Lateral forearm skin nerve !
The lateral antebrachial cutaneous nerve is the end of the musculocutaneous nerve; it gives feeling to the outer, thumb side of the forearm.
Official name: Lateral antebrachial cutaneous nerve
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What it is
The skin branch of the musculocutaneous nerve, coming out beside the distal biceps tendon.
What it does
Feeling on the outer forearm; it can be stretched during distal biceps repair.
Key facts
- Roots
- C5–C6, end of the musculocutaneous nerve
- Moves
- None
- Feeling from
- Lateral forearm
Relations
- Course
- Comes out from under the lateral edge of biceps above the elbow, pierces the deep fascia lateral to the biceps tendon, passes behind the cephalic vein and divides into anterior and posterior branches that run down the lateral forearm to the base of the thenar eminence
- Medial
- The distal biceps tendon
- Deep
- Brachialis, then brachioradialis
- Superficial
- The cephalic vein, which crosses in front of it at the elbow
How to find it
With the elbow bent against resistance the distal biceps tendon stands out; the nerve emerges just lateral to it, at or slightly above the elbow crease, where tapping may send tingling down the lateral forearm.
Examination
- Pinprick along the lateral forearm: loss with normal biceps strength points to this branch; loss with weak biceps points to the musculocutaneous nerve
- Tinel's sign just lateral to the biceps tendon, with pain on elbow extension plus pronation, suggests compression under the edge of the tendon
On imaging
Not seen on radiographs. Ultrasound finds it where it comes out lateral to the biceps tendon at the elbow, close to the cephalic vein, which is the landmark. It is looked for when a painful neuroma is suspected after venepuncture or distal biceps repair; the parent musculocutaneous nerve can be traced upward between biceps and brachialis.
Clinical notes
- Retraction during distal biceps tendon repair commonly stretches it; most cases recover
- Compression by the biceps tendon edge with repeated elbow extension and pronation (racquet sports, throwing) gives burning in the lateral forearm
- Its territory overlaps the superficial radial nerve's, so neuromas of either can contribute to pain after radial wrist surgery
- A common donor for short nerve grafts, for example for digital nerves
Anatomical variants
- If the musculocutaneous nerve is absent, this skin territory is supplied by a branch of the median nerve
Development
It carries C5–C6 fibres from the preaxial border of the limb bud, which becomes the lateral (radial) side after the limb's outward rotation; its strip of lateral forearm skin is the usual place to test the C6 dermatome.
Related conditions
Test yourself
Think of the answer, then tap the question to see it.
Of which nerve is the lateral forearm skin nerve the terminal branch, and where does it appear?
The musculocutaneous nerve; it appears lateral to the distal biceps tendon, between biceps and brachialis, just above the elbow crease.
Which operation most often affects the lateral forearm skin nerve?
Distal biceps tendon repair through an anterior incision, from retraction; most cases recover.
How does lateral forearm numbness with normal biceps strength localise the lesion?
To the lateral forearm skin nerve; with weak biceps it points to the musculocutaneous nerve.
Educational information, not medical advice. For any symptom, see a health professional.
Its names
- Official Latin (TA2)
- nervus cutaneus lateralis antebrachii TA2 6423
- Official Spanish (DeCS)
- Nervio cutáneo lateral del antebrazo
- English (TA2)
- Lateral antebrachial cutaneous nerve
- Also called
- lateral cutaneous nerve of forearm
Related
Sources: Terminologia Anatomica (TA2); Anatomy, Shoulder and Upper Limb, Musculocutaneous Nerve; Anatomy, Shoulder and Upper Limb, Forearm Nerves; Anatomy of the Human Body (20th ed.): The Branchial Region (Lea & Febiger (Gray's Anatomy, 1918), 1918) · adapted, Public domain; 8.5 Development of the Appendicular Skeleton (OpenStax (Rice University), 2022) · adapted, CC BY 4.0.
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Representative model, for educational purposes only.
