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FOCAL NEUROPATHIES

FOCAL NEUROPATHIES. William McKinley MD Associate Professor PM&R Virginia Commonwealth University. ETIOLOGY. Compression (any external pressure) Entrapment (anatomical compression site) Repetitive trauma/overuse Direct trauma (missile, laceration) ischemia Stretch.

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FOCAL NEUROPATHIES

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  1. FOCAL NEUROPATHIES William McKinley MD Associate Professor PM&R Virginia Commonwealth University

  2. ETIOLOGY • Compression (any external pressure) • Entrapment (anatomical compression site) • Repetitive trauma/overuse • Direct trauma (missile, laceration) • ischemia • Stretch

  3. 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

  4. 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

  5. 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

  6. 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)

  7. PM&R approach to the patient with focal neuropathy • History • PE • ?Electrodiagnosis • ?additional tests (rad, U/S, vasc studies)

  8. PHYSICAL EXAM • Inspection, palpation, Motor/Sensory, DTR, provocative tests • Tinels, phalens, pinch, froments, spurlings, SLR • Know nerve anatomy & innervations! • Know common sites of entrapment!

  9. 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

  10. DIFFERENTIAL dx • Peripheral neuropathy (DM, ETOH, uremia; drugs, toxins) • Plexopathy • Radiculopathy • “Double Crush” or “vulnerable nerve syndrome (ie: radic + focal neuropathy) • Spinal Cord Injury • Myofacial/referred pain

  11. 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”)

  12. Electrodiagnosis = NCS + NEE • Sensory (SNAP) NCS • Motor (CMAP) NCS • Proximal (“late”) NCS: (H Reflex, F Wave) • limited use in focal neuropathy • Needle EMG (NEE)

  13. 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

  14. 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)

  15. 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.

  16. Conduction Block CB & Axonal loss

  17. 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

  18. 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

  19. 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

  20. 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

  21. 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%

  22. 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 polyneuropathy • Signs: Phalens, “reverse” Phalens, Tinels, “flick” sign

  23. 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

  24. Ulnar NERVE ENTRAPMENT SYNDROMES NERVE LOCATION SYNDROME MUSCLE INVOLVED Lower trunk Thoracic 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)

  25. 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.

  26. 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

  27. 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

  28. 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)

  29. 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

  30. Radial Nerve: Fun Facts • Good prognosis in radial nerve injuries • Lead toxicity commonly affects radial nerve • Test BR muscle with forearm in “neutral” position • Superficial Radial N (sensory) given off proximal to supinator m • PIN (Post. Interosseous N.) traverses supinator thru Arcade of Froshe • Exam may reveal apperent weakness of interossei (ulnar) or thumb abduction (median)

  31. 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

  32. 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

  33. 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

  34. 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

  35. 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

  36. 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

  37. “failure is not an option”! • IOH • CYL • TTL • GTG/MDAF

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