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Biomedical subjects

J M Van Buren

Publications and source records attributed to J M Van Buren.

At least 19 recordsLinked to original sources
PubMed1985

Tumors of the paranasal sinuses: a therapeutic challenge.

Cancer involving the ethmoid and sphenoid frontal sinus complex can be successfully eradicated by a combined transcranial and transfacial surgical dissection. Survival rates of 44 to 58 percent with a 3 percent hospital mortality rate in patients whose previous surgery or radiotherapy was largely unsuccessful suggest that this cosmetically acceptable surgical endeavor should be used more often by the head and neck surgeon in treating paranasal sinus cancer. Utilizing the principles of antibiotic prophylaxis, strict attention to principles of tumor removal and surgical technique, and the talents of the combined surgical and neurosurgical team, this aggressive surgical approach to the paranasal sinuses can be safely and successfully carried out. The approach described herein has the following advantages: it allows accurate evaluation of intracranial tumor extension while protecting the intracranial contents, it essentially avoids cerebrospinal fistulization, it provides adequate exposure for hemostasis, facilitates en bloc tumor resection, selectively conserves the orbital contents, and provides patient survival rates up to 58 percent for paranasal cancer that involves the ethmoid and sphenoid frontal sinus complex.

Combined Modality Therapy↗
PubMed1983

A multipurpose CT-guided stereotactic instrument of simple design.

The instrument is based upon a radiolucent ring fixed to the skull by four pins. This locks into a frame for CT scanning from which the x, y and z stereotactic coordinates are derived. The head ring may be locked into a compatible support on the operating table for biopsy. A similar support and localization system is used for rotational radiotherapy. With the current 14 MeV apparatus, fields as small as 2 cm in diameter are available with 90% dosage fall-off in the surrounding 1-cm shell.

Biopsy↗
PubMed1983

Sensory responses from stimulation of the inferior Rolandic and Sylvian regions in man.

During the course of 134 craniotomies under local anesthesia, 274 sensory responses to electrical stimulation were recorded as to cortical site, type of sensation, and the site and lateralization of peripheral referral. The region of cortex exposed was largely the sensorimotor region near the Sylvian fissure and the temporal lobe. Differences in the type of sensation were seen on either side of the central fissure. Sensation of movement and specific sensations were reported more commonly from stimulation in the precentral region and crude sensation from the postcentral area. "Pain" was reported only once and taste not at all despite the large somatic sensory representation of the tongue. About 30% of the responses were referred to the ipsilateral side or bilaterally, with a somewhat higher percentage in the pre- than in the postcentral region. In general, the expected somatotopic sequence was followed, with tongue and mouth having the largest representation. An unexpected number of referrals to the head/face were found in the suprasylvian region, and it was uncertain whether this was part of Somatosensory area II. Eleven cases with sensory referrals to trunk/limbs in the suprasylvian area were found predominantly in the precentral region. No somatotopic pattern could be seen in these or on review of Penfield's material. Possible anatomical pathways for transmission of these responses were reviewed and questions raised as to the mechanisms involved.

Brain Mapping↗
PubMed1979

Hemiballismus complicating stereotactic thalamotomy.

The pathology of poststereotactic hyperkinesis has been rarely documented and the pathophysiology is still poorly understood. In a case of hemiballismus following thalamotomy for parkinsonism, detailed anatomical studies showed bilateral cortical pseudolaminar necrosis and no involvement of the subthalamic nuclei by the thalamic lesions. The structural and functional effects of surgical lesions upon the preexisting pharmacological abnormalities present in parkinsonism probably constitute the substrate necessary for occurrence of hemiballismus following stereotactic surgery.

Cerebral Cortex↗
PubMed1979

Anatomical study of a posterior cerebral lesion producing dyslexia.

After an "occipital lobectomy" that resulted in a severe dyslexia and a moderate dysgraphia-dyscalculia, anatomical study showed damage to the posterior extremity of the angular gyrus and degeneration in the posteroinferior pulvinar. This is in contrast to an earlier case that had degeneration in the anterosuperior pulvinor associated with a small anterior temporoparietal infarct and a well-documented receptive-expressive aphasia. However, the role of the pulvinar in speech function remains uncertain. The surgeon should be aware of the short distance between the angular gyrus and both the midline and the occipital pole because a lesion here during an "occipital lobectomy" produces a distressing and durable speech impairment.

Adult↗
PubMed1977

Neuritic growth cone and ependymal gap junctions in the feline subfornical organ during early development.

Intercellular contacts in the subfornical organ (SFO) of kittens 3, 16, and 29 days old were studied in thin sections and by the freeze-etch method. Gap junctions appeared between growing nerve processes and target cells. The junctions were interspersed between immature synapses lacking mitochondria as well as full pre- and postsynaptic membrane specializations. Gap junctions were seen on filopodia as well as on more mature processes. The morphology of these junctions was typical of those described earlier but they were of small size (0.2-0.3 micron). Gap junctions of peculiar form were also seen between ependymal elements in the SFO at 16 days. These were of large size (0.5-0.8 micron) and were often of segmented character. This segmentation consisted of bands 3-4 particles in width with a center-to-center spacing of 90 nm with particle free corridors between corresponding to the width of about two rows of particles. The margin of the group might be circumscribed by a row of particles. Although gap junctions of large size were seen between ependymal cells in thin section, features corresponding to the particle free corridors have not been observed to date.

Aging↗
PubMed1977

Cerebrospinal fluid norepinephrine alterations during electrical stimulation of cerebellar, cerebral surfaces in epileptic patients.

Lumbar cerebrospinal fluid norepinephrine concentrations were determined by radioenzymatic assay in five epileptic patients receiving double-blind cerebellar stimulation and in three epileptic patients with subdural cerebral surface electrodes. Mean CSF norepinephrine levels were significantly elevated by chronic cerebellar stimulation and significantly depressed after intermittent cerebral cortical stimulation. Lumbar CSF cyclic adenosine monophosphate levels determined by radioimmunoassay were not significantly altered by either cerebellar or cerebral surface stimulation. Our study suggests that (1) electrical stimulation of the anterodorsal cerebellum in man evokes alterations in noradrenergic metabolism. Cerebellar stimulation-induced elevations in norepinephrine may inhibit cerebellar, cerebral, and spinal neuronal activity. In addition, (2) noradrenergic responses to brain surface stimulation may exhibit regional specificity, and (3) noradrenergic alterations evoked by cerebral surface stimulation may not mimic those induced in isolated brain preparations.

Adolescent↗
PubMed1977

Cerebrospinal fluid GABA reductions in seizure patients evoked by cerebellar surface stimulation.

Lumbar cerebrospinal fluid (CSF) gamma-aminobutyric acid (GABA) levels determined by fluorometric assay in four seizure patients were found to be significantly lower during bilateral, continuous cerebellar stimulation than those determined after a 7-day period without stimulation. The CSF GABA concentrations during chronic unilateral, alternating cerebellar stimulation were reduced in three seizure patients but unchanged in a fourth patient. The percentage decrease in CSF GABA appeared to be independent of cerebellar stimulation frequency. These findings suggest that GABA-mediated neuronal transmission is depressed during cerebellar surface stimulation and this evoked reduction in GABA activity may compromise the efficacy of cerebellar stimulation in the treatment of epilepsy. Lumbar CSF cyclic guanosine monophosphate levels determined by radioimmunoassay were not significantly altered by either mode or frequency of cerebellar stimulation.

Aminobutyrates↗
PubMed1976

Significance of Purkinje cell density in seizure suppresion by chronic cerebellar stimulation.

Cerebellar biopsy specimens were obtained at the time of cerebellar electrode installation in three epileptic patients. Cerebellar autopsy specimens also were examined from four epileptic patients and from five patients without epilepsy or neurologic disease. All specimens from seizure patients showed isomorphic gliosis of the cerebellar cortices. Significantly lower Purkinje cell densities were found in epileptic patients as compared with nonepileptic control patients. Our two epileptic patients showing marked Purkinje cell loss before cerebellar stimualtaion appeared to have better seizure control during stimulation than the patient who had only mild reduction in Purkinje cell density. These data suggest that augmentation of Purkinje cell inhibitory discharges in not the dominant mechanism for seizure suppression during cerebellar stimulation. Comparison of cerebellar specimens obtained during electrode installation with those obtained later during electrode revisions may have been prognostic significance.

Adolescent↗
PubMed1976

Functional representation on the medial aspect of the frontal lobes in man.

Sensorimotor responses to stimulation of the medical frontal and cingulate area were studied in seven unrestrained, unsedated patients who suffered from intractable seizures. Complex postural synergies involving the trunk and proximal extremities appeared contralaterally or occasionally bilaterally. Contraversive turning of head and eyes was not observed. Sensory responses from the supplementary motor area were referred contralaterally and focally; those from the cingulate gyrus were widely referred. Speech impairment from stimulation of the supplementary motor area showed striking similarities with that obtained from stimulation in the frontostriatal region or lateral aspect of the frontal lobe. The observations support the hypothesis that interference with striatal function may be the basis of speech inhibition produced by stimulation of the frontal lobe.

Brain Mapping↗
PubMed1976

Sensory and nonsensory portions of the nucleus "ventralis posterior" thalami of chimpanzee and man.

In man and chimpanzee, the large-celled region in the posteroinferior portion of the lateroventral thalamic mass, commonly called the nucleus ventralis posterior thalami, is separated cytoarchitecturally into two regions. The anterior portion is called the nucleus ventrointermedius (Vim) and the posterior part, the nucleus ventrocaudalis (Vc). In the chimpanzee it was found that most of the fibers from the superior cerebellar peduncle entered Vim on the way to distribution in the anterior half of the lateroventral thalamic mass. Fibers from the posterior spinal column (medial lemniscus) entered the Vc. No overlap was evident in the radiations from the two sources. An unusual human case is presented suporting the sensory function of Vc since a lesion in this nucleus resulted in persistent contralateral paresthesia. On the other side, a discrete lesion in Vim caused no sensory disturbance.

Afferent Pathways↗
PubMed1975

An instrument for stable single cell recording from pulsating human cerebral cortex.

An instrument has been developed for positioning microelectrodes near neurons in the exposed pulsating cerebral cortex of man or animals. The electrode moves with the cortex and maintains a fixed relationship with the desired neuron. Stable extracellular single cell recordings have been obtained for 17.5 min from an exposed human brain that pulsated 1.5 mm at the surface.

Cerebral Cortex↗