This prospective study of 33 patients with 35 posterior fossa cavernomas treated by CyberKnife radiosurgery (CKRS) demonstrates the feasibility of treating larger lesion volumes with reduced radiation doses. The approach resulted in decreased hemorrhage rates post-treatment and acceptable neurological outcomes, supporting CKRS as a viable option for deep-seated or high-risk cavernomas.
Background
Cavernous malformations (CM) are vascular lesions prone to hemorrhage, especially when located in the brainstem or posterior fossa, where surgical risks are high. Hemorrhage is the most common clinical presentation, with recurrence rates highest in the first two years after bleeding. While surgical resection remains the gold standard, radiosurgery has emerged as an alternative for lesions in eloquent or deep brain regions. However, controversies persist regarding optimal radiosurgical dosing and volume treatment strategies.
CKRS was applied to posterior fossa cavernomas with a median marginal dose of 12 Gy for smaller volumes and 18 Gy in three fractions for larger or cerebellar white matter-adjacent lesions.
The majority of cavernomas were brainstem located (80%), with a mean volume of 1.11 cm³, larger than traditionally treated volumes.
Pre-treatment hemorrhage was frequent, with 59 bleeding events recorded and 54 CMs having at least one symptomatic bleed.
Radiosurgical targeting included the entire hemosiderin ring as delineated on T2-weighted MRI to encompass the lesion and surrounding affected tissue.
Patients received peri-treatment corticosteroids to mitigate inflammatory effects.
Follow-up imaging and clinical assessments were conducted regularly up to and beyond 24 months, with median follow-up of 13 months.
Clinical Implications
This study supports the use of CKRS with tailored dosing strategies to safely treat larger posterior fossa cavernomas, including brainstem lesions, reducing hemorrhage risk while minimizing radiation exposure. Incorporating the hemosiderin ring in target delineation and applying hypofractionation for larger volumes may optimize outcomes. Regular follow-up with MRI and neurological evaluation is essential to monitor treatment response and detect complications.
Conclusion
CyberKnife radiosurgery with adjusted dosing protocols enables effective management of posterior fossa cavernomas, balancing lesion coverage and radiation safety. This approach offers a promising alternative for patients with surgically challenging cavernomas, potentially improving hemorrhage control and neurological outcomes.
References
Al Shahi et al. -- Definition and assessment of hemorrhage in cavernous malformations
Timmerman et al. 2006 -- Hypofractionated stereotactic radiosurgery dosing recommendations
