Siobhan Haney, VMD, MS, DACVR (RO), MBA
The patient’s initial clinical signs included seizures and abnormal behavior which would last for several minutes at a time. Other clinical signs included stumbling and lethargy. The dog’s primary care veterinarian tried a course of antibiotics which initially seemed to help but the abnormal neurologic episodes returned. He was seen by a neurologist where an MRI was performed. This revealed a mass in his brain, specifically his frontal/ parietal lobes, which appeared to be most consistent with a meningioma. He was started on an anti-convulsant and steroid medication at that time (Levitiracetam and dexamethasone). All other staging tests including chest x-rays and bloodwork were within normal limits. The patient’s diagnostic MRI is shown below in Figure 1. The brain tumor, a meningioma, is circled in red.
The dog was treated with 3 treatments (fractions) of CyberKnife, which were administered over a 1-week period. This treatment is only possible due to the development of highly advanced radiation technologies that permit maximum dose delivery within the target while minimizing dose to the surrounding healthy tissue. The goal is to deliver doses that will destroy the tumor and achieve local control. This allows the dose of radiation to be given in 3 treatments as compared to 16-20 treatments of conventional radiation. Figure 2 depicts the patient’s radiation plan.
When the CyberKnife treatments were completed, the patient did not have any toxicities or side effects that were attributable to the radiation therapy. His owners reported that his quality of life was excellent at home. He remained on anti-convulsant medication after his treatments, which is standard protocol for patients with brain tumors. He did not have any further seizures after his treatment was complete.
Approximately 10 months after his CyberKnife treatments, the patient underwent a second MRI. This showed a complete remission of the meningioma. The meninges in the area previously occupied by the tumor enhanced with the administration of a contrast agent, however, this was likely due to scar tissue formation in the area after his treatment. Figure 3 shows his original MRI and his comparison MRI performed 10 months later. The red arrows show the meningioma (picture on the right) and the blue arrows (picture on the left) show the suspected scar tissue remaining after the treatment was completed.
This case report documents the successful treatment of a patient with a meningioma that was not amenable to traditional surgery and the significant tumor response leading to long term survival of the dog.