What is Ataxia? Ataxia and Cognitive Problems

From the National Ataxia Foundation, a great handout:

FREQUENTLY ASKED QUESTIONS ABOUT...

Cognition and Emotion in Cerebellar Disorders

Are problems in the areas of cognition and emotion related to the cerebellar damage in ataxia?

Yes, they can be. The cerebellum has long been known to be important for motor control, and people with ataxic disorders experience motor difficulties including wide-based and unsteady gait (ataxia), incoordination of the arms and legs, slurred speech, and eye movement abnormalities. We now know that the cerebellum, like the cerebral cortex, has some parts that are critical for movement, and other parts that play a role in cognition and emotion. The motor cerebellum is linked with the motor cortex that governs movements; whereas non-motor regions of the cerebellum are linked with cerebral cortical “association” areas important for thought, reasoning, motivation, memory and feelings. Damage to the non-motor cerebellum disrupts these cerebellar links with cerebral cortical thinking areas, and can lead to difficulties in intellectual functions and to changes in mood and personality. Ataxic disorders may also produce neurodegeneration in parts of the cerebral cortex important for intellect, another reason why ataxia patients may experience problems with these functions.

What types of psychological problems may be caused by cerebellar damage or disorders?
The cerebellar cognitive affective syndrome is the set of problems that arises when the non-motor cerebellum is damaged. It includes impairments in executive function, visual-spatial analysis and selected deficits in language skills as well as changes in personality and behavior. There may be difficulties with multi-tasking,

planning, and organizing. Tasks of every day life that require intellectual flexibility and that were previously performed automatically may require conscious effort and new strategies. There may de difficulty expressing thoughts logically and coherently, and memory problems, particularly with working, or scratch pad, memory. Mood changes include depression, apathy, irritability and limited frustration tolerance. Psychosocial interaction may be impaired, particularly in children with cerebellar damage. Dementia is uncommon in cerebellar disease, but can be a problem in those ataxic disorders that affect widespread areas of the cerebral cortex. The role of the cerebellum in dyslexia, attention deficit hyperactivity disorder, autism spectrum disorders, schizophrenia, developmental delay and panic disorder, is under active investigation.

Why is this important for the ataxia patient?
Cerebellar patients and families generally find it helpful to know that cognitive and psychiatric problems may occur as a direct result of the illness. These challenges, beyond motor control, are not “in their head”, rather, they are in their brain. These difficulties are not the fault of the affected individual, family members or health care providers. It is also useful to know that the stress of chronic illness and the social changes that result may place additional burdens on patients and families. Recognizing the brain basis of these mental and mood changes, along with challenging social and psychological issues that come with the illness, is the essential first step leading to treatment. Parents of children with developmental delay from cerebellar disease may have to deal with many special psychosocial and intellectual challenges, even if there is only minimal or no ataxia. 

National Ataxia Foundation
2600 Fernbrook Lane, Suite 119 • Minneapolis, MN 55447-4752
Phone: (763) 553-0020 • Fax: (763) 553-0167 Email: naf@ataxia.org • Website: www.ataxia.org 

PDF handout here

http://www.ataxia.org/events/2013-Presentations/Saturday/Schmahmann_2013.pdf

Why do serotonergic medications help some ataxias?

Why do serotonergic medications help some ataxias?

Neuroscientist. 2001 Jun;7(3):207-19.

Serotonergic neuromodulation in the cerebellar cortex: cellular, synaptic, and molecular basis.

Dieudonné S1.

Author information

Abstract

    The cerebellum, like most sensorimotor areas of the brain, receives a serotonergic innervation from neurons of the reticular formation. It is well established that local application of serotonin modulates the firing rate of cerebellar Purkinje cells in vivo and in vitro, but the mechanisms by which serotonin affects the cerebellar function are still poorly understood. Whereas interactions between serotonin, glutamate, and GABA have been reported to increase or decrease the firing frequency of Purkinje cells, there is little evidence for a modulation of excitatory and inhibitory synapses by serotonin in the cerebellar cortex. 

     Changes in the intrinsic electrical properties of Purkinje cells upon application of serotonin have also been reported, but their impact on Purkinje cell firing is unclear. The recent finding that serotonin specifically modulates the activity of Lugaro cells, a class of inhibitory interneurons of the cerebellar cortex, offers new insights on the action of this neuromodulator. The peculiar axonal projection and specific interneuronal targets of the Lugaro cells suggest that the action of serotonin might occur upstream of Purkinje cells through a resetting of the computational properties of the cerebellar cortex. 

       Understanding the mechanisms of the serotonergic modulation of the cerebellar cortex is of clinical relevance, as abnormal serotonin metabolism has been observed in animal models and pathological cases of motor disorders involving the cerebellum, and as chronic intravenous administration of L-5-hydroxytryptophan (5-HTP), a precursor of serotonin, was the first treatment shown to improve significantly cerebellar symptoms.

Can J Neurol Sci. 1993 May;20 Suppl 3:S78-82.

The cerebellar serotoninergic system and its possible involvement in cerebellar ataxia.

Trouillas P1.

Author information

Abstract

A review concerning the characteristics of the cerebellar serotoninergic system is presented. In rat, cat and oppossum, the perikarya of origin are located in the brain stem raphe nuclei and in other brainstem structures. The projections to the cerebellar layers and deep nuclei include synaptic connections, but also non synaptic terminals, especially in a diffuse cortical plexus. Serotoninergic receptors have been described: 5-HT1B in the molecular layer and 5-HT2 in the inferior olive. Serotonin exerts neurophysiological effects on several target cells, directly or indirectly, presynaptically or postsynaptically. A modulatory effect on Purkinje cells is well documented. In thiamine deprived animals, a specific serotoninergic cerebellar syndrome includes a selective degeneration of the serotoninergic cerebellar system, an increase of the 5-HIAA cerebellar values and an exaggerated serotoninergic turnover. In human heredoataxias (Friedreich's ataxia and cerebellar cortical atrophy), serotoninergic disturbances have been observed in the CSF, including low 5-HIAA values and an increased serotoninergic turnover. Therapeutic results have been obtained with L-5-HTP, a precursor of serotonin, in several conditions presenting cerebellar ataxia. L-5-HTP resistance of olivopontocerebellar atrophies may be explained by the destruction of serotonin-sensitive target cells, especially Purkinje cells.

How common is ataxia in childhood?

Neurology. 2013 Nov 27

Prevalence of ataxia in children: A systematic review.

Musselman KE, Stoyanov CT, Marasigan R, Jenkins ME, Konczak J, Morton SM, Bastian AJ.

Author information

Abstract

OBJECTIVE:

To estimate the prevalence of childhood ataxia resulting from both genetic and acquired causes.

METHODS:

A systematic review was conducted following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) statement. Five databases were searched for articles reporting a frequency measure (e.g., prevalence, incidence) of ataxia in children. Included articles were first grouped according to the World Health Organization (WHO) regions and subsequently classified according to etiology (genetic, acquired, or mixed). Each article was assessed for its risk of bias on the domains of sampling, measurement, and analysis. Incidence values were converted to prevalence estimates whenever possible. European prevalence estimates for different etiologies of ataxia were summed to gauge the overall prevalence of childhood ataxia.

RESULTS:

One hundred fifteen articles were included in the review. More than 50% of the data originated from the Europe WHO region. Data from this region also showed the least susceptibility to bias. Little data were available for Africa and Southeast Asia. The prevalence of acquired ataxias was found to vary more greatly across regions than the genetic ataxias. Ataxic cerebral palsy was found to be a significant contributor to the overall prevalence of childhood ataxia across WHO regions. The prevalence of childhood ataxias in Europe was estimated to be ∼26/100,000 children and likely reflects a minimum prevalence worldwide.

CONCLUSIONS:

The findings show that ataxia is a common childhood motor disorder with a higher prevalence than previously assumed. More research concerning the epidemiology, assessment, and treatment of childhood ataxia is warranted.