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Biomedical subjects

M D Shaw

Publications and source records attributed to M D Shaw.

At least 55 records · Page 3Linked to original sources
PubMed1986

Differences between neurological and neurosurgical approaches in the management of malignant brain tumours.

The management and outcome in 205 patients diagnosed as having cerebral gliomas over five years were reviewed. Patients referred to neurologists and neurosurgeons had similar clinical features and similar results on computed tomography. Patients referred to neurologists underwent burr hole biopsy less often and had better short term morbidity than patients referred to neurosurgeons, although final outcome was the same in both groups. Few patients underwent other surgical procedures. Referral for radiotherapy was usually by neurosurgeons, although this did not significantly affect long term survival. The implications for the management of patients with primary malignant brain tumours and the need for prospective studies are discussed.

Adolescent↗
PubMed1986

Arteriovenous malformations of the brain: natural history in unoperated patients.

Two-hundred and seventeen patients from a total population of 343 patients with arteriovenous malformations, were managed without surgery. Follow up was for a mean of 10.4 years. Using life survival analyses, there was a 42% risk of haemorrhage, 29% risk of death, 18% risk of epilepsy and a 27% risk of having a neurological handicap by 20 years after diagnosis in unoperated patients.

Adolescent↗
PubMed1985

Idiopathic spinal extradural lipomas: three cases and review of the literature.

Three cases of extradural spinal lipomas in adults are described in which there was no association with steroids. In all three cases the tumors were situated in the lumbar region and the patients were muscular, nonobese males. Two of the three cases had long histories contrary to those previously reported. Preceding transient neurological symptoms were noted in two of the three cases. The etiology of this phenomenon is discussed. It is possible that these lipomas, which are not associated with steroids, may represent a different spectrum of disease.

Adult↗
PubMed1985

Morphology of motoneurons in a mixed motor pool of the cat facial nucleus that innervate orbicularis oculis and quadratus labii superioris, stained intracellularly with horseradish peroxidase.

Retrograde tracing with horseradish peroxidase showed that motoneurons to two distinct muscles, the orbicularis oculis and quadratus labii superioris, are intermixed within the dorsolateral subnucleus of the cat facial nucleus. Intracellular electrodes were used to identify and fill the motoneurons of the dorsolateral subnucleus with horseradish peroxidase. Soma diameters averaged 55 micron. The average number of primary dendrites was 11.6. The area covered by the dendritic trees varied in shape according to the position of the soma within the subnucleus. Axon hillocks were seen arising in many orientations, bearing no apparent relation to subsequent axonal path, cell position within the nucleus or somatic geometry. Motoneurons to the two muscles appeared to be indistinguishable on the basis of morphology, even though they appear to be functionally independent. Their functional differences are not reflected in any measure of somadendritic shape studied here. Of further interest is the variability in shape associated with the neurons's position within the subnucleus. We conclude that many details of dendritic shape do not reflect specific physiological function.

Animals↗
PubMed1985

Dipyridamole and postoperative ischemic deficits in aneurysmal subarachnoid hemorrhage.

Recent evidence has suggested that the delayed cerebral ischemic deficits that often follow surgery for aneurysmal subarachnoid hemorrhage (SAH) may be due to a proliferative vasculopathy. This vascular pathology may result from an interaction between the platelets and the vessel wall. A single-blind controlled trial of dipyridamole administration in 677 patients presenting with SAH (of whom 348 came to surgery) was undertaken to test the hypothesis that the modification of platelet behavior might reduce the incidence of ischemic deficits. Blind independent assessment of the outcome in the surgical group based on the Glasgow Outcome Scale and the specific neurological deficits revealed no significant differences between the control and treatment groups.

Blood Platelets↗
PubMed1984

Brain abscess secondary to paranasal sinusitis.

Paranasal sinusitis is the commonest source of infection causing a subdural and frontal lobe abscess and is associated with a mortality of 25 per cent. The ear, nose and throat surgeon should be consulted by his neurosurgical colleague at the earliest stage of management in order to deal with the primary source of infection.

Adolescent↗
PubMed1984

Brain abscess secondary to otitis media.

Otogenic brain abscess still occurs despite advances in antibiotics. The possible diagnosis should be disproved rather than ignored in any patient who presents with a discharging ear and who has any intracranial symptoms. Otogenic brain abscess carries a 47.2 per cent risk of a fatal outcome and those patients who survive have a 95 per cent risk of developing epilepsy.

Adolescent↗
PubMed1984

Blinking and associated eye movements in humans, guinea pigs, and rabbits.

Recordings of upper eyelid movements in humans, guinea pigs, and rabbits demonstrated that all three species displayed qualitatively similar patterns of eyelid movement. The relation between amplitude, duration, and maximum velocity in rabbits and humans was nearly identical. Guinea pig blinks were faster than those of rabbit and man. Electromyographic (EMG) recordings in humans demonstrated that the orbicularis oculis muscle participated in downward movement of the upper eyelid during blinks and eyelid closure but did not participate actively in the downward lid movement occurring with gaze changes. When looking straight ahead, the estimated stiffness and viscosity of the upper eyelid were 10 g/mm and 0.38 g X s X mm-1 for humans and 1.17 g/mm and 0.062 g X s X mm-1 for rabbits. Upward and abducting rotations of the eye accompanied blinks in rabbits and guinea pigs. Simultaneously, the eyeball retracted (translational movement) into the orbit. These translational and rotational eye movements resulted from contraction of the retractor bulbi muscle and cocontraction of antagonistic extraocular muscles. The data suggested that humans also retracted the eye during voluntary blinks. The retraction produced a rotation of the eye toward a "primary position" rather than a rotation in one specific direction. The relationship between the maximum velocity, duration, and amplitude of the down phase of a blink may be expressed as a single equation, maximum velocity = c X average velocity, where c is a constant. The same relationship, with a similar value for c, also describes saccadic eye movements and rapid skeletal movements. This implies that all three movements employ comparable neural mechanisms.

Animals↗
PubMed1983

The locations of stapedius and tensor tympani motoneurons in the cat.

The numbers and locations of motoneurons to the stapedius and tensor tympani muscles were determined by retrograde transport of horseradish peroxidase. Stapedius motoneurons lay outside the traditionally recognized facial nucleus, in several distinct locations: (1) in the interface between the facial nucleus and the superior olive; (2) in a thin, scattered lamina of somewhat smaller cells spread dorsal to the facial nucleus; and (3) in a cluster located ventromedial to the rostral third of the facial nucleus. Some cells also lay dorsal to the superior olive or scattered in the reticular formation, just medial to the descending loop of the facial nerve. Tensor tympani motoneurons also lay outside the traditionally recognized trigeminal motor nucleus, in an area just ventral to it. Both motoneuron pools were large, producing innervation ratios that establish stapedius and tensor tympani among the most finely innervated muscles yet studied. The degree of intermingling of large and small cells in these pools may explain, in part, why it has been easier to identify slow muscle fibers physiologically in tensor tympani than in stapedius.

Animals↗
PubMed1983

The effectiveness of prophylactic anticonvulsants following neurosurgery.

One hundred and two patients who underwent supratentorial procedures for neurosurgical conditions, which are known to carry a high incidence of postoperative seizures, have been given prophylactic anticonvulsant medication. This preliminary analysis has failed to demonstrate any dramatic effect on the postoperative incidence of seizures in the first six months as the result of this policy. There has been a high incidence of serious side effects, but compliance has not been a major problem. This long-term study is continuing, though with a modified protocol.

Anticonvulsants↗
PubMed1983

Direct projections from vestibular nuclei to facial nucleus in cats.

Postsynaptic potentials were recorded from motoneurons in the facial nucleus in response to stimulation of the vestibular and trigeminal nerves. The motoneurons were identified by antidromic activation from their peripheral axons. Disynaptic excitatory and inhibitory postsynaptic potentials (EPSPs and IPSPs) and mixed EPSP/IPSPs were recorded in response to vestibular nerve stimulation, ranging in latency from 0.9 to 2.1 ms, with most at 1.5 ms. Activity in secondary vestibular axons recorded within the facial nucleus occurred at a latency of 0.7-1.1 ms. The amplitudes of the vestibular postsynaptic potentials were small, generally less than a millivolt, but double shocks produced marked summation. The average time to peak of ipsilateral vestibular EPSPs, 1.1 ms, was faster than that of either ipsilateral IPSPs, 1.6 ms, or contralateral EPSPs, 1.4 ms. The double-spiked vestibular activity was detectable in double-peaked PSPs. Disynaptic EPSPs, ranging in latency from 2.0 to 3.0 ms, were recorded in response to trigeminal nerve stimulation. The average time to peak was 1.3 ms. The multiple-spiked activity of the trigeminal neurons was detectable in multipeaked EPSPs. Inhibitory ipsilateral effects (Vi IPSPs) were recorded twice as often as excitatory ipsilateral effects (Vi EPSPs), being found in 29% versus 15% of the motoneurons. Contralateral effects were found in 13% of the motoneurons studied, and almost all were excitatory. Analysis of synaptic potential shapes suggested that the excitatory and inhibitory vestibular synapses probably contact distal dendrites preferentially, with the excitatory connections being somewhat closer to the soma. The trigeminal inputs probably contact the facial motoneurons more extensively near the soma. Horseradish peroxidase was injected into the facial nucleus, and retrograde uptake by vestibular neurons was studied. The majority of filled vestibular neurons was ipsilateral to the injection site, especially in the medial vestibular nucleus, ventral y group, and supravestibular nucleus. On the contralateral side, filled vestibular cells were found almost exclusively in the medial nucleus. Filled cells were also noted in the trigeminal nucleus, predominantly ipsilaterally at all rostrocaudal levels. We have demonstrated monosynaptic projections to facial motoneurons from both vestibular and trigeminal nuclei. The trigeminal input is likely to be involved in facial reflexes, especially blinking and grimacing. The afferent vestibular population overlaps that going to the oculomotor and cervical motoneurons; these projections may be collaterals of single vestibular neurons.4+.

Animals↗
PubMed1982

Generation of motoneurons in the rabbit brainstem.

Autoradiography of 3H-thymidine incorporation was used to determine the time of origin of motoneurons in the rabbit brainstem. With the exception of the facial nucleus, neurons of the branchial motor column originated earlier (days 9 and 10) than somatic motor column neurons (day 11). Labeling was obtained as early as embryonic day 8 for many motor nuclei and the mesencephalic trigeminal nucleus. The significance of temporal patterns of neurogenesis is discussed.

Abducens Nerve↗
PubMed1982

The incidence of epilepsy after ventricular shunting operations.

Overall, the risk of developing postoperative epilepsy following the insertion of an internal ventricular drainage system is 24%. Infection of the system was noted to be associated with a higher risk. The question of prophylactic anticonvulsant therapy is discussed.

Adolescent↗