A 66-year-old woman with history of chronic recurrent painful heel. On physical examination, there was no evidence of sensory loss.
Magnetic resonance imaging of the right foot performed with a high-resolution surface coil. Patient scanned in magnet of 1.5 T. The technical parameters for all magnet strengths were as follows: sagittal, coronal and axial short-tau inversion recovery (STIR) turbo spin echo, coronal turbo spin-echo proton density and T2-weighted and sagittal and coronal turbo spin echo T1-weighted.
MR images show marked thickening of the proximal plantar fascia with increased intrasubstance signal intensity. Also perifascial and mild calcaneal marrow oedema.
In association with these findings, there is selective fat tissue replacement of the abductor digiti minimi muscle.
Baxter's neuropathy is an entrapment syndrome of the inferior calcaneal nerve (ICN), which is the first branch of the lateral plantar nerve. It accounts for 20% of causes of medial heel pain, occasionally irradiating into the lateral aspect of the foot [1, 2, 3].
Atrophy of the abductor digiti minimi muscle reflects chronic compression of the ICN, which consist of loss of muscular mass of the affected muscle with fat tissue replacement (Fig. 1) [4]. MRI plays a key role since nerve entrapment at the foot and ankle involves thin and complex anatomic structures and is underdiagnosed because clinical symptoms and electrophysiologic findings may not contribute to the diagnosis [1]. In addition, opposite to MRI electromyography may not allow differentiation of lateral plantar nerve entrapment at the level of the tarsal tunnel from ICN entrapment [1].
Entrapment of the ICN occurs at three possible places: (a) adjacent to the fascial edge of a hypertrophied abductor halluces muscle, (b) as the nerve passes between the deep fascia of the abductor hallucis muscle and the medial caudal margin of the medial head of the quadratus plantae muscle or (c) most commonly where the nerve passes just anterior to the medial calcaneal tuberosity, where it is sometimes related with calcaneal spur and marked thickening of the proximal plantar fascia, as it is shown in our case (Fig. 2) [1, 4].
Compression of the ICN may result from altered biomechanics, reflected by posterior tibial tendon dysfunction or Achilles tendinosis, or may result from direct mechanical compression of the nerve due to plantar fasciitis and/or plantar calcaneal spurs (Fig. 3) [2]. Recht et al reported plantar fasciitis in 37% of cases with abductor digiti quinti atrophy [4].
Plantar fasciitis is referred in the literature as the most common cause of plantar heel pain [5, 6]. This condition generally occurs in obese middle-aged or elderly patients as a result of repetitive trauma from sport activities, excessive standing and walking [5, 6].
In view of the present case, and in order to identify the proper imaging approach to the patient with heel pain, we recommend to assess findings of fatty infiltration of the abductor digiti minimi muscle, since it reflects chronic ICN entrapment.
Baxter's neuropathy associated with plantar fasciitis
1. On MRI, there is a visible soft tissue structure on the medial side of the heel, particularly along the medial margin of the plantar fascia, indicating a potential site of compression consistent with the course of Baxter’s nerve (i.e., the first branch of the lateral plantar nerve, also known as the inferior calcaneal nerve).
2. In the affected area, thickening of the plantar fascia and/or calcaneal spur (osteophyte) formation can be seen, likely related to chronic traction by the plantar fascia or plantar aponeurosis.
3. Within the abductor digiti minimi muscle, signs of fatty infiltration or muscle atrophy are present, suggesting prolonged denervation consistent with Baxter’s nerve compression.
4. No significant abnormal signal changes are observed in other structures around the heel; bone continuity is intact, with no obvious fracture or severe bony destruction.
Based on the imaging findings (especially the localized fatty infiltration of the abductor digiti minimi muscle), the patient’s history of chronic and recurrent heel pain, and clinical examinations (no significant sensory deficits, but persistent medial heel pain and discomfort in adjacent areas), the most likely diagnosis is:
“Baxter’s Neuropathy (Compression Neuropathy of the First Branch of the Lateral Plantar Nerve).”
If any doubt remains, additional tests such as EMG, ultrasound, or the patient’s response to targeted treatments can be used to confirm the diagnosis.
1. Conservative Treatment:
2. Surgical Indications:
3. Rehabilitation and Exercise Prescription (FITT-VP Principle):
4. Special Precautions:
Disclaimer: The above report is a reference analysis based on current imaging and medical history. It does not replace an in-person consultation or professional medical opinion. A definitive diagnosis and treatment plan should be made by a specialist physician after comprehensive evaluation of the patient’s actual condition.
Baxter's neuropathy associated with plantar fasciitis
