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Biomedical subjects

G W Sypert

Publications and source records attributed to G W Sypert.

At least 19 recordsLinked to original sources
PubMed1991

Correlative electrophysiological and behavioral evaluation following L5 lesions in the cat: a model of spasticity.

The present work developed an animal model of hindlimb spasticity by analyzing the electrophysiological and behavioral consequences of L5 spinal cord lesions in cats. In chronically lesioned animals (1 to 6 months), the L7-S1 dorsal roots were stimulated and evoked potentials were recorded from hindlimb flexor and extensor motor nerves. Following lateral hemisection, the monosynaptic responses were 2-5 times larger (for voltage-time integral and for amplitude) on the ipsilateral side than those from the contralateral side or from control animals. Half-widths, rise-times, and latencies of the monosynaptic responses were the same on both sides. Behavioral signs of spasticity, including hypertonia and increased deep tendon reflexes, were displayed from the ipsilateral hindlimb following lateral hemisection. With lateral hemisection or with extensive dorsal quadrant lesions, hopping and proprioceptive placing reflexes were abolished; these behavioral observations impart functional significance to physiological and anatomical studies of a mid-lumbar center considered to be important for movement control. The present model represents the first demonstration of a statistically significant correlation between electrophysiological and behavioral observations of spasticity for animals with a lateral hemisection. These correlations demonstrate the utility of behavioral screening of animals for subsequent neurophysiological analyses. This facilitates the investigation of cellular events underlying spasticity and of strategies for its relief with tissue repair techniques affecting local circuitry involved in spasticity.

Animals↗
PubMed1991

Transoral approach to the upper cervical spine.

The transoral approach to pathology of the upper cervical spine is logical, but it is seldom used due to concerns about exposure and infection. The authors report on 16 consecutive patients requiring exposure from clivus through C3 for pathology, including spinal cord compression by rheumatoid pannus, craniovertebral anomalies, and tumor. Exposure was obtained using a Dingman mouth gag and soft palate retraction with silicone rubber sheeting. A horizontal "H" incision was made in the posterior pharyngeal wall creating three layers, closed separately, with attention to a watertight closure of the final mucosal layer. In no case was it necessary to divide the mandible, tongue, soft palate, or uvula. There were no deaths, wound breakdowns, infections, or persistent cerebrospinal fluid leakage. Patients with neurological indications improved postoperatively, and all tumors were grossly resected. Combined otolaryngology/neurosurgical exposure and treatment of pathology involving the upper cervical spine via the transoral approach is safe and effective. Functional results have been excellent, and no major complications were encountered.

Adolescent↗
PubMed1989

Independent evaluation of a multidisciplinary rehabilitation program for chronic low back pain.

Severe chronic low back pain was diagnosed in 236 patients by one physician and they were referred to the University of Miami Comprehensive Pain and Rehabilitation Center (UMCPRC) over a 5-year period for an intensive 4-week inpatient treatment program. Of these 143 (61%) were able to be contacted by telephone and given a structured interview designed for the study. The average time elapsed at follow-up from referral for all patients was 22.5 months. Outcome was measured in the following terms: current levels of pain, percent decrease in pain, subsequent health care utilization, activities of daily living, and attitudes toward treatment. After completion of the interview, the McGill Pain Questionnaire and the Oswestry Low Back Pain Disability Questionnaire were sent to the patients. The patients fell into five groupings: Group 1--participants in the UMCPRC program (n = 39); Group 2--those whose participation was not approved by insurance (n = 30); Group 3--those who declined participation (n = 46); Group 4--participants in other programs (n = 14); Group 5--dropouts (n = 14). The five groups were not meaningfully different with regard to prereferral demographics. Interestingly, Group 1 patients exhibited significantly greater prereferral pain and unemployment levels. Despite this, at follow-up significantly more Group 1 members were employed and they exhibited a greater percent decrease in pain as compared to the nonparticipant groups. Returned McGill and Oswestry Questionnaires mirrored these findings. Group 1 members also demonstrated significantly lower rates of subsequent health care utilization, i.e., physician visits, hospitalizations, and surgery than the nonparticipant groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Relation of whole muscle contractile properties to source of innervation.

This work investigated the extent to which constituent proportions of fast- and slow-twitch muscle units determine whole muscle contractile properties. We employed several self- and cross-reinnervation models using synergistic homogeneous and heterogeneous muscles. By comparing the present data with previously published single-unit studies on the same animals, we confirmed that the whole muscle data provide a weighted ensemble of single-unit effects. They corroborate conclusions based upon single-unit data concerning the proportions of fast- and slow-twitch units, the degree of recovery, and the alteration of force- and speed-related properties of muscle by nerve. In particular, the shape of the whole muscle isometric twitch was a reliable indicator of the relative proportions of fast- and slow-twitch motor units in the muscle. The half-rise time was an indicator of the presence or absence of fast units, and the half-relaxation time was an indicator of the presence of slow units.

Animals↗
PubMed1988

Intramedullary spinal tuberculoma.

A case report of intramedullary spinal tuberculomas presenting as cervical myelopathy is described. The rarity of these lesions in North America make this case unique. The use of modern neurodiagnostic and microsurgical techniques as well as the use of postoperative antituberculous drugs resulted in a good outcome. The first known description of magnetic resonance imaging of intramedullary spinal tuberculomas is presented. The gross and microscopic appearances of the lesion are given.

Aged↗
PubMed1988

Stabilization procedures for thoracic and lumbar fractures.

New concepts regarding the biomechanics of spinal instability, new technology for spinal and neurodiagnostic imaging, further evolution of the role of neurological decompression, and the development of improved systems and techniques for achieving anatomical reconstruction and fixation of the spine continue to improve the care of patients suffering injuries of the thoracic and lumbar spine. This field of medicine is in rapid evolution, and newer improved methods will be forthcoming in the near future. An understanding of all of these developments as well as their limitations and potential complications is requisite if we are to optimize the functional capability of patients suffering these catastrophic injuries.

Bone Wires↗
PubMed1987

Motor-unit properties following cross-reinnervation of cat lateral gastrocnemius and soleus muscles with medial gastrocnemius nerve. I. Influence of motoneurons on muscle.

This study addresses two questions: is reinnervation of mammalian skeletal muscle selective with respect to motor-unit type? And to what degree may muscle-unit contractile properties be determined by the motoneuron? Properties of individual motor units were examined following cross-reinnervation (X-reinnervation) of lateral gastrocnemius (LG) and soleus muscles by the medial gastrocnemius (MG) nerve in the cat. We examined animals at two postoperative times: 9-10 wk (medX) and 9-11 mo (longX). For comparison, properties of normal LG and soleus motor units were studied. Motor units were classified on the basis of their contractile response as fast contracting fatigable, fast intermediate, fast contracting fatigue resistant, or slow (types FF, FI, FR, or S, respectively) (13,29). Muscle fibers were classified on the basis of histochemical properties as fast glycolytic, fast oxidative glycolytic, or slow oxidative (types FG, FOG, or SO, respectively) (61). Reinnervation of LG and soleus was not selective with respect to motor-unit type. Both muscles were innervated by a full complement of MG motoneuron types, apparently in normal MG proportions. MG motoneurons determined LG muscle fibers' properties to a similar degree as reinnervated MG muscle fibers. In contrast, soleus muscle fibers "resisted" the influence of MG motoneurons. Thus, although longX-reinnervated LG muscle (longX LG) had a motor-unit type distribution similar to normal or self-reinnervated MG, longX soleus contained predominantly type S motor units. Overall mean values for muscle-unit contractile properties reflected this motor-unit type distribution. Muscle units in longX LG and longX soleus had contractile properties typical of the same motor-unit type in normal LG or soleus, respectively. Motor-unit types were recognizable at 10 wk X-reinnervation, although muscle-unit tensions were lower than after 10 mo. The proportions of fast and slow motor units in medX LG were similar to longX LG, although a greater proportion of fast units were resistant to fatigue at 10 wk. There were fewer fast units in medX soleus than longX soleus, which suggested that motor-unit type conversion or innervation of muscle fibers by fast motoneurons is not complete at 10 wk. We conclude that reinnervation of the LG and soleus muscles by MG motoneurons was not selective with respect to motor-unit type. MG motoneurons determined LG muscle properties to a similar degree as self-reinnervated MG muscle fibers. Soleus muscle fibers resisted the influence of MG motoneurons, representing a limit to neural determination of muscle properties.

Animals↗
PubMed1987

Motor-unit properties following cross-reinnervation of cat lateral gastrocnemius and soleus muscles with medial gastrocnemius nerve. II. Influence of muscle on motoneurons.

We tested whether the muscle innervated may influence the expression of motoneuron electrical properties. Properties of individual motor units were examined following cross-reinnervation (X-reinnervation) of cat lateral gastrocnemius (LG) and soleus muscles by the medial gastrocnemius (MG) nerve. We examined animals at two postoperative times: 9-10 wk (medX) and 9-11 mo (longX). For comparison, normal LG and soleus motoneuron properties were also studied. Motor units were classified on the basis of their contractile responses as fast contracting fatigable, fast intermediate fast contracting fatigue resistant, and slow types FF, FI, FR, or S, respectively) (9, 21). Motoneuron electrical properties (rheobase, input resistance, axonal conduction velocity, afterhyperpolarization) were measured. After 9-11 mo, MG motoneurons that innervated LG muscle showed recovery of electrical properties similar to self-regenerated MG motoneurons. The relationships between motoneuron electrical properties were largely similar to self-regenerated MG. For MG motoneurons that innervated LG, motoneuron type (65) predicted motor-unit type in 74% of cases. LongX-soleus motoneurons differed from longX-LG motoneurons or self-regenerated MG motoneurons in mean values for motoneuron electrical properties. The differences in overall means reflected the predominance of type S motor units. The relationships between motoneuron electrical properties were also different than in self-regenerated MG motoneurons. In all cases, the alterations were in the direction of properties of type S units, and the relationship between normal soleus motoneurons and their muscle units. Within motor-unit types, the mean values were typical for that type in self-regenerated MG. Motoneuron type (65) was a fairly strong predictor of motor-unit type in longX soleus. MG motoneurons that innervated soleus displayed altered values for axonal conduction velocity, rheobase, and input resistance, which could indicate incomplete recovery from the axotomized state. However, although mean afterhyperpolarization (AHP) half-decay time was unaltered by axotomy (25), this parameter was significantly lengthened in MG motoneurons that innervated soleus muscle. There were, however, individual motoneuron-muscle-unit mismatches, which suggested that longer mean AHP half-decay time may also be due to incomplete recovery of a subpopulation of motoneurons. Those MG motoneurons able to specify soleus muscle-fiber type exhibited motoneuron electrical properties typical of that same motoneuron type in self-regenerated MG.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1987

External spinal orthotics.

A great variety of spinal orthoses are available to neurological surgeons involved in the evaluation and management of spinal disorders. Each of the orthoses has certain advantages and disadvantages, and enough information about the biomechanical principles of spinal instability and spinal orthoses exists to make possible rational application of the appropriate orthosis. Based on this information, recommendations have been formulated for selecting the proper orthosis for the control of each spinal region, depending on the results sought through the use of an external orthosis.

Humans↗
PubMed1987

Evoked potential monitoring during aneurysm operation: observations after fifty cases.

Somatosensory or brain stem auditory evoked potentials (EPs) were monitored during 50 aneurysm procedures. Base line EPs were obtained shortly after the induction of general anesthesia and were recorded continuously during operation. Absolute latency, interpeak latency, and cortical EP amplitude were subsequently determined. Statistical analysis confirmed that significant changes in these parameters are routine during aneurysm operation. Arbitrary definitions of abnormal latency and amplitude changes led to an excessive false-positive/false-negative rate. From the time of dural opening to the time of closure, prolongation of central conduction time, decrease in cortical amplitude, or disappearance of the EP was predictive of postoperative sensory or motor deficit in all patients monitored, except those undergoing operation on basilar artery aneurysms. In basilar aneurysm cases, outcome could not be reliably predicted with either EP technique.

Adult↗
PubMed1987

Thoracic spinal canal stenosis.

Hypertrophy of the posterior spinal elements leading to compromise of the spinal canal and its neural elements is a well-recognized pathological entity affecting the lumbar or cervical spine. Such stenosis of the thoracic spine in the absence of a generalized rheumatological, metabolic, or orthopedic disorder, or a history of trauma is generally considered to be rare. Over a 2-year period the authors have treated six cases of thoracic myelopathy associated with thoracic canal stenosis. In four patients the deficits developed gradually and painlessly. The three older patients had a clinical profile characterized by complaints of pseudoclaudication, spastic lower limbs, and evidence of posterior column dysfunction. Two patients were younger adults with low thoracic myelopathy associated with local back pain after minor trauma. Both patients also had congenital narrowing of the thoracic spinal canal. Oil and metrizamide contrast myelography in the prone position were of limited value in diagnosing this condition; in fact, myelography may be misleading and result in erroneous diagnosis of thoracic disc protrusion, when the principal problem is dorsal and lateral compression from hypertrophied facets. Magnetic resonance imaging and computerized tomography sector scanning were more useful in the diagnosis of this disorder than was myelography. Thoracic canal stenosis may be more common than is currently recognized and account for a portion of the failures in anterior and lateral decompression of thoracic disc herniations.

Adult↗
PubMed1987

Cervical spine stenosis secondary to ossification of the posterior longitudinal ligament.

Ossification of the posterior longitudinal ligament (OPLL) is a well-documented cause of cervical spine stenosis and myelopathy among Japanese patients. Reports of OPLL in North Americans are rare. Choices of diagnostic method and treatment for this entity remain controversial. The authors report the results of management of 20 patients in the United States with symptomatic OPLL of the cervical spine. These represented 10% to 20% of patients operated on over the last 3 years for myelopathy secondary to structural spinal compression. Most of these OPLL patients were Caucasian (60%), male (male:female 4:1), and middle-aged (median age 47.5 years). Six had previously undergone laminectomy or discectomy. Cervical roentgenograms and standard myelography occasionally suggested the diagnosis. Axial computerized tomography (CT) metrizamide myelography with small interslice intervals proved invaluable for diagnosis and operative planning. Magnetic resonance imaging was not necessary for diagnosis. Retrovertebral calcification extended over one to five bodies (mean 2.75). The mass ranged in size from 5 to 16 mm in anteroposterior diameter and reduced the residual canal diameter to a mean (+/- standard deviation) caliber of 9.42 +/- 2.41 mm (mean narrowing ratio 0.44 +/- 0.12). Anterior cervical decompression by medial corpectomy and discectomy with fusion uniformly reduced preoperative myelopathy. Complications were limited to transient neurological deterioration in two patients, recurrent laryngeal nerve palsy in one, and halo device pin site infections in two. At a mean postoperative interval of 15 months, improvement was seen in each category of deficit: extremity weakness, hypesthesia, hypertonia, and urinary dysfunction. All fusions produced solid unions. It is concluded that OPLL of the cervical spine is an unexpectedly prevalent cause of myelopathy among patients treated in the United States. Thin-section axial CT metrizamide myelography with small interslice intervals is essential for the investigation of patients who may have OPLL. Anterior decompression and stabilization by medial corpectomy, discectomy, removal of the calcified mass, and fusion is a safe and effective method of treatment.

Adult↗
PubMed1986

Regeneration in peripheral nerve grafts to the cat spinal cord.

Peripheral nervous system grafts have long been known to promote CNS axonal elongation in the rodent. To investigate whether these principles also apply to a higher order animal, more suitable for physiologic studies, we performed autogenous sciatic nerve grafts to the adult cat spinal cord. This report is a brief, initial study of these grafts. In an effort to study both descending and ascending fibers as separately as possible, laminectomies were performed at both thoracic (T2-T9) and lumbar (L2-L4) levels. Aspiration lesions were made in the left side of the cord and the sciatic grafts were introduced. Three cats were studied with standard histological techniques, confirming previous reports of glial scar formation, collagen deposition, and cyst formation at the graft-CNS junction. In 7 other animals, at 146-179 days after the initial operation, the axonal origins were traced retrogradely using horseradish peroxidase and the tetramethyl benzidine technique. Reinnervation of the graft was found by intrinsic spinal cord neurons and dorsal root ganglia neurons. The number of reinnervating neurons was found to be greater than previously reported in the rodent. There was, however, no evidence of regeneration from brainstem nuclei when the grafts were placed at spinal levels where this has been seen in the rat. This may support an absolute maximum for regenerative distances vs a relative one. Although the amount of data was limited, it did support previous reports that peripheral axotomy enhances the regenerative response seen in primary sensory neurons.

Animals↗
PubMed1986

Anomolous path taken by branch of medial gastrocnemius nerve.

An anomolous branch of the cat medial gastrocnemius nerve was found to travel with the combined lateral gastrocnemius and soleus nerves in the popliteal fossa before innervating muscle fibers in the medial gastrocnemius. The innervation pattern was confirmed by EMG recording, elicitation of contraction in the medial gastrocnemius by stimulating the branch, isolation of a single motor unit innervating the medial gastrocnemius whose axon traveled in the branch, and glycogen depletion of medial gastrocnemius muscle fibers by stimulating the branch. Awareness of such anatomic variation is important, for example, in interpreting studies of synaptic connections and of mechanical properties during reinnervation of muscle.

Animals↗
PubMed1986

Plasticity of medial gastrocnemius motor units following cordotomy in the cat.

Experiments were performed in adult cats to determine the effects of lumbar cordotomy on synaptic potentials, motoneuron membrane electrical properties, muscle-unit contractile properties, and whole-muscle histochemical properties of a heterogeneous skeletal muscle. Medial gastrocnemius (MG) motor units were examined 1 wk to 7 mo following complete transection of the lumbar spinal cord (cordotomy). Motor units were classified on the basis of their contractile properties as type FF, FI, FR, or S (8, 68). Muscle fibers were classified as type FG, FOG, or SO on the basis of histochemical staining (59). Motoneuron electrical properties (axonal conduction velocity, action-potential amplitude, rheobase, input resistance, afterhyperpolarization), group I EPSPs, and muscle-unit contractile properties (unpotentiated and potentiated twitch, unfused and fused tetanus, fatigability) were measured. Reduced numbers of type FR motor units and increased numbers of types FI + FF motor units were found in electrophysiological experiments 2 wk to 7 mo following cordotomy. Corroborative data were obtained from histochemical studies of the same MG muscles. Electrical properties of the motoneurons of each motor-unit type were normal following cordotomy. The close correspondence between motoneuron electrical properties and muscle-unit contractile properties found in normal MG muscle (68) was preserved following cordotomy. Contractile strength of muscle units of all types was severely reduced following cordotomy; partial recovery occurred 4-7 mo following cordotomy. Cross-sectional area of muscle fibers was reduced at all times investigated (2 wk to 7 mo). In three cats, homonymous group Ia single-fiber-motoneuron EPSPs were studied 1 or 2 mo following cordotomy at spinal level L4-5 or L5. EPSP amplitude and afferent-to-motoneuron projection frequency were normal. In 12 other cats, composite heteronymous group I EPSPs were studied 2 wk to 7 mo following cordotomy at various levels. Amplitude of these EPSPs was increased, dependent upon level of cordotomy and postoperative time. Hypotheses concerning the influence of motoneurons on muscle, and of muscle on motoneurons, are presented as possible mechanisms whereby the close relation between motoneuron electrical and muscle-unit contractile properties is preserved in the face of redistributed motor-unit populations.

Afferent Pathways↗