Abiesha Smith Neuroanatomy Wednesday, March 1st, 2023
HOMEWORK FIVE
BELL’S PALSY AND STROKE
QUESTION:
1. EXPLAIN THE DIFFERENCES BETWEEN BELL’S PALSY AND A STROKE
Both Bell’s Palsy and a Stroke are medical conditions often accompanied by
facial paralysis of varying degrees and regions. But whilst the two are non-
mutually exclusive, they are not identical and cannot be substituted for the
other. Bell’s Palsy, also know as Idiopathic Peripheral Facial Paralysis, is a
deterioration of ipsilateral facial muscles that results from a disruption in
function/injury of the facial nerve after said nerve exits the cerebral area
known as the pons. In Bell’s Palsy, not only could the facial nerve become
injured just after leaving the pons but could damage could also occur in
branches of the facial nerves, resulting in a slew of varying physiological
ramifications. If the muscles of the forehead (upper face) and the lower face
—all of which are innervated by the facial nerve—are affected, full paralysis
or weakness of that particular (ipsilateral) side of the facial muscles being
innervated would occur (the characteristic droopy facial expression for which
Bell’s Palsy is known): additional complications include smoothness in the
forehead, retinal, and nasal regions of the face. A Stroke, on the other hand,
is a disruption in function/deterioration of contralateral facial muscles that
results from a lesion in the facial motor nucleus and damage to upper motor
neurons. In a Stroke, when a lesion of upper motor neurons—originating from
the right side of the cerebral cortex—occurs, the lower left side of the face is
affected due to the contralateral synapsing of said upper motor neurons to
the lower motor neurons responsible for innervation of facial muscles on the
lower left side of the face. What separates a Stroke from Bell’s Palsy is a lack
of physiological damage to the upper face in a Stroke: the forehead region,
in a Stroke, is unaffected if the ipsilateral innervation of its muscles (from the
ipsilateral cerebral cortex) is also unaffected by the lesion. As such, where
ipsilateral damage to the upper and lower faces are characteristic of Bell’s
Palsy—due to damage of any region of the facial nerve, its canals, and
innervated lower motor neuron regions, thereof—a Stroke’s paralysis, be it
upper or lower facial regions and left/right side of the face, will depend on
the upper motor neurons being affected and whether said disruptions are
either contralateral, ipsilateral, or both.
