Topics

Topic

design image
Medial cutaneous nerve of forearm

The medial cutaneous nerve of the forearm, also known as the medial antebrachial cutaneous nerve, is a purely sensory nerve originating from the medial cord of the brachial plexus (C8–T1). It supplies the skin of the medial aspect of the forearm, extending from the elbow to the wrist.

This small but clinically important nerve provides sensory innervation to the anteromedial and posteromedial surfaces of the forearm. Its superficial course around the medial epicondyle of the humerus makes it vulnerable to injury or entrapment during elbow trauma, venipuncture, or cubital tunnel procedures.

Synonyms

  • Medial antebrachial cutaneous nerve

  • Internal cutaneous nerve of forearm

  • N. cutaneus antebrachii medialis

Origin, Course, and Branches

  • Origin: Arises from the medial cord of the brachial plexus, carrying fibers from spinal nerves C8 and T1.

  • Course:

    • Descends medial to the axillary and brachial arteries within the axilla and upper arm.

    • Pierces the deep fascia approximately midway down the arm, often near the basilic vein.

    • Enters the forearm by passing anterior to the medial epicondyle of the humerus, where it divides into two main branches.

  • Branches:

    • Anterior (volar) branch: Runs along the anteromedial surface of the forearm, supplying skin from the elbow to the wrist.

    • Posterior (ulnar) branch: Passes obliquely posterior to the medial epicondyle, supplying the posteromedial forearm skin to near the wrist.

    • Communicating branches: Often join with the ulnar nerve or medial brachial cutaneous nerve.

Relations

  • Superiorly: Lies medial to the brachial artery and median nerve in the upper arm.

  • At the elbow: Courses anterior to the medial epicondyle, near the basilic vein — a common site of iatrogenic injury.

  • In the forearm: Travels superficial to the flexor muscles (especially flexor carpi ulnaris) and beneath the superficial fascia.

  • Laterally: Related to the ulnar nerve and medial antebrachial fascia.

Nerve Supply

  • Sensory only: Supplies the skin over the anteromedial and posteromedial forearm down to the wrist.

  • Does not innervate muscles or joints directly.

Function

  • Cutaneous sensation: Provides sensory innervation to the medial forearm on both anterior and posterior aspects.

  • Protective feedback: Contributes to pain, temperature, and tactile sensation along the ulnar side of the forearm.

  • Clinical landmark: Used in evaluating sensory deficits related to brachial plexus, cubital, or ulnar nerve lesions.

Clinical Significance

  • Entrapment or injury: May occur at the medial epicondyle or during venipuncture (basilic vein cannulation).

  • Iatrogenic causes: Nerve may be injured during elbow surgeries, cubital tunnel decompression, or catheter placement.

  • Symptoms: Numbness, tingling, or burning sensation along medial forearm; hypersensitivity or neuropathic pain may occur.

  • Brachial plexus lesions: Involvement of the medial cord affects this nerve along with ulnar and medial brachial cutaneous nerves.

  • Clinical testing: Assessed by light touch and pinprick over medial forearm region.

  • Imaging role: MRI and ultrasound can assess continuity, entrapment, or neuroma formation.

MRI Appearance

  • T1-weighted images:

    • Nerve: Low-to-intermediate signal linear structure surrounded by high-signal fat.

    • Course: Visualized superficial to flexor carpi ulnaris near the medial forearm.

    • Pathology: Neuroma or fibrosis may appear as focal enlargement or altered signal intensity (intermediate-to-bright).

  • T2-weighted images:

    • Normal nerve: Intermediate signal.

    • Pathology: Nerve injury or inflammation appears as bright hyperintense swelling along its course.

    • Adjacent edema: Surrounding fat may show increased T2 signal in neuritis or entrapment.

  • STIR:

    • Normal nerve: Intermediate-to-dark signal.

    • Abnormal nerve: Bright hyperintensity in neuropathy, neuritis, or trauma.

    • Helps distinguish between chronic fibrosis (dark) and active inflammation (bright).

  • Proton Density Fat-Saturated (PD FS):

    • Normal nerve: Intermediate-to-dark continuous cord-like signal.

    • Pathologic nerve: Focal or diffuse bright signal indicating edema, entrapment, or nerve inflammation.

    • Useful in identifying subtle neuropathy or scarring post-surgery.

  • T1 Fat-Sat Post-Contrast:

    • Normal nerve: Mild, uniform enhancement or none.

    • Inflamed or injured nerve: Focal or linear enhancement along the course.

    • Neuroma or entrapment: Irregular nodular enhancement with perineural enhancement.

CT Appearance

Non-Contrast CT:

  • Nerve is not well visualized directly, seen as a thin soft-tissue density in medial subcutaneous plane.

  • Indirect findings: Soft-tissue swelling, edema, or scarring along medial forearm.

  • Useful for: Detecting foreign bodies, post-traumatic fibrosis, or osseous changes compressing the nerve.

Post-Contrast CT (standard):

  • Nerve itself enhances minimally.

  • Inflamed perineural tissue or neuroma may show enhancement.

  • Best for evaluating iatrogenic injury, entrapment near surgical sites, or soft-tissue scarring.

MRI images

Medial cutaneous nerve of forearm axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI images

Medial cutaneous nerve of forearm axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00001

MRI images

Medial cutaneous nerve of forearm axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00002

MRI images

Medial cutaneous nerve of forearm axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00003