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Pain caused by irritation or inflammation of an intercostal nerve, often due to herpes zoster, trauma, or compression.
The pain follows a dermatomal distribution, typically unilateral and severe, and worsens with coughing or deep breathing.
Reactivation of the varicella-zoster virus in the dorsal root ganglion produces a painful vesicular rash along the affected intercostal space.
The condition demonstrates the segmental nature of intercostal nerves.
Lesions and pain are confined to one side of the thorax.
Local anesthetic injection near the inferior border of a rib to block intercostal nerves for pain relief after rib fractures or thoracic surgery.
Usually given at multiple levels since adjacent dermatomes overlap.
Care is taken to avoid injury to the pleura and intercostal vessels.
Commonly occurs near the angle of the rib, where the bone is weakest.
Multiple fractures can cause a flail chest, leading to paradoxical respiratory movement—depression during inspiration and bulging during expiration.
Performed to aspirate pleural fluid; needle inserted just above the upper border of a rib to avoid the neurovascular bundle in the costal groove.
Common site: 7th or 8th intercostal space in the midaxillary line.
The azygos and hemiazygos veins provide an important collateral pathway between the superior and inferior vena cava.
During IVC obstruction, venous blood from the lower body can bypass through this system to the SVC.
The internal thoracic artery is preferred for coronary artery bypass grafting (CABG) because it is resistant to atherosclerosis and remains patent for years.
The artery runs close to the sternum, hence care is required during sternal puncture or chest surgery.
The parietal pleura of the thoracic wall receives sensory fibres from intercostal nerves, hence pleuritic inflammation may cause sharp chest pain localized along the intercostal space.
Injury to the thoracic sympathetic trunk (especially upper part) may produce Horner’s syndrome, characterized by ptosis, miosis, and anhidrosis on the affected side.
In SVC obstruction, blood can flow from upper thoracic intercostal veins → azygos → hemiazygos → lumbar veins → IVC, maintaining venous return.
Prominent chest wall veins are visible clinically in such cases.
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Arrangement in the Costal Groove:
Structures from above downward are — Vein, Artery, Nerve (VAN).
Muscular Layers of Intercostal Space:
From superficial to deep — External intercostal, Internal intercostal, Innermost intercostal.
Neurovascular Plane:
Lies between internal and innermost intercostal muscles.
First Rib Distinction:
The first intercostal space lacks an intercostal muscle, being filled with fibrous tissue.
Branches of Posterior Intercostal Artery:
Dorsal branch: to vertebrae and muscles of back.
Collateral branch: runs along upper border of rib below.
Lateral cutaneous branch: supplies overlying skin.
Source of Intercostal Arteries:
Posterior intercostal arteries: from thoracic aorta (except 1st & 2nd spaces, from superior intercostal artery).
Anterior intercostal arteries: from internal thoracic (upper six) and musculophrenic artery (lower spaces).
Drainage of Intercostal Veins:
Right side → Azygos vein.
Left upper spaces → Left superior intercostal vein.
Left lower spaces → Hemiazygos and accessory hemiazygos veins.
Lymphatic Drainage:
Anterior intercostal lymphatics → Internal mammary (parasternal) nodes.
Posterior intercostal lymphatics → Posterior intercostal nodes → Thoracic duct or bronchomediastinal trunk.
Internal Thoracic Artery:
Arises from first part of subclavian artery.
Divides into superior epigastric and musculophrenic arteries at the 6th intercostal space.
Lies 1 cm lateral to the sternum.
Azygos System of Veins:
Azygos vein drains right posterior thoracic wall.
Hemiazygos vein drains lower left spaces.
Accessory hemiazygos vein drains upper left spaces.
Provides collateral venous pathway between superior and inferior vena cava.
Sympathetic Trunk:
Lies anterior to neck of ribs.
Gives rise to greater (T5–T9), lesser (T10–T11), and least (T12) splanchnic nerves.
Clinical Associations:
Herpes zoster involves intercostal nerves.
Thoracocentesis performed above upper border of rib to avoid intercostal neurovascular bundle.
Internal thoracic artery used in CABG.
Azygos system provides collateral flow in vena caval obstruction.
Problem:
A 45-year-old patient complains of sharp, stabbing pain along the right chest wall, increasing on coughing or deep breathing.
Anatomical Explanation:
Pain follows the course of the intercostal nerve, commonly due to compression, inflammation, or viral infection (herpes zoster). The pain distribution corresponds to the dermatome supplied by the affected nerve.
Problem:
A man with multiple rib fractures shows a segment of chest wall moving inward during inspiration and bulging outward during expiration.
Anatomical Explanation:
Fractures in two or more adjacent ribs at two points produce a free-floating segment called a flail chest. It moves paradoxically to the rest of the thoracic wall, impairing respiration and oxygenation.
Problem:
After thoracic surgery, the patient has persistent neuralgic pain along the incision line.
Anatomical Explanation:
Pain arises due to injury or entrapment of intercostal nerves running along the costal groove. Surgical incisions should therefore be placed just above the upper border of a rib.
Problem:
A patient with multiple rib fractures is given an intercostal nerve block for pain relief.
Anatomical Explanation:
The anesthetic is injected near the inferior border of the rib above, where the intercostal nerve runs in the neurovascular bundle. Blocks are given at several levels due to overlapping dermatomes.
Problem:
A vesicular rash appears over the left side of the chest along one intercostal space.
Anatomical Explanation:
Reactivation of latent varicella-zoster virus in the dorsal root ganglion of the corresponding thoracic nerve produces pain and rash along the nerve’s dermatome.
Problem:
A doctor plans to remove fluid from the pleural cavity. Where should the needle be inserted?
Anatomical Explanation:
The needle is introduced just above the upper border of the rib (commonly in the 7th or 8th intercostal space in the midaxillary line) to avoid damaging the intercostal vessels and nerve lying in the costal groove.
Problem:
A patient with pleural effusion complains of sharp pain along the chest wall.
Anatomical Explanation:
The parietal pleura of the thoracic wall is supplied by intercostal nerves, hence inflammation causes pain referred to the same intercostal dermatome.
Problem:
Why is the internal thoracic artery preferred for coronary bypass grafting?
Anatomical Explanation:
It has a strong wall, excellent collateral supply, and resistance to atherosclerosis. It can be mobilized easily from the posterior surface of the anterior thoracic wall for anastomosis with a coronary artery.
Problem:
CT scan shows a markedly dilated azygos vein in a patient with inferior vena cava obstruction.
Anatomical Explanation:
The azygos system provides a collateral venous pathway between the superior and inferior vena cava. In IVC blockage, blood from the lower body ascends via the azygos and hemiazygos veins to reach the SVC.
Problem:
A patient presents with ptosis, miosis, and anhidrosis on one side of the face.
Anatomical Explanation:
Lesion of the upper thoracic sympathetic trunk (especially T1) interrupts sympathetic fibres to the eye and face, producing Horner’s syndrome.
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