Rehabilitation of Peripheral Nerve Injuries in Disasters and Conflicts

Original Editors - Naomi O'Reilly

Top Contributors - Naomi O'Reilly, Tarina van der Stockt, Kim Jackson and Jess Bell      

Introduction

Peripheral nerves can sustain injury from numerous causes including traumatic thermal, chemical, or mechanical injury, inherited causes, infections, collagen or metabolic diseases (diabetes mellitus being one of the most common), exposure to endogenous or exogenous toxins; malignancies and iatrogenic causes, which manifest with neurological deficits distal to the level of the lesion. In disaster and conflict situations there can be a significant increase in the number of traumatic peripheral nerve injuries, but all of these other causes of nerve injury will continue to be seen by patients in these situations. In disaster and conflict situations patients with peripheral nerve injuries tend to present with other injuries, often complex and most frequently associated with limb fractures. In many cases these associated injuries need stabilised prior to the peripheral nerve injury being treated, which can often result in a delay in identification and treatment of the peripheral nerve injury.

Disasters including earthquakes and storms can lead to large numbers of peripheral nerve injuries, as a result of complex limb trauma and crush injuries, or those which incur deep soft tissue injuries from flying debris, while in conflict situations, peripheral nerve injuries are also associated with complex injuries as a result of explosives devices, gunshot wounds, and penetrating injuries. Primary injury to the nerve is generally a result of the same trauma that injures the bone or joint, but can also occur as a result of moving the patient or stretching, or manipulation of the limb while treating the injury, rather than by the initial force. Infection, scar, callus, or vascular complications including haematoma, arteriovenous fistula, ischemia, or aneurysm can also result in secondary injury to the nerve.

In the upper limb radial nerve injuries are most the common with 14% associated with humeral shaft fractures, 3% associated with fracture of the middle third of the humerus; 50%, with fracture of the distal third of the humerus; 7%, with supracondylar fracture of the humerus; and 7%, with dislocation of the radial head, while in shoulder dislocations it is the axillary nerve that may be injured as a result of stretch injuries, although this is rare and only occurs in about 5% of shoulder dislocations. Ulnar injuries account for 30% of patients with combined skeletal and neural injuries to the upper limb, and are generally associated with fractures of the medial humeral epicondyle, but often as a result of callus formation around the elbow. While elbow dislocations tend to result in median nerve injury in about 15% of combined skeletal and neural injuries of the upper limb, or after injury to the distal forearm of wrist. In the lower limb it is the peroneal nerve that is most commonly injured at the fibular neck, as a result of fracture of the tibia and fibula or dislocation of the knee, while the tibial nerve is injured more in distal fractures of the tibia or ankle. Lumbosacral plexus branches are injured in in less than 3% of pelvic fractures; and in 10% to 13% of posterior dislocations of the hip.

In conflict situations nerve injuries are generally distributed evenly between the upper and lower limbs, with explosions (63%) the main cause of peripheral nerve injury with 82% nerve injuries associated with open injuries, and a portion of patients presenting with injury to two or more nerves. Associated injuries included fractures (31.1%), multiple multiple peripheral nerve injuries (76.8%), vascular injury (30.4%), and traumatic brain injury (34.1%), with the lower extremity the most common site of the single most significant injury. Neurapraxia (45%) is the most common type of injury to the nerve, followed by axonotmesis (35%) and neurotmesis (20%). The ulnar, common peroneal and tibial nerves were most commonly injured, and in a large portion of these injuries was associated with a vascular injury, fracture, or both at the level of the nerve lesion, which is a small number of situation s result in amputation secondary to major tissue loss and the level of nerve damage. In conflict situations research suggests that there was no association between Sunderland Classification and time to evaluation, mechanism of injury, or nerve injured, but the Sunderland Classification was correlated with final motor and final sensory scores highlighting that those with with more severe initial injuries having worse final outcomes.

In disaster and conflict situations peripheral nerve injuries can be missed when medical or surgical team prioritise working to save limb or life, and rehabilitation professionals are often the first member of the team to identify possible nerve complications during their assessment and treatment. As such rehabilitation professionals should always ensure that every patient who has injured a limb or limb girdle should be evaluated and monitored for any possible peripheral nerve damage, in particular post surgery, manipulation, casting, and recovery from skeletal injury to detect any possible secondary neural injury. While timely referral for most peripheral nerve injuries does not always occur in disaster and conflict situations, research does suggest that a shorter time to presentation does led to improved sensory recovery. As such rehabilitation professionals involved in early rehabilitation play a key role in both identification and management of peripheral nerve injuries to ensure optimal recovery.

Peripheral Nerve Injury Overview

The peripheral nervous system is comprised of three types of cells: neuronal cells, glial cells, and stromal cells. Peripheral nerves convey signals between the spinal cord and the rest of the body. Nerves are comprised of various combinations of motor, sensory, and autonomic neurons. Efferent neurons (motor and autonomic) receive signals through their dendrites from neurons of the central nervous system, primarily using the neurotransmitter acetylcholine among others. Afferent (sensory) neurons receive their signals through their dendrites from specialized cell types, such as Paccinian corpuscles for fine sensation and others. These signals are sent to the CNS to provide sensory information to the brain and possibly interneurons in the spinal cord when a reflex response is necessary1.

A peripheral nerve injury can result in a minor injury or a fully severed nerve. Based on the type and amount of damage, nerve regeneration may or may not be possible. Peripheral nerve Injury treatment depends on the type of injury, symptoms and the amount of nerve injury sustained.

Mechanisms of Injury

Nerve injury can occur as a result of from traction/stretch, laceration, compression, or ischemia. The nerve dysfunction results primarily from the direct mechanical forces applied to it and secondarily from the vascular compromise that follows, with consequent ischemic nerve damage.

Laceration

A nerve can be lacerated or completely transected as a consequence of a traumatic injury. This is more likely to occur as a result of a penetrating injury mechanism (eg, knife wound, gunshot, flying debris), rather than a blunt injury mechanism. Laceration to the nerves may also be accidentally cut during surgery, e.g. a misplaced fixator pin cutting the peroneal nerve.

Traction / Stretch

Peripheral nerves allow for a significant degree of tension or stretch before developing internal/external structural damage, in part due to length redundancy that allows the nerve to adapt to stretching during normal movements of the limb (eg, the ulnar nerve at the elbow), allowing for stretching up to 10 percent with minimal traumatic consequences. However, when the nerve peripheral nerve is stretched beyond these limits both internal and external damage to the nerve can occurs. Rapid-stretch nerve injuries are among the most devastating lesions to peripheral nerves, often resulting in poor functional outcomes. Specific nerves are more susceptible than others to trauma from stretch due to their location and level of resting tension, including nerves around the brachial plexus, in particular the axillary nerve. Peripheral nerves may be injured by being stretched beyond its limit if a person is pulled by the limb through rubble or a narrow space after a building collapse.

Compression

External pressure can injure the nerve through compressive forces, which can either be continuously applied for hours at a time, such as occurs with compressive radial neuropathy ("Saturday Night Palsy") or following a crush injury, or repeatedly applied with cumulative effect, such as in habitual leaning on the elbow. More commonly, the nerves can be chronically compressed by abnormal neighboring structures, or while passing through fibro-osseous spaces such as with carpal tunnel syndrome or in situations with swelling such as compartment syndrome. Compression injury may occur to the nerve when a person or a limb is crushed, e.g. trapped under debris in a collapsed building, or in compartment syndrome (see Fractures chapter), e.g. compression of the radial nerve with crushed/swollen arm.

Combined Mechanisms

In disaster and conflict situations in many cases peripheral nerve injuries are a result of a combination of the above mechanisms. Vehicle-related injuries are predominantly stretch/traction injuries, although both contusion and laceration may also occur, missile-related injuries (eg, gunshot wounds) more commonly cause nerve contusions or transection, while laceration injuries occur most commonly as a result of sharp objects (eg, knife wound, gunshot, flying debris). Compression injuries often occur following building collapse or tend to relate to body positioning during anesthesia or surgeries; which are usually a result of a combination of contusion, compression and ischemia. Any injury with significant soft tissue damage that can also cause swelling may also cause subsequent compression.

Classification of Peripheral Nerve Injuries

Classification systems provides a common language for medical and rehabilitation professionals to effectively discuss nerve pathophysiology based upon the severity and extent of injury to the structural components of the peripheral nerve. There are two commonly used classification systems in use for peripheral nerve injury; the Seddon Classification developed in 1942 and the Sunderland Classification first proposed in 1990. Seddon was the first to classify nerve injuries into three categories; neurapraxia, axonotmesis, and neurotmesis, based on the presence of demyelination and the extent of damage to the axons and the connective tissues of the nerve. Sunderland later expanded on this initial classification to distinguish the extent of damage in the connective tissues. McKennon and Dellon introduced a further classification to denote combinations of Grade III-V injuries along the route of the damaged nerve, although it is not as widely accepted in use.

Table.1 Peripheral Nerve Injury Classification Systems

Seddon Classification	Sunderland Classification	Mechanism of Injury	Level of Injury	Potential for Recovery & Timeline
Neuropraxia	Grade I	Usually caused by a mild injury	Local myelin damage usually secondary to compression. The whole nerve remains structurally intact.	High likelihood for full recovery Recovery generally within 2 months of onset once compression removed but may often recover earlier within days or weeks.
Axonotmesis	Grade II	Typically occurs as a result of crush injuries, nerve stretch injuries (eg, motor vehicle accidents, falls), or percussion injuries (eg, gunshot wounds).	Axon severed Endoneurium intact	Good likelihood of full recovery but slower recovery.	Time course is significantly protracted as compared with neurapraxia. 0.5mm to 2mm per day Recovery proximal to distal from site of injury Recovery upto a maximum of two years
	Grade III		Axon discontinuity, endoneurial tube discontinuity. Perineurium and fascicular arrangement preserved	Potential for partial recovery. Surgery often required.
	Grade IV		Loss of continuity of axons, endoneurial tubes, Perineurium and fasciculi; epineurium intact	Potential for partial recovery, with less than 100% recovery. Surgery generally required.
Neurotmesis	Grade V	Most often occurs in association with severe lesions, such as sharp injuries, traction injuries, percussion, or exposure to neurotoxic substances.	Complete Nerve Transection Total physiologic disruption of entire nerve trunk	No significant regeneration or recovery occurs with such a lesion, unless surgical reanastomosis is performed. 0.5mm to 2mm per day Recovery proximal to distal from site of injury. Recovery upto a maximum of two years.

In disaster and conflict situations with traumatic peripheral nerve injuries most lesions are mixed and a single traumatic event can cause a combination of neurapraxia, axonotmesis, and neurotmesis in various degrees. As such the final prognosis and functional outcome depends on the ratio between the individual components of the injury, which may be difficult to assess clinically.

Common Peripheral Nerve Injuries

Upper Limb

Nerve	Related Injuries	Muscle Affected	Motor Function	Sensation	Test
Spinal Accessory Nerve	Fracture Atlas or Hyoid Neck Trauma	Trapezius	Elevates Pectoral Girdle Retracts Scapula Depresses Shoulder Ipsilateral side flexion of neck		Posture Scapular Winging at Rest Assess Abduction Test Hand behind back and lift hand away from back
Long Thoracic Nerve	Sudden Scapular Depression Axillary Crutch Use	Serratus Anterior	Scapula Protraction Upward Scapular Rotation		Scapular Winging with Movement
Axillary Nerve	Most common peripheral nerve injury to affect the shoulder. Fracture Shoulder Dislocation Shoulder	Deltoid Teres Minor	Abduction from 15° Shoulder Extension Shoulder Flexion External Rotation Atrophy Deltoid - Flat Shoulder	Regimental Patch	Unable to Abduct Arm to 90 degrees Unable to maintain resisted abduction at 90 degrees
Suprascapular Nerve	Shoulder Fracture Clavicular Fracture Proximal Humeral Fracture	Infraspinatus Supraspinatus	Initial 15° Abduction External Rotation Atrophy Supraspinatus and/or Infraspinatus		Infraspinatus Test Suprascapular Nerve Stretch Test
Musculocutaneous Nerve	Isolated injury to the Musculocutaneous Nerve is rare Knife wound to Axilla	Biceps Brachii Brachialis Coracobrachialis	Elbow Flexion Supination Weak or Absent Biceps Tendon Reflex Atrophy Anterior Compartment Arm	Lateral and Volar Aspect of  the Forearm	Unable to Flex Elbow
Ulnar Nerve	At risk of Injury at Medial Epicondyle, in Cubital Tunnel, or at the Wrist; Fracture Elbow Dislocation Elbow Laceration at Wrist	Forearm: Flexor Carpi Ulnaris Flexor Digitorum Profundus	High Lesion - Ulnar Paradox; Hyperextension 4th & 5th Finger at MCP Joint Paralysis 4th & 5th Finger at IP Joint; Straighter Fingers Loss Ulnar Deviation Loss of FCU Tendon on Ulna Flexion Loss Interossei Function Loss Thumb Adduction Wasting Hypothenar Eminence Wasting Interossei	Palmar Surface of 5th & ½ 4th Digit Dorsal Surface of 5th & ½ 4th Digit	Inability to cross second and third finger Poor Grasp and Release
		Hand Hypothenar Eminence; Abductor Digiti Minimi Flexor Digiti Minimi Opponens Digiti Minimi Thenar Eminence; Adductor Pollicis Short Muscles; Lumbrical 3 & 4 Dorsal Interossei Palmar Interossei Palmaris Brevis	Low Lesion - Partial Claw Hand; Hyperextension 4th & 5th Finger at MCP Joint Flexion 4th & 5th Finger at IP Joint Loss Interossei Function Loss Thumb Adduction Wasting Hypothenar Eminence Wasting Interossei		Inability to cross second and third finger Poor Grasp and Release Partial Claw Hand
Radial Nerve	Humeral Fracture Elbow Fractures Elbow Wounds	Arm Triceps Brachii Anconeus             Extensor Indicis	High Lesion; Loss Elbow Extension Loss Wrist Extension Loss Hand Extension Loss Radial Deviation Atrophy Forearm	No Sensory Involvement if Posterior Interosseous Branch is Damaged Alone 1st Webspace; Dorsum Aspect Hand from 1st to ½ 4th Digit	Wrist Drop Present
		Forearm; Brachioradialis Extensor Carpi Radialis Longus Extensor Carpi Radialis Brevis Supinator Extensor Digitorum Extensor Digiti Minimi Extensor Carpi Ulnaris Abductor Pollicis Longus Extensor Pollicis Longus Extensor Pollicis Brevis	Middle & Low Lesion; Loss Wrist Extension Loss Hand Extension Loss Radial Deviation Loss Thumb Extension Atrophy Forearm
Median Nerve	Supracondylar Humeral Fractures	Forearm; Pronator Teres Flexor Carpi Radialis Palmaris Longus Flexor Digitorum Superficialis Flexor Digitorum Profundus Flexor Pollicis Longus Pronator Quadratus	High Lesion; Loss Wrist Flexion Loss of Opponens Loss of Ulnar Deviation Wasting of Thenar Eminence	Palmar Aspect 1st - ½ 4th Ring Finger	Ok Test Pinch Test
			Low Lesion; Long Flexors Unaffected Loss of Opponens Thenar Muscle Wasting
		Hand; LOAF Lumbricals 1 & 2 Opponens Pollicis Abductor Pollicis Flexor Pollicis	Carpal Tunnel; Wasting of Thenar Eminence; Weakness Abductor Pollicis Brevis Loss of Opponens

Lower Limb

Nerve	Related Injuries	Muscle Affected	Motor Function	Sensation	Test
Gluteal Nerve		Gluteus Medius	Hip Abduction		Trendelenburg Sign
Femoral Nerve	Fracture Hip Fracture Pelvis Acetabular Fracture Stab Wounds Gunshot Wounds Prolonged Pressure on nerve	Quadriceps	Flexion Hip Extension Knee	Anterior Thigh Medial Thigh Medial Leg to Hallux (Great Toe)	Difficulty straightening knee
Tibial Nerve	Dislocation Knee Fracture Tibia Fracture Fibula Laceration Injury	Popliteus Gastrocnemius Soleus Plantaris Flexor Digitorum Longus Flexor Hallucis Longus			Unable to walk on toes
Peroneal Nerve	Dislocation Knee Fracture Fibular Head	Biceps Femoris Tibialis Anterior			Unable to walk on heels

Resources

Early Rehabilitation in Conflict and Disasters, Humanity and Inclusion

Rehabilitation in Sudden Onset Disasters, Humanity and Inclusion