case? This patient has dysfunction of the thenar sensory branch (palmar cutaneous branch) of the median nerve. This arises from the main nerve approximately 5 cm proximal to the wrist and initially runs parallel to the main nerve before passing volarly to the skin. It may be compressed by localized swellings such as hematoma, lipoma, or ganglion cysts. It may also be injured following penetrating trauma to the distal forearm. Further investigation or exploration is warranted in either scenario.1,2
2. Meyer P, Lintingre PF, Pesquer L, Poussange N, Silvestre A, Dallaudière B. The median nerve at the carpal tunnel … and elsewhere. J Belg Soc Radiol 2018;102(1):17 The Arcade of Frohse refers to the proximal edge of the superficial supinator muscle and is the most common site of radial nerve compression. Radial nerve compression is much less common than ulnar or median nerve compression. The radial nerve passes through the radial tunnel, which is formed by the radiocapitellar joint bursa, the brachioradialis tendon, the extensor carpi radialis longus (ECRL) and the extensor carpi radialis brevis (ECRB) tendons, and the biceps tendon and brachialis muscle. There are three other key sites of compression and these are fibrous bands anterior to the radiocapitellar joint (just proximal to the radial tunnel), the vascular leash of Henry (which represents the radial recurrent artery), and the proximal tendon of the ECRB.1–3 Saturday night palsy is a condition with signs of a new sudden-onset radial nerve compression following prolonged pressure overnight typically with the arm resting over a chair and often associated with intoxication. This is due to compression of the radial nerve at the spiral groove of the humerus.4
3. Latef TJ, Bilal M, Vetter M, Iwanaga J, Oskouian RJ, Tubbs RS. Injury of the radial nerve in the arm: a review. Cureus 2018;10(2):e2199
4. Lotem M, Fried A, Solzi P, Natanson T. Saturday night palsy [in Hebrew]. Harefuah 1972;83(8):328 ULNAR NERVE PATHOLOGY 3. Which one of the following represents a simple test for ulnar nerve motor function? Ulnar nerve motor palsy is demonstrated by the inability to cross the index and middle fingers or to deviate the extended middle finger ulnarly or radially when the hand is placed on a flat surface. Both of these tests are quick and simple to perform in clinic. These clinical findings are because the intrinsic muscles (dorsal and palmar interossei) are paralyzed. In addition, the flexor digitorum profundus (FDP) to the little and ring fingers may be affected, depending on compression/injury level. Making a thumb’s-up sign relies on radial nerve innervation of the extensor pollicis longus, extensor pollicis brevis (EPB), and abductor pollicis longus (APL). The “OK” ring sign requires anterior interosseous nerve innervation of the flexor pollicis longus (FPL) and FDP index finger. Thumb abduction requires innervation of the abductor pollicis brevis by the median nerve.1–3
Carpal tunnel syndrome is a compression neuropathy of the median nerve at the wrist within the carpal tunnel. Surgical treatment is most commonly an open release of the transverse carpal ligament. More than 90% of patients with confirmed carpal tunnel syndrome will have an improvement in their symptoms after adequate median nerve decompression. Carpal tunnel syndrome represents the most common upper extremity compression neuropathy and prevalence is estimated to be between 3 and 4%.1 The condition is not restricted to adults, as children can occasionally develop carpal tunnel syndrome too. The main concern in children is that symptoms tend to present late, often with bilateral disease and established thenar wasting. It is treated in the same way as adult carpal tunnel syndrome. In addition to altered sensation in the radial three digits, the radial border of the ring finger is also commonly affected by sensory changes. The thenar eminence is spared because the palmar cutaneous branch is given off proximal to the carpal tunnel. The main reported advantages of endoscopic carpal tunnel release are an earlier return to work and reduced scar sensitivity; however, there are higher rates of neuropraxia and of recurrent symptoms as a result of incomplete release.1,2
Neutrally positioned wrist splints can be very effective for relieving symptoms of carpal tunnel syndrome and are usually tolerated best at night. In mild to moderate carpal tunnel syndrome, many patients may choose to avoid surgery after a trial of splint therapy. Splints may also help with symptom management while a patient is waiting for surgery. If splints are helpful but are difficult to tolerate, steroid injection into the tunnel may be an effective alternative to surgery for some patients. However, only around one-fifth of patients will have a sustained improvement in symptoms after a steroid injection. The frequency of carpal tunnel syndrome in keyboard workers with variable intensity of use has been reviewed and found to be most common in workers with low-intensity keyboard activity.1 Obesity is recognized as a common association with carpal tunnel syndrome, along with pregnancy, diabetes, and thyroid disorders.2 Although forearm discomfort is not a classic feature of carpal tunnel syndrome, many patients experience this. Following carpal tunnel release, many such patients report improvement in their pain symptoms. This is thought to be a result of the “multiple crush phenomenon” in which there are multiple additive insults influencing axonal transport along the length of a nerve.3 Relieving one factor may sufficiently improve overall nerve function such that symptoms relating to other segments of the nerve are also improved. This is not a predictable outcome and patients should not be led to expect an improvement in symptoms, which are not directly attributable to compression of the median nerve at the wrist following carpal tunnel release. However, in a patient with coexisting nerve root or thoracic outlet nerve compression and peripheral nerve compression, it is prudent to relieve the peripheral compression in the first instance, as this may give sufficient relief to obviate the need for more complex proximal surgery.3
Pronator syndrome is a nerve compression affecting the median nerve in the forearm. It presents with forearm and hand pain, paresthesia, and hypoesthesia including the thenar eminence. It is often worse during resisted flexor digitorum superficialis (FDS) contraction, particularly of the middle finger. This is because the compression commonly occurs proximally within the forearm at the fibrous arch of FDS. Other key sites of compression include pronator teres (not pronator quadratus, which is deep at the wrist), the ligament of Struthers (ligament between the distal humerus and pronator teres fascia) just proximal to the elbow, and the bicipital aponeurosis (lacertus fibrosus) at the elbow. Compression may also be due to abnormal vasculature in the distal forearm. Pronator syndrome is predominantly a sensory pathology with no motor weakness usually evident. Occasionally, however, there may be additional signs of weak flexion of the thumb and index finger. Diagnosis is confirmed by history and examination which can show increased tingling on elbow flexion, forearm pronation, resisted FDS contraction, and tapping over the pronator teres. Surgical decompression is usually very successful with resolution of symptoms.1–3
The anterior interosseous nerve is a branch of the median nerve that supplies the radial slips of the FDP, FPL, and pronator quadratus. Compression of the nerve is therefore characterized by loss of thumb flexion at the interphalangeal (IP) joint and index/middle finger distal interphalangeal (DIP) joint flexion. Cutaneous sensation is unaffected. Compression can occur at the tendinous edge of the pronator teres (deep head) or the tendinous origin of the FDS. However, there is also the possibility of other noncompressive causes such as an inflammatory cause (amyotrophy). Diagnosis involves clinical assessment of pinch strength and the OK sign. Nerve compression and EMG studies are often useful. Surgical decompression with neurolysis at the antecubital fossa and proximal forearm is considered by some to be highly effective but may not always be so. For example, a study reviewing a case series of 16 patients found that resolution of symptoms following decompression was similar to patients who were managed nonoperatively, and the authors suggested that surgery should be restricted to those patients with isolated and complete anterior interosseous motor loss that is persistent at 6 months.1
The motor branches to the ECRL usually arise before the radial nerve splits around the supinator muscle into the posterior interosseous nerve (PIN) and the superficial radial nerve. Therefore, following an injury or compression at or around the region of the supinator muscle (such as a dislocation of the radial head), there is likely to be preservation of some wrist extension as a result of ECRL function. More proximal injuries to the radial nerve, such as secondary to a humeral shaft fracture or posterior dislocation of the shoulder, would be likely to affect brachioradialis, ECRL +/− triceps function as well. Plating of a distal radius fracture should not cause a loss of digital or wrist extension as a result of nerve injury, as the muscles will have been innervated proximal to this level. There could, however, be direct injury to the extensor tendons.1,2
Patients with radial tunnel syndrome experience pain in the proximal forearm on movement at the elbow, wrist, or digits similar to tennis elbow, with radiation distally to the dorsum of the hand. There is often tingling of the hand and a secondary weakness of grip due to pain. The pain is typically more distal to that of lateral epicondylitis and is described as being induced by resisted middle finger extension. Medial epicondylitis or golfer’s elbow is similar but affects the ulnar aspect of the forearm. Anterior interosseous syndrome is a motor condition with weakness of the FPL and FDP to index. Posterior interosseous syndrome is predominantly a motor weakness with difficulty extending the wrist and digits because of nerve compression or traction neuropraxia along the path of the nerve in the forearm. Pain can be a feature, but normal sensation is preserved. Wartenberg’s syndrome involves pain over the radial aspect of the hand and wrist due to compression of the superficial radial nerve. There is no motor weakness.1,2
Wartenberg’s syndrome is compression of the superficial radial nerve as it emerges from beneath brachioradialis, resulting in pain and paresthesia to the dorsoradial aspect of the hand and wrist. On examination, there will usually be a positive Tinel’s sign over the superficial radial nerve proximal to the radial styloid. Differential diagnoses include intersection syndrome, which is tenosynovitis caused by friction between the tendons of the first and second extensor compartments (APL and EPB over ECRL and ECRB). Initial treatment includes splinting, activity modification, and steroid injections. These modalities may be sufficient for most patients. Some patients may go on to benefit from surgical release of the surrounding fascia. Motor function of the index and thumb will be preserved in Wartenberg’s syndrome.1 In contrast, this function will be reduced in PIN compression. The PIN is primarily a motor nerve to the extensor compartment of the forearm with no cutaneous sensory supply. However, patients may complain of unpleasant sensations or pain in the forearm or wrist due to the nociceptive and proprioceptive roles of the PIN. Sensation will be preserved over the fifth MCP joint dorsally in either condition, as this is ulnar nerve territory. The inability to adduct the little finger is called Wartenberg’s sign and is due to ulnar nerve palsy with intrinsic muscle weakness, which leaves the slightly abducting line of pull of the EDM tendon unopposed.
The vascular leash of Henry is formed by the radial recurrent artery in the antecubital fossa and is a potential site of radial rather than ulnar nerve compression. The other sites are all potential places for the ulnar nerve to be compressed during its course in the arm. The five potential sites of compression affecting the ulnar nerve at the elbow are, from proximal to distal: 1. Medial intermuscular septum 2. Arcade of Struthers 3. Ligament of Osbourne 4. Proximal fascia between the two heads of FCU 5. Fascial bands within the FCU tunnel Preoperatively, to justify this exploration, the patient would be expected to have symptoms and signs of ulnar nerve compression that are not responding to nonoperative care, usually supported by NCS/EMG findings. Symptoms and signs include ulnar-side forearm tingling and pain extending to the ulnar half of the ring finger, the entire little finger, and the ulnar dorsal half of the hand. This may be associated with weakness +/− atrophy of the ulnar forearm and finger flexors and the hand intrinsics.1
The results of ulnar nerve decompression at the elbow are less predictable than those following median nerve decompression at the wrist. There is considerable debate regarding the optimal surgical intervention,1 with many preferring to perform a simple in situ decompression in the first instance and reserve transposition procedures for recurrent cases. Others are strongly in favor of medial epicondylectomy as the primary surgical procedure. Where epicondylectomy is preferred, a partial bony resection is undertaken, rather than complete resection of the epicondyle, to reduce the risk of valgus instability of the elbow following surgery. In recurrent cases, submuscular nerve transposition may be indicated2,3; however, this is not common, and many surgeons prefer a subcutaneous transposition4 if the nerve is to be relocated. An intramuscular pocket is also described. Submuscular transposition is more complex to perform than a subcutaneous pocket and has a much longer recovery period while the divided flexor-pronator mass heals. Both transposition procedures require great care to ensure that new areas of tension and compression along the nerve are avoided throughout the range of elbow motion, e.g., by resection of components of the intermuscular septum and FCU fascia. Although some patients find splinting of the elbow helpful, this prevents elbow flexion and interferes with activities and is therefore used only at night and generally less well tolerated than splinting in carpal tunnel syndrome. In severe ulnar nerve compression, splinting has not been shown to be beneficial, and surgery should not be delayed by a trial of conservative therapy.
One of the recognized causes of ulnar nerve compression in Guyon’s canal is an aneurysm of the ulnar artery, as can occur in occupations such as carpentry as a result of repetitive motion (hypothenar hammer syndrome). However, there are many potential causes, including a ganglion, lipoma, fracture of the hook of hamate, and synovial inflammation. Thus, plain radiographs, ultrasound with or without Doppler imaging, and even CT/MRI can be important to determine the specific cause before surgery, as the management may involve more than a simple decompression. If there is an aneurysm, the involved segment of the artery will be resected and replaced with a vein graft; so, the patient must be warned about a donor-site scar and the possibility of ischemic complications. Guyon’s canal can be superficially decompressed at the same time as a carpal tunnel release through the same incision. Alternatively, a more ulnar incision can be used in order to more easily access and release the deep motor branch. A standard carpal tunnel release can alter the shape of Guyon’s canal and reduce ulnar nerve compression without any direct dissection.1,2 Ulnar nerve compression in Guyon’s canal may present with mixed or isolated motor or sensory signs due to the branching pattern of the nerve at this site (Fig. 92.1). In zone I, the ulnar nerve has not yet bifurcated and there will be motor and sensory disturbance. In zone II, the deep motor branch is affected in isolation. In zone Fig. 92.1 Zones of ulnar nerve compression within Guyon’s canal. III II I III, only the superficial sensory branch to the hypothenar skin and ulnar one and a half digits are affected. Zone III compression is the least common.
In this scenario, the patient is exhibiting Wartenberg’s sign, which has nothing to do with Wartenberg’s syndrome. Wartenberg’s sign is abduction of the little finger caused by intrinsic muscle weakness that leaves the abducting force of the EDM unopposed. The weak grip is also in keeping with ulnar nerve palsy, the most common cause of which would be cubital tunnel syndrome. Radial tunnel syndrome would present with pain during movement at the elbow secondary to radial nerve compression in the proximal forearm. Pronator syndrome results in proximal forearm pain with paresthesia over pronator teres, extending distally onto the thenar eminence and radial digits. It is caused by median nerve compression in the forearm. Ulnar tunnel syndrome refers to ulnar nerve compression within Guyon’s canal at the wrist/hand. Patients present with ulnar sensory and/or motor deficits in the hand. Wartenberg’s syndrome is compression of the superficial radial nerve in the proximal forearm. This leads to pain and numbness to the dorsal radial aspect of the distal forearm and hand.1,2