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Biomedical subjects

K R Winston

Publications and source records attributed to K R Winston.

At least 37 records · Page 2Linked to original sources
PubMed1991

Hydraulic regulation of brain parenchymal volume.

A mechanism for the hydraulic regulation of brain parenchymal volume is hypothesized. Ventricular fluid pressure is transmitted to parenchymal capillaries and affects the pressure difference across the capillary wall, thereby influencing the rate of movement of fluid from the capillary lumen to interstitial fluid. The tendency for brain parenchyma to expand results from the resistance encountered by interstitial fluid as it slowly passes through the complex interstices of extracellular space. The tendency for the brain parenchyma to become smaller results, not from compression of tissue by ventricular fluid, but from an inherent elasticity of brain tissue. The parenchymal volume is stable only when the opposing tendencies are balanced. The critical site of action for the hydraulic control of parenchymal volume is the capillary wall, and the fundamental relationship governing this can be expressed mathematically.

Body Water↗
PubMed1990

Ectopic pituitary adenoma of the third ventricle. Case report.

Ectopic pituitary adenomas without associated intrasellar adenomas are rare and are usually located in the sphenoid sinus. Most have been reported without modern radiological, endocrinological, or electron microscopic (EM) documentation. The case of a 47-year-old man with a third ventricular, ectopic, clinically nonsecretory pituitary adenoma, which was shown to be a gonadotrophic adenoma by immunohistochemical and EM study, is reported. Neurological examination, extensive neurodiagnostic imaging, surgical anatomical observation, and endocrinological evaluation showed no evidence of neoplasia outside the third ventricle.

Adenoma↗
PubMed1990

Craniopharyngiomas in children. Long-term effects of conservative surgical procedures combined with radiation therapy.

Thirty-seven patients with craniopharyngioma were treated at Children's Hospital, Boston, between 1972 and 1981, the mean follow-up period now being 10.5 years. Twenty of these patients are old enough to have finished high school and have been queried about their college or job activity. None of the four patients who had undergone radical excision of their tumor and who had reached the age of finishing high school was able to work independently. Among the 16 patients who reached this age and who were treated by more conservative operations and irradiation or irradiation alone, job performance or college attendance varied considerably, indicating that psychosocial impairment occurred in this group, but suggesting that the risk was less. The rate of tumor recurrence or of failure to respond to treatment was 57% (four of a total of seven survivors) following radical surgery and 7% (two of 27 survivors) after conservative operations and irradiation. The overall mortality rate was 8%; the causes of the three deaths were: "hypothalamic crisis" 1 year after radical resection; progressive tumor growth despite two attempts at resection and irradiation; and a brain-stem glioma in the field of irradiation 8 years after treatment.

Child↗
PubMed1989

Stereotactic radiosurgery for intracranial arteriovenous malformations using a standard linear accelerator.

We have previously described the development of a technique which utilizes a standard linear accelerator to provide stereotactic, limited field radiation. The radiation is delivered using a modified and carefully calibrated 6 MV linear accelerator. Precise target localization and patient immobilization is achieved using a Brown-Roberts-Wells (BRW) stereotactic head frame which is in place during angiography, CT scanning, and treatment. Seventeen arteriovenous malformations (AVMs) have been treated in 16 patients from February 1986 to July 1988. Single doses of 1500-2500 cGy were delivered using multiple non-coplanar arcs with small, sharp edged x-ray beams to lesions less than 2.7 cm in greatest diameter. The dose distribution from this technique has a very rapid dropoff of dose beyond the target volume. Doses were prescribed at the periphery of the AVMs, typically to the 80-90% isodose line. Eleven of 16 patients have been followed by repeat angiography at least 1 year following treatment. Five of 11 have had complete obliteration of their AVM in 1 year and an additional three patients have achieved complete obliteration by 24 months. There have been no incidences of rebleeding or serious complications in any patient. We conclude that stereotactic radiosurgery using a standard linear accelerator is an effective and safe technique in the treatment of intracranial AVMs and the results compare favorably to the more expensive and elaborate systems that are currently available for stereotactic treatments.

Adolescent↗
PubMed1989

Tumors of the choroid plexus in children.

Primary neoplasms of the choroid plexus in children are surgically treatable, and the encouraging results of surgical removal, even for carcinoma, justify an aggressive surgical approach. Forty cases operated on over a span of 45 years have been reviewed in detail, including a rereading of all microscopic slides. The prognosis for children with papilloma has been excellent. The 5-year survival rate for children with carcinoma of the choroid plexus was 50%, and all deaths occurred within 7 months of operation. The patients whose carcinomas were totally removed had a better prognosis than did those with subtotal removal.

Adolescent↗
PubMed1988

Group B streptococcal infections of the central nervous system in infants with myelomeningocele.

Three cases of group B streptococcal infection of the central nervous system (CNS) occurred among 147 neonates treated for myelomeningocele at The Children's Hospital in Boston from 1970 to 1985. This pathogen was responsible for one third of the nine CNS infections noted in these patients over the 15-year study period. All three children with group B streptococcal CNS infections subsequently required multiple CNS shunting procedures and prolonged hospitalizations. Two children suffered major neurological sequelae. In neonates with myelomeningocele, group B streptococci have direct access to the CNS, perhaps explaining the high incidence of serious meningitis and ventriculitis in this population. Antibiotic prophylaxis for early myelomeningocele repair should be adjusted accordingly.

Central Nervous System Diseases↗
PubMed1988

Pre-radiation chemotherapy for infants and poor prognosis children with medulloblastoma.

Beginning in 1984, we started a prospective study to evaluate the role of postoperative, pre-radiation chemotherapy in the treatment of infants and poor prognosis children with medulloblastoma. The study was designed to evaluate the role of pre-radiation chemotherapy in two specific patient populations: (a) children under the age of 2 years in which there was an attempt to delay definitive radiation and thus reduce the risk of toxicity to the developing nervous system; and (b) children over age 2 years with Stage T3 and T4 disease who were known to have a relatively poor prognosis with surgery and radiation. The five patients under age 2 years received cisplatinum (100 mg/m2) every 3 weeks and weekly vincristine (1.5 mg/m2) for a total of 9 weeks. Nitrogen mustard (6 mg/m2), procarbazine (100 mg/m2), and vincristine (1.5 mg/m2) (MOP) were given in 28 day cycles as long as there was no disease progression or until the child's second birthday, at which time the children were referred for radiation therapy. The 13 patients over 2 years of age received the 9 week course of cisplatinum and vincristine and then began radiation. Responses measured by computed tomography were obtained in 10 of 12 children with measurable disease at the start of chemotherapy. With a median follow-up of 22 months, 15 of 18 children were alive and free of disease. Except for mild ototoxicity in one child, the acute side effects have been well tolerated. In conclusion, it appears that some infants can have their radiation delayed until the age of 2 years. Although the follow-up time was short, all but three patients were free of disease, time exceeding the median time to failure with radiation alone. Pre-radiation chemotherapy might improve local control and survival in children with advanced stage medulloblastoma.

Adolescent↗
PubMed1988

A system for stereotactic radiosurgery with a linear accelerator.

A small field irradiation technique to deliver high doses of single fraction photon radiation to small, precisely located volumes (0.5 to 8 cm3) within the brain has been developed. Our method uses a modified Brown-Roberts-Wells (BRS), CT-guided, stereotactic system and a 6 MV linear accelerator equipped with a special collimator (diameters of 12.5 mm to 30.0 mm projected to isocenter) located 23 cm from isocenter. Target localization via planar angiography has been added. Treatment consists of a series of arcing beams using both gantry and couch rotations. During treatment, the patient's head is immobilized independently of the radiotherapy couch and is precisely positioned without reference to room lasers or light field. A precise verification of alignment precedes each treatment. Extensive performance tests have shown that a target, localized by CT, can be irradiated with a positional accuracy of 2.4 mm in any direction with 95% confidence. If angiography is used for localization, the results are better. The dose 1.0 cm outside the target volume is less than 20% of the prescribed dose for a medium sized collimator.

Brain Neoplasms↗
PubMed1988

Neurourological implications of the changing approach in management of occult spinal lesions.

Occult lesions of the spine in children are a rare but recognizable cause of neurogenic dysfunction involving the lower extremities, and lower urinary and gastrointestinal tracts. We report the preoperative and postoperative urodynamic findings in 40 children with varying spinal abnormalities. Of these patients 28 were neonates or infants (average age 8.7 months) and 12 were older children (average age 11.7 years). Preoperative urodynamic testing revealed normal function in 18 of 28 children (64 per cent) in the younger age group in contrast to 1 of 12 (8 per cent) in the older age group. Of the 10 infants with abnormal studies postoperative urodynamic findings returned to normal in 6, while 2 others remained abnormal but were improved. In contrast, of 11 older children with abnormal preoperative evaluations 3 (27 per cent) reverted to normal postoperatively. The neurourological changes seen in these occult lesions are variable, may occur at any age, are progressive and are potentially reversible by surgical correction but this reversibility diminishes with age.

Adolescent↗
PubMed1988

Radiosurgery for arteriovenous malformations of the brain using a standard linear accelerator: rationale and technique.

We have recently initiated a program for irradiating small, unresectable arteriovenous malformations (AVM's) in the brain. The treatments are delivered using a modified and carefully calibrated 6 MV linac. We are using high, single doses (15 to 25 Gy) with a goal of sclerosing the vessels and preventing hemorrhages. This technique, radiosurgery, is somewhat controversial in the radiotherapy community. Since the treatment is given in a single sitting, rather than in the more conventional pattern of multiple small daily fractions, there is some concern about late radiation damage to the normal brain tissue. However an extensive review of the literature leads us to the conclusion that if a technique is used that keeps the volume irradiated to high dose small, radiosurgery is a safe and efficacious treatment for small (less than 2.5 cm) AVM's. To decrease the risk of necrosis of normal brain tissue, it is important to confine the high dose region as tightly as possible to the target volume. Precise target localization and patient immobilization is achieved using a stereotactic head frame which is used during angiography, CT scanning, and during the radiation treatment. This minimizes the margin of safety that must be added to the target volume for errors in localization and set-up. The treatment is delivered using multiple noncoplanar arcs, with small, sharp edged X ray beams, and with the center of the AVM at isocenter. This produces a rapid dropoff of dose beyond the target volume. Early results in our first few patients are encouraging.

Humans↗
PubMed1988

Linear accelerator as a neurosurgical tool for stereotactic radiosurgery.

A new system has been developed for stereotactically delivering prescribed high doses of radiation to precisely located volumes of approximately 0.6 to 10.0 ml within the brain. A Brown-Roberts-Wells stereotactic apparatus and a 6-MeV linear accelerator equipped with a special collimator (12.5 to 30 mm in diameter) have been adapted. The 20-mm collimator allows treatment of a nearly spherical volume of 2.1 ml. Outside the treatment field, the dosage declines to 80% of the dose prescribed for the periphery of the lesion over a distance of 1.8 mm and to 50% over the next 3.4 mm. Localization can be accomplished via computed tomography or cerebral angiography. Treatment is accomplished with an arcing beam of photon radiation with the turntable (couch) in each of four positions. The entire system has been extensively tested for accuracy in alignment and distribution of radiation. Errors have been measured for the alignment of the apparatus and for the process of localization. Safety of operation was emphasized throughout the design and testing phase.

Brain Diseases↗
PubMed1988

Hydrocephalus and intraspinal tumor.

Hydrocephalus with spinal subarachnoid obstruction is rare, and its cause is obscure. Two such patients are presented. The pathophysiology is reviewed. Spinal absorptive pathways for cerebrospinal fluid are postulated to play a critical role in such cases.

Aged↗
PubMed1988

Treatment of scaphocephaly with sagittal craniectomy and biparietal morcellation.

A series of 50 consecutive patients with scaphocephaly treated by a new operation are reported, and the results are reviewed in detail. The treatment consists of a broad sagittal craniectomy plus extensive morcellation of both parietal bones and, occasionally, the squamous portion of the occipital bone, without dislodging the bony fragments from their dural attachments. The procedure can be done relatively rapidly (median operative time = 55 min) and with minimal loss of blood (median transfusion = 85 ml). The results are analyzed by several criteria and are considered to be excellent.

Blood Transfusion↗
PubMed1988

Effect of preoperative shampoos with chlorhexidine or iodophor on emergence of resident scalp flora in neurosurgery.

Wound contamination with endogenous bacterial scalp flora plays an important role in the pathogenesis of postoperative neurosurgical infections. To assess the effect of preoperative antiseptic shampoos on the emergence of resident scalp flora during surgery and subsequent wound contamination, we randomized 151 neurosurgical procedures into four study groups: group A--preoperative shampoos with chlorhexidine, surgical scalp preparation with chlorhexidine; group B--no shampoos, surgical preparation with chlorhexidine; group C--shampoos with iodophor, surgical preparation with iodophor; group D--no shampoos, surgical preparation with iodophor. Quantitative cultures of the scalp were obtained preoperatively and at the end of surgery, and qualitative wound cultures were taken prior to wound closure. Group A had the lowest concentration of bacteria on the scalp both preoperatively and postoperatively (median range = 30 [0-5.7 x 10(5)] and 0 [0-2.5 x 10(3)] respectively). Group A also had significantly fewer positive postoperative scalp cultures (29%) than groups B (51%), C (58%), and D (53%) (P less than 0.05), as well as fewer positive wound cultures (20% v 25%, 42%, and 30% respectively). A density of bacteria on the scalp of greater than 10(2)/4cm2 best predicted the presence of bacteria in the wound. Repeated preoperative shampoos with chlorhexidine reduce intraoperative emergence of resident skin flora and subsequent contamination of the wound.

Adolescent↗
PubMed1987

The changing neurourologic lesion in myelodysplasia.

Seventy-nine newborns with myelodysplasia were followed up for 1 1/2 to six years with serial roentgenographic, neurologic, and urodynamic evaluations. Twenty-nine infants (37%) demonstrated changes in external urethral sphincter innervation during the first three years of life. Of the group who changed, 896% (25/29 infants) did so in the first year, 10% (3/29 infants) in the second year, and 4% (1/29 infants) in the third. The risk factor for change was 32%, 6%, and 2%, respectively, during each of these three years. Fifteen infants (19% of the total) experienced neurourologic deterioration while 14 infants (18%) improved. Seven newborns underwent a second neurosurgical procedure resulting in improvement in four, stabilization in two, and further deterioration in one. These findings underline the importance of early and continued neurologic and urologic surveillance in children with myelodysplasia because it is a dynamic disease process.

Electromyography↗
PubMed1987

Brain tumors after cranial irradiation for childhood acute lymphoblastic leukemia. A 13-year experience from the Dana-Farber Cancer Institute and the Children's Hospital.

Brain tumors developed in two children after they had received cranial irradiation as central nervous system therapy for acute lymphoblastic leukemia. A review of the literature demonstrated an increased incidence of brain tumors in survivors of acute lymphoblastic leukemia who received central nervous system irradiation. Most of the brain tumors occurred within a decade after radiotherapy. Further data will be required to determine whether early post-radiation brain tumors in patients with acute lymphoblastic leukemia are due to the central nervous system irradiation or to a genetic predisposition.

Adolescent↗