ABSTRACT
Botulinum neurotoxins-A [BT-A] are bacterial enzymes that block neurotransmitter release. BT-A is widely used to treat spasticity and dystonias, and also in pharmacocosmetic and in the management of various types of pain. It is therefore important to clarify the histological characteristics involved in muscular tissue postinjection and to reconcile its injection for cosmoses under scope. Fifteen adult albino rats were used in this study and divided into three groups [five rats each]. Group I served as negative control; groups II and III were injected into the right gastrocnemius muscle with BT-A in addition to saline into the left side to serve as positive control. Muscle harvest was examined by LM, EM, and morphometry at 28th day for group II with two rats of group I and at 56th day for group III with three rats of group I. Histological examination revealed neurogenic atrophy, target fiber change, hypertrophied fibers, and dilated aggregates of the sarcotubular system. Neurogenic muscle atrophy following a single BT-A injection should be taken into consideration when repeated BT-A injections into the same muscle are needed