolescent↗
PubMed1995

Nitrous oxide depresses the H-reflex in children with cerebral palsy.

Hoffmann's reflex or H-reflex (HR) is an electrically elicited reflex that measures excitability of motoneurons and shares some physiologic properties with the deep tendon reflex. Children with tendon hyperreflexia due to cerebral palsy usually have higher amplitude HRs. Nitrous oxide (N2O) depresses the HR in patients with normal spinal reflexes, although the effect of N2O in conditions with hyperreflexia such as cerebral palsy is not known. We propose to determine the effect of N2O on the amplitude of the HR under general anesthesia in children with hyperreflexia due to cerebral palsy. We studied eight children undergoing selective dorsal rhizotomy (SDR) for the relief of spasticity. The maximum amplitudes of the HR (HRmax) and direct motor response (MRmax) were routinely evoked under the following anesthetic conditions: 1) sufentanil and 66% N2O/33% oxygen; and 2) sufentanil and 100% oxygen. The HRmax amplitude was significantly lower when N2O was part of the inspired gas mixture. The differences between the no N2O and the 66% N2O groups were significant. The MRmax did not change significantly. Abnormal spinal reflexes seen in spastic diplegia can be abolished by inhaled N2O. This finding also suggests that N2O-induced depression of spinal reflexes should be a consideration during physiologic monitoring of the spinal cord under general anesthesia.

Cerebral Palsy↗
PubMed1995

Pial synangiosis for moyamoya syndrome in children.

The authors describe a modification of the encephalo-duro-arterio-synangiosis (EDAS) surgical technique for patients with moyamoya syndrome in which the arachnoid is widely opened over the exposed brain and the donor superficial temporal artery adventitia is sutured directly to the pia with 10-O nylon suture ('pial synangiosis'). The procedure has been performed in 34 patients over a 10-year period, with follow-up arteriograms 1 year following the procedure demonstrating markedly enhanced middle cerebral artery flow through the surgical site. Operative morbidity has been limited to two postoperative strokes, both in patients who were neurologically unstable preoperatively; and the clinical stability of the operated patients has thus far been excellent.

Adolescent↗
PubMed1995

Neurophysiologic assessment of urinary dysfunction in children with thoracic syringomyelia.

Isolated syringomyelia of the thoracic portion of the spinal cord is relatively uncommon. In children, signs and symptoms may involve only the urinary system. Five children who presented for evaluation of urinary tract dysfunction were found to have syringomyelia of the thoracic cord not associated with any other central nervous system abnormality on radiographic imaging. Each child underwent a complete neurologic examination and a complete electrophysiologic/urodynamic evaluation. One patient underwent surgical drainage of the syrinx due to progression of neurologic deficit, with slight improvement; three patients were treated pharmacologically to control the urinary dysfunction.

Child↗
PubMed1994

Stereotactic radiotherapy for pediatric and adult brain tumors: preliminary report.

PURPOSE: Stereotactic radiotherapy is a new modality that combines the accurate focal dose delivery of stereotactic radiosurgery with the biological advantages of conventional radiotherapy (1.8-2.0 Gy/day using 25-30 fractions). The modality requires sophisticated treatment planning, dedicated high-energy linear accelerator, and relocatable immobilization devices. We report here our early experience using stereotactic radiotherapy for intracranial neoplasms. METHODS AND MATERIALS: Between June 1992 and September 1993, we treated 82 patients with central nervous system lesions using stereotactic radiotherapy, delivered from a dedicated 6 MV stereotactic linear accelerator. A head fixation frame provided daily relocatable setup using a dental plate for all patients over 8 years of age. A modified head frame, which does not require a mouthpiece, was used for children requiring anesthesia. The patients ranged in age from 9 months to 76 years. Thirty-three patients were children less than 21 years of age. Selection criteria for the protocol included: (a) focal, small (< 5 cm) radiographically distinct lesions known to be radiocurable (pituitary adenoma, craniopharyngioma, meningioma, acoustic neuroma, pilocytic astrocytoma, retinoblastoma), and (b) lesions located in regions not amenable to surgery or radiosurgery such as the brain stem or chiasm. Standard fractionation and conventional doses were delivered. Patients with low-grade astrocytoma, oligodendroglioma, or ependymoma were treated using a dose escalation regime consisting of conventional doses plus a 10% increase. RESULTS: Although follow-up is 16 months (range 3-16 months), posttreatment radiographic studies in 77 patients have been consistent with changes similar to those found after conventional radiation therapy. To date, reduction of up to 50% of the original volume has been noted in 19 out of 77 patients, and 4 patients had a complete response, 2 with dysgerminoma, and 1 each with astrocytoma and retinoblastoma. In 56 patients disease was either stable or the follow-up was too short for evaluation. While the follow-up is relatively short, there have been no in-field or marginal recurrences. The only unexpected radiographic findings were in three patients with pilocytic astrocytomas, who developed asymptomatic edema in the treatment volume. Accuracy in daily fractionation was excellent. In over 2000 patient setups with 41,000 scalp measurements, reproducibility was found to be within 0.41 mm (median) of baseline readings, allowing for precise immobilization throughout the treatment course. The treatment in all cases was well tolerated with minimal acute effects. Our stereotactic radiotherapy facility can provide fractionated therapy for 10-12 patients a day efficiently and accurately. CONCLUSIONS: The treatment and relocatable stereotactic head frames were well tolerated with minimal acute effects. No long-term sequelae have been noted, although the observation period is short. To fully define the role of stereotactic radiotherapy, we are conducting prospective studies to evaluate neurocognitive and neuroendocrine effects. We expect that this innovative approach will make a significant impact on the treatment of intracranial neoplasms, particularly in children.

Adolescent↗
PubMed1994

Microvessel count and cerebrospinal fluid basic fibroblast growth factor in children with brain tumours.

Tumour growth is angiogenesis-dependent; brain tumours have more intense neovascularisation than other tumours and produce basic fibroblast growth factor, a potent angiogenic mediator. Because little is known about the release of basic fibroblast growth factor from brain tumours into extracellular fluids, we tested cerebrospinal fluid (CSF) from 26 children and young adults with brain tumours and 18 controls for basic fibroblast growth factor and for proliferative activity on cultured capillary endothelial cells. We also measured the density of microvessels in tumours by immunohistochemical staining. Basic fibroblast growth factor was detected in the CSF of 62% (16 of 26) patients with brain tumours but in none of the controls. Specimens with basic fibroblast growth factor stimulated DNA synthesis of capillary endothelial cells in vitro. Endothelial proliferative activity was blocked by neutralising antibodies to basic fibroblast growth factor. Basic fibroblast growth factor correlated with mitogenic activity in CSF in vitro (p < or = 0.0001), and with density of microvessels in histological sections (p < or = 0.005). A microvessel count of > or = 68 per 200 x field was associated with tumour recurrence (p = 0.005) and with mortality (p = 0.02). Basic fibroblast growth factor in brain tumours may mediate angiogenesis as measured by microvessel density in histological sections, so has potential as both a marker for neoplasia and a target for tumour treatments. Furthermore, evaluation of cerebrospinal fluid basic fibroblast growth factor, along with microvessel quantitation in biopsied tumours, may provide improved prognostic information for the management of patients with brain tumours.

Adolescent↗
PubMed1994

H reflex studies in cerebral palsy patients undergoing partial dorsal rhizotomy.

H reflex studies were performed in ten spastic children with cerebral palsy who underwent partial dorsal rhizotomy (PDR). Under anesthesia prior to PDR, H reflex amplitude evoked by percutaneous peripheral nerve stimulation gradually declined in all patients and became unobtainable in five. Motor responses could still be evoked by apparent dorsal root stimulation in these five, but since it was shown that they were M responses and not reflexes, PDR was performed randomly. In the other five patients, in whom H reflexes were still evokable, dorsal root stimulation evoked motor responses which were true reflex responses, and PDR was performed "selectively." Compared to preoperative values, postoperative Hmax/Mmax ratios declined, but no more so in selective than in random PDR. We conclude that current intraoperative methods for selection of "abnormal" dorsal rootlets for section may be invalid and may have no bearing on successful outcome, since spasticity improves even with random PDR.

Analysis of Variance↗
PubMed1994

A framework for the evaluation of vaccines for use in the expanded programme on immunization.

Since 1974, the Expanded Programme on Immunization (EPI) has provided technical support for the immunization of the world's children and women of childbearing age. Today, the vast majority of vaccines administered to these groups are delivered through the immunization programmes that have been established in developing countries. As these national programmes share many characteristics, the global use of a new or improved vaccine could be largely dependent on its compatibility with the priorities, existing antigens and vaccine delivery system of this network. Consequently, a framework has been developed for the systematic evaluation of candidate vaccines for use in EPI.

Adult↗