Nerve Compression Syndromes

Question 1

How is nerve conduction in the carpal tunnel reported?

Answer 1

In terms of “latency,” with the unit being milliseconds (ms).

Question 2

What is “latency”?

Answer 2

The time it takes for an electrical stimulus to travel along a nerve from the site of stimulation to a recording
electrode in a target muscle.

Question 3

What is the normal value for motor latency at the carpal tunnel?

Answer 3

Less than 4.0 ms.

Question 4

How is nerve conduction at the elbow reported?

Answer 4

In terms of velocity (m/s).

Question 5

What is a clinically significant decrease in velocity at the elbow?

Answer 5

10 or more m/s.

Question 6

What is the difference between compressive neuropathies and peripheral neuropathies?

Answer 6

In peripheral (systemic) neuropathies, the nerve conduction is decreased diffusely both proximally and distally in
multiple nerves.

Question 7

What are typical electromyography (EMG) findings for long-standing nerve compression and axonal damage?

Answer 7

Wide biphasic fibrillation potentials.

Question 8

What is the double crush syndrome?

Answer 8

A proximal site of nerve compression predisposes the peripheral nerve to a second distal site of compression. For
example, patients with cumulative or repetitive trauma or stress often have problems from the neck to the hand.

Question 9

What nerve is affected with thoracic outlet syndrome (TOS)?

Answer 9

Lower trunk of brachial plexus with symptoms mimicking cubital tunnel syndrome.

Question 10

What are the contents of the “thoracic outlet”?

Answer 10

Subclavian vein, subclavian artery, and brachial plexus.

Question 11

TOS is more common in what gender?

Answer 11

Female (3.5:1).

Question 12

Within the population of patients with cervical ribs, how many are bilateral?

Answer 12

50%.

Question 13

When do patients with TOS typically get their symptoms (ulnar-sided numbness)?

Answer 13

When their arms are above their heads.

Question 14

What is Adson maneuver?

Answer 14

Dampening of radial pulse with inhalation, neck extension, and head rotation to the affected side in patients with
TOS. There are varying descriptions of how to perform this maneuver.

Question 15

How accurate is an Adson maneuver?

Answer 15

False positives are so common that test is thought of in terms of historical interest only.

Question 16

What is Wright maneuver?

Answer 16

Reproduction of TOS symptoms or dampening of radial pulse with arm hyperabducted and head in neutral or
turned away from the affected side.

Question 17

How accurate is Wright maneuver?

Answer 17

It is positive in 7% of normal patients and thus should be used only to support a diagnosis of compression in
patients with arterial symptoms.

Question 18

What is Roos maneuver?

Answer 18

Both arms are put into 90◦ of abduction and external rotation and the patient is asked to open and close the hands for 3 minutes. Many patients will have forearm fatigue, but patients with TOS have reproduction of their symptoms.

Question 19

How accurate is Roos maneuver?

Answer 19

It is the most reliable of the three maneuvers noted. However, some patients with carpal tunnel syndrome (CTS) and no TOS will develop symptoms limited to the median nerve distribution.

Question 20

What are the electrodiagnostic testing results seen with TOS?

Answer 20

Negative EMG for ulnar nerve, positive somatosensory evoked potentials with arm in offending position.

Question 21

What is the first-line therapy for TOS?

Answer 21

Conservative treatment with exercises to strengthen the shoulder girdle, weight loss, and occasionally breast
reduction in women.

Question 22

Name the two approaches to the thoracic outlet.

Answer 22

Supraclavicular and transaxillary.

Question 23

What is similar and what is different about the presentation of TOS and cubital tunnel syndrome?

Answer 23

Similar: ulnar distribution numbness; different: TOS has medial forearm numbness.

Question 24

How do you tell the difference between ulnar nerve compression at the cubital tunnel from compression at the wrist (Guyon canal)?

Answer 24

Sensory changes on the dorsoulnar hand.
The dorsal sensory branch of the ulnar nerve branches from the main ulnar nerve approximately 7 cm proximal to the pisiform, providing sensation to the dorsoulnar hand. Therefore, patients with cubital tunnel compression should have some difference in sensation of the dorsoulnar hand between the affected side and the unaffected side.

Question 25

What is the distribution of motor weakness seen with cubital tunnel syndrome?

Answer 25

Flexor digitorum profundus (FDP) of ring and small fingers, ulnar intrinsic muscles.

Question 26

Describe Froment sign.

Answer 26

With ulnar nerve palsy, patients compensate for lack of adductor pollicis (ulnar innervated) function by flexing the thumb interphalangeal (IP) joint (pinch power then provided entirely by the median innervated flexor pollicis longus [FPL]).

Question 27

What are potential sites of ulnar nerve compression?

Answer 27

1. Arcade of Struthers—an upper arm fascial arcade through which the nerve passes. Present in 70% of patients. 2. Intermuscular septum between the brachialis and medial head of triceps. Can cause compression even in absence of arcade of Struthers so they are distinct. 3. Medial head of triceps—whether by hypertrophy (bodybuilders) or anterior subluxation over medial epicondyle. 4. Osborne ligament—a fascial arcade formed between the two heads of the flexor carpi ulnaris (FCU). The most common site of compression. 5. Flexor-pronator aponeurosis—a fascial band between the flexor digitorum superficialis (FDS) and the FDP. 6. Guyon canal—at the wrist (see Figure 34-1). Second most common site of entrapment.

Question 28

Where is the arcade of Struthers?

Answer 28

8 cm proximal to the medial epicondyle of the elbow.

Question 29

What is the cubital tunnel?

Answer 29

Floor—medial collateral ligament of elbow (spans from medial epicondyle to olecranon). Roof—Osborne ligament. Sides—medial epicondyle and olecranon (to which the above two structures attach).

Question 30

What are implicated as the main compressive structures in cubital tunnel syndrome?

Answer 30

Arcade of Struthers, intermuscular septum, Osborne ligament or band (fascia connecting ulnar and humeral heads of FCU), and the flexor–pronator aponeurosis.

Question 31

Explain why the elbow hyperflexion test elicits symptoms of cubital tunnel syndrome?

Answer 31

1. Elbow flexion increases the distance the ulnar nerve has to travel to traverse the elbow. 2. Feel your own olecranon and medial epicondyle with your elbow extended. Now flex your elbow and feel how the distance between them grows, tightening Osborne ligament and compressing the nerve.

Question 32

How sensitive is electrodiagnostic testing at the elbow?

Answer 32

50% false-negative rate for nerve compression in this region.

Question 33

What is a Martin–Gruber anastomosis, and what is its significance in relation to cubital tunnel syndrome?

Answer 33

Interconnection between the median and ulnar nerves at the level of the forearm; presence of this anomalous interconnection can result in spared intrinsic muscle function with cubital tunnel syndrome (because the median nerve innervates the intrinsics in this situation).

Question 34

What is a Riche–Cannieu anastomosis?

Answer 34

Interconnection between the median and ulnar nerve in the hand, typically the deep or motor branch of the ulnar nerve. Again, there may be confusion for the examiner as muscles usually innervated by the ulnar nerve continue to function.

Question 35

What are the key steps involved in anterior submuscular ulnar nerve transposition?

Answer 35

Release of FCU origin, transposition of ulnar nerve anterior to medial epicondyle, resuturing of FCU to epicondyle.

Question 36

So you have to do at least a submuscular transposition of the nerve, right?

Answer 36

Maybe not. In 1957, Geoffrey Osborne, a British orthopedic surgeon, reported 13 cases of cubital tunnel syndrome in which he released the ligament or band that now bears his name noting that it was tight in elbow flexion but lax in extension. These patients did no differently than those patients having a formal transposition. Several studies since then have supported this treatment.

Question 37

What is the other common ulnar nerve transposition method?

Answer 37

Subcutaneous.

Question 38

❍ What is a common postoperative complication of ulnar nerve surgery at the elbow causing a painful incision?

Answer 38

Neuroma of the medial antebrachial cutaneous nerve resulting from injury during the approach to the ulnar nerve.

Question 39

What is Guyon canal?

Answer 39

Roof-volar carpal ligament proximally and palmaris brevis distally. Floor—transverse carpal ligament. Ulnar wall—pisiform. Radial wall—hard to say. Some think of the hamate hook, but in many specimens the ulnar neurovascular bundle lies palmar or even radial to the hamate hook.

Question 40

What are the usual causes of ulnar tunnel syndrome?

Answer 40

Ganglions, trauma (hamate fractures), tumors, vascular anomalies, arthritis.

Question 41

What is the distribution of numbness with ulnar tunnel syndrome?

Answer 41

Small and ring fingers, but not dorsum of hand (because dorsal sensory branch is not involved).

Question 42

How does the motor examination differ between ulnar nerve compression at the wrist and the elbow?

Answer 42

Ulnar nerve compression at the wrist affects pinch strength but not grip strength; compression at the elbow affects both pinch and grip strength.

Question 43

In general, what is the treatment for ulnar tunnel syndrome?

Answer 43

Exploration of Guyon canal, decompression of nerve, removal of space-occupying lesion, ulnar artery reconstruction (if necessary). You have to feel for masses as they are responsible for 30% to 45% of all cases of ulnar tunnel syndrome.

Question 44

In what portion of the ulnar nerve is the motor fasciculus at wrist level?

Answer 44

Ulnar and dorsal.

Question 45

What are the syndromes associated with median nerve compression?

Answer 45

1. Pronator syndrome 2. Anterior interosseous syndrome 3. Carpal tunnel syndrome

Question 45

What conditions are associated with an increased incidence of CTS?

Answer 45

Most are idiopathic, but can be associated with pregnancy, diabetes, alcoholism, arthritis, amyloidosis, or thyroid disorders.

Question 46

How often is CTS bilateral?

Answer 46

60% of cases.

Question 47

❍ What are the borders of the carpal tunnel?

Answer 47

1. Roof—transverse carpal ligament 2. Floor—carpal bones and their ligaments 4. Ulnar wall—hook of hamate

Question 48

What are the classic symptoms of CTS?

Answer 48

Numbness (index, middle, radial side of ring finger), weakness, nocturnal pain, relief of symptoms while wearing a wrist brace.

Question 49

What are the structures thought to cause effort-associated CTS (ie, symptoms seen with repetitive gripping)?

Answer 49

Lumbrical muscles. They arise from the FDP tendons and are within the carpal tunnel during gripping activities.

Question 50

What is Phalen test?

Answer 50

Wrist is passively dropped into flexion. If symptoms are seen within 30 seconds, the test is positive.

Question 51

What is the most sensitive physical examination maneuver for diagnosis of CTS?

Answer 51

Carpal compression test.

Question 52

How are results of the carpal compression test reported?

Answer 52

In number of seconds from initiation of thumb pressure over the carpal tunnel (pressure should only be hard enough to make examiner’s thumb blanch).

Question 53

What electrodiagnostic study results signify median nerve conduction changes?

Answer 53

Median nerve latency increase of 10% or more above that of the ulnar nerve.

Question 54

What electrodiagnostic study result signifies muscle denervation with CTS?

Answer 54

Fibrillation potentials in the abductor pollicis brevis.

Question 55

What is the success rate of steroid injections for CTS?

Answer 55

Only approximately 20% to 22% of patients get long-term (>18 months) relief.

Question 56

Where is the motor fasciculus of the median nerve at the wrist?

Answer 56

Radial and palmar. This should be easy to remember since the recurrent motor branch of the median nerve comes off of the main nerve radially and palmarly. In addition, remember that the median nerve motor fasciculus (radial, palmar) is the direct opposite of the ulnar nerve motor fasciculus (ulnar, dorsal).

Question 57

What is Kaplan line and how is it used to determine the position of the motor branch of the median nerve?

Answer 57

Kaplan’s line is a line drawn as an extension along the ulnar border of the abducted thumb. The intersection of this line and one drawn longitudinally from the index–middle finger web space is the rough approximation of the motor branch.

Question 58

What is Kaplan line and how is it used to determine the position of the motor branch of the median nerve?

Answer 58

Kaplan’s line is a line drawn as an extension along the ulnar border of the abducted thumb. The intersection of this line and one drawn longitudinally from the index–middle finger web space is the rough approximation of the motor branch.

Question 59

What are the patterns of the route of the motor branch to the thenar musculature in relation to the transverse carpal ligament?

Answer 59

Extraligamentous (approximately 50%), subligamentous (30%), and transligamentous (20%–25%).

Question 60

Which muscles are innervated by the motor branch of the median nerve in the hand?

Answer 60

1. Opponens pollicis 2. Flexor pollicis brevis 3. Abductor pollicis brevis 4. Two radial lumbrical muscles

Question 61

What are the advantages of endoscopic carpal tunnel release when compared with the open technique?

Answer 61

Less scar tenderness, and earlier restoration of grip and pinch strength. But after 3 months there are no differences.

Question 62

What has been demonstrated as the chief disadvantage of endoscopic carpal tunnel release when compared to open?

Answer 62

Greater incidence of reversible nerve injury (4.3% in endoscopic vs 0.9% in open).

Question 63

In what outcomes are endoscopic and open carpal tunnels release equivocal?

Answer 63

Pain and return to work.

Question 64

Is internal neurolysis indicated during routine carpal tunnel decompression?

Answer 64

no

Question 65

During secondary surgery for recurrent CTS, where should the incision be made?

Answer 65

A new incision should be made more ulnar to the previous scar because the median nerve is adherent to or within the transverse carpal ligament.

Question 66

What are sites of median nerve compression in the elbow/forearm?

Answer 66

1. Ligament of Struthers—ligament between humeral supracondylar process and medial epicondyle 2. Lacertus fibrosis—aka bicipital aponeurosis—a fascial band between the biceps tendon and the fascia of the flexor pronator mass 3. Two heads of the pronator teres 4. FDS fibrous arch

Question 67

How can one specifically test for median nerve compression at the ligament of Struthers?

Answer 67

When flexing the elbow against resistance, the symptoms are exacerbated.

Question 68

How can one specifically test for median nerve compression at the pronator teres?

Answer 68

With resisted pronation, symptoms are exacerbated. The elbow must be fully extended to avoid confusion with compression by the bicipital aponeurosis.

Question 69

How can one specifically test for median nerve compression at the FDS arch?

Answer 69

Long finger flexion test: with resisted flexion of the long finger, the FDS arch compresses the median nerve, and symptoms are exacerbated.

Question 70

What is a Gantzer muscle?

Answer 70

An accessory head of the FPL originating from the medial humeral epicondyle and possibly also the coronoid process of the ulna and found in up to 45% of specimens. It can contribute to compression of the median nerve.

Question 71

What is the chief difference between the pronator syndrome and the anterior interosseus nerve (AIN) syndrome?

Answer 71

Deficits in pronator syndrome are sensory, whereas deficits in AIN syndrome are motor.

Question 72

What are the symptoms of the pronator syndrome?

Answer 72

Pain in forearm, numbness in median nerve sensory distribution (thumb, index, and middle fingers).

Question 73

What muscles are innervated by the AIN?

Answer 73

1.Flexor pollicis longus 2. Pronator quadratus 3. FDP to index finger 4. FDP to middle finger (this varies between the AIN and ulnar nerve depending on the patient)

Question 74

What are the symptoms of AIN syndrome?

Answer 74

Loss of precision pinch (cannot flex thumb IP or index DIP), pain in the forearm relieved by rest.

Question 75

What can patients with AIN syndrome NOT do?

Answer 75

Make an “OK” sign. They cannot flex their thumb IP or index DIP joints.

Question 76

❍ Is there a difference in the surgical treatment of AIN syndrome and pronator syndrome?

Answer 76

No, in both cases the nerve is explored completely and released from all compressing structures from the elbow to the distal forearm.

Question 77

What are possible sites of radial nerve compression?

Answer 77

1. The lateral humeral intermuscular septum 2. The radial head 3. Supinator fascia—aka arcade of Fro ̈hse (posterior interosseous nerve [PIN] syndrome) 4. Vascular Leash of Henry—radial recurrent vessels at the elbow 5. Extensor carpi radialis brevis (ECRB) origin 6. Between brachioradialis and extensor carpi radialis longus (ECRL)—Wartenberg syndrome (involves the superficial sensory branch of the radial nerve only)

Question 78

What is the most common site of radial nerve compression?

Answer 78

Supinator muscle fascia (aka the arcade of Fro ̈hse).

Question 79

Where is the radial tunnel?

Answer 79

It runs from the radial head to the distal edge of the supinator; the biceps tendon is the medial wall, and the ECRL and ECRB origins form the lateral wall.

Question 80

What are the symptoms of radial tunnel syndrome?

Answer 80

Lateral elbow pain, especially with repetitive elbow extension. Motor findings are usually absent.

Question 81

What physical examination finding differentiates radial tunnel syndrome from lateral epicondylitis?

Answer 81

Tenderness 4 cm distal to lateral epicondyle (between brachioradialis and ECRL) is seen with radial tunnel syndrome.

Question 82

Is there typically a sensory component to PIN syndrome?

Answer 82

No, the PIN innervates the extensors, and therefore results in weakness and pain, but not sensory deficits.

Question 83

What is the difference between radial tunnel syndrome and posterior interosseous nerve compression?

Answer 83

In radial tunnel syndrome symptoms involve pain over the dorsoradial forearm near the elbow. There is rarely weakness. In posterior interosseous nerve compression symptoms involve weakness of the thumb and finger extensors AS WELL AS pain.

Question 84

Is it common to see electrodiagnostic changes with radial nerve compression?

Answer 84

No, often the EMG/NCS is normal. Diagnosis is often based solely on history and physical examination.

Question 85

What is the role for surgery in PIN syndrome and radial tunnel syndrome?

Answer 85

Radial tunnel syndrome should be initially managed nonoperatively (muscle palsy is not seen with this syndrome); PIN syndrome should be treated operatively to prevent permanent muscle palsy.

Question 86

What is the vascular leash of Henry?

Answer 86

A network of radial recurrent vessels at the elbow that can compress the PIN, the radial sensory nerve, or both.

Question 87

What is Wartenberg syndrome?

Answer 87

Compression neuropathy of the radial sensory nerve due to trapping between the brachioradialis and ECRL. Other names include superficial radial neuritis or “cheiralgia paresthetica.”

Question 88

What can cause Wartenberg syndrome?

Answer 88

External compression (handcuffs), tight watch, surgical scarring, repetitive activities.

Question 89

Then what is Wartenberg sign?

Answer 89

Indicates ulnar neuropathy. The patient is unable to hold the small finger against the ring finger with the fingers in extension due to the unopposed action of the radially innervated extensor digiti minimi. The ulnarly innervated palmar interossei is weak and unable to adduct the small finger.

Question 90

How does one differentiate radial sensory nerve compression from de Quervain extensor tenosynovitis in the presence of a positive Finkelstein sign?

Answer 90

Resisted thumb extension with the wrist held in neutral causes pain in tendinitis but not in nerve entrapment.