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Biomedical subjects

R Levinthal

Publications and source records attributed to R Levinthal.

13 recordsLinked to original sources
PubMed1979

Effect of proximal occlusion on anastomosis patency in dogs.

This study compared the superficial temporal-middle cerebral artery (STA-MCA) anastomosis patency in animals with and without proximal embolic middle cerebral artery (MCA) occlusion. Sixteen dogs underwent STA-MCA bypass in association with silicone embolization of the MCA via an internal carotid injection. Animals re-explored 3 to 5 days postoperatively with evaluation of anastomosis patency by Evans blue injection and direct cutting of the STA demonstrated that 10 of 10 dogs with proximal MCA emboli had a patent STA-MCA anastomosis, whereas only 2 of 6 animals without an embolus lodged in the proximal middle cerebral artery had a patent connection. The likelihood of the anastomosis remaining open seems to be greatly influenced by the potential flow gradient between the extracranial and intracranial circulations (Neurosurgery, 5: 596--597, 1979).

Animals↗
PubMed1978

Fascicular nerve allograft evaluation. Part 1: comparison with autografts by light microscopy.

In a comparative experiment, transplantation of orthotopic nerve fascicle was performed on 100 sciatic nerves between inbred, antigenically identified rats. The authors studied cellular response, macrophage reaction, connective-tissue reaction, myelination, and distal/proximal axonal ratios, but no difference could be established between allografted and autografted fascicles after 2 months. Moreover, there was no evidence of any graded rejection phenomenon dependent on differences of tissue typing. Theories for the decreased antigenic reaction of nerve fascicles are proposed.

Animals↗
PubMed1978

Fascicular nerve allograft evaluation. Part 2: comparison with whole-nerve allograft by light microscopy.

Orthotopic whole-nerve and fascicular nerve grafts were transplanted between inbred rats with known histocompatibility antigen structure. In general, the whole sciatic nerves demonstrated a graded rejection response dependent upon the degree of tissue histocompatibility differences. The fascicular grafts, however, had evidence of greatly decreased rejection and no stigma of a graded response dependent on degree of variability of tissue typing. Limitations of the experiment are outlined, and the possible avenues of further research are briefly discussed.

Animals↗
PubMed1978

Preliminary observation on the immunology of nerve allograft rejection.

A preliminary experiment was devised to delineate the specificity of nerve allograft rejection. Skin grafts were performed between inbred strains of Fisher, AgB1, and Buffalo, AgB6, rats to determine the time required for a first set rejection, which occurred at day 9. Skin grafts also were performed two weeks after orthotopic placement of whole nerve or fascicular grafts. The rats that had previously been exposed to whole nerve showed skin graft rejection at six days, while those exposed to nerve fascicle demonstrated skin graft rejection at seven days. Fascicular whole nerve allografts and autografts were compared histologically at seven, 12, 19 and 28 days after grafting. The whole nerve allograft consistently showed gross and microscopic evidence of lymphocytic infiltration consistent with rejection involving the perineural connective tissues. Antigens obviously are present in sufficient levels in both the nerve and surrounding connective tissue, but at least, theoretically, there are some advantages to the use of fascicles versus the whole nerve.

Animals↗
PubMed1978

Intimal dissection of the superficial temporal artery.

Three patients who underwent superficial temporal-middle cerebral artery anastomosis demonstrated a dissection of the intima of the superficial temporal artery at operation. The fact that this abnormality had not been appreciated previously in surgical series and that it and other anatomical variants may account for "technical failures" of anastomoses is elucidated. The authors describe their successful technique for suturing the intimal flap.

Cerebral Arteries↗
PubMed1977

Comparison of fascicular, interfascicular and epineural suture techniques in the repair of simple nerve lacerations.

Simple lacerations of dog anterior tibial nerves were repaired utilizing fascicular interfascicular, and epineural suture techniques. Two months following repair, the involved regions of the nerve were removed and stained with hematoxylin and eosin, Weil, Bielschowsky, and Masson trichrome stains. An independent, unbiased observer rated proximal and distal myelin, connective tissue responses, and proximal to distal axon counts. The proportion of proximal to distal axons revealed no significant difference between fascicular (77%) and epineural (67%) neurorrhaphy, but showed a significant beneficial effect of fascicular suture to the interfascicular (52%) repair (significance at less than 0.02). Masson stain revealed dense connective tissue responses, but the axon counts were adversely affected only when the separate fascicles showed internal disruption by connective tissue. In general, distal myelinization was mildly superior with the fascicular neurorrhaphy technique. It appears that in simple lacerations in nerves which are repaired via direct end-to-end suture, there is no significant advantages to fascicular over epineural repair; however, there is a definite deleterious effect of interfascicular neurorrhaphy. The theoretical and technical implications of these findings are discussed.

Animals↗
PubMed1977

Traumatic intracerebral hematoma with stable neurological deficit.

The possibility of an intracerebral hematoma may be overlooked in the presence of a "fixed" neurologic deficit. The clinical complex that is emphasized is composed of (a) ipsilateral cranial trauma, (b) early development of focal neurological deficit, (c) a plateau in the subsequent course of the disease, (d) the delayed appearance of a positive radioactive isotope scan, and (e) a focal area of distorted vessels in angiographic studies. The availability of the computer tomographic scan has made the diagnosis of intracerebral hematomas more certain but it is important that the possibility of a hematoma be considered and pertinent investigations be performed. Even after diagnosis, an operative procedure may be delayed in patients who are neurologically stable. In the five cases presented, the diagnosis of cerebral contusion led to a delay in operative evacuation which was associated with improvement in the previously stable neurological deficit.

Adolescent↗
PubMed1976

Detection of small trigeminal neurinomas.

Four cases of trigeminal neurinoma are reviewed with particular attention to clinical signs and symptoms, lumbar puncture, electroencephalogram, brain scan, plain skull and tomographic radiographs, and angiographic and pneumoencephalographic findings. Pneumoencephalography, with special tomographic projections to identify various portions of the trigeminal nerve, delineated the tumor in all cases. Tumor removal was complete in three patients and nearly complete in the fourth. There was no operative morbidity or mortality.

Female↗
PubMed1976

A simple method for continuous pressure recording.

A relatively simple, nonoperative, percutaneous procedure for recording continuous cerebrospinal fluid pressure was carried out on 12 patients at UCLA Hospital. The experience with pressure recording in these patients has demonstrated no mortality or permanent sequelae and the technical character of the records has been excellent. This technique could make continuous pressure recording more easily available to the average practioner. Other uses for this procedure are also suggested.

Humans↗
PubMedDate not supplied

Effect of STA-MCA anastomosis on the course of experimental acute MCA embolic occlusion.

The experiments in this report were designed to evaluate the effect of superficial temporal-middle cerebral artery (STA-MCA) anastomosis on the course of middle cerebral artery (MCA) occlusion by emboli while avoiding a vessel clipping technique as well as the use of long-acting barbiturate anesthesia. Dogs were divided into 3 general groups: A) embolus placement 1 h following anastomosis; B) embolus placement 5 h prior to anastomosis; C) control group without anastomosis. Anastomosis prior to MCA occlusion has a favorable clinical effect and reduces the size of an infarction. Anastomosis 5 h after embolus placement is deleterious unless other therapeutic modalities can be shown to delay the course of infarction.

Acute Disease↗
PubMedDate not supplied

Long-term assessment of cerebral perfusion following STA-MCA by-pass in patients.

A prospective study of mean hemispheric cerebral blood flow (CBF) correlated with clinical status has now been completed for the past 54 months. Thirty-eight patients underwent superficial temporal to middle cerebral artery (STA-MCA) by-pass. They were compared with 22 patients with similar arteriographic lesions and clinical symptoms, treated medically throughout the same interval of time. Assignment to either treatment group was not randomized but depended solely on choice of patient or treating physician. Both groups were matched for age, clinical symptoms, angiographic abnormalities, and CBF values. All patients had proximal occlusion of one internal carotid artery or intracranial occlusive disease of the internal carotid or middle cerebral arteries. CBF measurements and clinical evaluations were repeated at regular intervals up to 54 months following surgery or institution of medical treatment. Mean follow up interval after STA-MCA by-pass was 28.7 months and for medical treatment was 29.7 months. Mean hemispheric CBF values for STA-MCA patients became significantly increased 2 weeks after operation. After that, CBF flow values decreased. At 24 months after surgery, flow values for surgically treated patients were significantly higher than among those treated medically, although there were no differences in flow values between the two groups at 3, 6, 12, 36 and 48 months. Prospective clinical evaluations after STA-MCA by-pass were as follows: 12 (32%) improved with cessation of TIAs and/or neurological improvement, 16 (42%) remained unchanged, 7 (18%) deteriorated (due to new or recurrent strokes) and 3 (8%) expired. Clinical results were the same for medical treatment: 6 (27%) improved, 10 (46%) unchanged, 4 (18%) deteriorated due to new or recurrent stroke, and 2 (9%) expired.

Adult↗