Bulbar Versus Pseudobulbar Palsy
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Direct answer
Bulbar palsy and pseudobulbar palsy both cause dysarthria and dysphagia, but bulbar palsy is a lower motor neuron lesion of the cranial nerve nuclei, while pseudobulbar palsy is bilateral upper motor neuron damage to the corticobulbar pathways. The classic bedside difference is a wasted, fasciculating tongue with a normal or reduced jaw jerk in bulbar palsy, versus a spastic tongue, brisk jaw jerk and emotional lability in pseudobulbar palsy.
What you must remember
- Bulbar palsy: lower motor neuron loss from the nuclei of cranial nerves IX, X and XII, causing flaccid dysarthria, nasal regurgitation and dysphagia.
- Tongue: wasting and fasciculations in bulbar palsy; in pseudobulbar palsy the tongue is spastic and slow but not wasted.
- Jaw jerk: brisk in pseudobulbar palsy because corticobulbar inhibition is lost, and normal or reduced in bulbar palsy.
- Emotional lability: pathological laughing or crying is the hallmark of pseudobulbar palsy and is seen in stroke, motor neuron disease and multiple sclerosis.
- Gag reflex: reduced in bulbar palsy because the glossopharyngeal and vagal arcs are damaged, but normal or exaggerated in pseudobulbar palsy.
- Motor neuron disease: amyotrophic lateral sclerosis combines upper and lower motor neuron signs and often starts with bulbar symptoms, which carry a poorer prognosis.
- Bilateral lacunar strokes: a common vascular cause of pseudobulbar palsy, sometimes with a stepwise course.
A bedside sequence to separate the two
The two syndromes sound alike on the telephone but differ in their lower and upper motor neuron signs. A structured examination of speech, tongue, reflexes and affect separates them within a few minutes.
- Listen to the speech: Flaccid, nasal dysarthria with a breathy quality suggests lower motor neuron bulbar weakness, while strained, slow and spastic speech suggests pseudobulbar involvement.
- Inspect the tongue: Wasting, fasciculations and a flaccid tongue point to bulbar palsy, whereas a small, stiff, slow and spastic tongue without wasting suggests bilateral upper motor neuron lesions.
- Test the jaw jerk: Placing a finger on the chin and tapping it should give a normal or reduced response in bulbar palsy and a brisk response in pseudobulbar palsy.
- Check the palate and gag: Palatal elevation and the gag reflex are reduced in bulbar palsy, whereas the gag is normal or exaggerated in pseudobulbar palsy.
- Look for emotional lability: Ask about crying or laughing out of proportion to the event, which indicates pseudobulbar affect and supports bilateral central disease.
- Scan the rest of the neuraxis: Check limb tone, reflexes and fasciculations elsewhere, because amyotrophic lateral sclerosis combines both patterns and needs electrodiagnostic confirmation.
Where the exam tries to catch you
Most traps here come from reading one feature, such as slurred speech, as if it defined the syndrome.
- Trap: Attributing emotional lability to bulbar palsy Correct: lability points to pseudobulbar palsy, and a combined picture of wasting and lability suggests amyotrophic lateral sclerosis or bilateral disease.
- Trap: Calling a spastic tongue bulbar because the speech is slurred Correct: a pseudobulbar tongue is spastic without wasting, so inspect for atrophy and fasciculations rather than judging speech alone.
- Trap: Thinking a brisk jaw jerk rules out motor neuron disease Correct: a brisk jaw jerk indicates an upper motor neuron component, which fits amyotrophic lateral sclerosis rather than excluding it.
- Trap: Assuming all dysarthria with dysphagia is a brainstem stroke Correct: bilateral lacunar or cortical lesions cause pseudobulbar palsy without brainstem involvement, so the cortical pathways are checked.
Frequently asked questions
What is the difference between bulbar and pseudobulbar palsy?
Bulbar palsy is a lower motor neuron lesion of the brainstem nuclei of cranial nerves IX, X and XII, causing flaccid, nasal dysarthria with a wasted, fasciculating tongue. Pseudobulbar palsy is bilateral upper motor neuron damage to corticobulbar pathways, giving spastic speech, a brisk jaw jerk and emotional lability. Examination answers hinge on the tongue and jaw jerk signs.
Why is the jaw jerk exaggerated in pseudobulbar palsy?
The jaw jerk is exaggerated in pseudobulbar palsy because bilateral corticobulbar lesions remove inhibitory input to the trigeminal motor nucleus. This is an upper motor neuron sign, which is why the reflex is brisk rather than reduced. A brisk jaw jerk therefore supports bilateral central disease.
Which motor neuron disease commonly presents with bulbar onset?
Amyotrophic lateral sclerosis commonly presents with bulbar onset, with dysarthria, dysphagia and tongue fasciculations as early features. Bulbar onset is generally associated with a poorer prognosis than limb onset. Diagnosis needs both upper and lower motor neuron signs across regions, supported by electrodiagnostic testing.
What causes pseudobulbar affect?
Pseudobulbar affect, with inappropriate crying or laughing, arises from bilateral damage to corticopontine-cerebellar pathways that regulate emotional expression. It is seen in stroke, amyotrophic lateral sclerosis, multiple sclerosis and other bilateral central disorders. Recognising it prevents the symptoms from being misattributed to a primary mood disorder.
Which cranial nerves are damaged in bulbar palsy?
Bulbar palsy involves the lower cranial nerves IX (glossopharyngeal), X (vagus) and XII (hypoglossal), either at their brainstem nuclei or along their peripheral course. The result is dysarthria, dysphagia, palatal weakness and tongue atrophy. Lower motor neuron signs in these nerves distinguish bulbar palsy from pseudobulbar palsy.