FOCAL NEUROPATHIES

William McKinley MD

Associate Professor PM&R

Virginia Commonwealth University

ETIOLOGY

Compression (any external pressure)Entrapment (anatomical compression site)Repetitive trauma/overuseDirect trauma (missile, laceration)ischemiaStretch

PATHOPHYSIOLOGY:Compression vs Ischemia

Compression vs Ischemia Focal demylination vs axonal injury

Mechanical compression 30 mmHg - decreased blood flow 30-60 mmHg - block of axoplasmic transport >60 mmHg - absent blood flow

Ischemia 15-45 min causes dec conduction (neuropraxia)

• less than 60 min - reversible greater than 8 hours - not reversible

MECHANICAL COMPRESSION

Pressure will lead to: paranodal demyelination

• conduction abnormalities (slowing, conduction block) Axonal injury - wallerian degeneration

Pressure selectively affects• large Type A fibers (motor, LT, vib) > small Type C

(pain/temp)• Peripheral (sensory) >central (motor) fibers

Nerve Recovery after injury

Peripheral N’s (unlike CNS) can regenerate.Remyelination - takes up to 3 months

however myelin is thin and internodes short (slow!)

Axonal Reinnervation Collateral Sprouts from adjacent intact axons Growth cones (NGF) from axon stump - span “gap” &

travel via endo tube 1-3 mm/d (1 inch/month)• Abberant re-innervation & neuroma• Muscle atrophy irreversible begins at one year• Sensory receptors survive for many years

CLASSIFICATION OF NERVE INJURY

Seddan’s Classification Neuropraxia - local cond. “block” with

demyelination (reversible) Axonotmesis - axonal injury w/wallarian

degeneration (endoneurium intact, re-innervation possible)

Neurotmesis - complete disruption of axon and endoneurial sheath (no innervation possible)

PM&R approach to the patient with focal neuropathy

HistoryPE?Electrodiagnosis?additional tests (rad, U/S, vasc studies)

PHYSICAL EXAM

Inspection, palpation, Motor/Sensory, DTR, provocative tests Tinels, phalens, pinch, froments, spurlings,

SLR

Know nerve anatomy & innervations!Know common sites of entrapment!

HISTORY

Timing: acute vs. insidious, ? Inciting event, what…better/worse

Occupation & Handedness: association with repetitive trauma

PMH: related to diseases? (DM, CTD) Location of: paresthesias (not always

anatomically distributed), numbness, Weakness

DIFFERENTIAL dx

Peripheral neuropathy (DM, ETOH, uremia; drugs, toxins)

PlexopathyRadiculopathy“Double Crush” or “vulnerable nerve

syndrome (ie: radic + focal neuropathy)Spinal Cord InjuryMyofacial/referred pain

Electrodiagnosis (Edx):

Can assist with: localization of injury

extent of injury (mild, moderate, severe)

assessment for underlying dz (DM, hypothy) and/or concomitant issues (“double crush”)

Electrodiagnosis = NCS + NEE

Sensory (SNAP) NCSMotor (CMAP) NCSProximal (“late”) NCS: (H Reflex, F Wave)

limited use in focal neuropathy

Needle EMG (NEE)

NCS findings with Focal Demyelination

Loss of conduction prolonged latency, slow CV

Abnormal proximal (to injury) stim response - (dec amplitude) compared with distal

conduction block if normal distal (to injury) amplitude = no axonal

degeneration

NCS findings with Axonal loss

NCS amplitude (measures # of fibers) loss• Motor and sensory amplitudes can help predict degree of axon loss

(comparison: with normal, proximal vs distal & side to side)

Distal wallerian degeneration• depends on distance (injury site to muscle)

Preservation of sensory NCS for up to 10 days

preservation of motor NCS for up to 7 days (NMJ)

NEEDLE EMG (NEE)

Severe compression will cause axonal injury and lead to signs of muscle fiber injury (positive sharp waves, fibrillations). Needle EMG is helpful 3- 4 weeks post injury

Nerve fiber recruitment is assessed. “Pattern” of involvement will help localize!You can also monitor “progression or

recovery” (reinnervation) with needle EMG.

Conduction Block CB & Axonal loss

Case Example: AXONAL loss vs DEMYELINATION

Ulnar Motor NCS to ADQ muscle Rt Amplitude = 10 MV (BE), 10 MV (AE) Lt Amplitude = 5 MV (BE), 2.5MV (AE)

Thus: Abnormal Lt ulnar motor with: 50% Axonal loss, 5 vs 10 (BE) - Lt vs Rt 50% Conduction block, 2.5 vs 5 -( AE vs BE)

LT

PROXIMAL NERVE ENTRAPMENT SYNDROMES

NERVE LOCATION SYNDROME MUSCLE INVOLVED

Facial Interosseus Bell’s palsy Facial, Frontalis

Sp Accessory Neck Tumor, Surg Upper Trapezius

Long Thoracic Supraclavic Trauma, Stretch Serratus Anterior

PROXIMAL NERVE ENTRAPMENT SYNDROMES

NERVE LOCATION SYNDROME MUSCLE INVOLVED

Suprascapular Suprascp Notch Backpack palsy Supra, infraspinatus

Musculo- Pierces Corac- Overuse Biceps, Brachials

cutaneous brachial coracobr.

Axillary Axilla Hum.fx Deltoid teres min

MEDIAN NERVE ENTRAPMENT SYNDROMES

NERVE LOCATION SYNDROME MUSCLE INVOLVED

Median Lig. Struthers LOS Pro Teres Involved

Median Pro Teres M Pronator Pro Teres. Spared

Teres Syndrome

Median A.I.N Anterior FPL, FDP (I II),

Int Syn PQ

Median Carpal Tunnel Carpal Tunnel Intrinsic hand

Syndrome

Median Neuropathy

Carpal Tunnel Syndrome- most common entrapment syndrome CT encloses 9 tendons and median nerve under

transverse carpal lig. CTS site is 3-4 cms distal to wrist crease CTS bilateral in 55%

CTS: Clinical exam

Symptoms: Numbness to lateral 3 digits, weakness in flexing fingers or abducting thumb, nighttime exacerbation, trophic changes.

ddx: C6-7 radiculopathy, or polyneuropathySigns: Phalens, “reverse” Phalens, Tinels,

“flick” sign

Median Neuropathy: Fun Facts

“Hand of benedictine” - Median Neurop seen w/ finger flexion “Double Crush” Syndrome (decreased axoplasmic flow predisposes

for CTS) cervical radiculopathy and CTS Martin-Gruber anastamosis (median to ulnar crossover of ulnar fibers).

Seen 15-30%, bilat in 70% , most common M. innervated is FDI

larger amp with stim elbow (vs. wrist) initial positive deflection in CTS increased NCV in CTS

Canieu Riche Anomaly (Anastomosis between the recurrent branch of the median N. and the deep br. of the ulnar N.) “Ulnar hand “ to FPB and opponens

Ulnar NERVE ENTRAPMENT SYNDROMES

NERVE LOCATION SYNDROME MUSCLE INVOLVED

Lower trunkThoracic outlet TOS All Ulnar M’s + median motor

Ulnar Ulnar Groove Tardy Ulnar +/- FCU

Palsy

Ulnar Betw Heads of Cubital Tunnel Spares FCU

FCU Syn

Ulnar Pisaform/Hamate Guyon’s Canal Ulnar Intrins

Ulnar Palm “Walker, Bike” Motor Only (FDI, Add Poll)

Ulnar Neuropathy at elbow

2nd most common entrapment syn Ulnar N superficial in UG & Cubital tunnel Ulnar Groove (UG - behind med. epic) - Most

common site • due to pressure (leaning on elbow), repetitive

motion (F/E), subluxation (18%, prior trauma (“Tardy Ulnar Palsy”), valgus deformity

Cubital tunnel (beneath aponeurosis joining 2 heads of FCU) is 2 cm distal to UG.

Ulnar Neuropathy: clinical exam

Ddx: C8-T1 radiculopathy, lower plexus lesion (TOS), CTS

Froment’s Sign, tinel, Horners (T-1), Ulnar Claw hand - seen w finger extension

Edx of Ulnar neuropathy @elbow

assess NCV across elbow “tricky” Edx findings ulnar N is “lax” in extension, and will tighten

w/flexion, also can sublux perform NCS with Elbox flexion 70-90 deg consider SSIS (“inching”) testing across elbow

(20% drop in amp is signif) NEE - FDI & forearm m’s

Ulnar Nerve: Fun Facts

Guyon’s Canal - etiol: ganglion cyst 30%, 25% recurrent trauma, 23% acute trauma

Shea-McClean Classification

• proximal canal: Motor and sensory deficits (30%)

• distal canal : Deep motor branch only (50%)

• superficial sensory branch to 4th and 5th digits (20%)

Dorsal ulnar Cutaneous N (DUC) - given off 8-10 cm proximal to wrist (does not go thru Guyons canal)

RADIAL NERVE ENTRAPMENT SYNDROMES

NERVE LOCATION SYNDROME MUSCLE INVOLVED

Radial Axilla Crutch Palsy Includes Triceps

Radial Spiral Groove Saturday Night Spares Triceps, weak Palsy/Fx ECR, sup, BR

Posterior Acrade of Posterior ECU, but spares

Inteross Frohse Inteross N. sup, ECR, BR

(Radial) (supinator) Synd (PIN)

SupRadial Wrist “Chiralgia” Sensory only

Radial Nerve: Fun Facts

Good prognosis in radial nerve injuriesLead toxicity commonly affects radial nerveTest BR muscle with forearm in “neutral” positionSuperficial Radial N (sensory) given off proximal to

supinator mPIN (Post. Interosseous N.) traverses supinator thru

Arcade of FrosheExam may reveal apperent weakness of interossei

(ulnar) or thumb abduction (median)

LE NERVE ENTRAPMENT SYNDROMES

NERVE LOCATION SYNDROME MUSCLE INVOLVED

Illioinguinal nerve, Genitofemoral nerve, Lateral femoral cutaneous nerve

(meralgia paresthetica), sural nerve, all rarely subject to isolated lesioins

Femoral Psoas/Retroperitoneal Hip Flex/Knee Ext

Femoral Inguinal Knee ext

Saphenous Hunter’s Sensory only

Canal

Obturator Pelvis Adductors

LE NERVE ENTRAPMENT SYNDROMES

NERVE LOCATION SYNDROME MUSCLE INVOLVED

Superior Gluteal Hip Injections Glut min/med

Inferior Gluteal Injections Glut max

Sciatic Under Pyriform Pyriform Short head bicep

Syndrome

SCIATIC NERVE

Course: thru greater Sciatic Foramen, beneath pyriformus M.

20% pass “thru” pyriformis (esp. peroneal division)

Peroneal division is most commonly involved (larger, fixed at fibula)

Etiology: Pelvic, hip or SI joint fractures, stretch injury, injections (SN), vaginal delivery (OBT), retropetroneal hematoma

Stim.site between ischeal tuberosity and gr. trochanter

PERONEAL NERVE ENTRAPMENT SYNDROMES

NERVE LOCATION SYNDROME MUSCLE INVOLVED

Common Head of Fibula Dorsiflex,

Peroneal Evertors

Deep Peroneal Distal to Fib Boot Dorsiflex, Dorsal

Web Sens

Deep Per “Ant” tarsal E.D. Brevis

Tunnel

Peroneal Neuropathy

Ddx: L5 radiculopathy check ankle inversion & hamstring DTR (both abnl in

L5 radic), tib post, glu med m’s

Etiology : leg crossing, weight loss, depression, casts, ankle injuries (stretch)

SHB (short head of Biceps Femoris) - thigh pierces PL m (fibular tunnel)

then divides into sup/deep peroneal

Accessory Peroneal (20%) - lat malleolus

TIBIAL NERVE ENTRAPMENT SYNDROMES

NERVE LOCATION SYNDROME MUSCLE INVOLVED

Tibial Under Flexor Tarsal Tunnel Intrinscs

Compart

Plantar 3/4 Toe Morton’s Sens/Pain

(Digital) Neuroma

“failure is not an option”!

IOHCYLTTLGTG/MDAF