- Bulbar palsy is a lower motor neuron palsy that affects the nuclei of the IXth, Xth, XIth, and XIIth cranial nerves.
- Pseudobulbar palsy is an upper motor neuron palsy that affects the corticobulbar tracts of the Vth, VIIth, IXth, Xth, XIth, and XIIth cranial nerves.
Bulbar palsy
Etiology
Pathophysiology
- Bilateral damage or injury of the nerve nuclei of cranial nerves IX, X, XI, and XII
- Since the cranial nerve nuclei in the brain stem are paired, unilateral lesions are often asymptomatic.
- Lower motor neuron palsy of the respective muscles
Clinical features
- Facial expression: normal
- Sparing of the VIIth cranial nerve nucleus
- Speech: nasal
- Due to paresis of the palate as well as of the tongue and lips
- Dysphagia, drooling, nasal regurgitation
- Tongue
- Wasting
- Fasciculations
- Inability to protrude the tongue
- Palatal movement: absent
- Gag reflex: absent
- Jaw jerk: normal
- Emotions not affected
Pseudobulbar palsy
Etiology
Pathophysiology
- Bilateral damage or injury of corticobulbar tracts to nerve nuclei of cranial nerves V, VII, IX, X, XI, and XII
- Note that the cranial nerves V and VII are involved in pseudobulbar palsy, but not in bulbar palsy.
- Upper motor neuron palsy of the respective muscles
Clinical features
- Facial expressions: absent (expressionless face)
- Due to VIIth nerve involvement
- Speech: spastic dysarthria (husky, nasal voice)
- Difficulty in chewing
- Vth nerve palsy → paralysis of the muscles of mastication
- Dysphagia, drooling, and nasal regurgitation
- Tongue
- Spastic, pointed
- Difficulty in tongue protrusion due to spasticity
- No wasting/fasciculations
- Palatal movement: absent
- Gag reflex: brisk (exaggerated)
- Jaw jerk: exaggerated; clonic
- Upper motor neuron palsy of Vth cranial nerve → exaggerated jaw jerk.
- Emotional incontinence (pseudobulbar affect)
- Disruption of central serotonin and dopamine pathways → social disinhibition → uncontrolled and/or mood-incongruent laughing and crying