[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Anatomy](https://durgical.com/en/anatomy/) › [Head and neck](https://durgical.com/en/anatomy/region/head-and-neck/) › Pterion [Skeletal system](https://durgical.com/en/anatomy/system/skeletal-system/) · [Head and neck](https://durgical.com/en/anatomy/region/head-and-neck/) # Pterion The pterion is the thin H-shaped spot on the side of the skull where four bones meet; an artery runs just inside, so a blow here can bleed over the brain. [See in 3D →](https://durgical.app/?from=durgipedia&lang=en#region=head_neck&select=pterion&side=r) Opens in the Durgical app, no sign-up needed. ## What it is The H-shaped thin spot on the side of the skull where four bones meet. ## What it does The middle meningeal artery runs just inside; a blow here can cause an epidural haematoma. ## Key points - A fracture line on CT crossing the groove of the middle meningeal artery here is a warning sign for an epidural haematoma, even when the person looks well (lucid interval) - Inside the skull it overlies the stem of the lateral (sylvian) fissure and the lesser wing of the sphenoid; on the dominant side Broca area lies close by - The pterional (frontotemporal) craniotomy is centred here: a standard route to the sylvian fissure, aneurysms of the [circle of Willis](https://durgical.com/en/anatomy/cerebral-arterial-circle/) and the region around the sella - In children the thin, pliable skull can let an epidural haematoma form without a visible fracture ## Key facts **Where** H-shaped junction of the frontal, parietal, temporal squama and greater wing of the sphenoid, about 3 cm above the zygomatic arch **Function** Thinnest part of the skull side; the frontal branch of the middle meningeal artery runs beneath (epidural haematoma) ## Relations **Deep** Dura with the frontal branch of the [middle meningeal artery](https://durgical.com/en/anatomy/middle-meningeal-artery/); then the lateral fissure, with the [middle cerebral artery](https://durgical.com/en/anatomy/middle-cerebral-artery/) in its depth, and the inferior frontal gyrus **Superficial** [Temporalis](https://durgical.com/en/anatomy/temporalis-muscle/) and its fascia, the superficial temporal vessels and the frontal (temporal) branch of the [facial nerve](https://durgical.com/en/anatomy/facial-nerve/) crossing the temple **In front** Frontal process of the [zygomatic bone](https://durgical.com/en/anatomy/zygomatic-bone/) and the lateral orbital rim **Below** Zygomatic arch and, below the infratemporal crest, the infratemporal fossa ## How to find it It cannot be felt as a point, because temporalis covers it. It lies in the hollow of the temple where a line going up from the middle of the zygomatic arch meets a line going back from the frontozygomatic suture. ## On imaging Skull CT with bone windows and 3D reconstruction shows the H-shaped suture junction and fractures crossing the arterial groove; the same scan in brain windows shows an epidural haematoma beneath as a bright, [lens](https://durgical.com/en/anatomy/lens/) -shaped collection. ## Clinical notes - An epidural haematoma from the frontal branch can enlarge over hours; drowsiness, a dilated pupil on the same side and weakness of the other side mean brain shift and call for emergency surgical evacuation - The frontal (temporal) branch of the facial nerve crosses superficially; injury in approaches here leaves the eyebrow unable to rise on that side - Small sutural bones at the pterion (epipteric bones) can be mistaken for a fracture on radiographs ## Anatomical variants - Suture pattern: in most skulls the sphenoid meets the parietal (sphenoparietal type); less often the frontal meets the temporal, or all four meet at one point (stellate type) - The frontal branch of the middle meningeal artery may run in a bony tunnel rather than a groove at the pterion, which makes it easier to tear in a fracture ## Development It marks the site of the anterolateral (sphenoidal) fontanelle of the newborn, which closes in the first year. ## Related conditions - [Epidural haematoma](https://durgical.com/en/conditions/epidural-haematoma/) ## Test yourself Think of the answer, then tap the question to see it. ## Which bones meet at the pterion, and why is it clinically important? Frontal, parietal, temporal squama and greater wing of the sphenoid; it is the thinnest part of the skull side, over the frontal branch of the middle meningeal artery. ## What does a CT fracture line crossing the middle meningeal groove at the pterion warn of? An epidural haematoma, even when the person looks well during a lucid interval. ## Which signs show that an epidural haematoma under the pterion is causing brain shift? Drowsiness, a dilated pupil on the same side and weakness of the other side; they call for emergency surgical evacuation. ## Which nerve branch is at risk in surgical approaches at the pterion, and what is the deficit? The frontal (temporal) branch of the facial nerve; the eyebrow cannot rise on that side. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/anatomy/pterion/) Educational information, not medical advice. For any symptom, see a health professional. ## Its names **Official Latin (TA2)** pterion TA2 421 **Official Spanish (DeCS)** Pterion **English (TA2)** Pterion ## Related - [Middle meningeal artery](https://durgical.com/en/anatomy/middle-meningeal-artery/) Sources: Terminologia Anatomica (TA2); [Anatomy, Head and Neck, Skull](https://www.ncbi.nlm.nih.gov/books/NBK499834/); [Anatomy, Head and Neck, Temporal Region](https://www.ncbi.nlm.nih.gov/books/NBK482497/). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/anatomy/pterion/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/pterion/