Morton neuroma (interdigital neuroma), first described in 1876, is a perineural fibrosis and nerve degeneration of the common digital nerve. Morton neuroma, or Morton’s neuroma, is not a true neuroma, although it results in neuropathic pain in the distribution of the interdigital nerve secondary to repetitive irritation of the nerve. The most frequent location is between the third and fourth metatarsals (third webspace). Other, less common locations are between the second and third metatarsals (second webspace) and, rarely, between the first and second (first webspace) or fourth and fifth (fourth webspace) metatarsals.
Poorly fitted footwear can be a cause. Shoes that have a tight and narrow toe box can cause the never to become entrapped causing the pain. High heeled shoes abnormally place the metatarsals under extreme pressure which can cause Morton?s Neuroma. In cases of abnormal pronation, there can be significant motion between the 3rd and 4th metatarsals which can cause an irritation to the nerve that runs between them. This inflammation causes the pain.
Symptoms include: pain on weight bearing, frequently after only a short time. The nature of the pain varies widely among individuals. Some people experience shooting pain affecting the contiguous halves of two toes. Others describe a feeling like having a pebble in their shoe or walking on razor blades. Burning, numbness, and paresthesia may also be experienced. Morton’s neuroma lesions have been found using MRI in patients without symptoms.
The clinical symptoms should quickly lead your doctor to suspect a neuroma. When examined, the doctor may feel a “click” which is known as Mulder’s sign. There may be tenderness in the interspace. The metatarsal bones will also be examined both clinically (and often with an xray). Tenderness at one of the metatarsal bones can suggest an overstress reaction (pre-stress fracture or stress fracture) in the bone. An ultrasound scan can confirm the diagnosis and is a less expensive and at this time, at least as sensitive a test as an MRI. An x-ray does not show neuromas, but can be useful to “rule out” other causes of the pain.
Non Surgical Treatment
Nonsurgical treatment is tried first. Your doctor may recommend any of the following. Padding and taping the toe area, shoe inserts, changes to footwear, for example wearing shoes with wider toe boxes or flat heels, Anti-inflammatory medicines taken by mouth or injected into the toe area, nerve blocking medicines injected into the toe area, other painkillers, physical therapy. Anti-inflammatories and painkillers are not recommended for long-term treatment. In some cases, surgery is needed to remove the thickened tissue and inflammed nerve. This helps relieve pain and improve foot function. Numbness after surgery is permanent.
Recently, an increasing number of procedures are being performed at specialist centers under radiological or ultrasound guidance. Recent studies have shown excellent results for the treatment of Morton’s neuroma with ultrasound guided steroid injections, ultrasound guided sclerosing alcohol injections, ultrasound guided radiofrequency ablation and ultrasound guided cryo-ablation.