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Biomedical subjects

P H Chapman

Publications and source records attributed to P H Chapman.

At least 19 recordsLinked to original sources
PubMed2001

The Alexandrian Library: crucible of a renaissance.

At the end of the 4th century BC, the Macedonian-Greek armies of Alexander the Great swept across Asia from Egypt to the Indus River, redefining political boundaries within that vast territory at a time when important cultural changes were also taking place in the Greek world. New literary forms were beginning to emerge from the classical literature, which was then the subject of scholarly investigation. There was growing curiosity about the physical world and mathematics. Aristotle and his contemporaries were redefining scholarship at a time when Alexander was redefining the political sphere. These remarkable transformations converged in Alexandria, which became the center of a new intellectual universe. The first Ptolemaic rulers founded two unique institutions--the Alexandrian Library and the Mouseion--and the Library became the crucible within which the Hellenistic renaissance was forged.

Egypt, Ancient↗
PubMed2001

Temporal clustering of hemorrhages from untreated cavernous malformations of the central nervous system.

OBJECTIVE: Hemorrhages from cerebral cavernous malformations (CMs) sometimes seem to occur in closely spaced "clusters" interspersed with long hemorrhage-free intervals. Clustering of hemorrhages could affect retrospective assessments of radiosurgery efficacy in prevention of CM rehemorrhage. However, this empirical observation had not been tested quantitatively. To test whether CM hemorrhages tend to cluster, we reviewed pretreatment rebleeding rates after a first symptomatic hemorrhage in CM patients who later underwent surgery or radiosurgery. METHODS: We performed a retrospective review of 141 patients with CMs who presented with clinically overt hemorrhage, and who subsequently underwent surgery or proton beam radiosurgery during an 18-year period. Statistical models were used to analyze all events per person and identify potential variation in rebleeding risk with time after a previous hemorrhage. RESULTS: Sixty-three of 141 patients experienced a second hemorrhage before treatment; 16 had additional hemorrhages. Five hundred thirty-eight patient years elapsed between first hemorrhages and treatment. The cumulative incidence of a second hemorrhage after the first CM hemorrhage was 14% after 1 year and 56% after 5 years. During the first 2.5 years after a hemorrhage, the monthly rehemorrhage hazard was 2%. The risk then decreased spontaneously to less than 1% per month, which represents a 2.4-fold decline (P < 0.001). Rehemorrhage rates were higher in younger patients (P < 0.01), but not in females or in patients with deep lesions. Shorter intervals between successive hemorrhages did not predict higher subsequent rehemorrhage risk. CONCLUSION: The rehemorrhage rate from untreated CMs is high initially, and it decreases 2 to 3 years after a previous hemorrhage. This hazard pattern generates the observed temporal clustering of hemorrhages from untreated CMs.

Adolescent↗
PubMed2000

Multimodality treatment of nongalenic arteriovenous malformations in pediatric patients.

OBJECTIVE: Previously reported series of arteriovenous malformations (AVMs) in pediatric patients have primarily used a single-modality treatment approach of either surgery, radiosurgery, or embolization, with significant treatment-related morbidity and mortality. At our institution, we have used a combined multidisciplinary team approach of all three treatment modalities, alone or in combination, to minimize complications and to maximize efficacy in the management of these lesions. METHODS: We retrospectively reviewed 40 consecutive pediatric patients with AVMs seen at our institution from 1991 to 1999. A multidisciplinary team planned the treatment for each AVM. The treatment modality consisted of the following approaches: surgery alone in 14 patients, a combination of endovascular embolization and surgery in 6 patients, radiosurgery alone in 11 patients, a combination of endovascular embolization and radiosurgery in 2 patients, and a combination of radiosurgery and surgery in 2 patients. Four patients are receiving ongoing multistaged treatment for reduction of the nidus size for eventual surgical resection or radiosurgical obliteration of large, complex lesions. In one patient, no treatment was recommended. RESULTS: The clinical outcomes for the overall series were 95.0% excellent or good (Glasgow Outcome Scale score 5 or 4), 2.5% fair (Glasgow Outcome Scale score 3), and 2.5% dead. Radiographic efficacy in the patients who have completed treatment was 92.9% complete obliteration of their AVMs and 7.1% incomplete obliteration. Of the 10 patients who had seizures, 9 are seizure-free. CONCLUSION: A combined multimodality approach of surgery, radiosurgery, and embolization in managing AVMs in pediatric patients can improve outcomes and minimize morbidity and mortality.

Adolescent↗
PubMed2000

An unusual pterygopalatine meningocele associated with neurofibromatosis type 1. Case report.

The authors describe an unusual meningocele of the lateral wall of the cavernous sinus and the anterior skull base in a young patient with typical stigmata of neurofibromatosis Type 1 (NF1). This lesion was discovered during evaluation for recurrent meningitis. It represented an anterior continuation of Meckel's cave into a large cerebrospinal fluid space within the lateral wall of the cavernous sinus, extending extracranially through an enlarged superior orbital fissure into the pterygopalatine fossa adjacent to the nasal cavity. It was successfully obliterated, via an intradural middle fossa approach, with fat packing and fenestration into the subarachnoid space. This meningocele most likely represents a variant of cranial nerve dural ectasia occasionally seen in individuals with NF1. It has as its basis the same mesodermal defect responsible for the more common sphenoid wing dysplasia and spinal dural ectasias identified with this condition. Involvement of the trigeminal nerve with expansion of the lateral wall of cavernous sinus has not been reported previously. The authors surmise, however, that it may be present in some cases of orbital meningocele associated with sphenoid wing dysplasia.

Cavernous Sinus↗
PubMed1999

Role of radiosurgery in the management of central nervous system metastases.

Radiosurgery is being used more routinely to treat patients with inoperable, recurrent, or multiple brain metastases from systemic cancer. Results in > 2000 treated patients have been published during the past 8 years. These results indicate that permanent local control can be obtained in > 80% of treated lesions with complications in < 10% of patients. Success is independent of the histology, ie, melanoma vs adenocarcinoma, of the treated lesion or number of lesions treated. The long-term results of radiosurgery compare favorably with those seen following surgical resection. The cost-effectiveness of radiosurgery compared to surgical resection favors an expanded role for this technology in the treatment of selected patients with brain metastases.

Brain Neoplasms↗
PubMed1999

Stereotactic proton radiosurgery.

The technique of stereotactic proton radiosurgery is discussed in depth in this article. The physics of the proton beam in radiosurgery is explained, and the different factors of beam delivery are examined. These key factors (correspondence to shape, accuracy of delineation of volume, correspondence to volume, and accuracy of delivery vary) with each of the radiosurgical techniques, from Gamma Knife surgery to linear accelerator therapy. Clinical series in the use of proton radiosurgery are also presented, with an emphasis on efficacy and uses.

Biophysical Phenomena↗
PubMed1998

Stereotactic radiosurgery for cavernous malformations: Kjellberg's experience with proton beam therapy in 98 cases at the Harvard Cyclotron.

OBJECTIVE: The lack of treatment options for surgically inaccessible cavernous malformations has made radiosurgery a possible alternative to conservative management. The few previous reports of radiosurgical efficacy have been limited by small numbers, short follow-up, or lack of attention to the full spectrum of end points, including neurological disability. In an attempt to elucidate the risk-to-benefit ratio of radiosurgery for cavernous malformations, we undertook a retrospective analysis of of 95 patients with 98 lesions treated by the late Raymond N. Kjellberg. METHODS: Patients were followed for an average of 5.4 years (range, 0.3-12.3 yr), and data regarding hemorrhage, seizure, neurological disability, and incidence of radiation-induced complications were gathered. RESULTS: The analysis revealed a drop in annual hemorrhage rates from 17.3% per lesion per year before treatment to 4.5% per lesion per year after a latency period of 2 years. Improvement in seizure control was evident. However, a 16% incidence of permanent neurological deficit and a 3% mortality rate were attributable to radiographically confirmed radiation-induced complications. Neurological disability scores, measured by the modified Rankin disability scale, indicated a significant decline in neurological functioning during the follow-up interval, a result of the combined effects of radiation-related injury, hemorrhage, and clinical progression of the lesion. CONCLUSION: We conclude that although radiosurgery does seem to reduce hemorrhage, there is potential for complications and continued lesion progression after radiosurgery. These risks and benefits must be carefully balanced against the natural history of untreated lesions if the use of radiosurgery is considered.

Adolescent↗
PubMed1996

Female pseudohermaphroditism due to congenital adrenal hyperplasia complicated by adenocarcinoma of the prostate and clear cell carcinoma of the endometrium.

The presence of prostatic glandular tissue in female pseudohermaphrodites has previously been documented. However, prostatic neoplasia in this clinical setting has not been reported. A karyotypic female with congenital adrenal hyperplasia due to 21-hydroxylase deficiency developed a prostatic adenocarcinoma associated with elevated serum prostatic specific antigen levels and osteoblastic skeletal metastases. This demonstrates that this tissue in pseudohermaphrodites can become malignant. In addition, the patient subsequently developed clear cell carcinoma of the endometrium, possibly related to radiation therapy for the prostatic adenocarcinoma. This demonstrates that female pseudohermaphrodites may be at risk not only for malignancies seen in genotypic females but also prostate cancer.

Adenocarcinoma↗
PubMed1995

Functional magnetic resonance imaging for cortical mapping in pediatric neurosurgery.

Currently there is considerable interest in applying functional imaging modalities to the problem of cortical localization. We present the case of a 15-year-old boy with a seizure disorder related to a tumor in the dominant supplementary motor area. This case illustrates the usefulness of functional magnetic resonance imaging as a new imaging tool for localization of cortical function in younger patients. The functional magnetic resonance imaging provided an anatomically accurate topographic map of operative site and subcortical structures along with relevant functional cortex. This information was useful for both presurgical planning and intraoperative localization. Validation of the technique in this instance was confirmed with intraoperative cortical motor mapping and the postoperative result.

Adolescent↗
PubMed1995

Symptomatic syringomyelia following surgery to treat retethering of lipomyelomeningoceles.

The authors report the cases of three children in whom symptomatic syringomyelia occurred de novo following an operation to relieve retethering of a previously treated lipomyelomeningocele. No patient had a Chiari malformation. In two cases, magnetic resonance imaging performed before the first operation did not show a syrinx. At the time of surgery to relieve retethering, it was discovered that one of these patients had a minor degree of terminal hydromyelia and the other had a prominent central canal within the conus medullaris. The third patient was initially studied by means of myelography, which gave no indication of a syrinx, and one was not found at the time of the surgery to release the retethering. Neurological deficits appeared abruptly within several months of operation in two children, and insidiously after 12 to 18 months in the other symptomatic individual. In all three cases, the syrinx involved the distal spinal cord adjacent to the site of the lipoma. Treatment consisted of syringosubarachnoid shunting, which arrested the progression of deficits but only partially reversed them. The details of each case are presented and the possible mechanism of syrinx formation discussed. Early recognition and treatment of this unusual but important problem are emphasized.

Child↗
PubMed1994

Intramedullary hemorrhage in spinal cord hemangioblastoma. Report of two cases.

The authors describe two cases of intramedullary hemorrhage caused by thoracic hemangioblastoma. Both patients presented with acute paraplegia. The lesion in the first case was diagnosed by myelography and in the second by magnetic resonance imaging. Emergency surgical evacuation of the intramedullary hematoma and tumor was performed in these patients. Hemangioblastoma was confirmed by histopathological examination in both cases. Both patients remain paraplegic after 7 and 1 years, respectively. Intramedullary hemorrhage is a rare and devastating effect of spinal hemangioblastoma.

Adult↗
PubMed1992

Pineal tumors.

From 1972-1985, 30 patients with pineal area tumor have been treated with combinations of surgery and irradiation, no patient receiving chemotherapy as a primary recommendation. Patients ranged between 3 and 69 years of age, 18 were male and 12 female. In 18 patients a tissue diagnosis was made initially, 14 patients required shunts before definitive management and in 8 of the 14 tissue diagnosis was made at the same time. Eight patients had no surgical intervention at any time. Patients who have received irradiation have had whole brain irradiation, local field irradiation, or craniospinal irradiation. Two elderly patients died rapidly of their malignant processes before definitive treatment could be given. Only one patient with a non neoplastic lesion was seen. This was a bleed from an AVM with no underlying tumor. One patient with a pineocytoma was not irradiated. Overall, two-thirds of our patients are alive 5 to 15 years after treatment. There has been no surgical mortality and minimal morbidity from biopsy. Late effects of treatment include one patient with mild hearing loss and three patients with endocrinopathies amenable to medical treatment. We believe that tissue diagnosis allows optimal field design and dose recommendations to be made by the radiotherapist in addition to defining prognosis. In our experience, endodermal sinus tumor and pineoblastoma are highly malignant, and in view of their poor prognosis with conventional management consideration of more radical treatment with a possible role for chemotherapy is suggested.

Adolescent↗
PubMed1992

Subdural empyema complicating bacterial meningitis in a child: enhancement of membranes with gadolinium on magnetic resonance imaging in a patient without enhancement on computed tomography.

Subdural empyema is a known yet infrequent complication of bacterial meningitis. Subdural effusions occur frequently with meningitis in children and usually resolve spontaneously or with subdural taps. Subdural empyema should be suspected when a patient fails to respond to antibiotic therapy or worsens neurologically. Computed tomography (CT) scans with contrast often show enhancement of subdural collections when an empyema exists. However, this is not true all of the time. We present a case of subdural empyema complicating bacterial meningitis in a 4 month old in which CT enhancement was not present yet magnetic resonance imaging (MRI) scans with gadolinium demonstrated intense enhancement. For comparison, we present a second case of a child with sterile subdural effusions due to meningitis that demonstrates an absence of contrast enhancement on MRI studies. MRI scans with contrast may offer a more sensitive means of making an early diagnosis of subdural empyema.

Empyema, Subdural↗
PubMed1992

Is intracerebral schwannoma a developmental tumor of children and young adults? Case report and review.

A case of intracerebral schwannoma in an 11-year-old girl is presented. Of the small number of intracerebral schwannomas reported without association to a cranial nerve, the majority have occurred in children or young adults. Several possible etiologies for this tumor type are discussed. Based upon the distribution of ages at presentation and theories of the pathological origin of this tumor, the possibility that intracerebral schwannoma represents a developmental tumor is suggested.

Biomarkers, Tumor↗