AANS2000AANS2000AANS2000AANS2000Internet Outline of

Neurosurgery

E. R. Flotte MD, 2009

 

Please send comments and corrections to admin@flotte2.com

www.outlineofneurosurgery.com

 

Peripheral Nerve

 

 

 

 

Peripheral Nerve Anatomy

 

General References

·         Kline DG N6/00 (Nerve surgery as it is now as and it may be)

·         Audio: Insights into Peripheral Nerve Surgery - Kline DG

Nerve injury

·         Classification:

o    Seddon classification: Neuropraxia > Axonotmesis (perineurium and epineurium intact) > Neurotmesis.

o    Sunderland classification I-V.

·         Recovery:

o    Motor recovery occurs within 18mos (no limit on sensory)

o    Axons regrow an “inch per month”

o    Progression of Tinel’s sign (paresthesias on tapping) may be used to follow recovery

Treatment

·         Progressive lesions (hematoma, compartment syndrome, pseudoaneurysm) require immediate evaluation/possible surgery

·          “3 days, 3 weeks, 3 month Rule”

·         Laceration: Repair within 3 days if sharp

·         Penetrating: Repair at 3 weeks. (i.e.chainsaw)

·         GSW: 3-6 mos for GSW with complete or severe lesions-in-continuity

o    Early exploration is advocated by some

o    Exploration primarily for upper elements (lower not as successful)

o    80% are in-continuity (concussive effect)

·         Traction/Blunt :

o    Serial EMG/NCVs at 2 weeks then every 3 months, repair by 3-6mos if no improvement on EMG or clinically.

o    Repair possible for upper elements only. Most effective if patient is <50yo.

o    Also surgically explore for pain, pseudoaneurysm.

Surgical Repair

·         Priorities for motor recovery are generally: elbow flexion (biceps), shoulder abduction, wrist extension, finger flexion

·         Prep for possible nerve graft (e.g. sural)

·         Consider tourniquet (remove during intraop nerve testing). Expose normal nerve proximal & distal 1st.

·         Loupes or microscope generally used.

·         Use 10-0 nylon. Consider fibrin glue.

·         Epineurial repair is equal to fasicular repair

·         Avoid traction. Use of more than 2 sutures to approximate implies unacceptable tension

·         Postoperative usually immobilized for 3-6 weeks, then physical therapy

Techniques

·         Neuroma: Determine need for resection by palpation (firm = worse), CNAP.  

o    Nerve Action Potentials (CNAP): Stimulation applied across neuroma or blunt/stretch injury site (proximal stimulation, distal recording).

o    Kline: If conduction occurs then only perform neurolysis (others perform neurolysis and distal transfer, or no neurolysis but distal transfer only). If no conduction then perform graft or nerve transfer.

o    Others perform graft or transfer regardless of CNAP.

o    End-to-side transfer distal to neuroma has been used

·         Neurorrhaphy: end-to-end repair.

·         Neurolysis: Dissection with lysis of adhesions. If nerve is in continuity and shows evidence of regeneration by positive CNAP distally or muscle contraction in response to stimulation

·         Neurotization (nerve transfer): Used for root avulsion.

o    Avoid intervening grafts, use direct transfer when possible. Implant as close as possible to the site where function is to be restored

o    Examples: elbow flexion=intercostals-to-musculocutaneous; shoulder abduction=spinal accessory-to-suprascapular

·         Interposition nerve graft:

o    Donors: sural, medial antebrachial cutaneous, superficial radial sensory, lateral cutaneous antebrachial,  dorsal cutaneous branch of ulnar

o    Sural n.:  Runs from lateral malleolus on posterolateral aspect to popliteal fossa of leg. Sensory – harvesting causes small area of numbness on the dorsal foot, may cause neuropathic pain.  Can harvest up to 35cm of graft.

o    “Cable graft”: several smaller nerves used to repair large n.

o    Synthetic nerve guides have been approved.  Used for short segments (few cm). Usually resorbable (non-resorbable may cause late compression syndromes) Schlosshauer B N10/06

o    Vein conduits used

·         Burying into muscle: equivocal, reported to be efficacious by some

 

Complex Regional Pain Syndrome

 

 

Peripheral Nerve Sheath Tumors

·         Neurofibromas (62%), Schwannomas (38%), Malignant Peripheral Nerve Sheath Tumors

·         In schwannomas function preserved in 89% after resection

·         Present with paresthesias, pain, mass. Percussion of the mass causes paresthesias.

·         Weakness rare for benign tumors. Ganglion cyst, lipomas can cause weakness.

·         Pain, rapid growth, neurologic deficits favor MPNST

·         Some recommend MRI to rule-out tumor for all peripheral nerve problems except classic CTS or ulnar neuropathy at the elbow

·         Reviews: Kwok K ON4/07 (Operative Nuances), Russell SM ON9/07

·         Case Series: Kim DH (Kline DJ) JN2/05

·         Videos: Kwok K ON4/07, Russell SM ON9/07

 

·         Non-nerve sheath tumors include: ganglion cysts, hypertrophic neuropathy, lipomas, hemangiomas, and desmoid tumors. Metastases to nerves can also occur. See Kim DH JN2/05

 

 

Entrapment Neuropathies

·         Pain is usually at the entrapment site, not in the distribution of the affected nerve. Parasthesias more common than numbness. Clumsiness more common than discreet weakness.

·         NCV shows conduction delay across the site of entrapment

·         Tinel’s sign: pain/paresthesias reproduced on mechanically stimulating (eg tapping) the nerve.

·         Always check Tinel’s sign for suspected entrapment neuropathy and to check nerve recovery

·         Reviews: Pham K NF2/09 (Mechanisms), Cho SC CN2/15/02, Cho SC CN2/28/02

 

 

 

Upper extremity

 

Root

Clinically Relevant Gross Motor Function

C5

Shoulder abduction; ± elbow flexion

C6

Elbow flexion, pronation/supination, ± wrist extension

C7

Diffuse loss of function in the extremity without complete paralysis of a specific muscle group

C8

Finger extensors, finger flexors, wrist flexors, hand intrinsics

T1

Hand intrinsics

 

·         Thumb movements: extension = lift off table (palm down); adduction = pinch against hand; abduction = touch nose with tip of thumb

 

 

Brachial Plexus

·         Roots (myotomes & dermatomes) show considerable overlap, peripheral nerves have sharp boundaries

·         Cords:

o    Lateral = muscles to forearm and sensation of median n.

o    Medial = all median and ulnar intrinsic hand muscles

·         Suprascapular n.: Shoulder abduction (first 90º) (supraspinatus) & external rotation (infraspinatus).

o    Most often repaired by spinal accessory n. transfer.

Injuries

·         Spontaneous recovery: 40% C5/6, 18% C5-7, 5% C5-T1 (flail arm)

·         Erbs palsy: C5 & 6/upper brachial plexus, bellhops hand

o    Erb’s birth injury: Controversial whether to operate or observe. Use of CNAP controversial.

·         Klumpkes palsy: C8 & T1/lower brachial plexus, claw hand

·         Ulnar n. vs C8 root injury: Sensation: ulnar n. splits 4th digit, C8 covers entire finger. Motor: C8 root lesion causes loss of all intrinsic hand muscles (ulnar and median)

·         Pancoast tumor: Horner’s + C8/T1 loss. Consider with all lower trunk/C8 involvement. Check CXR/CT chest.

·         Winged scapula:

o    long thoracic n. or serratus anterior injury (lymph node biopsy): winging when arm extended (eg against wall)

o    spinal accessory n. injury: winging when elbow flexed (across chest). Causes inability to abduct arm due to scapular instability.

·         Axillary n. injury: Occurs after shoulder dislocation.  Impaired abduction

·         Spinal accessory n.: injured in surgery of posterior cervical triangle (lymph node biopsy). Weak trapezius – impaired shoulder abduction >90o, drooping shoulder, winging of scapula, shoulder pain. No sternocleinomastoid paralysis (trapezius only). Shoulder shrug is preserved. SAN is cephalad to great auricular n. at lateral border of SCM. (N11/03)

·         Ulnar nerve has worst prognosis for return of motor function (and intrinsic hand weakness in generally usually does not recover). (Radial n. is usually best)

·         Radial n. injured with mid-shaft humerus fractures.  Brachioradialis improves 1st.

·         Benedictine sign: impaired flexion of thumb and index finger. While making fist = median injury; while opening hand = ulnar injury

 

 

Brachial Plexus Repair

·         Priorities for functional improvement: elbow flexion, shoulder abduction, finger flexion, wrist extension, shoulder rotation

·         Distal recovery is much more difficult to achieve

·         Review: Dubisson AS (Kline) N9/02

·         See Neurosurgical Focus 5/04

Preoperative workup

·         MRI, CT-myelogram:

o    Kline feels CT-myelogram are usually necessary unless MRI is conclusive for avulsion

o    Meningocoeles around nerve root imply root avulsion.

o    Absence of a meningocoele does not rule out an avulsion

·         EMG: documents the degree and pattern of dennervation, and any signs of reinnervation

o    Kline feels that SSEPs do not add any information (citation pending)

o    SNAPs (sensory nerve action potentials) are preserved in avulsions since DRG is still connected to the nerve. Absent in distal injuries

·         CXR: to look for diaphragm elevation, Pancoast tumor, cervical rib

·         Traumatic: rule out vascular injury (pulses, MRA, angio, etc)

·         Differentiate root avulsion from postganglionic injury:

o    Horner’s syndrome (C8/T1)

o    Paralysis of serratus anterior (winged scapula) or rhomboids

o    Diaphragm paralysis on CXR (C3-5)

o    Absent Tinel sign

o    Shoulder protraction test (C5)

o    Early neuropathic pain

o    EMG shows paraspinal deinnervation (wait >3wks)

o    Normal SNAP (lost in postganglionic lesions. More sensitive than an absent SSEP),

o    MRI/CT shows meningocoele.

o    See Bertelli JA JN12/06

Root avulsion

·         Most treatment is by nerve transfer.

·         No spontaneous recovery. Grafting not yet feasible (experimental).

·         Intraoperatively some dissect the nerve root into the foramina to prove avulsion

 

Obstetrical Brachial Plexus Injury

·         Some reserve surgery for those who have not had recovery of biceps function by 3-6mos (or longer)

·         Narakas Classification

·         Narakas Group IV (total plexus injury plus Horner syndrome) who show no signs of recovery require surgical repair.

·         Mild neurapraxic injury with full recovery by 1 month are treated conservatively

·          Bain JR JN:P3/09

 

Brachial Plexus Exploration

·         Trunks at lateral border of anterior scalene. Cords at level of 1st rib.

1.     Supraclavicular approach: Supine, shoulder roll, head turned away. Incision posterior border SCM, along clavicle. Platysma divided. EJ divided. Transverse cervical a. & v. ligated only if subclavian a. patent. Clavicular head SCM detached. CN11 under SCM preserved. Omohyoid divided. Phrenic n. identified on anterior side of anterior scalene & mobilized medially. Brachial plexus runs between anterior & middle scalenes. 1-2cm of anterior scalene resected.  Thyrocervical trunk preserved if possible.

2.     Infraclavicular approach: Incision along clavicle to deltopectoral groove. Cephalic v. exposed. Clavicular head of pectoralis m. divided. Pectoralis minor detached from coracoid process. Subclavius m. detached from clavicle. Lateral cord identified. Avoid sectioning clavicle – heals poorly.

·          Reviews: Tender GC (Kline DG) ON3/08 (Operative Nuances)

·         Videos: Tender GC ON3/08

3.     Axillary approach: Extend infraclavicular incision along pectoralis to humeral insertion (may be detached). Musculocutaneous n. below pectoralis.

4.     Posterior Subscapular approach: Patient prone, arm abducted & flex, head turned contralateral. Incision between medial border of scapula & spine. Trapezius, levator scapulae & rhomboids divided. 2nd rib divided medially, 1st rib & T1 transverse process resected. Scalenus posterior & medius transected. Trunks visible.

·         Useful after anterior approach failure or for TOS

·         Reviews: Tender GC (Kline DG) ON10/05 (Operative Nuances)

·         Videos: Tender GC ON10/05

 

Neurotization (Nerve Transfer)

·         Spinal accessory n. (CN11) works best for suprascapular nerve, less for axillary or musculotaneous nn. (where interposed grafts are necessary)

·         Intercostal-musculotaneous n. restores biceps in 70%

·         Medial pectoral-musculocutaneous n. works if these branches are substantial and lower trunk is intact

·         Oberlin procedure: fascicle of ulnar n. coapted to distal musculocutaneous n. Preferred by some to restore biceps in patients presenting over 8mos after injury

·         C7: ipsilateral or contralateral (requires lengthy graft). Carries small risk of weakness.

·         Cervical plexus or C3-4 provide some weak motor function

·         Phrenic n.: Kline avoids using it.

·         Hypoglossal n. not effective per Kline

·         Lower trunk has poorer prognosis for repair and some are more conservative

Examples

·         See Belzberg AJ JN 9/04 for survey of peripheral nerve surgeons on donor choices

·         C5-T1 avulsions: Accessory-suprascapular, intercostals-musculocutaneous/axillary/median (or medial pectoral, or phrenic).

 

Thoracic Outlet Syndrome

·         Three types of TOS:

1)     Neurogenic: compression of brachial plexus with neurologic deficits (see below)

2)     Vascular: compression of brachial artery & vein. Present with pain, pallor, coolness with arm use. Overhead (arm use) fatigue. Uncommon.

3)     Disputed: chronic, ill-defined arm or shoulder pain. No deficits. Frequently triggered by traumatic event (MVA, work-injury). Controversial.

·         Neurogenic and vascular variants occasionally occur together.

·         Affects C8, T1, and/or the lower trunk:

·         Compression may be from: cervical (C7) rib (10%), enlarged C7 transverse process, fibrous band (most common) from C7 TP to the clavicle, or fibrotic scalene muscles.

·         The cervical rib elevates and stretches brachial plexus, subclavan a. & v.

·         Typical patient: young, thin female with long neck and drooping shoulders

·         Symptoms/signs:

·         May have mild aching pain of ulnar forearm/hand (66%). No neck pain.

·         Weakness in all hand muscles (ulnar and median – thenar, hypothenar, and interossei). Ulnar (not median) numbness. Hand weakness/clumsiness is prominent.

·         Atrophy (“guttering”) of the lateral thenar eminence (APB - median) is characteristic. Thenar, hypothenar, and interossei atrophy – Gilliat-Sumner hand.

·         Bilateral in 50%, but less affected side is usually subclinical

·         No reliable provocative test, but 90° abduction + external rotation has best predictive value. May have Tinel’s sign over supraclavicular fossa.

·         Adsons test: turn head back & to affected side & lose radial pulse (for vascular variant)

·         Diagnosis:

·         EMG/NCV: Low APB (median) amplitudes (ulnar amplitudes are normal or slightly low). Low ulnar sensory potentials with normal median sensory potentials. Some say unreliable.

·         Chest or (oblique) c-spine Xrays or CT to look for C7 TP, cervical rib, r/o Pancoast tumor, etc

·         DDx: Pancoast tumor, ulnar neuropathy

·         Treatment – True TOS:

·         Surgical. Medical treatment, physical therapy is not indicated for true TOS (per Kline)

§  Anterior supraclavicular approach: favored. Incision usually supraclavicular, parallel to clavicle.

§  Posterior subscapular approach: used for morbidly obesity, large cervical ribs, previous anterior surgery. See Huang JH N10/04

§  Transaxillary cervical rib resection: favored by vascular surgeons, orthopedists. Per Kline has higher complication rate, less success

·         Reviews: Huang JH N10/04 (Algorithm)

 

Acute Brachial Neuritis (Parsonage-Turner Syndrome)

·         Pain: Sudden onset of very severe pain (patient presents to ER) in shoulder girdle. Pain persists for hours or weeks then becomes dull ache.

·         Weakness: As pain subsides rapid proximal arm weakness becomes prominent (deltoid, supra/infraspinatus, biceps).

§  Weakness usually recovers (90% at 3 years), but degree and duration of recovery are variable. Sensory changes are mild. 33% bilateral.

§  Preferentially affects AIN, PIN, long thoracic, suprascapular, deltoid.  Can affect 1 muscle or multiple.

·         Occurs at any age, but peaks in 20s and 60s. Males favored 4:1. 25%

§  May follow viral illnesses or vaccinations. May occur postop, even with distant surgery.

·         No fever. WBC and ESR are normal.

·         Dx: EMG/NCV: bilateral by EMG in 50%, no paraspinal involvement, abnormal SNAP (vs root). Obtained >3 wks from onset

§  MRI brachial plexus. CXR – r/o Pancoast’s tumor.

·         Symptomatic treatment (pain meds, immobilization, PT/ROM). Steroids not proven to be effective but some use.

 

Suprascapular nerve entrapment

·         Shoulder pain with supra- and infraspinatus atrophy. Inability to abduct shoulder (supraspinatus), externally rotate (infraspinatus).

·         Diagnosis: EMG/NCV. MRI shoulder (evaluate notch, r/o rotator cuff) 

·         DDx: rotator cuff disease.

·         Treatment:

o    Conservative initially: acticity restriction, NSAIDs

o    May respond to decompression. Incision on coracoids, split trapezius. Suprascapular artery runs over the suprascapular ligament, nerve runs under in suprascapular notch.

·         Reviews: Cho SC CN2/15/02

 

 

Ulnar nerve

·         From medial cord. Penetrates intermuscular septum to posterior compartment. Runs through arcade of Struthers. Runs behind medial epicondyle in cubital tunnel, between heals of flexor carpi ulnaris, through flexor-pronator aponeurosis (ancones epitrochlears – an aberrant muscle - may constrict here), thru Guyon’s canal in wrist.

1.     Dorsal cutaneous branch (sensation to dorsum of digits 4 & 5) leaves in forearm (before Guyon’s canal).

·         Muscles: Adductor pollicis, FPB (deep), hand intrinsics; FCU, FDP3/4

·         Autonomous zone = tip of little finger

 

Ulnar Entrapment

·         Signs: Interosseous wasting. Wartenberg’s sign (abducted 5th digit); Froment’s sign (grips paper b/t thumb & fingers w/tip only – adductor policis weakness). Late clawing.

·         Cubital tunnel syndrome: Medial elbow between medial epicondyle and olecranon.  Most common.

o    Ulnar numbness, grip weakness, worse with elbow flexion (e.g. talking on phone). Affects sensation to dorsal-ulnar hand (vs Guyon’s canal – spared)

o    Elbow flexion-test: elbow flexed, wrist extended, forearm supinated. Pressure applied to ulnar n. before cubital tunnel reproduces symptoms.

o    Dx: Elbow xrays (cubital tunnel projection), EMG/NCV (may be equivocal).

o    DDx: radiculopathy, medial epicondylitis, TOS, Guyon’s canal compression

o    Treatment: Rest, NSAIDS, reversed elbow pad, splint

o    Surgical options include simple decompression, medial epicondylectomy, or transposition– controversial. RPT show similar results.

·         Exposure at elbow: 8-10cm incision at medial epicondyle. Section cubital tunnel, FCU aponeurosis, arcade of Struthers.

·         Transposition: moving ulnar n. out of ulnar fossa (b/t medial epicondyle & olecranon process) Subcutaneous, submuscular or intramuscular.

·         Submuscular transposition often used for reexploration – transposed below flexor-pronator tendon and above brachialis.

·         Reviews: Janjua R ON10/08 (Operative Nuances – Submuscular)

·         Reviews: Huang JH N11/04 (Operative Nuances), Cho SC CN2/28/02

·         Videos: Huang JH N11/04, Janjua R ON10/08 (Submuscular), CNS University of Neurosurgery

·         Arcade of Struthers: 8cm proximal to elbow, rare

·         Guyons canal: Wrist – Weakness all ulnar mm. No sensory loss - Sensory to dorsum of hand spared. No Tinels.

o    Carpenters, bicycylists

o    Exposure at wrist: Incision over ulnar artery between pisiform & hamate, followed proximally.

o    DDx: Motor, no sensory loss – unilateral = Guyons, bilateral = syrinx, ALS, anterior cord syndrome

·         Vs C8 radiculopathy: with C8 all hand muscles affected including median n. & C8 sensory loss.

·         Vs cubital tunnel syndrome: sensory to dorsum of hand spared

o    Reviews: Cho SC CN2/28/02

 

 

Median nerve

·         From lateral & medial cords. Travels with brachial a. in arm. Goes thru 2 heads of pronator teres in forearm.

1.     Gives off anterior interosseous n. (FPL, index FDP, pronator quadratus).

2.     Palmar cutaneous branch: arises 5cm proximal to wrist.

3.     Recurrent motor br. To thenar muscles arises distal end carpal tunnel.

·         May be compressed at:

·         Ligament of Struthers: Fibrous band between medial epicondyle and supracondylar prominence on humerus. In 2% of population.

·         Lacertus fibrosis: arises from biceps tendon

·         Pronator Teres

·         Carpal Tunnel: transverse carpal ligament (flexor retinaulum). Contains median n. and flexor tendons.

·         Muscles: Hand = LOAF: Lumbricals 1&2, opponens, APB, FPB (superficial); all other flexors/ pronators in forearm, palmaris longus.

·         APB (abductor pollicis brevis) = “pure median”

·         Autonomous sensory zone = tip of index finger.

·         Benedictine or papal sign: impaired flexion of thumb and index finger

·         Exploration: Incision anteromedial arm, from 8cm above elbow to forearm

Entrapment syndromes

1) Carpal tunnel

·         Median nerve compressed in carpal tunnel beneath transverse carpal ligament (TCL, aka flexor retinaculum)

·         Seen with repetitive use, amyloidosis, diabetes, acromegaly, thyroid disorders, pregnancy.

·         Symptoms: numbness/ tingling, awakens at night, shaking or cold water relieves, may have pain in 5th digit & up arm (reason unclear)

·         Thenar atrophy. Unable to abduct thumb against resistance or oppose pads of thumb & index finger.

·         Phalen’s test – prolonged wrist flexion (61% sens, 83% spec)

·         Tinel’s sign – tapping wrist produces paresthesias (74% sens, 91% spec).

·         Differential Dx: TOS (diffuse hand weakness, numbness), tenosynovitis. Also AIN, pronator teres syndromes (below)

·         Double-crush: CTS + cervical radiculopathy (esp. C6)

·         DeQuervain’s syndrome: tendonitis of APL, tenderness at base of thumb with abduction (Finkelstein’s test), associated with pregnancy. NCV normal.

·         Diagnosis:  NCV: ­ median sensory (> motor) latency. Ratio of median: ulnar conduction times of 0.4 to 0.8. Normal latency <3.7 msec sensory, <4.5msec motor. EMG usually not necessary (normal in 30%)

·         Treatment:  Wrist splint, steroid (no anesthetic) injection (ulnar to palmaris longus).

·         Best available evidence for the non-surgical treatment includes rest, splinting, local steroid injection and oral steroids. NSAIDS.

·         Steroid injection: review showed short-term response 76%, but only 6%−33% long-term relief. No trial-based evidence to support repeat injections.

·         Carpal Tunnel Release:

o    Open or endoscopic sectioning of TCL

o    Incision: ulnar side of palmaris longus tendon/ interthenar crease, distal wrist crease to mid-palm. May need to section palmar aponeurosis and palmaris brevis muscle. Vascular arch is distal. Stay ulnar.

o    Palmar cutaneous branch is superficial to TCL on radial side.

o    Recurrent motor branch usually exits distal to ligament but may pierce it. 30% arise from ulnar side (70% radial)

o    90% show improvement. Endoscopic – earlier return to work, possible higher complications

o    Infection, median n. damage, ulnar n. damage due to retraction, PCB neuroma (palmar pain – cut and cauterize)

o    Reviews: Huang JH N2/04 (Mini-Open, Operative Nuances)

o    Videos: Huang JH N2/04 (Mini-Open), CNS University of Neurosurgery

·         Reviews: Cho SC CN2/15/02

 

2) Pronator teres syndrome

·         Median n. compressed between 2 heads of pronator teres, or less commonly by Struthers ligament

·         More prominent palmar pain & numbness (median palmar cutaneous branch arises proximal to TCL). Aching forearm after use, weak grip. Not noctural.

·         FPL weak (vs median neuropathy)

·         Dx: Pain on resisted pronation. Tender to palpation over pronator. NCV not useful (episodic)

·         Cause: repeat pronation.

·         Treatment: rest forearm. Can divide deep head of pronator teres

·         Reviews: Cho SC CN2/15/02

 

3) Anterior interosseous syndrome

·         AIN braches off median n. in forearm, runs through FDS fibrous arch on interosseous membrane.

·         Mostly motor wrist/thumb/1st 2 finger flexion – has small terminal sensory branches.

·         More often involved by inflammation (e.g. Brachial Plexitis). Compression caused by forearm trauma/anomalies

·         Compression as per median nerve, + sublimis bridge (arch of FDS muscle)

·         Loss of Pronator quadratus, FPL, index FDP (thumb, index, +- middle finger long flexors). May have hand/forearm pain worse with activity. No sensory loss.

·         “Pinch sign”: Unable to form ring/”OK sign” with thumb and index fingers – distal pads touch instead. Able to make a fist (vs median n.)

·         Diagnosis: EMG may help (AIN muscles affected, median not). NCV not helpful.

·         Treatment:

·         Usually resolves with rest/splinting/NSAIDS.

·         Consider exploration after 2-3 mos if structural or traumatic, 3-6 mos if entrapment is suspected.  Sooner for severe deficits.

·         Reviews: Cho SC CN2/15/02

 

Radial nerve

·         From posterior cord. Runs around spiral groove of humerus. Divides below elbow into:

o    posterior interosseous: thru arcade of Frohse, all radial muscles in forearm & hand – extensors and supinators, APL

o    superficial branch (sensory to dorsum of thumb)

·         Muscles: triceps, brachioradialis (musculocutaneous = brachialis), extensors/ supinator, APL. If cut in forearm no motor loss, only sensory.

·         Autonomous zone = 1st web space dorsum

·         Compression in axilla: e.g. from crutches.  Weakness in triceps and all distal mm.

·         Saturday night palsy: compression of radial n. on humerus (i.e. by a park bench or operative positioning) causes complete wrist drop without triceps weakness. Observe at least 3-6mo. Brachioradialis improves 1st.

·         Supinator tunnel syndrome: (aka Radial Tunnel). At elbow. Mimics refractory tennis elbow. Forearm pain without weakness – no deficits. Managed conservatively.

·         Posterior interosseous syndrome: AKA supinator syndrome.

·         Trapped at arcade of Frohse (proximal head of supinator muscle).

·         Finger drop +- wrist drop (extension deviates to radial side - ECRL, triceps, brachioradialis spared). 

·         Sensory loss partial – all fingers.

·         Pain in proximal forearm, arm (occ. to neck), worse on resisted supination.

 

Axillary nerve

·         From posterior cord. Deltoid, teres minor. Injured with anterior shoulder dislocation.

 

 

 

Lower Extremity

Meraglia Paresthetica:

·         Lateral femoral cutaneous n. Sensory only, lateral thigh. Entrapment causes burning dysesthesias in lateral thigh

·         Dx: Local block just medial to ASIS. Electrodiagnostic studies only helpful to rule out other causes.

·         Treatment: Neurectomy more effective than decompression. Incision medial to ASIS (longitudinal or transverse), Section fascia lata over anterior border of sartorius. Section inguinal ligament.

 

Obturator n.: Adductor weakness (test supine with knee extended)

 

Femoral n.:

·         From lumbar plexus (L1-L4). Supplies iliopsoas, quadriceps; not thigh adductors (obturator). Anterior thigh numbness.

·         Injured in thigh after hernia or hip operations.

·         Affected in diabetic neuropathy.

·         Vs L4 radiculopathy, which decreases sensation in medial shin (not thigh), weak thigh adductors (+- ankle dorsiflexors) – not iliopsoas. Both cause weak quadriceps (partial in radiculopathy).

·         See JN 6/04.

 

Sciatic n.: L4-S2. Divides into Common Peroneal n. and Posterior Tibial n above knee. Hamstrings and all mm below the knees. Lesion causes flail foot. Injured with dislocated knee.

 

Common Peroneal n.:

·         Deep n.: dorsiflexion (anterior tibialis), toe extension. Superficial n.: foot evertors.

·         Lesion causes foot drop (dorsiflexion, toe extension and foot eversion weakness)

·         Ganglion cysts: resection recommended.

·         Surgical exposure: prone. S-shaped incision. See N6/04.

·         Peroneal nerve palsy: Common in surgery and hospitalization with bedrest, trauma. Compression may occur at fibular head

 

Tibial n.: plantar flexion, toe flexion, foot inversion, sensation to sole of foot. Gastrocnemius, soleus mm.

·         Tarsal tunnel syndrome: tibial n. at medial malleolus. paresthesias sole of foot – no motor loss. Tinels. NCV. 90% improved. (only 50% in reops) (N11/03)

 

Mass behind knee: popliteal artery aneurysm, Ganglion (Baker’s) cyst (cut articular branch and drain cyst), nerve sheath tumor

 

 

 

Electrophysiology

Electromyography (EMG)

·         Needle placed in muscles to record action potentials and determine injury

·         Measure:

1.     Spontaneous muscle fiber action potentials:

·         Fibrillations: invisible – seen on EMG (compare fasiculations – visible to naked eye)

·         Positive Sharp Waves: downward wave after needle insertion

o    Above two present from 2 weeks to 4 months post-injury

·         Complex repetitive (Myotonic) discharges = slight movement of needle causes repetitive discharges (dive bomber). Indicate chronic denervation (>2 mos)

·         Note insertional activity seen with needle insertion is normal

2.     Motor unit action potentials (MUAP): amplitude (voltage) and duration

·         Myopathy = ¯ Voltage, ¯ duration, no ¯ motor units or recruitment;

·         Denervation/Reinnervation = ­ duration. Early: ¯ voltage. Late (2 mos – re-innervation leads to larger motor units ): ­ voltage, fibrillations, ¯ motor units & recruitment (begins 1-2wks; earlier in axonal than myelin dz);

·         UMN injury: normal EMG, no fasiculations.

·         LMN injury: fasiculations, EMG w/fibrillation, atrophy

 

NCV

·         Sensory = SNAP (sensory nerve action potential).  Normal = 50m/s (0.5-120m/s). (“speed limit = 55”)

·         Motor = MAP or CMAP (compound motor action potential). Stimulate nerve → record muscle. Normal 40-60m/s – slightly slower than SNAP. Measure amplitude, conduction velocity, and distal motor latency (measure neuromuscular junction function)

·         Axonal injury: ¯ amplitude.

·         Demyelination: ­ latency, may ¯ velocity. Ex: Guillain-Barre syndrome, CTS.

Root evaluation

·         H-reflex: submaximal stimulation, reflex arc (sensory>motor. Monosynaptic = Achilles). Median & tibial nn. Can detect proximal radiculopathy & neuropathy – ex. S1 radiculopathy (also affected by neuropathy – ie sciatic) in 1-2d after onset. Increased latency with normal F-responses localizes disease to nerve roots.

·         F-response: supramaximal stimulation, antidromic (motor>motor).Used for median, ulnar, peroneal, tibial n. Sensitive for diffuse demyelination (ex GBS)

·         M-response: direct motor response from stimulating mixed motor-sensory nerve.

 

 

 

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Revised 6/1/09

Text Copyright 2009

 

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It is intended for personal educational use by students and residents.  It is not intended to guide clinical decision making. Accuracy and timeliness cannot be guaranteed.

Sources for figures are embedded as hyperlinks within the figures.