# Linear Accelerator-Based Stereotactic Radiosurgery (SRS) for Arteriovenous Malformation (AVM) With Functional Magnetic Resonance Imaging (fMRI) Brain Mapping for Toxic Avoidance

## TL;DR

A military sniper with a brain arteriovenous malformation (AVM) was successfully treated with linear accelerator-based stereotactic radiosurgery (SRS) using functional MRI to avoid damaging critical brain areas.

## Contribution

This case report demonstrates the successful use of fMRI and linear accelerator-based SRS for a high-grade parietal AVM near critical brain regions.

## Key findings

- Functional MRI identified motor and sensory brain regions to avoid toxicity during SRS.
- The AVM was completely obliterated after treatment with no significant toxicity.
- A multidisciplinary approach enabled precise radiotherapy planning near the lateral sinus and hand grip region.

## Abstract

While the treatment of unruptured arteriovenous malformation of the brain (bAVM) is controversial, active intervention is usually recommended for patients who have had a previous intracerebral hemorrhage. Stereotactic radiosurgery (SRS) is the preferred treatment for bAVM when the patient is unsuitable for surgery or embolization. Currently, linear accelerator-based cranial SRS is gaining popularity, and this case report describes the multidisciplinary approach in treating a military sniper with a 3.2 cm x 3.5 cm x 3.7 cm Spetzler-Martin Grade 3 left high parietal AVM using this technique.

Functional MRI (fMRI) with block designs was used to identify the motor and vibrotactile areas of the hand and fingers. The patient underwent CT-simulation with frameless double-shell thermoplastic stereotactic mask immobilization followed by CT angiogram in the same position. After co-registration of CT simulation and MRI images, SRS planning was performed with the Eclipse Treatment Planning System (TPS). Two prescription dose levels of 20 Gy and 14 Gy were used. The dose constraints applied in the TPS were: Maximum dose (Dmax) of 16 Gray to the inner/medial wall and 12 Gray to the outer/lateral wall of the left lateral sinus, and 20 Gray to the motor and sensory regions of the brain. Radiological assessment after 32 months showed complete obliteration of the AVM, and the patient did not have any significant toxicity. He is back to his regular job as an army sniper in the armed forces.

With the current technological advent of linear accelerators and the TPS algorithms with inverse planning capacity, highly variable and conformal brain SRS plans can be generated based on an individual patient’s disease anatomy. Since bAVM is a benign disease and patients may have a long survival after treatment, it is important to ensure that the toxicity from the intervention is minimized. A multidisciplinary team successfully mapped adjacent brain areas, identified the bAVM target, and executed a complex radiotherapy plan, resulting in good outcomes for a patient with parietal bAVM near the hand grip region and left lateral sinus.