Small tumors on cranial nerves, which can lead to hearing impairment, dizziness, and ringing in the ears, have typically been monitored without immediate intervention. However, a new study is shifting the perspective on how these tumors, known as vestibular schwannomas, are treated.
Patients with small cranial nerve tumors that can lead to issues like hearing loss, imbalance, and tinnitus have usually been observed rather than treated right away, as the risks associated with initial treatment were thought to be greater than the potential benefits. Recent research, however, has revealed that even these individuals gain substantial advantages from a non-invasive procedure called stereotactic radiosurgery, as found in a multicenter, global study led by physicians at UVA Health.
Typically, doctors focus on treating larger vestibular schwannomas while opting for a “watchful waiting” strategy with smaller tumors that do not pose significant issues. Nevertheless, research conducted by UVA Health neurosurgeon Jason Sheehan, MD, PhD, and his team has the potential to change how asymptomatic schwannomas are handled. Their study showed that stereotactic radiosurgery—a targeted radiation therapy—can help prevent the growth of small tumors, thereby protecting patients from possible long-term complications.
“This study, along with our recent Vestibular Schwannoma International Study of Active Surveillance versus Stereotactic Radiosurgery [VISAS] trial, indicates that radiosurgery offers effective and lasting tumor control while often minimizing the neurological problems associated with simply monitoring vestibular schwannomas,” Sheehan explained. “Over time, Gamma Knife radiosurgery alters the growth dynamics and associated challenges of even the tiniest vestibular schwannomas.”
Understanding Vestibular Schwannomas
Vestibular schwannomas are tumors that develop on the cranial nerve connecting the brain with the inner ear. This nerve is crucial for relaying information about head movements, maintaining balance, and facilitating hearing. But these growths can interfere with these vital functions, leading to issues like hearing loss, balance problems, headaches, tinnitus (ringing in the ear), facial numbness or paralysis, and other related complications.
To enhance care for individuals with these tumors, Sheehan and his team conducted a trial via the International Radiosurgery Research Foundation, which involved 261 adults diagnosed with the smallest type of vestibular schwannomas. These tumors were typically identified early, and the participants were generally functioning well, making them more susceptible to long-term consequences from tumor growth. Out of the participants, 182 were treated with stereotactic radiosurgery, while 79 did not receive this intervention.
Among those patients who had Gamma Knife radiosurgery, there was a much better preservation of tumor control over time. In this group, 99% of the tumors remained stable, displayed minimal growth (less than 25%), or actually shrank after 3, 5, and 8 years, with only one patient’s tumor significantly increasing in size.
In contrast, those who did not undergo radiosurgery had a much worse outcome: 37% experienced significant tumor growth at 3 years, 50% at 5 years, and 67% at 8 years.
Such differences were clearly reflected in the symptoms experienced by the patients. Those who received radiosurgery had a 54% lower incidence of tinnitus, a 51% lower rate of deterioration in cranial nerve function, and an 83% lower occurrence of vestibular dysfunction that leads to dizziness and unsteadiness.
Despite the delicate nature of the procedure using Gamma Knife radiosurgery, hearing preservation rates were similar in both groups.
Sheehan, who specializes in stereotactic radiosurgery and brain tumors, emphasizes the importance of these findings for physicians, as the symptoms associated with tumor growth can become irreversible. Taking action early, before symptoms manifest, could significantly enhance patients’ long-term well-being, he asserts.
“In the realm of brain surgery, especially when addressing nerves involved in hearing and balance, our methods must be exceedingly precise,” he stated. “This study demonstrates that Gamma Knife radiosurgery greatly improves the future prospects for patients with vestibular schwannomas.”
