Evaluation of factors associated with the occurrence of cerebellar mutism syndrome after resection of pediatric medulloblastoma in 3 cases

<p>Objective: Cerebellar mutism syndrome (CMS), which consists of mutism, ataxia, and emotional disorder, is well known as a complication of the surgical procedure for pediatric medulloblastoma. Currently, risks for CMS are considered to be splitting of the vermis, younger age, and tumor size over 5 cm in diameter, but the exact mechanisms remain unknown. The aim of this study was to evaluate the risk factors for CMS occurrence in 3 CMS cases of pediatric medulloblastoma.</p><p>Patients and Methods: From 2009 to 2020, 11 pediatric medulloblastoma patients were hospitalized for resection or postoperative chemotherapy at Yokohama City University Hospital. One of the patients underwent surgery twice and 2 patients had undergone surgery at another hospital previously. The patients’ median age was 5 years (range, 2-16 years). The maximum tumor diameter ranged from 29 to 62 mm (mean, 47.8 mm). All the patients presented with obstructive hydrocephalus and severe cerebellar ataxia before surgery, but they were able to speak.</p><p>Results: Among all 12 surgical procedures, gross total resection was achieved in four; subtotal resection, in seven (residual volume <1.5 cm³, which was adherence to the brainstem and cerebellar peduncle) ; and partial resection, in one (following an additional operation). Three patients (27.2%), including the patient whose operation was performed at another hospital, presented CMS; 1 of the patients was able to speak 1 month later, and the other two patients recovered 4 months later. There was no correlation of the CMS with the maximum tumor diameter and the degree of resection (p>0.05). Splitting of the vermis was not performed in any of the cases. All 3 CMS cases presented new hyperintensity in the unilateral superior cerebellar peduncle on the MRI T2-weighted images after the operation. The hyperintensity in the unilateral superior cerebellar peduncle disappeared within several months. In the other 8 cases without CMS, hyperintensity in the T2-weighted images was visible only in one (p＝0.024). This patient showed severe cerebellar ataxia and dysarthria, but no mutism.</p><p>Conclusions: The current findings may explain the possible mechanism of CMS as involvement of the dentatothalamocortical pathway, which exists between the dentate nucleus of the cerebellum and the cerebellar cortex via the superior cerebellar peduncle. Careful retraction and coagulation especially surrounding the superior and inferior vermis is important to avoid the occurrence of CMS.</p>