Effects of alcohol injection in rat sciatic nerve as a model for Morton's neuroma treatment

Previous studies have shown that the injection of dehydrated alcohol has been successful for the treatment of Morton's neuroma in the foot. In this study, we determined the cellular effect of injection of alcohol into and around the sciatic nerve of rats and measured the extent of cell necrosis and/or any associated histologic or inflammatory changes.

Twenty-two male (~375 g) Wistar rats were randomized into 2 groups each receiving alcohol injections into or around the sciatic nerve after nerve exposure under sterile technique. Group 1 rats were injected with a 0.5 ml solution of 0.5% Marcaine in the left sciatic nerve as a control group. In the right sciatic nerve a 0.5 ml solution of 4% ethanol with 0.5% Marcaine was injected. Group 2 rats received 0.5 ml of 20% ethanol with 0.5% Marcaine injected into the left sciatic nerve and 0.5 ml of 30% ethanol with 0.5% Marcaine injected into the right sciatic nerve. In each group, the rats were placed in 3 subgroups: intraneural, perineural, perimuscular injections. All rats were sacrificed and tissue harvested for histologic evaluation at day 10 post injection.

No evidence of alcohol-associated cell necrosis, apoptosis, or apparent inflammation was observed in histologic specimens of any injected nerves, perineural tissue, or muscles in controls or experimental groups regardless of concentration of ethanol injected on day 10.

We concluded that alcohol injection (≤30% ethanol) into and/or around the sciatic nerve or the adjacent muscle of rats has no histologic evidence of necrosis or inflammation to the nerve or surrounding tissue. There was no observable histological change in apoptosis, or cell number, in response to the alcohol injection.

The lack of any measureable changes in nerve or adjacent muscle histology with ethanol injection into the rat sciatic nerve (and surrounding tissues) raises questions about the efficacy of using ethanol injections in the treatment of Morton's neuroma in human clinical practice.