Learning Objective: Describe the anatomy of the frontal bone, including its parts, articulations, attachments, and clinical significance, such as frontal sinusitis and fractures.
The frontal bone is a single, unpaired bone that forms the anterosuperior aspect of the cranium. Its name derives from Latin ‘frons’, meaning forehead. It protects the frontal lobes of the brain, forms the roof of the orbit, and contributes to the anterior cranial fossa.
Anatomical Structure
The frontal bone consists of four parts: squamous, orbital (2), and nasal.
Squamous Part
- The largest part, the external convex surface, forms the forehead.
- Internal features:
- Sagittal sulcus: vertical groove for the superior sagittal sinus.
- Frontal crest: attachment for the falx cerebri.
- Groove for the anterior meningeal artery.
- Houses the frontal sinuses (divided by a septum, with anterior and posterior plates).
- The supraorbital margin contains the supraorbital foramen (for the supraorbital nerve and vessels).
Orbital Parts
- Two flat, triangular plates form the roof of the orbit.
- Anterolateral: lacrimal fossa (lacrimal gland).
- Anteromedial: trochlear fossa (attachment for the superior oblique muscle pulley).
Nasal Part
- Small area projecting inferiorly between the supraorbital margins.
- Articulates with the nasal bones and the frontal processes of the maxilla.
- The nasal spine supports the bridge of the nose.
Attachments
- Trochlear fossa: cartilaginous pulley (‘trochlea’) for the superior oblique muscle.
- Frontal crest: attachment of the falx cerebri.
Articulations
The frontal bone articulates with 12 bones:
- Unpaired: Ethmoid, Sphenoid
- Paired: Nasal, Maxilla, Lacrimal, Parietal, Zygomatic
Clinical Relevance
Frontal Sinusitis
- Inflammation of the frontal sinus, usually infectious.
- Untreated infection can spread to the orbit or cranial cavity → orbital cellulitis, epidural/subdural abscess, meningitis.
Frontal Sinus Fracture
- Commonly due to motor vehicle accidents or falls.
- Anterior table fracture: frontal depression of the skull.
- Posterior table fracture: may cause cerebrospinal fluid (CSF) leakage through the nose → indicates dural rupture.
