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Intercostal nerves
Intercostal nerves
Intercostal nerves
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Intercostal nerves
Diagram of the course and branches of a typical intercostal nerve.
Intercostal nerves, the superficial muscles having been removed.
Details
FromThoracic nerves (T1-T11)
InnervatesIntercostal muscle
Identifiers
Latinnervi intercostales
MeSHD007367
TA98A14.2.04.006
TA26471
FMA75467
Anatomical terms of neuroanatomy

The intercostal nerves are part of the somatic nervous system, and arise from the anterior rami of the thoracic spinal nerves from T1 to T11.[1][2] The intercostal nerves are distributed chiefly to the thoracic pleura and abdominal peritoneum, and differ from the anterior rami of the other spinal nerves in that each pursues an independent course without plexus formation.[1][3]

The first two nerves supply fibers to the upper limb and thorax; the next four distribute to the walls of the thorax; the lower five supply the walls of the thorax and abdomen.[3] The 7th intercostal nerve ends at the xyphoid process of the sternum.[3] The 10th intercostal nerve terminates at the navel.[3] The 12th (subcostal) thoracic is distributed to the walls of the abdomen and groin.[3] Each of these fibers contains around 1300 axons.[2]

Unlike the nerves from the autonomic nervous system that innervate the visceral pleura of the thoracic cavity, the intercostal nerves arise from the somatic nervous system. This enables them to control the contraction of muscles, as well as provide specific sensory information regarding the skin and parietal pleura. This explains why damage to the internal wall of the thoracic cavity can be felt as a sharp pain localized in the injured region. Damage to the visceral pleura is experienced as an un-localized ache.

The 1st thoracic nerve

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The anterior division of the first thoracic nerve divides into two branches. The larger branch leaves the thorax in front of the neck of the first rib, and enters the brachial plexus. The smaller branch, the first intercostal nerve, runs along the first intercostal space, and ends on the front of the chest as the first anterior cutaneous branch of the thorax. Occasionally, this anterior cutaneous branch is missing.

The first intercostal nerve rarely gives off a lateral cutaneous branch; but sometimes sends a small branch to communicate with the intercostobrachial.

From the second thoracic nerve it frequently receives a connecting twig, which ascends over the neck of the second rib. This nerve was first described by Kuntz in 1927. There is considerable anatomic variation, but Kuntz nerve may be present in 40-80% of the population.[4][5]

The upper thoracic nerves: 2nd–6th

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The anterior divisions of the second, third, fourth, fifth, and sixth thoracic nerves, and the small branch from the first thoracic, are confined to the walls of the thorax, and are named thoracic intercostal nerves.

They pass forward in the intercostal spaces below the intercostal vessels. At the back of the chest they lie between the pleura and the posterior intercostal membranes, but soon they run between the internal intercostals and the innermost intercostals then anteriorly they lie between the pleura and the internal intercostals.

Near the sternum, they cross in front of the internal mammary artery and transversus thoracis muscle, pierce the intercostales interni, the anterior intercostal membranes, and pectoralis major, and supply the integument of the front of the thorax and over the mammary gland, forming the anterior cutaneous branches of the thorax; the branch from the second nerve unites with the anterior supraclavicular nerves of the cervical plexus.

The fourth intercostal nerve is innervated by cutaneous slowly-adapting and rapidly-adapting mechanoreceptors, especially by ones densely-packed under the areola; innervation subsequently triggers oxytocin release, which, when in the peripheral bloodstream, causes myoepithelial cell contraction and lactation: this is an example of a non-nerve-innervation muscular reflex.

Branches

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Numerous slender muscular filaments supply the Intercostales, the Subcostales, the Levatores costarum, the Serratus posterior superior, and the Transversus thoracis. At the front of the thorax some of these branches cross the costal cartilages from one intercostal space to another.

  • Lateral cutaneous branches (rami cutanei laterales) are derived from the intercostal nerves, about midway between the vertebræ and sternum; they pierce the Intercostales externi and Serratus anterior, and divide into anterior and posterior branches.
  • The anterior branches run forward to the side and the forepart of the chest and skin, fourth nerve anterior branches supplying the areola and the mamma; those of the fifth and sixth nerves supply the upper digitations of the Obliquus externus abdominis.
  • The posterior branches run backward, and supply the skin over the scapula and Latissimus dorsi.

The lateral cutaneous branch of the second intercostal nerve does not divide, like the others, into an anterior and a posterior branch; it is named the intercostobrachial nerve.

The lower thoracic nerves: 7th–11th

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See also: Thoraco-abdominal nerves

The lower thoracic nerves: 12th

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Anterior division

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See also: Subcostal nerve

Lateral cutaneous branch

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The lateral cutaneous branch of the last thoracic nerve is large, and undivided.

It perforates the internal and the external oblique muscles, descends over the iliac crest in front of the lateral cutaneous branch of the iliohypogastric nerve, and is distributed to the skin of the front part of the gluteal muscles, some of its filaments extending as low as the greater trochanter of the femur.

Additional images

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  • Nervous system
    Nervous system
  • Intercostal spaces, viewed from the left
    Intercostal spaces, viewed from the left
  • Brachial plexus
    Brachial plexus
  • Brachial plexus with courses of spinal nerves shown
    Brachial plexus with courses of spinal nerves shown

See also

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References

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[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Intercostal nerves

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from Grokipedia
The intercostal nerves are the ventral rami of the thoracic spinal nerves from T1 to T11 that provide mixed motor and sensory innervation to the chest wall, , parietal pleura, and overlying skin, while the T12 nerve is designated as the . These nerves originate from the anterior divisions of the spinal nerves at their respective vertebral levels and enter the intercostal spaces via the costal groove on the inferior aspect of each , traveling alongside the intercostal artery and in a protected by the internal intercostal muscle. Functionally, they facilitate respiration by innervating the (external, internal, and innermost), which elevate and depress the during , and supply sensory feedback from the thoracic and upper abdominal dermatomes. Structurally, the intercostal nerves are classified into typical (T3–T6), atypical (T1–T2 and T7–T11), and the , with typical nerves remaining confined to their intercostal spaces to innervate local muscles and skin, while atypical ones extend further—T1 contributing to the , T2–T6 providing lateral and anterior cutaneous branches to the trunk, and T7–T11 () piercing the abdominal muscles to supply the anterolateral . Each nerve gives off key branches, including gray and white rami communicantes for autonomic connections, muscular branches to the and subcostal muscles, collateral branches for the lower intercostal space, and cutaneous branches (lateral near the midaxillary line and anterior near the ) that distribute sensory fibers to the skin of the and upper , including specialized areas like the nipple-areolar complex. Blood supply to these nerves derives from the posterior (branches of the costocervical trunk via the supreme intercostal artery for the upper spaces and from the for the lower spaces) and anterior intercostal arteries (from the internal thoracic or musculophrenic arteries), with veins draining correspondingly. Clinically, the intercostal nerves are significant in procedures such as intercostal nerve blocks for managing thoracic and from conditions like rib fractures, post-surgical , or herpes zoster , where blockade can alleviate symptoms but risks complications like or . They also play a role in , such as neurotization for injuries, where multiple intercostal nerves (e.g., T3–T5) are transferred to restore elbow flexion, abduction, or sensation, leveraging their high motor fiber content (approximately 40%) and potential for central to achieve voluntary control. Damage to these nerves during insertion or thoracic surgery can lead to intercostal , characterized by sharp, burning along the affected dermatome, often requiring pharmacological intervention or targeted blocks.

Overview

Definition and Origin

The intercostal nerves are mixed peripheral nerves of the that provide sensory innervation to the skin and parietal pleura of the , motor innervation to the , and autonomic (sympathetic) modulation to associated structures. They arise from the anterior (ventral) rami of the thoracic spinal nerves T1 through T11, coursing within the intercostal spaces between adjacent to supply the lateral and anterior thoracic regions. The T12 anterior ramus, known as the , follows a similar path but below the 12th rib and is not classified as a true intercostal nerve. In terms of spinal levels, the T1 anterior ramus primarily contributes to the , providing limited intercostal innervation only to the first , whereas T2 through T11 form the classic intercostal nerves with segmentally organized distributions. The (T12) extends to the , innervating the lower intercostal and abdominal muscles. This segmental arrangement reflects the metameric organization of the thoracic spine. Embryologically, the intercostal nerves originate from the ventral rami of thoracic spinal nerves during the differentiation of somites into sclerotome, , and dermatome components, a process that occurs between weeks 4 and 8 of gestation. In early development, akin to observations in embryos at embryonic days 13–15 (equivalent to human weeks 5–8), these nerves initially exhibit bifurcated ventral branches that later consolidate into the mature single-branch morphology, ensuring patterned innervation of the body wall. The composition of each intercostal nerve includes sensory (afferent) fibers with cell bodies in the , which transmit somatic and visceral sensations via the dorsal root; motor (efferent) fibers arising from alpha and gamma motor neurons in the ventral horn of the , innervating skeletal muscles; and preganglionic sympathetic autonomic fibers from the intermediolateral cell column (T1–L2 levels), which exit via the ventral root and connect to the sympathetic chain through white rami communicantes for postganglionic distribution. This mixed fiber profile enables the nerves' multifunctional role in thoracic innervation.

General Course and Relations

The intercostal nerves, arising from the anterior rami of the thoracic spinal nerves T1 through T11, emerge from the intervertebral foramina and immediately enter the corresponding intercostal spaces, traveling anteriorly within the paravertebral gutter before crossing the and the posterior intercostal membrane to lie external to the parietal pleura. These nerves then proceed laterally and inferiorly along the inferior border of each , entering the costal groove where they are protected by the overhanging edge of the above, running between the inferiorly and the internal intercostal muscle superiorly. In this , the intercostal nerve occupies the inferior position relative to the intercostal vein (superior) and artery (middle), following the mnemonic "" from superior to inferior. As the nerves advance anteriorly within the costal groove, they traverse the layers of the , passing through the internal intercostal muscle and the external intercostal muscle (or its anteriorly), before emerging near the anterior chest wall. Near the mid-axillary line, each typical intercostal nerve (primarily T2 through T6) divides into a continuing main trunk and a lateral cutaneous branch, with the latter piercing the to supply the lateral thoracic skin. The main trunk then continues as the anterior division, which will give rise to the anterior cutaneous branch near the . While the course is generally uniform for most intercostal nerves, variations occur at the extremes: the first intercostal nerve (T1) takes a more superior trajectory, with its larger superior ramus contributing to the rather than fully following the intercostal path, and lacking typical lateral cutaneous branches. In contrast, the twelfth thoracic nerve (T12), known as the , does not travel in a costal groove but courses inferior to the , entering the posterior to the lateral arcuate ligament. These differences highlight adaptations for and abdominal innervation, respectively, while preserving the core intercostal template for T2 through T11.

Specific Intercostal Nerves

First Thoracic Nerve

The first thoracic nerve (T1) arises from the anterior ramus of the first thoracic and exhibits a partial intercostal role, as its primary contribution integrates into the formed by the anterior rami of C5 through T1, while a smaller branch functions as the first intercostal nerve to supply the first . The smaller intercostal branch enters the first and runs anteriorly within the costal groove inferior to the first , often piercing the ; it notably lacks a typical lateral cutaneous branch and typically does not give an anterior cutaneous branch. This atypical course distinguishes it from the more standardized path of subsequent thoracic nerves, which descend inferior to their respective . In terms of innervation, the portion of T1 contributing to the provides sensory fibers to the and medial arm, while its motor components, via the lower trunk of the , supply the intrinsic hand muscles through the . This dual role in arm innervation renders T1 less purely intercostal compared to T2 through T11, with clinical implications such as potential involvement in upper limb neuropathies or from thoracic procedures.

Upper Thoracic Nerves (2nd–6th)

The upper thoracic intercostal nerves, designated as T2 through T6, represent the typical intercostal nerves that adhere closely to the standard anatomical pattern observed in the thoracic region. These nerves originate from the anterior rami of the respective thoracic spinal nerves and emerge from the intervertebral foramina to enter the corresponding s, positioned between the parietal pleura inferiorly and the posterior intercostal membrane superiorly. Once in the , each nerve courses anteriorly within the subcostal groove of the , accompanied by the intercostal and superiorly in the order of vein, artery, nerve from superior to inferior, and lies between the innermost and internal . This configuration allows the nerves to maintain a consistent through the second to sixth intercostal spaces, providing both motor and sensory innervation to the structures. The anterior rami of T2–T6 nerves divide into several branches shortly after exiting the spinal column, with the lateral and anterior cutaneous branches serving as the primary terminal divisions responsible for . The lateral cutaneous branch arises near the posterior axillary line and pierces the at the mid-axillary line, subsequently dividing into anterior and posterior branches that supply sensory innervation to the skin of the lateral . In contrast, the anterior cutaneous branch continues anteriorly as the terminal branch, emerging near the after perforating the internal intercostal muscle and, in some cases, the muscle; it then bifurcates into medial and lateral branches to innervate the skin of the anterior . Additional branches include muscular twigs that supply the , levatores costarum, and serratus posterior superior, as well as a collateral branch that parallels the main nerve to innervate the parietal pleura and of the ribs. A notable variation occurs with the T2 nerve, where its lateral cutaneous branch forms the , which extends beyond the typical thoracic distribution to provide sensory innervation to the skin of the upper chest, , and medial aspect of the upper arm, occasionally communicating with the medial brachial . This extension distinguishes T2 from the more uniform pattern of T3–T6, which lack such extracostal branches and instead focus innervation on the , parietal pleura, and overlying thoracic skin without significant deviations. The T3–T6 nerves thus exhibit minimal anatomical variability, maintaining a straightforward course that supports their role in segmental thoracic wall innervation. In terms of spatial relations, the T2–T6 nerves occupy the second through sixth intercostal spaces, with their dermal supply progressively covering the lateral and anterior aspects of the chest wall in a dermatomal , corresponding to increasingly caudal segments of the . This ensures comprehensive sensory coverage of the upper thoracic dermatomes, with the lateral cutaneous branches contributing to the lateral chest wall sensation and the anterior branches to the parasternal , facilitating precise localization of thoracic sensations.

Lower Thoracic Nerves (7th–11th)

The lower thoracic nerves, specifically the 7th through 11th intercostal nerves (T7–T11), arise from the anterior rami of the corresponding thoracic spinal nerves and play a transitional role in innervating both the lower and the upper . These nerves emerge from the intervertebral foramina at levels T6/T7 to T10/T11 and course anterolaterally within their respective intercostal spaces, running in the costal groove along the inferior border of the ribs alongside the intercostal vessels (in the order of , , from superior to inferior). Unlike the more superior intercostal nerves, the T7–T11 segments have shorter intercostal portions due to their early divergence toward the abdominal region, with their anterior divisions becoming notably larger to accommodate innervation of the abdominal musculature. As these nerves proceed, their anterior divisions pass below the costal margin and continue as thoracoabdominal nerves, penetrating the abdominal wall to supply the external oblique, internal oblique, transversus abdominis, and rectus abdominis muscles with motor innervation, as well as the overlying skin and parietal peritoneum with sensory fibers. The lateral cutaneous branches emerge approximately at the mid-axillary line, providing sensory innervation to the skin over the lower ribs (for T7–T8) and the anterolateral upper abdomen (for T9–T11). The anterior cutaneous branches, meanwhile, travel medially, piercing the posterior rectus sheath and emerging through the anterior rectus sheath near the midline to supply the skin of the anterior abdominal wall, with T7 near the xiphoid process, T10 at the level of the umbilicus, and T11 to the lower abdomen. In terms of anatomical relations, the T7–T11 nerves traverse the lower intercostal spaces, lying deep to the internal intercostal muscle and superficial to the and , in close proximity to the diaphragmatic attachments along the lower ribs. They cross the (at the level of the 10th , approximately L2 vertebral level) as they transition into the , running in the neurovascular plane between the transversus abdominis and internal oblique muscles before reaching the . This positioning facilitates their role in bridging thoracic and abdominal innervation, with the thoracoabdominal extensions of T7–T11 differing from the more purely subcostal path of the T12 nerve by maintaining a partial intercostal trajectory before abdominal entry.

Subcostal Nerve (12th Thoracic Nerve)

The , arising as the anterior ramus of the twelfth thoracic spinal nerve (T12), differs from the typical in its trajectory, coursing along the inferior border of the twelfth rib in a subcostal position rather than within an intercostal groove. Emerging from the T12 , it travels as part of a with the subcostal and , passing posterior to the lateral arcuate ligament and anterior to the origin of the before descending into the . This path positions it deep to the costal origin of the quadratus lumborum initially, then within the neurovascular plane between the transversus abdominis and internal oblique muscles after perforating the transversus abdominis . The subcostal nerve features a prominent anterior division that primarily supplies motor innervation to key muscles, including the transversus abdominis, quadratus lumborum, internal oblique, external oblique, rectus abdominis, and pyramidalis. It also gives rise to a lateral cutaneous branch that emerges near the , typically at the mid-axillary line or approximately 5 cm posterior to the , after which it pierces the internal and external oblique muscles to reach the skin. The subcostal nerve also gives rise to an anterior cutaneous branch that pierces the rectus abdominis to supply the skin of the suprapubic region. Additionally, the nerve provides sensory innervation to the skin overlying the buttock (anterior gluteal region) and lateral thigh, extending toward the , while communicating with the (from L1) to facilitate shared sensory and motor contributions in the lower abdominal and pelvic regions. Anatomical variations in the include its occasional contribution to the formation of the through connections with L1 roots, as well as cases where the lateral cutaneous branch may be absent or reduced in some individuals, potentially altering sensory distribution in the gluteal and areas.

Branches and Distribution

Lateral Cutaneous Branches

The lateral cutaneous branches of the intercostal nerves originate from the anterior rami of the thoracic spinal nerves (T2–T12), typically emerging near the midaxillary line as the intercostal nerve travels within the costal groove. These branches are absent in the first intercostal nerve (T1), which primarily contributes to the without typical cutaneous divisions. In the second intercostal nerve (T2), the lateral cutaneous branch is notably enlarged and known as the , which extends to innervate the skin of the and medial upper arm. For T3–T11, the branches arise consistently from the main intercostal trunk, while the (T12) may give rise to a lateral cutaneous branch in some individuals, though this is variable and often absent. From their origin, these branches course laterally through the intercostal space, piercing the internal and external intercostal muscles before passing through the serratus anterior muscle to reach the subcutaneous tissue of the lateral thoracic and abdominal walls. This path positions them approximately at the midaxillary line, where they divide into anterior (ventral) and posterior (dorsal) divisions shortly after emerging from the deep musculature. The anterior division proceeds forward to supply the skin over the anterolateral aspect of the chest or abdomen, while the posterior division travels backward to innervate the skin along the posterolateral regions. These divisions maintain a segmental arrangement, with each branch corresponding to the dermatome level of its originating rib, facilitating precise sensory mapping of the lateral body wall. In terms of distribution, the lateral cutaneous branches of T2–T6 primarily supply the skin of the , lateral chest wall, and lateral aspects of , providing sensory innervation that aligns with the upper thoracic dermatomes. For T7–T11, these branches extend to the lateral , covering the skin from the lower to the and contributing to the thoracoabdominal dermatomes. The T12 branch, when present, targets the superolateral gluteal region or upper lateral , though its variability can lead to overlapping innervation from adjacent . Overall, these branches ensure comprehensive sensory coverage of the lateral trunk, distinct from the anterior cutaneous branches that handle medial and ventral regions.

Anterior Cutaneous Branches

The anterior cutaneous branches arise as terminal divisions from the anterior rami of the thoracic spinal nerves (T2–T12), forming smaller medial components of the intercostal nerves that course forward through the intercostal spaces alongside the intercostal vessels. These branches travel medially within the costal groove, passing deep to the internal intercostal muscle and between the internal intercostal muscle and the before continuing their trajectory. In the upper thoracic levels (T2–T6), the anterior cutaneous branches pierce the internal and , then perforate the muscle near the (parasternal region) to emerge and supply the skin of the anterior chest wall. For the lower levels (T7–T11), known as , and the (T12), these branches descend anteroinferiorly between the transversus abdominis and internal oblique muscles, piercing the posterior and to exit at the and innervate the anterior skin. Each branch typically divides into lateral and medial perforating filaments upon emergence, providing sensory innervation to the overlying and subcutaneous tissues. The distribution of these branches is segmental: T2–T6 supply the parasternal and anterior chest skin up to the level of the xiphoid process, while T7–T12 extend to the , with T10 reaching the and T12 providing sensation to the suprapubic skin. This pattern ensures comprehensive dermatomal coverage of the anterior trunk without overlap from lateral cutaneous contributions.

Collateral and Muscular Branches

The collateral branches of the intercostal nerves arise from the ventral rami of the thoracic spinal nerves T3 through T11 shortly after their formation, typically near the angles of the . These branches run parallel and inferior to the main intercostal , coursing along the superior of the rib below within the , and they anastomose with the collateral branches of the adjacent intercostal nerves both superiorly and inferiorly. These collateral branches primarily provide motor innervation to the in the inferior portion of the space, including the internal and innermost , as well as sensory supply to the parietal pleura and of the . In the typical intercostal nerves (T3 through T6), the collateral branches follow a consistent path deep to the main nerve, contributing to the stabilization of the by innervating these musculature layers. Separate from the collateral branches, the main intercostal nerves emit multiple muscular branches that directly supply the musculature, including the external intercostal, internal intercostal, innermost intercostal, subcostal, transversus thoracis, and serratus posterior superior muscles. For the lower thoracic nerves (T7 through T11), these muscular branches extend beyond the thoracic cage into the , innervating the internal oblique, external oblique, and transversus abdominis muscles, while the (T12) similarly supplies abdominal obliques and other anterolateral abdominal muscles. The first intercostal nerve (T1) provides limited muscular innervation to the first , as the majority of its fibers contribute to the . Additionally, each intercostal nerve connects to the through gray and white rami communicantes, which transmit postganglionic sympathetic fibers (via gray rami) for and control to the blood vessels and sweat glands in the and , while white rami carry preganglionic fibers from the levels T1 to L2.

Functions and Innervation

Sensory Functions

The intercostal nerves provide somatic sensory innervation to the skin of the thoracic and upper abdominal walls through their lateral and anterior cutaneous branches, conveying sensations of touch, , and temperature via dermatomes corresponding to spinal levels T2 through T12. These dermatomes form horizontal bands around the trunk, with T2 to T6 aligning nearly horizontally over the chest, while T7 to T12 descend slightly to cover the ; notably, the T10 dermatome reaches the level of the umbilicus, and T12 extends to the suprapubic . There is segmental overlap in these dermatomes, such as with cervical levels C3 to T2 in the upper and level L1 near the lower , ensuring continuous sensory coverage without distinct gaps. In addition to somatic functions, the intercostal nerves carry visceral sensory afferents from structures like the parietal pleura and , primarily through collateral branches and sympathetic fibers that join the nerves. For instance, levels T2 to T6 innervate the parietal pleura, while T7 to T11 supply the parietal ; these pathways transmit and other sensations from thoracic and abdominal cavities. Sympathetic visceral afferents from the , including the and upper , travel via fibers from spinal levels T5 to T9, integrating sensory input for viscerosomatic reflexes. Proprioceptive feedback from the is also mediated by sensory fibers within the intercostal nerves, contributing to respiratory monitoring by detecting muscle stretch and position during . This sensory input helps coordinate thoracic expansion and maintains rhythmic ventilatory control.

Motor Functions

The intercostal nerves provide motor innervation to the primarily through their muscular branches, which arise along the course of each nerve within the intercostal spaces. The , responsible for elevating the during inspiration, and the internal intercostal muscles, which depress the to aid expiration, receive segmental supply from the intercostal nerves at levels T1 through T11. However, the contribution from the first intercostal nerve (T1) is minimal, as much of its anterior ramus contributes to the rather than the musculature. The lower intercostal nerves, particularly T7 through T12, extend their motor supply to the muscles of the , enabling trunk flexion and rotation. Specifically, the (T7–T11) innervate the external oblique, internal oblique, transversus abdominis, and rectus abdominis muscles, while the (T12) also contributes to these structures. Additionally, the (T12) innervates the quadratus lumborum, supporting lateral trunk flexion and posture maintenance. In respiration, the intercostal nerves play a secondary role by coordinating the contraction of intercostal and abdominal muscles to expand and contract the , thereby altering volume to assist ventilation; the primary diaphragmatic innervation is provided by the (C3–C5). This motor coordination ensures efficient inspiratory elevation of the via external intercostals and expiratory depression via internal intercostals and abdominal muscles.

Clinical Significance

Intercostal Neuralgia and Pain Syndromes

Intercostal neuralgia is a condition characterized by unilateral, sharp or burning pain that follows the distribution of one or more intercostal nerves, typically affecting the chest wall, , or upper abdomen. This pain often manifests as a band-like sensation radiating along the affected dermatome, resulting from irritation, inflammation, or compression of the intercostal nerves. It is commonly associated with post-herpetic following varicella-zoster reactivation ( zoster), where persists in 10-20% of cases after the rash resolves, or with traumatic injuries such as fractures or surgical procedures like , which can lead to post-thoracotomy pain syndrome in 25-80% of patients. Common non-shingles causes include mechanical compression from rib fractures or hypermobility in (primarily involving the 8th to 10th ribs), where displaced impinges on the intercostal nerves, producing localized or radiating pain. Muscle strain in the chest wall or thoracic spine issues, such as herniated discs, can also contribute to band-like back-to-chest pain, though such pain is often more fixed in position, not strictly band-like, and bilateral. Inflammatory processes, such as intercostal from infections or herniated thoracic discs (slipped discs) compressing nerve roots, can also trigger the condition, alongside idiopathic cases without identifiable etiology. , a form of compression at levels T7-T11, further contributes by trapping branches of the intercostal nerves against the abdominal . Symptoms typically involve sharp, stabbing, or aching pain that wraps around the chest or in a dermatomal pattern, often intensified by deep breathing, coughing, sneezing, or trunk movements. This occurs because the intercostal nerves pass between the ribs and are involved in respiratory movements, so deep inhalation stretches or irritates them, worsening the pain. Accompanying features may include tenderness over the affected , a popping or clicking sensation in cases of rib hypermobility, and occasional or tingling, though complete is rare. Diagnosis relies on a detailed clinical history and to identify the dermatomal pain distribution, with maneuvers like Schepelmann’s sign (pain reproduction by hooking fingers under the rib margin and lifting) aiding confirmation. It is differentiated from cardiac or pulmonary pathologies through exclusion via , chest imaging, or levels when indicated, as the pain's neuropathic quality and lack of systemic symptoms guide the assessment. Visceral problems like heart, lung, or gallbladder issues typically present with pain that is not strictly horizontal band-like, shows poor response to heat, and is accompanied by additional symptoms such as shortness of breath, nausea, or sweating, unlike the tenderness and positional exacerbation seen in intercostal neuralgia. Diagnostic intercostal blocks can provide both confirmatory and therapeutic benefit. Treatment for intercostal neuralgia and related conditions such as chest wall muscle strain is primarily conservative, emphasizing pain relief and recovery. Nonsteroidal anti-inflammatory drugs (NSAIDs), including ibuprofen or indomethacin, are commonly used to reduce inflammation and pain. Physical therapy interventions, such as heat packs, massage, ultrasound, and gentle stretches, aid in improving mobility and alleviating symptoms. Rest is recommended, with avoidance of aggravating activities like pulling movements or shallow breathing. For chest wall muscle strain specifically, additional measures include ice or heat application and over-the-counter analgesics. Most cases resolve within days to a week, though some may take several weeks. In unresponsive or chronic cases, intercostal nerve blocks with local anesthetic and steroids, radiofrequency ablation, or acupuncture may be considered.

Surgical and Procedural Relevance

Intercostal nerve blocks are a common regional anesthesia technique used for perioperative , particularly following thoracic surgeries such as , where local anesthetics are injected near the in the costal groove via a posterior approach to provide targeted analgesia. This procedure targets the intercostal nerves from T1 to T11, blocking sensory transmission to alleviate acute postoperative pain, with studies demonstrating reduced requirements and improved pain scores in the first 24 hours after thoracic surgery. The block is performed by advancing a needle superior to the rib margin to avoid the , often under guidance to enhance precision and minimize complications like . In surgical contexts, intercostal nerves are vulnerable to iatrogenic during procedures involving the thoracic and abdominal walls, leading to chronic or motor deficits. frequently risks damage to these nerves due to retraction or incision through the intercostal spaces, resulting in post- in up to 50% of cases. Similarly, and axillary dissection pose risks to the intercostobrachial branch and intercostal nerves T2–T6, with occurring from dissection in the and contributing to persistent sensory disturbances in 20–30% of patients. , especially in the upper abdominal region, can compromise lower intercostal nerves through mesh placement or tissue manipulation, potentially causing weakness. Anatomical landmarks of the intercostal nerves guide needle placement in diagnostic and therapeutic procedures, ensuring safe access to thoracic structures. In pleural taps (thoracentesis), insertion occurs in the 6th to 8th intercostal space along the midaxillary or posterior lines, with the needle directed just superior to the rib to avoid the inferiorly located neurovascular bundle, thereby reducing risks of nerve injury or vascular puncture. For epidural access, the paravertebral positioning of intercostal nerve roots informs catheter placement in the thoracic epidural space, blocking multiple levels for intraoperative analgesia. The subcostal nerve (T12) is particularly relevant in lumbar incisions, such as lateral approaches to the spine, where its course along the abdominal wall must be preserved to prevent postoperative flank bulge or hernia from denervation of the transversus abdominis. Contemporary advancements, including ultrasound imaging, have significantly improved procedural safety by allowing real-time visualization of nerve anatomy during blocks and taps, reducing complication rates compared to landmark-based techniques.

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  17. https://medicine.uams.edu/neuroscience/education/medical-school-courses/human-structure-module/anatomy-tables/nerve-tables/nerves-of-the-thorax/
  18. https://pmc.ncbi.nlm.nih.gov/articles/PMC7540051/
  19. https://www.ncbi.nlm.nih.gov/books/NBK559218/
  20. https://www.kenhub.com/en/library/anatomy/quadratus-lumborum-muscle
  21. https://teachmeanatomy.info/thorax/muscles/thoracic-cage/
  22. https://www.ncbi.nlm.nih.gov/books/NBK560865/
  23. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7901126/
  24. https://www.mayoclinic.org/diseases-conditions/chest-pain/symptoms-causes/syc-20370838
  25. https://www.merckmanuals.com/home/heart-and-blood-vessel-disorders/symptoms-of-heart-and-blood-vessel-disorders/chest-pain
  26. https://my.clevelandclinic.org/health/symptoms/musculoskeletal-chest-pain
  27. https://pmc.ncbi.nlm.nih.gov/articles/PMC8593761/
  28. https://www.ncbi.nlm.nih.gov/books/NBK555900/
  29. https://pmc.ncbi.nlm.nih.gov/articles/PMC3496527/
  30. https://pmc.ncbi.nlm.nih.gov/articles/PMC8301281/
  31. https://pmc.ncbi.nlm.nih.gov/articles/PMC8613357/
  32. https://www.ncbi.nlm.nih.gov/books/NBK441866/
  33. https://pmc.ncbi.nlm.nih.gov/articles/PMC9840019/
  34. https://pubmed.ncbi.nlm.nih.gov/28532913/
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