Case Files Surgery, (LANGE Case Files) 4th Ed.

SECTION II. Clinical Cases

CASE 7

A 34-year-old diabetic woman complains of a 6-month history of progressive numbness and pain in her right hand that wakes her up at night. She states that her thumb is especially affected. She says that she is beginning to drop objects she is carrying in her right hand. She denies a history of trauma, exposure to heavy metals, or a family history of multiple sclerosis. The only medication she takes is an oral hypoglycemic agent.

Images What is the most likely diagnosis?

Images What is the mechanism of the disorder?

Images What is your next step?

ANSWERS TO CASE 7: Carpal Tunnel Syndrome

Summary: A 34-year-old diabetic woman complains of a 6-month history of progressive numbness and pain in her right hand occurring especially at nighttime and affecting her thumb. She states that she is beginning to drop objects she carries in her right hand.

• Most likely diagnosis: Carpal tunnel syndrome (CTS).

• Mechanism of the disorder: Median nerve compression.

• Next step in therapy: Nighttime splint and nonsteroidal anti-inflammatory drugs (NSAIDs).

ANALYSIS

Objectives

1. Learn the clinical presentation, pathophysiology, and risk factors for CTS.

2. Learn the medical and surgical options for treating CTS.

Considerations

The distribution of the progressive numbness and pain is suggestive of median nerve compression. In addition, exacerbation of the patient’s symptoms at night is typical of CTS. The mechanism of this disorder is compression of the median nerve as it passes within the carpal tunnel. This causes axonal damage and narrowing of the nerve. Median nerve compression causes numbness and pain in the thumb, index finger, and middle and lateral aspects of the ring finger. The median nerve may be compressed anywhere along its length from the brachial plexus down to the hand, but the most common site of compression is within the carpal tunnel, where it is dorsal to the transverse carpal ligament. The carpal canal is a rigid structure that causes physiologic dysfunction by producing median nerve ischemia. The best initial management is a nighttime splint for the wrist and avoidance of excess activity with the hand.

APPROACH TO: Carpal Tunnel Syndrome

DEFINITIONS

CARPAL TUNNEL SYNDROME: Median nerve compression at the wrist leading to paresthesias of the radial three fingers and sometimes hand weakness.

TINEL SIGN: Reproduction of the patient’s symptoms by percussion of the median nerve at the wrist.

ELECTROPHYSIOLOGIC STUDIES: Investigation of nerve conduction and muscle innervation.

CLINICAL APPROACH

The carpal canal serves as a mechanical conduit for the digital flexor tendons. The walls and floor on the dorsal surface of the canal are formed by the carpal bones, and the ventral aspect is confined by the strong, inelastic, transverse carpal ligament. The smallest cross-sectional area of the canal is created by extremes of flexion and extension of the wrist (Figure 7–1). Exacerbation of symptoms at night is thought to be caused by edema; tenosynovitis may also be present. CTS is associated with endocrine conditions, diabetes, myxedema, hyperthyroidism, acromegaly, and pregnancy. Other causes are autoimmune disorders, lipomas of the canal, bone abnormalities, and hematomas. The etiology is often multifactorial. Women are more commonly affected in a ratio of approximately 3:1.

Images

Figure 7–1. The carpal tunnel. The wrist in cross section reveals that the median nerve is susceptible to impingement.

Diagnosis

The diagnosis of CTS is clinical, and the symptoms are typical. The exertion of direct digital pressure by the examiner over the median nerve at the carpal tunnel frequently reproduces the symptoms in approximately 30 seconds. In the Phalen maneuver, gravity-induced wrist flexion also produces the classic symptoms of this condition. A positive Tinel sign is present when direct percussion over the nerve reproduces paresthesia. Sensory loss, particularly vibration sense, and motor loss may be present with thenar muscle wasting and decreased abductor muscle resistance. Because CTS is found bilaterally in up to half of patients, comparison to the contralateral hand can be misleading. Electrophysiologic studies may be helpful. A comparison of median and ulnar or median and radial sensory stimulation values at the wrist is useful in confirming the diagnosis. Radiographs, including a “carpal tunnel view,” are recommended to detect arthritis or fractures. CT and MRI are rarely needed; however, in the case of a symptomatic patient with equivocal EMG findings, imaging can be helpful. MR imaging has the greatest sensitivity and specificity in the evaluation of CTS.

Treatment

Conservative therapy consists of the use of splints and nonsteroidal anti-inflammatory agents. Splints should be light and hold the wrist in a neutral or slightly extended position. Local steroid injections are effective in 80% to 90% of patients, but symptoms tend to return after months or sometimes years. Injections should not be given more frequently than on two or three occasions per year. Care must be taken not to inject directly into the median nerve. Diuretics have not been shown to be efficacious. Surgery is indicated for intractable symptoms that are refractory to medical management. It consists of complete division of the transverse carpal ligament extending distally from the ulnar side of the median nerve. The results of surgery are generally good. Poor results are usually associated with either a misdiagnosis or failure to divide the ligament completely. The surgery can be performed with an open or an endoscopic approach. A tourniquet is used to exsanguinate the limb, and the operative field is infiltrated with a local anesthetic agent such as Xylocaine; in addition, intravenous sedation can be used. The Palmer fascia and the ligament are divided vertically from the proximal end of the carpal tunnel to its most distal point, and a wide separation of the ends of the ligament is observed (Figure 7–2). The underlying median nerve is carefully protected. A small tissue flap is left attached to the hook of the hamate, and the skin is closed. Postoperatively, the wrist is splinted in slight extension for approximately 2 weeks.

Images

Figure 7–2. Carpal tunnel release. The transverse carpal ligament is incised (palmar view of the wrist).

The potential advantages of the endoscopic approach are less discomfort, minimal scarring, a shorter period of immobilization, and a more rapid recovery. Persistent or recurrent symptoms should be investigated by repeated electrophysiologic studies and by exclusion of other causes of nerve compression. Occasionally, the ulnar nerve is compressed at the wrist, but more commonly, compression of this nerve occurs in the fibromuscular groove posterior to the medial epicondyle.

Prognosis

In general, conservative treatment of mild CTS is effective. In conditions that are temporary such as pregnancy, temporizing measures are common. Overall, surgery is approximately 85% effective in alleviating symptoms; however, some patients may have residual numbness of the fingers even after carpal tunnel release. Additionally, patients with advanced disease (significant motor deficits or muscular atrophy), concomitant neuropathy or diabetes, longer duration of condition, or older age group have a poorer prognosis.

COMPREHENSION QUESTIONS

7.1 A 24-year-old medical student notes some numbness and tingling of her right hand. She states that primarily her little finger is affected. Which of the following is the most likely etiology?

A. Median nerve

B. Radial nerve

C. Ulnar nerve

D. Lateral cutaneous nerve

E. Long thoracic nerve

7.2 Which of the following patients is most likely to develop CTS?

A. A 45-year-old woman with diabetes insipidus

B. A 32-year-old woman with hypothyroidism

C. An 18-year-old man with addisonian syndrome

D. A 48-year-old woman with hypertension

E. A 51-year-old woman with fibromyalgia

7.3 A 30-year-old man complains of numbness and tingling of his right thumb and index finger. He also has pain at night on the same hand. The Tinel sign is positive. He is diagnosed with CTS and given a nighttime splint. After 3 months, the symptoms have worsened. An electrophysiologic study is performed, and the results are equivocal. Which of the following is the best next step for this patient?

A. Refer to psychiatrist.

B. Question about drug-seeking behavior.

C. Refer for cervical spine surgery.

D. MRI of the wrist.

E. X-ray of the wrist.

ANSWERS

7.1 C. The sensory innervation of the little finger and the ulnar side of the ring finger is achieved with the ulnar nerve. Median nerve distribution is to the sensory aspect of the thumb, index and middle fingers on the palmar aspect.

7.2 B. Hypothyroidism (as well as diabetes mellitus, hyperthyroidism, pregnancy, and acromegaly) is associated with CTS. Diabetes insipidus is associated with loss of dilute urine and not associated with CTS.

7.3 D. When the clinical findings are present, but the EMG studies are equivocal, MR imaging can be helpful in assisting with the diagnosis. No imaging test is considered to be routinely needed in the evaluation of CTS, but in selected circumstances, it may be helpful. In mild cases of CTS, clinical examination is sufficient.

CLINICAL PEARLS

Images CTS usually involves pain to the radial three fingers, especially at night.

Images The initial treatment of CTS includes administration of NSAIDs and the use of a wrist splint.

Images Surgery is indicated when severe pain or progressive motor weakness occurs despite conservative measures.

REFERENCE

Lifchez SD, Sen SK. Surgery of the hand and wrist. In: Brunicardi FC, Andersen DK, Billiar TR, et al, eds. Schwartz’s Principles of Surgery. 9th ed. New York, NY: McGraw-Hill; 2010:1609-1645.