RCGP SCA Algorithm — UK Primary Care
Acute-onset ataxia is a neurological emergency until proven otherwise — a cerebellar stroke can rapidly cause fatal brainstem compression and hydrocephalus.
Posterior circulation strokes are missed in up to 30% of cases 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 24–72 h, compressing the brainstem and obstructing CSF flow (hydrocephalus) — a neurosurgical emergency. Wernicke's encephalopathy is under-diagnosed (the classic triad is present in only ~10%): give parenteral thiamine to any at-risk patient with ataxia/confusion, and always before IV glucose, which can precipitate it.
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 negative Romberg (unsteady regardless) points to a cerebellar cause, where vision cannot compensate. Distinguishing peripheral vestibular causes (benign) from central ones (stroke) acutely relies on the HINTS examination, which in trained hands outperforms early MRI for posterior-circulation stroke.
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 withhold the drug. 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 — ataxia impairs vehicle control, and there is a legal duty to advise patients to notify the DVLA.
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 and stopping antiepileptic or lithium toxicity, 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.