**Question:** Low ulnar nerve palsy is characterised by which of the following symptoms?

A. Claw hand
B. Sensory loss of medial four digits
C. Weakness of grips
D. Inability to extend at M.C.P. joint
E. Inability to abduct the thumb

**Correct Answer:** E. Inability to abduct the thumb

**Core Concept:**
The ulnar nerve is a major peripheral nerve that provides motor and sensory innervation to various muscles and skin regions. In the upper limb, the ulnar nerve is responsible for the innervation of the medial side of the hand, including the muscles that extend the fingers and the thumb. In particular, the ulnar nerve controls the abduction of the thumb, making it essential for proper hand function.

**Why the Correct Answer is Right:**
Low ulnar nerve palsy refers to a condition where the ulnar nerve is compromised and impaired, leading to a loss of function in the muscles it innervates. In the context of this question, the correct answer (E) highlights the specific symptom related to the ulnar nerve palsy: the inability to abduct the thumb. This symptom is a direct consequence of the impaired function of the ulnar nerve, which controls the abduction of the thumb.

**Why Each Wrong Option is Incorrect:**
A. Claw hand (option A) is a general term and not specific to the ulnar nerve palsy. The claw hand might be caused by a variety of conditions affecting the hand and wrist, and is not solely indicative of ulnar nerve palsy.
B. Sensory loss of medial four digits (option B) is not a specific symptom of low ulnar nerve palsy. Sensory loss could be present in various neuropathies affecting the hand, making it an insufficient diagnostic criterion for ulnar nerve palsy.
C. Weakness of grips (option C) is a general symptom and does not specifically indicate ulnar nerve palsy. Gripping weakness could be observed in various conditions affecting the hand and forearm muscles.
D. Inability to extend at the M.C.P. joint (option D) is not a unique symptom for ulnar nerve palsy. Extension weakness could result from a variety of conditions affecting the hand and forearm muscles.

**Clinical Pearl:**
Understanding the role of the ulnar nerve in hand function is crucial for proper diagnosis and management of ulnar nerve palsy. In the context of this question, the correct answer (E) highlights the specific symptom related to ulnar nerve palsy: the inability to abduct the thumb. This symptom is directly linked to the impaired function of the ulnar nerve, which controls the abduction of the thumb. This symptom is a direct consequence of ulnar nerve compromise, making it the correct answer. The other options are not specific to ulnar nerve palsy and could be symptoms of other conditions affecting hand and forearm muscles.