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Biomedical subjects

M D Medlock

Publications and source records attributed to M D Medlock.

13 recordsLinked to original sources
PubMed2001

Use of acetazolamide to decrease cerebrospinal fluid production in chronically ventilated patients with ventriculopleural shunts.

Acetazolamide (ACTZ), a carbonic anhydrase inhibitor, has been shown to decrease cerebrospinal fluid (CSF) production in both in vivo and in vitro animal models. We report two children with hydrocephalus who experienced multiple shunt failures, and who had externalised ventriculostomy drains (EVD) prior to ventriculopleural shunt placement. The effects of increasing doses of ACTZ on CSF production and subsequent tolerance to ventriculopleural shunts were evaluated. The patients had a 48% and a 39% decrease in their EVD CSF output when compared to baseline with maximum ACTZ dose of 75 mg/kg/day and 50 mg/kg/day, respectively (p < 0.05). This is the first report of change in CSF volume in children after extended treatment with ACTZ. ACTZ treatment in mechanically ventilated paediatric patients with hydrocephalus may improve tolerance of ventriculopleural shunts and minimise respiratory compromise. Potassium and bicarbonate supplements are required to correct metabolic disturbances.

Acetazolamide↗
PubMed2000

Conditionally replicating herpes simplex virus mutant, G207 for the treatment of malignant glioma: results of a phase I trial.

G207 is a conditionally replicating derivative of herpes simplex virus (HSV) type-1 strain F engineered with deletions of both gamma(1)34.5 loci and a lacZ insertion disabling the UL39 gene. We have demonstrated the efficacy of G207 in treating malignant glial tumors in athymic mice, as well as the safety of intracerebral G207 inoculation in mice and in Aotus nancymai. We sought to determine the safety of G207 inoculation into cerebral malignant glial tumors in humans. Criteria for inclusion into this dose-escalation study were the diagnosis of histologically proven malignant glioma, Karnofsky score > or = 70, recurrence despite surgery and radiation therapy, and an enhancing lesion greater than 1 cm in diameter. Serial magnetic resonance images were obtained for volumetric analysis. The trial commenced at a dose of 10(6) plaque forming units (p.f.u.) inoculated at a single enhancing site and was completed when the 21st patient was inoculated with 3x10(9) p.f.u. at five sites. While adverse events were noted in some patients, no toxicity or serious adverse events could unequivocally be ascribed to G207. No patient developed HSV encephalitis. We found radiographic and neuropathologic evidence suggestive of anti-tumor activity and long-term presence of viral DNA in some cases.

Adult↗
PubMed1997

Optic chiasm astrocytomas of childhood. 1. Long-term follow-up.

We reviewed 61 patients seen from 1975 to 1994 with a biopsy-confirmed optic chiasm astrocytoma or a characteristic clinical and imaging presentation. The mean age at diagnosis was 72 months, including 30 who were less than 5 years old. The mean tumor diameter at presentation was 31 mm among 54 tumors measured. Tumors involved the optic nerve in 41, hypothalamus in 38, optic tract in 15, and optic radiations in 2. Four patients, all with neurofibromatosis, received no treatment. Forty patients received conventional radiation therapy at a mean age of 89 months. Chemotherapy was given to 19 children and 7 of these were followed for greater than 1 year. Six of these 7 had progressive disease which required subsequent surgery and/or radiation therapy. Thirty-six patients underwent surgery. We restricted our analysis of outcome to those 38 patients followed for longer than 60 months. Development was normal in 13%, mildly disabled in 53%, severely disabled in 21% and dead in 13%. Children were severely disabled or dead in 47% if younger than 5 years at diagnosis, and 21% if older. There was no endocrine dysfunction in 18% and new endocrine failure was seen in 61%. More posterior tumors did not portend a poorer prognosis. Children less than 5 years old had a poorer prognosis. Neurofibromatosis did not have a marked effect on outcome. Intracranial hypertension was an indicator of a poor prognosis. No specific treatment modality was clearly superior in terms of long-term survival or improvement in quality of life.

Adolescent↗
PubMed1997

Optic chiasm astrocytomas of childhood. 2. Surgical management.

We presented our experience from 1975 to 1994 with emphasis on the long term follow-up of children with optic chiasm astrocytomas in part I. In part II we describe the surgical management of 20 patients with the diagnosis of an astrocytoma of the optic chiasm confirmed by biopsy. These patients underwent surgery by the senior author between 1988 and 1994. The patients and the tumors in this series are comparable in age, sex, and presentation and imaging characteristics to other series. Surgery was undertaken with the intent to reduce tumor volume and mass effect and in certain cases to confirm the diagnosis. The patients' mean age at the time of surgery was 81 (range 18-216) months. The surgical approaches used were pterional in 11 patients, transorbital/subfrontal in 8, and subfrontal in 1 patient. Greater than 50% of the tumor was resected in 8 patients, less than 50% was resected in 9, and biopsy only was achieved in 3 patients. Larger tumors were more likely to have magnetic resonance imaging documented debulking of tumor. Permanent morbidity included mild visual loss, diabetes insipidus, mild hemiparesis, and panhypopituitarism in 1 patient each. There was no surgical mortality. The likelihood of resecting greater than 50% of the tumor was higher in those with a diameter greater than 25 mm. The indications for craniotomy are (1) to debulk symptomatic tumors greater than 50 mm in diameter which are exophytic or cystic; (2) to relieve obstruction at the foramen of Monro, and (3) for diagnostic biopsy.

Astrocytoma↗
PubMed1994

Subcutaneous palisading granuloma of the scalp in childhood.

Subcutaneous palisading granulomas, lesions characterized by collagen necrosis and chronic inflammatory changes, may present as ill-defined, immobile, nontender masses of the scalp. They are frequently multiple and may vary in size over time. Imaging studies rarely show involvement of the calvarium. The histological pattern of palisading histiocytes around necrobiotic granulomas is seen in association with a variety of systemic illnesses but more commonly occurs as an isolated entity in childhood. They are unlikely to herald rheumatological disease unless the erythrocyte sedimentation rate is elevated. In the presence of juvenile rheumatoid arthritis, histological confirmation is usually not indicated. If the lesions are not associated with any other clinical symptoms excisional biopsy may be indicated to establish a diagnosis. The nodules need not be removed as they will spontaneously regress.

Child, Preschool↗
PubMed1993

A 10-year experience with postpump chorea.

Postpump chorea (PPC) is the development of choreoathetoid movements within 2 weeks following cardiopulmonary bypass. Over a 10-year period, 668 children underwent open cardiac surgery, of whom 8 (1.2%) developed PPC. Age at surgery ranged from 8 to 34 months. The onset of chorea was 3 to 12 days following surgery. Computed tomography and magnetic resonance imaging showed atrophy but no focal lesions. Cerebral positron emission tomography using [18F]fluorodeoxyglucose in a patient following 12 months of chorea showed patchy areas of decreased glucose metabolism. None of the patients were developmentally normal 22 to 130 months following surgery. Three patients have had transient and 5 have persistent chorea. Neurological deficits ranged from a mild learning disability to progressive hypotonia and obtundation ending in death. One of 4 patients who received haloperidol had a decrease in the severity of chorea. We compared PPC patients with 39 randomly selected controls. During surgery, affected patients spent significantly more time on pump and at temperatures under 36 degrees C, were cooled to lower temperatures than controls, and were more likely to have had a circulatory arrest. One patient developed chorea without a history of circulatory arrest. We conclude that (1) there is a strong association between PPC, deep hypothermia, and circulatory arrest, (2) absence of characteristic macroscopic changes suggests a biochemical or microembolic etiology in some cases, (3) chorea is frequently associated with developmental delay, and (4) the prognosis for complete resolution of chorea is guarded.

Brain↗
PubMed1993

Dissociation of cerebral blood flow, glucose metabolism, and electrical activity in pediatric brain death. Case report.

A 2-month-old infant demonstrated clinical brain death 48 hours after suffering a closed head injury accompanied by cardiac arrest. Two nuclear cerebral blood flow (CBF) studies demonstrated normal perfusion. On the 11th day following injury, cerebral electrical activity ceased and a normal glucose metabolic gradient between gray and white matter was documented on positron emission tomography. Autopsy revealed widespread necrosis with mononuclear cell infiltrates throughout all cerebral cortical layers. Nine children have previously been described with clinical brain death, electrocerebral silence, and evidence of CBF by radionuclide scan. The dissociation between cerebral electrical activity and blood flow may be explained by an increase in cranial volume allowed by the expansile neonatal skull, preventing both intracranial hypertension and a reduction in perfusion pressure. The persistence of glucose metabolism may be associated with the presence of inflammatory microglial cells in the ischemic cortex. The authors conclude that persistence of CBF and glucose metabolism in brain-dead children may not indicate neuronal survival. If repeated neurological examinations with or without electroencephalography support the diagnosis of brain death, the presence of CBF and glucose metabolism should not alter this conclusion.

Brain↗
PubMed1992

Prophylactic hypervolemia without calcium channel blockers in early aneurysm surgery.

Delayed ischemic neurological deficit (DIND) remains a major unsolved problem in the management of aneurysmal subarachnoid hemorrhage (SAH). For many years, the complications reported with acute aneurysm surgery caused surgeons to operate late after SAH. In a 42-month-period, we managed 146 patients with aneurysm and/or SAH. Forty-seven patients were characterized by the following: Hunt and Hess Grades I through III after an aneurysmal SAH; 2) clipping of their aneurysm within 72 hours of their SAH; and (3) prophylactic hypervolemia with a pulmonary artery catheter to optimize their fluid management. Forty of 47 (85%) had an excellent or good outcome, and 3 of 47 (6%) died. All of those who died had DIND. Nine of 47 (19%) patients developed DIND. There were 20 complications, primarily pulmonary edema, in 16 patients and one death related to prophylactic hypervolemia. It is not clear from our experience, when compared with results from other series, that hypervolemia provides any additional benefit to the patient as measured by a reduction in the risk of DIND or improved outcome. Despite aggressive volume expansion to the point of cardiovascular compromise, as evidenced by our high rate of pulmonary edema, we had no appreciable decrease in neurological morbidity and mortality when compared with results from recent reports.

Blood Volume↗
PubMed1992

Children with cerebral venous thrombosis diagnosed with magnetic resonance imaging and magnetic resonance angiography.

From 1985 to 1991, 13 children were diagnosed at the University of Illinois College of Medicine at Peoria, Saint Francis Medical Center, with cerebral venous thrombosis (CVT) by magnetic resonance imaging scan. Ages ranged from newborn to 5 years. Six children were premature neonates, five were term neonates and two were 5 years old. In the premature neonates, thrombosis was usually associated with other problems. All the term neonates had seizures. In all neonates, thrombosis resolved without any specific treatment. In the two older children, one presented with pseudotumor cerebri and one with coma. These children required neurosurgical intervention. Follow-up magnetic resonance imaging scans were obtained in 9 of 13 children and showed thrombus resolution in each case. Three children were studied in the acute and convalescent stages by magnetic resonance angiography using time-of-flight techniques. Each follow-up magnetic resonance angiogram showed improvement in venous flow consistent with their clinical course and other imaging studies. We conclude that 1) CVT in children encompasses a range of clinical conditions which may or may not require neurosurgical intervention; 2) magnetic resonance imaging is superior to other modalities for the diagnosis of CVT; and 3) magnetic resonance angiography is an alternative means to monitor the evolution of CVT and efficacy of therapeutic intervention.

Cerebral Angiography↗
PubMed1991

A case of glutaric acidemia type II (severe multiple acyl-CoA dehydrogenation disorder) with subsequent prenatal exclusion in a sibling.

A case of severe multiple acyl-CoA dehydrogenation disorder is described. This is the second such case reported to have had an elevated maternal serum alpha-fetoprotein and normal amniotic alpha-fetoprotein. The child's 3-day extrauterine life was characterized by intractable acidosis, respiratory distress, and ventricular fibrillation. The characteristic biochemical, morphologic, and microscopic findings of this condition are reviewed. A subsequent pregnancy was evaluated using chorionic villus sampling and analysis of cultured trophoblasts. The trophoblasts were biochemically normal, and a normal child was subsequently delivered. Since the manifestations of this disorder developed in utero, prenatal diagnosis and therapy offer the only hope for a more prolonged survival.

Acidosis↗