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PubMed1985

Specificity of early motoneuron growth cone outgrowth in the chick embryo.

During development, chick lumbosacral motoneurons have been reported to form precise topographic projections within the limb from the time of initial outgrowth. This observation implies, first, that motoneurons select the appropriate muscle nerve pathway and, second, that they restrict their ramification within the primary uncleaved muscle masses to appropriate regions. Several reports based on electrophysiology and orthograde horseradish peroxidase (HRP) labeling have shown muscle nerve pathway selection to be fairly precise. However, studies based on retrograde labeling with HRP have produced conflicting reports on the extent to which vertebrate motoneurons make projection errors. Since it is difficult to distinguish between true projection errors and HRP leakage when using retrograde labeling, we decided to assess the distribution of labeled growth cones in 25-micron serial plastic sections, following orthograde labeling of identifiable subpopulations of motoneurons during the period of initial axon outgrowth. Examination of a large number of muscle nerves revealed no segmentally inappropriate axons, confirming earlier reports that muscle nerve pathway selection is very accurate. In addition, we observed that growth cones take widely divergent trajectories into the same muscle nerve, suggesting that growth cones are responding independently to some specific environmental cue rather than being passively channeled at this point. The distribution of labeled growth cones within the muscle masses provided direct evidence that motoneurons did not at any time project to obviously inappropriate muscle regions.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1977

Intraspinal sacral root stimulation for controlled micturition.

The intraspinal extradural segments of the sacral nerves were stimulated in an effort to obtain the combination of maximal detrusor contraction and minimal outflow resistance essential for effective micturition. Each root was stimulated unilaterally and bilaterally. In addition, each was separated into its motor and sensory components and these components were then individually stimulated. It was found that the most effective result was obtained with stimulation of root S2. As in the experimental animal, sacral roots in the human have a long intraspinal course that makes them accessible for implantation of electrodes. It is hoped that ongoing experiments will lead to the development of a chronically implantable sacral root electrode--thus providing a tool for efficient emptying of the denervated bladder.

Animals↗
PubMed1979

Micturition and the male genitourinary response to sacral root stimulation.

The sacral roots, because of their anatomic and functional organization, are well suited to chronic stimulation. Data from our previous experiments on female dogs suggested that effective voiding responses to stimulation could be obtained by using the ventral root of S2, the sacral nerve in canines with the greatest detrusor representation. Elimination of dorsal root afferents from the stimulus field was essential to the minimization of spinal reflex activity. A selective somatic neurotomy was also necessary to attenuate maximally sphincter activity. In the male, the presence of the prostate gland, the greater urethral length, and the erectile response to stimulation might result in compression of the urethra, compromising micturition. Sacral root stimulation was thus studied using both spinalized and nonspinalized male dogs; the results are discussed with a view toward the applicability of sacral root stimulation to effect micturition in male paraplegics, who comprise the largest percentage of this group of patients.

Animals↗
PubMedDate not supplied

A reappraisal of the anatomy of the levator ani muscle in man.

A study of the attachments of the musculotendinous fibres of the levator ani muscle shows that it is made of two portions: a thick anterior portion which is mostly fleshy and a thin posterior portion which is mostly aponeurotic. The anterior portion consists of two layers: a superficial perineal layer and a deep pelvic layer. Both layers have a common origin from the back of the body of the pubic bone and the anterior part of the tendinous arch. In addition both layers make a U-shaped loop around the recto-anal junction. The posterior fibres of the deep pelvic layer received nerve supply only from the third and fourth sacral nerves. The rest of the muscle was supplied from the sacral nerves as well as the perineal branches of the pudendal nerve. The role of the anterior fibres in reinforcing the sphincters of the anal canal and fixation of the pelvic viscera is stressed. The close anatomical relation between the posterior portion of the muscle and the obturator internus suggests that the latter may play a role in supporting the weak posterior portion of the levator ani, especially during straining positions associated with lateral rotation at both hips.

Adult↗
PubMed1988

Electromyographic abnormalities in neurologic injury associated with pelvic fracture: case reports and literature review.

The incidence of neurologic injury associated with pelvic fractures is estimated at 10%. Studies have demonstrated that patients with double vertical pelvic fractures (combined injury to the anterior third of the pelvic ring and the sacroiliac area) are most at risk, with a 46% incidence of neurologic injury. Patients with pelvic fractures usually have many other associated injuries and medical complications, making the patients' neurologic deficits difficult to assess and thus easy to overlook in the acute setting. Three such patients are described. Electromyography was useful in confirming their diagnoses, thus allowing appropriate management.

Adult↗