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QuestionChoice
The radial nerve supplies the BEST muscles: brachioradialis, extensors of the forearm, supinator and triceps. It also supplies sensation to the dorsal arm and forearm, and the dorsal aspect of the radial 3 1/2 fingers. Finger abduction/adduction will not be affected since the interossei are innervated by the ulnar nerve. The radial nerve can be damaged at multiple points, including the wrist (eg. tight handcuffs), which causes finger drop (loss of finger extension), proximal forearm or in the spiral groove (eg. a fracture of the humerus or prolonged tourniquet), which presents with wrist drop, or at the level of the brachial plexus (crutches or a honeymoon/Saturday night palsy), which causes loss of triceps as well wrist drop.
52894
c
Radial nerve palsy
QuestionChoice
The axillary nerve supplies the deltoid and teres minor muscles. This manifests with inability to abduct the arm. It also supplies sensation to the regimental badge area. Finger abduction is conducted by the interossei muscles, which are innervated by the ulnar nerve. The axillary nerve does not supply any intrinsic hand muscles.
52895
d
Axillary nerve palsy
QuestionChoice
The musculocutaneous nerve supplies the coracobrachialis (which flexes and adducts the shoulder), biceps brachii (which flexes and supinates the forearm) and brachialis muscles (flexes the forearm). Injury to this nerve manifests with inability to flex and adduct the shoulder and flex the elbow. Finger abduction is conducted by the interossei muscles, which are innervated by the ulnar nerve. The musculocutaneous nerve does not supply any intrinsic hand muscles.
52896
e
Musculocutaneous nerve
QuestionChoice
In the hand, the ulnar nerve provides motor innervation to the interossei muscles, which are responsible for finger abduction and adduction. It also supplies the third and fourth lumbricals, the adductor pollicis and sensation over the hypothenar eminence and ulnar 1 and 1/2 fingers. The ulnar nerve runs medially around the elbow, through the cubital tunnel and along the medial aspect of the forearm. The most likely area of impingement is around the elbow, where there is notable swelling on examination. Damage can either occur due to bony impingement in the context of a fracture or oedema compressing the ulnar nerve through its course in the cubital tunnel.
52892
a
Ulnar nerve
QuestionChoice
In the hand, the median nerve supplies the muscles of the thenar eminence (opponens pollicis, abductor pollicis brevis and flexor pollicis brevis), as well as the radial 2 lumbricals. Its motor supply can be remembered using the helpful mnemonic LOAF. It also supplies sensation to the thenar eminence and the radial 3 1/2 fingers on their palmar aspect. Finger abduction/adduction will not be affected since the interossei are innervated by the ulnar nerve. The most common site of compression of the median nerve is at the carpal tunnel.
52893
b
Median nerve palsy
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Finger abduction- ulnar
Pincer grip strength between thumb and index finger- median
Wrist extension strength against resistance- radial
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# Summary

The ulnar nerve, deriving from nerve roots C8-T1, is integral to motor and sensory functions in the arm. Motor functions include innervating most of the intrinsic hand muscles and two muscles in the forearm, while sensory functions encompass innervation to the skin of the medial 1.5 digits and associated palm area. Noteworthy anatomical landmarks include its passage in the cubital tunnel at the elbow and Guyon's canal in the wrist, and its bifurcation into deep and superficial branches.

# Definition

The ulnar nerve is a peripheral nerve that arises from the medial cord of the brachial plexus, with its roots in the C8-T1 nerve roots. It serves both motor and sensory functions in the forearm and hand.

# Epidemiology

Ulnar nerve injuries, often a result of elbow trauma or continuous pressure on the elbow, are relatively frequent. Individuals at high risk include those participating in physical activities, sports, or with specific medical conditions predisposing them to nerve compression or trauma.

# Aetiology

The ulnar nerve can be injured through various mechanisms, including:

-   Direct trauma or injury to the nerve
-   Compression or entrapment (e.g., in conditions such as cubital tunnel syndrome or Guyon's canal syndrome)
-   Iatrogenic causes during surgical procedures
-   Systemic diseases that affect the peripheral nerves (e.g., diabetes mellitus)

#  Anatomical Course

  

The ulnar nerve comes off the medial cord of the brachial plexus, and passes through the axilla with the axillary artery on its lateral side and the axillary vein on its medial side. In the arm, the ulnar nerve travels alongside the brachial artery until half-way down, where it passes through the medial septal fascia to enter the posterior compartment of the arm. The ulnar nerve then passes posterior to the elbow through a small space between the medial epicondyle and olecranon called the ulnar tunnel.

  

In the forearm, the ulnar nerve pierces between the two heads of flexor carpi ulnaris, and travels deep to the muscle alongside the ulna. Three branches come off the ulnar nerve in the forearm:

  

- Muscular branch = innervates muscles of the anterior compartment

  

- Palmar cutaneous branch = innervates the medial half of the palm

- Dorsal cutaneous branch = innervates the dorsal surface of the medial 1 1/2 digits and associated dorsal hand area

  

The ulnar nerve passes through the wrist superficial to the flexor retinaculum and medial to the ulnar artery, and enters the hand through the ulnar (or Guyon's) canal. It terminates into two branches:

  

- Superficial = innervates the palmar surface of the medial 1 1/2 digits

- Deep = intrinsic muscles of the hand (hypothenar muscles, medial two lumbricals, adductor pollicis, palmar and dorsal interossei, palmaris brevis)

  

**"LOAF"**.

  

*All the muscles in the hand are supplied by the ulnar nerve except LOAF which are supplied by the median nerve*

  

L - lateral two lumbricals

  

O - opponens pollicis

  

A - abductor pollicis brevis

  

F - flexor pollicis brevis

  

The majority of the intrinsic muscles of the hand are supplied by the deep branch of the ulnar nerve, except palmaris brevis which is supplied by the superficial branch of the ulnar nerve.

**Summary table**

  

| Nerve roots | C8-T1 |
| --------------------- | ------------------------------------------------------------ |
| **Motor functions** | Innervates flexor carpi ulnaris and the medial half of flexor digitorum profundus. Innervates the intrinsic muscles of the hand (except for the LOAF muscles*) |
| **Sensory functions** | Innervates the medial 1 1/2 digits and the associated palm area |

# Signs and Symptoms

Signs and symptoms of ulnar nerve injury may include:

-   Weakness or paralysis of the muscles innervated by the ulnar nerve (e.g., most of the intrinsic hand muscles and two muscles in the forearm)
-   Numbness, tingling, or pain in the sensory distribution of the ulnar nerve (skin of the medial 1.5 digits and associated palm area)

# Differential Diagnosis

Other conditions that could present with similar symptoms include:

-   Brachial Plexopathy: Similar motor and sensory loss, but usually involves other nerves of the brachial plexus.
-   Carpal Tunnel Syndrome: Primarily causes sensory changes in the palmar aspect of the hand and motor weakness in the median nerve distribution.
-   Radial Neuropathy: Presents with sensory and motor deficits in the radial nerve distribution, including the dorsal surface of the lateral 3 1/2 digits.
-   Cervical Radiculopathy: Symptoms may overlap with ulnar nerve injury, but there may also be neck pain, and symptoms may be exacerbated by neck movements.

# Investigations

Investigations for a suspected ulnar nerve injury may include:

-   Neurological examination: to assess sensory and motor deficits
-   Electromyography (EMG) and Nerve Conduction Studies (NCS): to evaluate nerve function
-   MRI or CT scan: to identify any anatomical causes of nerve injury such as a fracture or mass lesion

# Management

The management of ulnar nerve injuries depends on the underlying cause:

-   Conservative measures: including rest, physical therapy, and use of splints to prevent muscle contractures in cases of mild nerve injury
-   Pharmacological interventions: such as analgesics for pain management
-   Surgical interventions: in cases of severe nerve injury or where the cause is a correctable lesion such as a tumor or fracture
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Ulnar nerve injuries
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Orthopaedics
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The ulnar nerve innervates the interossei muscles, crucial for finger abduction and adduction, and can be injured by supracondylar fractures.
A 43-year-old right-handed man presents to A&E after an accident at work. He was carrying a large glass window when he tripped and fell onto his left side. You note extensive bruising and swelling around his left elbow. An X-ray demonstrates a supracondylar fracture of the elbow. You assess his range of movement and find he is unable to abduct his fingers.

Which nerve has been damaged?
a