Ataxia

Ataxia is a term derived from the Greek words meaning "lack of order." It refers to a neurological sign characterised by the impairment of voluntary muscle movement coordination. This condition can manifest in various forms and affects different parts of the nervous system responsible for coordinating movement, such as the cerebellum. Ataxia can present as an isolated symptom or as part of a broader neurological disorder.

Signs & Symptoms

Ataxia presents with a range of symptoms, depending on the affected area of the nervous system. Common symptoms include:

• Lack of coordination
• Slurred speech
• Trouble eating and swallowing
• Deterioration of fine motor skills
• Difficulty walking
• Gait abnormalities
• Eye movement abnormalities
• Tremors
• Heart problems

Certain types of ataxia have specific symptoms. For example, cerebellar ataxia often results in poor balance, a widened base gait, and dysarthria (impaired articulation). Sensory ataxia is marked by a "stomping" gait with heavy heel strikes and postural instability, especially in poorly lit environments. Vestibular ataxia is associated with vertigo, nausea, and vomiting in acute cases.

Types of Ataxia

Cerebellar Ataxia

Cerebellar ataxia arises from dysfunction in the cerebellum, which integrates neural information for smooth movement coordination. Symptoms can include poor balance, scanning speech, tremors, and incoordination of movement. Depending on the specific cerebellar structures affected, individuals may exhibit a wide-based gait, intention tremors, dysdiadochokinesia (difficulty with rapidly alternating movements), and dysmetria (difficulty judging distances).

Sensory Ataxia

Sensory ataxia results from the loss of proprioception, the ability to sense the position of body parts. This is often due to dysfunction in the dorsal columns of the spinal cord. Patients may exhibit a stomping gait and positive Romberg's test, where instability worsens markedly with eyes closed.

Vestibular Ataxia

Vestibular ataxia stems from dysfunction in the vestibular system, which can cause vertigo, nausea, and vomiting in acute cases. Chronic cases may present with dysequilibrium without the classic vertigo symptoms.

Causes

Ataxia can have various causes, including:

• Focal Lesions: Strokes, brain tumours, multiple sclerosis, and inflammatory conditions can cause localised ataxia depending on the lesion site.
• Exogenous Substances: Alcohol, certain prescription medications, and recreational drugs can induce ataxia through central nervous system depression.
• Radiation Poisoning: Severe acute radiation poisoning can induce ataxia.
• Vitamin Deficiencies: Deficiencies in vitamins B12 and E can lead to ataxia.
• Hypothyroidism: Neurological dysfunction from hypothyroidism can manifest as ataxia.
• Hereditary Disorders: Various genetic conditions, such as Friedreich's ataxia, spinocerebellar ataxia, and ataxia-telangiectasia, can cause ataxia.
• Autoimmune Diseases: Conditions like gluten ataxia and cerebellar ataxia associated with anti-GAD antibodies are autoimmune in nature.

Diagnosis

Diagnosis of ataxia involves several approaches:

• Imaging Studies: CT scans or MRIs can identify structural abnormalities in the brain.
• Lumbar Puncture: Obtaining cerebrospinal fluid can help identify infectious or inflammatory causes.
• Genetic Testing: Identifies mutations associated with hereditary ataxias.

Treatment

Treatment of ataxia depends on the underlying cause. For focal injuries like stroke or tumours, recovery is generally better compared to degenerative conditions. Specific treatments are available for certain types of ataxia, such as vitamin E supplementation for vitamin E deficiency and a gluten-free diet for gluten ataxia.

Pharmacological treatments may include drugs like 5-hydroxytryptophan, idebenone, amantadine, and coenzyme Q10. Physical and occupational therapy play a very important role in managing ataxia, focusing on balance training, coordination exercises, and gait aids. Therapists may use tools like the International Cooperative Ataxia Rating Scale (ICARS) and the Scale for the Assessment and Rating of Ataxia (SARA) to assess and track progress.

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Self-assessment MCQs (single best answer)

What is the origin of the term "ataxia"?

Which part of the brain is primarily responsible for coordinating voluntary muscle movements and is often affected in cerebellar ataxia?

Which symptom is NOT commonly associated with ataxia?

What type of ataxia is characterised by a "stomping" gait and postural instability, especially in poorly lit environments?

Which of the following is NOT a common cause of ataxia?

Which type of ataxia is often associated with vertigo, nausea, and vomiting in acute cases?

Which diagnostic approach is used to identify structural abnormalities in the brain for ataxia patients?

Which hereditary disorder is known to cause ataxia?

What is the role of physical and occupational therapy in the management of ataxia?

What does a positive Romberg's test indicate in a patient with sensory ataxia?