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Introduction
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Injuries to ulnar nerve are common. In up to 20% of peripheral nerve
injuries, the ulnar nerve is implicated. Three-quarters of these injuries
occur in the superficial portion of the ulnar nerve behind the medial
epicondyle.
Anatomy
The ulnar nerve arises from the medial cord of brachial plexus
(ventral rami C8 T1 roots). It descends along the medial side of the axillary
and brachial arteries in the anterior compartment of the arm. At the mid
portion it pierces the medial intermuscular septum and passes behind the
medial epicondyle of the humerus. It then enters the anterior compartment
of the forearm and descends behind the flexor carpi ulnaris medial to
the ulnar artery. At the wrist it passes anterior to the flexor retinaculum
and lateral to the pisiform bone. It then divides into superficial and
deep terminal branches. The ulnar nerve does not give off any branches
in the upper arm. It is predominantly a motor nerve but also has a small
autonomic and sensory supply to the ulnar side of the hand.
Its branches in the forearm supply the flexor carpi ulnaris and the 4th
and 5th digitation of the flexor digitorum profundus. In the hand its
superficial branch supplies flexor pollicis brevis and palmaris brevis
muscles besides providing sensory innervation to the dorsal aspects of
3rd, 4th and 5th digits. Its deep branches supply erector pollices, interossei,
the 5th digitations of abductor digiti minimi, digitation of flexor digitorum
and opponens digitorum along with 3rd and 4th lumbricles.
Muscles most often affected by a lesion to the ulnar nerve include flexor
carpi ulnaris, abductor pollicis, palmar interossei, abductor digiti and
opponens digitorum.
Ulnar nerve is most often implicated either along the ulnar sulcus around
the medial epicondyle where it is often surrounded by a tendinous arch
between the two heads of flexor carpi ulnaris. The arch can be connected
to the olecranon and medial epicondyle of the humerus to form the cubital
tunnel. The other physiologic narrowing called Guyon tunnel extends from
the pisiform bone to the transverse carpi ligament. This ligament is also
called the Palmar carpi ligament. At this it divides into superficial
and deep branches accompanying the ulnar arteries.
Location and types of lesions
| a. |
The upper arm - This is rare and often leads to complete
paralysis of all muscles innervated by the ulnar nerve. The metacarpophalangeal
joints become hyper extended and the inter phalangeal joints become
flexed. This is most severe in the 4th and 5th digits as the support
in the extension by the median nerve innervating lumbricles is only
available in the 2nd and 3rd digits. There is also slight abduction
of the 4th and 5th digits. This is also known as Wartenberg sign.
There may be atrophy of the 1st interossei and hypothenars muscles.
There is also loss of sensation in the skin over the ulnar side.
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| b. |
The cubital tunnel - The ulnar nerve can be implicated either due to the supracondylar fracture of the humerus or direct damage to the nerve as a result of trauma. External pressures on the nerve or staying in bed with pressure on the nerve can all lead to signs and symptoms of nerve injury. Morphological displacement of the elbow due to systemic disease, ie. arthropathy, syringomyelia, subluxation or fractures can lead to the narrowing of the tissue structures causing ulnar paralysis.
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| c. |
Lesions in the wrist and distal forearm - Injury to the nerve in this area can lead to paralysis of abductors and adductor of the fingers, paresis of the hypothenar muscles, pollicis brevis and adductor pollicis muscles. There is no loss of sensibility of the dorsal and ulnar side of the forearm. This condition can also result from traumatic compression or idiopathic aneurysms of the ulnar artery.
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| d. | Lesions in the Guyon tunnel - The nerve can be implicated either at the entrance into the Guyon tunnel leading to paresthesia over 4th palmar interossei muscles and sensory loss along the ulnar side of the hand. In another case of lesion in the Guyon tunnel, the profundus muscles could be involved with no loss of sensibility. Weakness also occurs in abductors and adductors of the fingers as well as paresis of the adductor pollices and flexor pollices. The nerve can also be involved at its exit from the Guyon tunnel when it does not result in any weakness. There is, however, palmar paresthesia along the ulnar side of the 4th and 5th digits. Damage to the ulnar nerve in the Guyon tunnel can either result from trauma, ie. carpometacarpal dislocation, fractures of the carpal bones, or external pressure from chronic heavy use by the karate sportsmen. The cyclist, compression workers or joystick abusers can also present with signs and symptoms of ulnar nerve problems. In long standing cases the hand assumes the characteristic of a claw deformity. |
Wichtigste Lasionsstellen des N. ulnaris
1. Lasion am Oberarm
2. Sulcus n. ulnaris - Syndrom
3. Lasion an Handgelenk und distalen Unterarm
4. Lasion in der Loge de Guyon
Summary diagram of main branches of ulnar nerve |
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Literature
| 1. | Assmus RM, Hamer J: Die distale Nervus - ulnaris - Kompression. Syndrom der "loge de Guyon" und des Ramus prof. n. ulnaris. Neurochirur 1977, 20: 139-144 |
| 2. | Bonney G: Iatrogenic injuries of nervies. J Bone Surg 1986, 68b: 9-13 |
| 3. | Cavallo M, Poppi M, et al: Distal ulnar reuropathy from carpal ganglia: a clinical and electrophysiological study. Neurosurg 1988, 22: 902-905 |
| 4. | Dellon AL: Review of treatment results for ulnar nerve entrapment at the elbow. J Hand Surg Am 1989, 14a: 688-700 |
| 5. | Dellon AL, Hament W, et al: Nonoperative management of cubital tunnel syndrome. An 8-year prospective study. Neurol 1993, 43: 907-911 |
| 6. | Eisen A, Dannon J: The mild cubital tunnel syndrome. Its natural history and indications for surgical intervention. Neurol 1974, 24: 608-613 |
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| 8. | Greenberg MS: Handbook of Neurosurgery (Vol. 1) 1997. Lakland Florida |
| 9. | Krayenbuhl H: Die ulnarisspatlahmung nack fraktur des condylus humeri lateralis. A Unfallmed Berufsheilk 1946, 39: 49-53 |
| 10. | Kukoswski B: Distale unarislasion durch joystick-benutsung. Akt Neruol 1992, 19: 85-86 |
| 11. | Miller RG: The cubital tunnel syndrome. Diagnosis and precise localisation. Ann Neurol 1979, 6: 620-622 |
| 12. | Mummenthaler M: Die ulnarisparesen. Thieme, Stuggart 1961 |
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| 14. | Mummenthaler M, Schliack H: Lasionen peripherer nerven. Thieme, Stuggart 1993 |
| 15. | Osborne G: Compression neuritis of the ulnar nerve at the elbow. Hand 1972, 2: 10-16 |
| 16. | Scherzer E: Nervenschadigung bei ellenbogenbruchen - statistisch betrachtet. H Unfallheilk 1973, 114: 101-107 |
| 17. | Shea JD, McClain EJ: Ulnar nerve compression syndromes at and below the wrist. J Bone Surg 1969, 51a: 1095-1103 |
| 18. | Spinner M, Spencer PS: Nerve compression lesions of the upper extremity: a clinical and experimental review. Clin Orthop 1974, 104: 46-67 |
| 19. | Stolke D, Seidel BU, Schliak H: Das syndrome der loge de guyon oder die ulnarisparese an handgelenk unter bevorzugung des ramus profundus. Akt Neurol 1980, 7: 161-165 |
| 20. | Tackmann W, Richter HP, et al: Kompression syndrome peripherer nerven. Springer, Heidelberg, New York 1989 |
| 21. | Teichner M: Aufklarung uber mogliche lagerungsschaden. Dtsch med Wschr 1991, 116: 273-274 |
| 22. | Wassmann H, Moskopp D, Lasion des N. ulnaris in verbindung mit lumbaler bandscheibenoperation. MedR 1993, 2: 63-64 |
| 23. | Willis BK: Cubital tunnel syndrome in: Benzel EC (Editor): Practical approaches to peripheral nerve surgery. Park Ridge, Illinois 1992 |
| 24. | Woischneck D, Rosenthal H, et al: Ulnarissirritation beim Nail-patella-syndrome. Akt Neurol 1993, 20: 25-27 |
Prof. Dr. Dietmar Stolke
Neurosurgery Clinic & Policlinic
Essen University
HafelandstraBe 55
D-4300 Essen 1
Germany
