MRI of the Head Including Orbit: Clinical Indications and Recommendations
MRI of the head including orbit is recommended for multiple clinical scenarios including nontraumatic acute vision loss, suspected optic pathway tumors, papilledema, leukocoria, and suspected intraocular masses, where it provides superior soft tissue characterization compared to other imaging modalities. 1
Clinical Indications for MRI Head with Orbits
Vision Loss
- Nontraumatic acute vision loss without papilledema: MRI head and orbits with and without IV contrast is the first-line imaging modality 1
- Optic neuritis: Contrast-enhanced MRI of orbits and head, typically performed together 1
- Suspected optic pathway tumor: MRI head and orbits with and without IV contrast 1
- Papilledema or raised intracranial pressure: MRI head and orbits with and without IV contrast 1
- Post-chiasmal visual field defects: MRI brain with and without contrast (homonymous hemianopia or quadrantanopia) 1
Orbital/Ocular Pathology
- Leukocoria or suspected intraocular mass: MRI head and orbits with and without IV contrast 1
- Suspected retinoblastoma: MRI head and orbits with and without IV contrast to evaluate for intraocular mass, retrolaminar optic nerve infiltration, orbital invasion, and possible intracranial spread 1
- Benign intraorbital masses: MRI orbits with and without IV contrast, often with head imaging 1
- Diplopia or ophthalmoplegia: Contrast-enhanced MRI of head and orbits, particularly when related to primary orbital disease process, extraocular muscle abnormality, or cranial nerve pathology 1
Inflammatory Conditions
- Giant cell arteritis with visual symptoms: Combined orbital and cranial vessel wall MRI shows high sensitivity (83%) for ocular involvement 2
- Orbital inflammation or infection: MRI provides superior tissue characterization compared to CT 3
Advantages of MRI for Orbital Imaging
- Superior soft tissue contrast resolution 3, 4
- Direct multiplanar imaging capabilities 4
- No ionizing radiation exposure 4
- Better visualization of the optic nerve and intracranial structures 4
- Superior evaluation of neurological disorders affecting vision 4
- Better characterization of pathologic conditions with T2-weighted sequences 4
- Visualization of bone marrow abnormalities 4
When CT is Preferred Over MRI
- Orbital trauma: Non-contrast orbital CT is the gold standard (94.9% sensitivity) for evaluating fractures, foreign bodies, and muscle entrapment 5
- Foreign body assessment: CT superior for detecting metallic foreign bodies 5
- Acute trauma with suspected bony injury: CT provides better visualization of bony anatomy 5
- Suspected orbital or periorbital infection: CT with IV contrast is usually appropriate as initial imaging 1
- When MRI is contraindicated: Patients with pacemakers, certain implants, or severe claustrophobia 4
Protocol Considerations
- Standard protocol: MRI head and orbits with and without IV contrast 1
- Specific scenarios:
- Suspected retinoblastoma: Both head and orbit imaging should be performed together 1
- Ophthalmoplegia: Consider imaging during different gaze positions to identify muscular slip or pulley abnormalities 1
- Cranial nerve evaluation: Include small field-of-view high-resolution T2-weighted images of cranial nerves 1
Pitfalls to Avoid
- Relying solely on radiographs for orbital pathology, which is insufficient for proper evaluation 5
- Failing to include both head and orbit imaging when evaluating suspected retinoblastoma 1
- Not considering MRI for soft tissue characterization when CT findings are equivocal 4
- Overlooking the need for contrast in most orbital MRI examinations 1
MRI of the head including orbit has largely replaced older imaging techniques and is complementary to CT in many clinical scenarios, with each modality having specific strengths based on the suspected pathology and clinical presentation.