From the Guidelines
For a patient with suspected cluster headaches and changes in migraines with concern for optic nerve involvement, I would recommend a dedicated MRI protocol including T1-weighted and T2-weighted sequences with fat suppression, STIR (Short Tau Inversion Recovery) imaging, and contrast-enhanced T1-weighted sequences with thin cuts through the orbits and optic nerves, as this approach is supported by the most recent and highest quality study 1.
When evaluating the optic nerve, it is essential to include sequences that can detect inflammation, demyelination, compression, or vascular abnormalities. The recommended MRI protocol should include:
- T1-weighted and T2-weighted sequences with fat suppression to visualize the optic nerve structure
- STIR (Short Tau Inversion Recovery) imaging to detect subtle changes in the optic nerve
- Contrast-enhanced T1-weighted sequences with thin cuts through the orbits and optic nerves to reveal inflammation or lesions affecting the optic nerve
- MR angiography (MRA) of the head and neck to evaluate vascular structures, particularly the cavernous sinus and internal carotid arteries
- Diffusion-weighted imaging (DWI) to identify any acute ischemic changes
- FLAIR (Fluid-Attenuated Inversion Recovery) sequences to detect subtle white matter abnormalities
The use of contrast enhancement is crucial, as it can identify abnormal enhancement of the optic nerve in 95% of cases of optic neuritis, as reported in a study published in the Journal of the American College of Radiology 1. Additionally, a study on the assessment of lesions on magnetic resonance imaging in multiple sclerosis provides guidance on the optimal sequences for evaluating the optic nerve, including coronal fat-suppressed T2-weighted sequences with submillimetre in-plane resolution and slice thickness of 4-3 mm 1.
By following this comprehensive MRI protocol, clinicians can differentiate between primary headache disorders and secondary causes that might require different treatment approaches, ultimately improving patient outcomes in terms of morbidity, mortality, and quality of life.
From the Research
Special MRI Sequencing for Cluster Headaches and Migraines
To evaluate the optic nerve in a patient with suspected cluster headaches and a change in migraines, the following special MRI sequencing is recommended:
- High-resolution MRI of the optic nerve with T1 and T2 weighted images, as well as magnetization transfer ratio and apparent diffusion coefficient measurements, if possible 2
- Contrast-enhanced MRI including the sella turcica to rule out pituitary adenomas or other tumors that may be causing the headaches 3, 4
- MRI of the brain with SE T1, FSE T2, PD, FLAIR, and IR T1 sequences to detect any brain pathology, such as demyelination or vascular malformations 5
- MRV (Magnetic Resonance Venography) to evaluate the cranial venous outflow and detect any signs of obstruction or abnormalities in the venous sinuses 6
Evaluation of the Optic Nerve
When evaluating the optic nerve, the following MRI findings should be looked for:
- Elongation and edema of the optic nerves 6
- Protrusion of the optic disc 6
- Flattening of the posterior sclera 6
- Width of the optic nerve sheath 6
- Cranial venous outflow obstruction and ONS hydrops, which are highly sensitive and specific signs of intracranial hypertension 6
Importance of Neuroimaging
Neuroimaging, including MRI and MRV, is essential in patients with cluster headaches and migraines, especially those with atypical presentations or evolutions, to rule out secondary causes of headaches, such as tumors or vascular malformations 3, 4, 5, 6