Clinical manifestations

Presentation and course

The symptoms of postoperative cerebellar mutism typically have onset 1 to 2 days after posterior fossa surgery (116; 32; 70; 19; 84; 108; 93; 37). Clinical manifestations consist of abnormalities in speech or mutism, neurobehavioral or affective disturbances, diffuse cerebellar dysfunction, long tract findings, and cranial neuropathies.

Speech impairment is characterized by transient decreased production of speech and or complete mutism. When present, speech is limited to single words or short phrases, which are only elicited by repeated prompting. In a prospective cohort study of 60 children with medulloblastoma and postoperative cerebellar mutism undergoing tumor resection, 40 (66%) had complete and 20 (33%) had partial mutism (53). In most cases, receptive language is preserved relative to expressive language, although deficits in comprehension have been reported (109; 49; 93; 48). More language abnormalities associated with the mutism syndrome can go beyond deficient speech and articulation. A pervasive communication deficit, affecting comprehension as well as expressive language, was also noted in a significant number of patients with cerebellar mutism syndrome on comprehensive language evaluation during recovery (100). Speech improved in six of seven children who developed mutism after posterior fossa tumor resection but returned to normal in only one of them (103).

With recovery from cerebellar mutism syndrome, a speech pattern characterized as ataxic dysarthria has been described in a large fraction of patients. A review of 134 cases from the literature reported that 106 patients (79%) had dysarthric speech after resolution of the mutism (37). This finding has led to the hypothesis that the mutism may represent the most severe form of dysarthria, in effect, an ataxic anarthria (108; 107; 15).

Besides the core impairments in speech, cerebellar ataxia is nearly universal in cerebellar mutism syndrome. Some degree of ataxia was present with cerebellar mutism syndrome in 106 of 107 patients with cerebellar mutism syndrome in a multicenter prospective study; the ataxia was reported to be severe in 44% of them (90). This finding was corroborated in a prospective cohort study of 60 children with medulloblastoma and cerebellar mutism syndrome, all of whom had ataxia (53). Apraxia was also common, occurring in 40 (66%) patients. Movement disorders were seen in 28 (16%) of patients and included multifocal myoclonus, focal dystonia, tremor, ballism, and dyskinesias. Ocular abnormalities were seen in 18 (30%) of patients and presented primarily with impaired ocular fixation.

Most patients with cerebellar mutism syndrome exhibit a spectrum of neurobehavioral abnormalities. Substantial emotional lability and irritability is commonly described (116; 18; 109; 84; 100). In one series, an almost stereotypical response with inconsolable shrill whining occurred in 11 of 12 patients (84). Striking apathy and lack of initiative or hypokinesis are also commonly reported (46; 109; 100).

A variety of other neurologic abnormalities have also been noted in patients with cerebellar mutism syndrome. In the absence of bulbar cranial nerve deficits, decreased oral intake or oromotor apraxia has been described (46; 32; 109; 20; 84; 38; 48; 100). Persistent eye closure for prolonged periods, with apparent inability to initiate spontaneous opening of the eyes and usually in the absence of oculomotor deficits, was noted in two series (84; 100). Cerebellar mutism syndrome typically occurs in the absence of significant cranial nerve deficits or long tract signs (70; 31), although pontine cranial nerve deficits (VI or VII) or hemiparesis were found in several series (109; 84; 108; 100). The abrupt onset of visual loss has been reported in association with cerebellar mutism syndrome (22). Transient urinary and fecal incontinence was associated with the syndrome in five of eight patients in one series (100).

Prognosis and complications

Almost all patients with cerebellar mutism syndrome experience resolution of mutism symptoms, although most exhibit residual ataxic dysarthria and other deficits (30; 37). In a case series of 134 patients with cerebellar mutism syndrome reported in the literature, the mutism resolved at a mean of 8 weeks, with a range of 4 days to 5 months (37). A case-control study of children after cerebellar tumor resection demonstrated significantly more long-term residual ataxic dysarthria in those who had suffered cerebellar mutism syndrome than in those who had not (45). A critical review of 283 children with cerebellar mutism syndrome found that 99% displayed ataxic dysarthric motor speech deficits after recovery from the period of being totally mute (24).

Other lingering neurologic sequelae are also common. In a multicenter prospective evaluation of cerebellar mutism syndrome among medulloblastoma patients, persistent ataxia and speech difficulties were present to a moderate or severe degree for as long as 1 year from diagnosis in 66% (ataxia) and 44% (speech) of the patients who were initially judged to have had a severe degree of the syndrome (90). More significant residual speech deficits and a trend toward more ataxia was also seen among the initially most severe of 11 cerebellar mutism syndrome patients in one case series (112). Moreover, intellectual deficits that extend beyond strictly linguistic function have been noted in some patients recovering from cerebellar mutism syndrome. In one series, several of the 12 children recovering from cerebellar mutism syndrome had impairments in recent memory, attention span, problem-solving ability, and executive function on detailed neuropsychometric testing (84). As well, a significant fraction of patients with cerebellar mutism syndrome in the prospective medulloblastoma study were estimated to have persistent mild to moderate deficits of global cognitive function at 1 year from initial diagnosis of their tumors (90).

Persistent psychosocial problems, including obsessive-compulsive disorder, withdrawal behavior, and general difficulties with social interaction, were reported to be significantly more frequent in medulloblastoma patients who had experienced postoperative cerebellar mutism (117). Neurocognitive data available in 12 of 28 children after medulloblastoma tumor resection at a mean of 4.5 years after surgery demonstrated mean IQ to be 16 points lower among the five children with cerebellar mutism syndrome (112). At 1, 3, and 5 years following diagnosis of medulloblastoma, children who were initially diagnosed with posterior fossa syndrome following their treatment for medulloblastoma had lower mean scores on measures of general intellectual ability, processing speed, broad attention, working memory, and spatial relations compared to those without diagnosis of posterior fossa syndrome. Attention and working memory were also noted to decline over time. The posterior fossa syndrome group had mean scores at least one standard deviation below the mean for intellectual ability, processing speed, and broad attention across all time points and for working memory by 5 years postdiagnosis (97).

Clinical vignette

A 6-year-old boy presented to the emergency room with a history of progressive headache, morning vomiting, and unsteadiness of gait that had been getting worse over the previous 2 to 3 weeks. He was also complaining of double vision that was worse on left lateral gaze. On examination, he was mildly lethargic, but mental status was otherwise normal. His visual acuity and fields were normal, but bilateral papilledema was present. He had a partial left sixth nerve palsy and a mild degree of truncal ataxia. On brain MRI, there was a 4 X 3.5 X 3.5 cm homogeneous, gadolinium-enhancing mass arising from the cerebellar vermis and within the fourth ventricle, obstructing its outflow and causing a moderate degree of hydrocephalus.

After placement of an external ventriculostomy, the boy underwent a suboccipital craniotomy and gross total resection of the tumor, which was seen to be adherent to the brainstem. The histopathological tumor diagnosis was medulloblastoma. Disease-staging evaluation revealed no spinal metastases or residual tumor on postoperative MRI, and CSF cytologic examination was negative for neoplastic cells. He was extubated quickly following the surgery and had no new neurologic deficits in the immediate postoperative period.

His headaches resolved, the sixth nerve palsy improved, and he was noted to be speaking normally in short sentences to his parents and nurses. His ventriculostomy was weaned over 5 days, and he did not require shunting.

Then, on the second postoperative day, he stopped talking entirely and became extremely irritable, vocalizing only with frequent whining or high-pitched crying. He appeared to follow some verbal commands but would not always do so during periods of irritability. He did not want to eat and appeared to have difficulty with the initiation of chewing and swallowing, but he had no aspiration of liquids or solids on a swallow study. These symptoms persisted more or less unchanged for 2 to 3 weeks, after which time, he started to speak a few single words and was becoming less irritable.

As his speech gradually improved over the subsequent 2 months while he was undergoing craniospinal irradiation, it became apparent that he had an ataxic dysarthria as well as mild truncal ataxia. After completion of radiation therapy, he began a course of adjuvant chemotherapy. His speech and language comprehension, along with his gait, continued to improve during the chemotherapy, and his parents considered that his speech articulation and content were nearly back to normal by 1 year from diagnosis. There was no evidence of recurrent tumor on routine surveillance imaging. However, on detailed neuropsychometric testing at that time, he was found to have mild deficits of language comprehension, auditory processing, and executive function.

Biological basis

Etiology and pathogenesis

Tumor type and location. Most patients affected by cerebellar mutism syndrome are children who have undergone resection of midline cerebellar or fourth ventricular tumors. In a review of cases of cerebellar mutism, 117 of 134 (89%) had midline posterior fossa tumors, of which 85 (63%) were medulloblastomas, 24 (18%) were astrocytomas, and 19 were ependymomas (14%) (37).

The occurrence of brainstem involvement by tumor was a factor found to significantly correlate with the development of cerebellar mutism syndrome in the Children’s Oncology Group medulloblastoma study (90). Several series have shown an association between brainstem involvement and the development of mutism (32; 109; 84; 64; 85; 98). A metaanalysis of 28 studies involving 2276 pediatric patients identified tumor invasion of the brainstem (OR 4.3, 95% CI 2.2–8.2), fourth ventricle (OR 12.8, 95% CI 4.3–38.4), and superior cerebellar peduncle (OR 6.8, 95% CI 2.4–19.5) as significant risk factors for cerebellar mutism syndrome (83).

Surgical approach. From a review of the operative approach to posterior fossa tumor surgery at a single institution, Dailey and colleagues found a correlation between cerebellar mutism syndrome and splitting the inferior cerebellar vermis, which they postulated as an etiology (20). Indeed, surgical approaches using a vermian incision has been associated with cerebellar mutism and a subsequent low IQ (20; 15; 89; 39; 86). Kellog and Piatt reported a surgical approach to fourth ventricular tumors without splitting the vermis that avoided mutism (52). In another series, no cerebellar mutism syndrome was reported among 16 patients who underwent resection of fourth ventricular tumors by a telovelar surgical approach that avoided splitting vermian structures (29). Further, a combined transventricular and supracerebellar infratentorial approach preserving the vermis avoided the mutism syndrome in four patients with giant posterior fossa tumors that involved the tectum and the 4th ventricle (43).

Cerebellar-cortical connections. The role of the cerebellum extends beyond the motor domain. A spectrum of nonmotor cognitive deficits, some of which are seen in cerebellar mutism syndrome, has been described in patients with a variety of cerebellar diseases or injuries. This has been called cerebellar cognitive affective syndrome and is characterized by disturbances of executive function, visual-spatial disorganization, and nonarticulation language problems, including mild anomia and agrammatism. Personality changes with blunting or disinhibition of affect are also seen (33; 95; 113). In a network analysis of 30 pediatric patients with cerebellar mutism syndrome, lesions involving the vermis and inferomedial cerebellar lobules were associated with disruptions in cerebellothalamocortical circuitry similar to abnormalities seen in patients with autism spectrum disorder (104).

These clinical observations are supported by experimental neuroanatomic studies in primates and by functional imaging in humans, showing cerebellar involvement in extramotor functions. Using a retroviral detector in monkeys, a direct connection was demonstrated between dentate nuclei and the nonmotor prefrontal cortex, a region known to be involved in spatial working memory and future behavior-planning (66). Functional imaging with PET and fMRI methodology showed cerebellar activation in complex human cognitive operations such as puzzle-solving, sensory discrimination, and visual attention in the complete absence of motor activity. Moreover, this localization was in discrete areas of the cerebellum independent of those activated by motor activity (33; 54; 35; 06). A role for the cerebellum in mediating emotional behavior was demonstrated by the alleviation of aggressive behaviors in isolation-reared primates after the production of various cerebellar lesions (82; 12). Functional connections have also been identified between cerebellar and limbic structures, further strengthening a hypothesis that the cerebellum can modulate behavior and emotion (09; 41).

Several investigators have postulated the dentato-thalamo-cortical pathways as the anatomical substrate of cerebellar mutism (25; 19; 34; 84; 30; 58). These pathways project both to and from the dentate nucleus of cerebellum on either side, crossing in the superior and middle cerebellar peduncle, through the brainstem to the contralateral red nucleus and thalamus and on to the premotor and supplementary motor cortex (Adams and Victor 1993; 75). There is evidence that injury anywhere along the dentato-thalamo-cortical pathways can produce mutism. However, the proximal segment of the dentato-thalmo-cortical pathway appears to be clinically most relevant, as tumors and surgical resection occur within the region of this pathway (03; 91; 59). The proximal efferent cerebellar pathway consisting of the dentate nucleus, the superior cerebellar peduncle, and the mesencephalic tegmentum appear to be involved on imaging of patients with cerebellar mutism (109; 84; 113; 69; 86; 67; 75).

Injury of the dentate-thalamo cortical pathway is thought to lead to cerebello-cerebral diaschisis. This causes hypoperfusion and decreased metabolic activity in the corresponding cerebral cortex due to lack of excitatory stimulation from the cerebellum. Perfusion and diffusion tensor imaging studies have demonstrated this connection (38; 91; 69; 67; 102).

Children have become mute after injury to the brainstem, in which the proximal portions of the dentato-thalamo-cortical tracts travel. Mutism has occurred after surgical treatment of a pontine cavernous hemangioma or brainstem tumor (76; 109; 34) or after brainstem stroke (68). Brainstem involvement by tumor correlated with the development of cerebellar mutism syndrome in several series, including the multicenter medulloblastoma study, and could localize dysfunction to the brainstem within the dentato-thalamo-cortical pathways (84; 108; 90). A higher incidence of brainstem tumor invasion was also found in a series of 11 of 28 patients with cerebellar mutism syndrome after medulloblastoma surgery (112). In a prospective case-control study of 26 children, 13 with cerebellar mutism and 13 without cerebellar mutism after posterior fossa surgery, postoperative MRI signal abnormalities were observed more often in the superior cerebellar peduncles and midbrain in children with mutism than in controls (69). On DTI, there was lower fractional anisotropy of water in white matter tracts in bilateral superior cerebellar peduncles and bilateral fornices in the cerebellar mutism cohort, reflecting more interruption of white matter tracts in these areas.

Diffusion abnormalities in the proximal efferent cerebellar pathway have been associated with the development of cerebellar mutism, particularly bilateral involvement of the proximal efferent cerebellar pathway (11). Another group noted bilateral diffusion abnormalities about the surgical cavity and likely involving the dentate nucleus as being a risk factor (17). The superior cerebellar peduncles may also demonstrate abnormalities in diffusion-weighted images as well as on FLAIR in those with cerebellar mutism (106). Hypertrophic olivary degeneration can be demonstrated on MRI in patients with cerebellar mutism. This finding is thought to be caused by denervation injury of Mollaret triangle and further implicates the proximal efferent cerebellar pathways as the causative site of injury (11; 81).

Diffusion tensor imaging (DTI) and tractography map white matter fiber tracts on MRI. Reduced cerebello-thalamo-cortical volumes in postoperative patients with medulloblastomas evaluated via DTI correlated with poorer motor outcomes for patients (73). Other studies utilizing DTI found decreased fiber tract organization (reduced fractional anisotropy) within the bilateral superior cerebellar peduncles that persisted beyond a year post development of cerebellar mutism (75; 63). Decreased fronto-cerebellar association fibers volumes were also seen in patients with cerebellar mutism along with diminished fiber signal from the superior cerebellar peduncles and midline cerebellar structures in patients with cerebellar mutism, suggesting a link for the neurocognitive sequelae seen in patients with cerebellar mutism (102). These clinical observations and imaging data suggest that mutism after posterior fossa tumor surgery could involve dentato-thalamo-cortical pathways and most likely the dentate, superior cerebellar peduncle, and/or brainstem portions.

Wisoff and Epstein postulated that edema developing in supranuclear afferent pathways, caused by intraoperative retraction of these structures, was the pathophysiology of the syndrome (116). This hypothesis could also account for the delayed onset after surgery and partially transient nature of the syndrome, reflecting the time interval for development and regression of edema. The development of delayed edema by this same mechanism, but in the cerebellum itself, was also hypothesized by Ozek and colleagues, who recommended avoidance of constant retraction of bilateral cerebellar structures as a way to prevent the syndrome (76). A retrospective study demonstrated a statistically significant greater degree of preoperative pons compression and greater increase in postoperative pons diameter on MRI in 13 of 51 children who developed cerebellar mutism syndrome after resection of a posterior fossa midline tumor (64). The authors postulated that the greater compression may make white matter tracts in brainstem more vulnerable to injury after surgical manipulation, and that the relatively sudden release of this greater force at surgery may increase predisposition to axonal distortion and injury.

Other mechanisms. Early studies noted that larger posterior fossa tumors were associated with cerebellar mutism syndrome (37). Contrary to this, in several large series, tumor size was not a risk factor for the development of cerebellar mutism syndrome (84; 108; 100; 90; 17; 98).

Tumor presentation with hydrocephalus has been proposed as another mechanism of cerebellar mutism syndrome development. In a series of 134 patients with cerebellar mutism syndrome, 42 (31%) required placement of a ventriculoperitoneal shunt (37). Hydrocephalus that required CSF diversion appeared to be a significant factor in a small series in which five of five patients with cerebellar mutism syndrome, but only four of 10 without cerebellar mutism syndrome required a ventriculoperitoneal shunt (109). In a case of 60 pediatric patients undergoing posterior fossa tumor resection, both hydrocephalus at presentation and in the postoperative period were significantly associated with the development of cerebellar mutism syndrome (96).

A prospective Italian study found that abnormal language prior to surgery was a strong risk factor for the development of cerebellar mutism (26). All seven of 34 children who developed cerebellar mutism (20%) after posterior fossa tumor surgery had preoperative language impairment; no child with normal preoperative language developed mutism.

Postoperative vasospasm causing ischemia also has been proposed as a mechanism of injury that could account for the period of latency before the onset of symptoms (32; 70). On a SPECT scan, hypoperfusion was detected in the cerebellar hemisphere in a patient with mutism and then normalized after resolution of the mutism (30). The bilateral edema in middle cerebellar peduncles in many of the patients with cerebellar mutism syndrome was thought to be consistent with ischemia from vasospasm in these structures as a pathophysiologic mechanism of cerebellar mutism syndrome (84). Sagiuchi reported decreased blood flow in both cerebellar hemispheres (as well as in both thalami and frontal lobes) on SPECT scan after resection of a right cerebellar hemispheric medulloblastoma. This normalized after improvement of the patient’s mutism, providing support for a mechanism of delayed edema or ischemia in the cerebellum as a cause of cerebellar mutism syndrome (91). The hypoperfusion in the thalami and frontal lobes provides support for cerebellar connections to these structures, which are known to undergo changes in perfusion and metabolism with changes in the metabolism of the contralateral cerebellar hemisphere (91).

Epidemiology

Cerebellar mutism syndrome occurs most often following the resection of a large midline posterior fossa tumor. A variable incidence of the syndrome, ranging from 2% to 29%, has been reported in the literature (20; 84; 56; 48; 15; 27; 100; 37; 90; 57; 96). There is no known cultural or racial predilection to developing the syndrome. There is an ongoing multicenter prospective study in Europe that in addition to identifying risk factors, comorbidities, and differences in treatments, will also be exploring the role of genomic variants on the development, severity, and recovery from cerebellar mutism (114).

Although less common, cerebellar mutism syndrome has also occurred in adults and in settings other than tumor resection, including after traumatic or surgical vertebrobasilar injury, in the context of cerebellar or brainstem hemorrhage, and after resection of intrinsic brainstem tumors (25; 118; 94; 14; 23; 28; 31; 50; 56; 72; 101; 68; 51; 47), and with parainflammatory cerebellitis and acute disseminated encephalomyelitis (65; 79; 80). A prospective study of cerebellar mutism following posterior fossa surgery in 59 operations in adults did not find anyone with postoperative cerebellar mutism, though 16% had development or worsening of speech or motor complication (115).

Prevention

Based on the hypothesis that incision or removal of the cerebellar vermis was a cause of cerebellar mutism syndrome, it has been proposed that an approach that avoided splitting the vermis could avoid mutism (20; 52; El–Bahy 2005). However, such an approach does not appear to prevent cerebellar mutism syndrome with any consistency (23; 84; 100; 119). The avoidance of prolonged intraoperative retraction was proposed as a means of preventing cerebellar mutism syndrome in view of the hypothesis that this might be a factor contributing to cerebellar mutism syndrome by producing delayed postoperative edema or ischemia in cerebellar or pericerebellar structures (116; 76). But avoidance of prolonged intraoperative retraction has not been shown to be effective in preventing cerebellar mutism syndrome. Better understanding of the pathophysiology of postoperative mutism is needed to reduce the incidence of this postoperative complication in the future.

A multicenter international retrospective study evaluated modifiable factors associated with the development of cerebellar mutism in children with resection of posterior fossa tumors; however, no significant associations were seen with preresection surgical hydrocephalus treatment, prone position, ultrasonic aspirator use, external ventricular drain use, cerebellar vermis sparing approach, complete or near total resection, or treating center with postoperative cerebellar mutism (88). Another group found along with brainstem invasion and/or compression that an increase of 0.5 degrees Celsius in mean body temperature in the first 4 postoperative days resulted in an almost 5-fold increased odds ratio of developing cerebellar mutism (85).

An imaging-based preoperative risk scoring system to stratify patients in terms of postoperative cerebellar mutism risk has been developed (61). Using the six identified predictors of primary location, bilateral middle cerebellar peduncle involvement, dentate nucleus invasion, and age at imaging of more than 12.4 years, patients were risk stratified into low, intermediate, and high risk of cerebellar mutism, with 88.8% accuracy. This process allows for preoperative risk stratification during surgical consent. Additionally, use of intraoperative imaging significantly reduced cerebellar mutism syndrome risk (OR 0.36, 95% CI 0.18–0.72) in a large metaanalysis of 28 studies (83).

Differential diagnosis

The differential diagnosis of decreased speech or mutism following posterior fossa surgery includes the inability to speak because of cranial nerve palsies. These would include deficits of facial nerve function with decreased lip mobility, deficits of bulbar cranial nerves with attendant oropharyngeal dysfunction, and deficits of hypoglossal nerve function with decreased tongue mobility. The absence of speech in children after posterior fossa surgery conceivably could be unrelated to organic injury to brain structures and instead could represent a psychological reaction in the child to the stress of the operation. This is a phenomenon well known in psychiatry as “elective mutism,” and has been described in various psychologically stressful settings (07). Indeed, it has been hypothesized that the mechanism of the cerebellar mutism syndrome is actually a functional disturbance reflecting a sense of betrayal and anger in children whose parents have allowed them to be subjected to a difficult and painful operation (32). However, the cerebellar mutism syndrome, as currently described and increasingly identified, has such distinctive and stereotypical features that it seems improbable to have an exclusively psychological basis. Moreover, when the fully realized mutism syndrome is present, it is unlikely not to be recognized as such.

Diagnostic workup

The diagnosis of cerebellar mutism syndrome is made on the basis of the clinical constellation of signs and symptoms described in the clinical manifestations section of this article. Abbreviated speech and language evaluations to document the degree of language deficit at the onset and then at intervals during recovery from the mutism could be useful for prognosis. There are currently no established laboratory or brain imaging evaluations to confirm the diagnosis, although certain MRI abnormalities, such as edema in cerebellar peduncles or brainstem, have been noted in some cases of cerebellar mutism syndrome (109; 84).

Management

The comprehensive characterization of the neurologic impairments seen in cerebellar mutism syndrome may include severe communication deficits of expressive and sometimes receptive language with evolution to dystaxic speech, severe global cerebellar dysfunction, emotional lability, and sometimes inattention, oromotor dyspraxia, and loss of bowel and bladder control. This rather global picture of neurologic dysfunction frequently necessitates an intensive program of rehabilitation that includes speech, occupational, and physical therapy for patients recovering from cerebellar mutism syndrome. One reported case described a child who developed cerebellar mutism syndrome with complete absence of speech for 2 weeks after resection of a posterior fossa tumor; but the child was abruptly able to sing along with a musical video, which seemed to trigger a rapid and sustained overall speech recovery (77). The nonbenzodiazepine hypnotic agent, zolpidem, is primarily used as a sedative, but there is some evidence for its efficacy in alleviating mutism and akinesia in other neurologic and psychiatric disorders. Zolpidem was reported to have increased arousal and accelerated recovery of speech via an uncertain mechanism in a child with postoperative cerebellar mutism (99). Another case report reported the resolution and recurrence of cerebellar mutism correlating with the administration and clearance of midazolam in one patient; the authors performed SPECT analysis on this patient’s brain and also demonstrated initially reduced blood flow to cerebral cortex that resolved on follow-up (71).

There is little experience with pharmacological management of the symptoms of cerebellar mutism syndrome. High-dose steroids were administered to several patients with cerebellar mutism syndrome with a thought to preventing the edema hypothesized as a cause of the syndrome, either from intraoperative retraction of cerebellar structures or from postoperative vasospasm; they were ineffective in reversing the symptoms (84). However, two children with postoperative cerebellar mutism syndrome were reported to have had accelerated improvement after treatment with fluoxetine, a serotonin-reuptake inhibitor antidepressant medication. This idea for therapy was based on the hypothesis that speech and language impairment in childhood autism is related to decreased serotonin in the cerebral cortex, resulting from interruption of the dentato-thalamo-cortical pathways. A subsequent case report of a child with cerebellar mutism responding to fluoxetine was published in 2012 (04). A patient who developed cerebellar mutism syndrome after resection of a low-grade fourth ventricular neuronal-glial tumor was reported to have improved dramatically with the administration of bromocriptine. This was hypothesized to have restored possible decreased brainstem dopaminergic outflow related to the mutism (01).

Outcomes

Despite the age of injury and the number of years after surgery, most patients were found to have made their most substantial improvements within the first year of cerebellar mutism (45; 105). However, most patients with postoperative cerebellar mutism go on to have some speech difficulties (103). Patients with tumors requiring only surgical resection and without brainstem invasion may have a favorable prognosis in one study (105). The same group found that patients presenting at diagnosis with associated combined procedural memory and defective neurocognitive function tend to have a more severe cerebellar mutism course and are less prone to complete recovery.

Additionally, the emotional toll that these deficits may cause or may be a direct consequence of cerebellar injury needs to be monitored with referral to a psychologist/psychiatrist, as needed. Patients should be referred for rehabilitation services focusing on speech and any other associated cerebellar/cranial nerve findings along with neurocognitive assessment and rehabilitation. These patients will likely need individualized education plans at school.

Special considerations

Pregnancy

Fertility. There would be no expected influence of cerebellar mutism syndrome, per se, on fertility. Infertility incidence is increased in patients with medulloblastoma, the most common setting in which cerebellar mutism syndrome occurs, related to treatment with irradiation and chemotherapy.

Pregnancy complications. The cerebellar mutism syndrome has no particular relevance during pregnancy.

Anesthesia

Anesthesia seems unlikely to be complicated by cerebellar mutism syndrome, unless there were to be uncommonly associated cranial nerve deficits, which could result in aspiration from loss of airway protection because of bulbar dysfunction.