Surgery

Surgery is considered a standard part of treatment for histological confirmation of tumor type and as a means to improve outcome. Total or near-total resections are considered optimal if they can be performed safely.[84,85]

Postoperatively, children may have significant neurological deficits caused by preoperative tumor-related brain injury, hydrocephalus, or surgery-related brain injury.[86][Level of evidence C1] A significant number of patients with medulloblastoma develop cerebellar mutism syndrome (also known as posterior fossa syndrome). Symptoms of cerebellar mutism syndrome, which usually appear within 1 or 2 days after surgery, include the following:

The etiology of cerebellar mutism syndrome remains unclear, although cerebellar vermian damage and/or disruption of cerebellar-cortical tracts has been postulated as the possible cause of the mutism.[87,88]; [89][Level of evidence C1] In two Children’s Cancer Group studies that evaluated children with both average-risk and high-risk medulloblastoma, the syndrome was identified in nearly 25% of patients.[88-90]; [91][Level of evidence C1] A retrospective analysis of 370 patients with medulloblastoma identified younger age, larger tumor size, and midline tumor location as risk factors for developing mutism. This finding is consistent with previous observations. Investigators also observed a correlation between medulloblastoma subtype and risk of mutism. Mutism was more common in patients with group 3 and group 4 medulloblastomas (30%–35% of patients) and less frequent in children with SHH-activated tumors (7% of patients).[92] A prospective study that included longitudinal neurological examination of 178 patients with medulloblastoma identified similar risk factors for mutism (higher risk with younger age; lower risk with SHH subtype), most likely because SHH-activated tumors tend to be located in the hemispheres and not in the midline. The study also reported a higher risk of developing mutism in patients who undergo tumor resections at low-volume surgery centers.[93] Approximately 50% of patients with this syndrome manifest long-term, permanent neurological and neurocognitive sequelae.[89,91]