Feasibility Study on MR-Guided High-Intensity Focused Ultrasound Ablation of Sciatic Nerve in a Swine Model: Preliminary Results
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Spastic patients often seek neurolysis, the permanent destruction of the sciatic nerve, for better pain management. MRI-guided high-intensity focused ultrasound (MRgHIFU) may serve as a noninvasive alternative to the prevailing, more intrusive techniques. This in vivo acute study is aimed at performing sciatic nerve neurolysis using a clinical MRgHIFU system.
The HIFU ablation of sciatic nerves was performed in swine (n = 5) using a HIFU system integrated with a 3 T MRI scanner. Acute lesions were confirmed using T1-weighted contrast-enhanced (CE) MRI and histopathology using hematoxylin and eosin staining. The animals were euthanized immediately following post-ablation imaging.
Reddening and mild thickening of the nerve and pallor of the adjacent muscle were seen in all animals. The HIFU-treated sections of the nerves displayed nuclear pyknosis of Schwann cells, vascular hyperemia, perineural edema, hyalinization of the collagenous stroma of the nerve, myelin sheet swelling, and loss of axons. Ablations were visible on CE MRI. Non-perfused volume of the lesions (5.8–64.6 cc) linearly correlated with estimated lethal thermal dose volume (4.7–34.2 cc). Skin burn adjacent to the largest ablated zone was observed in the first animal. Bilateral treatment time ranged from 55 to 138 min, and preparation time required 2 h on average.
The acute pilot study in swine demonstrated the feasibility of a noninvasive neurolysis of the sciatic nerve using a clinical MRgHIFU system. Results revealed that acute HIFU nerve lesions were detectable on CE MRI, gross pathology, and histology.
KeywordsHIFU Neurolysis Sciatic nerve MRI Ablation
We thank Dr. Haruyuki Takaki for discussion of swine anatomy imaging and Dr. Rachelle Bitton for valuable discussion of thermometry during MRgHIFU. Grant Support: Memorial Sloan-Kettering Society grant. This work used core facilities funded by NIH Core Grant # P30 CA 008748.
Conflict of interest
Stephen B Solomon has received research grant and personal fees from GE Healthcare. Elena A Kaye, Narendra Babu Gutta, Sebastien Monette, Amitabh Gulati, Jeffrey Loh, Govindarajan Srimathveeravalli, Paula C Ezell, Joseph P Erinjeri, and Majid Maybody declare that they have no conflicts of interest.
All applicable institutional and/or national guidelines for the care and use of animals were followed.
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