Mutism of cerebellar origin is a well-described clinical entity that complicates operations for posterior fossa tumors, especially in children. This review focuses on the current understanding of principal pathophysiological aspects and risk factors, epidemiology, clinical characteristics, treatment strategies, and outcome considerations. The PubMed database was searched using the term cerebellar mutism and relevant definitions to identify publications in the English-language literature. Pertinent publications were selected from the reference lists of the previously identified articles. Over the last few years an increasing number of prospective studies and reviews have provided valuable information regarding the cerebellar mutism syndrome. Importantly, the clarification of principal terminology that surrounds the wide clinical spectrum of the syndrome results in more focused research and more effective identification of this entity. In children who undergo surgery for medulloblastoma the incidence of cerebellar mutism syndrome was reported to be 24%, and significant risk factors so far are brainstem involvement and midline location of the tumor. The dentate-thalamo-cortical tracts and lesions that affect their integrity are considered significant pathophysiological issues, especially the tract that originates in the right cerebellar hemisphere. Moderate and severe forms of the cerebellar mutism syndrome are the most frequent types during the initial presentation, and the overall neurocognitive outcome is not as favorable as thought in the earlier publications. Advanced neuroimaging techniques could contribute to identification of high-risk patients preoperatively and allow for more effective surgical planning that should focus on maximal tumor resection with minimal risk to important neural structures. Properly designed multicenter trials are needed to provide stronger evidence regarding effective prevention of cerebellar mutism and the best therapeutic approaches for such patients with a combination of pharmacological agents and multidisciplinary speech and behavior augmentation.
Marina Pitsika and Vassilios Tsitouras
Marina Pitsika, Jack Fletcher, Ian C. Coulter, and Christopher J. A. Cowie
Perioperative management of hydrocephalus in children with posterior fossa tumors (PFTs) remains challenging. The modified Canadian Preoperative Prediction Rule for Hydrocephalus (mCPPRH) has been previously described as a useful tool in predicting which children are at higher risk for permanent hydrocephalus following PFT resection and can be used in guiding treatment. The aim of this study was to externally validate this predictive model.
A retrospective review of the children treated in a single unit was conducted, recording all of the mCPPRH parameters (age, preoperative radiological diagnosis, presence of moderate/severe hydrocephalus, transependymal edema, and metastatic disease at the time of diagnosis), the need for a CSF diversion procedure at 6 months, time to surgery, and management of hydrocephalus. A receiver operating characteristic (ROC) curve was plotted using the mCPPRH, age, Evans index (EI), and frontooccipital horn ratio (FOHR), and an area under the curve (AUC) was calculated. A point-biserial correlation was run to determine the relationship between time to surgery, the insertion of an external ventricular drain (EVD), or initial EVD clamping and the development of postoperative persistent hydrocephalus.
From a total of 75 patients (mean age 6.99 years, 62.7% male) who were included in the study, 8 (10.7%) required permanent CSF diversion following PFT resection. The AUC of the ROC curve was 0.618 for the mCPPRH (p = 0.18, SE 0.088, 95% CI 0.446–0.791), 0.633 for age (p = 0.26, SE 0.119, 95% CI 0.4–0.867), 0.604 for the EI (p = 0.34, SE 0.11, 95% CI 0.389–0.818), and 0.663 for the FOHR (p = 0.17, SE 0.121, 95% CI 0.427–0.9). A significant positive correlation between EVD insertion (r = 0.239, p = 0.03) and insertion of a ventriculoperitoneal shunt was found. A negative correlation between the postoperative clamping of the EVD (r = −0.158, p = 0.4) and the time to PFT surgery (r = −0.06, p = 0.6) did not reach statistical significance.
The implementation of the mCPPRH score failed to reliably predict which children would require permanent CSF diversion following PFT resection when applied to this cohort. Clinical judgment remains the mainstay of choosing the perioperative treatment of hydrocephalus.