Cryosurgery Or Sclerosing Injections: Which Is Better For Neuromas?
Cryogenic neuroablation is a safe, minimally invasive option that is less painful than alcohol injections and may facilitate a reduced risk of stump neuromas, according to this author.
By Lawrence Fallat, DPM
Morton’s neuroma (perineural fibroma) is a common painful forefoot disorder that can present treatment challenges to all podiatric physicians. The common digital nerves, usually in the second and third intermetatarsal spaces, become enlarged in the area of the deep transverse metatarsal ligament and subsequently cause pain in the ball of the foot with cramping, pain and numbness of the toes.
Histological findings of the nerve include endoneural edema with perineural, epineural and endoneural fibrosis. Endarterial thickening occurs along with axonal loss and demyelination. These findings are consistent with a degenerative process and it is generally accepted that this occurs as a result of nerve entrapment.
Conservative treatment consists of shoe modification, orthotics, NSAIDs and steroid injections. Neurolytic agents such as phenol and, more commonly, diluted 4% alcohol have been advocated.1 When conservative treatment fails, surgical intervention may be indicated. Excision of the neuroma is the most common surgical procedure performed but significant failure rates have been reported.2,3 Poor results can occur from incomplete excision or the formation of a stump neuroma that can be more troublesome than the original pain.
With this in mind, one should consider the possible use of cryogenic neuroablation, which describes the destruction of axons to prevent them from carrying painful impulses. This technique involves applying extremely cold temperatures between –50ºC and –70ºC to the nerve. This results in degeneration of the intracellular elements, axons and myelin sheath with Wallerian degeneration.4
These changes are consistent with a second-degree nerve lesion. The epineurium and perineurium remain intact, and this prevents the formation of stump neuromas as the nerve regenerates. The preservation of these structures differentiates cryosurgery from surgical excision and neurolytic agents.