This report describes the structure of the temporal bone and of the facial nerve in relation to the pathological condition and treatment of Bell's palsy. Although the nerve is relatively avascular in the normal state, the connective tissue layer external to the nerve "sheath" contains a rich arterial supply with its accompanying venous drainage system. In addition, a wealth of vascular channels in the bone brings the contents of the facial canal into close relationship with surrounding tissue of petrous air cells and the mucous membrane that lines the middle ear cavity.
Barry J. Anson, James A. Donaldson, Raymond L. Warpeha, Michael J. Rensink, Bruce B. Shilling. Surgical Anatomy of the Facial Nerve. Arch Otolaryngol. 1973;97(2):201–213. doi:10.1001/archotol.1973.00780010207026