MRCP PACES Neurology: Mastering Cerebellar Examination

MRCP PACES Neurology: Mastering the Cerebellar Examination

The cerebellar examination is one of the most frequently tested and high-yield neurology presentations in MRCP PACES Station 3. Candidates often lose marks not because they fail to elicit signs, but because they present an unstructured, incomplete, or poorly interpreted set of findings. This guide breaks down everything you need to know—examination technique, clinical interpretation, and examiner-ready presentation—to help you approach cerebellar cases with the precision of a registrar.

Why Cerebellar Signs Are So Frequently Tested

Cerebellar dysfunction produces a constellation of signs that are clinically observable, making them ideal for a bedside exam setting. Examiners love cerebellar cases because they test:

• Your ability to perform a structured neurological examination

• Your knowledge of localisation within the nervous system

• Your skill in generating a differential diagnosis from a focused set of findings

• Whether you can safely distinguish cerebellar signs from brainstem pathology, sensory ataxia, or parkinsonian tremor

Common conditions encountered include:

• Multiple sclerosis (cerebellar plaques)

• Stroke (posterior circulation infarcts)

• Alcohol-related cerebellar degeneration (anterior superior vermis)

• Hereditary cerebellar ataxias (e.g., Friedreich's ataxia, spinocerebellar ataxias)

• Posterior fossa tumours (acoustic neuroma, medulloblastoma in younger patients)

• Paraneoplastic cerebellar degeneration

• Huntington's disease (with cerebellar features)

PACES Station 3: Where Cerebellar Signs Fit In

In Station 3 (Cardiovascular, Neurological, Abdominal), you will be instructed to examine a specific system. For neurology, the instruction might be:

"This patient has noticed some problems with their balance and coordination. Please examine their neurological system."

Alternatively, you may be asked to perform a focused cerebellar examination or examine the lower limbs / upper limbs with a coordination component.

The key is to recognise cerebellar signs early in your examination and then tailor the rest of your assessment accordingly.

Step-by-Step Cerebellar Examination Technique

1. General Inspection (At the Foot of the Bed)

Before touching the patient, observe:

• Posture and gait: Is there an ataxic gait (wide-based, staggering)? Can the patient stand unsupported (Romberg's test)?

• Abnormal movements: Is there an intention tremor or a resting tremor (think Parkinsonism if resting)?

• Speech: Listen for scanning dysarthria—characterised by irregular emphasis on syllables, a hallmark of cerebellar dysfunction.

• Scars: Posterior fossa craniotomy scars (retro-auricular), VP shunt tubing.

• Assistive devices: Walking aids, ankle-foot orthoses.

Exam Tip: If you notice dysarthria or an ataxic gait during the first 10 seconds, you've likely found your system. Mentally pivot to a cerebellar-focused examination for the remainder.

2. Cranial Nerves (Targeted Assessment)

Not every cranial nerve is relevant to cerebellar assessment. Focus on:

Key cerebellar eye signs:

• Gaze-evoked nystagmus: Nystagmus present when looking laterally, direction changes with gaze direction. Suggests cerebellar or brainstem pathology.

• Pendular nystagmus: Seen in congenital visual impairment or severe cerebellar disease.

• Downbeat nystagmus: Pathognomonic for foramen magnum / craniocervical junction lesions (e.g., Arnold-Chiari malformation).

• Opsoclonus: Rapid, chaotic, multi-directional eye movements—classically seen in paraneoplastic cerebellar degeneration (think neuroblastoma in children, small cell lung cancer in adults).

3. Speech Assessment

Ask the patient to say:

• "British Constitution"

• "West Register Street"

• "Baby hippopotamus"

Listen specifically for:

• Scanning dysarthria: Words are spoken slowly with irregular spacing between syllables and variable emphasis. Each syllable is articulated carefully but the rhythm is disrupted.

• Slurring: May indicate pseudobulbar palsy (UMN lesion) or intoxication.

Distinguish from other speech disorders:

• Dysphasia ( receptive or expressive): impairment of language content, not articulation → cortical lesion.

• Dysphonia: Hoarse or quiet voice → vocal cord or laryngeal pathology.

• Pseudobulbar speech: Spastic, strained quality → bilateral UMN lesion (e.g., MS, MND).

4. Upper Limb Examination

This is where the classic cerebellar signs are demonstrated.

a) Tone

• Cerebellar lesions typically produce hypotonia (reduced tone), though this is often subtle and difficult to elicit.

• Contrast with hypertonia (spasticity or rigidity), which would suggest pyramidal or extrapyramidal pathology.

b) Power

• Power is usually preserved in pure cerebellar disease.

• If weakness is present, consider combined pathology (e.g., MS with both cerebellar plaques and motor tract involvement).

c) Reflexes

• Reflexes may be pendular (slow, swinging quality), particularly at the knee. This is caused by hypotonia.

• Hyporeflexia or areflexia may suggest a co-existing peripheral neuropathy (e.g., Friedreich's ataxia).

d) Coordination — The Core Assessment

i) Finger-to-Nose Test

Ask the patient to touch your finger, then their nose, repeating the movement. Move your finger to different positions to test accuracy in different planes.

• Intention tremor: Tremor that worsens as the finger approaches the target (nose or examiner's finger).

• Dysmetria: Overshooting (past-pointing) or undershooting the target.

• Perseveration: Inability to stop the movement promptly.

ii) Dysdiadochokinesis

Ask the patient to rapidly alternate pronation and supination of one hand on the opposite palm.

• Look for irregular rhythm and clumsy, slow alternating movements.

• Test both sides—unilateral dysdiadochokinesis localises to the ipsilateral cerebellar hemisphere.

iii) Rebound Phenomenon (Stewart-Holmes Test)

Ask the patient to hold their arm flexed at the elbow. Pull against their arm and then suddenly release.

• Positive rebound: The patient's arm swings uncontrollably towards their face. They cannot stop the movement promptly.

• This indicates loss of the cerebellum's role in modulating and checking movements.

e) Sensation

• Proprioception (joint position sense) is critical to test because sensory ataxia (from dorsal column pathology) can mimic cerebellar ataxia.

• Romberg's test (distinguished below) is the functional equivalent.

Distinguishing Cerebellar Ataxia from Sensory Ataxia:

Feature	Cerebellar Ataxia	Sensory Ataxia
Romberg's test	Positive or negative (ataxia doesn't worsen significantly with eyes closed)	Positive (ataxia worsens markedly with eyes closed)
Joint position sense	Preserved	Impaired
Vibration sense	Preserved	Impaired (often first to be lost)
Reflexes	Pendular or normal	Absent (due to peripheral neuropathy or dorsal column lesion)
Speech	Scanning dysarthria	Normal
Nystagmus	Often present	Absent

5. Lower Limb Examination

a) Tone, Power, Reflexes

• Same principles as upper limbs.

• Look for hypotonia and pendular reflexes at the knee.

• Check plantar responses—extensor plantars suggest pyramidal tract involvement (not a cerebellar sign per se, but may co-exist in conditions like MS).

b) Coordination

i) Heel-to-Shin Test

Ask the patient to run the heel of one foot down the opposite shin from knee to ankle, then back up.

• Ataxic movement: The heel wobbles side to side and falls off the shin.

• Dysmetria: The heel overshoots or undershoots the starting position.

ii) Foot Tapping

Ask the patient to tap their foot rapidly against your hand or the floor.

• Look for irregular rhythm and clumsiness—the lower limb equivalent of dysdiadochokinesis.

6. Gait Assessment

This is one of the most critical components and should never be omitted.

• Cerebellar gait: Wide-based, staggering, irregular steps. Patient may veer to one side (towards the side of the lesion in unilateral cerebellar hemisphere pathology).

• Sensory ataxic gait: Stomping gait, patient watches their feet. Worsens in poor lighting.

• Parkinsonian gait: Shuffling, festinating, reduced arm swing.

Tandem gait (heel-to-toe walking) exaggerates cerebellar signs and should be tested if the patient can safely stand.

7. Romberg's Test

Ask the patient to stand with feet together and eyes open. Then ask them to close their eyes.

• Negative Romberg: Patient remains stable with eyes closed → cerebellar ataxia (the cerebellum doesn't rely on visual input for coordination).

• Positive Romberg: Patient sways or falls with eyes closed → sensory ataxia (loss of proprioception means the patient relies on vision for balance).

Exam Warning: Romberg's test is about proprioception, not cerebellar function. Many candidates incorrectly state that a positive Romberg suggests cerebellar disease. It does not. A positive Romberg suggests a dorsal column or peripheral neuropathy problem.

Common Cerebellar Presentations in PACES: Pattern Recognition

Pattern 1: Young Patient with Subacute Ataxia

Signs: Scanning dysarthria, intention tremor, gaze-evoked nystagmus, dysdiadochokinesis, ataxic gait, possible extensor plantars, internuclear ophthalmoplegia (INO).

Top differential: Multiple sclerosis

Supporting clues: Optic atrophy (pale discs), INO on eye movement testing, spasticity in limbs, relapsing-remitting history.

Pattern 2: Middle-Aged Patient with Progressive Ataxia and Family History

Signs: Pes cavus, absent reflexes, dysarthria, scoliosis, cardiomyopathy (signs of heart failure).

Top differential: Friedreich's ataxia

Supporting clues: Onset before 25 years, autosomal recessive (GAA trinucleotide repeat), diabetes mellitus, hypertrophic cardiomyopathy.

Pattern 3: Older Patient with Unilateral Cerebellar Signs

Signs: Unilateral dysmetria, intention tremor, nystagmus worse on one side, veering gait towards affected side, possibly with ipsilateral CN deficits.

Top differential: Posterior circulation stroke (PICA territory) or cerebellopontine angle lesion

Supporting clues: Sudden onset (stroke), ipsilateral facial sensory loss and contralateral body sensory loss (lateral medullary/Wallenberg syndrome), ipsilateral LMN facial palsy and hearing loss (acoustic neuroma).

Pattern 4: Chronic Alcohol User with Gait Ataxia

Signs: Predominantly truncal and gait ataxia (vermis affected), relatively preserved limb coordination, possible peripheral neuropathy signs.

Top differential: Alcohol-related cerebellar degeneration

Supporting clues: History of chronic alcohol excess, macrocytosis on bloods, deranged LFTs, stigmata of chronic liver disease.

Exam Pearl: Alcohol-related cerebellar degeneration primarily affects the anterior superior vermis, producing predominantly truncal and gait ataxia with relative sparing of limb coordination. This contrasts with cerebellar hemisphere lesions, which produce more prominent appendicular (limb) ataxia.

Presenting Your Findings: The Examiner-Ready Summary

Your summary should be structured, concise, and interpretive. Aim for 60–90 seconds.

Template:

"I examined Mr [X], a [age]-year-old patient, who has clinical features consistent with a cerebellar syndrome.

The key positive findings are:

• Scanning dysarthria

• Gaze-evoked nystagmus, worse on looking to the [right/left]

• Bilateral dysmetria and intention tremor on finger-to-nose testing

• Dysdiadochokinesis bilaterally

• Ataxic, wide-based gait with inability to perform tandem gait

• Heel-to-shin ataxia bilaterally

Negative findings of note:

• No sensory deficit, with preserved proprioception and vibration sense

• Romberg's test was negative

• No focal weakness or sensory level

• No cranial nerve deficit suggestive of brainstem involvement

These findings localise to the cerebellum, with the pattern suggesting [vermian / hemispheric / diffuse] involvement.

My primary differential diagnosis would be:

1. Multiple sclerosis – given the [age group] and presence of [INO/optic atrophy]

2. Hereditary cerebellar ataxia – such as Friedreich's ataxia, given [pes cavus/absent reflexes]

3. Posterior circulation stroke – though the gradual onset makes this less likely

To complete my assessment, I would like to:

• Take a detailed history, including family history, drug history, and alcohol intake

• *Perform a full cognitive assessment *

• Arrange neuroimaging (MRI brain and spine)

• Check bloods including FBC (for macrocytosis), LFTs, TFTs, vitamin B12, and copper studies

• Consider genetic testing if a hereditary ataxia is suspected

• Perform a lumbar puncture with CSF analysis for oligoclonal bands if MS is suspected"

Common Mistakes That Cost Marks

1. Failing to Test for Sensory Ataxia

Many candidates present a cerebellar syndrome without testing proprioception, vibration sense, and Romberg's test. The examiner's first question will often be: "How do you know this isn't sensory ataxia?" If you haven't tested these, you cannot answer.

2. Confusing Romberg's Test with Cerebellar Function

As emphasised above, Romberg's test assesses proprioceptive pathways, not cerebellar function. Stating that a positive Romberg suggests cerebellar dysfunction is a common and significant error.

3. Not Commenting on Gait

Gait is often the most abnormal feature in cerebellar disease. If you don't ask the patient to walk, you're missing critical evidence. Even if the instruction focuses on limb examination, you should always request to assess gait if clinically relevant.

4. Overcalling Cerebellar Signs

Not every patient with a tremor has cerebellar disease. Ensure you distinguish:

• Intention tremor (cerebellar) from resting tremor (Parkinson's) or postural tremor (essential tremor, hyperthyroidism)

• Ataxic gait from antalgic gait (pain), parkinsonian gait, or hemiparetic gait

5. Presenting a Shopping List Instead of a Differential

Avoid listing every possible cause of ataxia. Instead, localise the lesion based on your findings (vermis vs hemisphere vs peduncle), and then generate a focused, justified differential based on the patient's demographics and clinical features.

High-Yield Knowledge for the Examiner's Questions

After your presentation, the examiner will ask follow-up questions. Here are some commonly tested areas:

Anatomy of the Cerebellum

Causes of Cerebellar Ataxia (Categorised)

Vascular:

• Posterior circulation stroke (PICA, AICA, SCA territories)

• Cerebellar haemorrhage

• Vertebrobasilar insufficiency

Demyelinating:

• Multiple sclerosis

• Progressive multifocal leukoencephalopathy (PML)

Hereditary/Genetic:

• Friedreich's ataxia (autosomal recessive, GAA repeat on chromosome 9)

• Spinocerebellar ataxias (SCA1-40+, autosomal dominant, CAG repeats)

• Ataxia-telangiectasia (ATM gene, AR)

• Fragile X-associated tremor/ataxia syndrome (FXTAS, premutation CGG repeat)

• Wilson's disease (ATP7B gene)

Metabolic/Toxic:

• Alcohol-related cerebellar degeneration

• Vitamin E deficiency

• Thiamine deficiency (Wernicke's encephalopathy)

• Hypothyroidism

• Drug-induced (phenytoin, lithium, alcohol, chemotherapeutic agents)

Infectious/Post-infectious:

• Post-viral cerebellitis (especially in children, post-varicella)

• Creutzfeldt-Jakob disease (CJD)

• HIV-related

Neoplastic/Paraneoplastic:

• Posterior fossa tumours (medulloblastoma, ependymoma, haemangioblastoma)

• Metastases (lung, breast, melanoma)

• Paraneoplastic cerebellar degeneration (anti-Yo, anti-Hu, anti-Ri antibodies)

Autoimmune:

• Gluten ataxia (coeliac disease-associated)

• Anti-GAD antibody-associated ataxia

• Steroid-responsive encephalopathy with autoimmune thyroiditis (Hashimoto's encephalopathy)

Investigating Cerebellar Ataxia

First-line:

• MRI brain (with dedicated posterior fossa sequences)

• FBC, U&E, LFTs, TFTs, vitamin B12, folate

• Vitamin E levels

• Alcohol history + gamma-GT, MCV

**Second-line (based on clinical suspicion):
**

• Genetic testing (Friedreich's ataxia, SCAs)

• Paraneoplastic antibody panel (anti-Yo, anti-Hu, anti-Ri, anti-Tr)

• Anti-GAD antibodies

• Anti-tissue transglutaminase (coeliac screen)

• CSF analysis (oligoclonal bands for MS)

• Serum copper and caeruloplasmin (Wilson's)

• Toxicology screen (phenytoin levels)

Key Takeaways for PACES Success

1. Always test sensation (especially proprioception and vibration) when assessing coordination. Sensory ataxia is the most common mimic.

2. Assess gait in every neurological case where cerebellar signs are suspected. The type of gait abnormality is highly localising.

3. Localise before you generalise. Determine whether the lesion is in the vermis (truncal/gait), hemisphere (ipsilateral limb), or flocculonodular lobe (nystagmus, disequilibrium) before generating your differential.

4. Understand the side of the lesion. Cerebellar signs are ipsilateral to the lesion (unlike cortical lesions, which produce contralateral signs). This is because the cerebellum exerts its influence on the contralateral motor cortex via the thalamus, so a right cerebellar lesion affects the right cerebellar output to the left cortex, resulting in right-sided clinical signs.

5. Practise the presentation. Your summary should flow naturally, with positive findings first, relevant negatives second, localisation third, and a justified differential fourth. This is what separates a pass from a distinction.

Conclusion

The cerebellar examination in MRCP PACES is a test of clinical precision and interpretive skill. By mastering the examination technique, understanding the anatomy, and presenting your findings in a structured, registrar-level manner, you can confidently tackle any cerebellar case that appears in your exam.

Remember: the examiner is not just looking for signs—they're looking for someone who can think like a neurologist. That means localising the lesion, generating a sensible differential, and planning appropriate investigations.

Good luck with your PACES preparation!

Have a specific cerebellar case you'd like to practise? Try presenting it out loud using the template above, timing yourself to 60–90 seconds. This is the single most effective way to prepare for Station 3.