What are the radiographic features of a Naso-Orbito-Ethmoidal (NOE) fracture?

Radiographic Features of Naso-Orbito-Ethmoidal (NOE) Fractures

CT imaging with thin sections (1-2mm) is the gold standard for diagnosing NOE fractures, as it allows assessment of the medial canthal tendon's status and degree of comminution of the lacrimal crest bone to which it remains attached. 1

Primary Imaging Modality

Multidetector CT (MDCT) is the imaging modality of choice for evaluating NOE fractures due to:

• Superior delineation of osseous and soft tissue structures
• High image resolution with thin-section acquisitions
• Ability to detect subtle nondisplaced fractures
• Capability to assess the degree of comminution of the medial orbital wall at the level of the lacrimal fossa 1

Key CT Features of NOE Fractures

Bony Structures

• Comminution of the medial orbital wall at the lacrimal fossa level 1
• Fractures of the nasal bones, medial orbital walls, nasal septum, and naso-frontal junction 1
• Telescoping of the nasal bones 1
• Lateral displacement of medial orbital wall fragments into the orbit ("medial wall blow-in fractures") 2
• Medial displacement of ethmoid bone fragments ("medial wall blow-out fractures") 2
• Status of the "central fragment" (bone fragment bearing the medial canthal tendon insertion) 3

Soft Tissue Findings

• Displacement of the globe or extra-ocular muscles 2
• Potential entrapment of the medial rectus muscle 2
• Soft tissue swelling in the naso-orbital region 2

Associated Findings

• Frontal bone fractures (present in up to 70% of cases) 2
• Intracranial injuries (present in up to 70% of cases) 2
• Potential cerebrospinal fluid leak 1
• Associated facial fractures (orbital rim/floor, maxillary, mandibular) 4

Classification Based on Imaging

NOE fractures can be classified based on CT findings into three types according to the status of the medial canthal tendon and its bone insertion 3:

1. Type I: Single-segment central fragment
2. Type II: Comminuted central fragment with fractures remaining external to the medial canthal tendon insertion
3. Type III: Comminuted central fragment with fractures extending into bone bearing the canthal insertion

Advanced Imaging Considerations

3D Reconstructions

• Multiplanar and 3D image reconstructions allow better characterization of complex fractures
• Many surgeons find 3D reformations critical for preoperative planning 1

MRI Role

• Not typically used for initial evaluation
• May be helpful in cases with:
  • Cranial nerve deficits not explained by CT
  • Detection of CSF leak from skull base fracture
  • Evaluation of the olfactory nerve
  • Assessment of soft tissue herniation through skull base defects 1

Clinical Correlation

CT findings should be correlated with clinical findings, which may include:

• Traumatic telecanthus (widening of the intercanthal distance)
• Enophthalmos
• Nasal deformity
• Potential CSF rhinorrhea 5

Pitfalls and Caveats

• Head CT alone may miss or only partially image NOE fractures; dedicated maxillofacial CT is recommended 1
• Marked soft tissue swelling may preclude detailed physical examination, making CT even more valuable 2
• Associated injuries are common and should be actively sought on imaging (cervical spine injuries, intracranial injuries) 1
• Early and accurate diagnosis is critical to prevent long-term functional and cosmetic complications 5