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Flashcards in Motor System Deck (27):
1

Posterior Limb of Internal Capsule

Corticospinal tract

2

Pyramidal decussation

-at level of foramen magnum
-where medulla becomes SC

3

Bell's Cruciate Paralysis

-characterized by midline involvement of the upper portion of pyramidal decussation resulting in paralysis of upper extremity W/O lower extremity involvement
-upper extremity motor fibers in medulla decussation more superior and medial compared to the more inferior and lateral decussation of lower extremity motor fibers
-upper extremity CST fibers are medial in LCST while lower extremity CST fibers assume a more lateral position
-so this palsy may be caused by damage to Odontoid process b/c its proximity of medial decussating arm fibers

4

Corticobulbar fibers

Descend from cortex thru the genu of internal capsule
-decussation in lower pons b/w level of trigeminal and Abducens N
-brainstem LMNs receive some degree of bilateral Innervation from direct or indirect corticobulbar fibers

5

Direct corticobulbar fibers

-terminate upon LMNs of trigeminal, facial, And Hypoglossal motor nuclei
-exert a predominant influence on the fcn of nuclei

6

Lesions of corticobulbar fibers

-lesions of CBF above decussation may result in some contralateral cranial N palsies
-lesions of CBF below decussation may result in some ipsilateral cranial N palsies
-in the first year post stroke, some of these deficits are ameliorated due to varying degree of bilateral Innervation of these nuclei and contributions from corticoreticulobulbar fibers (indirect CBF)

7

Indirect corticobulbar fibers

-referred to corticoreticulobulbar fibers b/c of bilateral course and termination in reticular formation surrounding brainstem motor nuclei
-descending influences are relayed on to respective LMNs
-fibers do not affect the LMNs as strongly as the direct corticobulbar fibers, but they may play a role in recovery from infarction involving the direct corticobulbar fibers

8

Aberrant corticobulbar fibers

-these originate in frontal and occipital eye fields and descend in the dorsal aspect of midbrain adjacent to central gray
-separation of these fibers from corticospinal and corticobulbar fibers makes it difficult to destroy all 3 in same lesion
-terminate in superior colliculus and PPRF as part of Oculomotor system
-drive volitional and nonvolitional eye movements

9

Supra nuclear Facial Palsy

-caused by unilateral lesions of corticobulbar fibers above the level of facial nucleus
-result in paralysis of contralateral lower quadrant of face
-upper quadrant of face is unaffected by unilateral lesions of corticobulbar fibers due to the bilateral Innervation from the facial nucleus

10

Extrapyramidal System

-involved in crude, stereotyped, associative movements of axial and proximal limb musculature such as swinging arms while walking
-initiates movement patterns thru its complex sub cortical loops
-plays a role in facilitation of motor centers and activation of reflex arcs
-primary influence is on the primary and pre motor cortices

11

Principal Subcortical Loop

All areas of cortex-->striatum made up of caudate and putamen-->globus pallidus and substantia nigra-->ventral lateral and ventral anterior

12

Dorsal division of ansa lenticularis

-called lenticular fasciculus
-pallido-thalamus fibers join with fibers from ventral division to form the thalamic fasciculus
-projections are shared in common with those fibers from dentato-thalamic and dentato-rubro-thalamic pathways

13

Ventral division of ansa lenticularis

-most of fibers in the ansa lenticularis are pallido-thalamic fibers which join with the lenticular fasciculus to form the thalamic fasciculus

14

Nigro-thalamic fibers or Striatonigral

-connections of substantia nigra
-non dopaminergic fibers that originate from pars reticularis substantia nigra
-terminate in VA and VL thalamic nuclei
-fibers from globus pallidus and substantia nigra DO NOT terminate in same areas of VL and VA thalamic nuclei
-important in stereotaxic surgery for Parkinson's Dz

15

Nigro-Striatal Fiber

-connection of substantia nigra
-dopaminergic fibers that originate in pars compacta of substantia nigra
-terminate in caudate and putamen--striatum
-neurons in this area of the substantia nigra are destroyed in Parkinson's Dz
-destruction of inhibitory, GABA nergic fibers in these fibers are in Huntington's Dz

16

Pallidal and Subtantia Nigra Loops

-cortical and Subcortical feedback loops play important roles in initiating motor movement patterns and integrating them with cerebellum, cerebral cortex, and limbic system
-fibers are inhibitory upon these specific motor thalamic nuclei

17

Lesions of extrapyramidal system

-unilateral lesions exhibit contralateral deficits
-bilateral lesions are common and are due to NT imbalances or neuronal dysfunction

18

Parkinson's Disease

-Subcortical degeneration disorder involving substantia nigra, globus pallidus, upper brainstem nuclei, and postganglionic sympathetic neurons
-dz may be brought on by:
1. Post encephalitic syndrome
2. Arteriosclerotic Parkinsonism
3. Sequelae of certain tranquilizer or antipsychotic drugs

19

Postencephalic syndrome

-one of the causes of Parkinson's
-involves substantia nigra and reticular formation
-affects younger ppl
-likely to produce mental changes
-often seen on one side
-pt may have oculogyric crisis of eyes and head in which they appear to be forced upward for minutes w/o loss of consciousness

20

Arteriosclerotic Parkinsonism

-cause of Parkinson's Dz
-pts usually present with history of TIA and abrupt onset of ischemic episodes
-in older individuals, dementia may occur
-infarction may affect the substantia nigra, nigrostriatal pathways, basal ganglia
-prognosis is poor with a high risk of additional cerebral and myocardial infarction

21

Sequelae of certain tranquilizer or antipsychotic drugs

-cause of Parkinson's
-over titration of certain neuroleptic drugs may result in tardive dyskinesia
-this is a repetitive involuntary licking and smacking movements of lips
-always a result of drugs and may be present in other motor disorders
-may be reversible
-if medication is not adjusted, effects are irreversible

22

S/S of Parkinson's Disease

-dyskinesia, tremor, and rigidity are major symptoms

1. Bradykinesia--difficulty initiating movement
-difficulty initiating motor movement patterns especially gait patterns
2. Tremor during rest--may be in jaw and upper extremity
-slow tremor that is absent or reduced during movement
3. Rigidity--most disabling, inc resistance of extremities to passive movement in all directions
-may be initially unilateral and progress to other side
-limbs may exhibit cogwheel, knife clasp, or lead pipe rigidity
4. Absence of facial expression--masked face
-may stare with infrequent blinking--reptilian gaze
-positive glabellar reflex--tapping on pt's forehead with finger results in no attenuation of pt's repetitive blinking
5. Postural embarrassment
6. Cognitive changes--deterioration of memory, obsessions

23

Huntington's Chorea

-autosomal dominant motor disorder which has localized on chromosome 4
-common features include dementia, chorea, and behavioral disturbances
-deteriorates and dies 10-15 yrs after onset

24

S/S of Huntington's Dz

1. Choreiform movements--sudden, irregular, involuntary, jerky, purposeless movements
-pt may develop severe dementia--choreiform movements are debilitating but the dementia is more limiting
-principal areas of degeneration are corpus striatum and cerebral cortex--symptoms due to excessive dopaminergic influence in degenerated striatum or loss of inhibition from GABAnergic neurons

25

S/S and degenerating structure of Parkinson's Dz

-S/S: bradykinesia, tremor during rest, rigidity, masked face, glabellar reflex, postural embarrassment, autonomic effect, cognitive changes

-degeneration of: substantia nigra, globus pallidus, brainstem reticular formation and postganglionic sympathetic neurons

26

S/S and generating structure of Huntington's Chorea

-S/S: Onset age 30-40 yo
-choreiform movements, severe dementia, choreoathetosis, behavioral disturbances

-autosomal dominant disorder--chromosome 4

-denigrating structure: corpus striatum, cerebral cortex results in excessive dopaminergic influence in degenerated striatum or loss of inhibition from GABAnergic neurons of STRIATONIGRAL pathway

27

Genu of internal capsule

corticobulbar fibers