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Biomedical subjects

S E Mackinnon

Publications and source records attributed to S E Mackinnon.

At least 127 records · Page 7Linked to original sources
PubMed1994

Provocative testing for cubital tunnel syndrome.

This prospective study evaluated the clinical usefulness of provocative testing in 32 subjects with electrodiagnostically proven cubital tunnel syndrome and 33 control subjects. Four provocative tests were included: Tinel's sign, elbow flexion, pressure provocation, and combined elbow flexion and pressure provocation. The mean age of the control group was 41 years and 46 years for the group with cubital tunnel syndrome. In the control group, provocative tests were rarely positive. In 44 extremities with cubital tunnel syndrome, 31 had a Tinel's sign, 33 had a positive elbow flexion test, 39 had symptoms with pressure only, and 41 had symptoms with a combination of pressure provocation and elbow flexion testing. The sensitivity of the Tinel sign was 0.70, and at 30 seconds, the sensitivities of the other provocative tests were: elbow flexion (0.32), pressure provocation (0.55), and pressure-flexion test (0.91). The most sensitive provocative test in the diagnosis of cubital tunnel syndrome was elbow flexion when combined with pressure on the ulnar nerve.

Adult↗
PubMed1994

Peripheral nerve revascularization: a current literature review.

The revascularization of peripheral nerve grafts is reviewed in detail. The endoneurial vasculature is examined and noted to be anatomically dissimilar to a conventional capillary bed although, physiologically, it must subserve similar metabolic functions. Autografts, allografts, and xenografts are considered, as is the effect of graft caliber. The clinical implications for vascularized nerve grafting are discussed.

Animals↗
PubMed1994

Subjective and employment outcome following secondary carpal tunnel surgery.

Forty-five patients (50 hands) who had undergone secondary carpal tunnel surgery participated in a telephone questionnaire survey. The mean follow-up time from the second carpal tunnel surgery was 31 months (range, 9-92 mo). Only 24 patients (53%) reported significant improvement in their symptoms. Thirty-nine patients were unemployed workers who had experienced an average time off work of 28.7 months (+/- 4) before their secondary carpal tunnel surgery. Eleven of the 39 previously unemployed workers (28%) returned to work after the secondary carpal tunnel surgery. Factors associated with poor subjective and employment outcome included worker's compensation case involvement (p < 0.003). Occupations associated with repetitive hand movements or vibrating tools were associated with poor employment outcomes (p < 0.006). Although secondary surgery for carpal tunnel syndrome can be effective in relieving symptoms, patients and surgeons must have realistic expectations of the procedure, especially with respect to long-term employment goals.

Adult↗
PubMed1994

The fate of Schwann cells in peripheral nerve allografts.

The phenotype of Schwann cells, whether of host or donor origin, in nerve allografts has been a source of debate. The origin of Schwann cells in peripheral nerve allografts under conditions of no, temporary or continuous immunosuppression was assessed by immunohistochemistry. We hypothesized that host-derived Schwann cells would replace rejected foreign donor Schwann cells after withdrawal of immunosuppression. A murine model of nerve transplantation to normal (wild-type) hosts from donor Shiverer mice, a mutant whose Schwann cells are deficient in myelin basic protein, was used and antibody reactivity against myelin basic protein was employed to ascertain the identity of Schwann cells in the nerve allograft. Without immunosuppression, donor Shiverer Schwann cells were rejected and the nerve graft morphology was restored by host-derived Schwann cells. With continuous immunosuppression, donor Shiverer Schwann cells persisted in the graft segment, associated with a chronic rejection phenomenon. The latter allowed migration of host-derived Schwann cells, over time, into the graft segment in approximately half the cases. After withdrawal of finite (6 weeks) immunosuppression, a rejection response eliminated donor Schwann cells. Replacement by host Schwann cells ensured as was hypothesized.

Animals↗
PubMed1994

Tongue reinnervation by hypoglossal-lingual nerve transfer.

The morbidity associated with total glossectomy for treatment of base of tongue carcinomas provides the impetus to investigate techniques to salvage the uninvolved normal anterior tongue. This report describes a method of reinnervation of the anterior tongue using a hypoglossal-lingual transfer. In Cynomolgus monkeys, unilateral transfers with and without a subsequent muscle fillet resulted in reinnervation from the base to the tip of the tongue. It is proposed that hypoglossal-lingual nerve transfers be considered to allow sparing and return of function to the anterior tongue in conjunction with a resection of the tongue base. Additional experiments confirmed that the base of the tongue, like other midline muscles, has bilateral and separate innervation. The presence of a physiological lingual-hypoglossal reflex in the normal animal was documented.

Animals↗
PubMed1993

Regeneration across 'stepping-stone' nerve grafts.

The ability of small nerve segments interposed between synthetic conduits to increase the total nerve gap distance across which successful nerve regeneration would occur was studied. Fifty adult male Lewis rats were randomized into five groups. In Group I a segment of resected sciatic nerve was repaired by a nerve graft. Group II had alternating silicone tubing/nerve graft/silicone tubing replacement of the resected nerve segment (single stepping stone group). Group III had silicone tubing/nerve graft/silicone tubing/nerve graft/silicone tubing repair of the nerve deficit (double stepping stone). Group IV had a single long silicone conduit repair. Group V control underwent a sham operation. Nerve regeneration was evaluated using walking track pattern analysis, electrophysiologic assessment and histomorphological evaluation. 'Stepping stone nerve grafts' enhanced regeneration across nerve gaps in comparison to a single long conduit, but were inferior to a single long nerve graft. In the repair of long nerve gaps, the use of multiple short conduits with interposed short nerve segments could provide a source of trophic factors to enhance regeneration.

Animals↗
PubMed1993

The anatomical course of the palmar cutaneous branch of the median nerve, including a description of its own unique tunnel.

In order to obtain a better understanding of the palmar cutaneous branch of the median nerve, dissections of 21 forearms from 12 fresh cadavers were done with loupe magnification. Discrete regions of potential surgical significance were identified, including an origin that can be as high as 11 cm proximal to the wrist crease, a radial position immediately after its origin so that it lies adjacent to flexor carpi radialis in the distal forearm, and the existence of an anatomical tunnel through the palmar aponeurosis.

Cadaver↗
PubMed1993

A technique for maximizing biceps recovery in brachial plexus reconstruction.

In 21 cadaver dissections the intramuscular anatomy of the musculocutaneous nerve and the relative relationship of the motor and sensory components of this nerve were evaluated. Nearly one half of the fibers entering the musculocutaneous nerve terminate in cutaneous receptors. We report five cases in which biceps reinnervation was performed by a surgical technique that minimizes the period of denervation by using motor nerves (medial pectoral nerves) very close to the biceps muscle. This technique also redirects the cutaneous portion (lateral antebrachial cutaneous nerve) of the musculocutaneous nerve into the biceps muscle to ensure that the motor fibers are not directed toward cutaneous receptors.

Adult↗
PubMed1993

An evaluation of rapid exchange and simultaneous grip tests.

The usefulness of the rapid exchange grip test and a modification of this test, the rapid simultaneous grip test, in detecting submaximal grip efforts was evaluated. Uninjured subjects giving maximal or submaximal grip efforts were tested at grip rates of 80 and 100 repetitions per minute. Rapid exchange grip at 80 repetitions per minute yielded a sensitivity of 86% and a specificity of 97%. Rapid simultaneous grip at 80 repetitions per minute yielded a sensitivity of 81% and a specificity of 93%. Poorer sensitivities and specificities resulted when a clinical population of patients was tested. Patients who were not giving maximal efforts tended not to comply with the test protocol. The rapid exchange and rapid simultaneous grip tests do assist in detecting submaximal grip efforts; limits to these tests are emphasized.

Adolescent↗
PubMed1993

Evaluation of patients with thoracic outlet syndrome.

This prospective study evaluated 50 patients with thoracic outlet syndrome. Detailed history and pain scale evaluation preceded physical examination, which included provocative tests (positional and compressive) and sensory evaluation (baseline and postprovocative vibration thresholds and two-point discrimination). Only one patient had a positive nerve conduction study/electromyograph at the brachial plexus level. Thirty-two percent of the patients had a compressive anatomic abnormality as seen on a computed tomography scan. Ninety-four percent had positive provocative position and compression test results. Two-point discrimination was normal in 98%. Clinical assessment of thoracic outlet syndrome is best achieved by reproduction of symptoms with compression and positional provocative testing. Results of the majority of tests (nerve conduction studies/electromyographs, x-ray films, sensory tests) will be normal. Measurements of changes in sensory thresholds during provocation of symptoms may be useful.

Adult↗
PubMed1993

Occupational exposure to hand vibration in northern Ontario gold miners.

Nineteen underground gold mine drillers who operate vibration equipment and a control group of 16 gold mill workers without vibration exposure were evaluated. Assessment included static two-point discrimination, moving two-point discrimination, vibration threshold, and cutaneous pressure threshold. Provocative tests, including Tinel, pressure, and Phalen signs, were performed at the carpal and cubital tunnels. Mean age of the miners was 35 years, and the mean age of the control group was 31 years. The mean time of vibration exposure was 14 years. Numbness, pain, and weakness was reported in 12 miners and 1 control subject. Symptoms of vibration white finger were found in 16 miners and 3 control subjects. The miners had a higher incidence of positive provocative tests at the carpal and cubital tunnels and higher cutaneous pressure thresholds than the control group. Significantly higher vibration thresholds were found in the miners versus the control subjects. A correlation between years of vibration exposure and vibration threshold was found.

Adult↗
PubMed1993

Direct muscle neurotization recovers gastrocnemius muscle function.

This case report describes a devastating injury in which a distal motor nerve had been avulsed from the muscle belly and was not available for reconstruction. This otherwise irreparable posterior tibial nerve injury was successfully treated by direct neurotization of the muscle belly. The patient did have one small, intact, muscular branch to the medial gastrocnemius muscle; however, electrodiagnostic and clinical examination and recovery pattern suggested the neurotization procedure was responsible for the functional recovery. In the rare situation where no distal nerve is available, and tendon transfers or arthrodesis are inappropriate, direct muscle neurotization can be considered as a salvage technique.

Adult↗
PubMed1993

A technique for nerve reconstruction following resection of soft-tissue sarcoma.

Primary nerve grafting should be considered whenever tumor extirpation necessitates resection of an adjacent critical nerve. A technique of nerve grafting is presented which distinguishes motor from sensory fascicles, using intraoperative electrical stimulation. Stimulation of individual motor fascicles is performed proximal and distal to the lesion, and fascicles which produce the same muscle contraction are identified. Motor and silent sensory fascicles are tagged prior to tumor resection. This facilitates subsequent specific motor/sensory reconstruction of the defect, using intrafascicular grafting techniques.

Adolescent↗
PubMed1993

The effect of a distal site of compression on neural regeneration.

The effect of a distal site of nerve compression on neural regeneration after a nerve repair was investigated in the rat model. After chronic compression had been established by placement of a Silastic band about a distal site of the posterior tibial nerve, the proximal posterior tibial nerve was divided, and then immediately repaired. Beginning 6 months after nerve repair, neural regeneration, assayed by walking track analysis, demonstrated significantly impaired function in the group of rats with a distal site of compression, compared with the repair group without a distal site of compression (p < .05). Followed for 3 additional months, neural function further significantly (p < .001) deteriorated in the group with distal compression. Morphometric analysis demonstrated that both the nerve repair alone and repair-plus-compression groups had 1) significantly decreased axon and nerve-fiber diameters (p < .001), and 2) significantly increased myelinated nerve-fiber density (p < .001), compared with normal; these findings are consistent with neural regeneration. However, the repair-plus-compression group had significantly (p < .03) fewer regenerating fibers than did the repair-without-distal-compression group. This experimental study suggests that consideration be given to release of sites of known anatomic narrowing in close proximity to a nerve reconstruction.

Animals↗