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entrapment neuropathies at elbow

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ContentsDefinitionEtiologyPathophysiologyDiagnostic evaluationDifferential diagnosisManagementSpecific Entrapment neuropathies


It is a neuropathy due to a structural abnormality, such as compression, displacement, or traction of the nerve, or by an intrinsic abnormality of the nerve, such as nerve cell tumor

Withtheselesions,stretchingandangulationof thenervemaybeasimportantasource ofinjuryascompression




ETIOLOGYTrauma, direct pressure and space-occupying lesions at any level in the upper extremity

There are other situations that are not a direct cause of nerve compression, but may increase the risk and may predispose the nerve to be compressed specially when the soft tissues are swollen like synovitis, pregnancy, hypothyroidism, diabetes or alcoholism

RELEVANT ANATOMYPeripheral nerve

EpineuriumFascicleEndoneuriumPerineuriumArtery and Vein within the perineuriumLayers of nerve

Nerves have both axial (e.g. the median artery) and segmental vasculature (e.g. the Superior Ulnar colateral artery) all along its course 8

PATHOPHYISOLOGYAcute nerve compression

Pressures exceeding 20 mm Hg Reduced epineurial blood flow

Pressures exceeding 30 mm Hg Inhibits anterior and retrograde axonal transport

Pressures exceeding 80 mm Hg Cessation of intraneurial blood flow

These changes are transitory Reversible in short term

Example is Tourniquet palsy

The histopathology of chronic nerve compression follows a continuum that parallels patient sensory complaints, which progress from intermittent paraesthesia to constant numbness. Motor complaints progress from aching to weakness to atrophy

HISTOLOGY: neuromatous enlargement just above the retinaculum with an abrupt reduction in size in the tunnel, distal to which the nerve regained its normal dimensions. The nerve bundles beneath the retinaculum were thinned with an increase in the endoneurium which had destroyed the myelin sheaths

The swelling showed a considerable increase in both the epineurial and intrafunicular connective tissue though the great bulk of the swelling was due to the formerComplete recovery of function after surgical decompression reflects remyelination of the injured nerveIncomplete recovery in more chronic and severe cases of entrapment is due to Wallerian degeneration of the axons and permanent fibrotic changes in the neuromuscular junction that may prevent full reinnervation and restoration of function



Blood Nerve Barrier

BloodNerve barrierThe inner layers of the perineurium and the endothelial cells of the endoneurial microvessels create the bloodnerve barrier These cells have tight junctions that are impermeable to many substancesThus, the bloodnerve barrier provides a privileged environment within the endoneurial spaceThere are no lymphatic vessels within the endoneurial or perineurial spaces



Repetitive stress, prolonged compression

Wallerian degeneration

Localized demyelinationDemyelination of nerve fibres

As the duration of compression increases beyond several hours, more diffuse demyelination will appear, being the last event in injury to the axons themselvesThis process begins at the distal end of compression or injury, a process termed wallerian degeneration. These neural changes may not appear at a uniform fashion among the whole neural sheath depending on the distribution of the compressive forces, causing mixed demyelinating and axonal injury resulting from a combination of mechanical distortion of the nerve, ischemic injury, and impaired axonal flow


Double Crush Syndrome

DOUBLE CRUSH AND MULTIPLE CRUSH SYNDROMES A proximal level of nerve compression could cause more distal sites to be susceptible to compression

The summation of compression along the nerve would result in alterations of axoplasmic flow and subsequent pathology and symptomatology

The possibility of a distal site of compression making the more proximal nerve susceptible to secondary compression: A reverse double crush

Systemic diseases such as obesity, diabetes, thyroid disease, alcoholism, rheumatoid arthritis and neuropatthies lower the threshold for the occurrence of a nerve compression and alter axoplasmic transport rendering that nerve more susceptible to develop compression neuropathy and act as a crush

Multiple and double crush syndromeThey noted a high incidence of carpal and cubital tunnel syndrome with associated cervical root injuriesThis concept of double or multiple crush is important clinically in patients who demonstrate multiple levels of nerve compression, as failure to diagnose and treat these multiple levels of injury will result in failure to relieve patients symptoms. Systemic conditions such as obesity, diabetes, thyroid disease, alcoholism, rheumatoid arthritis and other neuropathies will similarly render a given individual more susceptible to the development of CTS and other compressions.


Entrapment Neuropathy in Diabetes DM is a significant predisposing factor for entrapment neuropathiesTN-C(Tenascin-C) expression in the endoneurium is closely correlated with nerve function Metabolic and phenotypic abnormalities of endoneurial and perineurial fibroblasts lies behind the vulnerability of DM patients to entrapment neuropathy

In contrast to angiopathies, retinopathy, and nephropathy, three representative complications of DM, mast cells do not play significant roles in the onset or progression of the entrapment neuropathy associated with DM

Ref: Histol Histopathol (2008) 23: 157-166 http://www.hh.um.es

CLINICAL SCENARIOTemporal sequence

Irritative orinflammatory pain

Paraesthesia (Tingling , Burning)

Ablative NumbnessWeakness and atrophy

Dry, thin, hairless skin

Ridged, thickened, cracked nails

Recurrent skin ulcerations

In a major mixed nerve (both sensory and motor), such as the sciatic or median nerves, signs of sympathetically mediated features may be prominent in chronic cases These changes manifest as the following

Dry, thin, hairless skinRidged, thickened, cracked nailsRecurrent skin ulcerations

Exceptions: Deep branch of the ulnar nerve at Guyon canal and PIN (both predominantly motor) and the lateral femoral cutaneous nerve (LFCN; pure sensory) near the anterior superior iliac spine (ASIS)


Clinical evaluation History Electro diagnosis: mainstayNerve Conduction studies(NCS)Electromyography(EMG)

Electromyography (EMG)EMG tests detect abnormal electrical activity in motor neuropathy and can help differentiate between muscle and nerve disorders

The electromyography detects the voluntary or spontaneous generated electrical activity. The registry of this activity is made through the needle insertion, at rest and during muscular activity to assess duration, amplitude, configuration and recruitment after injury. Recruitment will be affected if demyelination occurs, but will not result in abnormal spontaneous activity. Meanwhile, axonal injury will result in both recruitment and abnormal spontaneous activity, which will not be seen on needle electromyography until 2 weeks after the initial insult


ELECTRODIAGNOSISSensory nerve conduction studies are the earliest to show abnormality of slowing (focal demyelination) in the nerve across the site of the entrapment

Slow transmission rates and impulse blockage tend to indicate damage to the myelin sheath, while a reduction in the strength of impulses at normal speeds is a sign of axonal degeneration

Motor conduction abnormalities generally present later with slowing across the site followed by loss of axons (both sensory and motor) if the entrapment is unrelievedNeedle electromyography is used to detect axon loss which is chronic unless there is a super added acute external pressure on an existing entrapped nerve

Nerve conduction assesses for both sensory and motor nerves. This study consists in applying a voltage simulator to the skin over different points of the nerve in order to record the muscular action potential, analyzing the amplitude, duration, area, latency and conduction velocity. The amplitude indicates the number of available nerve fibers. Some authors consider diminished amplitude below 50% to be suggestive of compression. In such cases, we will find a normal response to distal stimulation but no response proximal to the site of entrapment. If the compression progresses, our results will be compatible with axonal degeneration with diminished amplitude of the response with relative preservation of the conduction velocity and distal latency until the remaining axons are completely damaged


Nerve biopsy Although this test can provide valuable information about the degree of nerve damage, it is an invasive procedure that is difficult to perform and may itself cause neuropathic side effects

Skin biopsy(examine nerve fibre endings) This test offers some unique advantages over NCV tests and nerve biopsy. Unlike NCV, it can reveal damage present in smaller fibres; in contrast to conventional nerve biopsy, skin biopsy is less invasive, has fewer side effects, and is easier to perform

Magnetic resonance imaging (MRI)can show muscle quality and size, detect fatty replacement of muscle tissue, and can help rule out tumors, herniated discs, or other abnormalities that may be causing the neuropathy

Ultrasound: The impact of sonography on clinical management has yet to be determined, even though upper extremity nerves are well-depicted Sonographically


Brachial plexopathy


Other central nervous system disorders, that can mimic peripheral nerve entrapment

Painful rheumatologic and orthopaedic disorders; and other psychological entities, such as somatoform and factitious disorders

TREATMENTTreat the underlying causeInfectionToxin exposureMedication related toxicityVitamin deficienciesHormonal deficienciesAutoimmune diseaseManagement of systemic diseasesEarly management of injuriesTREATMENT

Healthy lifestyleOptimal weightBalanced dietExercisingLimiting alcohol consumptionCorrecting vitamin deficiencies

Exercise can reduce cramps, improve muscle strength, and prevent muscle wasting

Inflammatory and autoimmune conditions leading to neuropathy can be controlled in several ways Immunosuppressive drugs such as prednisone, cyclosporine, or azathioprine may be beneficial. Plasmapheresis a procedure in which blood is removed, cleansed of immune system cells and antibodies, and then returned to the body can help reduce inflammation or suppress immune system activity. Large intravenously administered doses of immunoglobulins (antibodies that alter the immune system, and agents such as rituximab that target specific inflammatory cells) also can suppress abnormal immune system activity.


TREATMENTSymptom Management1. Nonsteroidal anti-inflammatory drugs (NSAIDs) for mild pain2. Antidepressants (tricyclic antidepressants such as amitriptyline or newer serotonin-norepinephrine reuptake inhibitors such as duloxetine hydrochloride or venlafaxine)3. Anticonvulsants (tricyclic antidepressants such as amitriptyline or newer serotonin-norepinephrine reuptake inhibitors such as duloxetine hydrochloride or venlafaxine)4. Antiarrythmics (Mexiletine) 5. Narcotic agents ( Tapentadol)

Neuropathic pain, or pain caused by the injury to a nerve or nerves, is often difficult to control. . The antidepressant and anticonvulsant medications modulate pain through their mechanism of action on the peripheral nerves, spinal cord, or brain and tend to be the most effective types of medications to control neuropathic pain. Tapentadol, a drug with both opioid activity and norepinephrine-reuptake inhibition activity of an antidepressant.


TREATMENT6. Topically administered medications LidocaineCapsaicinTopical agents are generally most appropriate for localized chronic pain such as herpes zoster neuralgia (shingles) pain7. TENS8. Allied medicine (Acupuncture, massage etc.)9. Orthosis10. Surgery11. Trans cranial magnetic stimulation

Surgical intervention can be considered for some types of neuropathies. Injuries to a single nerve caused by focal compression such as at the carpal tunnel of the wrist, or other entrapment neuropathies, may respond well to surgery that releases the nerve from the tissues compressing it. Some surgical procedures reduce pain by destroying the nerve; this approach is appropriate only for pain caused by a single nerve and when other forms of treatment have failed to provide relief. Peripheral neuropathies that involve more diffuse nerve damage, such as diabetic neuropathy, are not amenable to surgical intervention. Neutrophic factors23

CorticosteroidsSteroid injections (such as cortisone or prednisolone) shrink the swollen tissues and relieve pressure on the nerve

Corticosteroid injections are helpful for pregnant patients, as their symptoms often go away within 6 - 12 months after pregnancy

Most doctors limit steroid injections to about three per year, because they can cause complications, such as weakened or ruptured tendons, nerve irritation, or more widespread side effects

Low-Dose Oral Corticosteroids: A short course (1 - 2 weeks) of oral corticosteroid medicines may provide relief for some people, but the relief does not usually last.

Recent AdvancesUSG guided percutaneous injection, hydrodissection, and fenestrationAn extension of blind steroid injection with advantage of safety, accuracy of medication placement, effectiveness, non invasiveness, ease of performance and lower cost than open surgical release

REF: Vol.10,No.3,2010,Journal of Applied research

Research areas in nerve injuryMolecular factorsCLASSAGENT(S)ACTIONNeutrophic Factors andChemoattractantsCiliary Neutrophic factor (CNTF)Nerve growth factor (NGF)Insulin-like growth factors (IGFs)Brain-derived Neutrophic factor(BDNF)NT-3NT-4Promote neuronal survival andregrowthAttract and guide axon

Chemorepellent FactorsSemaphorinsNetrinsOthersSelectively repel some types ofaxons

Inhibitors of Connective TissueFormationInhibitors of fibroblastsCollagenasesOthersDecrease fibrosis at the site ofnerve injury to promote axonalregeneration

TYPES OF ENTRAPMENT NEUROPATHIESNerve involvedSite of entrapmentMedian N.(wrist) (Elbow)Ulnar N. (wrist) (Elbow)Lower trunk or medial cord of branchial plexusSuprascapular NRadial Nerve (Elbow)

Carpal tunnelBetween heads of Pronator teresAnterior Interosseous Nerve syndromeGuyons canal (Ulnar tunnel)Bicipital groove, Cubital tunnelCervical rib or band at thoracic outletSpinoglenoid notchRadial tunnelat point ofentrance into supinator muscle (arcade of Frohse)Posterior Interosseous Nerve syndrome


Median nerve in anterior elbow. Passing between two heads of Pronator teres muscle and into the forearm beneath the edge of the fibrous arch of flexor digitorum sublimis

MEDIAN NERVEPossible areas for median nerve compression proximal to the carpal tunnel:The ligament of StruthersThe bicipital bursaAnomalous arteries, and anomalous muscles (such as Gantzer's muscle, an accessory FPL muscle)

Pronator syndromeAnterior interosseous nerve syndromeThe last two remain the two most frequently referenced compression neuropathies of the median nerve in the forearm

PRONATOR SYNDROMECompression of the median nerve as it passes between the two heads of the pronator teres muscle, Bicipital aponeurosisCompression is due to hypertrophy and imbalance of regional tissuesDevelopment of fibrous tissue due to inflammatory processes from repetitive stress, decreasing range of motion and increasing stresses

Symptoms Insidious onsetNo history of traumaAching pain in the proximal, volar forearmParaesthesias radiating into the median innervated fingersWorsened by repetitive pronosupination movements and wrist flexionCarpenters, frequent computer users with a mouse, weight lifters, athletes especially yoga, golf and tennis


PRONATOR SYNDROMEDiscriminating clinically between PS and CTS:Loss of sensation over palmar cutaneous branch territoryNo Tinel's on the wristNo nocturnal disturbancePain on resisted pronation from a neutral position, especially as the elbow is extendedIf resisted contraction of the FDS to the middle finger reproduces symptoms, median nerve compression at the level of the fibrous arch between the heads of the FDS might be suspected

If symptoms are elicited by resisted flexion of the forearm in full supination, compression at the more proximal level of the lacertus fibrosus might be considered

ANTERIOR INTEROSSEOUS NERVE SYNDROMESite of compression essentially same for both Pronator syndrome(PS) and AIN

PS:Vague volar forearm pain,Median nerve parasthesias,minimum motor findings

AIN:Pure motor palsy of any or all three 1.FPL,2.FDP of index and middle fingers,3.PQ.

Surgical indications for nerve decompression include persistent symptoms for >6 months in patients with PS or for a minimum of 12 months with no signs of motor improvement in those with AIN syndrome

ANTERIOR INTEROSSEOUS NERVE SYNDROMEPain may be present in the forearm along the course of the nerveInability to make an OK sign when asked by the examiner to flex his thumb interphalangeal joint and index finger distal interphalangeal jointIn patients with mild AIN compression, subtle weakness of these muscles may be the only clinical findingSuch weakness of the FPL and index finger FDP may be uncovered by asking the patient to pinch a sheet of paper between his thumb and index finger using only the fingertips and then trying to pull the paper away

The AIN innervates the deep muscles of the forearm (FPL, FDP to the index and middle fingers, and pronator quadratus), a patient with a complete AIN palsy would present withAbsent motor function to all three of these muscles.


ANTERIOR INTEROSSEOUS NERVE SYNDROMEA patient with AIN syndrome may be unable to hold on to the sheet of paper with just his fingertips and may compensate by using a more adaptive grip in which the interphalangeal joint of the thumb and distal interphalangeal joint of the index finger remain extended

Differential diagnosisBrachial neuritisViral neuritis (ParsonageTurner syndrome)Rupture of the FPL tendon

AIN comes out radially from the median nerve while most other branches come out Ulnarward35


Anterior view of radial nerve course. PIN entrapment occurs because of prominent radial recurrent artery(RRA), medial edge of ECRB, proximal edge of S (Arcade of frohse, RN (Radial nerve), SRN (Superficial Radial Nerve)

AnatomyThe nerve begins posterior to the axillary artery and travels through the triangular space and then continues along the spiral groove of the humerus. The branches to the triceps are given off before this transition. All branches (sensory or motor) beyond the spiral groove pertain to the hand and forearm (Anconeus is the exception). The nerve travels from the posterior compartment of the arm into the anterior compartment as it penetrates the lateral intermuscular septum approximately 1012 cm proximal to the elbow. The radial nerve continues to travel distally and ultimately bifurcates into deep (PIN) and superficial (SRN) branches approximately 6.010.5 cm distal to the lateral intermuscular septum and 34 cm proximal to the leading edge of the supinator.[35,36] The PIN is a motor nerve that courses deep beneath the supinator muscle; the SRN is a sensory nerve that travels anteriorly on the undersurface of the brachioradialis and, in the distal one-third of the forearm, travels subcutaneously to provide sensation to the dorsoradial hand



Anatomy- Formed from posterior cord to emerge between long and lateral heads of triceps, spiral groove of humerus proceeding medially to laterally to emerge between brachialis and brachioradialis on lateral elbow to enter the radial tunnelOn exit from radial tunnel, the deep branch pierces the supinator and exits the posterior aspect to emerge as Posterior interosseous nerve


The PIN travels through the radial tunnel. Distally innervating the ECRB, supinator, ECU, EDC, EDM, APL, EPL, EPB, and EIP. It does not innervate the extensor carpi radialis longus (ECRL). The radial tunnel[34] is a potential space 34 finger breadths long, lying along the anterior aspect of the proximal radius through which the PIN travels. The floor of the radial tunnel is created by the capsule of the radiocapitellar joint, which continues as the deep head of the supinator muscle. 38

RADIAL NERVE ENTRAPMENTAnatomically, there are five potential sites of compression of the Radial nerve in the area of the radial tunnelFibrous bands of tissue anterior to the radiocapitellar joint between the brachialis and brachioradialisThe recurrent radial vessels that fan out across the PIN at the level of the radial neck as the so-called leash of HenryThe leading (medial proximal) edge of the extensor carpi radialis brevis (ECRB)The proximal edge of the superficial portion of the supinator, commonly referred to as the arcade of FrhseThe distal edge of the supinator muscle



Radial nerve compression can lead to either radial tunnel syndrome or posterior interosseous nerve syndrome (also called Supinator syndrome)


PIN is a branch of the radial nerve, originating in the lateral intermuscular septumPurely motor functionInnervates the supinator, extensor carpi ulnaris, extensor digitorum communis, extensor digiti minimi, abductor pollicis longus, extensor pollicis longus and brevis, and extensor indicis proprius muscles

Most common in racquet sports, bowlers, rowers, discus throwers, golfers, swimmersAll involve repetitive supination and pronationMay occur in synovitis, neoplasm etc

POSTERIOR INTEROSSEOUS NERVE SYNDROMESymptoms and signs:Inability to extend fingers and thumbECRL function intactthe wrist extends and radially deviates

Whereas patients with PIN syndrome have a loss of motor function, patients with RTS typically, present with mobile wad and lateral forearm pain without motor involvement

RADIAL TUNNEL SYNDROMESymptoms and signs:Pain distal to lateral epicondyle, tenderness over the radial tunnel along the path of PINPain worsened by extending the elbow, pronating the forearm and flexing the wristPain with resisted active supination or wrist extensionPain with active supination against resistancePain with wrist extension against resistancePain with resisted middle finger extension at the metacarpophalangeal jointNo neurological deficitPain disappears after instilling local anaesthetic at the site of entry of PIN

RADIAL TUNNEL SYNDROMEThere is no motor weaknessUnlike a case of lateral epicondylitis the pain is not on the lateral epicondyle of the humerus but slightly distal to itIt is described as being in the area of the mobile wad and radial tunnelDifferential diagnosis:Lateral epiconylitisOsteoarthritis of the radial capitellar jointImpingement of the articular branch of the radial nerveSynovitis of the radiocapitellar jointMuscle tear of the extensor carpi radialis brevis


Course of ulnar nerve from posterior view. It travels deep to the flexor carpi ulnaris muscle beneath the arcuate ligament

CUBITAL TUNNEL SYNDROMEEntrapment of the ulnar nerve is the second most common compression neuropathy in the upper extremity after CTSThe arcade of Struthers is a band of fascia that connects the medial head of the triceps with the intermuscular septum of the armThe cubital tunnel is a fibroosseous channel formed by the olecranon process laterally, the posterior cortex of the medial epicondyle medially, the elbow joint capsule and posterior bundle of the medial collateral ligament anteriorly, and the ligament of Osborne (the cubital retinaculum) posteriorly

Cubital Tunnel Syndrome

Truck drivers who lean the flexed elbow against the open window of their truckConstant cell-telephone users Baseball pitchers are also at risk because of the valgus stress that is induced in the late cocking and early acceleration phases of throwing Recurrent anteriordislocation of the ulnar nerveRisk factors for ulnar nerve dislocationinclude cubitus varus deformity, an absent or lax ligament of Osborne, a hypertrophic medial head of the triceps, or an accessory head of the triceps and the dislocation may be associated with activities that involve resisted elbow extension, such as the early acceleration phase of throwing and bench pressCUBITAL TUNNEL SYNDROME

TAKE HOME MESSAGEEntrapment neuropathies are far more common than thoughtThese syndromes are underdiagnosedEarly diagnosis can lead to faster and near complete recoveryConservative management followed by surgery in non responsive cases gives good results


Theodore T. Miller, William R. Reinus. Nerve Entrapment Syndromes of the Elbow, Forearm, and Wrist

Adams and Victors Principles of neurology

Entrapment Neuropathies John D. England, MD


Guyons canal entrapmentTypically in cyclists,weight lifters, jackhammersSymptoms may be motor or sensoryFeeling of pins and needles in the ring and little fingers, which is often noticed in the early morning This may progress to a burning pain in the wrist and hand followed by decreased sensation in the ring and little fingers The hand may become clumsy when the muscles controlled by the ulnar nerve become weak

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