Foramina
There are several bony landmarks and foramina present in the posterior cranial fossa (a foramen is simply a hole that allows the passage of a structure – usually a blood vessel or nerve).
Temporal Bone
The internal acoustic meatus is an oval opening in the posterior aspect of the petrous part of the temporal bone. It transmits the facial nerve (CN VII), vestibulocochlear nerve (CN VIII) and labyrinthine artery.
Occipital Bone
A large opening, the foramen magnum, lies centrally in the floor of the posterior cranial fossa. It is the largest foramen in the skull. It transmits the medulla of the brain, meninges, vertebral arteries, spinal accessory nerve (ascending), dural veins and anterior and posterior spinal arteries. Anteriorly an incline, known as the clivus, connects the foramen magnum with the dorsum sellae.
The jugular foramina are situated either side of the foramen magnum. Each transmits the glossopharyngeal nerve, vagus nerve, spinal accessory nerve (descending), internal jugular vein, inferior petrosal sinus, sigmoid sinus and meningeal branches of the ascending pharyngeal and occipital arteries.
Immediately superior to the anterolateral margin of the foramen magnum is the hypoglossal canal. It transmits the hypoglossal nerve through the occipital bone.
Posterolaterally to the foramen magnum lies the cerebellar fossae. These are bilateral depressions that house the cerebellum. They are divided medially by a ridge of bone, the internal occipital crest.
