The effect of triamcinolone hexacetonide on the spontaneous and mechanically-induced ectopic discharge following lingual nerve injury in the ferret

Investigations into the aetiology of nerve injury-induced dysaesthesia have revealed the development of spontaneous and mechanically-induced activity from damaged axons. Pharmacological manipulation of this activity could provide a method of treatment for this intractable condition. This study has investigated the effect of a corticosteroid applied to the injury site, as these agents are known to reduce inflammation and scarring. In 24 anaesthetised adult ferrets the left lingual nerve was sectioned and the Animals allowed to recover. In eight of these Animals the nerve was re-exposed under anaesthesia after 1 month and 100 microl of corticosteroid (triamcinolone hexacetonide, 20 mg/ml) was injected into and around the injury site. In eight Others, 100 microl of the steroid carrier was injected, and the eight remaining Animals were used as controls. In terminal experiments under general anaesthesia, 3 months after the initial injury, electrophysiological recordings were made from axons in fine filaments dissected from the nerve central to both the injury site and junction with the chorda tympani nerve. Spontaneous activity (SA) was found in approximately 13% of units in control Animals, 12% following the application of steroid, and 14% in the carrier group. Mechanically-induced activity at the injury site was found in approximately 13% of units in controls, significantly fewer after the application of steroid 4% (P<0.001) and 12% in the carrier group. These data suggest that local application of the corticosteroid triamcinolone hexacetonide could reduce the level of mechanically-induced, but not spontaneous, dysaesthesia following lingual nerve injury.