Medial Calcaneal Nerve: Anatomy, Relations, Function, Clinical Significance, MRI & CT Imaging

Topic

Medial calcaneal nerve

The medial calcaneal nerve is a sensory branch of the tibial nerve that arises within the tarsal tunnel, near or proximal to the level of the flexor retinaculum. It provides cutaneous innervation to the medial and plantar aspect of the heel, playing an essential role in heel sensation and pain syndromes such as tarsal tunnel syndrome and calcaneal neuropathy.

This small but clinically significant nerve passes through or superficial to the flexor retinaculum, piercing the laciniate ligament before distributing branches to the heel skin. Anatomical variation in its origin and number of branches is common—it may arise as one or multiple branches, sometimes directly from the tibial nerve or less frequently from the lateral plantar nerve.

Synonyms

Internal calcaneal nerve
Calcaneal branch of the tibial nerve
Medial heel nerve

Origin and Course

Origin: Arises from the tibial nerve in the tarsal tunnel, typically between the origins of the lateral plantar and medial plantar nerves.
Course:
- Descends posterior and medial to the calcaneus.
- Passes beneath or pierces the flexor retinaculum (laciniate ligament).
- Traverses the medial aspect of the heel, running superficially beneath the abductor hallucis muscle.
- Terminates by dividing into small cutaneous branches supplying the heel pad and medial plantar surface of the hindfoot.

Relations

Superiorly: Tibial nerve and flexor retinaculum
Inferiorly: Heel fat pad and plantar aponeurosis
Medially: Medial malleolus and abductor hallucis
Laterally: Lateral plantar nerve and vessels
Posteriorly: Calcaneal tuberosity

Function

Sensory innervation: Provides sensation to the medial aspect of the heel and the adjacent plantar surface.
Protective role: Transmits tactile and pressure sensations important for standing and gait.
Clinical marker: Involvement in neuropathies results in heel pain, numbness, or paresthesia, especially during weight-bearing.

Clinical Significance

Entrapment neuropathy: May occur within the tarsal tunnel or under the flexor retinaculum, causing chronic heel pain.
Tarsal tunnel syndrome: Involvement of the medial calcaneal branch produces isolated or combined sensory loss along the heel.
Trauma or surgery: Injuries during posterior ankle surgery, Achilles repair, or calcaneal fractures can damage the nerve.
Heel pain syndromes: Distinguishing neuralgia from plantar fasciitis is crucial; medial calcaneal nerve irritation often mimics plantar fasciitis.
Imaging role: MRI and high-resolution CT help evaluate nerve entrapment, inflammation, and post-surgical changes.

MRI Appearance

T1-weighted images:
- Normal nerve: low-to-intermediate signal intensity (dark linear structure).
- Surrounded by bright fat signal within the tarsal tunnel and heel fat pad.
- Entrapment or neuritis: mild thickening with intermediate-to-high signal.
T2-weighted images:
- Normal nerve: intermediate-to-low signal, slightly darker than muscle.
- Pathology: bright hyperintense signal in cases of neuritis, entrapment, or trauma.
- Fat suppression highlights nerve inflammation and perineural edema.
STIR:
- Normal: dark linear nerve structure.
- Pathology: hyperintense nerve and surrounding fat, indicating neuritis or edema.
- Best sequence for identifying early inflammatory changes or post-traumatic swelling.
Proton Density Fat-Saturated (PD FS):
- Normal: thin, dark linear nerve bundle within bright fat background.
- Pathology: focal or diffuse bright signal representing nerve irritation, fibrosis, or traction injury.
- Detects subtle perineural signal abnormalities in tarsal tunnel entrapment.
T1 Fat-Sat Post-Contrast:
- Normal nerve: minimal enhancement.
- Abnormal: patchy, nodular, or diffuse enhancement in neuritis, fibrosis, or post-surgical scar tissue.
- Enhancing surrounding soft tissue may suggest perineural inflammation or postoperative changes.

CT Appearance

Non-Contrast CT:

The nerve is not directly visualized due to small caliber.
Indirect signs: soft-tissue thickening, fascial plane loss, or calcaneal deformity impinging the tarsal tunnel.
Chronic entrapment: fat stranding or fibrotic tissue around medial ankle.

Post-Contrast CT (standard):

The nerve itself shows no enhancement.
Adjacent inflamed or fibrotic tissues may show enhancement along the course of the tibial nerve or its branches.
Useful for assessing osseous impingement or postoperative scarring compressing the nerve.

MRI image

Topics