Motor Tracts Flashcards
what would a lesion of the corticobulbar tract above the decussation may result in what?
contralateral supranuclear facial palsy
what does supranuclear facial palsy present as?
Paralysis of the lower quadrant of the face ( they can’t smile) (contralateral side of lesion)
where do corticobulbar fibers originate?
in the head region of the precentral gyrus
what part of the internal capsule do the corticobulbar course through?
the genu
where does the corticobulbar tract decussate?
in the lower pons
what do unilateral lesions of the corticobulbar tract below the decussation result in?
ipsilateral cranial nerve palsies
what is apraxia and what is an example?
when a patient cannot perform the motor sequence correctly (brush hair)
what are lesions sites that would result in apraxia?
left parietal lobe and premotor cortex
what is agnosia?
when a patient can perform a movement but does not know their right from their left
what is automatic voluntary dissociation?
when a patient doesn’t know their left from their right, but does a task using their dominant hand
what results from ischemia within the territory supplied by the perforating branches of the MCA or ICA?
lenticulostriate infarcts
where does the corticospinal pathway originate?
large pyramidally-shaped neurons (cells of Betz) located in the primary motor and premotor cortices
where do 85-90% of the corticospinal fibers decussate?
in the lower medulla at the pyramidal decussation
what do the corticospinal fibers become after decussation?
the lateral corticospinal tract (LCST)
what do the uncrossed fibers of the corticospinal tract continue as?
anterior corticospinal tract (ACST)
where in the spinal cord does the LCST descend?
in the lateral funiculus
where do most descending motor fibers terminate?
in lower motor neuron pools
what do unilateral lesions of the CST result in?
contralateral spastic hemiplegia or spastic hemiparesis (muscle weakness or stiffness on one side)
what do unilateral lesions of the LCST result in?
ipsilateral paralysis or paresis of the distal limb musculature innervated by those spinal segments below the level of the lesion
where are lower motor neurons found?
in the anterior horn of the spinal cord
what do lesions of the LMNs result in?
flaccid paralysis (muscle is completely limp), areflexia, atonia, atrophy, fasciculations
what are the signs and symptoms of an UMN lesion?
varying degrees of spastic paresis (weakness) of the axial and proximal limb musculature, hypertonia, hyperreflexia, + babinski sign, clonus, rigidity
what is ideational apraxia?
it is a loss of the ability to formulate the ideational concepts necessary to perform a motor activity
what are the fibers responsible for a patient’s recovery after a stroke?
corticoreticulobulbar fibers
ideomotor apraxia is specifically associated with lesions of what?
the supramarginal gyrus of the dominant hemisphere
what do the corticobulbar fibers innervate?
the somatic motor nuclei of the brainstem
the facial motor nucleus is divided into two parts. What are they?
an anterior portion of the facial nucleus and a posterior portion of the facial nucleus
the anterior portion of the facial nucleus receives corticobulbar fibers from where?
the contralateral cortex
what does the anterior portion of the facial nucleus innervate?
the muscles of the lower quadrant of the face
the posterior portion of the facial nucleus receives corticobulbar fibers from where?
from both hemispheres of the cortex
what does the posterior portion of the facial nucleus innervate?
the upper quadrant of the face
where are the most common sites for lesions causing supranuclear facial palsy?
in the facial region of the motor cortex and the genu of the internal capsule
what does a central lesion of the facial nerve result in?
Bell’s Palsy
unilateral lesion of the corticobulbar fibers to the facial nucleus results in what?
paralysis of the contralateral lower quadrant of the face
A lesion of the CST resuts in what?
contralateral spastic hemiplegia
