General
- Located between the temporal bone and the occipital bone
- Size
- Rt > Lt: 68% of the cases
- Rt= Lt: 12%
- Rt<Lt 20%
- Roof of the jugular foramen is formed by
- Pyramidal fossa = covers the Pars Nervosa
- Intrajugular process = Dural septum
- Jugular notch = Pars vascularis
- The appearance of the jugular foramen is anatomically variable, and sometimes both cranial nerves IX and X traverse through the pars nervosa.
- The right jugular foramen is larger than the left in 75% of the population.
- When the roof of the jugular bulb is seen above the level of floor of IAC, it is called a high riding jugular bulb, which is more common on the right side.
- This is a dangerous variant & exposing during translabyrinthine surgery.
Contents
- Venous
- Sigmoid sinus and jugular bulb
- Inferior petrosal sinus
- Artery
- Meningeal branches of the ascending pharyngeal and occipital arteries
- CN + ganglia
- CN9
- Tympanic branch of the CN9 (Jacobson's nerve)
- CN10
- Auricular branch of the CN10 (Arnold's nerve)
- CN11
- Cochlear aqueduct
- The sigmoid sulcus makes a sharp turn just before emptying into the sigmoid portion of the jugular foramen.
- The inferior petrosal sinus extends along the petroclival fissure and enters the petrosal part of the foramen.
- The nerves enter the intrajugular part of the foramen located between the sigmoid and petrosal parts.
- The outlined area shows the approximate site from which B to F were taken.
- The sigmoid sinus descends in the sigmoid sulcus and makes a sharp anterior turn to enter the jugular foramen.
- The jugular bulb extends upward under the petrous temporal bone toward the internal acoustic meatus.
- The endolymphatic sac is located above the lower portion of the sigmoid sinus on the back of the temporal bone and opens above through the vestibular aqueduct into the vestibule.
- The glossopharyngeal, vagus and accessory nerves penetrate the dura on the medial side of the intrajugular process vein.
- The nerves penetrate the dura on the medial side of the intrajugular process of the temporal bone.
- The intrajugular ridge extends forward along the medial side of the jugular bulb.
- The CN9 passes forward along the medial side of the intrajugular ridge, but the vagus and accessory nerves, although entering the dura on the medial side of the intrajugular process, almost immediately turn downward and do not course along the medial edge of the intrajugular ridge in the medial wall of the jugular bulb, as does the glossopharyngeal nerve.
- The auricular branch of the vagus nerve (Arnold’s Nerve)
- Arises from the CN10
- Passes along the groove in the anterior wall of the jugular fossa → penetrates the mastoid canaliculus in the lateral wall of the fossa.
- The intrajugular process of the temporal bone projects backward to join the intrajugular process of the occipital bone, thus forming an osseous bridge that divides the foramen into two parts.
- The vagus and accessory nerves pass lateral to the osseous bridge and the inferior petrosal sinus descends below the bridge to open into the internal jugular vein
- CN 9 pass medial to the osseous bridge
- The hypoglossal nerve has been exposed on the lateral side of the occipital condyle.
- It exits the hypoglossal canal and joins the glossopharyngeal, vagus, and accessory nerves below the jugular foramen in the interval between the internal carotid artery and internal jugular
Has 3 parts
Larger lateral part
- Aka
- Sigmoid part
- Pars vascularis
- Receives the drainage of the sigmoid sinus
- Contains
- Sigmoid sinus
- CN 10 (and its auricular branch)
- CN 11
Intrajugular part
- Separates the pars Vascularis and Pars Nervosa
- Formed by
- Intrajugular process of the occipital bone
- Intrajugular process of the temporal bone.
- The processes are joined together
- By a fibrous link:
- Dural septum (more intracranial portion of the jugular foramen)
- Intrajugular septum
- By a osseous link:
- Osseous bridge (aka intrajugular ridge) (more extracranial portion of the jugular foramen)
Smaller medial part
- Aka
- Petrosal part
- Pars Nervosa
- Receives the drainage of the inferior petrosal sinus.
- Contains
- CN 9
- CN9's tympanic branch (Jacobson’s nerve)
- Inferior petrosal sinus
- Meningeal branches of the ascending pharyngeal artery
Bony anatomy
Ac., acoustic; Car., carotid; Coch., cochlear; Cond., condyle; Fiss., fissure; For., foramen; Hypogl., hypoglossal; Int., internal; Intrajug., intrajugular; Jug., jugular; Mast., mastoid; Occip., occipital; Pet., petrous; Petrocliv., petroclival; Post., posterior; Proc., process; Sig., sigmoid; Squam., squamosal; Stylomast., stylomastoid; Temp., temporal; Vest., vestibular. Aur., auricular; Br., branch; Canalic., canaliculus; Car., carotid; CN, cranial nerve; Cond., condyle; Ext., external; Fiss., fissure; For., foramen; Jug., jugular; Mandib., mandibular; Occip., occipital; Petrotymp., petrotympanic; Proc., process; Trans., transverse; Tymp., tympanic.
- Jugular foramen
- Located between the temporal and occipital bones.
- One cannot see directly through the foramen from above, as shown, because it is directed forward under the temporal bone.
- Sigmoid groove descends along the mastoid and crosses the occipitomastoid suture where it turns forward on the upper surface of the jugular process of the occipital bone and enters the foramen by passing under the posterior part of the petrous temporal bone.
- The glossopharyngeal, vagus, and accessory nerves pass through the intrajugular portion of the foramen located between the sigmoid and petrosal parts.
- The right jugular foramen often being larger as shown.
- Cochlear aqueduct
- Opens just above the anterior edge of the petrosal part.
- Vestibular aqueduct
- Opens into the endolymphatic sac, which sits on the back of the temporal bone superolateral to the sigmoid part of the jugular foramen.
- One cannot see directly through the foramen from below because the foramen is covered above by the part of the petrous temporal bone forming the jugular fossa, which houses the jugular bulb.
- The entrance into the carotid canal is located directly in front of the medial half of the jugular foramen.
- The stylomastoid foramen is located lateral and the anterior half of the occipital condyle medial to the jugular foramen.
- The posterior condylar foramen is transversed by an emissary vein, which joins the sigmoid sinus. The hypoglossal canal passes above the middle third of the occipital condyle and opens laterally into the interval between the jugular foramen and carotid canal.
- The roof over the foramen formed by the jugular fossa of the temporal bone is shaped to accommodate the jugular bulb.
- The posterior margin of the foramen is formed by the jugular process of the occipital bone, which connects the basal (clival) part of the occipital bone to the squamosal part.
- The petroclival fissure intersects the anteromedial margin of the petrosal part of the foramen.
- The sutures have been forced open to show the relationship of the foramen to the
- Petroclival sutures
- Occipitomastoid sutures
- The hamate process normally extends along the medial edge of the petrosal part of the foramen to the adjacent part of the temporal bone, but in this case the sutures were forced open, leaving an interval between the hamate process and the temporal bone.
- Intrajugular ridge
- Extends forward from the intrajugular process along the medial side of the jugular bulb.
- CN9 passes forward along the medial side of the intrajugular process and ridge.
- CN10, 11 enter the dura on the medial side of the process, but quickly descend and do not pass forward along the medial edge of the ridge as does the CN9.
- The jugular process of the occipital bone often has a small prominence on its surface that projects toward the intrajugular process of the temporal bone, and in some foramina, the intrajugular processes of the two bones are joined by an osseous bridge that converts the foramen into two osseous foramina.
- In this case, the intrajugular process of the occipital bone is absent.
- The cochlear aqueduct opens above the petrosal part of the foramen and the site where the CN9 enters the intrajugular part of the foramen on the medial side of the intrajugular process.
- The vestibular aqueduct opens onto the posterior surface of the temporal bone superolateral to the jugular foramen.
Relationships around the jugular foramen
- Relation
- Lateral to jugular foramen
- Styloid process
- facial nerve
- Anterior to jugular foramen
- Mandibular condyle
- Posterior to jugular foramen
- Vertebral artery ascending through the C1 transverse process
- The transverse process of C1 sits behind and often indents the posterior wall of the internal jugular vein.
- Medial to jugular foramen
- Anterior half of occipital condyle
- The temporal bone forms the dome over the jugular bulb. The jugular process of the occipital bone forms the posterior margin of the jugular foramen.
- The jugular foramen and carotid canal are separated by a narrow bony ridge, which is penetrated medially by the tympanic canaliculus through which passes the tympanic branch of the glossopharyngeal nerve (Jacobson's nerve).
- This branch of the nerve passes forward across the promontory in the medial part of the tympanic cavity, then crosses the floor of the middle fossa as the lesser petrosal nerve, and eventually reaches the otic ganglion, providing parasympathetic innervation to the parotid gland.
- The anterior wall of the sigmoid part of the foramen is the site of a shallow groove across which the auricular branch of the vagus nerve (Arnold's nerve) passes to enter the mastoid canaliculus. It exits the mastoid through the tympanomastoid suture.
- A small fiber (arrow) placed in the tympanic canaliculus, shown in B, exits the canaliculus in the middle ear where the fibers of the tympanic branch of the glossopharyngeal nerve cross the promontory, and then regroup to cross the floor of the middle fossa as the lesser petrosal nerve
Made with Bullet