What Is Morton’s Neuroma Ethanol Ablation?
A Morton’s neuroma is frequently considered to be a result of repetitive compression upon the common plantar digital nerve most frequently involving the third web space of the forefoot, and less commonly the second web space. Whatever the underlying aetiology may be; the end result is “perineural fibrosis of the common plantar digital nerve”. This leads to swelling of the digital nerve and the reproduction of a severe intermittent pain to the toes, especially during the toe – off phase of walking and running.
The treatment options for a Morton’s neuroma include conservative management with biomechanical alterations including orthotics. Consideration may be given to an ultrasound guided injection with cortisone and local anaesthetic and this provides relief for up to 3 months in most cases.
Ethanol injected around a nerve produces chemical neurolysis through dehydration, necrosis, and precipitation of protoplasm. The maximum effect appears to be in large myelinated fibers. These are the nerve fibres within a neuroma that carry pain signals.
Ethanol ablation procedure involves using an ultrasound transducer to guide a small needle within the neuroma, after infiltration with local anaesthetic initially. A very small amount of ethanol mixed with long acting local anaesthetic is then injected centrally in the neuroma with constant ultrasound visualisation. This procedure may take about 10 seconds. There may be very mild discomfort during the injection. After the injection has been completed, a small skin plaster will be placed at the site of the injection. This can be removed at the following day.
It is recommended that you rest for at least 24 hours after the ethanol injection to limit the degree of localised pain. It is beneficial to elevate the foot and apply ice packs for 20 minutes each two hours during the first 24 hours. If there is significant discomfort, you may require simple analgesic medication such as Panadol or anti-inflammatory medication e.g. Voltaren. The ethanol injection is repeated on three further occasions at two weekly intervals. Research has shown that having completed for ethanol injections there is an 80% chance of having significant reduction of the pain.
The procedure risks are infrequent, however there is a small chance of worsened pain, or no significant improvement of pain, infection at the injection site, localised bruising and nerve damage with loss of sensation are potential risks. Some patients do report having increased swelling, redness and pain for all up to 2 weeks after the injections. In most cases this gradually improves and there is an overall improvement within three months.
The ethanol ablation treatment, whilst effective in approximately 80% of patients, may be ineffective in up to 20% of patients. These patients can still undergo other treatments to cure the neuroma, including radiofrequency ablation or surgical excision.
Radiofrequency ablation uses an electrode needle inserted under ultrasound guidance which emits a thermal energy capable of destructing the neuroma. Please see the associated information sheet regarding this radiofrequency procedure.