Ulnar neuropathy at elbow and distal

UN at elbow can occur during repetive stress, more commonly with certain positions and decreased body mass, and more commonly in men. Associations exist with overhead throwing sports, cross country skiing, weight lifting and racket sports. One third have no cause. Among athletes it often accompanies other elbow problems including attenuation of the ulnar collateral ligament and medial epicondylitis. The clinical presentation is sensory ulnar in non-athletes but athletes tend to have medial epicondyle pain first. Evaluation requires X rays, +/- ultrasound and MRI. Conservative treatment is rest, splinting, NSIAD's, NOT steroid injection. Surgery is for those with mild/moderate pain who fail conservative therapy,or intractable pain or fixed sensory deficits or weakness. Distal ulnar neuropathy can occur at wrist proximal to, within, or beyond Guyon's canal. The first spares the dorsal ulnar cutaneous branch, the second all cutaneous branches, and the third all but the superficial sensory branches of the fourth and fifth digits. It affects cyclists, wheelchair athletes, racket and club sports. NCS help; therapy is conservative unless there is a fracture such as the hamate. Sensory symptoms in the forearm suggest brachial neuritis rather than ulnar neuropathy. Pitfalls in examination: if nerve conductions appear to show an ulnar conduction block, check for a Martin Gruber anastamosis. Fibers destined for FDI/APB/ADM may travel with median nerve at elbow in about 20 percent of patients. Stimulate the median nerve at the elbow and wrist, and if you get a response only at the elbow you have proved that an anastamosis exists. Another pitfall of nerve conduction is muscle artifact seen with antidromic stimulation (G1 is close to ADM). Solve this problem by doing orthodromics. Another pitfall is brachial neuritis masquerading as an ulnar neuropathy. Medial antebrachial cutaneous nerves are abnormal in cases of lower trunk lesions. It also puts the lesion away from a radiculopathy if abnormal. Distribution of sensory nerve fibers in hand: 100 % of ulnar fifth fibers comes from lower trunk. In index finger 100 % comes from middle or upper trunks (80/20). In thumb, 100 % come from upper trunk. Localizing a true ulnar neuropathy with, one must know common compressions are in retrocondylar groove (most common), humeroulnar arcade (Cubital tunnel), and less commonly, at exit from FCU. Other sites are Guyon's canal, deep ulnar in hand, and (proximally) axilla nd arcade of Struthers. A nerve conduction of dorsal ulnar response recorded between the fourth and fifth metacarpals, 8 cm proximal to wrist,compared to the contralateral side, is useful to differentiate between an ulnar neuropathy at the elbow and wrist. If its normal, it suggests the problem is at the wrist. The Mayo protocol is antidromics from the fifth digit, recorded11 cm proximal to wrist, above and below the elbow velocities. If velocities are <> 20 %, stimulate below elbow and upper arm. If slowing is > 8 mps or 10 % amplitude difference across the 10cm elbow segment, perform 2 cm inching. IF FDI is weak consider FDI recording. Elbow should be flexed at 90 degrees during test. Needle examination should include FDI, ADM, FDP and FCU. FCU is reached in the forearm. It flexes the wrist with ulnar deviation. However FCU may comes off either before or after cubital tunnel. The FDP comes off only after (to digits 4 and 5 is ulnar). Reach by supinating arm, wrist up, 4 finger breadths up, just ulnarly to the shaft. The ulnar fibers are superficial. he flex the dip of the 4th and 5th digits. Both FCU and FDP are C8-T1. If ulnar muscles are abnormal, check APB (C8 median) , EIP (C8 radial), and contralateral FDI. If other C8 muscles are abnormal, check paraspinals. ECU is posterior interosseous (radial) c 6-8, lower trunk extends wrist with ulnar deviation. Do if suspect lower trunk. If the lesion is in the wrist, proximal to Guyon's canal, all ulnar hand muscles will be affected, plus the antidromic DL will be prolonged with a reduced amplitude, with a normal dorsal ulnar response. Sensory loss will exist in an ulnar hand distribution. Proximal to the hypothenar branch, FDI/ADM affected, normal sensory, abnormal hypothenar EMG, normal sensation, weak interossei, lumbricals and hypothenar. Isolated deep branch in the hand, has weak interossei, lumbricals, spares ADM and sensation, reduced FDI amplitude, normal antidromic ulnar sensories, abnormal needle emg in interossei and lumbricals. Reach the latter by going to the second palmar crease, just proximal to joint, just radial to the tendon. Go too deep you'll be in opponens digiti minimi.