THE ANATOMY OF THE INFERIOR PETROSAL SINUS, GLOSSOPHARYNGEAL NERVE, VAGUS NERVE, AND ACCESSORY NERVE IN THE JUGULAR FORAMEN

PURPOSE: To define the variations of the courses of the cranial nerves and the inferior petrosal sinuses as they enter and traverse the jugu lar foramen. METHODS: Thirty-nine cadaveric specimens mens containing the jugular foramen were scanned with 1-mm contiguous axial and corona l CT sections. Each specimen was dissected to evaluate the position of the cranial nerves and inferior petrosal sinus as they entered the ju gular foramen. RESULTS: The glossopharyngeal nerve entered the most su perior, anterior, and medial aspect of the jugular foramen and descend ed in the anterior portion:of the jugular foramen, often within a groo ve. The vagus and accessory nerves could not be separated by CT. They entered the jugular foramen most often anterior or anterior and inferi or to the jugular spine of the temporal bone and descended in a positi on ranging from medial to anterior to the jugular vein. The inferior p etrosal sinus most often coursed inferior to the horizontal portion of the glossopharyngeal nerve and entered the jugular system in the jugu lar foramen, at the exocranial opening or below the skull base. A pars nervosa and pars venosa could be identified only at the endocranial o pening, where the jugular spine separated the pars nervosa containing the inferior petrosal sinus and three cranial nerves from the pars ven osa containing the jugular vein. CONCLUSION: Our evaluation demonstrat ed anatomic variation in the area of the jugular foramen.