Causes of peroneal neuropathy

Argument in letters section of Neurology 2003;60:1559-1560; letter writer lists "known" causes of peroneal neuropathy at fibular head as etiologically identifiable in 83%: perioperative, 30.6%, postural 19 %, bedridden 13.9 %, weight loss 5.6 %, multiple trauma 5.6 %, chalk positioning 5.6 %, synovial cyst 2.8 %).

Cubital tunnel syndrome

Clinical-- impaired sensation over the fifth and half the fourth finger
Weakness and wasting of the unlar innervated hand muscles

EMG shows sparing of FCU (proximal)
afffects the ulnar half of the flexor digitorum profundus

Digital nerve entrapment

Small sensory branches of the median nerve may be compressed against the deep transverse metacarpal ligament, with pain in one or two fingers, worse with lateral hypewrextension of the digits and tenderness and dysesthesias over the palmar surfaces between the metacarpals.

Carpal tunnel associations

Amyloidosis (primary or secondary)
Acromegaly, 35 %
Rheumatoid arthritis, 23 % (differentiate from disuse, c spine disease, or ulnar n at elbow)
eosinophilic fasciitis
myxedema
lupus erythematosus
hyperparathyroidism
toxic shock syndrome
Colles fracture
Fracture of the capitatum or hamate
soft tissue swelling around wrist after injury
intraneural hemorrhage
anomaly of distal radius
subluxed carpus on distal radioulnar
rubella immunization
DM
Gout
myeloma (=Leri's pleonosteosis)
cerebral palsy
TB
pregnancy
toxic shock s
toxic oil syndrome
mucopolysaccharidosis
congenital av fistula
dialysis
brachial hypertrophy
SLE
scleroderma

Signs/symptoms of CTS
Paresthesias and pain relieved with movement, worse at night
Raynaud's phenomenon
hypesthesias 1st 3 digits and half of fourth
Sensory loss confined to tip of third digit
Sensory splitting of fourth digit on exam
Sparing of thenar eminence
Phalen's and Tinel's signs
Flick sign (relief with shaking wrist) most reliable sign

Motor APB-- pushing up perpendicular to palm
Opponens pollicis -- touch thumb and fifth finger
Phalen's/ Tinel's signs

Differential diagnosis
high median compression at elbow
C 6 radiculopathy
handcuff neuropathy

Anterior interosseous syndrome (Kiloh-Nevin s.)

AI s is due to injury to the branch of the median nerve just past the pronator teres muscle and can be unilateral or bilateral. There is pain in the forearm and elbow, made worse by resisted proximal ip flexion of the middle finger. Asked to make the "OK" sign, patients will make a triangle sign instead (pinch sign). Spontaneous recovery occurs over 6 weeks to 18 months. Identical syndromes can be caused by more proximal lesions, including antecubital level or the brachial plexus, due to prearrangement of the bundles of nerves proximally. Weakness also is seen in fl dig profundus 1 and 2 and PQ.

Nerve conduction may be normal or show a delay from pronator quadratus. EMG is abnormal in the flexor pollicis longus, flexor digitorum profundus I and II, and pronator quadratus.

Associations include trauma, forearm (midshaft radial) fractures, humeral fracture, injection/phlebotomy of antecubital vein, stab wounds, fibrous bands, related to exercise. Occassionally associated with brachial neuritis, CMV infection, bronchogenic carcinoma mets or spontaneous. Consider plexitis.

Other median entrapments occur at the ligament of Struthers, Lacertus fibrosis and the tendinous insertion of FDS. Humeral spur at supracondylar site can produce brachial claudication and radial artery obliteration, exacerbation of numbness and pain by resisted elbow extension and forearm supination.

Median nerve syndromes: pronator teres syndrome

The median nerve pierces the two heads of the pt (pronator teres) before passing under it. Trauma, fracture, muscle hypertrophy or an anomalous band connecting the pt to the tendon arch of the flexor digitorum sublimis can injure the nerve here. Also tenosynovitis, muscle hemorrhage, tear, postop scarring, anomalous median artery, or increased forearm compartment pressure can be related.

Clinically,  pain and tenderness appears over the pronator teres, is fatiguaibile, with the pain radiating occassionally to the shoulder. Weakness of the flexor pollicis and apb, and preserved pronation. Sensory changes over the thenar eminence help to make the diagnosis. EMG/NCS distal studies are normal with slowing in the wrist.

A different entrapment at the site of the ligament of Struthers affects the nerve near the lower humerus. The difference clinically is that here, pronator teres is affected unlike the pt syndrome in which pt is spared. Compression of the brachial artery with full extension of the arm obliterates the radial pulse.

Differentiate from CTS with Tinel's over site of entrapment, absent Phalen's sign, rare nocturnal exacerbation, weak mm over forearm worse with pronation, elbow flexion or contraction of the superficial flexor of second digit. Consider CTS, plexopathy, other median neuropathy syndromes, or radiculopathy.

Suprascapular neuropathy

Injury from pressure on/trauma to the shoulder, stab wounds above the scapula, improper use of crutches, stretching of the nerve, eg. volleyball players during serving, r/o rupture of the rotator cuff. In athletics intense activity over weeks may cause it. Baseball pitchers are susceptible. Volleyball players, weight lifters and wrestlers are susceptible to developing it. Many athletes have exclusive or predominant involvement of the infraspinatus muscle.

Clinically one sees difficulty initiating abduction of the arm and externally rotating the arm, with an aching pain in the shoulder joint.The sign is selective wasting and weakness of the supraspinatus and infraspinatus muscles. Testing the deltoid separately means taking the fully abducted arm and having the patient pull backwards; also looking for deltoid atrophy. Also useful are tenderness in the suprascapular notch and pain evoked by forced adduction of the arm.

Gradual onset neuropathies may be due to ganglia in the suprascapular notch and spinoglenoid notch, or malignant tumors from the scapula. True entrapment neuropathies within the notch to a spur or ligament. Inherited calcification of the ligament may occur.

Differential includes ABN (acute brachial neuritis) , and less commonly shoulder joint/rotator cuff disorders, disuse wasting, or combined shoulder/nerve injury. EMG is definitive. MRI can look at entrapment in the suprascapular notch, and determine which muscles and hence which nerves are involved.

Treatment may involve rest, physiotherapy, injections, suprascapular notch exploration (supraglenoid notch if only infraspinatus is involved).

Ataxic v. painful form of paraneoplastic neuropathy

Oki Y, Koike H, Iijima M et al. Neurology 2007; 69:564-572.

Group one-- dep sensory disturbance, shows sensory ataxia, markedly abnormal sural nerve,

Group 2-- superficial sensory disturbance- shows severe hyperalgesia, involvement small myelinated fibers and unmyelinated fibers.

Both groups showed an axonal sensory neuropathy with greater diminution of SNAPs in first (sensory ataxia) group. Both groups had about 50% presence of antiHu antibodies. Both groups had some cases with benefit from treating the cancer; immunotherapy was of transient benefit.

Genitofemoral nerve

Arises from L1 and L2 roots, and branches into the lumboinguinal and external spermatic nerves, supplies the skin over femoral triangle, the cremasteric muscle and the inner upper thigh, labia or scrotum

Branches of the Nerves of forearm

Anterior interosseous:
Flexor pollicus longus
Pronator quadratus
Flexor digitorum profundus I and II

Ulnar:
Flexor carpi ulnaris
Flexor digitorum III and IV
Intrinsic hand muscles

Median-- most flexors in forearm, lumbric alsI and II, and muscles of thenar eminence