THE "CAVERNOUS " SINUS* BY

THE cavernous sinus is a vascular channel of great importance not only in ophthal-mology but in many other branches of medicine. Descriptions of its structure are scattered in books and journals on ophthalmology, otorhinolaryngology, paediatrics, and dentistry as well as in the standard anatomical works. However, the descrip-tions of the sinus and its contents show great variation and it is the purpose of this paper to clarify the matter. Probably the earliest description of this sinus was by Ridley (1695), who placed the internal carotid artery against the lateral wall, "leaving no room at all for either blood or serum to be contained there". He noted with regard to the artery "a little interstice between itselfand the pituitary gland", and how this venous space communi-cated with that of the opposite side. The term "circular sinus " was suggested in his book, a name still sometimes applied. The presence of the fibrous trabeculae was first noted by Winslow (1732), but his description of the other structures is not clear: "The internal carotid is bathed in the blood of the sinus together with the third, fourth, fifth and sixth pairs of nerves. " It was Winslow who likened the interior of the sinus to that of the corpus cavernosum of the penis and applied the term "caver-nous", which has been used ever since. The classic description is that of a blood-filled channel completely surrounding the horizontal portion ofthe internal carotid artery and the sixth (abducent) nerve as they pass anteriorly on either side of the sella turcica (Fig. 1). In addition to these two structures, the lumen of the cavernous sinus is usually described as being crossed by numerous fibrous laminae, termed trabeculae, and always depicted as a dense, interlacing mass. This description of the artery, the sixth nerve, and the trabecula