The anatomy of the jugular foramen region is complex and important neurovascular structures are involved. These structures are in close relation with the cervical region, ear, and brainstem. A precise knowledge of this anatomical relationship is fundamental to properly expose a tumor originating at or involving the jugular foramen. The Jugular foramen is located on the medial and inferior surface of the petrous pyramid and is formed by the occipital and temporal bones. It is a depression around the sigmoid sinus, jugular bulb, and inferior petrous sinus in close relationship with the magnum foramen, internal auditory canal , and the hypoglossal canal (Figs. 5.1–5.4) [1, 2]. In most cases the width of the right jugular foramen is larger than that of the left one [3].

Classically the JF is described as having two portions [4]. The nervous portion with the glossopharyngeal nerve, the inferior petrosal sinus, and the meningeal branches of ascending pharyngeal artery and the venous portion with the sigmoid sinus, vagal, and accessory nerves (Fig. 5.5). The vascular structures within the jugular foramen are: the sigmoid sinus, the jugular bulb, the inferior petrous sinus, and branches of the ascendant faringeal and occipital arteries. The jugular bulb connects the sigmoid sinus and the internal jugular vein. It is located under the floor of the middle ear and its upper portion lies in the jugular fossa (Fig. 5.6). The jugular bulb has a size of approximately 15 mm wide and 20 mm high [5]. Large jugular bulbs enter into the middle ear. In these cases the floor of the middle ear may be dehiscent and this anatomic variation may cause pulsatile tinnitus.

The cranial nerves (IX, X, and XI) are located anterior and medial to the jugular bulb. These nerves cross a connective tissue septum that is in continuity with the pericranium and dura mater. The position of these cranial nerves is an important anatomical parameter because it allows a posterior surgical approach to the jugular bulb with preservation of the nerves. The lower cranial nerves present a multifascicular histoarchitecture (particularly the X cranial nerve) [6]. The tympanic branch of the glossopharyngeal nerve (Jacobson’s nerve) and the auricular branch of the vagal nerve (Arnold’s nerve) may be the site of origin of paragangliomas (Fig. 5.7).

In 1997, Katsuta and Rhoton [7] divided the jugular foramen in three portions: two venous and one nervous (intrajugular) with the nerves IX, X, and XI, between the two venous. Anatomical variations are described in the course of the cranial nerves through the jugular foramen. The vagal nerve is usually formed by multiple fascicles, the glossopharyngeal nerve by one [6], and the accessory nerve is formed by two fascicles : one spinal and one cranial.

Intradural the jugular foramen is related to the cranial nerves IX, X, and XI (with its spinal portion) (Fig. 5.8), superiorly with the VII and VIII cranial nerves with the vertebral, posterior inferior and anterior inferior cerebellar arteries, the medulla oblongata, pons, and upper cervical cord (Fig. 5.9). The internal carotid artery (ICA) is located anterior to the jugular bulb and enters the skull through the carotid canal (Figs. 5.10 and 5.11). The glossopharyngeal, vagus, accessory, and hypoglossal nerves run between the ICA and the internal jugular vein (Fig. 5.12). The C2 or petrous segment of the ICA is inside the petrous portion of the temporal bone. This segment has three portions: an ascending (vertical), the genu, and the horizontal portion (Fig. 5.13). The ICA is located anterior to the tympanic cavity, Eustachian tube, and cochlea (Fig. 5.14). Anatomical vascular variations within the temporal bone as aberrant ICA, high jugular bulb, dehiscent carotid canal, stapedial artery, and high jugular bulb may mimic glomus tumors. They are rare but very important anomalies because misdiagnosing may lead to massive hemorrhage. The caroticotympanic branches of the petrous segment of the ICA may feed the ear portion of the tumor (Fig. 5.15). The C3 (lacerum) segment of the ICA passes through the superior part of the foramen lacerum, is surrounded by periosteum, and gives the vidian artery [8].