The foramen spinosum is a hole located in the greater wing of the sphenoid. It is located posterolateral to the foramen ovale and anterior to the

sphenoidal spine The sphenoidal spine (Latin: "''spina angularis''") is a downwardly directed process at the apex of the great wings of the sphenoid bone that serves as the origin of the sphenomandibular ligament. Additional images File:Spine of sphenoid bone ...

. It allows the passage of the

middle meningeal artery The middle meningeal artery ('' la, arteria meningea media'') is typically the third branch of the first portion of the maxillary artery. After branching off the maxillary artery in the infratemporal fossa, it runs through the foramen spinosum to ...

, middle meningeal vein and usually the

meningeal branch of the mandibular nerve The meningeal (recurrent) branch of the mandibular nerve (nervus spinosus) is a branch of the mandibular nerve that supplies the dura mater. Course The meningeal branch of the mandibular nerve enters the skull through the foramen spinosum along w ...

(sometimes it passes through the foramen ovale). The foramen spinosum is often used as a landmark in

neurosurgery Neurosurgery or neurological surgery, known in common parlance as brain surgery, is the medical specialty concerned with the surgical treatment of disorders which affect any portion of the nervous system including the brain, spinal cord and peri ...

, due to its close relations with other cranial foramina. It was first described by Jakob Benignus Winslow in the 18th century.

Structure

The foramen spinosum is a

foramen In anatomy and osteology, a foramen (;Entry "foramen"
in

in the

sphenoid bone The sphenoid bone is an unpaired bone of the neurocranium. It is situated in the middle of the skull towards the front, in front of the basilar part of occipital bone, basilar part of the occipital bone. The sphenoid bone is one of the seven bones ...

of the

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...

. It connects the

middle cranial fossa The middle cranial fossa, deeper than the anterior cranial fossa, is narrow medially and widens laterally to the sides of the skull. It is separated from the posterior fossa by the clivus and the petrous crest. It is bounded in front by the pos ...

to the infratemporal fossa. It is located posterolateral to the foramen ovale, and anterior to the

Variation

The foramen spinosum varies in size and location. The foramen is rarely absent, usually unilaterally, in which case the

enters the

cranial cavity The cranial cavity, also known as intracranial space, is the space within the skull that accommodates the brain. The skull minus the mandible is called the ''cranium''. The cavity is formed by eight cranial bones known as the neurocranium that in ...

through the foramen ovale. It may be incomplete, which may occur in almost half of the population. Conversely, in a minority of cases (less than 1%), it may also be duplicated, particularly when the middle meningeal artery is also duplicated. The foramen may pass through the sphenoid bone at the apex of the spinous process, or along its medial surface.

Development

In the newborn, the foramen spinosum is about 2.25 mm long and in adults about 2.56 mm. The width of the foramen extends from 1.05 mm to about 2.1 mm in adults. The average diameter of the foramen spinosum is 2.63 mm in adults. It is usually between 3 and 4 mm away from the foramen ovale in adults. The earliest perfect ring-shaped formation of the foramen spinosum was observed in the eighth month after birth and the latest seven years after birth in a developmental study of the

foramen rotundum The foramen rotundum is a circular hole in the sphenoid bone of the skull. It connects the middle cranial fossa and the pterygopalatine fossa. It allows for the passage of the maxillary nerve (V2), a branch of the trigeminal nerve. Structure T ...

, foramen ovale and foramen spinosum. The majority of the foramina in the skull studies were round in shape. The

sphenomandibular ligament The sphenomandibular ligament (internal lateral ligament) is one of the three ligaments of the temporomandibular joint. It is situated medially to - and generally separate from - the articular capsule of the joint. Superiorly, it is attached to the ...

, derived from the first

pharyngeal arch The pharyngeal arches, also known as visceral arches'','' are structures seen in the embryonic development of vertebrates that are recognisable precursors for many structures. In fish, the arches are known as the branchial arches, or gill arch ...

and usually attached to the spine of the sphenoid bone, may be found attached to the rim of the foramen.

Animals

In other

great apes The Hominidae (), whose members are known as the great apes or hominids (), are a taxonomic family of primates that includes eight extant species in four genera: '' Pongo'' (the Bornean, Sumatran and Tapanuli orangutan); ''Gorilla'' (the east ...

, the foramen spinosum is found not in the sphenoid, but in parts of the

temporal bone The temporal bones are situated at the sides and base of the skull, and lateral to the temporal lobes of the cerebral cortex. The temporal bones are overlaid by the sides of the head known as the temples, and house the structures of the ears. Th ...

such as the squamous part, found at the

sphenosquamosal suture The sphenosquamosal suture is a cranial suture between the sphenoid bone and the squama of the temporal bone The temporal bones are situated at the sides and base of the skull, and lateral to the temporal lobes of the cerebral cortex. The te ...

, or absent.

Function

The foramen spinosum permits the passage of the

, middle meningeal vein, and the

Clinical significance

Due to its distinctive position, the foramen is used as an

anatomical landmark Anatomical terminology is a form of scientific terminology used by anatomists, zoologists, and health professionals such as doctors. Anatomical terminology uses many unique terms, suffixes, and prefixes deriving from Ancient Greek and Latin. The ...

during

. As a landmark, the foramen spinosum reveals the positions of other cranial foramina, the

mandibular nerve In neuroanatomy, the mandibular nerve (V) is the largest of the three divisions of the trigeminal nerve, the fifth cranial nerve (CN V). Unlike the other divisions of the trigeminal nerve (ophthalmic nerve, maxillary nerve) which contain only aff ...

and

trigeminal ganglion A trigeminal ganglion (or Gasserian ganglion, or semilunar ganglion, or Gasser's ganglion) is the sensory ganglion at the base of each of the two trigeminal nerves (CN V), occupying a cavity (Meckel's cave) in the dura mater, covering the trigemi ...

, foramen ovale, and

. It may also be relevant in achieving

haemostasis In biology, hemostasis American and British English spelling differences#ae and oe, or haemostasis is a process to prevent and stop bleeding, meaning to keep blood within a damaged blood vessel (the opposite of hemostasis is Bleeding, hemorrhage). ...

during surgery, such as for

ligation Ligation may refer to: * Ligation (molecular biology), the covalent linking of two ends of DNA or RNA molecules * In medicine, the making of a ligature (tie) * Chemical ligation, the production of peptides from amino acids * Tubal ligation, a meth ...

of the

. This may be useful in

trauma surgery Trauma surgery is a surgery, surgical Specialty (medicine), specialty that utilizes both operative and non-operative management to treat traumatic injuries, typically in an acute setting. Trauma surgeons generally complete Residency (medicine), ...

to reduce

bleeding Bleeding, hemorrhage, haemorrhage or blood loss, is blood escaping from the circulatory system from damaged blood vessels. Bleeding can occur internally, or externally either through a natural opening such as the mouth, nose, ear, urethra, vag ...

into the

neurocranium In human anatomy, the neurocranium, also known as the braincase, brainpan, or brain-pan is the upper and back part of the skull, which forms a protective case around the brain. In the human skull, the neurocranium includes the calvaria (skull), ...

, or for removal of the pyramidal process of the

palatine bone In anatomy, the palatine bones () are two irregular bones of the facial skeleton in many animal species, located above the uvula in the throat. Together with the maxillae, they comprise the hard palate. (''Palate'' is derived from the Latin ''pa ...

History

The foramen spinosum was first described by the Danish anatomist Jakob Benignus Winslow in the 18th century. It is so-named because of its relationship to the spinous process of the greater wing of the sphenoid bone. However, due to incorrectly declining the noun, the literal meaning is "hole full of thorns" ( la, foramen spinosum). The correct, but unused name would, in fact, be '.

Additional images

File:Skull foramina labeled.svg, alt=Inner surface of the base of skull, showing cranial foramina, Inner surface of the base of skull, showing cranial foramina

References

External links

* – "Osteology of the Skull: Internal Surface of Skull" * – "Schematic view of key landmarks of the infratemporal fossa."
Anatomy of the Skull – 27. Foramen spinosum
{{Authority control Foramina of the skull