Baxter's nerve compression imaging performance

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One of the causes of heel pain.
Heel pain is a common clinical symptom.
The differential diagnosis includes plantar fasciitis, fat pad atrophy, calcaneal stress fracture or osteoporosis, inflammatory arthritis, tumor And infection.

One of the more elusive diagnostic factors in heel pain is the compression of the first branch of the lateral plantar nerve (Baxter's nerve impingement).

Baxter's nerve is a mixed nerve of sensory and motor, which provides motor transmission for Abductor digiti minimi (AbDM).

Baxter's nerve entrapment can produce clinical symptoms that are indistinguishable from plantar fasciitis.
Although it is seen in 20% of patients with heel pain, other causes of heel pain are often overlooked.

The abductor digitorum (AbDM) may have lesions, but it is difficult to detect clinically.

MR can be used to detect muscle changes related to innervation in the abductor digitorum (AbDM), thereby confirming the diagnosis of Baxter's nerve entrapment.

Anatomy of the two terminal branches of the tibial nerve: one is the medial plantar nerve and the other is the lateral plantar nerve.
The skin branches of the medial plantar nerve are distributed in the skin of the inner plantar, and the skin of the lateral plantar nerve innervates the outer plantar Skin, this nerve is the sensory branch of the little toe and the outside of the fourth toe, which innervates the movement of the abductor digitorum and quadratus plantarius.

Baxter's nerve (Baxter nerve) is the first branch of the lateral plantar nerve, also known as the inferior calcaneus nerve, which innervates the abductor digitorum muscle (AbDM).

Lateral plantar nerve: Lateral plantar nerve (LPN) Medial plantar nerve (MPN): Abductor digiti minimi (AbDM) Pathological Baxter nerve compression is common in two locations (see the figure below).

Baxter nerve entraps two potential locations (in the oval circle): 1.
When the nerve passes between the deep fascia of the abductor muscle (AH) and the medial plantar edge of the quadratus plantar muscle (QP).

2.
When the more distal nerve passes along the anterior part of the medial tuberosity of the calcaneus, the attachment point of the plantar calcaneus and plantar fasciitis may cause compression.

According to reports in the literature, risk factors for Baxter nerve involvement include advanced age, calcaneal bone hyperplasia, plantar fasciitis, plantar masses, thickened blood vessels, muscle enlargement (such as athletes), obesity, and foot varus.

Imaging manifestations MRI has proved to be very valuable to show denervated muscle-related changes; compared with ultrasound or CT, MRI is more sensitive to changes in the tissues in the muscle; and has advantages compared with electromyography because The non-invasiveness and superior anatomical details of MRI can show the pathological changes of muscles with dual innervation and can rule out other diagnoses (fractures, tumors, fasciitis).

The normal abductor digitorum muscle shows isointensity on T1WI and fluid sensitivity sequence (red arrow in the figure below).

Acute and subacute muscle denervation are best assessed by fluid-sensitive sequences, such as T2WI images with fat suppression (T2 FS) or short tau reversal recovery (STIR) images.
Compared with normal muscles, the muscle abdominal The increased signal is related to neurogenic muscle edema.
The enhanced scan occurs in the acute to subacute stage of denervation; in the case of Baxter nerve compression, according to the patient’s innervation anatomy, muscle edema will be selectively in the abductor digitorum (AbDM) occurs internally, and may also occur in the flexor digitorum brevis and quadratus plantar muscles; obvious muscle atrophy and fatification can be seen in the chronic phase.


T1 image muscle showed isosignal (asterisk) and no atrophy; suppressed T2 image showed muscle edema of the abductor digitorum (arrow) and flexor digitorum brevis (arrow).

The coronal T1WI and suppressed PDWI images of patients with severe atrophy and fat infiltration of the abductor digita minor can selectively involve the abductor digitorum muscle due to chronic Baxter nerve involvement; the signal intensity (arrow) of the abductor digita minor muscle is similar to the phase There is no obvious muscle edema in adjacent subcutaneous fat.

The transverse T1WI and coronary fat suppression PDWI images of another patient with chronic Baxter nerve compression showed severe diffuse atrophy and fatty infiltration of the abductor digitorum (arrow).


The initial treatment of Baxter nerve compression is usually conservative treatment, including a combination of rest, non-steroidal anti-inflammatory drugs, corticosteroid injections, and orthotics.

If persistent pain persists after conservative treatment, surgery can be performed.

Conclusion Baxter nerve compression is a clinically difficult diagnosis and is often overlooked in the manifestations of heel pain.

MRI can evaluate the denervation effect of nerve compression by identifying abnormalities in the abdomen of the abductor digitorum (AbDM) muscle.

In addition, potential causes of impact (eg, calcaneal spurs, soft tissue masses, vasodilatation) and related pathologies (eg, plantar fasciitis, tendinopathy) can be found, and other differential diagnoses (eg, stress fractures) can be ruled out.