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1
Question:

A 48-year-old man comes to the office due to pain in his right hand.  He has had symptoms intermittently for the past year, but they have become worse over the past 3 months, particularly at night.  The pain radiates to the anterior aspect of the forearm.  Medical history is notable for type 2 diabetes mellitus; his most recent hemoglobin A1c was 8.5%.  The patient does not use tobacco, alcohol, or recreational drugs.  He works at a retail supermarket where he is responsible for stocking heavy canned goods.  Blood pressure is 148/95 mm Hg, pulse is 76/min, and respirations are 12/min.  BMI is 32 kg/m2.  On examination, the patient appears comfortable.  There is weakness of thumb opposition and slightly decreased light touch sensation over the palmar surface of the tip of the thumb, index finger, and middle finger.  Sensation is normal elsewhere.  Which of the following is the most likely cause of this patient's symptoms?

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Explanation:

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Carpal tunnel syndrome

Risk factors

  • Obesity
  • Pregnancy
  • Diabetes mellitus
  • Hypothyroidism
  • Rheumatoid arthritis
  • End-stage renal disease/hemodialysis

Clinical presentation

  • Pain & paresthesia in median nerve distribution (first 3½ digits)
  • Positive Phalen, Tinel, or Durkan (carpal compression) test
  • Severe disease: weakness of thumb abduction & opposition, atrophy of thenar eminence

Confirmatory test

  • Nerve conduction studies

Treatment

  • Wrist splinting
  • Glucocorticoid injection
  • Surgery for severe or refractory symptoms

This patient has pain and decreased sensation in the hand, consistent with carpal tunnel syndrome (CTS).  CTS is caused by compression of the median nerve as it passes deep to the flexor retinaculum in the wrist and is common in patients with diabetes mellitus, as well as in individuals with repetitive, forceful use of the wrist and hand.

Manifestations of CTS include paresthesia, pain, and sensory loss in the palmar aspect of the first 3 digits and sometimes in the lateral aspect of the fourth; patients may also have referred pain to the lateral palm, forearm, or even upper arm.  However, because the palmar cutaneous branch of the median nerve passes outside the carpal tunnel, sensation over the thenar eminence typically remains intact.

In the clinic, symptoms may be provoked by percussion (Tinel test) or manual compression (Durkan test) over the nerve, or by forceful flexion of the wrist (Phalen test).  Early CTS typically has an intermittent course with symptoms often worse at night.  However, manifestations can be highly variable, particularly with severe disease.  As the disorder progresses, symptoms may become persistent and/or associated with motor features (eg, thenar atrophy, weakness of thumb abduction and opposition).

(Choice A)  Complex regional pain syndrome causes pain in a regional (vs specific peripheral nerve) distribution.  It typically follows trauma or surgery and is associated with edema, vasomotor signs, and trophic changes in skin and hair.

(Choice B)  Multiple sclerosis is caused by focal demyelination in the white matter.  Clinical features (eg, sensory disturbances, incontinence, optic neuritis) are intermittent and progressive, and occur in multiple neural distributions.

(Choice C)  Glycosylation of proteins in the vasa nervorum leads to diabetic peripheral neuropathy.  It causes pain in the extremities but usually occurs in a stocking-and-glove pattern; findings tend to be most prominent in the feet.

(Choice E)  Median nerve compression in the forearm (eg, pronator teres syndrome) can cause forearm pain and sensory loss in the palmar aspects of the first 3 digits; however, additional sensory loss over the lateral palm and thenar eminence would be expected due to involvement of the palmar cutaneous branch.

Educational objective:
Carpal tunnel syndrome is caused by compression of the median nerve at the wrist.  It initially has an intermittent course, but with progression, the symptoms may become more persistent and associated with motor features.  Pain may radiate to the forearm or upper arm, but sensory loss in these areas is not seen.