Lower Intercostal Nerves Research Articles

Peritoneal innervation: embryology and functional anatomy.

The parietal peritoneum (PP) is innervated by somatic and visceral afferent nerves. PP receives sensitive branches from the lower intercostal nerves and from the upper lumbar nerves. Microscopically, a dense network of unmyelinated and myelinated nerve fibers can be found all over the PP. The unmyelinated fibers are thin and are ending just underneath the PP. The myelinated fibers can penetrate the PP to reach the peritoneal cavity, where they lose their myelin sheath and are exposed to somatic and nociceptive stimuli. PP is sensitive to pain, pressure, touch, friction, cutting and temperature. Noxious stimuli are perceived as a localized, sharp pain. The visceral peritoneum (VP) itself is not innervated, but the sub-mesothelial tissue is innervated by the autonomous nerve system. In contrast to the PP, the visceral submesothelium also receives fibers from the vagal nerve, in addition to the spinal nerves. VP responds primarily to traction and pressure; not to cutting, burning or electrostimulation. Painful stimuli of the VP are poorly localized and dull. Pain in a foregut structure (stomach, duodenum or biliary tract) is referred to the epigastric region, pain in a midgut structure (appendix, jejunum, or ileum) to the periumbilical area and pain from a hindgut source (distal colon or rectum) is referred to the lower abdomen or suprapubic region. Peritoneal adhesions can contain nerve endings. Neurotransmitters are acetylcholine, VIP, serotonin, NO, encephalins, CGRP and substance P. Chronic peritoneal pain can be exacerbated by neurogenic inflammation, e.g. by endometriosis.

Multiple Lumbar Roots Neurotizations With the Lower Intercostal Nerves. Preliminary Clinical and Electrophysiological Results in a Sheep Model

Neurotization of lumbar roots with lower intercostal nerves is a potential way to treat neurological deficits after spinal cord injury. The anatomical feasibility of such neurotizations in humans has already been reported. We propose to assess axonal regrowth after intercostal to lumbar neurotization in a sheep model. Ten sheep had a left T11-L2, T12-L3, and T13-L4 neurotization. In 5 sheep, a L1 level left hemisection of the spinal cord was performed. The sheep had clinical and electrophysiological monitoring with a 6 mon follow-up. A flaccid paralysis with clinical asymmetry of the left abdominal wall was noted three months after surgery. This asymmetry improved in all the cases at the 6 mon follow-up. Motor potentials were detected without difficulty for the 3 neurotized nerves (L2, L3, and L4) in 5 sheep. In another sheep, motor potentials of the L3 root remained undetected. Eight sheep had postoperative complications responsible for the animals' death in 5 cases. The current study demonstrates the technical feasibility of intercosto-lumbar neurotizations in a sheep model. We proved in all the animals--except in the case of 1 neurotized root--the ability of motor axon to regenerate through neurotization area down to the muscular effectors; however, we noted a high rate of postoperative complications in this animal model.

The Paraspinal Splitting Approach: A Possible Approach to Perform Multiple Intercosto-Lumbar Neurotizations

Descriptive anatomy. OBJECTIVE.: To describe the anatomy associated with the extensive transmuscular paraspinal approach required to perform multiple intercosto-lumbar neurotizations. Neurotization of lumbar roots using lower intercostal nerves is a potential method of treating neurologic deficits after spinal cord injury. It appeared to us that the paraspinal splitting approach was potentially an optimal method to perform intercostal nerve harvesting, rerouting, and intercosto-lumbar neurotizations. Ninth, 10th, and 11th intercostal nerve harvesting and rerouting down to L2, L3, and L4 roots were performed on 50 cadavers. The descriptive anatomy and topographic landmarks are reported. The mean total length of intercostal nerve harvested was 17.96 (range, 10-27) cm for the 9th intercostal nerve, 17.14 cm (range, 10-20) for the 10th intercostal nerve and 15.94 cm (range, 10-25) for the 11th intercostal nerve. The length of harvested nerve was not correlated to the size of the trunk. The length of harvested nerve was sufficient to perform lumbar roots neurotizations in the 300 cases of nerve harvesting. Multiple lumbar roots neurotizations with lower intercostal nerves already have been proposed by other authors. In this strategy, the use of the spinal cord and intercostal nerves above the spinal cord lesion avoids the axonal regrowth required via the injured central nervous system. Rerouting intercostals nerves down to the lumbar roots at their exit from the intervertebral foraminae is less invasive that the same procedure performed down to the vertebral canal at the level of the cauda equina as we used in previous protocols. Our anatomic study confirms the advantage of the paraspinal sacrospinalis splitting approach in multiple intercosto-lumbar neurotizations. The approach is quick and easy and allows a good exposure of the nerve roots at the thoracic and lumbar levels. The L2, L3, and L4 roots could be satisfactorily neurotized with this procedure.

Efficient reinnervation of hindlimb muscles by thoracic motor neurons after nerve cross-anastomosis in rats.

Peripheral motor axons can regenerate through motor endoneurial tubes of foreign nerves to reinnervate different target muscles. This regenerative capacity has been brought to clinical applications for restorative surgery after nerve or root injury. In this study the authors explore the extent to which nerve cross-anastomosis between lower intercostal nerves and lumbar ventral roots would be effective in inducing reinnervation of paralyzed hindlimb muscles after spinal cord hemisection at the thoracolumbar boundary in rats. The proximal extremities of sectioned intercostal nerves T10-12 were surgically connected to the distal extremities of sectioned ipsilateral lumbar ventral roots L3-5, respectively. Motor activity reappeared 2 months postsurgery; however, locomotion was not restored and inappropriate motor patterns persisted at 9 months postsurgery. At that time, data from electrophysiological and histological studies and horseradish peroxidase retrograde labeling demonstrated efficient regrowth of thoracic motor neuron axons that reached hindlimb muscles. They also revealed a persistent maturation defect of regrown fibers, as shown by size heterogeneity and presumable extensive axonal branching. These features are consistent with reduced neural activity subsequent to continuing inappropriate motor patterns. These results indicate that cross-anastomosis of intercostal nerves with lumbar ventral roots allows efficient reinnervation of paralyzed hindlimb muscles after spinal cord hemisection in rats. Stimulating the reorganization of the neuronal circuitry in the central nervous system by locomotion training or other methods would presumably result in both functional and anatomical improvements. This experimental setting provides a convenient animal model to investigate these processes.

Efferent activity in the phrenic nerve during startle reflex in chloralose anesthetized cats

Reflex activity in the phrenic nerve was studied in chloralose anesthetized cats during development of somatic startle reflexes in limb and lower intercostal nerves. It was shown that the main component of this activity during low-threshold reflexes evoked by acoustic, tactile and low-threshold somatic afferent stimulation was depression of phrenic inspiratory activity. The following reflex discharges were prevalent components of phrenic responses to high-threshold afferent stimulation: early, propriospinal (intercostal-to-phrenic reflex) and late, suprasegmental ones. The latter were of two types: inspiratory (observed mainly during inspiration in about 75% of experiments) and expiratory (observed during expiration in 25% of experiments) which could be classified as "phrenic startle reflexes". Modulation of all responses during the respiratory cycle was described. Structural characteristics of reflex responses evoked in the phrenic nerve by stimulation of various respiratory and nonrespiratory bulbar sites as well as their respiratory modulation have been analyzed. Organization of possible neurophysiological mechanisms of phrenic responses during startle reflexes is discussed.

Respiratory modulation of the startle reflex in cats

Phase respiratory influences on reflex after-discharges in response to stimulation of the segmental nerves as well as tactile and acoustic stimulation in the limb and intercostal nerves — physiological analogs of startle reflexes (SR) were studied in unanesthetized (decerebrate) or chloralose-anesthetized cats. It was found that the level of these reflexes in the inhalation phase of respiration was 8–58% lower than during exhalation. The difference between the inhalation and exhalation phases was determined for different types of reflexes and under varying experimental conditions. Evidence was obtained that respiratory modulation of reflexes occurs mainly at the level of suprasegmental (reticular) mechanisms. Clear distinctions could be drawn between the pattern of reflex modulation in the lower intercostal nerves and those of the limbs. Findings would lead to the conclusion that the likely mechanisms underlying suprasegmental respiratory influences on these reflexes differ, as does the organization of their reticular centers.

Intercostal and abdominal muscle afferent influence on medullary dorsal respiratory group neurons

Studies were performed on anesthetized, paralyzed, artificially ventilated cats. Phrenic (C 5) efferent activity, dorsal respiratory group (DRG) neuron activity in the vicinity of the medullary solitary tract complex, and thoracic dorsal root compound action potentials were recorded during electrical stimulation of intercostal and lumbar nerves. DRG neurons were identified by their firing pattern and response to lung inflation. Phrenic activity (PA) was inhibited by stimulating external intercostal nerves T 3−T 10 internal intercostal nerves T 3−T 12, lateral branch of the main intercostal nerves T 6−T 12, or lumbar nerves 1–2. Stimulation of lower (T 9−T 11) intercostal or lumbar nerves produced a short duration (10–20 msec) facilitation of PA prior to the inhibition. Facilitation and inhibition of PA were correlated with recruitment of afferent fibers from muscle proprioceptors. Inspiratory neurons (Iα and Iβ) in the DRG were inhibited simultaneously with PA regardless of the nerves stimulated. DRG neurons which fired in phase with lung inflation (P cells) were unaffected by nerve stimulation evenn though PA was inhibited. Lower intercostal nerve (T 9−T 11) stimulation produced a brief facilitation of medullary neuron activity simultaneous with facilitation of PA. It is concluded that intercostal and abdominal muscle proprioreceptor afferents, and perhaps cutaneous afferents, reflexly alter the activity of DRG inspiratory neurons (Iα, Iβ) which drive the phrenic motoneurons. The inhibitory effect is not via P cells but may be via other interneurons in close proximity to the I cells.

DISTRIBUTION OF MOTOR AND SENSORY FIBERS IN THE INTERCOSTAL NERVES Significance in Reconstructive Surgery

If the distribution of the types of nerve fibers in the various intercostal nerves is taken into consideration, an intercostal nerve segment can be an acceptable donor nerve graft for sensory and/or motor nerve replacements. We describe the distribution of motor and sensory axons in various segments of the upper and lower intercostal nerves.

Excitability of phrenic motoneurones to afferent input from lower intercostal nerves in the spinal cat.

AbstractThe reflex connections between the lower intercostal segments and the phrenic motor pool, described in a preceding paper, has been studied further. It was found that the diaphragm on contraction could exert enough mechanical force on the lower part of the rib cage to provoke a reflex discharge in the phrenic motoneurones. The intercostal‐to‐phrenic reflex arch thus constitutes a link in a loop for self‐excitation of the phrenic nucleus which may make up for its lack of autogenetic facilitation. Up to five synchronized reverberating phrenic volleys could be recorded in response to a single diaphragmatic jerk. These were abolished by paralyzing doses of gallamine. Conduction times and excitability cycles for the loop have been studied. Examination of reflex firing probality for phrenic motoneurones has revealed considerable individual differencies in their responsiveness to each of the three afferent input parameters: a) nerve stimulated, b) strength and c) frequency of stimulation. The order of reflex recruitment of phrenic motoneurones followed the same order as found for their respiratory engagement: small spikes always appeared earlier than bigger spikes.

Studies on Intercostal Nerve Physiology

Summary and Conclusions1. Stimulation of the central end of any intercostal nerve causes a reflex inhibition of respiration and effects a concomitant drop in blood pressure. 2. The lower intercostal nerves (7-12) elicit a greater response than do the upper ones. 3. Stimulation of the intercostal branches to the parietal pleura, diaphragmatic pleura, and rectus abdominis muscle give the respiratory inhibition and lowered blood pressure (approximately 25 mm of Hg.) 4. Stimulation of sensory or intercostal fibers in the diaphragm causes reflex contraction of the abdominal musculature through reflex connection with other lower intercostal nerves. 5. Among other things, these results furnish the physiological mechanisms involved in referred pain and muscular rigidity in the lower abdominal quadrant as a result of involvement of the base of the lungs, in lobar pneumonia for example. 6. Both expiration and inspiration cause the intercostal nerves to be stimulated and thereby effect reflexly respiratory inhibitio...

Innervation of the diaphragm

On the basis of studies carried out on dogs, AA Troitskaya (Vesti. Khir. And Pogr. Obl., 1926, No. 16) found that none of the 6 lower intercostal nerves in dogs, apparently, gives motor branches to the diaphragm , the muscles of which are supplied with motor nerves exclusively from n. phrenicus; therefore cutting n. phrenici entails complete paralysis and atrophy of the phrenic muscle on the corresponding side (this paralysis in a dog is not fatal).

A CONTRIBUTION TO THE SURGERY OF THE GALL BLADDER AND DUCTS.

ANATOMY. The advancement of surgery to include the biliary passages has awakened a new interest in these structures and their relations. The surgeon found it necessary to go into the dissecting room and familiarize himself with the normal structures in this region. With this object in view, George Emerson Brewer, 1 M.D., New York, dissected and studied 160 subjects to which I wish to refer you. Mr. Morrison 2 has drawn attention to the lesser sac of the peritoneum in which the gall bladder exists, and many others have made valuable observations. The ninth costal cartilage is the external landmark of the gall bladder; in making an incision to expose it, the lower intercostal nerves should be avoided if possible. By making the perpendicular incision below the costal arch, and through the outer border of the right rectus muscle, only the ninth intercostal nerve is severed. There is not much variation in the normal position of the