Motor Cortex And Pyramidal Motor System Flashcards
Corticospinal and corticonuclear projections through the corona radiate motor
Descend through internal capsule
Descends through cerebral peduncle, basilar pons, pyramids, forms AL corticospinal tracts
What is the order from front to back of the different motor cortex
- frontal eye fields
- Premotor area and supplementary motor area
- primary motor
Is the cingulate gyrus motor
No
What runs through the pyramid
Corticospinal system
Corticonuclear system,
Cortico-pontine projections
Corticonuclear system, UMN projections to:
LMN in brainstem
-3-12
Postcentral gyrus map
Low extremity: medially
Upper extremity: laterally
Corticospinal system
- Cerebral peduncle
2 basilar pons - Pyramid
- Pyramidal decussation
Anterior limb of the internal capsule
Runs between the caudate nucleus medially and putamen and globus pallidus laterally
Posterior limb of the internal capsule
Runs between thalamus medially and putamen and globus pallidus laterally
What does the posterior limb of the internal capsule represent
Upper extremity
Trunk
Lower extremity
Where is the face represented on the internal capsule
Genu
What kind of info is in the internal capsule
Descending
What part of the brainstem does the corticospinal system go through
Ventral brainstem
Supplementary motor cortex
- active during sequence of finger flexion
- active during mental rehearsal of sequencing of finer flexion
Guides motor cortex and planning movements
Premotor cortex function
Motor planning
Input to premotor cortex
Mostly sensory info
- proprioception from primary somatosensory cortex
- body awareness from 2ndry somatosensory cortex
- motor related nuclei of the thalamus
- complex spatial posteiror parietal cortex
Projections from premotor cortex
To primary motor cortex, anteiror horn, reticulospinal system
Deficits in the premotor cortex
Apraxia
Impairment in complex movements or sequences of movements, especially learned movements
Apraxia
When the premotor cortex is damaged
Selective damage does NOT produce significant weakness or paralysis
Supplementary cortex function
Motor planning and execution
Input to the supplementary cortex
Motor prefrontal and parietal association cortex
- visual and somatosensory info from parietal association cortex
- prefrontal input probably related to learned movements
- motor related nuclei of the thalamus-motor coordination by cerebro-cerebellum system and basal ganglia
Projections of the supplementary cortex
To primary motor cortex, anterior horn, reticulospinal system
Deficits when the supplementary cortex is damaged
Apraxia
Where are the frontal eye fields
Overlaps with the premotor cortex in middle frontal gyrus
Where do the frontal eye fields project to
Tract of nuclei of CN 3, 4, 6 to mediate voluntary eye movement in all directions
Circuit for voluntary conjugate eye movements: UMN are in the frontal eye field
-FEF corticonuclear projections are bilateral to CN3 and CN6 nuclei. FEF corticonuclear projections are unilateral to contralteral abducens nucleus. FEF drives lateral conjugate gaze toward opposite side: left FEF=right ward gaze. So, unilateral FEF damage causes eyes to deviate toward the lesioned size. Left FEF lesion=left ward deviation
How do frontal eye fields drive lateral gaze
Opposite side: left FEF=right-ward gaze
Unilateral FEF damage
Causes eyes to deviate toward the lesioned side
Left FEF lesion=left ward deviation
If there is a problem with FEF how can the eyes still move laterally?
VOR reflex
Voluntary suppression of urinary voiding
Cortical micturition center
Prefrontal cortex inhibits the brainstem pathway that promotes voiding. Neurons in the midline part of the superior frontal gyrus send descending excitatory projections to brainstem interneurons, whihc then inhibit the pontine micturition center.
Frontal type incontinence
- bilateral damage causes incontinence
- unilateral damage effects are variable, some weakness/incontinence can occur
- inability to stop urination, complete reflex voiding occurs
- may also lack awareness of deficit and emotional reaction to it
- all reflex voiding mechanisms are intact, so absence of (detrusor-sphincter days-synergia, urge incontinence, incomplete voiding)
What is responsible for urinary storage?
Sympathetic NS
Inhibits de trusts
Activates internal sphincter
MCA infarct would affect what
All structures in the motor cortex all the way to the distal arm
MCA superior division territory deficits
Premotor cortex: apraxia
Frontal eye field: gaze deviation
Broca’s area: language output
What supplies the dorsolatral parts of frontal, parietal, and cingulate gyrus
ACA
What is the cingulate gyrus supplied by
Pericallosal branch of ACA
What is the superior frontal gyrus supplied by
Callosomarginal branch of ACA
Callosomarginal branch occlusion
Leg portion of primary motor cortex, entire supplementary motor cortex, cortical micturition center
What are some areas that are possible sites of disruption due to a watershed
Premotor cortex (MCA superior territory), supplementary motor cortex (ACA territory), micturition inhibitory area (ACA territory), frontal eye fields (MCA superior territory)
Unilateral ACA stem occlusion
-left distal ACA “steals” collateral flow from the right ACA
-potentially insufficient cerebral blood flow through both ACAs
-potentially bilateral deficits, more severe on side of occlusion
-f/u: unilateral deficits due to infarct on the side of occlusion, non-occluded side recovers, deficits resolve.
Can have frontal type incontinence
ACA-MCA watershed territory infarcts motor system deficits
- primary motor: variable outcome-hip, trunk, proximal arm weakness
- premotor: apraxia, unless primary cortex also damaged (weakness masks it)
- FEF: voluntary lateral age deficits, ipsilateral deviation of forward gaze
Primary motor cortex deficit
Spastic paresis/paralysis
Premotor cortex deficit
Apraxia, bu not weakness (if primary is spared)
Supplementary motor cortex deficit
Apraxia but no weakenss ( if primary is spared)
Frontal eye field deficit
Horizontal gaze palsy, eyes deviant toward lesioned side
Brock’s areadeficit
Brocas aphasia
When could you see frontal type incontinence
Bilateral damage to MCA
What is the internal capsule blood supply
Lenticolostriate arteries and anterior choroidal artery
Lesion to the right internal capsule or complete unilateral damage to right corticospinal tracts in brainstem
- hemiplegic gait
- lower face weakness in ipsilateral side of hemiplegia
- slight head deviation due to weak sternocleidomastoid
Patient compensates for weakness in leg by using trunk postural movements to passively swing the affected leg around to a forward position
Hemiplegic gait
Danger of growing intracranial mass
Herniated can induce reflex posturing in unconscious patients
Decortate (flexor-extensor) posturing/rigidity in unconscious patient
Supratentorial mass abolishes cortical suppression of reflex posturing
- midbrain projections to spinal cord LMNs mediate tonic arm flexion, enhanced by cerebellar influence on midbrain
- this gets knocked out
Decerebrate (extensor) posturing/rigidity
- trans-tentorial mass or herniation compresses midbrain and suppresses the midbrain arm flexion pathway
- descending extensor systems are still intact
What kind of disorder is cerebral palsy
Acquired, congenital
Distribution of cerebral palsy
Diffuse
What is cerebral palsy cause by
Transient hypoxia/ischemia at birth
Other possibilities are intracranial hemorrhage, CNS viral infection
Hallmark presentation of cerebral palsy
- variable degree of weakness and impaired motor coordination
- increased muscle tone in some muscles-typically hyper-flexion
- reduced muscle tone and movement
- dyskinetic: involuntary movements
ALS
UMN and LMN neurodegeneration
