Some sources claim that entrapment of the plantar nerve because of compression between the metatarsal heads, as originally proposed by Morton, is highly unlikely, because the plantar nerve is on the plantar side of the transverse metatarsal ligament and thus does not come in contact with the metatarsal heads. It is more likely that the transverse metatarsal ligament is the cause of the entrapment. Despite the name, the condition was first correctly described by a chiropodist named Durlacher, and although it is labeled a "neuroma", many sources do not consider it a true tumor, but rather a perineural fibroma (fibrous tissue formation around nerve tissue).
The cause of this problem is often due to impingement of the plantar nerve fibres between the metatarsal heads and the intermetatarsal ligament. It is entirely a biomechanical phenomenon. Differential diagnoses include stress fracture, capsulitis, bursitis or ligament injury at the metatarsal-phalangeal joint, a tendon sheath ganglion, foreign-body reaction and nerve-sheath tumour.
The symptoms of Morton?s Neuroma tend to come and go over time. They are typically exacerbated by physical activity or by wearing certain shoes. Morton?s Neuroma symptoms include sharp pain in the ball of the foot, pain radiating to the tips of the toes, burning pain in the second, third, or fourth toes, numbness in the toes, sensation of a lump between the toes.
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
Treatment strategies for Morton's neuroma range from conservative to surgical management. The conservative approach to treating Morton's neuroma may benefit from the involvement of a physical therapist. The physical therapist can assist the physician in decisions regarding the modification of footwear, which is the first treatment step. Recommend soft-soled shoes with a wide toe box and low heel (eg, an athletic shoe). High-heeled, narrow, nonpadded shoes should not be worn, because they aggravate the condition. The next step in conservative management is to alter alignment of the metatarsal heads. One recommended action is to elevate the metatarsal head medial and adjacent to the neuroma, thereby preventing compression and irritation of the digital nerve. A plantar pad is used most often for elevation. Have the patient insert a felt or gel pad into the shoe to achieve the desired elevation of the above metatarsal head. Other possible physical therapy treatment ideas for patients with Morton's neuroma include cryotherapy, ultrasonography, deep tissue massage, and stretching exercises. Ice is beneficial to decrease the associated inflammation. Phonophoresis also can be used, rather than just ultrasonography, to further decrease pain and inflammation.
The ultimate success of a Morton?s neuroma treated surgically is somewhat unclear. This is likely due to the idea that in most instances a ?Morton?s neuroma? is actually more than just an isolated nerve problem but rather consitutes a metatarsalgia where other structures (such a as the MTP joints) are also problematic, not just the nerve. Therefore, addressing the nerve as well as the other components of a metatarsalgia may offer a better chance of surgical success. However, like many conditions in foot and ankle, it is ideal if this condition can be managed without surgery.