Related Subjects:
|Radial Nerve
|Median Nerve
|Ulnar Nerve
|Musculocutaneous nerve
|Axillary nerve
|Brachial plexus
|Dermatomes
Although the fourth and fifth digits are held in the clawed position when the nerve is injured at the wrist, a high lesion paralyses the long flexors to these two fingers and results in the loss of this sign.
Overview of the Ulnar Nerve
The ulnar nerve is one of the major nerves of the upper limb. It originates from the brachial plexus and supplies motor and sensory innervation to parts of the forearm and hand.
Anatomy of the Ulnar Nerve
- Origin:
- The ulnar nerve arises from the medial cord of the brachial plexus, with nerve roots from C8 and T1.
- Course:
- Travels down the medial aspect of the arm, passing posterior to the medial epicondyle of the humerus (commonly known as the "funny bone").
- Enters the forearm and travels between the flexor carpi ulnaris and flexor digitorum profundus muscles.
- Continues into the hand, passing through Guyon's canal to reach the palmar aspect of the hand.
Branches of the Ulnar Nerve
- Muscular Branches:
- Innervate the flexor carpi ulnaris and the medial half of the flexor digitorum profundus in the forearm.
- In the hand, innervate most of the intrinsic muscles, including the hypothenar muscles, the medial two lumbricals, the interossei, and the adductor pollicis.
- Sensory Branches:
- Dorsal Cutaneous Branch: Provides sensation to the dorsal aspect of the medial one and a half fingers and the associated hand area.
- Palmar Cutaneous Branch: Provides sensation to the palmar aspect of the medial one and a half fingers and the associated hand area.
Functions of the Ulnar Nerve
- Motor Functions:
- Controls the movement of the flexor carpi ulnaris and the medial half of the flexor digitorum profundus in the forearm.
- Controls most of the intrinsic muscles of the hand, which are crucial for fine motor skills and finger movements.
- Sensory Functions:
- Provides sensation to the skin of the medial one and a half fingers on both the dorsal and palmar aspects of the hand.
Clinical Relevance
- Ulnar Nerve Entrapment:
- Compression or irritation of the ulnar nerve, often occurring at the elbow (cubital tunnel syndrome) or at the wrist (Guyon's canal syndrome).
- Symptoms: Numbness, tingling, and pain in the medial one and a half fingers, weakness in the intrinsic hand muscles.
- Treatment: Includes physical therapy, splinting, anti-inflammatory medications, and in severe cases, surgical decompression.
- Ulnar Nerve Injury:
- Injuries can occur due to trauma, fractures, or prolonged pressure on the nerve.
- Symptoms: Similar to entrapment, with possible muscle atrophy and loss of fine motor skills in the hand.
- Treatment: Depends on the severity; may include physical therapy, medications, or surgical repair.
- Claw Hand Deformity:
- Occurs due to severe ulnar nerve damage, leading to unopposed action of the extensor muscles of the fingers.
- Symptoms: Hyperextension of the metacarpophalangeal joints and flexion of the interphalangeal joints in the ring and little fingers.
- Treatment: Often involves surgical intervention to correct the deformity and restore function.
Summary
The ulnar nerve is a vital nerve of the upper limb, providing motor and sensory innervation to the forearm and hand. It arises from the brachial plexus and travels down the arm, forearm, and into the hand. Understanding its anatomy and clinical relevance is crucial for diagnosing and managing conditions such as ulnar nerve entrapment, injuries, and claw hand deformity.