A physician-validated, board-style question from the Active Transport QBank. Try it, then check the reasoning for every option.
A 27-year-old young man presents to his primary care physician for weakness and tingling in his hand. The patient is an avid bodybuilder and has noticed that his grip strength has gradually worsened in both hands with symptoms worse at the end of a long workout. The patient has a past medical history of anabolic steroid use in high school. His current medications include a multivitamin, fish oil, and whey protein supplements. On physical exam, you note a muscular young man with male pattern hair loss. The patient has a loss of sensation bilaterally over the volar surface of the 4th and 5th digits and over the medial aspect of the volar forearm. The patient has 3/5 grip strength of his left hand and 2/5 grip strength of his right hand. There is also notable weakness of finger adduction and abduction. The rest of the patient's physical exam is within normal limits.
Which of the following is the most likely diagnosis?
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A
Cubital tunnel compressionCorrect. Cubital tunnel compression at the elbow produces ulnar nerve symptoms in the hand AND medial forearm sensory loss, since proximal cutaneous branches are involved.
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B
Guyon's canal compressionIncorrect. Guyon's canal compression at the wrist would cause distal ulnar findings but SPARE the medial forearm sensation (which is preserved here only if proximal), inconsistent with the medial forearm sensory loss described.
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C
Carpal tunnel syndromeIncorrect. Carpal tunnel syndrome affects the median nerve, producing thumb, index, middle, and radial half of the ring finger numbness — opposite distribution.
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D
Posterior interosseous nerve compressionIncorrect. Posterior interosseous nerve compression causes weakness of finger and thumb extensors without sensory loss; not this presentation.
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E
Pronator teres syndromeIncorrect. Pronator teres syndrome compresses the median nerve in the proximal forearm, causing thumb/index numbness and weakness of forearm flexors, not the ulnar-distribution sensory loss and finger ab/adduction weakness here.
↑ Tap an answer to reveal the reasoning
Answer: A. Numbness in the medial (ulnar) distribution of the hand — over the 4th and 5th digits and the medial forearm — plus weakness of intrinsic hand muscles (finger adduction/abduction, grip strength loss) is ulnar neuropathy. The key localization question is where along the ulnar nerve the lesion lies. Weakness of intrinsic hand muscles AND sensory loss in the medial forearm (cutaneous branches arising proximal to the wrist) places the lesion at the elbow, not the wrist.
The ulnar nerve passes through the cubital tunnel posterior to the medial epicondyle. Compression at this site (cubital tunnel syndrome) typically results from leaning on the elbow, repetitive flexion (bodybuilding, heavy lifting), or prolonged flexed-elbow posture. Compression at Guyon's canal (wrist) would produce weakness and sensory loss in the hand but would SPARE the medial forearm, because the medial antebrachial cutaneous branches arise above the wrist. Treatment is activity modification, splinting in extension, and surgical decompression if refractory.
**Why each option:**
**A.** Correct. Cubital tunnel compression at the elbow produces ulnar nerve symptoms in the hand AND medial forearm sensory loss, since proximal cutaneous branches are involved.
**B.** Guyon's canal compression at the wrist would cause distal ulnar findings but SPARE the medial forearm sensation (which is preserved here only if proximal), inconsistent with the medial forearm sensory loss described.
**C.** Carpal tunnel syndrome affects the median nerve, producing thumb, index, middle, and radial half of the ring finger numbness — opposite distribution.
**D.** Posterior interosseous nerve compression causes weakness of finger and thumb extensors without sensory loss; not this presentation.