Medicine – Bulbar Palsy vs Pseudobulbar Palsy

Bulbar palsy and pseudobulbar palsy can both cause dysarthria and dysphagia, but they arise from lesions at different levels of the motor pathway. The simplest distinction is that bulbar palsy is a lower motor neurone (LMN) disorder, whereas pseudobulbar palsy is a bilateral upper motor neurone (UMN) corticobulbar disorder.

1. Site of Lesion

Bulbar palsy: The lesion affects the motor cranial nerve nuclei in the medulla or their peripheral nerves, particularly pathways involving cranial nerves IX, X and XII.

Pseudobulbar palsy: The lesion is above the cranial nerve nuclei and affects the corticobulbar tracts bilaterally.

Therefore:

Bulbar = cranial nerve nuclei/nerves → LMN.

Pseudobulbar = bilateral corticobulbar tracts → UMN.

2. Type of Motor Neurone Lesion

Bulbar palsy: Lower motor neurone lesion.

Because LMNs are damaged, the affected muscles become weak and may undergo atrophy and fasciculation.

Pseudobulbar palsy: Upper motor neurone lesion.

Loss of descending cortical control produces spasticity and exaggerated reflexes rather than prominent muscle wasting and fasciculations.

3. Cranial Nerve Functions Affected

Both conditions particularly interfere with functions mediated through:

CN IX – glossopharyngeal nerve.

CN X – vagus nerve.

CN XII – hypoglossal nerve.

However, pseudobulbar palsy is better considered a bilateral corticobulbar syndrome, so facial and jaw movements may also be affected.

4. Tongue in Bulbar Palsy

The tongue in bulbar palsy is characteristically:

Weak.

Wasted or atrophied.

Fasciculating.

Movement of the tongue may be markedly reduced.

The combination of tongue wasting + fasciculations is a classic clue to LMN involvement.

5. Tongue in Pseudobulbar Palsy

The tongue in pseudobulbar palsy is:

Stiff.

Spastic.

Slow-moving.

There are generally no prominent fasciculations because the lower motor neurones themselves remain intact.

Therefore:

Wasted + fasciculating tongue → bulbar palsy.

Spastic tongue without fasciculations → pseudobulbar palsy.

6. Dysarthria

Both disorders can produce dysarthria, but the character of the speech differs.

Bulbar palsy: Speech is flaccid, weak, slurred and often nasal because of weakness of the tongue, palate, pharynx and larynx.

Pseudobulbar palsy: Speech is typically slow, strained and spastic. Older textbooks sometimes describe this as “Donald Duck speech.”

7. Dysphagia

Dysphagia can occur in both conditions.

In bulbar palsy, weakness of the palate, pharynx and larynx can cause:

Choking.

Coughing during meals.

Nasal regurgitation of fluids.

Aspiration.

In pseudobulbar palsy, swallowing is impaired because voluntary control of the swallowing musculature is disrupted by bilateral corticobulbar damage.

Both conditions can therefore cause clinically important aspiration.

8. Nasal Regurgitation

Bulbar palsy: Nasal regurgitation is particularly characteristic because weakness of the soft palate prevents adequate closure of the nasopharynx during swallowing.

Pseudobulbar palsy: Dysphagia occurs, but the classical picture is dominated more by spastic swallowing dysfunction rather than flaccid palatal weakness.

9. Jaw Jerk

The jaw jerk is one of the most useful examination differences.

Bulbar palsy: The jaw jerk is not characteristically exaggerated and may be reduced if the relevant LMN reflex pathway is involved.

Pseudobulbar palsy: The jaw jerk is brisk or exaggerated because of bilateral UMN corticobulbar damage.

Therefore:

Exaggerated jaw jerk → think pseudobulbar palsy.

10. Gag Reflex

Bulbar palsy: The gag reflex may be reduced or absent when the relevant IX/X lower motor pathways are affected.

Pseudobulbar palsy: Bulbar reflexes may be brisk or exaggerated because of loss of descending inhibitory control.

However, the gag reflex naturally varies between individuals, so it should not be interpreted alone.

11. Muscle Wasting

Bulbar palsy: Muscle wasting occurs because the lower motor neurones directly supplying the muscles are damaged.

Pseudobulbar palsy: Marked denervation wasting is not expected because the lower motor neurones remain intact.

This again follows the general rule:

LMN → wasting and fasciculations.

UMN → spasticity and hyperreflexia.

12. Fasciculations

Bulbar palsy: Fasciculations, particularly of the tongue, may be clearly visible.

Pseudobulbar palsy: Fasciculations are generally absent.

A wasted fasciculating tongue should therefore immediately suggest a lower motor neurone bulbar lesion.

13. Emotional Lability

Bulbar palsy: Emotional lability is not a characteristic consequence of the LMN lesion itself.

Pseudobulbar palsy: Emotional lability is characteristic.

The patient may have sudden episodes of uncontrollable:

Laughing.

or

Crying.

This is known as pseudobulbar affect.

14. Causes of Bulbar Palsy

Important causes include:

Motor neurone disease.

Guillain–Barré syndrome.

Other diseases affecting the medullary motor nuclei or lower cranial nerves can also produce bulbar weakness.

Motor neurone disease is particularly important because it may produce both LMN and UMN abnormalities.

15. Causes of Pseudobulbar Palsy

Important causes include:

Bilateral cerebrovascular disease, such as multiple strokes affecting the corticobulbar pathways.

Multiple sclerosis.

Motor neurone disease.

Other disorders producing bilateral corticobulbar tract damage can also cause the syndrome.

16. Motor Neurone Disease Can Cause Both

An important point is that motor neurone disease can produce both bulbar and pseudobulbar features.

This occurs because diseases such as ALS can damage both:

LMNs → bulbar palsy.

and

UMNs → pseudobulbar palsy.

Therefore, a patient with motor neurone disease may have mixed findings.

For example:

Tongue fasciculations → LMN involvement.

Brisk jaw jerk → UMN involvement.

Finding both suggests combined upper and lower motor neurone disease.

17. Bulbar Palsy – Quick Note Form

Lesion: LMN.

Site: cranial nerve nuclei/peripheral lower cranial nerves.

Important nerves: IX, X, XII.

Tongue: wasted, weak and fasciculating.

Speech: weak, flaccid and often nasal.

Swallowing: dysphagia.

Nasal regurgitation: common with palatal weakness.

Jaw jerk: not exaggerated.

Gag: may be reduced.

Emotional lability: not characteristic.

Main causes: motor neurone disease and Guillain–Barré syndrome.

18. Pseudobulbar Palsy – Quick Note Form

Lesion: UMN.

Site: bilateral corticobulbar tracts.

Tongue: stiff/spastic without prominent fasciculations.

Speech: slow, strained and spastic.

Swallowing: dysphagia.

Jaw jerk: exaggerated/brisk.

Bulbar reflexes: may be exaggerated.

Emotional lability: characteristic.

Main causes: bilateral cerebrovascular disease, multiple sclerosis and motor neurone disease.

19. Fastest Examination Distinction

When trying to distinguish the two at the bedside, look particularly at the tongue, jaw jerk and emotional response.

Bulbar palsy:

Wasted fasciculating tongue

↓

LMN

↓

Weak/flaccid speech + dysphagia

Pseudobulbar palsy:

Spastic tongue + brisk jaw jerk + emotional lability

↓

Bilateral UMN corticobulbar lesion

↓

Spastic speech + dysphagia

Key Clinical Differences

Bulbar palsy = LMN.

Pseudobulbar palsy = bilateral UMN.

Bulbar → tongue wasted and fasciculating.

Pseudobulbar → tongue spastic, no prominent fasciculations.

Bulbar → flaccid/nasal dysarthria.

Pseudobulbar → spastic/strained dysarthria.

Bulbar → jaw jerk not exaggerated.

Pseudobulbar → jaw jerk exaggerated.

Bulbar → gag may be reduced.

Pseudobulbar → reflexes may be brisk.

Bulbar → emotional lability not characteristic.

Pseudobulbar → emotional lability characteristic.

Bulbar causes → MND + Guillain–Barré syndrome.

Pseudobulbar causes → bilateral strokes + MS + MND.

Key Clinical Pattern

The easiest memory rule is:

BULBAR = LMN = WASTING

PSEUDOBULBAR = UMN = SPASTICITY

So:

Wasted fasciculating tongue → Bulbar palsy.

Spastic tongue + brisk jaw jerk + emotional lability → Pseudobulbar palsy.