[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [Peripheral nerve and skeletal muscle](https://durgical.com/en/general-pathology/areas/nerve-muscle/) › Traumatic and entrapment neuropathies # Traumatic and entrapment neuropathies - Lesion Nerves can be cut, stretched or squeezed. A cut nerve may regrow or form a painful tangle; a squeezed nerve at a tunnel causes numbness and weakness. Updated Nov 12, 2026 ## Key points - Seddon: neurapraxia (conduction block), axonotmesis (axon loss, endoneurium intact), neurotmesis (complete transection). - Axonal regrowth is roughly one millimetre per day, guided by Schwann cell bands of Büngner. - Traumatic neuroma: disorganized axons, Schwann cells and perineurial cells in scar at the end of a cut nerve (e.g. after amputation). - Carpal tunnel syndrome: median nerve; risk with pregnancy, hypothyroidism, acromegaly, RA, diabetes, amyloid, repetitive wrist use. - Other entrapments: ulnar at the elbow, radial in the spiral groove ('Saturday night palsy'), common fibular at the fibular head, tibial at the tarsal tunnel. - Morton neuroma: third intermetatarsal space, women with tight shoes; perineural fibrosis and vascular thickening, not a true tumour. ## What it is Physical injury to nerves includes laceration, stretch and avulsion, compression and entrapment. The severity is graded from neurapraxia (focal demyelination with an intact axon, recovering in weeks), through axonotmesis (axon divided, sheaths intact, good regrowth) to neurotmesis (whole nerve divided, regrowth needs surgical repair). When regenerating sprouts cannot find the distal stump, they form a traumatic neuroma, a painful tangle of axons and scar. Entrapment neuropathies arise where nerves pass through tight anatomic tunnels, such as the median nerve in the carpal tunnel. Morton neuroma is perineural fibrosis of a plantar digital nerve. ## Structure - Compression: focal demyelination under the pressure point, with tapering of myelin (paranodal intussusception) and axonal loss if prolonged. - Traumatic neuroma: nodule of haphazard small nerve fascicles in dense collagen. - Morton neuroma: thickened nerve with dense perineurial and endoneurial fibrosis, hyalinized arteries and mucoid change. - Regeneration: clusters of small thinly myelinated axons. ## Step by step - Pressure or stretch first disrupts myelin and blood flow, causing a reversible conduction block. - Prolonged or stronger force divides axons, which degenerate distally. - Schwann cells proliferate and form tubes; the proximal stump sends out many sprouts. - If the endoneurial tubes are intact, sprouts reach their targets and function returns. - If the nerve is completely divided and not repaired, sprouts tangle in scar and form a painful neuroma. ## Clinical notes - Carpal tunnel: night tingling of the thumb, index and middle fingers, positive Phalen and Tinel tests, thenar wasting late. - Common fibular palsy after leg crossing or a tight cast: foot drop with sensory loss on the dorsum of the foot. - Nerve conduction studies localize the lesion and grade its severity. ## Memory aid Pressure blocks, stretch breaks the wire, a cut breaks the cable; the cable's cut end tangles into a neuroma. ## Test yourself Think of the answer, then tap the question to see it. ## What is neurapraxia? Focal conduction block from demyelination with an intact axon; it recovers in weeks. ## What is a traumatic neuroma? A disorganized mass of regenerating axons, Schwann cells and scar at the end of a cut nerve. ## Which conditions predispose to carpal tunnel syndrome? Pregnancy, hypothyroidism, acromegaly, rheumatoid arthritis, diabetes, amyloidosis and repetitive wrist use. ## Is Morton neuroma a true neoplasm? No. It is perineural fibrosis of a plantar digital nerve from repeated compression. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/general-pathology/traumatic-and-entrapment-neuropathies/) [More Pathology questions →](https://durgical.com/en/practice/?f=pathology) ## Elsewhere in DurgiPedia - [Nerve injury and regeneration (Wallerian degeneration)](https://durgical.com/en/histology/nerve-injury-and-regeneration/) ## Connections ## Related 4 - [Peripheral nerve injury: axonal vs demyelinating](https://durgical.com/en/general-pathology/peripheral-nerve-injury-axonal-vs-demyelinating/) - [Diabetic neuropathy](https://durgical.com/en/general-pathology/diabetic-neuropathy/) - [Inherited neuropathies: Charcot–Marie–Tooth and others](https://durgical.com/en/general-pathology/inherited-neuropathies-charcot-marie-tooth-and-others/) - [Schwannoma and neurofibromatosis type 2](https://durgical.com/en/general-pathology/schwannoma-and-neurofibromatosis-type-2/) ## Related conditions 8 - [Carpal tunnel syndrome](https://durgical.com/en/conditions/carpal-tunnel-syndrome/) - [Cubital tunnel syndrome (ulnar neuropathy at the elbow)](https://durgical.com/en/conditions/cubital-tunnel-syndrome/) - [Common Fibular (Peroneal) Nerve Injury](https://durgical.com/en/conditions/common-fibular-nerve-injury/) - [Morton neuroma](https://durgical.com/en/conditions/morton-neuroma/) - [Tarsal tunnel syndrome](https://durgical.com/en/conditions/tarsal-tunnel-syndrome/) - [Brachial plexus injury](https://durgical.com/en/conditions/brachial-plexus-injury/) - [Meralgia paresthetica](https://durgical.com/en/conditions/meralgia-paresthetica/) - [Axillary nerve injury](https://durgical.com/en/conditions/axillary-nerve-injury/) [← All of general pathology](https://durgical.com/en/general-pathology/) Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given. Sources: [Carpal Tunnel Syndrome](https://www.ncbi.nlm.nih.gov/books/NBK448179/) (StatPearls (NCBI Bookshelf), 2025); [Ulnar Neuropathy](https://www.ncbi.nlm.nih.gov/books/NBK534226/) (StatPearls (NCBI Bookshelf), 2025); [Morton Neuroma](https://www.ncbi.nlm.nih.gov/books/NBK470249/) (StatPearls (NCBI Bookshelf), 2025). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/general-pathology/traumatic-and-entrapment-neuropathies/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/traumatic-and-entrapment-neuropathies/