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Biomedical subjects

T H Milhorat

Publications and source records attributed to T H Milhorat.

At least 19 recordsLinked to original sources
PubMed1992

Classification of the cerebral edemas with reference to hydrocephalus and pseudotumor cerebri.

Cerebral edema is a common clinical disorder that results from an abnormal increase in water content within the extracellular (EC) compartment of the brain. It is distinguished from two other types of brain bulk enlargement: (1) vascular swelling, caused by arterial dilatation or venous obstruction; and (2) cellular swelling, caused by cytotoxic injuries or metabolic storage. Under normal conditions, the EC compartment has two fluids, the interstitial fluid (ISF) and the cerebrospinal fluid (CSF), and extends from the blood brain barrier (BBB) through a series of 100 to 150-A-wide intercellular spaces that are anatomically continuous with the CSF spaces. There are four primary types of EC edema: (1) vasogenic edema, which results from an increase in brain capillary permeability, the most common type, in which leakage of plasma constituents into the brain follows the pathways of ISF bulk flow and is governed by the interaction of systemic arterial pressure and tissue resistance; (2) osmotic edema, which results from an unfavorable osmotic gradient between the plasma and ISF across an intact BBB; (3) compressive edema, which results from obstruction of ISF bulk flow pathways; and (4) hydrocephalic edema, which results from obstruction of CSF bulk flow pathways. In this latter type of edema, distension of the collecting channels proximal to the block leads to retrograde flooding of the EC compartment with the formation of periventricular edema. The syndrome of pseudotumor cerebri includes several different types of brain bulk enlargement.

Animals↗
PubMed1992

Surgical treatment of syringomyelia based on magnetic resonance imaging criteria.

The treatment of syringomyelia includes many surgical options. We report a retrospective study of 65 patients with cavitary lesions of the spinal cord in whom the results of magnetic resonance imaging were used to develop specific treatment strategies. Intramedullary cavities were classified into three general types: 1) communicating syrinxes, which occurred with hydrocephalus and were anatomically continuous with the 4th ventricle (9 patients); 2) noncommunicating syrinxes, which were separated from the 4th ventricle by a syrinx-free segment of spinal cord (42 patients); and 3) atrophic syrinxes, which occurred with myelomalacia (14 patients). Noncommunicating syrinxes were further subdivided according to type: Chiari II malformations with hydrocephalus (5 patients), Chiari I malformations without hydrocephalus (11 patients), extramedullary compressive lesions (12 patients), spinal cord trauma (6 patients), intramedullary tumors and infections (6 patients), and multiple sclerosis (2 patients). Of the 65 patients, 39 underwent surgical treatment for progressive symptoms. Syrinxes occurring with hydrocephalus were treated empirically with a ventriculoperitoneal shunt. Excellent results were achieved in 7 of 7 patients with communicating syrinxes and in all 5 patients with Chiari II malformations. Two approaches were used in the treatment of syrinxes occurring with Chiari I malformations: Posterior fossa decompression improved symptoms but did not reduce syrinx size in 2 of 3 patients. In the third patient and in 3 patients who were not treated with decompression, shunting from the syrinx to the cerebellopontine angle cistern collapsed the cavity and resolved symptoms over the interval of follow-up (average follow-up, 1.5 years). Excision of extramedullary obstructions at the rostral end of noncommunicating syrinxes resulted in collapse or disappearance of the cavity in 6 of 7 patients. The remaining patient was treated effectively by a syringocisternal shunt. In all 4 patients with posttraumatic syringomyelia, good results were achieved by a spinal or syringocisternal shunt. Syrinxes associated with intramedullary masses were managed by biopsy or excision of the causal lesion and appropriate adjunctive therapy (6 patients). Patients with atrophic syrinxes were not operated upon except to relieve symptoms referrable to the causal lesion (4 patients). Recurrent syrinxes were not encountered in the 35 surviving patients over an average follow-up of 2.5 years. It is concluded that syringomyelia is a complex pathological disorder with several mechanisms of pathogenesis that requires a number of different treatment strategies.

Adolescent↗
PubMed1992

Syrinx shunt to posterior fossa cisterns (syringocisternostomy) for bypassing obstructions of upper cervical theca.

Syrinx shunts to the spinal subarachnoid space are likely to fail if the cerebrospinal fluid pathways rostral to the syrinx are blocked. To bypass obstructions at or below the level of the foramen magnum, a technique was developed for shunting the syrinx to the posterior fossa cisterns, termed "syringocisternostomy." Syrinxes were shunted to the cisterna magna in two patients with spinal arachnoiditis and to the cerebellopontine angle cistern in four patients with Chiari I malformations. There was symptomatic improvement and collapse of the syrinx in each case, with no complications or recurrences over a follow-up interval of 14 to 27 months (average 20.3 months). The surgical technique and results of treatment are described.

Adult↗
PubMed1991

Histopathology of experimental hematomyelia.

The pathology of hematomyelia was examined in 35 rats following the stereotactic injection of 2 microliters blood into the dorsal columns of the thoracic spinal cord. This experimental model produced a small ball-hemorrhage without associated neurological deficits or significant tissue injury. Histological sections of the whole spinal cord were studied at intervals ranging from 2 hours to 4 months after injection. In acute experiments (2 to 6 hours postinjection), blood was sometimes seen within the lumen of the central canal extending rostrally to the level of the fourth ventricle. Between 24 hours and 3 days, the parenchymal hematoma became consolidated and there was an intense proliferation of microglial cells at the perimeter of the lesion. The cells invaded the hematoma, infiltrated its core, and removed erythrocytes by phagocytosis. Rostral to the lesion, the lumen of the central canal was found to contain varying amounts of fibrin, proteinaceous material, and cellular debris for up to 15 days. These findings were much less prominent in the segments of the canal caudal to the lesion. Healing of the parenchymal hematoma was usually complete within 4 to 6 weeks except for residual hemosiderin-laden microglial cells and focal gliosis at the lesion site. It is concluded that the clearance of atraumatic hematomyelia probably involves two primary mechanisms: 1) phagocytosis of the focal hemorrhage by microglial cells; and 2) drainage of blood products in a rostral direction through the central canal of the spinal cord.

Animals↗
PubMed1989

Regional brain glucose utilization during and following chronic naltrexone administration: preliminary observations in rat brain.

Experiments were conducted to determine some of the metabolic correlates of tonic opioid activity in the central nervous system under conditions previously examined for changes in monoamine levels. The glucose metabolic rates in seven brain regions were determined by autoradiographic visualization of 14C-deoxyglucose incorporation in female rats after 8 days of chronic exposure to naltrexone pellets and 10 days after pellet removal. Autoradiographs were analyzed on a region-by-region basis to correspond to areas previously dissected and analyzed for changes in monoamine content under similar experimental conditions. Chronic administration of naltrexone resulted in a significant decrease in the metabolic activity of neurons in the striatum. Other brain areas examined under this condition were not significantly affected. Ten days following pellet removal, 14C-deoxy-glucose incorporation was indistinguishable from that determined in placebo treated rats in all brain regions examined. These results indicate that tonic opioid input is an important determinant of metabolic activity in the striatum. In addition, these results indicate that conditions previously shown to alter regional content of monoamines do not necessarily produce concomitant changes in regional glucose utilization.

Animals↗
PubMed1989

Relationship between oedema, blood pressure, and blood flow following local brain injury.

Vasogenic brain oedema is a concomitant of a wide variety of central nervous system lesions that have in common a disturbance of the blood-brain barrier permeability. Although it is well established that the formation and spread of this extracellular type of oedema is influenced directly by variations of systemic arterial pressure, the consequences of these events on local cerebral blood flow are not known. In the current experiments, vasogenic brain oedema was produced in rats by cold-injury lesions, and local cerebral blood flow measurements were made using a technique of 14C-antipyrine quantitative autoradiography under pharmacologically controlled conditions of hypertension, hypotension, and normotension. Evidence is presented that the formation and spread of vasogenic brain oedema is accompanied by the development of a congruent zone of decreased local cerebral blood flow, and that the magnitude of this field of oedema/ischaemia is a direct function of systemic arterial pressure. These findings may have important clinical implications.

Animals↗
PubMed1978

Nerve endings in the choroid plexus of the fourth ventricle of the rat: electron microscopic study.

Nerve fibers and nerve endings in the fourth ventricle choroid plexus of the adult rat were studied with the electron microscope. Nerve endings were found at two sites within the plexus: (1) on the smooth musculature of the blood vessels (i.e. vascular nerve endings), and (2) in the stroma between the choroidal epithelium and the fibrovascular core. Ultrastructurally all fibers were of the efferent type, and the majority were unmyelinated. No ganglion cell bodies were identified. Fibers ending in relation to the smooth muscle of the vessels presumably control the calibre of these vascular channels. Although the role of the stromal nerve endings is as yet unknown, these fibers may influence epithelial cell functions and thus indirectly regulate choroidal cerebrospinal fluid production.

Animals↗
PubMed1976

Normal pressure hydrocephalus in patients with myelomeningocele.

Although the syndrome of normal pressure hydrocephalus (NPH) was described in the adult as early as 1964, it has only recently been recognized in the child. In this preliminary report, eight myelomeningocele patients with presumed NPH were evaluated before and after ventricular shunting procedures. Cranial computed tomography and serial psychological testing have proved to be particularly valuable both in the pre-operative and post-operative assessment of these patients and have the distinct advantage of being simple, non-invasive diagnostic measures. Continuous intra-ventricular pressure monitoring has shown what promises to be characteristic elevated pressure plateaux imposed on normal baseline cerebrospinal fluid (CSF) pressures in so-called NPH but is a more difficult clinical procedure, necessarily associated with potential complications. Although decreasing response to growth-stimulating hormone can be demonstrated in patients with long-standing hydrocephalus, this endocrine malfunction cannot be considered an early indicator of intracranial pathology. Single IQ scores are inadequate measures of intellectural function in children with NPH and serial examinations should be carried out. Detailed neuropsychological testing will document performance IQ scores well below verbal IQ scores and will generally show failure of psychomotor development to keep pace with chronological ageing. Initial studies indicate that improved performance scores can be expected within 1 1/2 to 3 months following successful ventricular shunting operations, and that any downward trend in pre-operative test scoring can at least be reversed. Statistically significant improvements in full-scale IQ scores have not been seen, however, before the end of the first post-operative year. Clinically, improved attentiveness and sociability, and decreased spasticity (if present prior to surgery) can be expected following shunting. Over-all, ventriculomegaly, normal CSF pressure, stable head size, and non-progressive neurological symptoms cannot be regarded as sufficient criteria for the diagnosis of an arrested state of hydrocephalus, and should suggest NPH, especially in those children who demonstrate a discrepancy between performance and verbal IQ scores and who fail to exhibit continuing psychomotor development with advancing age.

Adolescent↗
PubMed1976

Primary choroid plexus papilloma of the cerebellopontine angle presenting as brain stem tumor in child.

A case of a primary choroid plexus papilloma of the cerebellopontine angle in an 8-year-old female is presented. The clinical features of progressive cranial nerve palsies and cerebellar signs in the absence of intracranial hypertension initially suggested an intrinsic brain stem lesion. Whereas a radionuclide brain scan demonstrated abnormal uptake in the region of the pons, vertebral angiography and pneumoencephalography were diagnostic of an angle mass. At surgery, the tumor proved to be a choroid plexus papilloma that was totally confined to the cerebellopontine angle. This patient represents the thirteenth reported case of a primary cerebellopontine angle papilloma and the first such case occurring in a child.

Brain Neoplasms↗
PubMed1976

Normal rate of cerebrospinal fluid formation five years after bilateral choroid plexectomy. Case report.

A ventricular perfusion technique was used to determine the rate of cerebrospinal fluid (CSF) formation in a 5-year-old child who had undergone bilateral choroid plexectomy for communicating hydrocephalus during infancy. At the time of the study, the patient had a failed ventriculoperitoneal shunt and was suffering from progressive ventriculomegaly. The calculated rate of CSF formation, 0.35 ml/min +/- 0.02 standard deviation, was within normal limits.

Cerebral Ventriculography↗
PubMed1976

Choroid plexus papilloma. I. Proof of cerebrospinal fluid overproduction.

Utilizing a ventricular perfusion technique, the rate of CSF formation was determined in a 2-year-old child before and after removal of a 74 g choroid plexus papilloma from the left lateral ventricle. Preoperatively, the CSF formation rate was 1.05 +/- SD 0.01 ml/min (1,656 ml/day). Postoperatively, the CSF formation rate was reduced fivefold to 0.20 +/- SD 0.01 ml/min (288 ml/day). Whereas these data are regarded as conclusive evidence of CSF overproduction by a choroid plexus papilloma, the pathogenesis of generalized ventricular enlargement in this case was due to part to obstruction of the subarachnoid pathways.

Cerebral Ventricle Neoplasms↗
PubMed1976

Unreliability of combined pneumoencephalography and scinticisternography.

Evidence is presented that the radiopharmaceutical flow in cerebrospinal fluid may be significantly altered by pneumoencephalography. When both pneumoencephalography and scinticisternography are required in the same patient, the studies should be performed separately rather than as a combined procedure.

Child↗
PubMed1976

Choroid plexus papilloma. II. Ultrastructure and ultracytochemical localization of Na-K-ATPase.

An electron-microscopic study of a choroid plexus papilloma from the lateral ventricle of a child revealed fine structural features typical of normal choroid plexus tissue. Utilizing the Ernst technique for demonstrating ouabain-sensitive, potassium-dependent phosphatase activity, Na-K-ATPase was localized along the basal and lateral plasmalemmas of the tumor epithelium but not along the ventricular surface (apical plasmalemma). This localization is similar to that found in normal choroid plexus epithelium of all species studied to date.

Adenosine Triphosphatases↗