Pathophysiology of Peripheral Nerve Lesions Part 2: Upper Extremity Entrapment Syndromes

1. Pathophysiology of Peripheral Nerve LesionsPart 2: Upper Extremity Entrapment Syndromes David A. Lake, PT, PhD Department of Physical Therapy Armstrong Atlantic State University Savannah, GA

2. Examination of Entrapment Peripheral Neuropathies • History • Focus on occupational/activities that involve repetitive motion • Have patient trace rather than verbalize paresthesia or pain pattern • Distinct symptoms suggest a distal lesion • Complex symptoms suggest a proximal lesion

3. Examination of Entrapment Peripheral Neuropathies • Sensory Exam • Sensory symptoms before motor • Light touch, 2 pt discrimination over distribution of nerve • Inspect for trophic changes to skin - often an effect on autonomic fibers to an area

4. Examination of Entrapment Peripheral Neuropathies • Motor Exam • Check reflexes bilaterally • Inspect for atrophy - again bilateral comparison • Bilateral testing for muscle strength in muscles along the nerve course

5. Examination of Entrapment Peripheral Neuropathies • Reproduction of symptoms • Positioning to narrow tunnel through which the nerve progresses • Muscle contraction against resistance is compression is caused by passing through a muscle • Percussion tests - tapping on nerve or tapping/applying pressure to area of compression

6. Examination of Entrapment Peripheral Neuropathies • NCV & EMG testing • > 50% reduction in amplitude of compound action potential in nerve conduction velocity tests (NCV) sign of impairment • EMG shows abnormal spontaneous activity within 2 weeks of acute compression/trauma if deficit in motor axons - and is gold standard if motor deficit

7. Examination of Entrapment Peripheral Neuropathies • NCV & EMG testing • Abnormal spontaneous activity includes: • Positive sharp waves • Fibrillation potentials

8. Examination of Entrapment Peripheral Neuropathies • NCV & EMG testing • Abnormal EMG activity also includes: • Enhanced insertional activity

9. Examination of Entrapment Peripheral Neuropathies • NCV & EMG testing • Abnormal EMG activity also includes: • Reduced maximal evoked activity (interference pattern) Normal Interference Pattern Reduced Interference Pattern

10. Examination of Entrapment Peripheral Neuropathies • NCV & EMG testing • Abnormal EMG activity also includes: • Eventually the replacement of normal biphasic MUAPs with polyphasic MUAPs Biphasic MUAPs Polyphasic MUAPs

11. Examination of Entrapment Peripheral Neuropathies • NCV & EMG testing • Compare bilaterally and there are normative standards for • Conduction velocity • Compound action potential amplitudes • Distal latencies

12. Examination of Entrapment Peripheral Neuropathies Brachial Plexus and Early Branches of the Brachial Plexus

13. Entrapment Neuropathies • Thoracic Outlet Syndrome (TOS) • Name change suggested to cervico-axillary syndrome because of anatomical terminology • Anatomical thoracic outlet from thorax to abdomen - covered by the diaphragm • But TOS still most commonly used • Three major forms of TOS • Scalene entrapment syndrome • Costoclavicular entrapment • Costopectoral Tunnel syndrome

14. Entrapment Neuropathies • Scalene Entrapment Syndrome • The brachial plexus passes out between the anterior and middle scalene muscle Anterior Scalene Middle Scalene Brachial Plexus

15. Entrapment Neuropathies • Scalene Entrapment Syndrome • Most commonly caused by: • scalene muscle hypertrophy • poor posture • prolonged overhead work • less often due to abnormal presence of a cervical rib or a scalene minimus muscle • Most commonly affects the lower plexus C8 & T1 spinal nerves

16. Entrapment Neuropathies • Scalene Entrapment Syndrome • Symptoms most commonly include: • Numbness in fingers, hand and anterior forearm

17. Entrapment Neuropathies • Scalene Entrapment Syndrome • Symptoms most commonly include: • Clumsiness & loss of fine motor control of the hand • Occasionally vascular signs such as: • UE ischemic changes • Raynaud like symptoms • Ischemic finger ulcerations

18. Entrapment Neuropathies • Costoclavicular Entrapment • Subclavian artery & brachial plexus pass between clavicle and first rib

19. Entrapment Neuropathies • Costoclavicular Entrapment • Most commonly the result of: • Poor posture • Congenital fibrous bands • Can occur secondary to a clavicular fracture and callus that develops as part of fracture healing • Most commonly affects lower plexus • Vascular problems more common than in scalene entrapment syndrome

20. Entrapment Neuropathies • Costoclavicular Entrapment • Symptoms include: • Numbness of the fingers, hand and forearm • Arm and hand pain • When vascular problems occur they are similar to those seen with scalene entrapment syndrome but may also include hand edema secondary to venous compromise

21. Entrapment Neuropathies • Costopectoral Tunnel syndrome • Costopectoral tunnel formed by the pectoralis minor lying over the anterior thoracic wall and the corocoid process of the scapula • Brachial plexus (blue) & brachial artery (red) run through it

22. Entrapment Neuropathies • Costopectoral Tunnel syndrome • Most common cause is 1) hyper-trophic pectoralic minor or 2) prolonged overhead activities • Less commonly caused by 1) an abnormal muscle, the chondro-epitrochlearis muscle arising from the pectoralis minor or 2) scar tissue in the subpectoral space • More commonly accompanied by vascular problems than the other two forms of TOS

23. Entrapment Neuropathies • Costopectoral Tunnel syndrome • Symptoms include: • Pain and parethesias in the fingers and hand • Made worse by arm abduction • Hand ischemia and edema

24. Entrapment Neuropathies • Long Thoracic Nerve entrapment • Lies deep to the brachial plexus on top of the 2nd rib and may be compressed against this second rib. Long Thoracic Nerve Potential Entrapment Site

25. Entrapment Neuropathies • Long Thoracic Nerve entrapment • C5 and C6 fibers of the long thoracic nerve may pass through the middle scalene muscle and may be compressed by it

26. Entrapment Neuropathies • Long Thoracic Nerve entrapment • Compression can come from: • Tight bandage across the lateral chest, trauma to the shoulder • Poorly adjusted crutches • Symptoms generally include: • Vague anterior shoulder pain or paresthesias • Distinct winging of the scapula is generally seen

27. Entrapment Neuropathies • Long Thoracic Nerve entrapment • Scapular winging

28. Entrapment Neuropathies • Long Thoracic Nerve Damage • Damage can occur during a radical lymph node resection or mastectomy

29. Entrapment Neuropathies • Quadrilateral Space Syndrome • Space formed by teres major, teres minor, shaft of the humerus & long head of the triceps through which runs the axillary nerve Axillary Nerve Post Humeral Circumflex Artery

30. Entrapment Neuropathies • Quadrilateral Space Syndrome • Closure of this space results subsequent to: • Scapular or humeral fractures • Shoulder dislocations • Teres major hypertrophy

31. Entrapment Neuropathies • Quadrilateral Space Syndrome • Symptoms • Paresthesia - lateral shoulder and proximal arm • Deltoid paresis and atrophy • Shoulder abduction paresis with compensatory actions of the supraspinatus and biceps • Tenderness over the quadrilateral space • Abnormal scapulohumeral rhythm

32. Entrapment Neuropathies • Suprascapular Nerve Syndrome • Suprascapular nerve runs under the transverse scapular ligament through the scapular notch

33. Entrapment Neuropathies • Suprascapular Nerve Syndrome • 50% of individuals have an inferior transverse scapular ligament as an additional connective tissue roof which can entrap nerve & Transverse Scapular Ligament Transverse Scapular Ligament Entrapment Inferior Transverse Scapular Ligament Entrapment Inferior Transverse Scapular Ligament

34. Entrapment Neuropathies • Suprascapular Nerve Syndrome • In addition to possible entrapment beneath the superior and inferior transverse scapular ligaments, other possible causes include: • Supraglenoid ganglionic cyst can narrow gap • Scapular fracture • Repetitive overhead activities • Weight bar resting on shoulders during squat exercises

35. Entrapment Neuropathies • Suprascapular Nerve Syndrome • Signs and Symptoms • Posterior shoulder or acromioclavicular pain • Nocturnal pain • Positive crossed-arm adduction test • Supraspinatus and infraspinatus atrophy • Paresis of shoulder abduction and external rotation

36. Entrapment Neuropathies Median Nerve Entrapment Neuropathies

37. Entrapment Neuropathies • Median nerve syndromes- there are several potential points of median nerve entrapment: • Supracondylar tunnel - Rare • Pronator teres • Anterior interosseous nerve • Carpal tunnel

38. Entrapment Neuropathies • Median nerve syndromes- Supracondylar tunnel (RARE) • Supracondylar process - anomalous growth proximal to the medial epicondyle on the humerus. • More common would be entrapment by the medial intermuscular septum as the supracondylar process is a rare, anomalous structure occurring in only 1-3% of the population

39. Entrapment Neuropathies • Median nerve syndromes- Supracondylar tunnel • If the supracondylar process exists, there is a connective tissue link between the supracondylar process and the medial epicondyle (Ligament of Struthers) forms a tunnel through which the median nerve runs • Sometimes seen secondary to humeral fracture or prolonged immobilization of the elbow

40. Entrapment Neuropathies • Median nerve syndromes- Supracondylar tunnel • Supracondylar process - anomalous growth proximal to the medial epicondyle on the humerus. • Ligament of Struthers forms the Supra-condylar tunnel Supracondylar Process Supracondylar Tunnel Ligament of Struthers

41. Entrapment Neuropathies • Median nerve syndromes- Supracondylar tunnel • Median nerve runs through this supra-condylar tunnel

42. Entrapment Neuropathies • Median nerve syndromes- Supracondylar tunnel • Sometimes seen secondary to humeral fracture or prolonged immobilization of the elbow • Symptoms • Carpal tunnel like symptoms of paresthesias and pain along the median nerve distribution & atrophy and paresis of hand intrinsic flexors • Except that pain radiates up into the forearm & long wrist and finger flexors are also involved. • NCV changes both proximal and distal to the carpal tunnel seen

43. Entrapment Neuropathies • Median nerve syndromes- Supracondylar tunnel • Symptoms • Example of pain radiates up into the forearm along median nerve distribution

44. Entrapment Neuropathies • Median nerve syndromes-Pronator teres • Median nerve runs between the two heads of the pronator teres to desend to run superficially to the flexor digitorum profundus and deep to the flexor digitorum superficialis • However at times the nerve can penetrate through the pronator teres or the pronator teres can have an anomalous head that narrowly surrounds the median nerve or has extra fibrous connections between the heads

45. Entrapment Neuropathies • Median nerve syndromes-Pronator teres syndrome • Median nerve runs between the two heads of the pronator teres to desend to run superficially to the flexor digitorum profundus and deep to the flexor digitorum superficialis

46. Entrapment Neuropathies • Median nerve syndromes-Pronator teres syndrome • However at times: • Median nerve can penetrate through the pronator teres • Pronator teres can have an anomalous head that narrowly surrounds the median nerve • Pronator teres has extra fibrous connections between the heads • Pronator teres hypertrophy

47. Entrapment Neuropathies • Median nerve syndromes- Pronator teres Syndrome symptoms include: • Carpal tunnel like symptoms of pain and paresthesias along the median nerve distribution • Atrophy and paresis of hand intrinsic flexors • Impaired thumb, index and middle finger flexion • Tinel's sign over the pronator teres • Symptoms get worse with resisted pronation or sustained forearm supination with elbow extension

48. Entrapment Neuropathies • Median nerve syndromes- Anterior interosseous Nerve Syndrome • Anterior interosseous nerve is a motor nerve that innervates the flexor digitorum profundus (digits 2 & 3), flexor pollicis longus and pronator quadratus

49. Entrapment Neuropathies • Median nerve syndromes- Anterior interosseous Nerve Syndrome • Anterior interosseous nerve dives through the flexor digitorum profundus

50. Entrapment Neuropathies • Median nerve syndromes- Anterior interosseous Nerve Syndrome • The nerve runs along the interosseous membrane between radius and ulna Anterior - up Posterior down Medial - right Lateral - left Arrows: Yellow - Anterior Interosseus Nerve Red - Flexor Digitorum Profundus Blue - interosseus membrane