Fluctuating and intermittent facial weakness following a local anaesthetic.

Considering the extensive use of local anaesthetics, especially in dental anaesthesia, it is surprising that injury to peripheral nerves, as a result of the injection, appears to be rare. During local anaesthesia of the maxillary nerve territory it is not uncommon for there to be a little weakness of the cheek and lip muscles, presumably due to spread of local anaesthesia into the proximity of facial nerve branches, but this invariably recovers as the effect of the local anaesthetic wears off. Muscle weakness, Which is the result of a partial lesion of a peripheral nerve, is usually fairly constant and is relatively unaffected by use of the muscle, though the muscle may fatigue more readily. Cooling of the muscle, however, may increase its weakness a little. The patient we are about to describe appears to show two unique features. First, a partial lesion of the branches of the facial nerve was sustained during an injection for dental anaesthesia. Secondly, the weakness of the affected muscles was considerably increased by activity of facial muscles or by cooling the cheek.