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Axonotmesis is a disruption of nerve cell axon, with Wallerian degeneration occurring below and slightly proximal to the site of injury.^[1] If axons, and their myelin sheath are damaged, but schwann cells, the endoneurium, perineurium and epineurium remain intact is called axonotmesis. Axonotmesis is usually the result of a more severe crush or contusion than neuropraxia.^[2] In axonotmesis, the proximal section is repaired by creating a sprout with its growth cone, but in the distal section occurs axonal degeneration. The rate of outgrowth of regenerating nerve fibers is about 1 mm to 2 mm per day, so that the recovery of conduction to a target structure depends on not only regrowth into the appropriate endoneurial tube (endoneurium), but also on the distance involved.^[3]

Assessment[edit]

A nerve contains sensory fibers, motor fibers, or both. Sensory fibers lesions cause the sensory problems below to the site of injury. Motor fibers injuries may involve lower motor neurons, sympathetic fibers, and or both.

Assessment items include:

Sensory fibers that send sensory information to the central nervous system.
Motor fibers that create the contraction of skeletal muscle.
Sympathetic fibers that innervate the skin, and blood vessels of the upper and lower limbs.

In assessment, sensory-motor defects may be mild, moderate, or severe. Damage to motor fibers results in paralysis of the muscles. Nervous plexus injuries create the more signs and symptoms from sensory-motor problems (such as brachial plexus injuries). In these cases, the prognosis depends on the amount of damage and the degree of functional recovery.

EMG and NCV findings[edit]

Changes in EMG:

Electromyography (EMG) is a medical test performed to evaluate and record the electrical activity (electromyogram) produced by skeletal muscles using an instrument called electromyograph.^[4] In axonotmesis, EMG changes (2 to 3 weeks after injury) in the denervated muscles include:

Fibrillation potentials (FP)
Positive sharp waves

Changes in NCV (nerve conduction velocity):

EMG test is often performed together with another test called nerve conduction study, that measures the conducting function of nerves.^[5] NCV study shows loss of nerve conduction in the distal segment (3 to 4 days after injury). According to NCV study, in axonotmesis there is an absence of distal sensory-motor responses.

Treatment[edit]

Treatment of axonotmesis consists of :

Physical therapy. Physical therapy aims include:
- Pain relief
- Maintain range of motion
- Reducing muscular atrophy
- Patient education
Use of assistive devices (Orthotic needs)
Surgical treatment (For example, in cases of surrounding scar tissue)

Prognosis[edit]

The prognosis is usually good in terms of recovery. Rate of recovery depends on the distance from the site of injury, with axonal regeneration occurring at 1 to 4 mm/day.^[6] Nerve regeneration may take several months.

References[edit]

^ Otto D.Payton & Richard P.Di Fabio et al.Manual of physical therapy. Churchill Livingstone Inc. ISBN 0-443-08499-8
^ http://www.medstudents.com.br/neuroc/neuroc4.htm
^ Carol Mattson Porth. Pathophysiology: concepts of altered health states. Publisher: Lippincott. Third Edition. ISBN 0-397-54723-4
^ http://medchrome.com/basic-science/pathology/electromyography/
^ http://medchrome.com/basic-science/pathology/electromyography/
^ Otto D. Payton & Richard P. Di Fabio et al. Manual of physical therapy. Churchill Livingstone Inc. Page 24. ISBN 0-443-08499-8

UpToDate Contents

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1. 外傷性単神経障害 traumatic mononeuropathies
2. Neonatal brachial plexus palsy
3. 頭頸部皮膚切除における解剖学的危険部位 anatomic danger zones in cutaneous surgery of the head and neck
4. バーナー（刺す痛み）：スポーツ選手の急性腕神経叢損傷 burners stingers acute brachial plexus injury in the athlete
5. 若年アスリートにおける筋骨格損傷：手術が不要な損傷に対する治療の原則の概要 musculoskeletal injury in the young athlete overview of treatment principles for nonoperative injuries

English Journal

Ankle joint mobilization reduces axonotmesis-induced neuropathic pain and glial activation in the spinal cord and enhances nerve regeneration in rats.

Martins DF, Mazzardo-Martins L, Gadotti VM, Nascimento FP, Lima DA, Speckhann B, Favretto GA, Bobinski F, Cargnin-Ferreira E, Bressan E, Dutra RC, Calixto JB, Santos AR.SourceLaboratório de Neurobiologia da Dor e Inflamação, Departamento de Ciências Fisiológicas, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Campus Universitário, Trindade, Florianópolis, SC, Brazil.
Pain.Pain.2011 Nov;152(11):2653-61. Epub 2011 Sep 8.
An important issue in physical rehabilitation is how to protect from or to reduce the effects of peripheral nerve injury. In the present study, we examined whether ankle joint mobilization (AJM) would reduce neuropathic pain and enhance motor functional recovery after nerve injury. In the axonotmesi
PMID 21906878

Morphofunctional analysis of sciatic nerve and motor performance of rats after cryotherapy with liquid nitrogen.

Saueressig F, Xavier LL, Bagatini PB, Nique PS, Dacosta JC, Gomes I, Cherubini K.SourcePostgraduate Program, Dental College, Pontifical Catholic University of Rio Grande do Sul, Porto Alegre, Brazil.
Oral surgery, oral medicine, oral pathology, oral radiology, and endodontics.Oral Surg Oral Med Oral Pathol Oral Radiol Endod.2011 Jun 17. [Epub ahead of print]
OBJECTIVE: This work evaluated sciatic nerve regeneration after cryotherapy.STUDY DESIGN: Rats underwent surgical access of the sciatic nerve and subsequent cryotherapy, crush lesion, or no manipulation. Walking-track, electroneuromyographic, and histomorphometric analyses were performed at 15, 30,
PMID 21684775

Direct current electrical stimulation of acupuncture needles for peripheral nerve regeneration: an exploratory case series.

Inoue M, Katsumi Y, Itoi M, Hojo T, Nakajima M, Ohashi S, Oi Y, Kitakoji H.SourceDepartment of Clinical Acupuncture and Moxibustion, Meiji University of Integrative Medicine, Kyoto, Japan. mo_inoue@meiji-u.ac.jp
Acupuncture in medicine : journal of the British Medical Acupuncture Society.Acupunct Med.2011 Jun;29(2):88-93. Epub 2011 Feb 28.
OBJECTIVE: To examine the therapeutic effect of a novel therapeutic method based on electroacupuncture with intermittent direct current (DCEA) and associated adverse events in patients with peripheral nerve damage and a poor clinical prognosis.METHODS: In seven older patients with peripheral nerve d
PMID 21357254

Japanese Journal

早期血腫除去術を施行された被殻出血症例の一考察

太田晴基,東山理加,木下利喜生,児嶋大介,山本洋司,中村健
日本理学療法学術大会 2009(0), B4P3084-B4P3084, 2010
… 末梢神経障害のSeddonの分類におけるAxonotmesisが優位な状態であったと推察される。 …
NAID 130004582164

他動運動訓練による末梢神経再生促進効果に関する基礎的研究:―axonotmesisとneurotmesisによる違い―

塚越卓
昭和医学会雑誌 64(5), 456-459, 2004
… 復が期待できるaxonotmesisモデルを用いた他動運動訓練による神経再生促進効果について基礎的研究をおこなった.Wistar系ラット25匹をneurotmesis群10匹 (訓練群=5, 自然回復群=5) , axonotmesis群10匹 (訓練群=5, 自然回復群=5) , 無処置群=5匹の5群に分けた.Neurotmesisモデルは殿部で右坐骨神経を露出し, 神経を切断後, 顕微鏡下に8-0ナイロン糸にて神経上膜縫合を施行した.Axonotmesisモデルは露出し …
NAID 130001819181

ラット茸状乳頭の形態分化ならびに形態維持におよぼす脱神経の影響

松本光治郎
福岡歯科大学学会雑誌 24(2), 147-165, 1997-06-30
… To elucidate the trophic function of chorda tympani-lingual nerve during postnatal differentiation of rat fungiform papilla, unilateral neurectomy, nerve transection or nerve crush (axonotmesis) were performed at day 1 and at weeks 1,2,3,4 and 7 after birth. …
NAID 110004000746