However, similar findings can be seen in ulnar neuropathy at the elbow. It is suggested that the fibers destined for the FCU, PUC, and DUC lie in individual fascicles at the elbow in a deep dorsolateral position, rendering them less susceptible to damage. Sensory symptoms involving the fifth digit and medial half of the fourth digit may indicate an ulnar neuropathy at the wrist. Unless it is associated with an acute injury to the elbow, pain is not a dominant feature however, some patients may complain of pain due to overuse of the forearm flexors such as the FCU. It is usually associated with elbow flexion, particularly at night. The patient may have numbness and paresthesia, radiating distally to the ulnar aspect of the hand, the fifth digit and the ulnar aspect of the fourth digit. Symptoms of ulnar neuropathy at the elbow usually start slowly unless it is associated with trauma. Repetitive movement that exerts pressure on the ulnar wrist and hypothenar eminence predisposes the ulnar nerve to develop neuropathy. Wrist fractures and compressive mass lesions may also cause ulnar neuropathy at the wrist (UNW). In contrast, the pressure was less than 19 at elbow extension. In a study investigating patients with UNE, the pressures recorded between the ulnar nerve and overlying arcade increased up to above 200 mm Hg in elbow flexion or during isometric contraction of the flexor carpi ulnaris muscle. In some individuals, the ulnar nerve may be subluxed out of the retroepicondylar groove medially over the medial epicondyle during elbow flexion. Repetitive elbow flexion and extension, arthritic changes, and valgus deformities at the elbow increase its vulnerability to injury. At the elbow, the ulnar nerve lacks protective cover in the ulnar groove. This causes its susceptibility to external compression. The second most common upper extremity entrapment neuropathy is ulnar neuropathy at the elbow (UNE). The deep palmar branch gives motor innervation to the adductor pollicis, the deep head of the flexor pollicis brevis, the third and fourth lumbricals, and the three palmar and four dorsal interossei muscles. Before the nerve exits through the pisohamate hiatus, the motor fibers branch off from the deep palmar motor branch to innervate the hypothenar muscles (abductor digiti minimi, flexor digiti minimi, opponens digiti minimi, and palmaris brevis). The superficial sensory branch provides sensory innervation to the palmar aspects of the medial half of the fourth digit and the fifth digit. In the canal, the nerve separates into the superficial sensory branch and the deep palmar motor branch. A thick band is formed at the outlet (pisohamate hiatus) connecting the hook of the hamate to the pisiform bone. The roof is formed by the palmaris brevis muscle, and the floor is formed by the combination of the transverse carpal ligament, the hamate, and the triquetrum bone. The proximal wall of Guyon’s canal is formed by the pisiform bone and the distal wall by the hook of the hamate. The main trunk of the ulnar nerve enters through the Guyon’s canal at the level of the distal wrist crease. Distal to the bifurcation of the PUC, the dorsal ulnar cutaneous (DUC) branch separates from the main trunk, curves around the ulna, and provides sensory innervation to the dorsum of the skin of the medial hand, medial half of the fourth digit, and fifth digit. At the mid to distal forearm, the palmar ulnar cutaneous branch (PUC) splits from the ulnar nerve and enters the hand ventral to the Guyon canal and gives sensory innervation to the skin at the hypothenar area. At the forearm, it innervates the FCU and the flexor digitorum profundus (FDP). The nerve then passes through the belly of the FCU muscle and out through the deep flexor-pronator aponeurosis. The area beneath the HUA is also called the cubital tunnel. It then passes underneath the humeroulnar aponeurotic arcade (HUA), which is a dense aponeurosis between the tendon attachments of the flexor carpi ulnaris (FCU). Just above the elbow, the ulnar nerve courses posteriorly to pass through the retroepicondylar groove between the medial epicondyle and olecranon process. The ulnar nerve then courses along the upper arm medial to the brachial artery, in proximity to the median nerve. The C8 and T1 nerve roots merge to form the lower trunk of the brachial plexus which continues as the medial cord to give rise to the ulnar nerve. Prevention of compression and early diagnosis/treatment is important for its prognosis because the treatment outcome is usually disappointing once the nerve has axonal damage. Although the elbow is the most common site of compression, the ulnar nerve is also susceptible to injury at the wrist, forearm, and upper arm. The ulnar nerve has several potential compression sites along its course.
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |