new definition: Post-operative pediatric CMS

Post-operative pediatric cerebellar mutism syndrome is characterized by delayed onset mutism/reduced speech* and emotional lability after cerebellar or 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 from CMS may be prolonged. Speech and language may not return to normal, and other deficits of cognitive, affective and motor function often persist [1].

*Speech production that is severely reduced and limited to single words or short sentences that can only be elicited after vigorous stimulation.                                                                                                                                      **Impairment of gait (ataxia), extremity coordination (dysmetria), disor- dered eye movements, poor articulation (dysarthria), impaired swallowing (dysphagia) and tremor.                                                               ***A pattern of behavioral abnormalities that includes impairments of ex- ecutive function (planning, set-shifting, abstract reasoning, verbal fluen- cy, working memory), often with perseveration, distractibility or inattention; visual-spatial disorganization and impaired visual-spatial memory; personality change with blunting of affect or disinhibited and inappropri- ate behavior; and difficulties with language production including dysprosodia, agrammatism and mild anomia.                                                                                                                                                                                                                                                                       ****Symptoms such as urinary retention/incontinence and hemiparesis, which are frequently observed in this patient population.

core symptom: CM

The hallmark characteristic of post-operative pediatric CMS is CM, which is transient muteness that follows lesions of the cerebellum as opposed to the cerebrum or lower cranial nerves. Its unique features are delayed onset and limited duration followed by a recovery period where speech is marked by dysarthria [2]. It has recently been futher characterized as absence of speech (verbal mutism) and not absence of non-verbal sounds (i.e. whining, crying, laughter) [1].

Older related terms: PFS, AM, PP, tCM, MSD, CMS, PFS, CCAS

Until recently there existed no international consensus on definitions of post-operative pediatric CMS or related conditions. The spectrum of symptoms that can be seen in children after cerebellar or 4th ventricle tumor surgery (neuropsychological, neurological, speech- and language related symptoms) was frequently described as Posterior Fossa Syndrome (PFS). Other common definitions and abbreviations are: Akinetic Mutism (AM), Cerebellar Mutism (CM), Transient Cerebellar Mutism (TCM); Mutism and Subsequent Dysarthria (MSD), Cerebellar Mutism Syndrome (CMS - not the same as the new definition of post-operative pediatric CMS), and the Cerebellar Cognitive Affective Syndrome (CCAS) [1].  Many authors still use these terms interchangeably in their articles [2-3].

See Fig 1 below for a schematic presentation of the inter-relationship of these old definitions, and the Incidence page for information on how this myriad of overlapping terms has affected reported study results.

Fig. 1 Symptomatic spectrum and relationship between the PFS, CCAS and related conditions


Entire figure

PFS = Posterior Fossa Syndrome

Left half of figure (excluding CM)

CCAS = Cerebellar Cognitive Affective Syndrome

Inner circle (light gray area)

CMS = Cerebellar Mutism Syndrome (old definition)

Dotted area

MSD = Mutism and Subsequent Dysarthria

Core (dark gray area)

CM = Cerebellar Mutism                                                                                                    TCM = Transient Cerebellar Mutism (synonym)

Striped area

Cerebellar signs                                                                                                           Cerebellar Syndrome (synonym)



Fig. 1   Schematic illustration of the symptomatic spectrum and relationship between the PFS, CCAS and related conditions. The old PFS definition refers to neuropsychological, neurological, speech- and language related symptoms. It has most commonly been described in children after posterior fossa tumor surgery, but may also occur following trauma, vascular incidents and infections. The CCAS consists of neuropsychological and language-related symptoms, but does not include CM or neurological/motor symptoms. The CMS covers some of the most characteristic features of each category of the PFS (mutism, ataxia, hypotonia, irritability), while the syndrome of MSD focuses on the speech- and language-related part of the spectrum. At the core of these three post-operative syndromes (PFS, CMS and MSD) lies CM, also known as TCM. The cerebellar syndrome is a synonym for typical motoric signs that can be observed both pre- and post-operatively in posterior fossa tumor patients. Neither the cerebellar syndrome nor the CCAS include CM.

NB - the new definition of POP-CMS is not illustrated on Fig. 1

Links to:

Incidence, Symptoms, Anatomy, Pathophysiology, Imaging findings, Risk factors, Prognosis, Treatment, Prevention

1. Gudrunardottir T, Morgan AT, Lux AL, Walker DA, Walsh KS, Wells EM, Wisoff JH, Juhler M, Schmahmann JD, Keating RF, Catsman-Berrevoets C, for the Iceland Delphi Group (2016) Consensus Paper on Post-operative Pediatric Cerebellar Mutism Syndrome: The Iceland Delphi Results. Childs Nerv Syst May 3. [Epub]

2. Gudrunardottir, T., Sehested, A., Juhler, M., Grill, J., & Schmiegelow, K. (2011a). Cerebellar mutism: definitions, classification and grading of symptoms. Childs Nerv.Syst., 27, 1361-1363

3. Thomale, U. W. & Driever, P. H. (2013). Inconsistent terminology for cerebellar mutism. Childs Nerv.Syst., 29, 717-718

3. Schmahmann, J. D. & Sherman, J. C. (1998). The cerebellar cognitive affective syndrome. Brain, 121 ( Pt 4), 561-579