Nerve Entrapment Syndromes 1091
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1090 Part VIII Septic and Nontraumatic Conditions may present with well-defi ned symptoms of ulnar CHAPTER 80 nerve compression at the elbow; electrical studies, however, may have normal results in the ulnar nerve but reveal changes of carpal tunnel syndrome (which Nerve Entrapment may be either subclinical or less symptomatic to the patient). Post-traumatic thickening of the brachial Syndromes fascia in the distal arm can produce a simultaneous median and lateral antebrachial nerve compression. When more than one nerve is suspected in the neural Robert J. Spinner compression process, a more proximal lesion such as the brachial plexus, must be ruled out as the site of the pathologic process. 2. A nerve can be compressed at more than one level; INTRODUCTION that is, a “double crush” lesion may exist. This most commonly occurs at the neck and the wrist but can The diagnosis of a nerve entrapment lesion arising at also occur at other locations such as the thoracic the elbow can be relatively straightforward if the history, outlet and the cubital tunnel. physical examination, electromyographic (EMG), and 3. Two separate neurologic processes may coexist. For imaging studies, when indicated, all confi rm the diagno- example, a patient who is wheelchair-bound from a sis and the localization of the lesion.12,32,47,87,93,138 However, syrinx may develop hand atrophy, which represents when the history and physical examination do not cor- new bilateral ulnar nerve compression rather than respond or the electrophysiologic or imaging studies do progression of the syrinx. Thus, on occasion, it is nec- not support a specifi c clinical diagnosis, then problems essary to direct one’s conservative or surgical atten- can arise. Therefore, one must apply the same system- tion to two nerves, two sites on one nerve, or even atic, thoughtful approach to the care of every patient. two neurologic conditions to address the patient’s One can then put all of the data of the clinical puzzle presenting symptoms and new neurologic fi ndings. together to offer appropriate treatment. Sometimes, historical information can be misleading. Some patients are prone or predisposed to sequential For example, it is not uncommon for an elderly patient neural compression lesions. There are predisposing to say that his or her fi ngers are “stiff” when in reality factors for multiple neural entrapment lesions. A group the fi ngers are numb. Stiffness suggests an arthritic of substances, such as sorbitol, can cause an increase in process, whereas numbness suggests involvement of the intrafascicular pressure, which can predispose a patient peripheral neurologic system in the pathologic process. with diabetes mellitus to a neural compression lesion. Other times, physical fi ndings may be diffi cult to Hereditary neuropathies also occur; despite genetic interpret. Persistent pain about the lateral aspect of the advances, the mechanism of dysfunction is not fully elbow that is resistant to all forms of conservative treat- understood. Congenital anomalies of the elbow, such as ment as well as operative treatment directed to the lateral from a lacertus fi brosus variant or a ligament of Struthers, epicondyle may represent resistant lateral epicondylitis, may result in nerve compression lesions. Developmental entrapment of the posterior interosseous nerve alone, or changes from hypertrophied muscles may lead to com- both entities. In this instance, EMG studies, more com- pressive neuropathies, such as a pronator syndrome in monly than not, do not help establish the diagnosis of an athlete. Trauma may induce a nerve compression resistant “tennis elbow” due to posterior interosseous syndrome either acutely or chronically, either from nerve compression or localize the pathologic process. If bony or associated soft tissue changes. both conditions are believed to be present on clinical Recurrent neural compression lesions also occur. A grounds, then management of both lesions needs to be physician may successfully care for an individual’s addressed simultaneously to relieve the patient’s neural compression only for another nerve compression symptoms. to arise a few months or years later that affects the same Other issues may confound the clinical picture and peripheral nerve or another nerve.132,139,198 Usually, tech- the treating physician: nical factors at surgery can prevent recurrent lesions. Free gliding of the nerve with elbow fl exion and exten- 1. Simultaneous peripheral nerve compressions may sion and forearm rotation helps prevent late postopera- occur, whether from related or unrelated causes.25 For tive symptoms. If a nerve is fi xed by adhesions or example, a diabetic patient may present with symp- scarring or at a fracture site, it is not just a matter of toms related to concurrent carpal tunnel syndrome entrapment. A traction neuritis can exist as well. As the and cubital tunnel syndrome. An active individual joint moves, the nerve is tethered and can be stretched. Chapter 80 Nerve Entrapment Syndromes 1091 If the ulnar nerve is transposed anteriorly (especially if during ulnar nerve transposition and median nerve it has not been transposed in a straight line), ulnar decompression, and the posterior cutaneous nerve of neuritis can develop at a later date. Similarly, if the the forearm is at risk with posterior interosseous nerve medial epicondyle is resected and the nerve becomes neurolysis. In the majority of cases of nerve compres- adherent to the medial epicondylectomy site, resistant sion, external neurolysis is the usual operative interven- ulnar nerve neuritis can develop after the primary tion. Internal neurolysis, when indicated, should be surgery. limited to the neural segment and the internal region Certain principles apply to the surgical management clinically involved. The perineurium should rarely, if of entrapment lesions. Wide exposure is often necessary ever, be violated. Nerves should be placed in healthy to defi ne the normal anatomy and the pathologic region. beds away from scar tissue. Intraoperative nerve action The nerve should be identifi ed in a healthy region potentials may help in the management of more proximally and distally both grossly and microscopi- advanced lesions. Postoperative care should emphasize cally; only then should the nerve be traced to the early mobilization. Early motion can improve neural pathologic region. Surgery should be guided by the use gliding. The development of a stiff joint can undo an of internervous planes, and gentle handling of the nerve otherwise successful nerve decompression. is critical. During the wide decompression, care must be A detailed understanding of the complex normal given to the cutaneous nerves. Patients who have anatomy of this region and the “common” variants is entrapment lesions are prone to develop symptomatic essential for proper diagnosis and treatment of these postoperative skin neuromata; their initial symptoms conditions (Fig. 80-1). Careful history, serial examina- related to the nerve compression lesion may disappear tions and EMG studies, and at times, imaging modalities postoperatively to be replaced by a different type of can usually localize the lesion or lesions. Early, accurate neuromatous pain. In particular, at the elbow level, the diagnosis and treatment are important for effective medial cutaneous nerve of the forearm is susceptible overall management of nerve compression lesions. Biceps and bicipital aponeurosis Brachialis Median n. Radial n. Brachial a. Pronator teres, Brachioradialis humeral head Radial recurrent a. Flexor carpi radialis and palmaris longus Deep and superficial Pronator teres, ulnar head branches of radial n. Ulnar n. Supinator Ant. and post. Extensor carpi radialis ulnar recurrent aa. longus Ulnar a. Common Flexor digitorum interosseous a. superficialis Posterior and anterior Pronator teres interosseous aa. Anterior Radial a. interosseous n. Flexor carpi ulnaris Flexor pollicis Flexor digitorum longus profundus Dorsal branch of ulnar n. Ant. interosseous a. and n. FIGURE 80-1 Major neurovascular and Pronator quadratus Ulnar a. and n. muscular relationships of the elbow region. Abductor pollicis Median n. (Redrawn from Hollinshead, W. H.: Anatomy longus for Surgeons, 3rd ed. Vol. 3. New York, Harper & Row, 1982.) 1092 Part VIII Septic and Nontraumatic Conditions Understanding the degree of nerve injury can help There appear to be several types of fi rst-degree injury. a physician predict recovery patterns and guide These lesions are correlated best when both the nerve management. fi ber pathologic processes and the clinical recovery fol- lowing neurolysis are analyzed temporally. There are ionic96 and vascular40,109,117 lesions of nerve fi bers that NEUROPHYSIOLOGY OF NERVE respond to release by prompt recovery within, at times, COMPRESSION LESIONS hours of surgery. There is a structural fi rst-degree lesion, described by Gilliatt and colleagues64 and Ochoa,136 in Nerve compression may be categorized as fi rst-, which there is segmental injury to the nerve fi ber con- second-, third-, or fourth-degree neural lesions. This sisting of segmental demyelination and remyelinization method was fi rst described by Sir Sydney Sunderland.184 of just a few nodal segments of the fi bers. In this The earlier classifi cation of Sir Herbert Seddon (1943)157 instance, the entire recovery process takes 30 to 60 days. uses the terms neurapraxia, axonotmesis, and neurotmesis and The clinical implications of this particular lesion are as can be correlated with Sunderland’s classifi cation in the follows: whether the lesion is high or low in the nerve, following manner. A fi rst-degree lesion is a neurapractic it takes 30 to 60 days for neural function to be lesion. A second-degree or mild third-degree lesion is restored. an axonotmetic lesion. The neurotmetic lesion encom- In contrast, in the second-degree lesion of nerve passes all of the fourth-degree lesions (the neuroma in compression, there is degeneration from the point of continuity) and the advanced third-degree lesions. I injury distally. Regeneration of the nerve fi bers occurs prefer using Sunderland’s classifi cation when correlating within the intact basement membrane.