Development and application of a diagnostic and severity scale to grade post-operative pediatric cerebellar mutism syndrome

The post-operative pediatric cerebellar mutism syndrome (CMS) affects about one-third of children and adolescents following surgical removal of a posterior fossa tumor (PFT). According to the Posterior Fossa Society consensus working definition, CMS is characterized by delayed-onset mutism/reduced speech and emotional lability after cerebellar or 4th ventricle tumor surgery in children, and is frequently accompanied by additional features such as hypotonia and oropharyngeal dysfunction/dysphagia. The main objective of this work was to develop a diagnostic scale to grade CMS duration and severity. Thirty consecutively referred subjects, aged 1–17 years (median 8 years, IQR 3–10), were evaluated with the proposed Post-Operative Pediatric CMS Survey after surgical resection of a PFT and, in case of CMS, for 30 days after the onset ( T 0 ) or until symptom remission. At day 30 ( T 1 ), CMS was classified into mild, moderate, or severe according to the proposed scale. CMS occurred in 13 patients (43%, 95% C.I.: 25.5–62.6%), with mild severity in 4 cases (31%), moderate in 4 (31%), and severe in 5 (38%). At T 1 , longer symptom persistence was associated with greater severity ( p = 0.01). Greater severity at T 0 predicted greater severity at T 1 ( p = 0.0001). Children with a midline tumor location and those aged under 5 years at diagnosis were at higher risk of CMS ( p = 0.025 and p = 0.008, respectively). In conclusion, the proposed scale is a simple and applicable tool for estimating the severity of CMS at its onset, monitoring its course over time, and providing an early prognostic stratification to guide treatment decisions. What is Known: • Post-operative pediatric Cerebellar Mutism Syndrome (CMS) is a complex phenomenon with a wide spectrum of symptoms that may manifest in children undergoing the resection of a posterior fossa tumor (PFT) and that can result into long-term impairment. What is New: • This study developed and pilot-tested an easily applicable diagnostic and severity scale to grade the duration and the severity of symptoms of the CMS. • The proposed scale was found to be a sensitive instrument to identify even mild CMS presentations. • By scoring not only the duration but also the severity of symptoms the scale allows a more accurate prognostic stratification for an optimal planning of clinical and rehabilitative interventions.