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spasticity is a clinical event characterized by increased muscle contraction, sometimes painful, secondary to central nervous system damage. It leads to a high rate of nursing procedures, hospital admissions, and costs and quality of life impairment with problems in sleeping, breathing, and speaking. Standard treatment for systemic spasticity is represented by oral or intrathecal baclofen. In the case of focal spasticity, available treatment options are intramuscular botulinum toxin, alcoholic or surgical neurolysis or even selective neurotomies or rhizotomies. However, these surgical procedures are characterized by prolonged surgical sessions and may have infective, anesthetic and surgical complications. They requires an experienced team, the costs are relatively high, and the learning curve is slow. The aim of the present study is to evaluate the therapeutical effectiveness of linac-based stereotactic radiosurgery (SRS) in the treatment of malignant spasticity.

patients with spasticity to the lower limbs unresponsive to systemic therapies were treated with linac-based SRS to the spinal nerves responsible for the spasms within a prospective observational trial (n° 51262). Treatment dose was 45 Gy in a single fraction delivered with VMAT technique. The primary end-point was the reduction of the muscular resistance to passive movement measured with the Modified Ashworth Scale (MAS). Secondary end-points were toxicity, quality of life, and spinal nerves radiological features (fractional anisotropy, diffusivity).

from December 2020, the first 4 patients were treated at our Institution. The first patient was treated at the bilateral nerves L4-S1 and had a complete spasms resolution the day after SRS administration that lasts 10 months after treatment. The second was treated at bilateral levels L3-L5 and had a progressive reduction up to 40% of the spasms over 4 months (fig. 1). The third patient was treated at the bilateral L4-5 and left S1. After 2 months, she had a MAS reduction (2 versus 3), however she died of thromboembolism 6 months after SRS. Patient 4 had MAS 3 and was treated at the bilateral L3-4. Few days after SRS administration he had a complete response to treatment with MAS 0, which lasted 3 months after treatment. No acute treatment-related toxicities or spasticity relapse were reported.

Figure 1. Treatment plan and DVH of patient 2

the present is the first clinical report on the use of a linac-based SRS for the treatment of malignant spasticity. These preliminary results with a short follow-up documented a clinical activity of SRS that will be explored in a larger population to better assess effectiveness, toxicity, and duration of the response.