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Biomedical subjects

S E Mackinnon

Publications and source records attributed to S E Mackinnon.

At least 37 records · Page 2Linked to original sources
PubMed2000

Nerve transfers in the upper extremity.

Restoration of extremity function following nerve injury is often unpredictable. Nerve transfers in the upper extremity are important techniques in the management of many types of peripheral nerve injury. The physiologic principles of nerve transfer lead to the indications for use. The elements of planning and execution of common nerve transfers are presented in this article.

Arm↗
PubMed1999

Evaluation of functional nerve recovery shows that allogeneic nerve graft treated with ICAM-1 and LFA-1 mAbs can be good alternative to syngeneic graft.

The objective of the study is to establish recovery results of tibial nerve defects reconstructed using allogeneic and xenogeneic graft, in host immunosuppressed with Intercellular Adhesion Molecule-1 (ICAM-1) and Lymphocyte Function Antigen-1 (LFA-1) monoclonal antibodies (mAbs). A pilot study was conducted in fifteen Fischer rats by forming a 1 cm right tibial nerve gap, then reconstructing it with 1.2 cm long grafts, namely, Wistar allogeneic, Black mouse xenogeneic, and syngeneic (n = 5/group). The main study included forty-eight rats allocated to the following groups (n = 12/group): 1) Allograft without treatment as control group. 2) Allograft with intraperitoneal ICAM-1 and LFA-1 mAbs treatment. 3) Allograft preserved in Belzers' solution including ICAM-1 mAbs plus standard intraperitoneal treatment. 4) Syngraft as benchmark. At 3, 6 and 9 weeks postengraftment walking track analysis was performed and expressed as Tibial Functional Index (TFI). Motor and compound nerve action potential across the graft conduction velocities were measured at week 10. Xenograft did not show any functional recovery and was therefore excluded from main study. However, pilot and main study results showed recovery results in both treated allogeneic groups and were comparable to benchmark syngraft. Therefore, allogeneic nerve graft could be an alternative in peripheral nerve reconstruction and spinal cord grafting.

Action Potentials↗
PubMed1999

Transfer of flexor carpi ulnaris branch of the ulnar nerve to the pronator teres nerve: histomorphometric analysis.

Partial median-nerve injury high in the upper extremity, resulting from brachial plexus neuritis or trauma, can affect the pronator teres muscle and result in the inability to pronate the forearm. A nerve transfer from an ulnar nerve-innervated branch to the flexor carpi ulnaris (FCU) muscle to the branch to the pronator teres (PT) is an attractive option in this clinical scenario. This study, a histomorphometric analysis of nine cadaver specimens harvested at the proposed FCU branch to PT branch transfer site, demonstrates sufficient similarities between the two branches in total number of nerve fibers (371.6 with SEM 35.1, and 361.9 with SEM 47.1; p = 0.87) and nerve cross-sectional area (122,181 microm2 with SEM 14,546 microm2, and 142,492 microm2 with SEM 19,633 microm2; p = 0.42), to predict a functional transfer result. In addition, clinical application of this transfer resulted in functional pronation strength of M4+.

Aged↗
PubMed1999

Peripheral nerve revascularization: histomorphometric study of small- and large-caliber grafts.

The revascularization of nerve grafts was investigated using histologic and morphometric techniques. Small-diameter nerve grafts (sciatic in the rat and sural in adult ewes) were studied, as was a large-diameter peroneal nerve graft in the ewe. Ninety-six hours after sciatic nerve engraftment, rats were injected with an intravascular fluorescent tracer. Evans blue albumin (EBA). Specimens were observed for the number of vessels perfused. Analysis showed no difference in vascular pattern between the grafted nerves and their control nerves, suggesting that spontaneous revascularization had occurred to establish a vascular tree essentially identical to the native nerve. Sural and peroneal nerve grafts were evaluated in adult ewes at 7 or 40 days post-nerve grafting. Similar to the rat sciatic nerve, the small-diameter sural nerve grafts were completely revascularized, with an equal number of perfused vessels at both time periods, with respect to control specimens. In contrast, the larger-caliber peroneal nerve grafts were not perfused at 7 days, and very poorly perfused at 40 days. This correlated with scant neural regeneration at 40 days. The finding suggests that small-diameter nerve grafts spontaneously revascularize, and revascularization using microvascular techniques is not necessary. In contrast, the larger-diameter nerve graft did not revascularize well. Such a large-diameter nerve graft would provide a suitable model to investigate the potential merits of a vascularized nerve graft.

Animals↗
PubMed1999

Strain differences in peripheral-nerve regeneration in rats.

Currently, several strains of rats are used for studies of peripheral-nerve injury and repair. The purpose of this study was to determine if significant differences in regeneration between strains exist that might influence comparison of results and interpretation of scientific conclusions. One outbred (Sprague-Dawley) and four inbred stains (ACI, Wistar-Furth, Lewis, Brown-Norway) were studied. Animals were randomized to one of two experimental conditions, undergoing either posterior tibial nerve transection and repair, or Silastic conduit repair of the posterior tibial nerve (n=6/group). Endpoint evaluations at 6 and 13 weeks included histomorphometry and walking-track analysis. Evidence of excellent regeneration was noted in all rat strains undergoing primary repair. Generally, no statistically significant differences between strains were noted, regardless of endpoint evaluation used in the primary repair group. Nerve regeneration across the conduits was either poor or not present at 6 weeks, with no regeneration at all noted in any animals in the ACI and Brown-Norway groups, and regeneration in only one or two animals in the other strains. At 13 weeks, between three and five animals in each strain showed regeneration, but functional recovery was poor. Overall, few differences in peripheral-nerve recovery appear to exist between rat strains. It seems that uniform conclusions may be drawn regardless of strain used.

Analysis of Variance↗
PubMed1999

Cold preservation of nerve grafts decreases expression of ICAM-1 and class II MHC antigens.

Cold preservation has previously been shown to decrease the antigenicity of nerve allografts, while Schwann cells remain viable. The expression of intercellular adhesion molecule-1 (ICAM-1) and class II MHC antigens, both of which have been shown to play a major role in initiating graft rejection, was studied in fresh rat nerve, and after 2 and 7 weeks of cold preservation. Ten sciatic nerves harvested from Lewis rats were cut into three segments. One segment was processed immediately, while the other ones were preserved at 5 degrees C for 2 and 7 weeks, respectively, before processing. Immunostains using specific monoclonal antibodies and alkaline phosphatase development were performed on each sample. The relative level of expression of these antigens was compared using computer-assisted densitometry. Expression of ICAM-1 was significantly decreased at 7 weeks, as compared to fresh and 2-week groups, with no statistically significant difference between fresh and 2-week nerves. Expression of class II MHC was significantly decreased at 2 and 7 weeks, compared to fresh nerves, with no statistically significant difference between the preserved groups. The decrease in antigenicity of cold-preserved nerve allografts appears to be linked to a down-regulation of ICAM-1 and MHC class II expression.

Analysis of Variance↗
PubMed1999

Peripheral nerve injection injury with antiemetic agents.

Antiemetics are widely used drugs, frequently administered to alleviate postoperative and postchemotherapeutic nausea and vomiting. While antiemetics do not induce peripheral neurotoxicity when administered systemically, it is not known whether peripheral nerve injury can occur as a result of inadvertent intraneural injection during intramuscular administration. The purpose of this study was to characterize the neurotoxic effect of three commonly used antiemetic agents (promethazine, dimenhydrinate, and prochlorperazine) as compared to saline in the rat sciatic nerve model. Intrafascicular and extrafascicular injection as well as direct application of the antiemetic drugs were performed. Nerves were harvested at 2 weeks postoperatively for histology and morphometry, with an additional sacrifice point at 8 weeks for the intrafascicular injection group. Injection injuries caused by antiemetic drugs differed depending on the agent injected and the location of injection. Extrafascicular injection and direct application caused no damage. Intrafascicular injection caused diffuse axonal injury in the promethazine and dimenhydrinate groups, while prochlorperazine caused only focal injury. Regeneration was prominent at 8 weeks in all intrafascicular injection groups in this rat model. Prochlorperazine thus appears to be less neurotoxic when injected intraneurally and should preferentially be used for intramuscular injections.

Animals↗
PubMed1999

Utility of vibration thresholds in patients with brachial plexus nerve compression.

The diagnosis of brachial plexus nerve compression is controversial due to the subjective nature of patient symptoms and the lack of objective, quantifiable tests. It has been hypothesized that quantitative sensory evaluation of sensory threshold is the most sensitive method of evaluating nerve compression, particularly in the early stages. This study evaluated the sensitivity and specificity of vibration thresholds for detection of brachial plexus nerve compression. A multiple-frequency vibrometer was used to evaluate 40 control subjects and 35 patients with brachial plexus nerve compression. Calculated sensitivity values were modest (0.49 at 63, 250, and 500 cps) with high specificity values (0.98 at 8 cps) for individual frequencies using a fifth percentile criterion. The low sensitivity values indicate that this instrument is not adequate as a screening device.

Adult↗
PubMed1999

Postradiation neural sheath sarcoma of the brachial plexus: a case report.

Sarcoma arising in the brachial plexus is a rare complication following radiation therapy, with only 7 patients reported in the literature. The absolute number of patients is likely to increase with the growth of radiation therapy to treat breast cancer. Because of its rarity, early diagnosis requires a high degree of suspicion. We present a patient with neural sheath sarcoma of the brachial plexus arising 18 years after external beam radiation for breast cancer. The interval between presentation and definitive therapy was prolonged by workup and treatment of carpal tunnel syndrome and cervical nerve root compression. The English language literature regarding postradiation sarcoma is reviewed and the clinical, radiological, and electrophysiological workup of postradiation brachial plexopathy is discussed.

Brachial Plexus↗
PubMed1999

Subjective recovery of nerve graft donor site.

Nerve graft procedures require the use of a donor nerve to supply the graft material. This results in an area of numbness in a less critical region. The purpose of this study was to assess donor site recovery using patient subjective evaluation. Thirty-one patients (mean age, 38 years) who were at least 2 years past a nerve graft procedure participated in the telephone survey. The mean time since surgery was 65 months. Donor nerves from the lower extremity were utilized in 16 patients and from the upper extremity in 15 patients. The subjective patient evaluations indicated low levels of pain, numbness, and cold sensitivity in the donor nerve sensory distribution. Patient factors, including workers' compensation and legal involvement, did not have a significant effect on recovery at the donor site. Function and daily activity were not affected significantly by donor site factors. Satisfaction with nerve graft recovery was related significantly to reported patient satisfaction of the donor site (p = 0.002).

Adolescent↗
PubMed1999

Evaluation of hand sensibility with single and double latex gloves.

The purpose of this study was to examine hand sensibility of surgeons wearing single and double latex gloves. Evaluation of hand sensibility, including cutaneous pressure thresholds, moving two-point discrimination, and static two-point discrimination, was performed on 25 surgeons (mean age 45 years). The dominant hand index finger was assessed with no glove, single glove, and double glove. The majority of surgeons had a moving and static two-point discrimination of 2 or 3 mm. The lowest cutaneous pressure thresholds were found when measured with no gloves and increased with single and double gloves. Statistically significant differences in cutaneous pressure thresholds using Semmes-Weinstein monofilaments were found for gloves versus no gloves (p < 0.0003) and single versus double gloves (p = 0.0003). Statistically significant differences in moving two-point discrimination were found for no gloves versus double gloves (p = 0.05) and single versus double gloves (p = 0.02). In conclusion, we found significant differences in hand sensation when measured with single and double gloves.

Adult↗
PubMed1999

FK506 accelerates functional recovery following nerve grafting in a rat model.

The sometimes dramatic and permanent functional deficits that result from severe peripheral nerve injuries provide compelling incentives to identify exogenous agents that may expedite axonal regrowth and avoid prolonged denervation of end organs. The purpose of this study was to identify, whether the regular systemic administration of tacrolimus (FK506) or cyclosporin A (CsA) would influence the speed and efficiency of nerve regeneration through short nerve grafts. A total of 35 Buffalo rats each received a 2-cm posterior tibial nerve graft and were randomized to one of three experimental groups. Group I animals were left untreated, group II received daily CsA (5 mg/kg intraperitoneally), and group III received daily FK506 (1 mg/kg intraperitoneally). Walking tracks were obtained starting 3 weeks after graft placement and continuing biweekly for the next 7 weeks. FK506-treated animals fully recovered hindlimb function 7 days earlier than CsA-treated animals or untreated control animals. Regenerated nerves from one-half of each treatment group were harvested for histomorphometric analysis at 7 weeks, shortly after recovery was complete in the FK506-treatment group but not in the other two groups, and once again at 10.5 weeks when recovery of function had stabilized in all groups. At 7 weeks, FK506-treated animals had significantly greater fiber density and percentage of neural tissue per nerve and a significantly larger population of mature, myelinated fibers in comparison with either CsA-treated or untreated animals. The authors concluded that the daily, systemic administration of low-dose FK506 facilitates peripheral nerve recovery and regeneration after nerve grafting.

Animals↗