Search PubMed⌕ Search

Biomedical subjects

R M Crowell

Publications and source records attributed to R M Crowell.

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

External pneumatic calf compression reduces deep venous thrombosis in patients with ruptured intracranial aneurysms.

We evaluated the ability of intermittent external pneumatic calf compression to prevent deep venous thrombosis after subarachnoid hemorrhage from ruptured intracranial aneurysms. Fifty-six subarachnoid hemorrhage patients not given external pneumatic calf compression were compared with 90 patients who had calf compression after their subarachnoid hemorrhages. Both groups of patients were on strict bedrest for 7 to 21 days after aneurysm rupture, and both received epsilon-aminocaproic acid, 30 to 36 g/day intravenously, until operation. The risk factors in the two groups were similar, and the nursing and medical care did not seem to differ. Of patients without external pneumatic compression, 18% had venographically proven deep venous thrombi, which contrasts with 6% of patients receiving calf compression. This was a significant difference (P less than 0.05; chi 2). These retrospective data suggest that external pneumatic calf compression helps to prevent deep venous thrombosis in patients with subarachnoid hemorrhage when delayed operation, bedrest, and antifibrinolytic agents are used.

Adult↗
PubMed1986

Neuroradiological and electroencephalographic features in a case of temporal lobe status epilepticus.

A patient with medically intractable status epilepticus of temporal lobe origin is presented. A computed tomogram showed a low density area adjacent to the midbrain, possibly related to atrophy of the medial temporal lobe. Cerebral angiography revealed early filling veins and an anterior temporal blush. Magnetic resonance (MR) scanning (T2 weighted images) showed increased signal intensity in the region of the amygdala and anterolateral left temporal lobe. Ictal activity was recorded from scalp electrodes over the left temporal area, and many paroxysms were recorded from cortical surface electrodes. An anterior temporal lobectomy revealed only gliosis. The cerebral blood flow changes accompanying status epilepticus of focal origin are reviewed, and a possible relation of electroencephalographic, angiographic, and MR findings is discussed.

Adult↗
PubMed1986

Optochiasmatic arachnoiditis with treatment by surgical lysis of adhesions, corticosteroids, and cyclophosphamide: report of a case.

A 24-year-old woman presented with progressive optochiasmatic arachnoiditis causing progressively worsening visual loss associated with headache and amenorrhea. Treatment with the standard initial therapy of dexamethasone, warfarin, and dipyridamole was unsuccessful at halting her disease process. Surgical lysis of adhesions led to a temporary improvement and then deterioration. A course of therapy with cyclophosphamide was initiated and her response to this therapy resulted in resolution of her headaches, return of her vision to normal, and resumption of her normal menstrual cycles.

Adrenal Cortex Hormones↗
PubMed1986

Regional cerebral blood flow assessment prior to balloon detachment in the treatment of intracranial giant aneurysms.

Three patients with giant aneurysms (2 internal carotid and 1 anterior communicating) were treated by internal carotid occlusion with a detachable balloon. 133Xe regional cerebral blood flow (rCBF) was performed on each patient on admission. Due to low CBF, one patient received a superficial temporal artery--middle cerebral artery (STA-MCA) bypass. The rCBF was repeated when the balloon was inflated in the internal carotid prior to detachment of the balloon. All three patients were discharged within one week with no neurologic deficit. The rCBF assessment appears useful to decide which patient will tolerate acute balloon occlusion of the internal carotid and to help select patients who will need an extra-cranial-intracranial (EC-IC) bypass to avoid ischemic complication.

Aged↗
PubMed1986

Surgical management of cerebrovascular disease.

After careful evaluation to pinpoint abnormal vessels, surgery may be performed, either to improve blood flow or to repair leaky vessels. This approach can serve to prevent future stroke events.

Arteriovenous Shunt, Surgical↗
PubMed1985

Neuropathological changes related to the transorbital application of ethyl 2-cyanoacrylate adhesive to the basal cerebral arteries of cats.

The long-term toxic effects of ethyl 2-cyanoacrylate adhesive were evaluated histologically in 25 cats. Fresh medical- or commercial-grade adhesive was introduced transorbitally into the subarachnoid space in the vicinity of the right middle cerebral artery. Three sham-operated animals served as controls. The animals were sacrificed at intervals ranging from 2 days to 6 months. For both medical- and commercial-grade adhesive, neuropathological examination disclosed acute and chronic granulomatous inflammation of the meninges and evidence of severe vascular damage, including vessel wall necrosis, inflammation, thrombosis, and occasionally hemorrhage. Most animals showed cerebral infarcts of variable size in the territories of distribution of the basal arteries which were in contact with adhesive. The results of this study show that ethyl 2-cyanoacrylate is capable of producing severe arterial and parenchymal damage. The risk of its deleterious effects should be weighed against its potential benefits. Clinical experience would suggest that ethyl 2-cyanoacrylate can be used in difficult situations as long as care is taken to protect the brain and local blood vessels.

Animals↗
PubMed1985

Aneurysms and arteriovenous malformations.

This article discusses intracranial aneurysms and subarachnoid hemorrhage in terms of prevalence, etiology, pathology, pathophysiology, and clinical presentation. Evaluation of patients, medical management, and surgical treatment are detailed as are results for selected aneurysms.

Anesthesia, General↗
PubMed1984

Selective necrosis and total necrosis in focal cerebral ischemia. Neuropathologic observations on experimental middle cerebral artery occlusion in the macaque monkey.

Temporary (15 minutes to 24 hours) or permanent focal cerebral ischemia was induced in 87 awake monkeys (Macaca mulatta and Macaca fasicularis) by transorbital snare ligation of the middle cerebral artery (MCA) and neuropathological evaluation was carried out two weeks later. The size, location and histology of lesions varied within each time-period of MCA occlusion. However, most animals that underwent long-term ischemia (eight hours to permanent) had a single, confluent infarct involving deep and sometimes cortical structures. These animals had total necrosis chracterized by: 1. indiscriminate involvement of white and gray matter, 2. relatively sharp margins containing astrocytic and mononuclear cells, 3. an inner zone of liquefaction, infiltrated with fat-laden macrophages and newly formed blood vessels. Animals that underwent moderate to short-term ischemia (30 minutes to four hours) showed multiple, non-confluent deep infarcts. These animals had selective necrosis characterized by: 1. involvement of gray matter and relative sparing of white matter, 2. poorly circumscribed, multiple and often perivascular lesions with incomplete tissue destruction, 3. preferential loss of neurons and proliferation of reactive astrocytes and microglia.

Animals↗
PubMed1984

Effect of naloxone on experimental stroke in awake monkeys.

Naloxone has recently been reported to be of benefit in the treatment of central nervous system ischemia. To study the effect of naloxone in an experimental stroke model, we subjected 40 awake monkeys to middle cerebral artery (MCA) occlusion 2 weeks after the placement of a MCA ligature by a transorbital technique. Cerebral blood flow (CBF) was monitored with stereotactically placed H2 electrodes, and the neurological course was serially recorded. Infarct size was determined 2 weeks after MCA occlusion. Twenty animals served as control and received no naloxone; 10 of these underwent permanent occlusion, and 10 underwent 4-hour MCA occlusion. In 25 treatment animals, naloxone was administered in three different intravenous dosages: (a) naloxone, 2-mg/kg bolus 20 minutes postocclusion and 2 mg/kg/hour X 4 hours, in 10 animals with permanent MCA occlusion; (b) naloxone, 10-mg/kg bolus 20 minutes postocclusion and 10 mg/kg/hour X 4 hours, in 10 animals with 4-hour MCA occlusion; and (c) naloxone, 20-mg/kg bolus, in 5 animals with various neurological deficits. MCA occlusion typically produced a moderate deficit: hemiparesis, hemianopsia, and facial paresis. In most instances, naloxone in the 2- and 10-mg/kg dose regimens produced little or no change in the neurological function. CBF decreased after MCA occlusion and was unaffected by naloxone in most cases. Infarct size was not significantly different between the control and treated groups. However, the 20-mg/kg dose consistently produced a nonfunctional, transient increase in total body motor tone in normal and hemiparetic animals. Naloxone did not significantly improve useful neurological function, CBF, or infarct size in an experimental primate stroke model.

Animals↗
PubMed1984

Somatosensory evoked potentials and cortical blood flow during craniotomy for vascular disease.

It has been demonstrated that central conduction time (CCT) is slowed and that attenuation of cortical potentials occurs with reduced cerebral perfusion. During 11 craniotomies for aneurysm, arteriovenous malformation (AVM), or extracranial-intracranial (EC-IC) bypass, we continuously monitored somatosensory evoked potentials (SSEPs) and regional cortical blood flow (rCBF) as determined by a thermal flow probe. The CCT was calculated and correlated with the rCBF. In 8 of the 11 cases, the rCBF values varied within 1 SD of normal values derived from 25 measurements of nonischemic cerebral cortex. All initial CCT values were within 1 SD of normal, but 4 of 11 patients had a prolonged CCT intraoperatively. Three of these were associated with a low rCBF (14 to 31 ml/100 g/minute). One patient had postoperative confusion at the time of discharge. One patient who underwent AVM embolization had a permanent loss of SSEPs postoperatively, and his preexisting hemiparesis was more profound after operation. Finally, 1 patient's CCT improved after EC-IC bypass. This is a preliminary study that demonstrates the feasibility of monitoring CCT and rCBF during craniotomy. When rCBF values fall and the CCT slows, neurological deficit will probably occur.

Adolescent↗
PubMed1984

Beneficial effects of induced hypertension on experimental stroke in awake monkeys.

The authors performed a controlled study of induced hypertension therapy for treatment of experimental stroke in unanesthetized monkeys. Ten control and 10 treated animals were subjected to a 4-hour occlusion of the middle cerebral artery (MCA) by an implanted tourniquet. Neurological status and local cerebral blood flow (CBF) were monitored serially. Local CBF was determined by hydrogen clearance in and around the elevated 20% to 40% by intravenous infusion of phenylephrine hydrochloride. Neuropathological evaluation was performed after about 2 weeks. A 4-hour occlusion of the MCA in control animals caused moderate stable neurological deficits, moderate stable decreases in local CBF, and medium-sized infarcts. With induced hypertension, five of 10 treated animals showed neurological improvement, and eight exhibited increased CBF in the ischemic zone. Average infarct size tended to be smaller in the treated group, although the difference did not reach statistical significance. Hemorrhagic infarcts were not observed. In four animals, phenylephrine caused cardiac dysrhythmias and hypotension which were reversed by appropriate measures. In this unanesthetized primate model of moderate experimental stroke, induced hypertension had beneficial effects on neurological status, local CBF, and infarct size without causing hemorrhagic infarction. Induced hypertension may be beneficial for some clinical cases of focal cerebral ischemia.

Anesthesia, General↗
PubMed1984

Criteria for using imaging ultrasound during brain and spinal cord surgery.

Imaging ultrasonography was performed during 23 brain and five spinal cord operations with real-time B-mode instruments. Criteria for the utilization of ultrasound at neurosurgical procedures were identified in terms of assistance in the diagnosis or better definition of lesions. The diagnosis criteria were detection and exclusion. Because of the accuracy of preoperative imaging, usually little further help was provided by operative ultrasonography in detecting previously totally unknown abnormalities or excluding lesions found on positive studies. The definition criteria were localization, distinction of tissue features, and assessment of spatial relations. Operative ultrasonography was most useful when applied on the basis of these definition criteria. Operative ultrasonography was considered to be useful in 22 of 28 operations (79 per cent) in which it assisted in exposing, accessing, and extirpating disease.

Adult↗
PubMed1984

[Operative ultrasonography of the brain and spinal cord pathology].

B-mode real-time ultrasound using 5 or 7.5 MHz transducer has been employed during 21 operations for brain pathology and spinal cord lesions. Ultrasonic scanning was performed at the following operations: 10 brain tumors (4 glioblastomas multiforme, 2 astrocytomas, 1 medulloblastoma, 2 metastatic tumors), 2 brain cysts (arachnoid, epidermoid), 1 tuberculous abscess, 3 cerebral hematomas: 2 spinal cord tumors (malignant melanoma, glioma), 2 syringomyelias, 1 posterior longitudinal ligament thickening. Operative ultrasound was useful prior to dural incisions and particularly for subcortical lesions. In addition, ultrasound provided assistance at spinal cord surgery. Our experience has been reviewed and summarized in this report in terms of specific usefulness of assistance of this method which has proven helpful to the neurosurgeons. The types of assistance provided by operative ultrasonography include: Location of dural incision. Localization of brain and spinal cord lesions prior to biopsy. Diagnosis which has not been made preoperatively (e.g. necrosis or cystic area in tumor). Consistency of each lesion (e.g. solid or cystic, necrosis, loculation). Size, extent and depth of brain tumor, cyst, abscess and hematoma. Presence and extent of spinal cord syrinx. Relation of tumor to spinal cord and dura. Access route for biopsy and drainage (avoiding critical areas such as motor strip). Exclusion of bleeding or hematoma following biopsy. Confirmation of the effectiveness of drainage or resection of lesions. Relationship between pathology and surrounding anatomic structures. A number of important assistance by the utilization of ultrasound during neurological surgery have been identified.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1983

The relation of cerebral vasospasm to the extent and location of subarachnoid blood visualized by CT scan: a prospective study.

In 41 cases of verified ruptured saccular aneurysm, we prospectively predicted the presence or absence of delayed symptomatic cerebral vasospasm. CT criteria quantifying the extent and location of subarachnoid blood (developed in our previous retrospective study) were used in this prospective series of patients. Twenty-two patients had recognizable subarachnoid clots larger than 3 X 5 mm or layers of blood more than 1 mm thick (measured on reproduced images). In 20 of the 22 patients with severe significant clot or thick layer, severe vasospasm was correctly predicted and localized (2 false positives). In 19 patients with no blood, or diffuse blood, or blood outside the subarachnoid space, the absence of severe vasospasm was correctly predicted in 14 (5 false negatives). All of the false-positive and false-negative cases could be explained by inadequate CT technique. The data indicate that the extent and location of blood in the subarachnoid space determine the severity and location of vasospasm and that patients in jeopardy of developing symptomatic cerebral vasospasm can now be identified. Early preventive measures may now be assessed more accurately.

Adult↗
PubMed1983

Large and giant paraclinoid aneurysms: surgical techniques, complications, and results.

Twenty-five patients with giant (greater than 25 mm in diameter) and 9 patients with large (15 to 25 mm in diameter) aneurysms of the internal carotid artery in the ophthalmic or paraophthalmic region are reviewed. In 23 of these patients the aneurysm was clipped directly. There was 1 death in this group, and none of the survivors had disabling neurological complications outside the visual system. The other 11 patients were treated by a trapping procedure or by either common carotid ligation or internal carotid ligation in the neck. Of the 5 patients treated by internal carotid ligation preceded by an extracranial to intracranial bypass graft, 3 developed embolic complications, which in 1 patient resulted in death. One of the 4 patients treated by ligation of the common carotid artery died 1 year later from a recurrent subarachnoid hemorrhage. Of the total group, 18 patients had visual loss preoperatively as a result of aneurysmal compression; in 10 the vision was improved by operation, in 3 it was made worse, and in 2 it was unchanged. In another patient the vision continued to deteriorate slowly after common carotid occlusion, and the other 2 patients died postoperatively before vision could be assessed. The complications in the patients are described and analyzed in detail. Maneuvers found to be of value in the direct approach to these lesions are described. Of these, exposure of the internal carotid artery in the neck for temporary occlusion during clipping and thorough drilling of the anterior clinoid process and unroofing of the optic canal were particularly helpful. The literature on indirect methods of treatment by carotid occlusion with and without bypass graft is reviewed with special reference to the complications and effectiveness of each alternative. Based on this review of the literature and our experience, a treatment scheme is suggested for these aneurysms depending on their mode of presentation.

Adult↗
PubMed1983

Bilateral parietal arteriovenous malformations: report of a case.

A patient with bilateral parietal arteriovenous malformations (AVMs) is reported. The clinical presentation included seizures, coma, and signs of tentorial herniation. After the evacuation of a large left intraparietal hematoma, cerebral angiography identified a small left parietal AVM, which was excised. Mass effect and increased intracranial pressure were present at the time of the initial angiography, and the presence of a right parietal AVM was not appreciated. Postoperative cerebral angiography to document excision of the left parietal AVM then disclosed the small right parietal AVM, which was later excised. The patient has recovered very well. The natural history of AVMs and the occurrence of multiple AVMs are discussed.

Adult↗