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Common palmar digital branch of ulnar nerve

The common palmar digital branch of the ulnar nerve is a terminal sensory branch arising from the superficial branch of the ulnar nerve in the palm. It plays an essential role in providing cutaneous innervation to the medial one and a half fingers (the little finger and the medial half of the ring finger) through its proper digital branches.

This nerve branch lies within the superficial palmar fascia and travels alongside the superficial palmar arch, communicating with the median nerve to form part of the sensory network of the palm. It is clinically important because lesions here can cause sensory loss in the medial digits without affecting motor function.

Synonyms

  • Common digital nerve of the ulnar nerve

  • Common palmar branch of ulnar nerve

  • Superficial ulnar digital branch

Origin, Course, and Branches

Origin:
Arises from the superficial branch of the ulnar nerve within the palm, just distal to the pisiform bone and anterior to the flexor retinaculum.

Course:
Passes distally beneath the palmar aponeurosis and superficial palmar fascia, running medial to the ulnar artery. It moves toward the interdigital cleft between the ring and little fingers.

Branches:

  • Proper palmar digital nerves: Two terminal branches that supply the palmar surfaces of the little finger and the medial half of the ring finger.

  • Communicating branch: Occasionally joins the common palmar digital branch of the median nerve, forming a sensory communicating loop (Berrettini anastomosis).

Relations

  • Superficially: Palmar aponeurosis and superficial palmar fascia

  • Deeply: Superficial palmar arch and flexor tendons

  • Medially: Hypothenar muscles (abductor digiti minimi and flexor digiti minimi brevis)

  • Laterally: Common digital branch of the median nerve (variable communication)

Nerve Supply

Provides cutaneous sensory innervation to:

  • The palmar surface of the little finger

  • The adjacent medial half of the ring finger

  • The distal dorsal surface of these fingers beyond the distal interphalangeal joints (via terminal branches)

Function

  • Sensory function: Conveys tactile, temperature, and pain sensations from the skin of the medial one and a half digits and adjacent palm.

  • Protective sensation: Critical for fine touch and grip control during manipulation and grasping.

  • Clinical marker: Its sensory territory helps localize ulnar nerve lesions to the distal palm when motor function remains intact.

Clinical Significance

  • Ulnar tunnel syndrome (Guyon’s canal): Compression proximal to the origin of this branch can cause numbness in the little and ring fingers while sparing dorsal sensation.

  • Isolated branch injury: Results in sensory loss limited to the palmar surfaces of the medial digits; common in lacerations or surgical trauma near the hypothenar region.

  • Communicating branch variations: May cause overlap with the median nerve, leading to variable sensory findings in palm and fingers.

  • Peripheral neuropathy: Sensory testing of this branch helps differentiate distal ulnar neuropathy from more proximal lesions (e.g., cubital tunnel).

  • Surgical relevance: Important to preserve during palmar incisions or carpal tunnel decompression, as inadvertent injury causes localized numbness and dysesthesia.

MRI Appearance

T1-weighted images:

  • Nerve appears as a linear, intermediate-to-low signal structure surrounded by bright subcutaneous fat.

  • Lies within the superficial palmar soft tissue medial to the flexor tendons.

  • Focal injury or neuroma may appear as fusiform thickening with intermediate signal.

T2-weighted images:

  • Normal nerve: intermediate-to-mildly hyperintense signal relative to muscle.

  • Pathology: bright hyperintense signal in neuropathy, inflammation, or entrapment.

  • Excellent for detecting perineural edema or focal discontinuity from trauma.

STIR:

  • Normal: low-to-intermediate signal.

  • Pathologic: bright hyperintensity in neuritis or compressive injury, often with adjacent soft-tissue edema.

Proton Density Fat-Saturated (PD FS):

  • Normal: uniform low-to-intermediate signal nerve fascicles.

  • Abnormal: focal bright signal and thickening in neuropathy or fibrosis.

  • Clearly delineates nerve from surrounding fat and tendons.

T1 Fat-Sat Post-Contrast:

  • Normal: minimal or no enhancement.

  • Pathology: linear or nodular enhancement seen in neuritis, post-traumatic scarring, or perineural fibrosis.

  • Neuromas show heterogeneous enhancement with surrounding inflammatory reaction.

CT Appearance

Non-Contrast CT:

  • Nerve not directly visualized but identified as a soft-tissue density line in the superficial palmar fat plane medial to the flexor tendons.

  • Indirect findings include soft-tissue swelling or fibrosis in cases of trauma or entrapment.

MRI image

common palmar digital branch of ulnar nerve axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI image

common palmar digital branch of ulnar nerve axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00001

MRI image

common palmar digital branch of ulnar nerve axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00002

MRI image