Symposium: Congenital anomalies of the middle ear. II. Vascular anomalies of the middle ear.

Of all the abnormal situations that one encounters in performing a tympanotomy, probably the last one to be thought of is vascular anomalies, and yet, potentially, this is one of the most hazardous of anomalous problems with which we have to deal. Most of the anomalies which have been reported concern the persistent stapedial artery. This artery arises from the stump of the second aortic arch (stapedio-hyoid artery), it traverses the developing stapes bone, leaving behind a monument to its existence - the obturator foramen of the stapes. The artery exits from the middle ear along the horizontal portion of the facial nerve, traversing this area for a variable distance and then usually divides into an intra-cranial branch and a sphenoidal branch. The stapedial artery in its development before its regression, gives rise to the anlage of many important cranial arteries. These vessels are usually anastomosed with and distributed by the branches of the internal maxillary artery and the ophthalmic artery. The hyoid artery is represented in the adult by the carotico tympanic artery. Anomalies involving the internal carotid artery are much more rare. The anomalies that have thus far been reported are: 1. Absence of the internal carotids. 2. Aneurysms. 3. Unusual courses. Venous anomalies are generally uncommon and are usually represented by an abnormally placed jugular bulb which can simulate a glomus jugulari tumor.