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  • Updated 04.29.2024
  • Released 11.13.2003
  • Expires For CME 04.29.2027

Cerebellar mutism syndrome



This update on cerebellar mutism adds current literature regarding risk factors associated with cerebellar mutism as well as the ongoing efforts to mitigate those risk factors. Longer-term neurocognitive prognosis following the diagnosis of cerebellar mutism is also included.

Key points

• Cerebellar mutism is not necessarily a transient disease. Although the mutism typically resolves, patients are still likely to chronically have varying degrees of dysarthria, ataxia, and cognitive dysfunction.

• A consensus statement has defined cerebellar mutism with the intent of clearly identifying and unifying the multiple signs and symptoms that are associated with cerebellar mutism. Specifically, it explicitly cites this disease as being a postoperative consequence in children in the effort to further research and improve the quality of life for these patients.

• Damage to the dentato-thalamo-cortical fiber tracts and proximal efferent cerebellar pathways are being identified via imaging and metabolic studies in patients with cerebellar mutism.

• There is still no clear cause for cerebellar mutism. However, bilateral cerebellar damage, brainstem invasion/compression by tumor, and large tumor size are noted as risk factors in multiple papers.

• Patients with cerebellar mutism exhibit greater short- and long-term neurocognitive impairment that require close follow-up and intervention.

Historical note and terminology

A child’s loss of speech after removal of a cerebellar tumor was initially described in 1958 (21). This complication of posterior fossa surgery was mentioned in the literature in the following decades (44; 92) and became more widely recognized after a landmark case series of six patients in 1985 (87). Since then, the descriptions of hundreds of additional cases have contributed to the understanding of this unique constellation of signs and symptoms that to be known as the posterior fossa or cerebellar mutism syndrome. Cerebellar mutism syndrome is characterized by partially reversible decreased production of speech and often mutism, frequently in association with diffuse cerebellar dysfunction (ataxia and axial hypotonia), and a variety of neurobehavioral affective disturbances consisting of prominent emotional lability with irritability and apathy (44; 92; 116; 87; 110; 08; 25; 32; 36; 70; 94; 16; 42; 23; 74; 05; 10; 55; 03; 20; 84; 108; 49; 62; 93; 13; 38; 48; 60; 107; 15; 27; 100; 37; 47; 111; 65; 103; 78; 79; 90).

Given the multiple names and constellation of symptoms associated with mutism after cerebellar surgery, the Posterior Fossa Society was formed in 2014. The group issued a consensus statement in 2016, which introduced the term “postoperative pediatric cerebellar mutism syndrome” in an effort to unify the literature (40). The core symptom of postoperative pediatric cerebellar mutism syndrome is cerebellar mutism, defined as a transient reduction in speech due to damage to the cerebellum (as opposed to other structures involved in speech production such as the cerebral cortex and cranial nerves). The consensus statement reads: “Post-operative pediatric CMS is characterized by delayed onset mutism/reduced speech and emotional lability after 4th ventricle tumor surgery in children. Additional common features include hypotonia and oropharyngeal dysfunction/dysphagia. It may frequently be accompanied by the cerebellar motor syndrome, cerebellar cognitive affective syndrome and brain stem dysfunction including long tract signs and cranial neuropathies. The mutism is always transient but recovery may not return to normal, and other deficits of cognitive, affective and motor function often persist” (40). For the remainder of this review, we will refer to this syndrome as cerebellar mutism syndrome (or CMS).

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