Dominic Stone
The pterion is a region on the lateral aspect of the skull where four bones meet: the frontal, parietal, temporal, and sphenoid bones. It is a clinically significant area as it is the weakest part of the skull and is located directly above the middle meningeal artery. A fracture at the pterion can cause an extradural haematoma, a dangerous increase in intracranial pressure. Due to its structural importance, the pterion serves as a structural landmark for neurosurgical approaches. The muscles covering the pterion include the temporalis and masseter muscles, which are involved in the formation of the temporomandibular joint (TMJ) or jaw joint.
| Characteristics | Values |
|---|---|
| Location | Side of the skull, just behind the temple |
| Skull bones joined | Frontal, parietal, temporal, sphenoid |
| Skull weakness | Yes, weakest part of the skull |
| Clinical significance | Skull is very thin, fracture can cause an extradural (epidural) haematoma |
| Artery | Anterior division of the middle meningeal artery |
| Muscle attachments | Temporalis, masseter, sternocleidomastoid |
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What You'll Learn
The pterion is the weakest part of the skull
The pterion is a region on the lateral aspect of the skull where four bones meet: the frontal, parietal, temporal, and sphenoid bones. The name comes from the Ancient Greek root "pteron", meaning "wing". In Greek mythology, Hermes, the messenger of the gods, had wings attached to his head at the pterion, enabling him to fly.
The pterion is a clinically significant area of the skull. It is considered the weakest part of the skull due to the union of several bones, making it susceptible to fractures. A fracture at the pterion can disrupt the underlying middle meningeal artery, leading to an extradural or epidural haematoma. This type of injury can cause a dangerous increase in intracranial pressure, resulting in symptoms such as nausea, vomiting, seizures, bradycardia, and limb weakness.
The pterion is located in the temporal fossa, approximately 2.6 cm behind and 1.3 cm above the posterolateral margin of the frontozygomatic suture. It is positioned about two fingers' breadth above the zygomatic arch and a thumb's width behind the upward portion of the zygomatic bone. This area of the skull is also referred to as the temporal bone, which serves as a point of attachment for many muscles, including the temporalis and masseter muscles.
The pterion is an important landmark in neurosurgery, particularly when approaching middle cerebral artery aneurysms and performing pterional craniotomies to access the middle cranial fossa. Its location makes it crucial in radiological and anthropological skull measurements. Overall, the pterion's weakness is a critical factor in head trauma and brain injuries, which are major causes of death and disability.
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It is where four bones meet
The pterion is a region on the lateral aspect of the skull where four bones meet: the frontal, parietal, temporal, and sphenoid bones. It is located just behind the temple, approximately two fingers' breadth above the zygomatic arch (cheekbones) and a thumb's width behind the upward portion of the zygomatic bone. The name "pterion" comes from the Ancient Greek "pteron," meaning "wing." In Greek mythology, Hermes, the messenger of the gods, had wings on his head, attached at the pterion, that enabled him to fly.
The pterion is a significant anatomical landmark, particularly in neurosurgery, as it is located directly over the path of the anterior division of the middle meningeal artery (MMA). This artery supplies the skull and the dura mater, the outer membranous layer covering the brain. Due to the intersection of multiple bones, the skull is structurally weak at the pterion, making it the weakest part of the skull. As a result, a fracture in this region can injure or completely lacerate the MMA, leading to an extradural or epidural haematoma. Specifically, blood accumulates between the dura mater and the skull, causing a dangerous increase in intracranial pressure. This condition is characterised by symptoms such as nausea, vomiting, seizures, bradycardia, and limb weakness.
The pterion is also important in the context of head injuries and trauma. As mentioned earlier, the pterion is the weakest part of the skull, making it susceptible to fractures from blunt force or penetrating trauma. Strong blows to this region can result in fractures, leading to bleeding inside the skull and potential injury to the brain. Consequently, head injuries are a major cause of immediate death and disability, with additional complications like infections.
Furthermore, the temporal bone, which is part of the pterion, serves as a point of attachment for several muscles. These include muscles of mastication, such as the temporalis and masseter muscles, which attach to the temporal bone through their involvement in forming the temporomandibular joint (jaw joint). The mastoid process of the temporal bone is also a significant site of muscle attachment, including muscles such as the sternocleidomastoid.
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Fractures at the pterion can cause extradural haematomas
The pterion is a region on the lateral aspect of the skull where four bones—the frontal, parietal, temporal, and sphenoid—join together. It is located just behind the temple and is considered the weakest part of the skull. The skull is very thin at this point, and the anterior division of the middle meningeal artery runs underneath it. Due to its structural weakness and the presence of the artery, fractures at the pterion can cause extradural haematomas, also known as epidural haematomas.
Extradural haematomas are a type of intracranial haemorrhage that occurs outside of the brain, specifically between the dura mater and the skull bone. They are often caused by skull trauma, particularly in the temporoparietal region, and are associated with skull fractures in 73.5% to 75% of cases. The pterion is particularly vulnerable to fracture due to the thinness of the bone in this region. A fracture at the pterion can lacerate the middle meningeal artery, causing bleeding between the dura and the skull.
The middle meningeal artery is the most common source of bleeding in extradural haematomas, accounting for around 85% of cases. When this artery is ruptured, blood accumulates between the skull and the dura mater, forming an extradural haematoma. This type of haematoma can lead to a significant increase in intracranial pressure, which can cause damage to the brain and even brainstem death if left untreated.
The classic presentation of an extradural haematoma includes an initial loss of consciousness at the time of injury, followed by a lucid interval, and then progressively decreasing consciousness. Other symptoms may include severe headaches, nausea, confusion, and Cushing's triad, which includes bradycardia, hypertension, and irregular breathing. Diagnosis is typically made through CT imaging, which reveals hyperdense biconvex lesions indicative of an extradural haematoma. Treatment involves emergency surgery to drain the blood, remove the haematoma, stop the bleeding, and relieve the pressure on the brain.
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The pterion overlies the middle meningeal artery
The pterion is a region on the lateral aspect of the skull where four bones—the frontal, parietal, temporal, and sphenoid—are joined together. The name pterion comes from the Ancient Greek root "pteron", meaning "wing". In Greek mythology, Hermes, the messenger of the gods, had wings on his head that were attached at the pterion, enabling him to fly.
The pterion is considered the weakest part of the skull, making it clinically significant. Its location is approximately 2.6 cm behind and 1.3 cm above the posterolateral margin of the frontozygomatic suture. The skull is very thin at this point, and it is also a point of union between several bones, making it structurally weak. This means that a fracture of the skull at the pterion is a serious concern as it can lead to an extradural (epidural) haematoma.
Due to its proximity to the pterion, any fracture or traumatic blow to the pterion can result in the rupture of the MMA. This can lead to a dangerous increase in intracranial pressure, causing symptoms such as 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 serves as a structural landmark for the neurosurgical approach to middle cerebral artery aneurysms. Its clinical significance lies in its vulnerability to fractures and the potential consequences for the underlying MMA.
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It is located two finger widths above the zygomatic arch
The pterion is a region on the lateral aspect of the skull where four bones are joined: the frontal, parietal, temporal, and sphenoid bones. It is a clinically significant area, as it is the weakest part of the skull. The skull is very thin at this point, and a fracture of the skull at the pterion can disrupt the middle meningeal artery, leading to an extradural (epidural) haematoma.
The pterion is located two finger widths above the zygomatic arch, which is palpable as the cheekbones. The zygomatic arch is formed by the articulation of the zygomatic process of the temporal bone with the zygomatic bone. This process arises from the lower part of the squama temporalis, projecting anteriorly.
The pterion is also located a thumb's width posterior to the frontal process of the zygomatic bone. This position is clinically important, as it overlies the course of the anterior division of the middle meningeal artery. Consequently, a traumatic blow to the pterion may rupture the middle meningeal artery, causing an epidural haematoma.
The pterion is a structural landmark used in neurosurgery to approach middle cerebral artery aneurysms. It is also known as the weakest point of the skull, where a fracture can result in bleeding inside the skull and subsequent injury to the brain. Head and traumatic brain injuries are a major cause of immediate death and disability.
The temporal bone serves as a point of attachment for many muscles, including the temporalis and masseter muscles. These muscles attach to the temporal bone due to its involvement in forming the temporomandibular joint, or the joint of the jaw. The pterion, located two finger widths above the zygomatic arch, is a critical landmark in the temporal region of the skull.
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