Facial skeleton CT

Maxillary fractures: Le Fort classification

The classification proposed in 1900 distinguishes three main types of fractures. On CT images, it is important to evaluate specific anatomical landmarks of the injuries.

• Le Fort I fracture (Low level). The fracture line runs horizontally: it begins just above the piriform aperture (piriform fossa), extends below the base of the zygomatic bone, and heads toward the pterygoid process of the sphenoid bone (pterygoid plate). As a result, the tooth-bearing part of the maxilla (maxilla) is detached. It is frequently bilateral and clinically may lead to the formation of an open bite.
• Le Fort II fracture (Intermediate level). Pyramidal fracture. The line runs along the bridge of the nose, through the lacrimal bones, crosses the medial walls and inferior orbital margins, involving the anterior and posterolateral walls of the maxillary sinuses. Damage to the nasal septum at a variable level and the appearance of a step-like deformity are characteristic.
• Le Fort III fracture (Suprazygomatic fracture). There is a complete separation of the midface from the cranial base (craniofacial dysjunction). The fracture line extends posterolaterally through the medial and lateral orbital walls and crosses the zygomatic arches (zygomatic arches). In combined injuries (Le Fort II + III), CT often reveals hemosinus (fluid level) or total opacification of the maxillary sinus.

Features of facial fractures in clinical practice

Modern diagnostic imaging data demonstrate that a strict Le Fort classification is highly debatable — in actual practice, injuries are more complex.

1. Asymmetry. Injuries are rarely symmetrical. A classic example is the combination of bilateral Le Fort II and unilateral Le Fort III, where one side of the face is significantly more traumatized.
2. Comminution. Impact from sharp objects often causes comminuted (comminuted) fractures of the maxilla.
3. Associated injuries. Facial fractures are frequently accompanied by depressed fractures (depressed fracture) of the fronto-ethmoidal complex.
4. Tooth preservation. Even with extremely severe and massive fractures, the tooth-bearing alveolar process may remain intact.

CT diagnosis of temporal bone injuries

High-resolution CT (HRCT / HRCT) is the routine protocol in head trauma. Although temporal bone pyramid fractures are uncommon, it is important not to miss them, as they threaten cerebrospinal fluid leakage (CSF rhinorrhea/otorrhea), facial nerve palsy, or disruption of the ossicular chain.

Traditionally, pyramid fractures are divided into two groups:

• Longitudinal (80%). Occur with temporoparietal trauma. Frequently extend to the external acoustic meatus and the middle ear cleft.
• Transverse (20%). The consequence of occipital or frontal trauma. The fracture line begins at the sites of least resistance in the bone, such as the jugular foramen or vestibular aqueduct.

Important rule: the modern approach to CT reporting requires not so much classifying the fracture as longitudinal or transverse (they frequently have an oblique direction), but rather precisely describing the course of the fracture line and the involved anatomical structures.

Temporal bone pathologies on CT

Computed tomography is indispensable not only for trauma but also for evaluating the inner ear structures and neoplastic processes.

• Developmental anomalies. Normally, CT of the temporal bone pyramid should visualize a clear separation of the distal basal turn and the middle turns of the cochlea (cochlea), as well as the vestibule. Incomplete separation of the turns is a sign of pathology.
• Facial nerve palsy. Acute palsy is more commonly associated with Bell's palsy or trauma. CT is ordered less frequently than MRI; however, it is strictly indicated if the physician suspects cholesteatoma or otomastoiditis upon otoscopy.
• Glomus tumors (paragangliomas). The most frequent cause of pulsatile tinnitus. HRCT of extensive tympanic and jugulotympanic paragangliomas reveals a specific pattern of "permeative" (permeative) destruction of the adjacent bone tissue.

Class and exam questions

What else to study on this topic

• MRI findings of facial nerve lesions and topographic diagnosis of hearing loss.
• Imaging signs of glomus tumors on MRI (the "salt and pepper" sign).
• Diagnosis of vestibular schwannoma of the cerebellopontine angle.
• Ultrasound and X-ray (sialography) diagnostics of sialolithiasis.
• Anatomy and physiology of the inner ear: how hair cells encode sound frequencies.

Other topics in the Neuroimaging section

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