Spontaneous Regression of Vestibular Schwannomas: A Clinical And Radiographic Assessment

Background: Vestibular schwannomas (VSs) are benign nerve sheath tumors that arise from the vestibulocochlear nerve within the internal auditory canal (IAC) and extend into the cerebellopontine angle (CPA). It is the most common tumor of the CPA with an annual incidence of 17.4/1 million. They typically demonstrate slow growth over time and as such, observation is a reasonable approach to management. A portion of these tumor remains static and approximately 5 to 10% of these tumors will demonstrate spontaneous regression while under observation, including those associated with neurofibromatosis type 2. The standard treatment for symptomatic or growing lesions is surgical resection followed by radiation for residual tumor or reoccurrence; however, management recommendations encourage tailoring care to each patient and tumor individually. Several previous case series have attempted to identify predictive factors for tumor growth and regression, but few have reached significance or demonstrated reproducible findings. If factors were identified that could predict tumor growth one could intervene at an earlier stage of the disease. One meta-analysis conducted on growing tumors identified that size at diagnosis was the only predictive factor that reached significance. In a similar vein, defining factors that reliably predict spontaneous regression could prevent unnecessary intervention. As per our review of the literature, no patient characteristics have yet predicted spontaneous regression to date. Imaging characteristics including a festooned aspect of the tumor and the presence of cerebrospinal fluid in the IAC have been identified as predictive for tumor regression in small case series ( N = 13–14). Methods: Using a clinical database of VS treated by one team at our institution, we identified 40 patients who have demonstrated significant spontaneous regression or complete resolution of their VS. All patients received a survey by mail and telephone. For all patients who consented to participate, radiographic and clinical data was collected from patient charts in addition to survey responses. Medical comorbidities and medications provided through patient questionnaire were corroborated with patient charts. Tumor volume was approximated using the formula V = 4/3 × π × length/2 × width/2 × height/2 and nominal logistic regression was completed using JMPv17 with 50% tumor reduction as the reference value. Results: Ten patients were included in the final descriptive summary of this patient population. Tumors were generally small, left sided (8/10), with a fungated shape (6/10) and at least partial preservation of CSF in the IAC (8/10). Significant decrease in tumor volume was an inclusion criterion; however, no patient factors or radio graphic factors appeared to predict the degree of tumor regression. Conclusion: In conclusion, this is the first study to consider patient lifestyle factors obtained through patient survey in addition to clinical and radiographic findings to describe spontaneous regression of VS. Although there was perhaps a higher-than-average rate of herpes/varicella in this population, no clinical factors were found to be predictive on analysis. Additionally, no radiographic factors appear to be protective including those previously demonstrated to be protective, such as CSF preservation in the IAC and IAC extension. Publication History Article published online: 07 February 2025 © 2025. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany

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