Biomedical subjects
Publications and source records attributed to M B Pritz.
A simple technique to lengthen the distal catheter of ventriculoperitoneal shunts is described. This method, which utilizes a guidewire, has been successful in elective shunt revisions in eight children.
Immunoreactivity to antisera directed against a variety of calcium binding proteins was investigated in the thalamic reticular nucleus of one species of reptiles, Caiman crocodilus. Cells and fibers were immunoreactive for parvalbumin whereas fibers but not neurons were immunoreactive for calbindin and calcitonin gene related peptide. These data support the observations that Caiman thalamic reticular nucleus contains at least two neuronal populations. One group, whose cells are immunoreactive for parvalbumin, forms at least part of the projection to the dorsal thalamus. The other group, which contains qualitatively different and sparser number of neurons, is immunoreactive for glutamic acid decarboxylase.
Tumours located anterior to the cervicomedullary junction have been most commonly approached via one of two routes: anterior/transoral or posterolateral. Each of these surgical corridors can pose potential pitfalls. To circumvent these problems, a lateral suboccipital approach in conjunction with an upper cervical hemilaminectomy has been used. Selecting an appropriate surgical corridor between the lower cranial nerves (IX through XII), the vertebral artery, and the posterior inferior cerebellar artery has allowed satisfactory tumour removal. A three-dimensional picture of tumour location and relationship to surrounding neural and vascular structures is obtained preoperatively from computed tomography and magnetic resonance. Arteriography is essential to determine the origin, course, and relation of each vertebral to the tumour as well as the contribution of each vertebral to the basilar. In instances of abnormalities in the posterior circulation, evaluation of the carotid contribution to the basilar is crucial. The advantages of this approach are several. First, a direct view of the anterior surface of the lower brainstem und upper cervical cord is obtained. Second, surgery is undertaken in a sterile field in which the dura can be closed watertight. Third, neither mastoidectomy nor transposition of the vertebral artery is required. The major difficulty is the necessity to operate through narrow surgical corridors bounded by the lower cranial nerves, vertebral and posterior inferior cerebellar arteries, and the lower medulla and upper cervical cord. These structures provide the major obstacles to dissection as well as the primary causes of morbidity.
The case of a 44-year-old woman with tinnitus of her left ear is presented. An arteriogram demonstrated a posterior dural arteriovenous malformation (AVM) on that side with drainage via dilated cortical veins into the superior sagittal sinus. No intervention was undertaken. When angiography was repeated 7 years later, no dural AVM was seen.
Aneurysms of the vertebral artery and its branches are relatively uncommon lesions. Their anatomy and presentation can be quite variable. A spectrum of aneurysms of the vertebral artery is presented to illustrate the neuroradiological evaluation, surgical treatment, and perioperative management of these complex lesions.
The presence of a reptilian thalamic reticular nucleus was investigated in Caiman crocodilus. Injections of horseradish peroxidase made into the dorsal thalamus produced retrogradely labeled neurons in the nucleus of the dorsal peduncle of the lateral forebrain bundle. A separate population of thalamic neurons located in the nucleus of the dorsal peduncle of the lateral forebrain bundle with morphology different from those neurons projecting to the dorsal thalamus were found to be immunoreactive for glutamic acid decarboxylase. Taken together, these findings suggest that Caiman, like mammals, contain a thalamic reticular nucleus but that thalamic organization in Caiman differs significantly from that of mammals.
A patient who sustained a gunshot wound to the neck and subsequent blunt trauma is presented. No angiogram was performed after the initial injury. Subsequently, the patient developed a cerebral embolus from a thrombus dislodged from a pseudoaneurysm of the cervical carotid artery, resulting in complete occlusion of the distal internal carotid artery. After antiplatelet therapy, the distal internal carotid artery recanalized, and the pseudoaneurysm occluded spontaneously. We stress the need for the use of arteriography in the initial evaluation of penetrating injuries to the neck and the utility of repeated arteriograms for further treatment planning as these traumatic lesions can change with time.
Ascending projections to the thalamus from a midbrain somatosensory area were investigated in a reptile, Caiman crocodilus. Connections were determined utilizing horseradish peroxidase (HRP) neurohistochemistry in which tetramethylbenzidine was the chromogen. Anterograde experiments, in which HRP injections were placed into the midbrain, revealed bilateral projections to the medialis complex of the dorsal thalamus. These observations were confirmed by HRP injections into the medialis complex which retrogradely labeled neurons in the midbrain somatosensory area bilaterally. An ipsilateral predominance of connections was observed in both anterograde and retrograde HRP experiments. This somatosensory target in the thalamus, the medialis complex, is located between the auditory and visual nuclei. This organization and neural circuitry of somatosensation is similar to that of auditory and visual systems that terminate in the midbrain of Caiman.
Brains of reptiles, Caiman crocodilus, were processed by standard immunocytochemical methodology using a polyclonal antibody to glutamic acid decarboxylase (GAD) as well as several monoclonal antibodies to GAD. No neurons immunoreactive for GAD, GAD(+), were observed in the dorsal column nucleus, although GAD(+) puncta were seen. These findings suggest that in Caiman, the dorsal column nucleus, like the dorsal thalamus, lacks local circuit neurons.
A midbrain somatosensory area was identified in reptiles Caiman crocodilus, by orthograde degeneration techniques after midcervical spinal cord transections or after dorsal column lesions. Terminations of these somesthetic inputs were located in a caudal lateral part of the central nucleus of the torus semicircularis and contiguous dorsal mesencephalon. Dorsal column projections were contralateral while spinal connections were mainly ipsilateral. In order to confirm the results of the anterograde degeneration experiments independently, injections of horseradish peroxidase were placed in this midbrain somatosensory recipient area. Retrogradely labeled neurons were identified in the contralateral dorsal column nucleus. These findings indicated that the pattern of degeneration seen after dorsal column lesions originated from the dorsal column nucleus itself. The results of the present experiments when compared with similar studies in other amniotes emphasize the following two points. First, dorsal column and spinal cord projections to the midbrain are features common to reptiles, birds, and mammals. Second, since these pathways and midbrain somatosensory terminations are common to amniotes, dorsal column nucleus and spinal circuits to the midbrain and their mesencephalic projection areas are phylogenetically ancient.
Brains of reptiles, Caiman crocodilus, were processed by standard immunocytochemical methodology using a polyclonal antibody to gamma-aminobutyric acid (GABA) raised in rabbit and a polyclonal antibody to glutamic acid decarboxylase (GAD) raised in sheep. No GABA(+) or GAD(+) cells or puncta were observed over any thalamic nucleus known to project to the telencephalon in Caiman. These findings suggest that all thalamic nuclei that project to the telencephalon in Caiman lack intrinsic cells and presumably direct inhibitory input mediated by GABA.
A 3-year-old boy with a septated syrinx and several other dysraphic features is presented. The literature regarding the cause, diagnosis, and pathology of septation in syringomyelia is reviewed. This case raises two points. First, the septated pattern may be associated with an elevated pressure in the syrinx. Second, despite the septations, the syrinx may communicate freely.
Small injections of horseradish peroxidase (HRP) restricted solely to the general cortex in reptiles, Caiman crocodilus, resulted in retrogradely labeled cells located bilaterally in the nucleus dorsolateralis anterior of the thalamus. Larger cortical injections of HRP labeled greater numbers of nucleus dorsolateralis anterior cells. HRP injections designed to label as much cortex as possible resulted in very few unlabeled ipsilateral neurons in the nucleus dorsolateralis anterior. The percentage of these unlabeled cells was less than 1%. These data indicate that the nucleus dorsolateralis anterior contains few, if any, intrinsic or local circuit neurons.
Projections to the dorsal column nucleus were investigated in the reptile Caiman crocodilus following application of horseradish peroxidase (HRP) crystals to the cervical spinal cord after dorsal myelotomy. Brains were processed for HRP histochemistry by use of tetramethylbenzidine as the chromogen. Injection of the dorsal funiculus alone labelled axons that terminated solely in the ipsilateral dorsal column nucleus. Application of HRP that extended beyond the dorsal funiculus labelled axons that terminated in brainstem areas in addition to the dorsal column nucleus depending upon the injection site. Retrogradely labelled neurons in the brainstem were seen only after HRP injections that extended beyond the dorsal funiculus and varied depending upon the injection site. Dorsal funiculus fibers travel rostrally and turn laterally to reach more anterior portions of the dorsal column nucleus. Fibers peel off in an oblique ventrolateral fashion to terminate in the posterior part of the nucleus where boutons are intermixed with fibers. The anterior portion of the nucleus contains a greater proportion of axon terminals as compared to fibers than does the posterior part. A graphic reconstruction of the dorsal column nucleus was made by superimposing serial sections to view the nucleus in transverse, sagittal, and horizontal planes.
Large injections of horseradish peroxidase were placed in the non-cortical telencephalon in a reptile, Caiman crocodilus. The number of retrogradely labeled and unlabeled neurons in two sensory thalamic nuclei, nucleus rotundus (vision) and nucleus reuniens pars centralis (audition) were counted. The percentage of unlabeled cells in each nucleus was less than 1%. These data suggest that each of these thalamic nuclei contain few, if any, intrinsic or local circuit neurons.
A case of neurenteric intraspinal cyst with vertebral anomalies is reported; the cyst contained gastric mucosa. MRI and CT provided useful information.
Theoretical and practical aspects of monitoring cardiac and blood volume status in neurosurgery patients are discussed. Groups of patients unique to neurosurgeons who might benefit from this approach include the following: those with intracranial hypertension; those undergoing blood volume expansion as a treatment for a variety of cerebrovascular disorders; and those with significant cardiovascular-respiratory problems undergoing high-risk or prolonged neurosurgical procedures. In addition, the generation of Starling-type ventrical function curves to be used in fluid management for blood volume expansion in the treatment of neurologic deficits associated with vasospasm is discussed.
Three patients with recent stroke underwent carotid endarterectomy 1, 4, and 8 days after the onset of maximal symptoms. In each case, computed tomography (CT) demonstrated recent cerebral infarction and cerebral arteriography showed high grade cervical carotid stenosis. No patient developed worsened neurological symptomatology, intracerebral hemorrhage, or vasomotor paralysis. These results suggest that carotid endarterectomy, if indicated, can be performed safely after acute stroke under certain conditions. These criteria include the following: normal level of consciousness, relatively small cerebral infarction without mass effect on CT, and meticulous control and monitoring of systemic blood pressure during the perioperative period. These initial observations suggest that a specific subgroup of patients with recent cerebral infarction may be able safely to undergo carotid endarterectomy shortly after diagnosis.