A 53-year-old man is evaluated for right hand discomfort. A month ago, he started to intermittently experience a "pins and needles" sensation in his right hand that is worse at night. He has no neck pain or history of trauma to the right upper extremity. The patient has smoked a pack of cigarettes daily for 20 years and has worked as an accountant for the past 30 years. On physical examination, there is loss of sensation over the right fifth digit. There is no swelling, redness, or warmth of the hand. The patient is most likely to have weakness of which of the following movements?

Question

A 53-year-old man is evaluated for right hand discomfort.  A month ago, he started to intermittently experience a "pins and needles" sensation in his right hand that is worse at night.  He has no neck pain or history of trauma to the right upper extremity.  The patient has smoked a pack of cigarettes daily for 20 years and has worked as an accountant for the past 30 years.  On physical examination, there is loss of sensation over the right fifth digit.  There is no swelling, redness, or warmth of the hand.  The patient is most likely to have weakness of which of the following movements?

Quizplus · Accepted Answer

11ec160b_35cd_7040_9249_43ccb1cae5c4_MD0001_00 The ulnar nerve originates from the medial cord of the brachial plexus, courses with the brachial artery in the upper arm, and enters the forearm after passing posterior to the medial epicondyle of the humerus (cubital tunnel). It innervates flexor carpi ulnaris (wrist flexion and adduction) and the medial portion of flexor digitorum profundus before entering the wrist through Guyon canal (between the hook of the hamate and pisiform). In the hand, the superficial branch of the ulnar nerve provides cutaneous innervation to the fifth digit, medial half of the fourth digit, and the hypothenar eminence. The deep motor branch supplies most of the intrinsic muscles of the hand. The ulnar nerve is most commonly injured at the elbow due to trauma (eg, medial epicondyle fracture) or compression (eg, resting on a hard surface while using a computer). Ulnar neuropathy at the elbow usually presents with discomfort and loss of sensation/paresthesia in the ulnar distribution. Severe cases can also result in impaired wrist flexion and adduction (ie, ulnar deviation) along with finger weakness/clumsiness. The nerve can also be injured more distally at the wrist as it runs through Guyon canal, resulting in more pronounced clawing of the 4th and 5th digits (ulnar claw) due to sparing of the flexor digitorum profundus. (Choices A and E) Radial nerve injury (eg, C6/C7 disc herniation, humerus fracture) can result in weakness in elbow and/or wrist extension in addition to sensory loss over the posterior arm, dorsolateral hand, and dorsal thumb. (Choice B) Axillary nerve injury (eg, shoulder dislocation, humeral fracture) can present with loss of sensation over the lateral upper arm and weakness in shoulder abduction (eg, deltoid weakness). (Choice C) Proximal median nerve injury (eg, trauma) can result in weakness on wrist flexion and abduction (ie, radial deviation), flexion of the second/third digits, and flexion/opposition of the thumb along with palmar sensory loss involving the majority of the first through third digits. Educational objective: Ulnar nerve injury most commonly occurs at the elbow (eg, compression due to resting arm on a hard surface while using a computer) and usually presents with discomfort and sensory loss/paresthesia in the fifth digit, medial half of the fourth digit, and the hypothenar eminence. In severe cases, patients can also have weakness on wrist flexion and adduction (ie, ulnar deviation) along with finger weakness/clumsiness. __________ References: Entrapment neuropathies I: upper limb (carpal tunnel excluded). (http://www.ncbi.nlm.nih.gov/pubmed/21072726) Peripheral nerve entrapment and injury in the upper extremity. (http://www.ncbi.nlm.nih.gov/pubmed/20082510)

A 53-Year-Old Man Is Evaluated for Right Hand Discomfort