Enhanced sensory relearning after nerve repair by using repeated forearm anaesthesia: aspects on time dynamics of treatment.

BACKGROUND: We describe a new principle for enhancing the effects of sensory re-education following nerve injury and repair. The outcome from nerve repair in adult patients is generally poor. One reason is the functional cortical reorganisation which always occurs because of axonal misdirection at the repair site. In healthy individuals selective anaesthesia of the forearm results in improved hand sensation. Here we hypothesised that this principle would be valid also after nerve injury and repair.

METHOD: In a prospective, randomised, double blind study we studied the effects of cutaneous forearm anaesthesia combined with sensory reeducation on the outcome after median or ulnar nerve repair at wrist or distal forearm level.

FINDINGS: EMLA-application four times over a two week period starting with beginning reinnervation of the fingers resulted in significantly improved sensory recovery (tactile gnosis) as compared to the placebo group and also at assessment four weeks after the last EMLA-session. However, at assessment 8-11 months after the first EMLA-treatment there was no difference between the groups.

CONCLUSIONS: Our findings indicate that repeated cutaneous forearm anaesthesia over a two week period can enhance the effects of sensory re-education at least over the four following weeks. However, the optimal time protocol for EMLA-treatment, aiming at a long-lasting or permanent effect on sensory recovery still has to be defined.