Preoperative Visualization of the Greater Occipital Nerve with Magnetic Resonance Imaging in Candidates for Peripheral Nerve Decompression for Headaches
Mariam Saad, MD1, Isaac V Manzanera Esteve, PhD1, Adam Evans, MD2, Sara C Chaker, BS3, Tigran Kesayan, MD1, Krista Brooks-horrar, MD4, Patrick E Assi, MD5, Wesley P. Thayer, M.D., PhD3 and Salam Kassis, MD1, 1Vanderbilt University, Nashville, TN, 2Eastern Virginia Medical School, Norfolk, VA, 3Vanderbilt University Medical Center, Nashville, TN, 4VA Tennessee Valley health care, Nashville, TN, 5Vanderbilt University, Nasville, TN
Introduction. Migraine and chronic headaches constitute a significant global burden, ranking as the second leading cause of disability. They also contribute substantially to financial costs. Surgical extracranial nerve decompression has demonstrated efficacy in decreasing the severity and frequency of migraines and chronic headaches in specific patient populations. However, the identification of accurate imaging techniques or electrodiagnostic biomarkers to detect specific anatomical characteristics related to occipital nerve migraine and chronic headaches remains unexplored. Such tools would provide valuable guidance to surgeons in identifying patients who would derive the greatest benefit from nerve decompression surgery.
Materials & Methods. Patients diagnosed with severe migraine headaches or occipital neuralgia who were scheduled for migraine surgery were approached to undergo MRI imaging of their greater occipital nerves (GONs). The MRI imaging protocol consisted of three MR neurography sequences designed to target fat-suppressed fluid-sensitive areas and utilize T2-weighted signal intensity to enhance the visualization of nerve pathologies and assess their morphology. To visualize the GON track, 2-D image slices were utilized, with each slice carefully rotated in the direction of the nerve course to obtain the subsequent slice until the entire nerve was successfully tracked.
Results. Twelve patients had MRI imaging of their GONs prior to surgery. Ten patients were female, and the average age was 49. Five patients had structures coursing in close proximity to one of the GONs, suspected to be the occipital arteries and confirmed upon operative validation. Four patients had increased thickness of the GON, and four patients had associated areas of hyperintensity at specific trigger points along the nerve track on one side. Unusual splitting of one the GONs was seen in the images of three patients and later validated in the operative findings of two of them. One patient had a connection between the right LON and GON seen intraoperatively, this was described as splitting of the GON with one the branches having a downward trajectory on MRI.
Conclusion. MRI can potentially serve as a non-invasive biomarker to guide surgeons in selecting patients who would derive the greatest benefit from surgical nerve decompression. It can visualize and track the GON from the C2 through the semispinalis muscle, along the scalp up to the vertex. It has the ability to locate potential trigger points suspected in migraine headache and occipital neuralgia. Further comparative studies are needed to determine the diagnostic accuracy of MRI in identifying the patients with peripherally triggered headaches.
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