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Bulbar palsy refers to impairment of function of the cranial nerves IX, X, XI and XII, which occurs due to a lower motor neuron lesion either at nuclear or fascicular level in the medulla oblongata or from lesions of the lower cranial nerves outside the brainstem.
In contrast, pseudobulbar palsy describes impairment of function of cranial nerves IX-XII due to upper motor neuron lesions of the corticobulbar tracts in the mid-pons. For clinically evident dysfunction to occur, such lesions must be bilateral as these cranial nerve nuclei receive bilateral innervation.
Bulbar palsy is an assortment of signs and symptoms, not the name of a precise disease.
- Genetic: Kennedy's disease, acute intermittent porphyria
- Vascular causes: medullary infarction
- Degenerative diseases: motor neuron disease (amyotrophic lateral sclerosis), syringobulbia
- Inflammatory/infective: Guillain–Barré syndrome, poliomyelitis, Lyme disease
- Malignancy: brain-stem glioma, malignant meningitis
- Toxic: botulism, bark scorpion venom (Centruroides sp.), some neurotoxic snake venoms
- Autoimmune: myasthenia gravis
- dysphagia (difficulty in swallowing)
- difficulty in chewing
- nasal regurgitation
- slurring of speech
- difficulty in handling secretions
- choking on liquids
- dysphonia (defective use of the voice, inability to produce sound due to laryngeal weakness)
- dysarthria (difficulty in articulating words due to a CNS problem)
- Nasal speech lacking in modulation and difficulty with all consonants
- Tongue is atrophic and shows fasciculations.
- Dribbling of saliva.
- Weakness of the soft palate, examined by asking the patient to say aah.
- The jaw jerk is normal or absent.
- The gag reflex is absent.
- In addition, there may be lower motor neuron lesions of the limbs.
The ocular muscles are spared and this differentiates it from myasthenia gravis.
Pseudobulbar palsy is a clinical syndrome similar to bulbar palsy but the damage is located in upper motor neurons, that is the nerve cells coming down from the cerebral cortex innervating the motor nuclei in the medulla. This is usually caused by stroke.