A 50 year old handicraft lady from Pune presented with numbness and weakness of the right hand. On examination, there was atrophy of the thenar eminence and and hypoaesthesia in the area. Compression of which of the following nerve could explain the presentation?
**Core Concept**
The presentation of numbness, weakness, and atrophy of the thenar eminence along with hypoaesthesia in a specific area suggests a focal neuropathy caused by compression of a specific nerve. The thenar eminence is primarily innervated by the median nerve, which also supplies sensation to the palmar surface of the thumb, index, and middle fingers.
**Why the Correct Answer is Right**
The median nerve is responsible for motor innervation of the thenar muscles, including the abductor pollicis brevis, flexor pollicis brevis, and opponens pollicis. Compression of the median nerve leads to weakness and atrophy of these muscles, resulting in the characteristic thenar atrophy. Sensory innervation of the palmar surface of the thumb, index, and middle fingers is also impaired, causing hypoaesthesia in the affected area.
**Why Each Wrong Option is Incorrect**
**Option A:** **Ulnar nerve** compression would primarily affect the intrinsic muscles of the hand, leading to weakness of adduction and abduction of the fingers, and sensory loss in the little finger and ulnar half of the ring finger.
**Option B:** **Radial nerve** compression would affect the extensor muscles of the wrist and fingers, leading to weakness of wrist extension and finger extension, with sensory loss on the back of the hand.
**Option C:** **Axillary nerve** compression would affect the deltoid and teres minor muscles, leading to weakness of shoulder abduction and external rotation, with sensory loss over the lateral aspect of the shoulder.
**Option D:** **Meralgia paresthetica** is caused by compression of the lateral femoral cutaneous nerve, leading to sensory loss on the anterolateral aspect of the thigh.
**Clinical Pearl / High-Yield Fact**
The thenar eminence is a key area to examine in patients with suspected median nerve compression, as atrophy of the thenar muscles is a classic sign of carpal tunnel syndrome.
**Correct Answer: C. Axillary nerve**