Bell's palsy is lower motor neurone paralysis of seventh cranial (facial) nerve of unknown cause.
The involvement of both upper and lower parts of the face distinguishes lower motor neurone paralysis from supranuclear lesions.
Differential Diagnosis of Bell's Palsy Infection Otitis media Mastoiditis Other structure directly involving or compromising lower motor neurone of facial nerve Herpes zoster of geniculate ganglion (Ramsay Hunt syndrome) Other herpetic infection of facial nerve Lyme disease
It is a progressive disease attacking the upper and lower motor neurones leading to weakness and wasting of muscles, causing increased loss of mobility and difficulties with swallowing, breathing and speech.
Amyotrophic Lateral Sclerosis (ALS) is the most common form and involves both the upper and lower motor neurones.
Progressive Bulbar Palsy (PBP) affects about 25 percent of sufferers and also involves both the upper and lower motor neurones but is characterised by dysarthria and dysphagia, and predominantly affects older women.
Progressive Muscular Atrophy (PMA) is the least common form, affecting about 10 percent of sufferers and predominantly affects the lower motor neurones, causing muscle weakness and wasting, weight loss and fasciculation.
ALS is the most common motor neurone disease resulting from progressive degeneration of both upper and lower motor neurones which lead to severe muscle weakness and wasting, followed by paralysis and death, generally caused by respiratory failure.