From the Guidelines
To diagnose optic neuritis, an MRI of the head and orbits with and without IV contrast is the most useful imaging modality. This recommendation is based on the most recent and highest quality study available, which suggests that MRI of the head and orbits with and without IV contrast can identify abnormal enhancement of the optic nerve in 95% of cases of optic neuritis 1. The MRI should specifically include fat-suppressed T1-weighted sequences with gadolinium contrast, which helps highlight areas of inflammation by showing contrast enhancement of the affected optic nerve.
Key Considerations
- The use of MRI allows for the evaluation of the lesions involving extraorbital neurovisual pathway and the remainder of the brain parenchyma, which is important in identifying underlying conditions such as multiple sclerosis 1.
- T2-weighted and FLAIR sequences are also important to identify white matter lesions that might suggest multiple sclerosis, as optic neuritis is frequently associated with this condition.
- While other imaging modalities such as orbital ultrasound may be used as supplementary tests, they have limited sensitivity compared to MRI.
- Visual evoked potentials (VEPs) can also be helpful as a complementary test to assess optic nerve function, though they are not imaging studies.
Clinical Application
The MRI findings, combined with clinical symptoms such as vision loss, eye pain, and color vision deficits, provide the most comprehensive approach to diagnosing optic neuritis and identifying any underlying conditions. The most recent study available supports the use of MRI as the primary imaging modality for the evaluation of acute nontraumatic vision loss, including optic neuritis 1.
From the Research
Imaging Studies for Optic Neuritis
To diagnose optic neuritis, the following imaging studies can be obtained:
- Gadolinium-enhanced MRI of the brain and orbits, as recommended by studies 2, 3
- Fat-suppressed MRI to reduce chemical shift artifact of orbital fat and improve detection of optic nerve enhancement, as suggested by studies 4, 5
- 3.0 Tesla MRI, which has been shown to be more sensitive than 1.5 Tesla MRI in detecting optic neuritis, according to study 6
Key Findings
- The presence of two or more white matter lesions on MRI suggests high risk for clinically definite multiple sclerosis (CDMS) 2, 3
- Gadolinium-enhanced MRI can help identify optic nerve enhancement and demyelination 4, 5
- Combined fat- and water-suppression techniques, such as SPIR-FLAIR, can improve the demonstration of optic neuritis and optic nerve atrophy 5
Imaging Modalities
- MRI is the preferred imaging modality for diagnosing optic neuritis, with gadolinium enhancement and fat suppression techniques providing additional diagnostic value 2, 3, 6, 4, 5
- 3.0 Tesla MRI is more sensitive than 1.5 Tesla MRI in detecting optic neuritis, but the choice of magnet strength may depend on availability and clinical judgment 6