Brainstem Motor Pathways-Wilson Flashcards
Describe the following for upper motor neuron disease:
- tone
- reflexes
- Babinski
- clonus
- muscle bulk
- fasciculations
spastic paralysis greater in flexors of arms and extensors of legs; when you move a joint you get resistance and that is dependent on the velocity of the movement (slow movement not a lot of resistance; fast movement produces lots of resistance)
accentuated stretch reflexes
present Babinski
clonus frequently present
slight atrophy of disuse only, late
no fasciculations
Describe the following for lower motor neuron disease:
- tone
- reflexes
- Babinski
- clonus
- muscle bulk
- fasciculations
flaccid tone
normal, decreased, absent reflexes
absent Babinski
absent clonus
marked atrophy of muscles
fasciculations present
What happens if there is lesion in the lateral corticospinal system at the pyramids?
- produces paresis and a loss of voluntary movements, especially at the digits
- positive Babinski sign
- decreased cremaster reflex
- produces hypotonia (loss of tonic stimulatory effect)
- does NOT produce spasticity
What happens if there is lesion in the anterior corticospinal system at the pyramids?
- manipulation of objects normal (10% do not cross and it’s only change of posture, lateral CST is for manipulation of digits)
- frequent failing
- lost of righting reflex
- hypotonicity
Why does a lesion to the lateral corticospinal tract in the pyramids NOT produce spasticity?
you get other parallel pathways in addition to the corticospinal tract that go to the brainstem, its when you lose signals going to the brainstem, that results in spasticity; at this stage all the corticofugal fibers (going to the brainstem) have been given off so no effect on the corticoreticular or corticorubral pathways, so you won’t have spasticity
Are lesions of the corticospinal tract clean?
NO
you get other parallel pathways like corticoreticular and corticorubal neurons
What is the difference between rigidity and spasticity?
rigidity: increase in extensor and flexor muscle tone which can demonstrate clinically through resistance to passive stretch; independent of velocity; due to increase in tonic reflex of muscle spindle
spasticity: increase of muscle tone that is velocity dependent; the faster you stretch the muscle the more resistance there is; greatest in flexors of upper limb and extensors of lower limb; exaggerated deep tendon reflexes and clonus (because of increase gain and sensitivity in the phasic phase of the tendon reflex–>hyperreflexia )
What are the two types of rigidity? Characterize them both.
lead-pipe: resistance constant throughout the range of movement
cogwheel (Parkinson’s disease) or clasp-knife (pyramidal tract): increase in passive resistance that abruptly decreases, usually at the end of the an excursion; resistance-release jerking pattern
Where is spasticity greatest during upper motor neuron lesions?
greatest in the flexors of the arm and extensors in the legs
What are the major efferents from motor cortical areas?
- basal ganglia
- cerebellum via basilar pons
- indirect motor pathways to the spinal cord
What are the indirect motor pathways to the spinal cord?
- Red nucleus
- Pontine reticular formation
- medullary reticular formation
- vestibular nuclei
Spasticity results from disinhibition of reticular and brainstem nuclei, and damage of what parts of cortex?
non-pyramidal parts of the cortex
Relate the activity of motor areas of the brainstem during excessive muscle tone.
the motor areas of the brainstem become overactive resulting in excessive muscle tone
Cortex control of motor activity through corticofugal connections is direct or indirect?
indirect
brainstem modulates the reflexive activity of the spinal cord
Depending on the stimulus under a certain context, you can have different motor responses.
reflexes can change, sometime they are operational and sometimes they are not
Rexed Lamina IX consist of what two distinct groups of motor neurons that innervate what muscles?
medial group- axial musculature
lateral group: appendicular musculature (cervical and lumbosacral enlargement)
Where is the lateral descending motor system that controls the lateral motoneurons of lamina IX located? Which muscles do these neurons innervate?
- posterolateral funiculus
- innervate appendicular musculature
Where is the medial descending motor system that controls the lateral motoneurons of lamina IX located? Which muscles do these neurons innervate?
anteromedial funiculus (medial motor pathway extends slightly laterally and so anterolateral funiculus)
axial musculature and some muscles of the shoulder girdle
Describe the projection of lateral and medial motor system pathways.
Lateral Pathway:
- contralateral
- lateral ventral horn
- limbs and distal musculature
Medial Motor System (anteromedial funiculus)
- bilateral
- medial ventral horn
- axial and girdle musculature
Medial Motor System (anterolateral funiculus)
- unilateral (ipsilateral)
- intermediate ventral horn
What are the spinal segments and muscles of the medial descending pathway besides the motor neurons in Rexed lamina IX?
- will synapse on interneurons in Rexed lamina VIII activating long propriospinal neurons that will go to medial motor neurons pools
- proximal and extensor muscles (most important)
What are the spinal segments and muscles of the lateral descending pathway besides the motor neurons in Rexed lamina IX?
- will synapse on interneurons in Rexed lamina VII activating short propriospinal neurons (possible to move one limb without having to move the other limb unlike axial musculature in which both sides need to move) that will go to lateral motor neuron pools
- distal and flexor muscles (most important)
What are the major lateral cortical descending pathways?
lateral corticospinal tract
rubospinal tract coming from the red nucleus
medullary (lateral) reticulospinal tract
What are the major anterior cortical descending pathways?
-anterior corticospinal tract
tectospinal tract: involves the superior colliculus; coordinates head and eye movements to look at objects in lateral gaze
pontine (medial) reticulospinal tract