It consists of a downward displacement of the cerebellar tonsils and the medulla through the foramen magnum, sometimes causing hydrocephalus as a result of obstruction of cerebrospinal fluid outflow.

* Coning a brain herniation in which the cerebellar tonsils move downwards through the foramen magnum

Also, the specimen showed short canine teeth, and the position of the foramen magnum was evidence of bipedal locomotion.

This was made possible by the evolution of locking knees and a different location of the foramen magnum ( the hole in the skull where the spine enters ).

The skull is large, with a narrow foramen magnum, and relatively small skull base.

Cranial features show a flatter face, u-shaped dental arcade, small canines, an anterior foramen magnum, and heavy brow ridges.

Because no postcranial remains ( bones below the skull ) have been discovered, it is as of yet unknown whether Sahelanthropus tchadensis was indeed bipedal or two-footed, although claims for an anteriorly placed foramen magnum suggests that this may have been the case, some paleontologists have disputed this interpretation of the basicranium.

Increased intracranial pressure can cause parts of the brain to herniate through narrowed portions of the cranial cavity or through the foramen magnum.

Finally, the skull tapers towards the rear, where the foramen magnum lies immediately above a single condyle, articulating with the first vertebra.

The base of the cranium is formed from a ring of bones surrounding the foramen magnum and a median bone lying further forward ; these are homologous with the occipital bone and parts of the sphenoid in mammals.

It consists of a downward displacement of the cerebellar tonsils through the foramen magnum ( the opening at the base of the skull ), sometimes causing non-communicating hydrocephalus as a result of obstruction of cerebrospinal fluid ( CSF ) outflow.

These fibers coalesce to form spinal rootlets, roots, and finally the spinal accessory nerve itself, which enters the skull through the foramen magnum, the large opening at the base of the skull.

In anatomy, the foramen magnum ( Latin: ' great hole ') is a large opening in the occipital bone of the cranium.

Apart from the transmission of the medulla oblongata and its membranes, the foramen magnum transmits the spinal accessory nerve, vertebral arteries, the anterior and posterior spinal arteries, the membrana tectoria and alar ligaments.

In humans, the foramen magnum is farther underneath the head than in great apes.

Comparisons of the position of the foramen magnum in early hominid species are useful to determine how comfortable a particular species was when walking on two limbs ( bipedalism ) rather than four ( quadrupedalism ).

It lies within the suboccipital triangle along with the vertebral artery, where the artery enters the foramen magnum.

Cervical vertebrae possess transverse foramina to allow for the vertebral arteries to pass through on their way to the foramen magnum to end in the circle of Willis.

It is pierced by a large oval aperture, the foramen magnum, through which the cranial cavity communicates with the vertebral canal.

* The curved, expanded plate behind the foramen magnum is named the squama occipitalis.

The foramen magnum ( Latin for large hole ) is a large oval aperture with its long diameter antero-posterior ; it is wider behind than in front where it is encroached upon by the condyles.

In most higher vertebrates, the foramen magnum is surrounded by a ring of four bones.

Most mammals also have a single fused occipital bone, formed from the four separate elements around the foramen magnum, along with the paired postparietal bones that form the rear of the cranial roof in other vertebrates.

Finally, the skull tapers towards the rear, where the foramen magnum lies immediately above a single condyle, articulating with the first vertebra.

* The otic ganglion is situated directly under the foramen, but is also transmitted through the foramen ovale.

* Infraorbital foramen, an opening in the skulle under the eye socket

The ophthalmic, maxillary and mandibular branches leave the skull through three separate foramina: the superior orbital fissure, the foramen rotundum and the foramen ovale.

Upon emerging from the lateral aspect of the medulla the branchial motor component joins the other components of CN IX to exit the skull via the jugular foramen.

The glossopharyngeal fibers travel just anterior to the cranial nerves X and XI, which also exit the skull via the jugular foramen.

It then proceeds anteriorly to exit the skull via the foramen ovale along with the mandibular component of CN V ( V3 ).

Upon exiting the skull, the lesser petrosal nerve synapses in the otic ganglion, which is suspended from the mandibular nerve immediately below the foramen ovale.

The central processes of these neurons enter the skull via the jugular foramen.

From the anterior portion of the medulla oblongata, the glossopharyngeal nerve passes laterally across or below the flocculus, and leaves the skull through the central part of the jugular foramen.

Upon exiting the skull via the jugular foramen, the spinal accessory nerve pierces the sternocleidomastoid muscle before terminating on the trapezius muscle.

The nerve courses along the inner wall of the skull towards the jugular foramen, through which it exits the skull with the glossopharyngeal ( CN IX ) and vagus nerves ( CN X ).

At the base of the skull the foramen ovale ( Latin: oval window ) is one of the larger of the several holes ( the foramina ) that transmit nerves through the skull.

The cervical segment, or C1, of the internal carotid extends from the carotid bifurcation until it enters the carotid canal in the skull anterior to the jugular foramen.

# obex: represents the caudal tip of the fourth ventricle ; the obex is also a marker for the level of the foramen magnum of the skull and therefore is a marker for the imaginary dividing line between the medulla and spinal cord.

If some of the inert gas-laden blood passes through the patent foramen ovale ( PFO ), it avoids the lungs and the inert gas is more likely to form large bubbles in the arterial blood stream, causing decompression sickness.

In addition, the specimen exhibited short canine teeth, and the foramen magnum was more anteriorly placed, suggesting a bipedal mode of locomotion.

While the foramen ovale and ductus arteriosus are open after birth, some mixing of red and blue blood occurs allowing a small amount of oxygen to be delivered to the body ; if ASD, VSD, PFO, and / or PDA are present, this will allow a higher amount of the red and blue blood to be mixed, therefore delivering more oxygen to the body, but can complicate and lengthen the corrective surgery and / or be symptomatic.

In a large randomized controlled trial the higher prevalence of patent foramen ovale in migraine patients was confirmed, but migraine headache cessation was not more prevalent in the group of migraine patients that underwent closure of their patent foramen ovale.

When computed tomography or, more specifically, cone beam computed tomography or CBCT ( 3D X-ray imaging ) is used preoperatively to accurately pinpoint vital structures including the inferior alveolar canal, the mental foramen, and the maxillary sinus, the chances of complications might be reduced as is chairtime and number of visits.

The superior orbital fissure is a foramen in the skull, although strictly it is more of a cleft, lying between the lesser and greater wings of the sphenoid bone.

Skull fractures occur more easily at the thin squamous temporal and parietal bones, the sphenoid sinus, the foramen magnum ( the opening at the base of the skull through which the spinal cord passes ), the petrous temporal ridge, and the inner portions of the sphenoid wings at the base of the skull.