Cerebellar Mutism

Loice Swisher, M.D.
Cerebellar mutism was first reported in 1979 by Hirsh after a posterior fossa tumor resection. In the past, cerebellar mutism was thought to be an uncommon problem. However, there have been increasing numbers of case reports and literature reviews that indicate that cerebellar mutism may be significantly more common than previously thought. The reason for this increase of reports is unclear but may be due to neurosurgical advances that allow more aggressive tumor resection.

The complication of cerebellar mutism, also known as syndrome of mutism of subsequent dysarthria or posterior fossa syndrome with cerebellar mutism, is rarely mentioned to parents during the consent for surgery of a posterior fossa tumor. When it occurs parents are often scared and confused by this unexpected new problem their child is experiencing. Frustration may be heightened by the lack of information written at a level for parents at a time when they have been thrust into probably the worst nightmare of their life. The questions are many- How did this happen? Will it get better? How long will it take to improve? What is the natural course of this problem? Will my child talk normally again? Can I talk to any other parent who has been dealt this hand? This article tries to address some of these parental concerns.

The basics:

Definition: This is a symptom complex including decreased or absent speech, irritability, hypotonia (low muscle tone), ataxia (unsteadiness and deceased coordination) and the inability to coordinate voluntary movements most commonly seen after surgery in the posterior fossa region of the brain. Mutism is considered a severe incoordination of the volitional motor aspects of speech.

Onset of Mutism: The mutism may be immediate or delayed. Virtually all cases of mutism will occur within the first week of surgery- 50% within the first two days. It is not uncommon for the child to speak a few words after surgery and then the next day unable to produce words.

Length of Mutism: Mutism has been reported to last as short of six days and as long as 52 months. There have been no cases reported where a child with cerebellar mutism did not get return of functional speech.

Incidence: Review articles have published the statistic that approximately 8% of children undergoing posterior fossa surgery for tumor will develop a degree of cerebellar mutism.

Factors associated with the development of mutism:

  • Posterior fossa surgery for tumor- Overwhelmingly mutism of cerebellar origin has been reported with surgical intervention in the posterior fossa for tumor. However, there are other etiologies reported in the literature including posterior fossa trauma., cerebellitis (inflammation of the cerebellum), cerebellar hemorrhage, embolic events, and AVM's.
  • Children- Most cases involve children. Although there have been reports of mutism in patients in there eighth decade of life.
  • Midline tumor location
  • Cerebellar vermal incision
  • Large or very large tumor size- A size greater than 5cm with medulloblastomas appears to increase the risk.
  • Medulloblastoma- This tumor type appears to be increasingly associated with mutism although it has also been reported to occur with ependymomas, choroid plexus tumors, astrocytomas and rhabdoid tumors.

Pathophysiology: The exact reason for cerebellar mutism has not been agreed upon. Recent reports believe that there is focal decreased cerebral and cerebellar blood blow leading to decreased cell functioning in particular areas. Specifically, decreased blood flow to the dentate-thalami-cortical pathway may cause these cells not to function as well. Single photon emission computerized tomography (SPECT) studies have lead support to this theory. It is not thought to be an emotional problem where the child is unwilling or too angry or depressed to talk.

The speech: Speech always returns with cerebellar mutism. Rarely, some children have there speech come back almost all at one time. For example, one day few sounds and then next "one, two, three, four I declare a thumb war". More commonly the communication comes back more slowly with more spontaneous sounds first (laughing and crying) followed by sounds (such as fffff). If a child had not been able to communicate in a nonverbal way due to severe hypotonia (such as with head nods, gestures, or communications boards), this type of nonverbal communication usually precedes speech.

The speech is virtually always becomes functional for communication, however it may not be the same as before surgery. The speech may be hypernasal, monotone, high pitched (helium voice), slower and sparser. The child may have difficulty initiating an answer and speech less than before. The stress patterns of speech (prosody) may also be off.

Some children will never return to a normal voice and are left with residual deficits in prosody (the melody or normal stress patterns of speech), initiation and vocal quality. It should be noted that children undergoing posterior fossa surgery may have speech disturbances of a similar nature even without mutism. This is often referred to as cerebellar speech.

Intervention: Children with cerebellar mutism are usually seen by a speech-language pathologist whose job may include-

  • Assisting in devising a form of nonverbal communication
  • Explaining the usual course of cerebellar mutism and what to expect in the recovery. For example, asking a child to speak when they do not have the motor ability just leads to frustration for both the parents and children.
  • Practicing tongue and lip movements before speech returns
  • Practicing and suggesting volitional blowing tasks (Harmonicas, recorders, party favors, blowing bubbles are some of the most common. Straw games such as blowing the paper off a straw, blowing bubbles into liquid, and blowing cottonballs off a table are favorites among many kids)
  • Assessing speech and language skills
  • Giving suggestions to parents to aid in recovery of function. Examples include:
  • singing or taping songs at a very slow speed as a way for the child to practice the intonation differences and other speech skills.
  • Starting a nursery rhyme and having the child complete it.
  • Giving a picture and having the child tell a story
  • Having the child do something and then explain what they did

 

Other problems:

  • Posterior fossa syndrome- This refers to the irritability, hypotonia, and ataxia which may or may not be accompanied by mutism. Some of these children will also suffer from a hemiparesis as well. Rehabilitative services, including physical therapy and occupational therapy, are usually a given. Cerbellar mutism has not been reported without the other finding of posterior fossa syndrome in the face of tumor resection
  • Feeding difficulties- Some children has such severe problems with the coordination of oro-facial movements that they are unable to chew and swallow. Return of voluntary movements of the tongue (to stick it out and move to side to side) precede the ability to eat. Children who have been affected this severely often need tube feeding, especially when radiation therapy and chemotherapy is given at the same time as the child is trying to regain the ability to eat. The decreased appetite, nausea and vomiting may not allow the child who is just regaining these skills to get enough nutrition on their own.
  • Cortical blindness-like syndrome- Very uncommonly a child will develop a problem in which the eyes can see but the brain in not interpreting images. Thus, the patient is essentially blind since the brain is not processing visual input. This is frequently referred to as cortical blindness. This may be more common than reported as the vision usually returns before the mutism improves. Unless it is checked for or the child asked at a later time, this may not be noted.
  • Neuro-cognitive Issues- Some clinicians believe that children who have experienced cerebellar mutism may also experience greater neuro-cognitive deficits. This question has not been answered but investigations are now underway in some institutions.

Recurrence of Cerebellar Mutism:

There are no reports in the literature of a recurrence of cerebellar mutism with subsequent surgeries.

Other resources: Other resources available to parents include the Cerebellar Mutism/Posterior Fossa Listserve at http://groups.yahoo.com/group/cerebellarmutism or the American Speech-language-Hearing Association at www.asha.org. Reprinted from a Childhood Brain Tumor Foundation newsletter, author Loice Swisher.

This article was written for the Childhood Brain Tumor Foundation, Germantown, Maryland.

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