RCGP SCA Algorithm — UK Primary Care
Sudden-onset new ataxia or unsteadiness should be treated as possible posterior-circulation stroke until excluded (NICE NG127 and NG128). Refer immediately through the local stroke/emergency pathway when there is a focal neurological deficit, acute vestibular syndrome not explained by BPPV or postural hypotension, abnormal trained HINTS examination, reduced consciousness, severe headache or vomiting — a cerebellar stroke can rapidly cause fatal brainstem compression and hydrocephalus.
Posterior circulation strokes are often missed because the standard FAST tool is insensitive to cerebellar/brainstem signs — isolated acute ataxia, vertigo or diplopia can be the only feature. A cerebellar infarct/haemorrhage can swell over the first few days, compressing the brainstem and obstructing CSF flow (hydrocephalus) — a neurosurgical emergency. Wernicke's encephalopathy is under-diagnosed (the classic triad is present in only a minority): give parenteral thiamine urgently to any at-risk patient with confusion, ophthalmoplegia or ataxia, before or alongside glucose where feasible — but never delay treatment of severe hypoglycaemia.
The tempo of onset narrows the differential more than anything else. Always clarify exactly how quickly it came on and whether it is progressive.
Onset tempo is the most powerful triage tool in ataxia. Sudden onset = vascular or toxic until proven otherwise (emergency); subacute progression over weeks should raise the spectre of a tumour or paraneoplastic syndrome; slowly progressive over years suggests a degenerative, hereditary or nutritional cause that can be worked up in primary care. A careful drug and alcohol history identifies the large group of reversible ataxias — antiepileptic toxicity, lithium toxicity, and thiamine/B12 deficiency are all treatable and must not be missed.
The Romberg test is the key bedside discriminator: a positive Romberg (steady with eyes open, unsteady when closed) indicates a sensory ataxia — the patient relies on vision to compensate for lost proprioception. A positive Romberg can also reflect vestibular loss. If the patient cannot stand safely with eyes open (as in severe cerebellar ataxia), the test is not interpretable. Distinguishing peripheral vestibular causes (benign) from central ones (stroke) acutely uses the HINTS examination only in acute vestibular syndrome and only when performed by a trained, experienced examiner; if one is unavailable, refer immediately through the stroke pathway.
Truncal ataxia (inability to sit or stand unsupported) localises to the cerebellar vermis (midline) and is a feature of alcohol-related degeneration and midline tumours (e.g. medulloblastoma in children). Lateralised limb ataxia is ipsilateral to a cerebellar hemisphere lesion. Always examine the fundi: papilloedema in a patient with ataxia and headache mandates urgent imaging before any lumbar puncture. Documenting proprioception and vibration sense is essential — a sensory ataxia from B12 deficiency is reversible if caught early but causes irreversible cord damage if missed.
A panel of simple bloods identifies the common reversible ataxias that primary care can act on: B12 deficiency, hypothyroidism, alcohol/liver disease, and antiepileptic or lithium toxicity. Lithium toxicity is a particular trap — ataxia, coarse tremor and confusion signal a level that can rise rapidly to fatal levels, so check it urgently and agree a same-day plan with acute/specialist advice before withholding doses. MRI is far superior to CT for the cerebellum and posterior fossa and is the imaging of choice for non-acute ataxia, but it should be requested through neurology, who also coordinate paraneoplastic and genetic work-up.
The referral destination follows directly from the onset tempo established in the history. Acute ataxia is treated as a stroke/emergency; subacute progression earns an urgent neurology referral (to catch tumours, demyelination and paraneoplastic syndromes within a useful window); chronic ataxia is worked up more deliberately once reversible causes are excluded. Driving is an important and often-forgotten conversation — advise not driving where symptoms could impair safe vehicle control, and advise checking the current DVLA standards and notifying DVLA where required.
Next steps: see Stroke and TIA · Harmful drinking and alcohol dependence · Hypothyroidism
A meaningful proportion of ataxia is reversible, and primary care can make a real difference: replacing B12 before the dorsal-column damage becomes permanent, recognising antiepileptic or lithium toxicity and arranging same-day review, treating hypothyroidism, and giving thiamine to at-risk drinkers. For the many ataxias without a curative treatment (hereditary, degenerative), multidisciplinary rehabilitation — physiotherapy, occupational therapy and speech and language therapy — is the evidence-based mainstay and substantially improves function, safety and quality of life.
For chronic and progressive ataxias there is rarely a cure, so the goals shift to maximising function, preventing complications and supporting quality of life. Falls and aspiration are the principal causes of harm — proactive OT, physiotherapy and SALT input prevent injury and hospital admission. Ataxia UK provides specialist information and peer support that patients and carers value highly. Continued alcohol use in alcohol-related cerebellar degeneration drives ongoing, eventually irreversible, loss — cessation is the single most effective intervention.
After an acute cerebellar stroke the danger period extends over the first few days as oedema peaks — a patient who becomes drowsy or develops worsening headache and vomiting may be developing hydrocephalus or brainstem compression and needs emergency reassessment. For chronic ataxias, the recurring safety issues are falls and aspiration: a low threshold for SALT swallow assessment prevents aspiration pneumonia, the commonest cause of death in advanced cerebellar disease. Clear safety-netting and documented driving advice protect the patient and are medico-legally important.