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Biomedical subjects

W K Clark

Publications and source records attributed to W K Clark.

At least 37 records · Page 2Linked to original sources
PubMed1979

Halo immobilization of cervical spine fractures. Indications and results.

Thirty-three patients with a spectrum of cervical spine fractures or subluxations were treated with immobilization by a halo apparatus. All spines were assumed to be unstable because of the nature of the fracture or because of a subluxation noted on spine films. Treatment consisted of immobilization and fracture reduction followed by application of a halo plaster cast or molded halo plastic vest. Patient acceptance was high. Complications were few and minor. No patient experienced neurological deterioration during treatment. Reduction was well maintained during an average halo immobilization period of over 3 months. Use of the halo resulted in healing of bone and ligament and restoration of stability in 85% of the patients. Halo immobilization was efficacious in the treatment of odontoid and hangman's fractures as well as complex fractures involving multiple areas of a single vertebra. It was also used successfully as an adjunct to posterior cervical fusion. Although several patients with subluxations or angulation without bone injury were treated successfully, two of the four therapy failures occurred in this group of patients, and the halo must be used with caution in this clinical setting. Contraindications to the use of the halo include complete cervical spinal cord injury with anesthetic skin, tomographic and/or myelographic evidence of disc or bone within the spinal canal, and unsatisfactorily reduced subluxations. The halo has provided more effective and reliable immobilization than other orthoses. It is an acceptable alternative to cervical fusion for the achievement of stability in a wide variety of cervical spine fractures and dislocations avoiding both the short-term and perhaps long-term complications of spinal fusion.

Adolescent↗
PubMed1979

Dexamethasone and severe head injury. A prospective double-blind study.

A prospective double-blind study of the effects of dexamethasone administration on the outcome of patients with severe head injuries was performed. Patients were stratified for severity of neurological injury and were treated with placebo, low-dose dexamethasone (16 mg/day), or high-dose dexamethasone (96 mg/day) for a period of 6 days. Outcome was evaluated at 6 months following injury. Of the 76 patients available for analysis, a good outcome was achieved in 37% of placebo-treated patients, 44% of low-dose-treated patients, and 29% of high-dose-treated patients. These differences are not statistically significant. Similarly dexamethasone administration had no statistically significant effect on intracranial pressure patterns or serial neurological examinations during hospitalization. Gastrointestinal bleeding occurred in only one patient. Good outcome was associated with age under 10 years, lighter depth of coma on admission, and the preservation of brain-stem reflexes upon admission. A recalculation of data in previous clinical series purporting to show an improvement in outcome as a result of corticosteroid therapy shows no significant difference in outcome when steroid- and placebo-treated patients are compared. In our series, 90% of all deaths were caused by recurrent intracranial hematomas, medical complications, or diffuse brain injuries with parenchymal hemorrhage and tissue disruption -- causes of death which cannot be affected by corticosteroid therapy. The study suggests that dexamethasone in either high or low dosages has no significant effect on morbidity and mortality following severe head injury.

Adolescent↗
PubMed1979

Malignant pineal region tumors. A clinico-pathological study.

Eight patients with primary malignant pineal tumors have been seen at this institution over the past 6 years; six of them underwent definitive surgical exploration. Complete gross microsurgical excision of well encapsulated tumors was possible in four of these patients. In two cases of pineal germinomas, a biopsy and a subtotal resection were carried out because of the known radiosensitivity of this tumor. These six surgical patients all received postoperative craniospinal radiation and continue to do well up to 6 years postoperatively. Two nonoperative patients were initially treated at other institutions by ventriculoperitoneal shunt and radiation and were the only ones to develop metastatic disease. One patient had metastasis of her pineoblastoma to her unirradiated spinal canal and the other patient had metastasis of his germinoma to the peritoneum. The former patient was quadriplegic on admission, although her pineal tumor was no longer visible on computerized tomography (CT), and she died of pneumonia. The latter patient's tumor secreted the beta chain of human chorionic gonadotropin (HCG). This patient's massive metastatic tumor burden completely regressed as determined by body CT scan and HCG levels after four courses of chemotherapy with bleomycin, vinblastine, and cis-platinum. In 20 patients with lesions of the pineal region, craniotomy was associated with only one death (a patient with metastatic adenocarcinoma). Thus, microsurgery for pineal tumors provides either a reasonably safe potential for complete tumor extirpation and possible cure, or a tissue diagnosis which is necessary for appropriate therapeutic planning for radiotherapy and/or chemotherapy. The traditional therapeutic approach of empiric radiotherapy without a tissue diagnosis for pineal lesions may no longer be warranted.

Adolescent↗
PubMed1977

Surgical management of unruptured asymptomatic aneurysms.

The natural history of unruptured asymptomatic aneurysms in nuclear. Because of this uncertainty regarding risk of ultimate enlargement and/or hemorrhage, and in view of the significant mortality and morbidity traditionally involved in aneurysm surgery, clinicans have varied in their advocacy of surgical management of such lesions. Forty-nine consecutive patients harboring 52 such aneurysms were treated surgically over a 57-month period. There were no surgical deaths and morbidity was within acceptable limits. Patient population characteristic and surgical technique are discussed.

Adult↗
PubMedDate not supplied

Comparison of the infratentorial and transtentorial approaches to the pineal region.

During the past 10 years, two different operative approaches to the pineal region have been recommended by different authors. Numerous reports have appeared in the literature, indicating the safe use of one or the other of these two techniques for the excision of masses in the pineal region. This paper reports experience with both techniques in the treatment of 15 patients with mass lesions in this area. Four patients underwent a supracerebellar infratentorial approach and 11 patients underwent an occipital transtentorial approach to the pineal region. These two approaches are compared in terms of anatomical exposure, technical difficulties, and real or potential complications. The authors prefer the occipital transtentorial approach in dealing with lesions in the pineal region.

Adult↗
PubMedDate not supplied

Microsurgical evaluation of the pterional approach to aneurysms of the distal basilar circulation.

The microsurgical correlates the pterional approach to the distal basilar circulation were evaluated in 20 cases of posterior circulation aneurysms, 50 human cadaver dissections, and a variety of other intracranial surgical lesions. The pterional approach permitted successful clipping of the aneurysm in 13 of 15 basilar bifurcation aneurysms, 1 of 2 basilar-posterior cerebral aneurysms, and 2 of 3 basilar-superior cerebellar aneurysms. In each of the failed attempts via the pterional approach, the subtemporal route ultimately resulted in proper clip application. The interposition of the posterior clinoid process was the impediment to successful clipping in three of the four cases that could not be managed via the pterional approach. All 3 of these patients had a basilar bifurcation that was below the level of the posterior clinoid on angiography, whereas none of the remaining 17 aneurysm patients demonstrated a low-lying bifurcation. Posterior displacement of the basilar artery away from the posterior clinoid exceeded 1 cm in only 13% of our cases and was not an impediment to successful clipping of the aneurysm via the pterional route. We conclude that, when the anatomical situation is appropriate, the pterional approach offers the advantages of less brain retraction and better visualization of the parent arteries and important perforating branches when compared to the subtemporal approach.

Basilar Artery↗
PubMedDate not supplied

Servo-controlled lumbar infusions: a clinical tool for the determination of CSF dynamics as a function of pressure.

The variable rate lumbar subarachnoid infusion technique allows rapid quantitative study of the cerebrospinal fluid (CSF) compartment. Numerous pressure plateaus are studied in a brief time period with a servo-controlled system. The test determines the difference between rates of CSF absorption and formation as a function of pressure. On-line computer data analysis increases experimental efficiency to guarantee statistical significance. Animal and patient data are presented in the report.

Absorption↗
PubMedDate not supplied

Unique aspects of central nervous system immunology.

In this review the authors discuss three immunologically unique aspects of the central nervous system (CNS). The first relates to whether the CNS is really an immunologically privileged site. Although still somewhat controversial, the answer to that question is that the CNS is, to a large extent, an immunologically privileged site. The second unique aspect of the CNS is the origin and significance of the microglial cell. Some microglial cells seem to originate from the systemic circulation, whereas other microglial cells seem to have a primary CNS origin. The function of the microglial cell is that of a macrophage. In addition it may play an important role in the immune response of the CNS. Present evidence suggests that the microglial cell can be classified as a lymphoreticular cell and as such is the only member of this cell type present in the CNS under normal circumstances. The final unique aspect of the central nervous system is the cerebrospinal fluid (CSF). Under normal circumstances this fluid is essentially acellular, and the only immunoglobulins present are those that are passively derived by diffusion from the systemic circulation. However, in pathological situations (i.e., demyelinating diseases, infections, and possibly even tumors) a local immune response occurs within the CNS and can result in the production of immunoglobulins. At present the detection of such local immune responses in CSF is predominately of diagnostic value only. However, these local CNS immune responses almost certainly play an important role in the pathogenesis of the diseases in which they occur.

Adult↗