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Biomedical subjects

P Dyck

Publications and source records attributed to P Dyck.

At least 19 recordsLinked to original sources

High-dose tamoxifen in treatment of brain tumors: interaction with antiepileptic drugs.

The incidence of seizures related to primary brain tumors is 20-80%. High-dose tamoxifen was recently reported as a novel treatment for patients with malignant gliomas who have failed standard therapies. Tamoxifen inhibits protein kinase C (PKC) in vitro and thus may regulate glioma cell growth by modulating intracellular signal transduction. We report a patient with a recurrent supratentorial pilocytic astrocytoma who had an untoward interaction between high-dose tamoxifen therapy and phenytoin (PHT), drugs that share a common enzyme for metabolism, therefore emphasizing the need to monitor concomitant antiepileptic drug (AED) levels when high-dose tamoxifen therapy is instituted.

Adult↗

Malignant fibrous histiocytoma of the pericranium: case report.

Malignant fibrous histiocytoma only infrequently arises from structures of the head and neck. When it does, it most often originates in facial structures, particularly the maxilla. This case report details a malignant fibrous histiocytoma arising from the pericranium, and presenting clinically as a large indurated frontal calvarial mass. A CT scan showed its origin to be from the pericranium and demonstrated its intracranial extension. Radical excision presented a surgical challenge because of the extensiveness of the lesion. Yet, combined with post-operative teletherapy, a favourable outcome was obtained.

Histiocytoma, Benign Fibrous↗

Stereotactic biopsy and brachytherapy of brain tumours.

This paper discusses 98 patients who had their cerebral lesions stereotactically biopsied. Modified Riechert-Mundinger instrumentation was employed. Of the 98 patients, eight received only biopsy and 90 were then interstitially radiated with iridium-192 (192Ir) custom stacked in afterloading catheters. The vast majority of brachytherapeutically treated lesions were anaplastic or malignant astrocytomas. There were some metastatic lesions, and in two instances the tumour occupied the infratentorial compartment. Two-thirds of the patients had received prior teletherapy; in the remainder, stereotaxis provided the initial diagnosis and brachytherapy the principal treatment. The survival data suggest reasons for optimism. Eighty percent of patients with anaplastic astrocytoma were alive 2 yr later, compared with 55% for those harbouring malignant astrocytomas. Since this is the largest database on this topic in the U.S.A., we are in the process of a more critical review. Complication rate is low. Diagnostic tissue was obtained in all instances. Delayed radionecrosis at the site of implant may aggravate neurological deficits when lesions involve functionally sensitive cortex or their pertinent underlying structures. Such reactions may appear 4-18 mnth after brachytherapy and are more likely to occur in patients who were previously radiated.

Adolescent↗

CT-compatible system for stereotactic biopsy and brachytherapy of infratentorial tumors.

Teletherapy of nonresectable radiosensitive brain tumors is the mainstay of adjunctive treatment. In the past two decades brachytherapy has begun to play an ever-increasing role, particularly on the European continent. Yet this attention has been addressed almost exclusively to lesions of the supratentorial space. This article describes modifications of the Riechert-Mundinger stereotactic system which were made by one of us (P.D.) to allow an unencumbered yet precisely computerized stereotactic approach to posterior fossa lesions for biopsy and interstitial radiation with iridium 192. A case report is described to illustrate the technical details involved in such an undertaking.

Adult↗

Lumbar reservoir for intrathecal chemotherapy.

The Ommaya ventricular reservoir has been the standby of intrathecal chemotherapy for more than a decade, in spite of some specific drawbacks. A general anaesthetic is often required. The scalp must be shaven. Ventricular puncture may not always be easy and keeping the ventricular catheter patent is sometimes difficult. Hence the author has adapted a commercially available lumbar peritoneal shunt system to function as a lumbar intrathecal reservoir. The procedure is simple and can be performed expeditiously under local anaesthesia. To date, eight cases have received intrathecal chemotherapy by this means.

Antineoplastic Agents↗

Paraplegia following chemonucleolysis. A case report and discussion of neurotoxicity.

A case report of inadvertent chymopapain introduction into the lumbar theca is reported. It led to an extensive subarachnoid and subdural hemorrhage, producing paraplegia. The neurotoxicity of chymopapain in the experimental model is reviewed and related to a clinical setting. Clinically speaking, there appears to be no tolerance for this discolytic agent either in the peripheral or central nervous system. Cerebrospinal fluid barbotage may lessen the neurologic injury by removing the enzyme when it finds its way inadvertently into the subarachnoid space.

Adult↗

Sylvian lipoma causing auditory hallucinations: case report.

A sylvian fissure lipoma that caused auditory hallucinations, frequent olfactory auras, and occasional visual hallucinations is reported. The patient had been diagnosed as suffering from a functional psychosis for more than a decade, with symptoms severe enough to warrant frequent psychiatric attention, including institutional care. The computed tomographic findings are discussed. The literature is reviewed and therapeutic options are proposed.

Adult↗

Computer-aided, CT-guided biopsy and brachytherapy of brain tumors.

The authors present the principles of computer-aided, CT-guided stereotaxis as it applies to the modified Riechert-Mundinger equipment. A preliminary report on 20 prospectively biopsied and interstitially radiated patients with cerebral mass lesions is discussed. 192Ir served as the interstitial isotope exclusively. To date the results are encouraging and complement the European experience. However, a great deal of improvement is possible, particularly in the sophistication of interstitial radiation of brain tumors; all well within presently available technology.

Adult↗

Symptomatic hemifacial spasm: case report and review of literature.

The purpose of this article is to discuss a case of hemifacial spasm due to a fusiform basilar aneurysm. The hemifacial spasm was successfully treated by decompression of the facial nerve in the facial canal 14 months before death due to aneurysmal rupture. The literature on symptomatic hemifacial spasm is reviewed, the pathophysiology discussed and the therapeutic options presented. Since the pathophysiology is poorly understood, conservatism is recommended.

Basilar Artery↗

Failed lumbar disc surgery: cause, assessment, treatment.

The challenge of failed back surgery is in the decision of when to operate and how to do it competently. Specific neuroanatomic indications as a basis for surgical treatment should reduce surgical failures. One source of failure is a "battered root" and the arachnoiditis which may follow limited or inadequate interlaminar exposure. Even with adequate interlaminar exposure, hemostasis may be difficult if preoperative positioning of the patient to diminish intra-abdominal pressure has not been performed. Bleeding can obscure the operative field and the surgeon's ability to visualize and deal with the problem at hand. A less common cause of failure is segmental instability. This may be pre-existing and related to facet tropism. It may also be a consequence of surgical removal of posterior vertebral elements, thus creating a loss of stability with or without a discernable change in vertebral alignment. The surgeon should try to: avoid becoming enmeshed in the psychodynamic problems of patients. He should use specific diagnostic tests, e.g., nerve blocks or facet injections, in an effort to localize specific sources of pain; recognize that prognosis is adversely affected by additional surgery; and avoid "exploratory" operations. Furthermore, neurolysis without spatial decompression, bony or otherwise, is eventually futile. All patients with failed back surgery have a psychodynamic component to their pain. This article will have achieved its purpose if it promotes recognition that a small percentage of patients with failed back surgery can be helped. These are individuals in whom specific diagnostic tests or clinical acumen uncover a surgically correctable lesion, be it compressive or radiculopathy or segmental instability. In such instances an adverse psychologic profile need not necessarily be a deterrent to surgical treatment.

Adult↗

Anterior sacral meningocele. Case report.

A woman presented with a mass in the left groin, which was later shown to be a sliding hernia. A bony sacral defect prompted investigation, which uncovered a massive anterior sacral meningocele. Examination, including ultrasonography and myelography, is discussed, and a surgical approach proposed.

Adult↗

Arachnoid cysts.

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Adult↗

Supratentorial arachnoid cysts in adults. A discussion of two cases from a pathophysiologic and surgical perspective.

Large congenital arachnoid cysts are a rare cause of increased intracranial pressure and progressive neurologic deficits in adult life. We describe two patients, diagnosed by computerized axial tomography and surgically treated. The pertinent medical literature was reviewed. The outer cyst membranes were excised, and a communication between cyst and subarachnoid space was established. When possible, the membranes and fluid content of these lesions should be studied. This fluid is best obtained by aspiration prior to dural incision. At present, three etiologic mechanisms of cyst enlargement appear tenable: (1) secretion of fluid by ependymal cells, (2) fluid ingress due to an osmotic gradient, and finally, (3) trapping of fluid by a ball-valve mechanism. Regardless of the reasons why these lesions enlarge, drainage of cyst content into the venous system warrants a clinical consideration.

Brain↗