Presentation

The presentation of a patient with ataxia can be diverse. The ataxia may be transient (e.g. following a viral infection, also known as post-viral cerebellitis), episodic (eg: episodic ataxias due to genetic causes) or progressive (eg: in Friedreich’s ataxia, the most common ataxia in the UK¹³).

Onset may be acute (eg: in a patient with stroke) or it may be gradual. Most of the progressive ataxias are of gradual onset. Rapidity of progression is an important consideration, because such rapid progression of ataxia (over weeks) may indicate paraneoplastic cerebellar degeneration and the need to hunt for covert cancer¹⁴. Rapid progression may also be a sign of multiple system atrophy in its cerebellar form, or of prion diseases, thus the need for fast referral^15–17. Finally the age of onset should be considered; diseases presenting with ataxia in children or young adults – often developmental, metabolic or inherited – tend to differ from the neurodegenerative or immune-mediated ataxias presenting in older people. The clinician therefore has to consider all aspects of the history in coming up with a differential diagnosis for each patient.

Family history is crucial in patients with ataxia in view of the frequency with which genetic/inherited factors cause ataxia. Almost all forms of genetic transmission are recognised, but generally speaking early-onset ataxias, under 20 years of age, tend to be of autosomal recessive (AR) inheritance (e.g. Friedreich’s ataxia) whereas the spinocerebellar ataxias (SCAs) are autosomal dominant (AD) and tend to present mostly after 20 years of age; although both recessive and dominant can occur at any age. With AR inheritance there is a one in four risk of further siblings also being affected, but the parents of the patient, whilst carriers of the mutated gene, are usually themselves clinically unaffected. Parental consanguinity is sometimes identified. With AD transmission, one of the parents is likely to be affected but may have much milder clinical features. In some AD ataxias, paternal transmissions in particular tend to lead to dramatically reduced age of onset and more severe clinical phenotypes in offspring (eg:SCA1, SCA2, SCA3, SCA7, DRPLA). Ataxias due to mitochondrial disease may be an under-diagnosed cause of ‘inherited’ ataxia, but the pattern of inheritance may be complex, including maternal transmission, AR and AD inheritance^18,19. Premutations of the fragile-X gene may be a cause of adult-onset ataxia (‘fragile X-associated tremor/ataxia syndrome’ or FXTAS) that affects both men and women²⁰.

Patients with ataxia complain of incoordination and unsteadiness, slurred speech and clumsiness. Rarely, oscillopsia (due to nystagmus) is reported. The clinical signs seen in patients with ataxia can be summarised as follows²¹:

• Gait ataxia and in some cases impaired sitting balance
• Gaze-evoked and/or resting nystagmus, hypermetropic /hypometropic saccades and jerky pursuit
• Speech may be slurred (dysarthric) and have a staccato quality
• Intention tremor
• Dysmetria or ‘past-pointing’
• Dysdiadochokinesis

Patients with disorders limited to midline cerebellar disease may only show ataxia when gait is tested, especially heel-to-toe/tandem gait. It is also important to recognise that impairment of sensation (joint position sense) can produce (sensory) ataxia. Depending on the underlying cause of the ataxia, there can be additional neurological features that manifest themselves during the course of the illness. These can include ophthalmoplegia, parkinsonism, visual disturbance, peripheral neuropathy, urinary symptoms, spasticity and cognitive decline²¹.