Foramen Spinosum
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The foramen spinosum is a small open hole in the greater wing of the sphenoid bone that gives passage to the
middle meningeal artery The middle meningeal artery (') is typically the third branch of the maxillary artery#First portion, first portion of the maxillary artery. After branching off the maxillary artery in the infratemporal fossa, it runs through the foramen spinosum t ...
and vein, and the
meningeal branch of the mandibular nerve The meningeal branch of the mandibular nerve (also known as the nervus spinosus) is a sensory branch of the mandibular nerve (CN V3) that enters the middle cranial fossa through either the foramen spinosum or foramen ovale to innervate the menin ...
(sometimes it passes through the foramen ovale instead). The foramen spinosum is often used as a landmark in
neurosurgery Neurosurgery or neurological surgery, known in common parlance as brain surgery, is the specialty (medicine), medical specialty that focuses on the surgical treatment or rehabilitation of disorders which affect any portion of the nervous system ...
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 small
foramen In anatomy and osteology, a foramen (; : foramina, or foramens ; ) is an opening or enclosed gap within the dense connective tissue (bones and deep fasciae) of extant and extinct amniote animals, typically to allow passage of nerves, artery, ...
in the
greater wing The greater wing of the sphenoid bone, or alisphenoid, is a bony process of the sphenoid bone, positioned in the skull behind each eye. There is one on each side, extending from the side of the body of the sphenoid and curving upward, laterally, ...
of 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 bon ...
of the
skull The skull, or cranium, is typically a bony enclosure around the brain of a vertebrate. In some fish, and amphibians, the skull is of cartilage. The skull is at the head end of the vertebrate. In the human, the skull comprises two prominent ...
. It connects the
middle cranial fossa The middle cranial fossa is formed by the sphenoid bones, and the temporal bones. It lodges the temporal lobes, and the pituitary gland. It is deeper than the anterior cranial fossa, is narrow medially and widens laterally to the sides of the skull ...
(superiorly), and
infratemporal fossa The infratemporal fossa is an irregularly shaped cavity that is a part of the skull. It is situated below and medial to the zygomatic arch. It is not fully enclosed by bone in all directions. It contains superficial muscles, including the lower ...
(inferiorly).


Contents

The foramen transmits the
middle meningeal artery The middle meningeal artery (') is typically the third branch of the maxillary artery#First portion, first portion of the maxillary artery. After branching off the maxillary artery in the infratemporal fossa, it runs through the foramen spinosum t ...
and vein, and sometimes the
meningeal branch of the mandibular nerve The meningeal branch of the mandibular nerve (also known as the nervus spinosus) is a sensory branch of the mandibular nerve (CN V3) that enters the middle cranial fossa through either the foramen spinosum or foramen ovale to innervate the menin ...
(it may pass through the foramen ovale instead).


Relations

The foramen is situated just anterior to the
sphenopetrosal suture The sphenopetrosal fissure (or sphenopetrosal suture) is the cranial suture between the sphenoid bone and the petrous portion of the temporal bone. It is in the middle cranial fossa The middle cranial fossa is formed by the sphenoid bones, and t ...
. It is located posterolateral to the foramen ovale, and anterior to the sphenoidal spine. A groove for the
middle meningeal artery The middle meningeal artery (') is typically the third branch of the maxillary artery#First portion, first portion of the maxillary artery. After branching off the maxillary artery in the infratemporal fossa, it runs through the foramen spinosum t ...
and vein extends anterolaterally from the foramen.


Variation

The foramen spinosum varies in size and location. The foramen is rarely absent, usually unilaterally, in which case the
middle meningeal artery The middle meningeal artery (') is typically the third branch of the maxillary artery#First portion, first portion of the maxillary artery. After branching off the maxillary artery in the infratemporal fossa, it runs through the foramen spinosum t ...
enters the
cranial cavity The cranial cavity, also known as intracranial space, is the space within the skull that accommodates the brain. The skull is also known as the cranium. The cranial cavity is formed by eight cranial bones known as the neurocranium that in human ...
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 variesfrom 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 th ...
, derived from the first
pharyngeal arch The pharyngeal arches, also known as visceral arches'','' are transient structures seen in the Animal embryonic development, embryonic development of humans and other vertebrates, that are recognisable precursors for many structures. In fish, t ...
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 ...
, the foramen spinosum is found not in the sphenoid, but in parts of the
temporal bone The temporal bone is a paired bone situated at the sides and base of the skull, lateral to the temporal lobe of the cerebral cortex. The temporal bones are overlaid by the sides of the head known as the temples where four of the cranial bone ...
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. Additional images File:Sphenosquamosal suture - animation4.gif, Animation of sphenosquamosal suture File:Sphenosquamosal suture - ...
, or absent.


Function

The foramen spinosum permits the passage of the
middle meningeal artery The middle meningeal artery (') is typically the third branch of the maxillary artery#First portion, first portion of the maxillary artery. After branching off the maxillary artery in the infratemporal fossa, it runs through the foramen spinosum t ...
,
middle meningeal vein The pterygoid plexus (;Entry "pterygoid"
in
, and the
meningeal branch of the mandibular nerve The meningeal branch of the mandibular nerve (also known as the nervus spinosus) is a sensory branch of the mandibular nerve (CN V3) that enters the middle cranial fossa through either the foramen spinosum or foramen ovale to innervate the menin ...
.


Clinical significance

Due to its distinctive position, the foramen is used as an
anatomical landmark Anatomical terminology is a specialized system of terms used by anatomists, zoologists, and health professionals, such as doctors, surgeons, and pharmacists, to describe the structures and functions of the body. This terminology incorpor ...
during
neurosurgery Neurosurgery or neurological surgery, known in common parlance as brain surgery, is the specialty (medicine), medical specialty that focuses on the surgical treatment or rehabilitation of disorders which affect any portion of the nervous system ...
. 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 nerves, cranial nerve (CN V). Unlike the other divisions of the trigeminal nerve (ophthalmic nerve, maxillary nerve) which ...
and
trigeminal ganglion The trigeminal ganglion (also known as: Gasserian ganglion, semilunar ganglion, or Gasser's ganglion) is the sensory ganglion of each trigeminal nerve (CN V). The trigeminal ganglion is located within the trigeminal cave (Meckel's cave), a cav ...
, foramen ovale, and
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 ...
. It may also be relevant in achieving
haemostasis In biology, hemostasis or haemostasis is a process to prevent and stop bleeding, meaning to keep blood within a damaged blood vessel (the opposite of hemostasis is hemorrhage). It is the first stage of wound healing. Hemostasis involves three maj ...
during surgery, such as for ligation of the
middle meningeal artery The middle meningeal artery (') is typically the third branch of the maxillary artery#First portion, first portion of the maxillary artery. After branching off the maxillary artery in the infratemporal fossa, it runs through the foramen spinosum t ...
. This may be useful in
trauma surgery Trauma surgery is a surgical specialty that utilizes both operative and non-operative management to treat traumatic injuries, typically in an acute setting. Trauma surgeons generally complete residency training in general surgery and often f ...
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, urethr ...
into the
neurocranium In human anatomy, the neurocranium, also known as the braincase, brainpan, brain-pan, or brainbox, 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 cal ...
, or for removal of the pyramidal process of the
palatine bone In anatomy, the palatine bones (; derived from the Latin ''palatum'') are two irregular bones of the facial skeleton in many animal species, located above the uvula in the throat. Together with the maxilla, they comprise the hard palate. Stru ...
.


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" (). The correct, but unused name would, in fact, be '.


See also

*
Foramina of skull This article lists foramina that occur in the human body. __TOC__ Skull The human skull has numerous openings (foramina), through which cranial nerves, arteries, veins, and other structures pass. These foramina vary in size and number, with ...


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