Today I have an experience to do Ultrasound to detect Morton's Neuroma..it appears hypoechoeic lump on ultrasound over the interdigital area. When you put the colour doppler on it, usually theres no signal. This might differentiate it from synovitis in which is more vascular. The patient has Sjogren's disease and presented with arthritis before and pain in between 2nd and 2rd interdigital space of both feet. This was associated with feeling tingling sensation and worse on walking.
What is Morton's Neuroma?
From Uptodate
INTERDIGITAL PLANTAR (MORTON'S) NEUROMA — Entrapment neuropathy, with or without an associated plantar neuroma, often develops between the third and fourth toes on the plantar surface of the foot. Anastomoses of the medial and lateral plantar nerves occur in this area. A neuropathy in this location is commonly called a Morton's neuroma. Similar involvement of other interdigital plantar nerves may also occur.
Etiology — Possible causes of neuropathy in this area include excessive mobility of the fourth metatarsal, nerve impingement between flattened metatarsal heads, or compression of the nerve as it is angulated over the transverse tarsal ligament. Chronic compression leads to neuroma formation. Similar signs and symptoms may be induced by an intermetatarsal bursitis rather than a neuroma since the neurovascular bundle lies close to the bursa.
Clinical manifestations — Symptoms of a Morton's neuroma include hyperesthesia of the toes, numbness and tingling, and aching and burning in the distal forefoot. Pain radiates forward from the metatarsal heads to the third and fourth toes. It is aggravated by walking on hard surfaces and wearing tight or high-heeled shoes. The pain frequently persists for some time after cessation of weight bearing. Symptoms are unilateral in 85 percent of cases.
Physical examination reveals tenderness in the plantar aspect of the distal foot over the third and fourth metatarsals; compressing the forefoot reproduces the symptoms. The tenderness is occasionally aggravated by direct pressure to the plantar aspect of the third and fourth metatarsophalangeal joints; pressure may be applied by squeezing the metatarsal heads together with one hand, and simultaneously compressing the involved web space with the thumb and index finger of the opposite hand. There should be a concomitant sensation of burning distally.
Diagnosis — The diagnosis of a Morton's neuroma is often clinical. Radiography may reveal lateral toe deviation, a faintly radiopaque shadow, and rarely, notching of the adjacent bone. Other procedures used include ultrasonography, computed tomography, MRI, and nerve conduction testing.
Of these modalities, MRI is the most effective to diagnose a Morton's neuroma. In one report, for example, MRI findings in 17 feet with suggestive symptoms of neuroma were corroborated by surgical findings. In another study, a change in clinical diagnosis as well as in treatment plans occurred after MRI in 28 and 57 percent of feet initially thought to harbor a neuroma, respectively.
Resected nerves have no pathognomonic changes, although in one study of surgical specimens from patients with symptoms of intermetatarsal neuroma and plantar nerves obtained at autopsy the largest diameter nerves were surgical specimens while the smallest were from the autopsy group. Nerve swelling was calculated to have a sensitivity of 78 percent and specificity of 80 percent. This provides some support for the usefulness of MRI assessment of nerve size as a confirmatory test.
Treatment — Conservative treatment should precede expensive diagnostic procedures; this involves decreasing stresses at the metatarsal heads with the use of a metatarsal support, metatarsal bar, or a comma-shaped metatarsal shoe insert. External appliances should be placed on both shoes so that the patient walks evenly, even when symptoms are unilateral. A broad-toed shoe that allows spreading of the metatarsal heads or an extra-depth shoe is helpful.
Injection of a local anesthetic–corticosteroid injection into the site of compression can be beneficial; methylprednisolone 20 mg (0.5 mL) mixed with 0.5 mL 1 percent lidocaine should suffice. The injection should precede consideration for surgery since an intermetatarsal bursitis is common, and the injection and use of proper shoes may provide a cure. When the neuroma is evident, injection may only provide transient benefit.
Surgical removal of the neuroma and nerve may be required in those who are resistant to nonoperative therapy; patients still benefit from wearing adapted shoes after surgery. In one post-operative study of 31 patients, for example, only 30 percent had no restrictions in the choice of their shoes at long term follow-up. Others report surgical success rates of up to 80 to 90 percent.
