Cerebellar Disorders
Disorders of the cerebellum causing ataxia, dysarthria, nystagmus, intention tremor, and dysdiadochokinesis. Causes include stroke, alcohol, MS, space-occupying lesions, paraneoplastic syndromes, and hereditary ataxias. The mnemonic DANISH PAST covers the key cerebellar signs.
Key Facts
Cerebellar signs (DANISH PAST): Dysdiadochokinesis, Ataxia, Nystagmus, Intention tremor, Scanning/staccato speech, Hypotonia; Past-pointing, Ataxic gait (broad-based), Slurring of speech, Titubation Acute causes: posterior circulation stroke (cerebellar infarct/haemorrhage — emergency), alcohol intoxication, drug toxicity (phenytoin, carbamazepine, lithium), Wernicke encephalopathy Subacute/chronic: MS, alcoholic cerebellar degeneration, paraneoplastic cerebellar degeneration (anti-Yo, anti-Hu, anti-Tr), brain tumour (medulloblastoma, haemangioblastoma) Hereditary ataxias: Friedreich ataxia (autosomal recessive), spinocerebellar ataxias (autosomal dominant, CAG repeats), ataxia-telangiectasia Cerebellar lesions are IPSILATERAL: signs on the SAME side as the lesion (unlike cortical motor signs which are contralateral) Posterior fossa mass: risk of obstructive hydrocephalus and tonsillar herniation — neurosurgical emergency
Overview
Key Facts
Cerebellar disorders are diverse in aetiology. Acute cerebellar syndrome requires urgent evaluation for stroke. Chronic progressive ataxia requires systematic investigation including neuroimaging, toxicology, paraneoplastic screen, and genetic testing.
Epidemiology
Varies by cause. Posterior circulation stroke accounts for ~20% of ischaemic strokes. Alcohol-related cerebellar degeneration common in chronic alcoholics. Hereditary ataxias: Friedreich ataxia prevalence ~2-4 per 100,000.
Aetiology
Acute: posterior circulation stroke, haemorrhage, infection (cerebellitis), drug toxicity, Wernicke encephalopathy Subacute: MS, paraneoplastic (anti-Yo — ovarian/breast; anti-Hu — SCLC; anti-Tr — Hodgkin), tumour, abscess, prion disease (CJD) Chronic: alcoholic degeneration (anterior vermis), hereditary ataxias (Friedreich, SCAs), hypothyroidism, vitamin E/B12 deficiency, coeliac disease (gluten ataxia)
Pathophysiology
The cerebellum coordinates voluntary movement, balance, and motor learning. Midline (vermis): truncal ataxia, gait ataxia, nystagmus. Lateral (hemispheres): limb ataxia (intention tremor, dysmetria, dysdiadochokinesis), dysarthria. Each cerebellar hemisphere controls the ipsilateral side of the body (double decussation of cerebellar pathways).
Clinical Presentation
Cerebellar Signs
- Ataxia: limb (intention tremor, dysmetria, past-pointing) and truncal/gait (broad-based, unsteady)
- Dysarthria: scanning/staccato speech (irregular rate and volume)
- Nystagmus: horizontal (towards side of lesion); may be multidirectional in diffuse disease
- Dysdiadochokinesis: inability to perform rapid alternating movements smoothly
- Hypotonia: reduced muscle tone
- Titubation: head/trunk oscillation
- Pendular reflexes: slow oscillatory tendon reflexes
- Rebound phenomenon: inability to check a suddenly released opposing force
Localisation
- Vermis: truncal ataxia, gait disturbance, nystagmus (alcohol, medulloblastoma)
- Hemisphere: ipsilateral limb ataxia, intention tremor, dysarthria
Red Flags
- Acute onset cerebellar signs → posterior circulation stroke (emergency)
- Cerebellar signs + headache/vomiting → posterior fossa mass → risk of hydrocephalus/tonsillar herniation
- Progressive cerebellar degeneration with weight loss → paraneoplastic (cancer screening)
- Young-onset progressive ataxia → Friedreich, SCA, Wilson disease
Differential Diagnosis
| Diagnosis | Key Features | Investigation |
|---|---|---|
| Posterior circulation stroke | Acute onset, vascular risk factors | CT/MRI brain (DWI) |
| Alcoholic cerebellar degeneration | Chronic alcohol excess, vermis atrophy, gait > limb ataxia | MRI (vermis atrophy), history |
| MS | Relapsing, young, multifocal CNS lesions | MRI brain/spine, CSF |
| Paraneoplastic | Subacute, weight loss, smoking history | Anti-neuronal antibodies, CT CAP |
| Friedreich ataxia | Young onset, cardiomyopathy, scoliosis, pes cavus | Genetic testing (GAA repeat) |
| Drug toxicity | Phenytoin, carbamazepine, lithium, alcohol | Drug levels |
Diagnosis / Investigation
Imaging
- MRI brain: cerebellar atrophy (pattern — vermis vs hemisphere), mass lesion, infarction, demyelination
- CT brain: urgent if acute (stroke, haemorrhage, hydrocephalus)
Bloods
- Drug levels: phenytoin, carbamazepine, lithium
- TFTs: hypothyroidism
- B12, vitamin E: deficiency
- Anti-tissue transglutaminase (tTG): coeliac disease/gluten ataxia
- Anti-neuronal antibodies: paraneoplastic panel (anti-Yo, anti-Hu, anti-Tr, anti-CV2, anti-GAD)
- FBC, LFTs, GGT: alcohol
- Copper, caeruloplasmin: Wilson disease (young onset)
- Alpha-fetoprotein: ataxia-telangiectasia (raised)
Genetic Testing
- Friedreich ataxia: GAA repeat expansion in FXN gene (autosomal recessive)
- Spinocerebellar ataxias: CAG repeats (SCA1-3, SCA6, SCA7 — autosomal dominant)
Other
- CT CAP: paraneoplastic (cancer screening)
- LP/CSF: MS (OCBs), infection, malignancy
Management
Treat Underlying Cause
- Stroke: acute stroke pathway (thrombolysis/thrombectomy if eligible); posterior fossa haemorrhage/infarction with hydrocephalus → neurosurgery (EVD, decompressive craniectomy)
- Alcohol: abstinence, thiamine (Pabrinex IV then oral thiamine), nutritional support
- Drug toxicity: reduce/stop offending drug, check levels
- MS: DMTs (see MS section)
- Paraneoplastic: treat underlying malignancy + immunotherapy (IVIg, steroids, rituximab)
- Hypothyroidism: levothyroxine replacement
- Gluten ataxia: strict gluten-free diet
Symptomatic
- Physiotherapy: balance training, gait rehabilitation, falls prevention — MOST IMPORTANT for all chronic ataxias
- OT: adaptive devices, home modifications
- SALT: speech and swallowing therapy
- Tremor: limited pharmacological options; 4-aminopyridine (episodic ataxia type 2); DBS (research)
Hereditary Ataxias
- No disease-modifying treatment for most
- Friedreich ataxia: cardiac monitoring (cardiomyopathy), scoliosis management, physiotherapy; omaveloxolone (Nrf2 activator) approved in some countries
Referral Criteria
- Acute: emergency neurology/neurosurgery
- Chronic progressive: neurology (ataxia specialist service)
- Genetics: hereditary ataxias
Prognosis
Depends on cause. Posterior circulation stroke: variable; posterior fossa mass effect can be rapidly fatal without intervention. Alcoholic cerebellar degeneration: stabilises with abstinence; limited recovery of established damage. Paraneoplastic: often irreversible even with tumour treatment (neuronal loss occurs early). Friedreich ataxia: progressive; wheelchair-dependent ~10-15 years after onset; cardiomyopathy is leading cause of death (mean age of death ~35). SCAs: progressive; variable rate depending on subtype.
Other Relevant Information
Cerebellar Signs Mnemonic (DANISH)
| Letter | Sign |
|---|---|
| D | Dysdiadochokinesis |
| A | Ataxia (limb and gait) |
| N | Nystagmus |
| I | Intention tremor |
| S | Scanning/staccato speech |
| H | Hypotonia |
Common Paraneoplastic Cerebellar Antibodies
| Antibody | Associated Cancer |
|---|---|
| Anti-Yo (PCA-1) | Ovarian, breast |
| Anti-Hu (ANNA-1) | Small cell lung cancer |
| Anti-Tr (DNER) | Hodgkin lymphoma |
| Anti-CV2 (CRMP5) | SCLC, thymoma |
| Anti-GAD | Thymoma, breast (also type 1 diabetes) |