Radial nerve palsy  clinical features and diagnosis
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Radial nerve palsy clinical features and diagnosis

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PLASTIC SURGERY

PLASTIC SURGERY

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Radial nerve palsy  clinical features and diagnosis Radial nerve palsy clinical features and diagnosis Presentation Transcript

  • Radial Nerve Palsy Clinical features & Diagnosis Dr Subhakanta Mohapatra IPGME&R,Kolkata.INDIA
  • Anatomy
  • Radial Nerve • Largest branch of the brachial plexus • Arises from the posterior cord of the brachial plexus (C5–8) • Mixed nerve
  • Course of Radial Nerve (RN) in the arm • Sensory supply: In the axilla, RN lies Posterior cutaneous anterior to subscapularis, nerve of arm teres major and LD RN leaves the axilla via the triangular space • Motor supply: long head of Triceps It then comes to lie along spiral groove on posterior aspect of humeral shaft along with arteria profunda brachii • Motor: medial and lateral heads of triceps, Anconeus • Sensory: posterior cutaneous nerve of forearm, lower lateral cutaneous nerve of arm
  • RN then leaves the spiral groove by piercing the lateral intermuscular septum to enter the anterior compartment of the arm, 10-12 cm above the lateral epicondyle • Motor supply: Brachialis (lateral part), BR, ECRL Here it lies b/w brachialis and BR • Terminal branches: Posterior Interosseous Anterior to lateral epicondyle, RN Nerve (PIN) and Dorsal divides into its terminal branches or Superficial radial sensory nerve
  • Radial nerve (C5, 6, 7 , 8, T1) exiting axilla via the triangular space Triceps brachii Radial nerve in the spiral groove (posterior aspect of humeral shaft) Posterior cutaneous nerve of arm Lower lateral cutaneous nerve of arm Lateral intermuscular septum Brachialis (lateral part) ECRL (last branch of radial nerve proper) Brachioradialis (BR) Posterior cutaneous nerve of forearm Anconeus
  • Course of Radial Nerve (RN) in the forearm Dorsal digital nerves ECRL Dorsal Radial Sensory Nerve BR 8 cm Radial styloid It crosses the anatomical snuffbox b/w EPB and EPL, dividing into multiple branches to supply sensation to hand It emerges b/w tendons of BR and ECRL ≈ 8 cm proximal to radial styloid, to become subcutaneous Dorsal radial nerve courses through the forearm immediately deep to the BR
  • Radial Nerve Proper Superficial terminal branch Deep terminal branch → Posterior interosseous nerve (PIN) PIN reaches the back of forearm by passing around the lateral aspect of the radius b/w the superficial and deep heads of the Supinator to supply all extensor compartment muscles Supinator ECRB ECU EDC and EDM EIP APL Finally, PIN ends by supplying carpal joint sensation EPL EPB
  • Cutaneous innervation from radial nerve Lower lateral cutaneous nerve of arm Posterior cutaneous nerve of arm Gives sensibility to the dorsum of the hand over the radial twothirds, the dorsum of the thumb, and the index, long, and half of the ring finger proximal to the distal interphalangeal joint. Posterior cutaneous nerve of forearm Dorsal radial sensory nerve
  • Clinical Features
  • Functional motor deficit Inability to extend the wrist (in case of injury at level of PIN, wrist extension is weak with radial deviation since ECRL innervation is intact) Inability to extend and radially abduct the thumb Weakness of grip strength d/t loss of mechanical advantage that wrist extension provides for grasp and power grip Inability to extend the fingers at the MCP joints
  • Sensory Loss Unlike the median and ulnar nerves, sensory loss following radial nerve injury is not functionally disabling unless the patient develops a painful neuroma Area of sensory loss in radial nerve injury in the axilla The Lateral cutaneous nerve of forearm has a significant overlap pattern with the Superficial radial sensory nerve Autonomous sensory zone for radial nerve → dorsum of 1st webspace
  • Radial Nerve Compression Syndromes
  • Wartenberg’s syndrome • Aka: Cheiralgia paresthetica • D/t compression of Superficial radial nerve as it emerges b/w ECRL and BR, 8 cm proximal to radial styloid
  • presence of motor weakness suggests a more proximal site of compression isolated pain or paresthesias over the dorsoradial aspect of the hand preceding history of trauma to the area (i.e., handcuffs, forearm fracture) Clinical features Differentiating Wartenberg’s syndrome from de Quervain’s tenosynovitis In WS, pain is exacerbated by pronation, while in DQT pain is elicited with changes in thumb and wrist position DQT - normal sensation in the dorso-radial hand DQT - pain on percussion over the 1st extensor compartment Also seen in patients who use forearms in pronated position for extended periods → in pronation, the tendons of BR and ECRL approximate and may compress the nerve A Tinel’s sign over the superficial sensory radial nerve is the most common exam finding Electrodiagnostic testing is of limited value in Wartenberg’s syndrome
  • Posterior interosseous nerve (PIN) syndrome • D/t compression of PIN in the radial tunnel • Most common causes include: Tumors such as lipomas, ganglia Rheumatoid synovitis Septic arthritis Vasculitis
  • PIN BR arcade of Fröhse The radial tunnel is a 5 cm space bounded by: Dorsally: capsule of the radiocapitellar joint Volarly: the BR Laterally: the ECRL and ECRB muscles Medially: the biceps tendon and brachialis muscles Supinator ECRL Within radial tunnel, there are 5 potential sites of compression: fibrous bands to the radiocapitellar joint between the brachialis and BR the recurrent radial vessels (leash of Henry) the proximal edge of the ECRB the proximal edge of the Supinator (arcade of Fröhse) the distal edge of the Supinator
  • Diagnosis loss of finger and thumb extension Weak wrist extension with radial deviation (since ECRL innervation is intact) Intact passive tenodesis effect (rules out extensor tendon rupture) EMG testing is helpful to confirm the diagnosis and monitor motor recovery
  • Radial Tunnel syndrome • Similar to PIN syndrome, it is also d/t compression of PIN in the radial tunnel • Not considered a true compression neuropathy by some
  • Radial Tunnel Syndrome is a clinical diagnosis Pain at ECRB origin with resistance of middle finger extension Tenderness over radial tunnel (lateral proximal forearm, 3-4 cm distal to lateral epicondyle over the mobile wad) Pain with resisted forearm supination ↑ Pain on combined elbow extension, forearm pronation, and wrist flexion Radial Tunnel Syndrome
  • Proximal Radial nerve compression • Compression of the radial nerve proximal to the elbow is uncommon • Causes: Fibrous arch from the lateral head of triceps After strenuous muscular activity Bony exostosis of humerus Injury in spiral groove: # shaft humerus ‘Saturday night palsy’ (neuropraxia) Post injection palsy (chemical neurotmesis) • Patients present with variable degrees of radial nerve dysfunction
  • Diagnosis
  • History Mechanism of injury (e.g. sharp penetrating vs. blunt trauma) Timing of injury Loss of motor and sensory function Presence of pain Interval recovery of function in patients presenting late
  • Physical Examination Individual muscles innervated by the nerve are tested to determine what is functioning and what is not: Helps to determine the level of injury Guides future surgical planning Assessment of motor function Assessment of sensory function Elicitation of Tinel’s sign Specific sensory testing Assessment of involved joints Each joint is taken through its passive range of motion to assess for suppleness → presence of fixed joint contractures in delayed presentations is associated with poor treatment outcomes
  • Specific sensory tests Test Perception Main receptor Comments Static 2 point discrimination (2PD) Tactile Merkel cell Evaluates sensory receptor innervation density Normal distance: 6mm Moving 2PD Tactile Meissner corpuscle Tuning fork (250 Hz) Vibration Pacinian corpuscle Tuning fork (30 Hz) Vibration Meissner Semmes-Weinstein monofilament test Pressure Merkel Ten test (moving light touch) Pressure Merkel Cold-heat test Temperature Free nerve endings Normal distance: 3mm Reliability comparable to monofilament test •Changes in Vibration and Pressure thresholds are seen in early nerve compression but are unreliable for evaluating nerve lacerations •Changes in sensory receptor innervation density (2PD) are seen in chronic nerve compression but are reliable for evaluating nerve lacerations
  • Electrodiagnostic testing Electromyography (EMG) Helpful in arriving at a diagnosis in presence of atypical presentations or equivocal clinical findings Nerve conduction studies (NCS) Limitations of EDT: Evaluates only large myelinated fibres → smaller axons conveying pain and temperature are not assessed Changes in unmyelinated nerve fibres, which are the first to be affected in nerve compressions, are not evaluated Performing the test before 3-6 weeks post injury can give inaccurate results Very proximal or distal nerve injuries are difficult to assess Unreliable assessment of multilevel injuries Examiner dependant
  • Nerve conduction studies (NCS) 2 electrodes are placed along the course of the nerve. The first electrode stimulates the nerve to fire, and the second electrode records the generated action potential Amplitude • represents the size of the response • proportional to the number of depolarizing axons in the nerve Latency • the delay in response following stimulation Sensory nerve action potential (SNAP) • Response obtained when the recording electrodes is placed proximally along the sensory nerve, toward the spinal cord Conduction velocity Compound motor action potential (CMAP) • Response obtained when the recording electrodes is placed distally at the target muscle
  • Electromyography (EMG) Insertional activity Fibrillation potentials Fasciculations Motor unit potentials (MUPs) • Activity observed when a needle electrode is inserted into the muscle • Seen when the muscle is at rest • Absent in normal muscles • Generated by the muscle during a voluntary contraction • Evaluates the integrity of neuromuscular junction
  • Sequence of events in nerve compression Focal demyelination Axonal damage at the compression site Further axonal loss Axonal sprouting producing collateral re-innervation Remyelination following decompression Associated Electrodiagnostic findings ↑Latency ↓Nerve conduction velocity ↓SNAP ↓CMAP ↑Insertional activity Fibrillation potentials and fasciculations ’Giant’ MUPs Normalization of NCV Loss of ‘giant’ MUPs