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NEUROMUSCULAR DISORDERS: Sports & Occupations

Sports/Occupation Abattoir Backpacking Baseball Bicycle Bodybuilding Bowling Cold exposure Dance Football Mountain climbing Musicians Running Surfing Volleyball

Occupations Abattoir: Immune Batteries: Lead Cabinet maker: Hexacarbon Copper smelting: Arsenic Demolition: Lead Dentist: Nitrous oxide Dry cleaner: Trichloroethylene Epoxy resin: Allyl chloride Farmers: Organophosphates Glass & Ceramics: Tellurium Mining: Arsenic Military: Rhabdomyolysis Painter: Hexacarbon Plastic industry: Acrylamide Rayon industry: Carbon disulfide Rubber industry: Trichloroethylene Tool use: Vibration syndrome

BASEBALL

• Ulnar nerve lesion at elbow
  • Rupture of ligaments holding nerve
  • Inflammation of collateral ligament
  • Nerve traction
  • Inflammation at entrance to cubital tunnel
  • Anomalous epitrochleoanconeus
• Median nerve
  • Pronator syndrome
    • ? Related to throwing fastball: Hypertrophy of pronator teres
    • Entrapment by fibrous bands: Pronator teres; Flexor digitorum superficialis
  • Carpal tunnel syndrome
  • Ulnar digital nerve of thumb
    • Batters
    • Traumatic neuroma
    • See: Bowler's thumb
• Suprascapular neuropathy
  • Location: Suprascapular notch underneath superior transverse scapular ligament
    • Shoulder symptoms: Weakness; Posterior pain
    • Muscle involvement: Infraspinatus & Supraspinatus
  • Location: Spinoglenoid notch; Distal
    • Overhead throwing athletes
    • Causes: Injury; Ganglion cyst
    • Muscle involvement: Isolated infraspinatus atrophy
    • No pain
• Axillary nerve ± Posterior humeral circumflex artery
  • Quadrilateral space syndrome
  • Glenoid fossa osteophyte
• "Pitcher's Arm": Asymptomatic
  • Location: Throwing arm
  • Biceps reflex: Reduced
  • Sensory nerve action potential amplitudes: Reduced
• Musculocutaneous nerve
  • Bassett's Lesion: Lateral antebrachial cutaneous nerve
• Other
  • Thoracic outlet syndrome
  • Hamstring strain
  • Radial neuropathy: Softball pitchers

• Shoulder injury
• Subclavian artery lesions

BODYBUILDERS ¹

• Entrapments:
  • Acute or subacute onset
  • May be related to strenuous training
  • Often with anabolic steroids
• Specific mononeuropathies
  • Carpal tunnel syndrome
  • Musculocutaneous
  • Long thoracic nerve
  • Medial pectoral
  • Thoracodorsal
  • Dorsoscapular
  • Suprascapular
    • Overhead-activity athletes
    • Distal inferior branch: Bodybuilders & Volleyball
  • Lateral Femoral Cutaneous (Meralgia paresthetica)
  • Femoral: Distal
• Prognosis: Improvement over time

• Abdominal rhabdomyolysis
• Electrolyte disorders:
  • K⁺: Reduced
  • PO₄: Reduced
• Tear & Trauma
• Hypertrophy

BOWLING

• Nerve: Palmar digital
• Other types of causative injuries
  • Baseball
  • Jewelers
  • Cherry pitting
  • Repetitive use
  • Finger surgery
  • Snow blowing
  • Cysts & Neoplasms
  • Mononeuritis multiplex
• Clinical
  • Sensory loss: Medial thumb
  • Pain: Local over lesion
  • Nerve: May be thickened & painful to palpation
  • Time course: Chronic
• Pathology: Perineurial fibrosis

• Clinical
  • Onset: Rapid; During bowling activity
  • Sensory loss: Medial thumb
  • Pain & Paresthesias: Medial thumb
  • Time course: Monophasic; Resolution over 2 months
• Electrophysiology
  • NCV: Reduced medial SNAP stimulating from thumb

SURFING

• Saphenous nerve: Terminal sensory branch of femoral nerve
• Clinical
  • Sensory loss: Medial leg
  • Pain: Medial leg
• NCV: Asymmetric loss of saphenous SNAP
• Other causes: Entrapment; Trauma; Intrinsic lesions; Amyloid

• Epidemiology
  • Inexperienced or 1st time surfers
  • Mean age: 25 years
  • Other possible association of similar syndrome: Parachuting
• Cause
  • Continued prone hyperextension of back
  • Spinal cord ischemia: ? Watershed zone
  • Non-traumatic
• Clinical
  • Onset
    • Rapid
    • Back pain
    • Temporal: While surfing or shortly thereafter
  • Pain: Low back
  • Weakness: Legs; Proximal & Distal
  • Sensory level: T10 to L1
  • Bladdder: Urinary retention
  • Course
    • Improvement over time in most
    • Complete recovery 50%
    • Prognosis: Related to initial severity of myelopathy
  • Syndrome similar to aortic disease-associated myelopathy
• MRI (with DWI): Lower thoracic cord lesion
  • T2 Signal change: Longitudinal; Central; Upper level T6 to T11
  • No spinal canal stenosis
• Vaascular anatomy
  • Some patients have no T12 radicular artery or artery of Adamkiewicz
• Rule out: Spine trauma

BICYCLING ⁶

• Injury frequency: Non-traumatic injuries common
• Nerve Syndromes
  • Ulnar nerve
    • Nosology: "Handlebar palsy"
    • Location: Distal; At wrist or palm
    • Frequency: 10% to 30%
  • Median nerve
    • Carpal tunnel syndrome
    • Activity: Riding on the 'hoods' (Where brake lever attaches to handlebars)
  • Sciatic nerve
  • Buttock: Ischial tuberosity pain
  • Perineum
    • Numbness: Penis
    • Erectile dysfunction
    • Mechanism: Pressure on
      • Dorsal branch of pudendal nerve
      • Perineal artery either at symphysis pubis or Alcock’s canal
• Orthopedic: Knee; Neck; Shoulder; Back; Hip; Foot

FOOTBALL

• Stinger
  • Sudden burning in arm after tackle
  • Lasts 3 to 10 seconds
  • Weakness
    • Initially lasts 1 to 2 minutes
    • May be more persistent with repeated episodes
  • ? Brachial plexopathy or radiculopathy
• Cervical spine lesion
• Hamstring strain

MOUNTAIN CLIMBING & BACKPACKING

• Backpack paralysis: Mononeuropathies
  • Brachial plexus
  • Axillary nerve
  • Suprascapular nerve
  • Accessory nerve
  • Long thoracic nerve
  • Radial nerve
• Tarsal tunnel syndrome

TENNIS

• Pain
  • Lateral epicondyle of elbow: Ground strokes, especially backhand
  • Medial elbow pain: Serving
• Cubital tunnel: Spin serve
• Posterior interosseus nerve entrapment
  • Arcade of Frohse
  • Pain with resistance to passive arm pronation or wrist flexion

RUNNING

• Neuropathy
  • Reduction in vibration threshold: Subclinical
  • Peroneal neuropathy
  • Tarsal tunnel syndrome
  • Morton's neuroma
• Muscle
  • Rhabdomyolysis: Sickle cell trait at thigh altitude
  • Compartment syndrome: Exertional
  • Hamstring strain: Especially sprinting

SKIING

• Superficial peroneal nerve
  • Branches: Medial & Intermediate Dorsal cutaneous branches
  • Clinical
    • Sensory loss: Medial dorsal foot to ankle

HOCKEY ⁷

• Asymptomatic prolonged distal latencies: Dominant & non-dominant arms
  • Axillary nerve
  • Radial nerve
• Nerve injuries
  • Axillary
  • Medial & Lateral Plantar
  • Peroneal
  • Sural

MUSICIANS, INSTRUMENTAL ⁴

• Epidemiology
  • Sex: Female 60%, except focal dystonia (Male > Female)
  • Age: Mean 4th decade
• Common complaint: Pain
• Lateralization
  • Left > Right: Strings & Brass
  • Right > Left: Keyboards & Woodwind
  • Bilateral: Most percussionists (47%); Least bowed string instruments (17%)
  • Oboists & Clarinetists: Weight-bearing thumb
• Syndromes
  • Musculoskeletal disorders: 64%
    • Regional muscle pain syndromes
    • Local disorders
      • Tendinitis
      • Ligament sprain
      • Shoulder disorders: Rotator cuff...
  • Peripheral nerve disorders: 20%
  • Focal dystonia: 8%
• Electrodiagnostic studies
  • Often normal: Especially early in course, with intermittent symptoms, regional pain syndromes
  • Useful to test for nerve entrapment

• Specific disorders
  • Tendinitis
  • Ligament sprain
  • Shoulder disorders: Rotator cuff; Shoulder impingement
• Regional muscle pain syndromes
  • "Overuse"
  • Upper limb, upper trunk & neck
  • Discomfort
    • Pain or Tenderness
    • Elicited by stretching or activating affected region against resistance
  • Distribution
    • Uni- or multifocal
    • Localized to muscle or muscle-tendon junctions
  • Symptoms: Tightness, stiffness, cramping, fatigue, swelling, numbness
  • Strength: Normal; May be limited by pain
  • Electrodiagnostic studies: Usually normal
  • Course: 50% with reduction in symptoms over years
  • Treatment: Initial rest or abstinence from offending activity; Identify technical flaws

• Thoracic outlet syndrome
  • Type: Symptomatic; Neurogenic & Non-neurogenic forms
  • Epidemiology
    • Male:Female = 1:3
    • Onset age: Mean 26 years
  • Sensory symptoms
    • Pain
    • Other: Numbness, Tingling, Burning, Swelling
    • Distribution: Forearm & Hand; Ulnar > Radial
    • No sensory loss on exam
  • No weakness
  • Provocation
    • Specific positions or activities
    • Arm Maneuvers: Hyperabduction; Abduction & extension; Downward traction with internal rotation at shoulder
  • Droopy shoulder configuration: 50%
  • Otherwise normal neurologic examination
  • Instruments: Brass, Woodwind, Strings
• Mononeuropathies
  • Ulnar neuropathy
    • Most common at elbow
    • Pain: Elbow; Ulnar arm
    • Paresthesias
    • Sensory loss: Ulnar hand & fingers
    • Weakness: Occasional; May be painless
    • Male = Female
    • Age: Mean = 39 years
    • Laterality: String, all on Left (Supporting arm); Keyboard, Left > Right
    • Other ulnar: Wrist; Forearm (trauma)
    • Instruments: Strings (Violin, Guitar);. Flute (Guyon's canal)
  • Median
    • Most common: Carpal tunnel syndrome
    • Instruments: Keyboard (Organ, Piano, Accordion); Strings (Violin, Guitar)
    • Pain: Proximal & Distal; May occur at night, especially in bow string players
    • Paresthesais
    • Laterality: Bilateral in 50%; Right common in bow string players
    • Course: 50% improve with non-operative management
    • Surgery: Open or Endoscopic; 90% cure rate
    • Other median: Trauma (66%); Anterior interosseus (? Brachial plexopathy); Pronator syndrome
  • Cervical radiculopathy
    • Especially string & keyboard players
    • Age: Mean 50 years; Range 29 to 90 years
    • Male: Female = 3:1
    • Levels: C6 > C7 > C8
  • Digital neuropathy
    • Playing related: 60%
    • Flautists: Left index finger
    • Guitarists & violinist: Radial digital branch of index finger, 2° pressure on the neck of instrument
    • Marimba player (four-mallet technique): Digital branch to middle finger
    • Percussion
  • Other
    • Radial
    • Posterior cutaneous nerve to forearm
    • Branches to lip: Brass & woodwind
      • Sensory loss ± Weakness
      • Upper or lower lip
      • Improves with change of technique
    • Posterior & Anterior interosseous: Strings (Violin)
    • Cranial neuropathy: Brass (Trumpet)

• Distribution
  • Most distal arm: Loss of control, speed, or dexterity
  • Brass & wind involve embouchure: Difficulty in tone production
• Often task specific to playing instrument
• Sex: Male > Female
• Onset: Mean in mid 30's
• Progression: Slow; Over years
• Physiology
  • Excessive motor cortical excitability with abnormal cortical sensory processing
  • ? Mediated by basal ganglia

Dance ⁴

• General
  • Lower > Upper extremity
• Joint: Foot/Ankle; Knee
• Specific nerves: Case reports
  • Femoral
  • Lateral femoral cutaneous
  • Fibular: Tarsal tunnel
  • Digital: Medial hallucal nerve

Hand-Arm Vibration Syndrome (HAVS) ³

Exposure Regular use of vibratory tools: Risk proportional to Magnitude & duration of vibration exposure Vibration frequency: Harmful frequencies 8 to 1,000 Hz Professions Lumberjacks: Chainsaw Drilling Metal working: Fettling tools Association with: Tobacco use (7x risk); Cold Clinical Onset Paresthesias, continuous or relapsing Latency: Mean 6 years; Range 1 to 17 years Sensory loss Onset: Often initial feature with pain Panmodal Arms Distribution: Distal; More diffuse than single nerve During & after exposure: Especially during night-time Pain: Wrist, Palm, or Fingers; Often worse at night Motor: Weakness; Reduced manual dexterity Vascular Raynaud's like symptoms Vibration white finger Local autonomic neuropathy Onset: Later than neurologic features Prognosis: Worse with age & smoking Joint: Dupytron's contracture (Ring finger) Associated disorders Rotator cuff tendinitis Carpal tunnel syndrome Epicondylitis Course Neurosensory symptoms: Continued More severity & white finger syndrome with continued vibration exposure Laboratory NCV Abnormal motor & sensory potentials in arms Multifocal pattern: Ulnar, Median, Radial, or Digital Multiple-site lesions in segments of nerves Lesions especially common distal to wrist Vascular pathology: Thickened walls of digital vessels; Occlusions

SUPRASCAPULAR NEUROPATHY Anatomy Roots: C5-6 Brachial plexus: Upper trunk Muscles innervated: Supraspinatus; Infraspinatus Sensory Cutaneous innervation: None Coracohumeral & Coracoacromial ligaments Subacromial bursa Acromioclavicular & Glenohumeral joint capsules Entrapment & Lesions Weakness: Arm abduction & External rotation Locations Suprascapular notch Weakness: Supraspinatus & Infraspinatus Spinoglenoid notch Ligament over notch: Male > Female Weakness: Isolated infraspinatus Painless Superior transverse scapular ligament Causes Ganglion Diagnosis: MRI or Ultrasound Location Spinoglenoid notch 75% Suprascapular notch 20% Nerve stretch: Overhead sports; Shoulder pain Repeated trauma in notch Trauma or Damage around shoulder Fractures: Scapula, Clavicle, Proximal humerus Glenohumeral dislocations Acromioclavicular (AC) joint injuries Surgery Arthroscopy Posterior shoulder approach Familial calcification of superior transverse scapular ligament Differential diagnosis 11 Rotator cuff tear Quadrilateral space syndrome Frozen shoulder Brachial plexopathy C5 root lesion Sports General: Overhead-activity athletes Backpacking Volleyball Baseball Tennis Swimming Fencing Weightlifting Skeet shooting Dancing Clinical Pain Type: Dull; Aching Location: Shoulder (Posterior & Lateral) Less & more inferior with spinoglenoid lesions Exacerbated by: Adduction of extended arm Tenderness Suprascapular notch Over infraspinatus fossa Weakness & Wasting Infraspinatus > Supraspinatus Reduced arm abduction & external rotation SSN stretch test Lateral rotate patient's head away from painful shoulder Retract neck & shoulder Pain at posterior shoulder is exacerbated Laboratory Electrodiagnostic Nerve conduction: Prolonged distal latency to infraspinatus in most EMG: Denervation in Infraspinatus > Supraspinatus MRI or ultrasound: May localize ganglion Treatment Modalities Rest Nerve decompression Outcomes Reduces pain ± Improvement in strength

Suprascapular nerve Spinoglenoid notch Suprascapular notch

AXILLARY NERVE Anatomy Origin: C5-C6 Brachial plexus: Posterior cord Innervation Motor: Deltoid; Teres minor Sensory: Skin over lateral shoulder Lesions: Weak arm abduction & external rotation Trauma: Shoulder dislocation (anterior); Humerus fracture Compression: Sleeping prone with arms over head Penetrating injury: Injection; Bullet; Rotator cuff surgery Quadrilateral (quadrangular) space syndrome Brachial neuritis

Gowers Deltoid weakness Shoulder is elevated by trapezius. Slight abduction by supraspinatus.

Quadrilateral (Quadrangular) Space Syndrome Pathology: Nerve & vessel damaged or occluded in quadrangular space Distal branch of axillary nerve ± Posterior humeral circumflex artery Clinical Age: Young adults; 22 to 35 years Pain Shoulder; Poorly localized Increased by: Abduction & external rotation of arm Tenderness Quadrilateral space Near insertion of teres minor muscle Paresthesias: Lateral shoulder; Upper posterior arm Weakness Muscles: Teres minor ± Deltoid External rotation ± Abduction of arm Dominant extremity Sports Baseball Differential diagnosis Other axillary nerve change Anterior shoulder dislocation Humeral neck fracture Brachial plexus stretch injury Shoulder injury Subclavian artery stenosis Lab EMG: Denervation of teres minor MRI Selective atrophy: Teres minor ± Deltoid muscle Tendon: Normal Subclavian arteriography Posterior humeral circumflex artery Occluded with abduction & external rotation of arm ? Non-specific: Occlusion may also occur in normals

MUSCULOCUTANEOUS NERVE

• Anatomy
  • Origin
    • Roots: C5-C7
    • Brachial plexus: Lateral cord
  • Innervation
    • Motor
      • Muscles: Biceps; Brachialis; Coracobrachialis
      • Actions: Elbow flexion
    • Sensory (Lateral antebrachial cutaneous nerve)
      • Roots: C5-C7
      • Forearm distribution: Radial side from elbow to wrist
    • Anomalous branch: To median nerve in arm
• Lesions
  • Clinical
    • Onset: Often sudden
    • Weakness: Weak elbow flexion & supination
    • Muscles: Biceps & Coracobrachialis
    • Normal strength: Spinati; Deltoids; Brachioradialis
    • Sensory loss & Dysesthesias: Throwing arm
      • Lateral antebrachial nerve territory
      • Lateral forearm
      • Not hand
    • Tendon reflex: Biceps reflex absent
  • Causes
    • Injuries
      • Direct trauma: Most common, especially proximal humerus fracture
      • Rapid extension of forearm
      • Strenuous exercise
        • Lesion between Erbs point & Axilla
        • Entrapment: Passing through coracobrachialis
      • During anesthesia
      • Shoulder dislocation
      • Rotator cuff tear: Less common than axillary & suprascapular damage
    • Brachial neuritis
  • Sport associations
    • Weightlifters
    • Baseball pitchers: Reduced biceps reflex
    • Tennis: Elbow hyper-extension
• Differential diagnosis
  • Ruptured biceps tendon
  • C6 radiculopathy
• Diagnosis: EMG
• Variant: Lateral antebrachial cutaneous nerve lesion (Basset's lesion)
  • Location
    • Elbow
    • Lesion: Lateral edge of biceps, above elbow
    • Nerve entrapped between: Biceps tendon & Brachialis muscle
  • Causes
    • Strap of heavy bag across elbow crease
    • Venipuncture
    • Throwing athletes
    • Elbow hyperextension
  • Clinical
    • Pain
      • Location: Lateral elbow
      • Worsened by: Arm pronation & extension
    • Paresthesias: Down forearm with forced pronation; During throwing movement
    • Sensory loss: Lateral distal forearm

Long Thoracic Nerve ¹²

• Anatomy
  • Roots: C5, C6, C7
  • Origin: Roots before Brachial plexus
  • Muscle: Serratus anterior
    • Motions: Scapular Abduction, Rotation & Stabilization
• Lesions: Causes & Patterns
  • Dominant side: 85%
  • Injury
    • Types: Surgical; Blunt trauma; Stretch
    • Often alone without other nerves
  • Brachial neuritis (85%)
• Clinical syndrome
  • Scapular Winging: Medial

MEDIAL PECTORAL NERVE ²

• Anatomy
  • Origin: Brachial plexus
    • Common: Medial cord
    • Other: Medial trunk
  • Innervation: Sternal portion of pectoralis major
• Causes
  • Entrapment in hypertrophied pectoralis minor muscles
  • Stretch injury
• Clinical
  • Inferior sternal portion of pectoralis major: Wasting & weakness
  • Painless
  • May be bilateral
  • Compensatory hypertrophy of other chest muscles may occur
  • ? Recovery with resting of affected region

HAMSTRING STRAIN ⁵

• Sports involved
  • Sprinting: Running; Baseball; Football; Cricket (Fast bowlers)
  • Kicking a ball
• Specific muscle activity
  • Eccentric contraction (Contracting muscle is lengthened)
  • Injury more likely when muscle is already in lengthened position
• Frequency
  • Very common
  • Reinjury rate: 34%
• Predisposition
  • Previously injured muscles: Shortened range of motion
  • Unaccustomed eccentric exercise
• Prevention
  • Eccentric exercise
    • Repetitive mild
    • Mechanism: During 1 week after exercise muscle fibers produce additional sarcomeres
  • After injury
    • Muscle stretching exercise: Increase range of motion
    • Agility & trunk stabilization exercises: Icing
• MRI of injury
  • Tendon damage: 12%
    • Proximal: Common (80%)
    • Distal: Occasional
    • Requires surgical intervention
  • Muscle injury
    • Biceps femoris: 81%
    • Semimembranosus: 14%
    • Semitendinosus rare: 5%
    • May respond to conservative management
• Also see: Hamstring weakness

NOTALGIA PARESTHETICA ⁸

• Anatomy: Posterior rami of spinal nerves T2 through T6
  • Course: Pass through multifidus spinae muscle at 90° angle course en route to epidermis
• Epidemiology
  • Females: 60% to 90%
• Genetic associations
  • Familial cases described
  • MEN2A
  • Amyloid: PLCA1
• Clinical
  • Onset ages
    • Mean: 54 to 62 years
    • Earlier: Familial syndromes
  • Symptoms: Sensory
    • Distribution
      • Interscapular, Subscapular, Dorsal Paravertebral
      • T2-T6 dorsal rami
    • Itch
    • Pain
    • Paresthesias & Tingling
    • Burning
    • Hypesthesia
    • Hypoesthesia
  • Skin (65%)
    • Hyperpigmented macule(s)
  • Treatments
    • Topical: Capsaicin; Tacrolimus; Lidocaine; Botulinum toxin; Corticosteroids
    • Oral: Analgesic medications
• Laboratory
  • EMG: Normal or Denervation
  • Measure: Calcitonin in young patients

ENVIRONMENT: COLD EXPOSURE & PAINFUL SENSORY NEUROPATHY ¹⁰

• Epidemiology: Male (95%); African (75%); Armed forces
• Precipitant
  • Non-freezing cold injury or exposures
  • Exposure to temperatures of 0 °C to 15 °C
• History: "Trench foot"
• Clinical
  • Onset: Acute
  • Paresthesias
  • Pain: Cold hypersensitivity
  • Sensory loss
    • Distal
    • Arms & Legs
    • Pan-modal: Often; Pain, Temperature & Vibration (More severe cases)
    • Symmetric
  • Skin: Pale early after injury
  • Strength: Normal
  • Course: Improvement over months to years
  • Tendon reflexes: Normal in 90%
  • Treatment: Analgesics
• Laboratory
  • Intraepidermal axons: Reduced numbers in distal leg (86%)
  • NCV: Normal large axons