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Cerebellar ataxia
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Cerebellar ataxia can be either acute or chronic. Chronic ataxia is sometimes referred to as cerebellitis, and is seen in people with multiple sclerosis (MS). Cerebellar ataxia is a form of ataxia that originates from abnormalities such as inflammation in the occipital and temporal lobes of the cerebellum. The cerebellum is found at the back of the brain, below the cerebrum and close to the brainstem, and is responsible for motor control, muscle movement, and motor learning. This type of ataxia is most commonly known for causing a loss of balance and coordination, but it can lead to other symptoms such as fatigue, cognitive issues and visual abnormalities.
Symptoms
Cerebellar ataxia can lead to a number of symptoms, such as:
- a wide and unsteady gait when walking
- poor hand-eye coordination
- tremors
- slow and imprecise speech
- a lack of sensory capability
- cognitive impairment
- diplopia (double vision)
- nystagmus (involuntary eye movements)
- difficulties when swallowing
- hypotonia (floppiness)
- asynergy (lack of coordination between organs and body parts)
- dyschronometria (difficulty in estimating time passing)
- dysdiadochokinesia (inability to perform quick and alternating movements)
Symptoms can vary from person to person, depending on how the cerebellum has been affected.
Causes
Cerebellar ataxia itself is merely a symptom and does not simply have one clear cause. In some instances, it is a result of an underlying condition or problem which may be treated, such as hyperthyroidism, alcoholism, stroke and MS. In other instances, it is of genetic origin, caused by inherited mutations. However, many cases of cerebellar ataxia are idiopathic, meaning that cerebellar degeneration simply occurs with no obvious cause.
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Genetic factors
Sometimes cerebellar ataxia can have a genetic origin. This is known as autosomal dominant cerebellar ataxia, and results from inherited mutations in the form of triplet repeat expansion, in genes SCA1 to SCA37. Triplet repeat expansion refers to a repeated segment of DNA, known as a trinucleotide repeat, that is unstable and interferes with protein functioning. The mutations are dominant and hence can be transmitted easily. This form of ataxia is registered with the National Organization for Rare Disorders (NORD) and can also be called dentato-rubro-pallido-luysian atrophy and familial progressive cerebellar ataxia.
Alcoholism
One common cause of cerebellar ataxia is alcoholism. When abused for long periods of time, alcohol directly damages the cerebellum, leading to a loss of proper functioning. It also damages subcortical white matter, the connective myelinated fiber tracts of the cerebral cortex, and other parts of the central nervous system. Damage to all of these areas results in ataxia as the systems controlling motor skill become impaired.
Hypothyroidism
Another underlying cause of cerebellar ataxia is hypothyroidism. This occurs when the thyroid gland, at the base of the neck, becomes underactive, producing too little hormone. Thyroid hormones are called triiodothyronine (T3) and thyroxine (T4) which control energy use and metabolism. Too little of them can lead to a lethargy, weight gain, and weakness, amongst other symptoms. The changes in metabolism caused by hypothyroidism lead to cerebellar dysfunction and degeneration. Additionally, hypothyroidism can lead to an increase in antithyroid antibodies, which is thought to lead to cerebellar degeneration.
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Infection
Sometimes cerebellar ataxia can result from infection, which causes inflammation in the cerebellum, impairing its ability to function normally. Ataxia is more commonly caused by viral infections like chickenpox, but can be caused by bacterial infections too, such as Lyme disease. This results in a sudden, or acute, attack of ataxia, in a previously healthy patient, and is much more common in children that adults. This kind of cerebellar ataxia is often referred to as acute cerebellar ataxia (ACA), or acute post-infectious ataxia (APCA).
Head trauma and bleeding
Cerebellar ataxia can also be a result of trauma to the head, or bleeding on the brain. Unsurprisingly, head traumas can lead to inflammation of the cerebellum, as well direct damage and injury. This impairs the normal functioning of the cerebellum, leading to cerebellar ataxia. Bleeding into the cerebellum can also cause ataxia.
Tumours
Both cancerous and noncancerous tumours can lead to cerebellar ataxia by affecting the structure of the cerebellum, by placing pressure on it, or causing it to become inflamed.
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Cerebral palsy
Cerebral palsy is a condition that affects movement, and is a result of brain injury either before, during, or shortly after birth. If the injury damages the cerebellum, cerebral ataxia can occur. Damage to the cerebellum before, during, and after birth can result from:
- infection in the womb
- loss of oxygen from breaching during birth or placental failure
- head traumas during or after birth
- brain hemorrhages caused by fetal stroke
Idiopathic cerebellar ataxia
Some cerebellar ataxia has no clear cause, and is the result of cerebellar degeneration that has no genetic factor. This type of ataxia is known as idiopathic late onset cerebellar ataxia (ILOCA). Patients with idiopathic cerebellar ataxia show variation in the physical changes in their cerebellum. Some exhibit cerebellar cortical atrophy, which involves degeneration of Purkinje cells in the cerebellar cortex and loss of facultative retrograde cells in the inferior olive (or inferior olivary nucleus). This is the largest nucleus of the olivary body of the medulla oblongata, which inputs to the cerebellum and is important in motor control.
Idiopathic cerebellar ataxia can also result from olivopontocerebellar atrophy, which are transneuronal changes in the cerebellar hemispheres that originate in the olivary and pontine nuclei (in the pons), and result in cerebellar shrinkage. Although sometimes inherited, this form of ataxia often occurs idiopathically with no obvious cause. Ataxia can also result from unexplained changes in the spinal cord, thalamus, cerebral cortex, and basal ganglia of the central nervous system.
Diagnosis
One way to diagnose ataxia is through genetic analysis of blood samples and assessing familial medical histories. If a pattern of cerebellar ataxia is present in the family tree, then it is likely that the patient is suffering from inherited autosomal dominant ataxia. Diagnosis can also be conducted using MRI scanning, to assess damage or inflammation in the brain, and cerebellum in particular. Ataxia can also be diagnosed by determining the patient’s history, looking for signs of conditions such alcoholism or hypothyroidism, and assessing the presence and severity of ataxia symptoms.
Treatment
In cases where cerebral ataxia is a result of an underlying condition, it can generally be treated by treating that condition. For example, alcoholics experiencing ataxia can reverse their symptoms by abstaining from drinking alcohol. Likewise, if hypothyroidism is causing ataxia, then treatment of this condition with hormone therapy should remove the ataxia symptoms. In terms of infection, treating the infection should lead to recovery from ataxia. Similarly, treatment of brain tumours, bleeding and head injuries can also lead to recovery.
However, there is currently no cure for ataxia itself. In patients with idiopathic, genetic, or cerebral palsy-caused cerebellar ataxia, there is no obvious cure. Although certain therapies are available to reduce its intensity, such as: speech therapy, occupational therapy, and physiotherapy.
Highlights
Cerebellar ataxia is a form of ataxia that originates from abnormalities such as inflammation in the occipital and temporal lobes of the cerebellum.
Cerebellar ataxia can lead to a number of symptoms, such as:
- a wide and unsteady gait when walking
- poor hand-eye coordination
- tremors
- slow and imprecise speech
- a lack of sensory capability
- cognitive impairment
- diplopia (double vision)
- nystagmus (involuntary eye movements)
- difficulties when swallowing
- hypotonia (floppiness)
- asynergy (lack of coordination between organs and body parts)
- dyschronometria (difficulty in estimating time passing)
- dysdiadochokinesia (inability to perform quick and alternating movements)
This condition itself is merely a symptom and does not simply have one clear cause. Possible causes of cerebellar ataxia include:
- genetic
- alcoholism
- hypothyroidism
- infection
- head trauma and bleeding
- tumours
- cerebral palsy
It is diagnosed by performing genetic analysis, taking the family and medical histories, and MRI scanning. Treatment is only symptomatic and for the cause, as there is no cure for cerebellar ataxia itself.
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