A case of double-innervation of the anterior belly of the digastric muscle by the mylohyoid and facial nerves

The anterior belly of the left digastric muscle of a 75 year old woman was found to be innervated both by the mylohyoid nerve, which entered the deep surface, and by a branch of the stylohyoid branch of the facial nerve, which was distributed in the lateral two-thirds of the more superficial half of the muscle belly. The stylohyoid muscle attached to the hyoid bone by two insertions, neither of which, however, passed superficial to the intermediate tendon of the digastric. It may not be quite impossible to regard this anomaly as showing a transitional stage of the innervation change (Futamura 1906), but origin and course of the anomalous nerve does not agree with that of the embryonal stage. It is suggested, that the part of the normal stylohyoid muscle, which lies superficial to the intermediate tendon, would have been fused to the anterior belly.