Middle meningeal artery

The middle meningeal artery is a major branch of the maxillary artery, which itself arises from the external carotid artery. It supplies blood to the meninges, which are the protective layers covering the brain and spinal cord, as well as parts of the cranial bones.

Location

The middle meningeal artery arises in the infratemporal fossa from the maxillary artery. It ascends vertically and passes through the foramen spinosum of the sphenoid bone to enter the middle cranial fossa. Once inside the cranial cavity, the artery runs laterally between the dura mater and the inner surface of the skull, supplying the dura and bones of the cranial vault. It divides into anterior and posterior branches, spreading over the lateral aspects of the skull.

Origin

The middle meningeal artery is a major branch of the maxillary artery, one of the terminal branches of the external carotid artery. It originates from the first (mandibular) part of the maxillary artery in the infratemporal fossa, a deep anatomical space located beneath the base of the skull. The middle meningeal artery is one of the most important branches of the maxillary artery, supplying vital areas of the cranial cavity.

Course and Pathway

Infratemporal Fossa

The middle meningeal artery begins its course in the infratemporal fossa, where it arises from the maxillary artery near the mandibular neck. This space also contains the mandibular nerve (V3), pterygoid muscles, and other branches of the maxillary artery.

Foramen Spinosum

From the infratemporal fossa, the artery ascends vertically and passes through the foramen spinosum, a small circular opening located in the greater wing of the sphenoid bone. The foramen spinosum is an important bony landmark, allowing the artery to enter the cranial cavity. Alongside the artery, the meningeal branch of the mandibular nerve also enters the cranial cavity through the foramen spinosum.

Middle Cranial Fossa

Upon entering the middle cranial fossa, the middle meningeal artery runs laterally between the dura mater (the tough outer covering of the brain) and the inner surface of the cranial bones. It travels deep to the pterion, an anatomical region where the frontal, parietal, temporal, and sphenoid bones meet, making this a vulnerable point for head injuries.

Branching

Once inside the cranial cavity, the middle meningeal artery divides into two major branches: the anterior (frontal) branch and the posterior (parietal) branch.

Anterior (Frontal) Branch

The anterior branch travels forward and upward, coursing under the pterion and along the greater wing of the sphenoid and the parietal bone. It ascends toward the vertex of the skull, supplying the dura mater and cranial bones in the anterior and middle portions of the cranial vault.

Posterior (Parietal) Branch

The posterior branch runs posteriorly and slightly upward, following the curve of the parietal bone. This branch supplies the dura mater and bones of the posterior cranial vault, including parts of the occipital region and the temporal bone.

Small Branches and Anastomoses

In addition to its main anterior and posterior branches, the middle meningeal artery gives off several smaller branches:

• Petrosal branch: This small branch runs along the petrous portion of the temporal bone, supplying parts of the middle ear structures.
• Superior tympanic artery: A branch of the middle meningeal artery, this artery travels through the petrotympanic fissure to supply the tensor tympani muscle and parts of the middle ear.
• Orbital branches: Small branches may extend toward the orbit and supply parts of the periosteum and orbital structures.

The middle meningeal artery also forms important anastomoses with other arteries, including:

• Lacrimal artery (a branch of the ophthalmic artery)
• Stylomastoid artery (a branch of the posterior auricular artery)
• Accessory meningeal artery, which may arise from the maxillary artery and also enter the skull through the foramen ovale.

Relations with Surrounding Structures

The middle meningeal artery is in close proximity to several critical structures as it courses through the infratemporal fossa and cranial cavity:

• Pterion: The artery runs deep to the pterion, a clinically important region where the bones of the skull are thinner and more susceptible to fractures. The artery’s proximity to this area makes it vulnerable to injury in cases of head trauma.
• Dura mater: The artery travels between the dura mater and the inner surface of the skull, providing vascular support to these areas.
• Mandibular nerve (V3): The artery passes near the mandibular nerve as it exits the foramen spinosum, contributing to the vascular network that supports the dura and cranial bones.

Variations

There can be variations in the anatomy of the middle meningeal artery. For example, in some cases, the artery may arise directly from the internal carotid artery rather than the maxillary artery. Other variations include differences in the size and course of the anterior and posterior branches, as well as additional anastomoses with other meningeal or cranial arteries. Rarely, the artery may have an accessory branch known as the accessory meningeal artery, which may enter the cranial cavity via the foramen ovale.

Function

The middle meningeal artery is the primary artery responsible for supplying blood to the dura mater and parts of the cranial bones. It also has secondary roles in nourishing nearby structures such as the middle ear and the orbit. Below is a detailed explanation of its functions.

Blood Supply to the Dura Mater

The dura mater is the tough, outermost layer of the meninges that protect the brain and spinal cord. The middle meningeal artery is the principal vessel supplying the dura mater in the middle cranial fossa and large portions of the anterior and posterior cranial fossa.

• Anterior Branch: The anterior (frontal) branch of the middle meningeal artery supplies the anterior and middle portions of the dura mater, particularly in the region of the frontal and parietal bones. This branch is crucial for maintaining the health of the dura covering the superior portions of the brain.
• Posterior Branch: The posterior (parietal) branch travels toward the posterior region of the skull, nourishing the dura covering the parietal and occipital bones. This posterior branch ensures that the dura mater remains functional and well-oxygenated over the cerebellum and brainstem areas.

The blood supplied by the middle meningeal artery allows the dura mater to perform its protective functions, including providing structural support to the brain and aiding in the production of cerebrospinal fluid (CSF).

Blood Supply to Cranial Bones

The middle meningeal artery also plays an essential role in supplying the cranial bones with oxygenated blood. This is vital for maintaining the strength and health of the bones, especially in areas that are particularly thin or vulnerable to injury.

• Cranial Vault: The anterior and posterior branches of the middle meningeal artery supply the bones of the cranial vault, including the frontal, parietal, temporal, and occipital bones. This vascular supply helps maintain the health and density of these bones.
• Bone Repair and Regeneration: The artery plays a critical role in the repair and regeneration of the cranial bones following fractures or injury. By delivering nutrients and oxygen, it supports the periosteum (the outer layer of bone) in maintaining bone strength and healing damaged areas.

Support for Neurovascular Health

Through its supply to the dura mater and nearby cranial structures, the middle meningeal artery contributes to the overall neurovascular health of the brain and skull. The artery ensures that blood flow is maintained to the meningeal layers, which help regulate intracranial pressure and protect the brain.

Neurovascular Integrity: The artery’s branches ensure a rich blood supply to the dural layers, supporting their function in protecting and stabilizing the brain inside the skull. This continuous supply of oxygen and nutrients is crucial for the proper functioning of the central nervous system.

Blood Supply to the Middle Ear

The middle meningeal artery contributes to the blood supply of the middle ear through its smaller branches. These include the superior tympanic artery, which travels through the petrotympanic fissure and supplies structures in the middle ear.

• Tensor Tympani Muscle: One of the key structures the artery supplies is the tensor tympani muscle, a small muscle that regulates the tension of the tympanic membrane. This muscle plays an important role in protecting the ear from loud sounds.
• Middle Ear Structures: The artery also provides small branches to the tympanic cavity, supporting the health and function of the structures involved in hearing, including the auditory ossicles.

Blood Supply to the Orbit

The middle meningeal artery may give off small branches that supply parts of the orbit, contributing to the blood supply of the periosteum and nearby structures.

Orbital Structures: Through its orbital branches, the artery can help supply blood to the periorbita, the lining around the orbit, and some of the soft tissues in the region. This is particularly important in maintaining the health of the bones surrounding the eye and supporting orbital stability.

Role in Collateral Circulation

The middle meningeal artery forms important anastomoses (connections) with other arteries, creating a collateral blood supply that ensures continuous blood flow to the dura mater, cranial bones, and adjacent structures even if one of the arteries is compromised.

• Anastomosis with Lacrimal Artery: The artery anastomoses with branches of the lacrimal artery (a branch of the ophthalmic artery), forming an additional source of blood for the orbit and cranial dura.
• Anastomosis with Accessory Meningeal Artery: The middle meningeal artery also forms connections with the accessory meningeal artery, which enters the cranial cavity through the foramen ovale. This ensures that blood can continue to flow to the middle and posterior cranial fossa, even if one arterial pathway is blocked or damaged.

Support for Healing and Tissue Repair

The middle meningeal artery plays an important role in tissue repair and healing in the event of injury to the dura mater, cranial bones, or surrounding areas.

• Fracture Healing: In cases of cranial fractures, particularly in the regions supplied by the middle meningeal artery, the blood delivered by the artery supports the healing and regeneration of bone tissue.
• Dura Mater Repair: The artery’s blood flow helps repair the dura mater following traumatic injury or surgery, ensuring that the protective layer of the brain remains functional.

Role in Intracranial Pressure Regulation

By supplying the dura mater, the middle meningeal artery indirectly supports the regulation of intracranial pressure. The dura mater is involved in the production and regulation of cerebrospinal fluid (CSF), which plays a major role in maintaining proper pressure within the cranial cavity.

CSF Production Support: By ensuring the dura mater is well-nourished, the middle meningeal artery helps support the regulation of CSF flow, which is critical in protecting the brain from excessive pressure and maintaining normal brain function.

Clinical Significance

The middle meningeal artery is of great clinical significance due to its location and role in supplying blood to the dura mater and cranial bones. It is particularly vulnerable to injury in cases of head trauma, especially at the pterion, where the bones of the skull are thin and the artery runs superficially. Damage to the middle meningeal artery can lead to an epidural hematoma, a life-threatening condition in which blood accumulates between the skull and the dura mater, increasing intracranial pressure and compressing the brain.

The artery is also important in neurosurgical procedures and cranial surgeries, where care must be taken to avoid injury to it. Its anastomoses with other arteries, such as the lacrimal artery and accessory meningeal artery, make it a key vessel for ensuring collateral circulation in the cranial cavity. Furthermore, its role in the vascularization of the middle ear and the tensor tympani muscle makes it relevant in otological surgeries.