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The pterion is an H-shaped suture complex on the side of the skull, just behind the temple, where the frontal, parietal, temporal, and sphenoid bones meet. It is considered the weakest part of the skull, making it clinically significant. The pterion is also a neurosurgical landmark for approaching middle cerebral artery aneurysms. The muscles covering the pterion include the temporalis, masseter, and sternocleidomastoid muscles, which attach to the temporal bone.
| Characteristics | Values |
|---|---|
| Location | Side of the skull, just behind the temple |
| Composition | H-shaped formation of sutures |
| Bones | Temporal, parietal, frontal, and sphenoid |
| Artery | Anterior division of the middle meningeal artery |
| Clinical Significance | Weakest part of the skull, susceptible to fracture |
| Muscles | Temporalis, masseter, sternocleidomastoid |
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What You'll Learn
The pterion is the weakest part of the skull
The pterion is located on the side of the skull, just behind the temple, and is a craniometric point used in skull measurements and neurosurgery. Its position is approximately 2.6 cm behind and 1.3 cm above the posterolateral margin of the frontozygomatic suture. This area is also referred to as the anterior end of the squamous suture, with the asterion located at the posterior end. The pterion is an important landmark for neurosurgeons when performing craniotomies, especially the pterional craniotomy, as it provides wide exposure to the middle cranial fossa and other structures while minimising brain retraction.
The pterion's weakness is due to it being the point of union between several bones. A traumatic blow to this region can result in a skull fracture and rupture of the underlying middle meningeal artery. This can lead to an extradural or epidural haematoma, where blood collects between the dura mater and the skull, causing a dangerous increase in intracranial pressure. Symptoms of this include nausea, vomiting, seizures, bradycardia, and limb weakness. Treatment options range from diuretics for minor cases to surgical intervention in cases of major haemorrhage.
The pterion's H-shape is formed by the sutures between the frontal, parietal, temporal, and sphenoid bones. The parietal and sphenoid bones constitute the midpoint of the H. The anterior limb of the H comprises sutures between the frontal, parietal, and sphenoid bones, while the posterior limb is composed of sutures between the parietal, temporal, and sphenoid bones. This complex suture arrangement contributes to the pterion's structural weakness, making it the most fragile part of the skull.
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It is where the frontal, parietal, temporal and sphenoid bones meet
The pterion is an H-shaped formation of sutures on the side of the skull, just behind the temple. It is the region where the frontal, parietal, temporal, and sphenoid bones meet. It is also the thinnest part of the skull, making it clinically significant. Due to its location over the anterior division of the middle meningeal artery, fractures in this area can cause serious issues.
The frontal bone is located at the front of the skull, forming the forehead. It articulates with the parietal bone, which forms the sides and roof of the skull. The parietal bone also connects with the temporal bone, which is located at the sides of the skull and forms part of the temporomandibular joint (TMJ) of the jaw. The temporal bone serves as a point of attachment for many muscles, including the temporalis and masseter muscles.
The sphenoid bone is located at the base of the skull and articulates with both the frontal and parietal bones. It has a complex shape and contains a number of important structures, including the sphenoidal sinus and optic canal. The sphenoid bone also articulates with the temporal bone, forming the zygomatic arch, which is palpable as the cheekbones.
The pterion is an important landmark in neurosurgery, particularly for the pterional craniotomy approach. This approach provides wide exposure to the middle and anterior cranial fossae, as well as other important structures, while minimising brain retraction. Due to its location and structural weakness, the pterion is also important in the context of head trauma. A traumatic blow to the pterion may rupture the underlying middle meningeal artery, leading to an epidural haematoma and a dangerous increase in intracranial pressure.
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The middle meningeal artery runs underneath the pterion
The pterion is an H-shaped suture complex, representing the junction of four skull bones: the frontal, parietal, temporal, and sphenoid bones. It is located on the side of the skull, just behind the temple, and is considered the weakest part of the skull. This makes it clinically significant, as fractures in this region can lead to serious complications.
Underneath the pterion runs the anterior division of the middle meningeal artery (MMA). The MMA supplies the skull and the dura mater, which is the outer membranous layer covering the brain. Due to its location, a traumatic blow or fracture to the pterion can rupture or injure the MMA. This can result in an epidural or extradural haematoma, where blood collects between the dura mater and the skull, leading to a dangerous increase in intracranial pressure.
Symptoms of an extradural haematoma include nausea, vomiting, seizures, bradycardia, and limb weakness. Treatment options depend on the severity of the haemorrhage, ranging from diuretics for minor cases to surgical intervention for major haemorrhages. The pterion, therefore, plays a crucial role in the management of head injuries and neurosurgical procedures.
Neurosurgical approaches, such as the pterional craniotomy, commonly utilise the pterion as a landmark for accessing various structures within the skull. By understanding the anatomy of the pterion and its relationship with the MMA, neurosurgeons can effectively treat conditions like middle cerebral artery aneurysms while minimising brain retraction and potential complications.
In summary, the middle meningeal artery runs underneath the pterion, making this region of the skull clinically significant. Fractures or traumatic blows to the pterion can result in serious complications, including MMA rupture and extradural haematoma. This knowledge is essential for both the management of head injuries and neurosurgical procedures, highlighting the importance of understanding the anatomy of the pterion and its underlying structures.
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A fracture to the pterion can cause an extradural haematoma
The pterion is the region where the frontal, parietal, temporal, and sphenoid bones join. It is located on the side of the skull, just behind the temple, and is considered the weakest part of the skull. The anterior division of the middle meningeal artery (MMA) runs underneath the pterion. A fracture to the pterion can cause an extradural haematoma, also known as an epidural haematoma, a type of intracranial haemorrhage.
Extradural haematomas are extra-axial bleeds occurring between the dura mater and the skull bone. They are commonly caused by skull trauma in the temporoparietal region, resulting in a linear skull fracture with minimal displacement. Due to the pterion's location over the MMA, a fracture at this point can rupture the artery, leading to an extradural haematoma. This type of fracture is the most common source of bleeding, occurring in around 85% of cases.
The MMA supplies the skull and the dura mater, the outer membranous layer covering the brain. When the MMA is ruptured, blood collects between the dura mater and the skull, causing a dangerous increase in intracranial pressure. This increase in pressure results in a range of symptoms, including nausea, vomiting, seizures, bradycardia, and limb weakness. Without treatment, the rising intracranial pressure can lead to brainstem death.
Extradural haematomas are typically associated with a history of trauma, such as road traffic collisions, falls, or assaults. They are more common in young people, particularly males, and those engaging in high-risk behaviours or contact sports. While rare in children under two and adults over 60, they occur in up to 10% of people with head injuries and carry significant morbidity and mortality risks.
The diagnosis of an extradural haematoma is often more straightforward than other types of haemorrhage due to its sudden and obvious presentation. Initial investigations include urgent blood tests and CT imaging of the head, which typically reveals hyperdense biconvex lesions. Treatment options depend on the severity of the haematoma and range from diuretics for minor cases to surgical intervention for major haemorrhages.
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The pterion is an H-shaped suture complex
The H-shape of the pterion is formed by the sutures between these four bones. The anterior limb of the H-shape consists of sutures between the frontal, parietal, and sphenoid bones, while the posterior limb comprises sutures between the parietal, temporal, and sphenoid bones. The parietal and sphenoid bones form the midpoint of the H-shape. Notably, the midpoint of the H-shape is not at the same level on the skull's external and internal surfaces, with the external pterion lying above the internal pterion when viewed externally.
The pterion is of particular interest in neurosurgery due to its proximity to the middle meningeal artery, which runs underneath it. A fracture in this region can injure the artery, leading to an extradural haematoma, a dangerous increase in intracranial pressure. Symptoms of an extradural haematoma include nausea, vomiting, seizures, bradycardia, and limb weakness. Treatment options range from diuretics for minor cases to surgical intervention in cases of major haemorrhage.
The pterion also serves as an important landmark for neurosurgeons when performing craniotomies, particularly the pterional craniotomy, which is a common approach to accessing the middle cranial fossa and other structures. By understanding the anatomy of the pterion and its surrounding structures, surgeons can minimise brain retraction and optimise patient outcomes.
In summary, the pterion is an H-shaped suture complex that represents the junction of four skull bones and is of significant clinical importance due to its proximity to the middle meningeal artery and its role as a neurosurgical landmark. Its structural weakness and anatomical relationships underscore the need for a comprehensive understanding of this region in both diagnostic and surgical contexts.
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Frequently asked questions
The pterion is the region where the frontal, parietal, temporal, and sphenoid bones join. It is located on the side of the skull, just behind the temple.
The pterion is considered to be the weakest part of the skull. The anterior division of the middle meningeal artery runs underneath the pterion. Consequently, a traumatic blow to the pterion may rupture the middle meningeal artery, causing an epidural hematoma.
An epidural hematoma is when blood collects in between the dura mater and the skull, causing a dangerous increase in intracranial pressure. This can lead to symptoms such as nausea, vomiting, seizures, bradycardia, and limb weakness.
The temporal bone serves as a point of attachment for many muscles, including the temporalis and masseter muscles. The mastoid process of the temporal bone is a major site of muscle attachment, including for the sternocleidomastoid muscle.
The pterion is a structural landmark for the neurosurgical approach to middle cerebral artery aneurysms. The pterional craniotomy is a common neurosurgical procedure that provides wide frontobasal exposure while minimizing brain retraction.
