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Biomedical subjects

P H Gorman

Publications and source records attributed to P H Gorman.

6 recordsLinked to original sources
PubMed1998

Neurophysiologic evaluation of lower motor neuron damage in tetraplegia.

We quantitatively investigated the extent of damage to motor neurons in tetraplegic subjects. Numbers of motor units in the patients were significantly lower for thenar, wrist extensor, and biceps brachii as compared to controls. Reduction in counts occurred even when M-response amplitudes were normal. Standard electromyography suggested a surprising frequency of lower motor neuron dysfunction below the level of injury. These results confirm previous reports and add data on motor units in the biceps brachii.

Cell Count↗
PubMed1997

Patient selection for an upper extremity neuroprosthesis in tetraplegic individuals.

One hundred and twenty persons with new onset traumatic tetraplegia consecutively admitted to our rehabilitation service were screened for consideration for use of an upper extremity neuroprosthesis. Strict inclusion criteria allowed only for participation of patients with ASIA impairment scale A, B or C injuries at the C5 or C6 level. One hundred and six persons were excluded from participation for the following reasons: five patients died, 27 had central cord syndrome, two had Brown-Sequard syndrome, 12 were injured at too high a level, 42 were injured at too low a level, two were excluded on the basis of motor incompleteness alone, four were excessively denervated, two had limited range of motion, one had overriding medical complications, seven had psychosocial issues making participation impractical, and two elected tendon transfer surgery. In total, 14 patients (representing 11.7% of all tetraplegic individuals and 50% of the C5 or C6 ASIA Impairment Scale A, B or C patients) were found to be candidates for the neuroprosthesis. Given the prevalence of tetraplegia, approximately 12,200 Americans would be candidates for the FES neuroprosthetic hand grasp system under the current research protocols. With both the expansion of current protocols to other diagnostic categories and further research and development, application of this neuroprosthesis to a considerable number of previously excluded subjects will likely be possible.

Adult↗
PubMed1993

Nonlinear stretch reflex interaction during cocontraction.

1. We investigated the role of stretch reflexes in controlling two antagonist muscles acting at the interphalangeal joint in the normal human thumb. Reflex action was compared when either muscle contracted alone and during cocontraction. 2. The total torque of the flexor pollicis longus (FPL) and extensor pollicis longus (EPL) muscles was measured in response to an externally imposed extension of the interphalangeal joint. The initial joint angle and the amplitude of the extension were constant in all experiments, and the preload of the active muscle(s) was varied. Joint torque was measured at the peak of short-latency stretch reflex action during contraction of the FPL alone, contraction of the EPL alone, and during cocontraction. Incremental joint stiffness was calculated as the change in torque divided by the change in angle. 3. Incremental stiffness increased in proportion to the preload torque during single muscle contractions of either the FPL (lengthening disturbances) or the EPL (shortening disturbances). Thus stiffness was not regulated to a constant value in the face of varying loads for either single muscle stretch or release. 4. Incremental stiffness varied across the range of cocontraction levels while the net torque was maintained at approximately 0. Thus net torque alone did not determine the stiffness during cocontraction. 5. The contributions of each muscle to the net intrinsic torque during cocontraction were estimated by scaling the individual muscles' responses so that their sum gave the best fit (in a least-squares sense) to the cocontraction torque before reflex action. The solution is unique because the individual torques have opposite signs, but the stiffnesses add. This gave estimates of the initial torques of both muscles during cocontraction. 6. The contributions of the two muscles during cocontraction were used to estimate the active joint stiffness that would be expected if the two muscles were activated independently to the same levels as in the cocontraction trials. The stiffness measured at the peak of stretch reflex action during cocontraction trials differed from the sum of the stiffnesses of the two muscles when they were contracting alone. At low cocontraction levels, the measured stiffness was less than expected on the basis of summation of the action of the two muscles, whereas at high cocontraction levels, the measured stiffness was greater than expected. This demonstrates that there is nonlinear stretch reflex interaction. That is, reflex action for a pair of antagonists is not simply the linear sum of the reflex actions of the two muscles acting independently.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1992

Upper extremity applications of functional neuromuscular stimulation.

Functional electrical stimulation (FES) has been used for increasing muscle strength, decreasing spasticity, and controlling movement of limbs for many years. Most of this work, however, has been done in a research setting. Over the past decade, FES has moved slowly from the laboratory to the clinical world through feasibility studies in groups of patients with spinal cord injuries and strokes. Electrical stimulation has been shown to decrease spastic tone both during and after the stimulation, allowing for better limb positioning, decrease in contracture formation, and in some cases, improvement of voluntary movement. Electrical stimulation as a motor prosthesis is now being provided to small groups of spinal cord-injured patients (primarily C4, C5 and C6 levels) to assist with hand positioning and to produce hand grasp. In these settings, patients have attained greater independence in activities of daily living and in work-related tasks. Distribution of this technology to multiple centers is continuing through a technology transfer program.

Arm↗
PubMed1989

Intramedullary and extramedullary schwannoma of the cervical spinal cord--case report.

Intramedullary schwannomas and neurofibromas are rare tumors. Only two cases have been reported as having both an intramedullary and extramedullary component. We have managed the case of a 15-year-old girl with a schwannoma that appeared to track along the sensory nerve root into the spinal cord. The clinical presentation in this case was that of motor weakness and atrophy, sensory abnormalities, and, late in the course, pain. Magnetic resonance imaging with gadolinium enhancement was better than myelography and computed tomography at delineating the intramedullary extent of the tumor. The tumor was removed microsurgically at two operative sittings. Reports of this unusual pathology are reviewed.

Adolescent↗