bulbar palsy is lower motor neuron weakness of the muscles innervated by the cranial nerves IX, X and XII, while pseudobulbar palsy is an upper motor neuronal weakness of these muscles
mixed nerve, including the afferent fibres for the gag reflex, and somatic sensory and bitter/sour taste sensation from the posterior one-third of the tongue, parasympathetic inputs to parotid gland, etc.
the only motor component is to stylopharyngeus muscle
damage can thus cause loss of taste to post. third tongue and impaired swallowing
innervates all the extrinsic and intrinsic muscles of the tongue, except for the palatoglossus which is innervated by the vagus nerve
isolated damage to the nerve is rare but may be caused by:
tumours, wounds, sarcoid, multiple sclerosis (MS), presence of an ectatic vessel in the hypoglossal canal
vertebrobasilar stroke may affect both hypoglossal nerves and facial and trigeminal nerves resulting in tight oral musculature, dysarthria, difficulty eating and chewing
if the damage is to the nerve itself (a lower motor neuron lesion), the half wasted, fasculating tongue will curve toward the damaged side, owing to weakness of the genioglossus muscle of affected side
if the damage is to the nerve pathway (an upper motor neuron lesion) the tongue will curve away from the side of damage, due to action of the affected genioglossus muscle, and will occur without fasciculations or wasting
these conditions result in difficulty with chewing, talking, and swallowing and may also cause drooling
afebrile patient with signs and symptoms of acute progressive bulbar palsies and descending neuromuscular paralysis should be highly suspected of having botulism
Brown–Vialetto–Van Laere syndrome
rare, bulbopontine paralysis, usually preceded by progressive bilateral nerve deafness;
weakness is in the distribution of motor cranial nerves III, and VII to XII
Worster-Drought syndrome or congenital suprabulbar paresis
selective weakness of the orbicularis oris muscle, tongue and soft palate leading to dysarthria and drooling
some complain of exercise-induced muscle cramps and hand tremors several years before weakness develops
proximal muscles are affected first, followed by bulbar involvement, which may become marked and facial fasciculations with moderately raised CK levels