Ataxia refers to problems affecting the fine control of posture and movement/balance, resulting in poor coordination. Ataxia is a symptom which can be due to many different causes. As such, it is neither a specific diagnosis nor a disease.
Cerebellar ataxia means unsteadiness due to pathology in the cerebellum, which is a leaf-like structure in the back part of the brain.
Medical text written December 2010; updated June 2018 by Leena D Mewasingh, Consultant Paediatric Neurologist and Honorary Senior Clinical Lecturer, St Mary’s Hospital, Imperial College Healthcare NHS Trust, London, UK.
Although great care has been taken in the compilation and preparation of all entries to ensure accuracy, we cannot accept responsibility for any errors or omissions. Any medical information is provided is for education/information purposes and is not designed to replace medical advice by a qualified medical professional.
People with this disorder have a broad-based gait, which means their feet are wider apart when they walk. This is due to their balance problem, which can also be present in sitting and standing. Cerebellar problems can also lead to: a lack of purposeful coordination in hands (intention tremor), imprecision when trying to reach a target with one’s fingers (past pointing), difficulties with fast and alternating actions (dysdiadochokinesia) and slurred speech (dysarthria). The overall result is that the person can appear clumsy. The eyes can also be affected and seem to ‘wobble’, a clinical finding known as nystagmus. (See entry Nystagmus)
Cerebellar ataxia may occur suddenly (as an acute problem) or may be long -standing (chronic problem). In some of these chronic cases, the symptoms can get worse over time (known as progressive ataxia).
The main causes of acute cerebellar ataxia are:
- drug ingestion (usually accidental eg a young child swallowing tablets not prescribed for them)
- due to an infection, which is usually viral, the most common one being chickenpox.
- at times the ataxia occurs after an infection, referred to as post-infectious or para-infectious cerebellitis (again this is often after chickenpox, but other viruses can also lead to this)
- less commonly a lesion in the cerebellum eg a tumour can be a cause of either acute or chronic ataxia
Chronic ataxia can be due to a number of different causes:
- genetic (eg spinocerebellar ataxias – which occurs due to problem involving the cerebellum and part of the brainstem adjacent to it; there is a long list of genes responsible eg SCA 1,2,3; ataxia-telangiectasia and Friedreich’s ataxia are some of the genetic causes)
- congenital/structural (eg there is a brain malformation present since birth affecting the cerebellum and possibly other nearby structures)
- metabolic problems
- brain tumours involving the cerebellum (which can also cause acute ataxia).
A detailed clinical and family history is essential as this often gives clues to the type of ataxia and to what tests might need doing. This is then followed by a brain scan, usually a magnetic resonance imaging (MRI) scan, and blood and urine tests. At times a lumbar puncture to analyse the fluid known as cerebrospinal fluid (CSF) may be indicated. A test of the muscles and nerves is also done in chronic cases of ataxia (Electromyogram/Nerve conduction studies).
Treatment depends on the actual cause of the ataxia. If it is thought to be due to a virus then the child may receive an intravenous drug for it (eg acyclovir or ganciclovir). In some cases, the ataxia settles over time without any specific treatment.
In most of the chronic cases of ataxia there is unfortunately no specific treatment. Physiotherapists and occupational therapists involvement is key in supporting the patient better manage their symptoms and improving their quality of life as much as possible.
In some cases of congenital malformations or tumours affecting the brain, surgery may be required. Surgery may be resective (to remove an affected area), or sometimes it can be to allow more space around those structures in the brain if there is a lot of swelling in the cerebellum (decompressive craniectomy).
The spinocerebellar ataxias (SCAs) have different modes of inheritance: autosomal dominant, autosomal recessive, or in rare cases mitochondrial or X-linked inheritance. Most of the SCAs start in adulthood, some in early adulthood and a few have their onset in childhood. Genetic counselling is indicated for these families. SCA genes are implicated in the dominant ataxias. A number of these disease-causing genes can be tested genetically. Nowadays often a gene panel will be requested for these patients that can test many ataxia genes in one go (ie from a single blood test).
Some of the other genetic causes of cerebellar ataxia can also be confirmed by genetic tests (ataxia-telangiectasia; Friedreich’s ataxia).
Prenatal testing and diagnosis is available in families who have been proven to have mutations in some of the genetic ataxias. Chorionic villus sampling is available in the first trimester of pregnancy; amniocentesis can be done early in the first trimester or later, in the second trimester .
Advice from a clinical geneticist needs to be sought preferably as soon as a family is being planned or as early in the pregnancy as possible.
Information and support in the UK for cerebellar ataxia is provided by Ataxia UK (see entry Friedreich’s Ataxia).