1 Peripheral Nerves



10.1055/b-0039-171763

1 Peripheral Nerves



1.1 Diagnostic Approach for Peripheral Nerve Lesions (Table 1.1)

















History




  1. Symptoms (sens., weakness, atrophy)



  2. Mechanism of injury



  3. Chronological progression of symptoms



  4. Getting better/worse?



  5. Inciting events?


Examination




  1. Inspection (incl. postures)



  2. Palpation (e.g., mass lesion, subluxation)



  3. Motor examination



  4. Sensory examination (fuzzy vs. discrete borders)



  5. Reflexes (UMN vs. LMN)



  6. Provocative tests (e.g. Tinel’s sign)



  7. Other: vascular examination, passive ROM (contractions)


Diagnostic studies




  1. Electrophysiology (electromyogram [EMG], nerve conduction study [NCS])



  2. Imaging (US, CT, MRI)



1.2 Neuropathies



1.2.1 Nerve Pathologies Depending on Number and Location of Nerves Involved (Table 1.2a)































Dfn, features

Causes/specific syndromes

Mononeuropathy


One peripheral nerve involved


  • Injury/iatrogenic



  • Compression/entrapment


Polyneuropathy


Diffuse lesions of many nerves involved:




  • Distal nerves > prox nerves involved



  • Motor + sensory (incl. pain) fibers involved


  • Endocrinological diseases (DM, hypothyroidism)



  • Alcohol



  • Vitamin B12 deficiency



  • Heavy metals



  • Meds (e.g., chemotherapy)



  • Radiotherapy



  • Charcot–Marie–Tooth II (CMT II)


Mononeuritis multiplex


> 2 nerves involved in noncontiguous areas (simultaneous OR sequential)


  • Autoimmune diseases (systemic lupus erythematosus [SLE], RA, sarcoid)



  • Vasculitis (polyarteritis nodosa)


Plexopathy


Brachial OR lumbosacral plexus involved


  • Trauma



  • Brachial neuritis (Parsonage–Turner syndrome)



1.2.2 Other Classifications for Polyneuropathies (Table 1.2b)















  • Inherited vs. acquired




  • Small fiber neuropathy (e.g., DM) vs. large fiber neuropathy (AKA sensory ataxic neuropathies)




  • Neuropathies with predominantly motor deficits vs. with predominantly sensory deficits



1.2.3 Causes for Neuropathies (Table 1.2c)



























  • Hereditary (CMT disorder)




  • Traumatic (injuries, entrapment)




  • Infection (Hansen’s, AIDS, Guillain–Barré)




  • Autoimmune (sarcoidosis, polymyalgia rheumatica)




  • Ca (paraneoplastic, CTX, RTX)




  • Metabolic (hypothyroidism, DM, uremic neuropathy, amyloid)




  • Medicines, toxins (heavy metals), alcohol




  • Vitamin B12 deficiency




  • Pseudoneuropathy



1.2.4 Peripheral Neuropathy Versus Radiculopathy (Tab. 1.2d)

























Radiculopathy

Neuropathy

Sensory distribution

Fuzzy

Discrete


Muscle atrophy

No (rare)

Yes




  • Utilize patterns of innervation to differential diagnosis (DDx):




    • Sensory nerve distribution



    • Motor innervation



1.3 Peripheral Nerve Injuries



1.3.1 Basics (Table 1.3a)























Nerve anatomy

Endoneurium


Surrounds myelinated OR unmyelinated axons


Perineurium


Surrounds fascicles


Mesoneurium (AKA interfascicular epineurium)


Separates fascicles


Epineurium


Surrounds nerve



1.3.2 Regeneration (Table 1.3b)


















  • Rate


1 mm/d → 1 inch/mo



  • Signs




  • Advancing Tinel’s sign



  • Motor march phenomena (= motor reinnervation from prox. → dist.)



1.3.3 Mechs of Nerve Injury (Table 1.3c)

















  • Trauma (compression–crush, concussive, laceration, stretch)




  • Entrapment




  • Ischemic




  • Thermal, electrical, radiotherapy



1.3.4 Grading of Nerve Injuries (Table 1.3d)





















































Seddon


Sunderland


Pathology dfn


Wallerian degeneration


NCS


Spontaneous recovery


Neuropraxia


I


Intact basement membrane (physiologic rather than anatomic transection/nerve in continuity)

NO (maybe just focal demyelinating injury)

No conduction across lesion


Conduction prox. + dist. to lesion

Complete (in h/mo; ave: 6–8 wk)


Axonotmesis


II


Complete interruption of axons—myelin sheaths with intact endoneurium

YES (dist. to injr)

Block distally

Good


III


Axons + endoneurium disrupted with intact perineurium

Variable (possibility of scarring)


IV


Axons + endoneurium + perineurium disrupted with intact epineurium

Poor, neuroma formation


Neurotmesis


V


Complete transection (loss of continuity)

YES (dist. to injr)

Block distally

NO

Note: Pure grades of injury rarely exist; severity of most injury occurs along a continuum.



1.3.5 Peripheral Nerve Injury Grading Systems (Table 1.3e)

(Source: Adapted from Burnett et al. 1 )


1.3.6 Management of Peripheral Nerve Injury (Table 1.3f)














Evaluation (identify involved nerve, mech, degree of injury, time from injury)




  • Hx



  • P/E (motor, sens, reflexes, autonomous nervous system involvement, trophic changes)



  • Electrophysiology



  • Imaging


Management




  • Conservative (PT, splinting, pain meds)



  • Surgical repair:




    • Options:




      • Neurolysis



      • Primary/secondary repair ± nerve graft



      • Nerve transfer



    • Timing: rule of 3s



1.3.7 Timing of Nerve Exploration and Repair Rule of 3s (Table 1.3g)

















3 d/ASAP

Sharp clean lacerations


3 wk


  • Blunt lacerations



  • Blast injuries


3 mo

Injury in continuity: stretch, compression, etc. (Mgt: follow nerve regeneration closely by clinical examinations ± EMG, NCS) → surgical exploration and repair if no recovery after 3 mo



1.3.8 Algorithm of Timing of Nerve Surgery


2 , 3 (Table 1.3h )

(Source: Adapted from Dubuisson and Kline 2 and Chung et al. 3 )


1.3.9 Peripheral Nerve Repair: Surgical Pearls (Table 1.3i)

























  • Trim back to healthy nerve (fascicular) tissue




  • Tension-free neurorrhaphy + least possible microsutures




  • Topographic specificity (= match surface landmarks)




  • Magnification (microinstruments)




  • Cover repair with fibrin glue




  • No overriding fascicles




  • Consider use of epineurial, grouped fascicular and fascicular repairs depending on circumstances




  • Use max amount of graft (= maximal cross-sectional coverage of nerve stumps)



1.4 Brachial Plexus



1.4.1 Brachial Plexus Injuries (Table 1.4a)



1.4.2 Brachial Plexus Injuries: Trunks (Table 1.4b)



































Mech of injury

Motor deficits

Sensory deficits

UE posture

DDx



  1. Upper trunk injury (C5, C6, ±C7); Erb–Duchenne palsy; common (A)

Forcible widening of shoulder–neck angle (shoulder pushed downward vs. head stabilized/pushed upward)




  • Motorcycle accidents



  • Falls



  • Parturition/obstetric

Weakness of muscles w/ C5, C6 :




  • Infraspinatus



  • Supraspinatus



  • Deltoid



  • BB



  • Brachioradialis



  • Supinator (occ.)

Sens. loss in C5 + C6 dermatomes:




  • Lat. half of UA + forearm (FA)



  • Thumb (1st finger)

Bellhop’s/waiter’s tip position (see Table 1.10




  • Arm hangs at side adducted–internally rotated



  • Elbow extension



  • Wrist–finger flexion

Versus C5, C6 nerve root injr: brachial plexus weakness involves more muscles:




  • +Rhomboids ( by dorsal scapular n.)



  • + Serratus anterior (by long thoracic n.)



  • + Diaphragm (by phrenic n.)




  • 2. Lower brachial plexus injury (C8, T1, ±C7); Klumpke’s palsy; rare (B)


  • Forcible widening of chest wall–arm angle (traction of abducted arm)



  • Pancoast’s syndrome due to chest tumor




    • Pain along med. UA, FA



    • Motor—sens. def.



    • Horner’s S.

Weakness of muscles w/ C8, T1 :




  • Hand grip



  • Finger spreading + Horner s. (if T1 involved)

Sens. loss in C5 + C6 dermatomes:




  • Med. FA+ hand



  • 5th finger

Claw deformity:




  • FA supinations



  • Hyperextension of MCP joints



  • Flexion of IP joints



1.4.3 Brachial Plexus Injuries: Cords (Table 1.4c)



























Motor deficits

Sensory deficits



  1. Lateral cord palsy


    (C5, C6, C7; musculocutaneous n. palsy + lat. component of median n. palsy) (C)


  1. Weakness of muscles w/ MCN :




    • Weak elbow flex. (BB, brachialis, coracobrachialis)



  2. Weakness of muscles w/ lateral component of median n. (C5, C6, C7):




    • Pronator teres



    • Flexor carpi radialis (FCR)



  3. Weakness of clavicular head of pectoralis major (lat. pectoral n.)


  1. Sens. loss of MCN n.:




    • Lat. FA (lat. antebrachial cut. n.)



  2. Sens. loss of lateral component of median n.:




    • Lat. Palm



    • Finger tips 1–3




  • 2. Medial cord palsy


    (C8, T1; ulnar n. palsy + med. component of median n. palsy) (D)


  1. Weakness of muscles w/ ulnar n. :




    • Medial wrist flex. (FCU)



    • Distal IP joint flexion of fingers 4, 5 (flexor digitorum profundus [FDP])



    • Finger 5 mvts (ADM, FDM, ODM)



    • Finger add–abd (interossei)



  2. Weakness of muscles w/ medial component of median n. (C8, T1):




    • Thumb mvts (opponens pollicis, FPB, APB)



    • Prox. IP joint ext. (lumbricals 1, 2)



  3. Weakness of sternal head of pectoralis major (med. pectoral n.)


  1. Sens. loss of ulnar n.:




    • Med. hand



    • Fingers 4, 5



  2. No cut. Innervation of med. component of median n.



  3. Sens. loss of br. from med. cord:




    • Med. UA (med. brachial cut. n.)



    • Med. FA (med. antebrachial cut. n.)




  • 3. Posterior cord palsy


    (C5–C8, ±T1; radial n. palsy + axillary n. palsy) (E)


  1. Weakness of muscles w/ radial n. :




    • FA ext. (TB)



    • FA supination (supinator)



    • Wrist ext. (ECR longus–brevis, ECU)



    • Finger, thumb ext. (finger extensors)



  2. Weakness of muscles w/ axillary n. :




    • Arm abd. (deltoid)



  3. Weakness of muscles w/ from br. of post. cord:




    • Arm add. + int. rotation (upper + lower subscapular n., thoracodorsal n.)


  1. Sens. loss of radial n.:




    • Post. UA (post. brachial cut. n.)



    • Post. FA (post. antebrachial cut. n.)



    • Lower lat. UA (lower lat. brachial cut. n.)



    • Dorsolat. hand (superf. sens. radial n.)



  2. Sens. loss of axillary n.:




    • Upper lat. UA (upper lat. brachial cut. n.)



1.4.4 Dx of Preganglionic Injury (Nerve Root Avulsion) (Table 1.4d)

















Neuro def




  • Prox upper roots:




    • Phrenic palsy



    • Serratus anterior/rhomboid paralysis (scapula alata = winged scapula)



  • Horner’s syndrome (at T1 only)


EMG/NCS




  • Denervation of posterior myotomes (segmental paraspinal muscles)



  • No motor action potentials (MAPs)



  • Normal sensory nerve action potentials (SNAPs) from clinically denervated skin



  • No somatosensory evoked potentials (SSEPs)


MRI/myelography


Intraspinal nerve root(let)


Pseudomeningocele



1.4.5 Surgical Approach Based on Defining Clinical Level of Lesion (Table 1.4e)






























Approach

Location of injury

Anterior


Supraclavicular


Roots + trunks + proximal divisions


Infraclavicular


Distal divisions + cords + terminal branches


Combination of both


Potentially entire brachial plexus


Posterior


Posterior subscapularar


Roots + trunks + proximal divisions

Note: Indications for posterior subscapular approach (not commonly used): need for very proximal exposure to exiting roots, extensive scarring of anterior neck, and chest wall.



1.4.6 Supraclavicular Approach (Table 1.4f)




























  1. Skin incision




  • Starts: at jaw angle



  • Course:




    1. Along posterior border of sternocleidomastoid (SCM)



    2. At clavicle: turn laterally



    3. Along superior border of clavicle



  • End: at midpoint of clavicle




  • 2. Division of platysma muscle





  • 3. Exposure of posterior cervical triangle




  • Caution: preserve spinal accessory nerve in superior edge of incision



  • Vessels crossing the operative field can be ligated



  • SCM: SCM is detached from clavicle → retracted medially



  • Omohyoid: cut + retract (tag edges for reapproximation)




  • 4. Supraclavicular fat pad retraction


Dissect free supraclavicular fat pad → retract laterally → exposure of anterior scalene muscle




  • 5. Identification proximal brachial plexus




  1. Identify phrenic nerve on anterior surface of anterior scalene muscle



  2. Follow phrenic nerve superiorly until it joins C5 spinal nerve



  3. Identify C6 spinal nerve deep and slightly inferior to C5 (C5 + C6 form the superior trunk)



  4. Identify C7 deep and inferior to C6 (C7 forms the middle trunk)



  5. Identify the lower trunk deep and inferior to middle trunk



  6. Identify C8, T1 spinal nerves (C8 + T1 form the lower trunk)



  7. Trace trunks distally → identify divisions




  • 6. Maneuver for better exposure of proximal brachial plexus


Anterior scalene muscle division resection with protection of phrenic nerve and internal jugular vein



1.4.7 Infraclavicular Approach (Table 1.4g)


































  1. Skin incision




  • Starts: at midpoint of clavicle



  • Course: inferiorly along deltopectoral groove



  • End: anterior axillary crease




  • 2. Cephalic vein resection





  • 3. Exposure of posterior cervical triangle




  • Caution: preserve spinal accessory nerve in superior edge of incision



  • Vessels crossing the operative field can be ligated



  • SCM: SCM is detached from clavicle → retracted medially



  • Omohyoid: cut + retract (tag edges for reapproximation)




  • 4. Pectoralis minor division


Division of pectoralis minor tendon insertion to coracoid process (leave muscle cuff for reapproximation)




  • 5. Incision of clavipectoral fascia





  • 6. Identification of cords




  1. Identify lateral cord → identify musculocutaneous nerve (from lateral cord)



  2. Identify axillary artery inferomedial to lateral cord



  3. Identify posterior cord posterior to axillary artery



  4. Identify medial cord (+ its proximal sensory branches) inferomedial to axillary artery




  • 7. Retraction of clavicle for exposure of divisions proximally




  1. Detach pectoralis major from clavicle



  2. Ligate suprascapular artery/vein



  3. Resect subclavius muscle



  4. Retract clavicle




  • 8. Identification of brachial plexus terminal branches




  1. Identify reverse Greek “Σ” formation of nerves (superior/lateral → inferior/medial: musculocutaneous, median, ulnar)



  2. Identify radial and axillary nerves from posterior cord



1.4.8 Neurogenic Thoracic Outlet Syndrome (Table 1.4h)











































Involved neural structures

C8, T1 +/ lower trunk irritated at scalene triangle

Causes




  • Abnl fibrous band btw. ant. and mid. scalene m.



  • Elongated C7 transverse process/cervical rib


Sensory


Presentation




  • Dull shoulder/axilla pain (not so concerning for pt)


Examination




  • Sens. loss: med. FA + med. hand



  • Roos’ maneuver/elevated arm stress test: external arm rotation + abd. over head for 1–2 min → provocation



  • Tinel’s sign: at supraclavicular area (not always)


Motor


Presentation


Progressive hand intrinsic weakness—atrophy (median n. > ulnar n. innerv. hand intrinsics)


Posture


Forward drooping shoulders


DDx




  • R/O C8 radiculopathy:




    • No neck/radicular pain



    • C8 + T1 motor and sens. def. in thoracic outlet syndrome



  • R/O ulnar n. compression at elbow




    • Weakness of both ABP (~by median n.) + ADM/FDI (~by ulnar n.) in thoracic outlet syndrome


Dx


C-spine XR: R/O C7 bony anomalies


Treatment (Tx)


Conservative




  • Modification of activities



  • Physical therapy



  • Transcutaneous electrical nerve stimulation (TENS)



  • Pain meds (nonsteroidal anti-inflammatory diseases [NSAIDs], opiates, antiepileptics, antidepressants)



  • Nerve blocks


Surgical


Surgical exploration + decompression via anterior supraclavicular approach (± transaxillary approach)



1.4.9 Parsonage–Turner Syndrome (Table 1.4i)




































Demographics

Males>, any age

Causes


  • Unknown



  • Previous viral infection



  • Shoulder trauma/overuse



  • Surgery


Sensory

Presentation


  • Sudden marked shoulder pain → pain radiation:




    • Down along UA



    • Up to the neck



    • To the scapula



  • Better with UA add. + FA flex.



  • Sens. loss: absent/minimal during acute phase


Motor

Presentation


  • No weakness during acute phase → significant weakness occurs later after pain resolution



  • Most common muscles involved:




    • Deltoid



    • Supraspinatus, infraspinatus


DDx

MRI C-spine: R/O disk herniation


Dx

EMG/NCV (early and repeat in 6 weeks)


Management


  1. Early stage (pain):




    • Pain meds (NSAIDs, opiates, antiepileptics, antidepressants)



    • Oral steroids (controversial)



    • TENS



  2. Later stage (weakness):




    • Physical therapy (strengthening exercises, range-of-motion exercises)



    • Electrical stimulation (controversial)


Prognosis

Self-limiting (wk) → near normal in 3 y



1.5 Entrapment Neuropathies



1.5.1 Median Nerve ([C5], C6, C7, C8, T1) Sites of Compression (Table 1.5a)



1.5.2 Median Nerve Entrapment Sites: Motor and Sensory Deficits (Table 1.5b)

Legends: Joint, : mixed nerve, : motor nerve, : sensory nerve. In the table, boxes containing muscles are colored with blue shades and their deficits with gray shades. Boxes containing nerve br., which innervate skin as well as their deficit are colored green. Red boxes show possible entrapment sites.


1.5.3 Clinical Syndromes and Findings: Median Nerve Injury/Compression in Arm (Table 1.5c)





































































Location of injury/compression

Causes

Motor

Sensation

Postures/signs

Dx

Pitfalls (mimicking/substitution)

Arm


Proximal (A)




  • Trauma (usually, + concomitant neurovascular injury)



  • Saturday night palsy: hanging arm over chair and fainting



  • Honeymooners palsy: arm under someone’s neck



  • Pressure from crutch head

Examination


Weakness a :




  • FA (pronator teres): no pronation



  • Wrist (FCR): weak flexion in ulnar direction



  • Thumb (ABP, OP): no opposition, no palmar abd



  • Second, third fingers: weakness of lumbricals

Presentation


Numbness:




  • Radial two-thirds of palm



  • Volar surfaces of fingers 1–3 and radial half of 4

Benedictine sign (orator’s hand)




  1. Pt makes fist



  2. Finger flexion:




    • 1st: almost none



    • 2nd: partial



    • 3rd: weak



    • 4th, 5th: nl (see Table 1.10)




  • Pronation: brachioradialis w/ gravity (by radial n.)



  • Thumb opposition: FPB (deep head), add. pol. (both by ulnar n.)



  • Thumb abduction: FPB (deep head by ulnar n.), APL ( by radial n.)


Examination


Sensation loss: same distribution like numbness


Arm


Distal (B)

Entrapment




  • Supracondylar spur: ≈ on med. humerus, 5 cm prox. to med. epicondyle (1%)


    +



  • Ligament of Struthers: lig. between supracondylar spur and med. epicondyle


    ↓


median n. passes under this lig. (w/ brachial OR ulnar artery)

Presentation


Insidious onset of FA, hand weakness

Presentation


Deep aching pain in prox. FA (occ. worsens w/ pronation–supination)


Variable sensory loss

OK sign: (see Table 1.5g, AIN neuropathy)

Dx of spur




  • XR



  • Palpation


Examination




  • Variable weakness ± wasting in any median n. innerv muscle



  • Pronator teres may be spared

Examination


Tinel’s sign: in dist med arm


Injury


Supracondylar fractures:




  • Acute injury (esp. if displaced)



  • Delayed injury(callus formation)

Pseudo-anterior interosseous neuropathy b (often):


Isolated AIN motor loss (partial median n. injr)


+


1st, 2nd finger numbness (DDx vs. true AIN neuropathy)




a Weakness of pronator teres implies injury above elbow.


b AIN exists as separate bundle in median n. before branching off.


Note: AIN fibers + sens fibers for first and second fingers placed post in median n. at dist arm.



1.5.4 Management for Injury of Median Nerve in Arm (A, B) (Table. 1.5d)















Lesion type

Management options

Injury (A, B)




  • Management options and timing follow general rules and rule of 3s for nerve injuries



  • Indications for surgery: progressive neurological deficit, intractable pain



1.5.5 Key Surgical Steps for Median Nerve Exposure in Arm (A, B) (Table 1.5e)



















  1. Incision




  1. Starts: from axillary fold



  2. Courses: along the sulcus btw. BB and TB



  3. Ends: 4 cm above med. epicondyle incision curves laterally




  • 2. Anatomical structures encountered before median n.




  1. Med. brachial cut. n.: beware—preserve prior to opening the brachialis fascia



  2. Ulnar n.: the first nerve we might encounter is the ulnar n. (posteromed. vs. median n.) with the basilic vein




  • 3. Median n. identification




  • Dissect more lateral to ulnar n. to find the median n.



  • Median n. proximally courses laterally to brachial a. and then crosses medially



1.5.6 Clinical Syndromes and Findings: Median Nerve Entrapment in FA (Table 1.5f)















































Location of injury/compression

Causes

Motor

Sensation

FA

Entrapment

Musculotendinous compression (C)

(C1) Bicipital aponeurosis (very rare)

Presentation

Similar to compression due to ligament of Struthers

Presentation

Similar to compression due to ligament of Struthers:




  • Elbow pain radiating proximally and distally



  • Worse by resisted FA flexion


(C2) Pronator teres syndrome: compression btw. two heads of pronator teres (unknown incidence)

Examination


  • All muscles may be involved except for pronator teres



  • Weakness of flexion of 2nd, 3rd fingers (occasionally)

Presentation


  • Insidious onset of dull aching pain of proximal FA



  • Worse by repetitive pronation


Examination


  • Pronator teres tenderness



  • Hand sensation: nl



  • Tinel’s sign: at antecubital fossa


(C3) sublimis arch (arch of FDS)



Presentation


  • Similar to pronator teres syndrome



  • Worse pain by FDS contraction

Note: AIN fibers + sens fibers for first and second fingers placed post in median n. at dist arm.



1.5.7 Clinical Syndromes and Findings: Median Nerve / AIN Injury/Compression in FA (Table 1.5g)













































Location of injury/compression

Causes

Motor

Sensation

Postures/signs

Dx

DDx

FA

AIN (D)


  • Unknown



  • Trauma/fracture



  • Parsonage–Turner S.



  • Anomalous muscle +/tendons

Presentation

Weakness/clumsiness grasping objects with 1st and 2nd fingers

Presentation


  • Progressive arm/FA pain followed by weakness



  • No numbness

OK sign:




  • nl: thumb and index fingertips touch together



  • In AIN palsy: volar surfaces of thumb and index touch together


  • EMG/NCV



  • MRI: may show denervation of muscles innerv by AIN


  • Cervical spine degenerative disease



  • Brachial plexopathy



  • Parsonage–Turner syndrome



  • Pseudo-AIN



  • Spontaneous painless rupture of FDS, FPL tendons in RA pts

Examination

weakness:




  • FDP



  • PQ



  • FPL

Examination

nl

Note: AIN fibers + sens fibers for first and second fingers placed post in median n. at dist arm.



1.5.8 Management for Entrapment of Median Nerve/AIN at Distal Arm/Elbow/Proximal FA (C, D) (Table 1.5h)

























Lesion type

Management options

Entrapment (C, D)


Conservative




  • NSAIDs



  • Activities modifications (avoidance of repetitive FA supination/pronation)


Surgery


Indications

No improvement > 8–12 wk


Technique

Surgical exploration and decompression



1.5.9 Key Surgical Steps for Decompression of Median n./AIN at Distal Arm/Elbow/Proximal FA (C, D) (Table 1.5i)

























  1. Landmarks


Mark biceps tendon




  • 2. Incision




  1. Starts: 2–3 cm above med. epicondyle over the medial IM septum



  2. Courses: curves lateral just med. to BB tendon



  3. Ends: continues into FA btw. FDS and brachioradialis




  • 3. Median n. identification


Find median n. proximally btw. biceps and IM septum →follow into FA




  • 4. Division of three points of compression




  1. Lacertus aponeurosis (oblique)



  2. Deep head of pronator teres



  3. Arch of FDS (sublimis arch)



  4. Also divide any other constricting fibrous bands/collateral vessels

Note: There is a still controversy regarding conservative vs. surgical management of AIN entrapment.



1.5.10 Clinical Syndromes and Findings: Median Nerve Entrapment in Carpal Tunnel (Table 1.5j)











































Compression site

Causes

Motor

Sensation

Postures/signs

Dx

Hand (E)

Entrapment

Carpal tunnel syndrome (compression by transverse carpal lig.)


  • Systemic diseases:




    • Hypothyroidism, acromegaly, DM



    • Chronic renal dialysis



    • RA



    • Obesity



    • Vitamin B6 deficiency



    • Alcoholism



  • Pregnancy



  • Trauma



  • Space occupying lesions



  • Genetic



  • Anatomical variations



  • Repetitive wrist movements

Presentation


  • Hand clumsiness



  • Weak grip strength

Presentation


  • Aching pain and paresthesias in radial half of palm, fingers 1–3



  • Insidious onset



  • Pain wakes pt up at night



  • Relief: by shaking hand away; strike


  • Phalen’s test: forceful wrist flexion → paresthesias



  • Reverse Phalen’s test: wrist extension → paresthesias


  • NCS:




    1. Sensory studies (earliest, most sensitive):




      • ↑Latency at carpal tunnel > 3.7 ms



      • ↓Amplitude OR absent



    2. Motor studies (APB): ↑latency at carpal tunnel > 4 ms



  • EMG: DDx vs.:




    1. Other median n. entrapment sites



    2. Brachial plexus lesions



    3. C6, C7 radiculopathies


Examination


  • Thenar muscle wasting



  • Weakness:




    • Thumb opp (OP)



    • Thumb abduction (APB)



    • Thumb flexion (FPB)

Examination


  • Fingers 1–3, half of 4:




    • Hypesthesia/hyperesthesia



    • ↓Vibratory sensation



  • Thenar eminence: nl



  • Tinel’s sign: at wrist

Note: AIN fibers + sens fibers for first and second fingers placed post in median n. at dist arm.



1.5.11 Management for Entrapment of Median Nerve at Carpal Tunnel (E) (Table 1.5k)




























Lesion type

Management options

Carpal tunnel syndrome (E)


Conservative




  • NSAIDs, steroids



  • Steroid injections



  • Splint



  • Tx of underlying systematic diseases


Surgery


Indications




  • Failure of conservative measures



  • Progressive OR nonimproving sensory loss



  • Muscle atrophy/weakness



  • EMG findings of axonal loss


Technique


Surgical exploration and division of transverse carpal ligament (TCL)


Outcomes




  • Excellent results for most pts (pain/paresthesias relieved, motor improvement)



  • Surgical decompression is better for symptom relief vs. conservative Tx



  • Factors in favor of good outcome: symptoms <3y, no muscle atrophy/weakness, no OR low degree of demyelination/axonal loss

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May 11, 2020 | Posted by in NEUROSURGERY | Comments Off on 1 Peripheral Nerves

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