What is cerebellar ataxia?

Cerebellar ataxia refers to a group of conditions marked by impaired muscle coordination (ataxia) or awkward movements due to the cerebellum's damage, the brain region that regulates balance and movement. Pierre Marie identified it in 1893. Ataxia symptoms appear on the same side of the body as the cerebellar damage. Types of ataxia uniquely impact muscle coordination, such as dysmetria, dysdiadochokinesia, and asynergia. Damage to the cerebellum can cause abnormal eye movements, action tremor, speech disturbance, balance deficits, and gait ataxia. Cerebellar ataxia can be inherited or acquired through stroke, diseases, or tumors. Rehabilitation training, including physical, occupational, and speech therapy, can help improve physical strength and mobility, communication, and swallowing, though treatments that slow the cerebellum's degeneration are limited.

Where in the brain does cerebellar ataxia start?

Cerebellar ataxia arises from damage to the cerebellum , the area of the brain that integrates sensory input with muscular responses. Damage to the oldest part of the cerebellum, which lies deep in the midline, can cause difficulty in maintaining an upright posture. Lesions in the vermis and anterior lobes particularly affect gait, while damage to the lateral lobes may result in incoordination of the limbs. Ataxia symptoms manifest on the same side of the body as the cerebellar damage. Spinocerebellar degenerations, which are inherited disorders, can also cause ataxia.

How does cerebellar ataxia affect body movement and balance?

Cerebellar ataxia results from damage to the cerebellum, impacting muscle coordination and balance. This condition manifests as various impairments, including dysmetria (inability to judge movement distance) and dysdiadochokinesia (difficulty with rapid, alternating movements). Balance deficits and gait ataxia are common, leading to postural sway, abnormal trunk movements, and a clumsy, wide-based gait. Damage to specific parts of the cerebellum affects posture, gait, and limb coordination. While treatments are limited, rehabilitation therapies like physical and speech therapy can improve mobility and communication.

What are some common causes of cerebellar ataxia?

Cerebellar ataxia, marked by impaired muscle coordination, arises from various factors affecting the cerebellum. It can be inherited or acquired. Inherited forms, like Friedreich ataxia (FXN gene mutations), can manifest at birth or later and follow autosomal recessive or dominant patterns. Acquired cerebellar ataxia often stems from direct damage to the cerebellum or its pathways, typically from stroke, diseases, or tumors. Other causes include chronic alcoholism, certain medications, vitamin deficiencies, hypothyroidism, and inherited metabolic defects. Inflammatory diseases like abscesses and cerebellitis can also affect the cerebellum.

How do doctors diagnose cerebellar ataxia?

Cerebellar ataxia is characterized by a failure of muscle coordination resulting from atrophy or disease of the cerebellum , the region of the brain that organizes sensory information related to balance and locomotion. Doctors can assess cerebellar function through physical examinations that include an evaluation of cranial nerves, motor systems, and sensory systems. To assess cerebellar function in the limbs, doctors may ask the subject to touch their nose and the physician’s finger, run one heel down the opposite shin, or perform piano-playing movements with the fingers. The nature and pattern of the symptoms and physical signs of neurological disease allow inferences to be drawn about the sites of the lesions causing them.

What changes happen in the cerebellum during cerebellar ataxia?

Cerebellar ataxia is characterized by a failure of muscle coordination, or ataxia, resulting from atrophy or disease of the cerebellum . Damage to the cerebellum can manifest differently depending on the location of the damage. Damage to the oldest part of the cerebellum results in difficulty maintaining an upright posture and nystagmus . Lesions in the vermis and anterior lobes particularly affect gait. Damage to the lateral lobes may cause ataxia of the limbs, leading to awkward and impaired movements, possibly accompanied by a severe tremor. Other issues include abnormal eye movements, action tremor, speech disturbance, balance deficits, and gait ataxia.

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Causes of cerebellar ataxia

Cerebellar ataxia can be inherited or acquired. Inherited forms may be present at birth or manifest later in life and may be autosomal recessive (two copies of the defective gene are needed to cause disease) or autosomal dominant (one copy of the defective gene is needed). One of the most common inherited forms of cerebellar ataxia is Friedich ataxia, which is caused by mutations in a gene known as FXN. Acquired cerebellar ataxia can result from damage to the cerebellum itself or from damage to pathways to and from the cerebellum. Acquired damage typically is caused by stroke, certain diseases, or a tumour.

Manifestations of ataxia and other symptoms

If there is damage to only one side of the cerebellum, the resulting symptoms of ataxia manifest on the same side of the body as the damage (e.g., right cerebellar damage causes right-sided ataxia). There are many types of ataxia, and each uniquely affects muscle coordination. Dysmetria, for example, is a form of ataxia characterized by an inability to make a movement of the appropriate distance, such as touching a heel to a shin or touching a finger to a target object. In such tests, persons with dysmetria undershoot or overshoot the desired target. Individuals with cerebellar damage tend to overshoot when they move more rapidly and undershoot when they move more slowly, wishing to be accurate. Dysdiadochokinesia is an inability to make rapid alternating muscle movements, such as those required when tapping a foot. The condition appears to reflect abnormal control of opposing muscles. Asynergia refers to an inability to combine the various components of a movement to create fluid motion. In asynergia, movements appear clumsy, jerky, and abnormal. Those with cerebellar damage may also show signs of hypotonia, or abnormally decreased muscle tone (e.g., floppier motions). Hypotonia, when present, is apparent only during the early phase of cerebellar disease.

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Damage to the cerebellum can cause a variety of other problems, including abnormal eye movements, such as nystagmus, which is an involuntary jumping movement of the eye. Another common finding is action tremor (involuntary shaking during any movement) or intention tremor (involuntary shaking during purposeful movement). In both forms of tremor, shaking disappears when the muscles are at rest. Cerebellar damage can also cause a speech disturbance called dysarthria, in which words become slurred and difficult to understand. Dysarthria tends to be a major problem and frustration for individuals affected by cerebellar ataxia, as it makes communication difficult. Some individuals affected by dysarthria also experience difficulty in swallowing.

Possibly the most common and disabling impairments of cerebellar damage are balance deficits and gait ataxia. Balance abnormalities are characterized by increased postural sway, either excessive or diminished responses to perturbations, poor control of equilibrium during motions of other body parts, and abnormal oscillations of the trunk (titubation). Gait ataxia, or walking incoordination, is often described as a “drunken gait,” with distinctive features including variable foot placement, irregular foot trajectories, a widened stance, a veering path of movement, and poor overall coordination of the legs. Thus, walking tends to look clumsy and unstable.

Impacts on life, work, and recreation

The impact of cerebellar ataxia on life expectancy varies depending on the type of condition, age of onset, severity, and other factors. Many affected individuals have normal life expectancy and learn to cope with their condition; some even enjoy relatively normal lives. For others, however, ataxia can impinge on work, home life, and recreation. Many affected persons find that their jobs become difficult to perform with ataxia. Ataxic hand movements make handwriting illegible and can cause difficulties with typing on the computer, while dysarthria can make talking on the phone difficult. For individuals with physically demanding jobs, balance problems and walking ataxia can affect performance. Often, individuals find that they must modify their jobs or become trained in another area in order to continue working. At home, modifications such as the installation of handrails and grab bars can help individuals better manage conditions such as walking ataxia. Recreational activities also can be modified in order to increase opportunities for participation for persons with cerebellar ataxia.

Treatment

There are few treatments for cerebellar ataxia, and medications that are capable of slowing the progression of degenerative diseases of the cerebellum are lacking. Therefore, the main treatment available to patients is rehabilitation training, which can include physical, occupational, and speech therapy. Those therapies can lead to improvements in physical strength and mobility, performance of day-to-day tasks, communication, and swallowing.

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