A 43-year-old woman says she cannot sleep due to pain and tingling affecting the first three digits of both hands. She has no problems with her legs. The patient suffers from chronic renal failure due to uncontrolled hypertension and receives hemodialysis. On examination, she has bilaterally diminished sensation over the thumb, index and middle fingers, and the radial half of her ring finger. Which of the following is the most likely mechanism of this patient's condition?

Question

A 43-year-old woman says she cannot sleep due to pain and tingling affecting the first three digits of both hands.  She has no problems with her legs.  The patient suffers from chronic renal failure due to uncontrolled hypertension and receives hemodialysis.  On examination, she has bilaterally diminished sensation over the thumb, index and middle fingers, and the radial half of her ring finger.  Which of the following is the most likely mechanism of this patient's condition?

Quizplus · Accepted Answer

11ec160b_39b2_4bda_9249_f175a9e76835_MD0001_00 Carpal tunnel syndrome (CTS) is a peripheral mononeuropathy caused by compression of the median nerve in the carpal tunnel. The carpal tunnel is an area located on the palmar surface of the wrist (between the carpal bones and transverse carpal ligament) in which the median nerve and tendons of the long flexors of the digits pass through. There is little room for expansion in this anatomical compartment. CTS is associated with conditions that reduce carpal tunnel space, including pregnancy (fluid accumulation), hypothyroidism (glycosaminoglycan buildup), diabetes mellitus (connective tissue thickening), and rheumatoid arthritis (tendon inflammation). Patients with a long history of hemodialysis can also develop median nerve compression through deposition of β2-microglobulin (dialysis-associated amyloidosis) in the carpal tunnel. Symptoms and signs of CTS often occur bilaterally and include: Sensory impairment, pain, and/or paresthesias in the median nerve distribution (palmar surface of the first 3 digits and radial half of the 4th digit). Symptoms are usually worse at night. Motor weakness during thumb abduction/opposition and thenar atrophy. Tinel sign (tapping over the flexor surface of the wrist reproduces symptoms) and Phalen sign (flexion of the wrist reproduces symptoms). (Choice A) Endomysial inflammatory infiltration is found on muscle biopsy in polymyositis, a myopathy that usually presents with proximal muscle weakness, not distal sensory symptoms as seen in this patient. (Choice B) Endoneural arteriole hyalinization can occur in diabetes mellitus (diabetic microangiopathy) and most commonly results in a distal, symmetric peripheral polyneuropathy that usually starts in the feet. However, this patient does not have diabetes and her symptoms follow a median nerve distribution, which is more likely due to compressive neuropathy. (Choice C) Endoneural inflammatory infiltration with multifocal demyelination is seen in Guillain-Barré syndrome, a demyelinating peripheral neuropathy that typically presents with ascending motor weakness. Patients with median nerve compression under the flexor retinaculum have focal, not multifocal, demyelination. (Choice D) Duchenne muscular dystrophy is an X-linked condition that occurs due to mutation or deletion of the dystrophin gene. It is a myopathy that predominantly affects young boys and presents with proximal muscle weakness and pseudohypertrophy of the calves. Educational objective: Carpal tunnel syndrome is a peripheral neuropathy characterized by pain/paresthesias in a median nerve distribution (palmar surface of the first 3 digits and radial half of the 4th digit), weakness on thumb abduction/opposition, thenar atrophy, and a positive Tinel and/or Phalen test. It is caused by median nerve compression at the transverse carpal ligament. __________ References: Carpal tunnel syndrome. (http://www.ncbi.nlm.nih.gov/pubmed/21524035)

A 43-Year-Old Woman Says She Cannot Sleep Due to Pain