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Neuro Exam I > Upper Motor Neurons: Primary Lateral Sclerosis > Flashcards

Upper Motor Neurons: Primary Lateral Sclerosis Flashcards

1
Q

each lobe of the cerebral cortex is defined by what fissures / sulci?

A
  • frontal lobe: anterior to central sulcus & superior to lateral fissure
  • parietal lobe: posterior to central sulcus & anterior to parietooccipital fissure, & superior to lateral fissure
  • temporal lobe: anterior to parietoccipital fisure & inferior to latearl fissure
  • occipital lobe: posterior to parietoccipital fissure
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2
Q

the frontal lobe can be subdivided into what gyri?

what forms these subdivisions?

A
  • on each side, two sulci run perpendicular to the central sulcus: the inferior frontal sulcus & superior frontal sulcus. this devides the frontal lobe - from medial to lat:
    • superior frontal gyrus
    • middle frontal gyrus
    • inferior frontal gyrus
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3
Q

describe the locations of the motor cortex:

A
  • recall that the motor cortex = precentral gyrus + caudal frontal lobe
    • primary motor cortex: located in precentral gyrus (gyri ant to central sulcus)
    • premotor cortex: portions of caudal frontal lobe. specifically, the
      • posterior most portion of the _middle frontal gyr_i
      • posterior most portion of the inferior frontal gyri
  • supplemental motor cortex: caudal-most portion of the superior frontal gyrus
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4
Q

what gyri form the premotor cortex component of the motor cortex?

A

the posterior most portions of two frontal lobe gyri: middle, inferior

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5
Q

define & explain the homunculus

A

is a spatial segregation of the primary motor cortex (precentral gyrus) based on the portion of the body that they innervate

  • going from medial to lateral and also dorsal (superior) to ventral (inferior):
    • MEDIAL: lower body - distal to proximal
    • MIDDLE: 1. trunk / head / neck + upper body - distal to proximal to distal
    • LATERAL: face + thoat - superior to inferior
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6
Q

label & note important trends.

A
  • going from medial to lateral and also dorsal (superior) to ventral (inferior):
    • MEDIAL: lower body - distal to proximal
    • MIDDLE: 1. trunk / head / neck + upper body - distal to proximal to distal
    • LATERAL: face + thoat - superior to inferior
  • THE HIP: transition from medial to middle (also dorsal / superior) primary motor cortex
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7
Q

the portion of the primary motor cortex with nuerons that intervate the HIP serves as a transition from what two primary cortex regions?

A

transition from the medial premotor cortex (genitals + LE from D-P) to the middle / superior / dorsal premotor cortex (trunk + UE)

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8
Q

the parikaryons (neuron cell bodies) that make up the primary motor cortex send signals through axons that travel where?

A

give off the axons (white matter) that comprise the corona radiata.

will travel through the:

  • association fibers
  • corpus collosum
  • internal capsule

to get to

  • subcortical brain centers
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9
Q

review the components of the internal capsule and their bordering anatomy.

A
  • in a transverse cut
    • anterior crus:
      • caudate nucleus is medial
      • lentiform nucleus (globus pallidus + putamen) is lateral
    • genu
    • posteior crus
      • thalamus is medial
      • lentiform nucleus (globus pallidus + putamen) is lateral
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10
Q

genu

  • is what kind of neural tissue?
  • carries what signals? and
    • from where?
    • to where?
A
  • is axons (white matter) forming part of the IC
    • specifically, contains the corticobulbar tract axons, which:.
      • extend from primary motor cortex perikaryons (grey matter) located in the:
        • lateral (& most inferior) region. i.e:
          • head & neck:
            • ​eyes-nose-face-lips
            • teeth-gums-jaw
            • tongue-pharynx
      • carry motor info to: LMNS in the brainstem (cranial nerves)
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11
Q

posterior crus

  • is what kind of neural tissue?
  • carries what signals? and
    • from where?
    • to where?
A
  • is axons (white matter) forming part of the IC
    • specifically, corticospinal tract axons, which:
      • extend from primary motor cortex perikaryons (grey matter) located in the:
        • medial & middle (& most superior / dorsal) region
          • LE - distal to proximal
          • trunk-head-neck
          • UE -proximal to distal
      • rearrange info from: anterior-posterior: arm-trunk-leg
      • carry motor info to: spinal cord LMNS (ventral horn, gray matter)
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12
Q

explain how the posterior crus “rearranges” the signals it carries from the motor cortex

A
  • in medial & middle motor cortex perikaryocns:
    • LE: distal-prox I-S
    • trunk-head-neck
    • UE: prox-distal M-L/S-I
  • in posterior crus axons (corticobulbar tract):
    • anterior-posterior: arms-trunk-legs (a for arms)
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13
Q

compare contrast the genu and _posterior cru_s. note the

  • fibers they carry
  • their origins and destinations
A

both: extend from perikaryons in the primary motor cortex & synapse onto LMNs.

genu

  • corticobulbar tracts
  • lateral / inferior motor cortex
  • brainstem LMNS (cranial nerves)

posterior crus

  • corticospinal tract
  • medial / middle motor cortex
  • spinal cord LMNS (ventral horn)
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14
Q

the neurons that feed axons into the corticobulbar tract & corticospinal tract come from WHAT kind of neurons?

A

UPPER MOTOR NEURONS

(perikaryons in the primary motor cortex)

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15
Q

after the coritospinal tracts travel thru the posterior crus, where do they go next?

A

the brainstem: midbrain -> pons -> medulla

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16
Q

through what part of the midbrain does the corticospinal tract travel?

explain.

A
  • the crus cerebri: the most superficial / inferior / anterior component of the tegmentum (ventral midbrain) specifically,
    • through central 1/3 of the crus cerebri
    • with fibers rearranged medial-lateral: arms-trunk-leg
17
Q

through what part of the pons do the corticospinal tracts travel?

explain.

A
  • through the basis pontis
    • perpendicular to pontine nuclei
    • near ventral edge of pons
18
Q

what interactions pontine nuclei have with axons?

explain

A
  • corticospinal tracts - run thru ventral pontine nuclei at a perpendicular angle
  • middle cerebellar peduncle - formed from pontine nuclie that extend of lateral pons
19
Q

through what part of the medulla do the corticospinal tracts travel?

explain.

A
  • pyramids
    • after exiting the pons, they converge venterally & medially
    • then form / travel through the medullary pyramids
    • within the median fissure (between the pyramids), they dessucate
20
Q

review the ventral anatomy of the medulla oblongota

A
  • pyramids (corticospinal tracts): most ventral
  • median fissure: divides pyramids
  • anterolateral sulcus: border pyramids
  • inferior olives: lateral to pyramids
21
Q

discuss the dessucation of corticospinal tract

  • where does it occur?
  • what occurs after?
  • clinical relevance?
A
  • occurs in the median fissure (between pyramids)
  • 90% of corticospinal tracst with dessucate:
    • if they dessuccate -> lateral corticospinal tract
    • if they dessuccate -> vertical corticospinal tract
  • clinical:
    • stroke prior to dessucation = contralateral
    • stroke after dessucation = iupsilateral
22
Q

describe the architecture of the white matter in the spinal cord

A
  • divided into large regions called funiculi:
    • dorsal funiculus: medial to (im between) dorsal horns
    • ventral funiculus: medial to (in between) ventral horns
    • lateral funiculus: lateral to dorsal & ventral horns
23
Q

how do the corticospinal tracts move through the spinal cord?

what does it do here?

A
  • the corticospinal tracts runs through the gray matter of the spinal cord as two different tracts, where they synapse onto LMNs in the ventral horn:
    • lateral corticospinal tract:
      • ​DID dessucate
      • in the lateral funiculus
      • synapses onto lateral ventral horn: distal appendages
    • ventral corticospinal tract:
      • ​did NOT dessucate
      • in the ventral funiculus
      • synapses onto medial ventral horn: proximal appendages + TRUNK
24
Q

summarize the path of the corticospinal tract.

A
  1. perikaryons (UMNs) in medial + middle primary motor cortex give of axons that
  2. enter posterior crus (IC), arranged ant-post: arms-trunk-leg
  3. travel through brainstem:
    • midbrain: central crus cerebri, arranged med-lat: arms-trunk=leg
    • pons: pontine nuclei
    • medulla: pyramids, dessucate in median fissure
  4. enters white matter of spinal cord:
  5. synapse onto LMNS in the ventral horn
    1. ventral corticalspinal tract -> median ventral horn: trunk + proximal appendages
    2. latearl corticospinal tract -> lateral vental horn: distal appendges
25
Q

what does disruption the corticospinal tract lead to?

explain.

A

hemipeglia: paralysis on one side of the body.

  • a corticospinal lesion that is:
    • superior to dessucation (median fissure) -> contralateral hemiplegia
    • inferior to dessucation (median fissure) -> ipsilateral hemiplegia
26
Q

what does damage to UMNS result in?

explain.

A
  • in the absence of UMNs, LMN activation is primary regulated by sensory input.
    • remember that LMNS can receive input from: UMNs, interneurons, sensory.
      • ​negative feedback from the spindle apparatus / GTO will activate LMNs, will result in constant LMN contraction
27
Q

damage to UNNs of the

  • corticospinal tract
  • extrapyramidal tracts

leads to what presentation?

A
  • corticospinal tracts (legs, trunk, arms): hyperreflexia
  • extrampyramidal tracts (extensors m/c): rigid paralysis
28
Q

what is hoffman’s test?

what is a positive hoffman’s test, and what is it diagnostic of?

A
  • an UE assessment used to dx corticospinal tract UMN injury
  • tapping/flicking 3rd finger terminal phalanx: + test = thumb flexion/adduction
    • indicates hypereflexia -> UMN injury
29
Q

constrast the clinical presenattion / physical exam see in LMN damage vs LMN damage.

A
  • LMN damage: no input from ANYTHING.
    • flaccid paraylsis: hypotonia, hyporeflexia
    • clinical: no DTRs, no babinski
  • UMN damage: LMN intput only SENSORY (spindle, GTO)
    • rigid paralysis - hyperreflexia, hypertonia:
    • clinical: + Banbinski, + hoffman test
30
Q

primary lateral sclerosis

  • pathogenesis
  • presentation
  • histology
A
  • pathogenesis: corticospinal neuron (UMN) damage
  • presentation: hyperreflexia, hypertonia of appendanges + dysphagia
  • histology: lateral sclerosis: hardening of lateral funiculus d/t damage of the lateral corticospinal tract running through
31
Q

other than the corticospinal tract, what major component forms the medullary pyramids?

A

the corticobulbar tract

32
Q

review the path of the corticobular tract

A
  • perikaryons in lateral portion of primary motor cortex: head, neck
  • genu of internal capsule
  • medullary pyramids
  • synapse onto cranial nerve LMNs:
    • facial nerve (VII)
    • accessory nerve (XI)
33
Q

what is the extramedullary pyramidal system?

A

a system of tracts that, like ones in the pyramids, are made of upper motor neurons

but, the run outside the pyramids

34
Q

what are the tracts that form the of the extrapyramidal system?

briefly, where are their perikyarons (origins?)

A
  • tectospinal - superior colliculi (midbrain)
  • rubrospinal - red nuclei (midbrain)
  • medial longitudinal fasciulus - vesticular nuclei & superior colliculi
  • reticulospinal - reticular formation (midbrain)
  • vestibulospinal - vestibular nuclei
35
Q

which of the extra- pyramidal tracts dessucate?

where?

A
  • both dessucate in the ventral midbrain (tegmentum):
    • tectospinal: in dorsal tegmentum
    • rubrospinal: in ventral tegmentum
36
Q

tectospinal tract

  • originates from?
  • carries what info?
  • decussates where?
  • synapses where?
A

extrapyramidal tract

  • origin: colliculi (tectum) - i.e., “tecto”
  • carries: visual info (superior colliculi) and auditory info (inferior colliculi):
    • to drive reflexive movements of the head / neck
  • decussates where: dorsal tegmentum - comes from tectum, which is dorsal to tegmentum
  • synapses: onto LMNs in the ventral horn of spinal nerves to cervical segments
37
Q

rubrospinal tract

  • originates from?
  • carries what info?
  • decussates where?
  • synapses where?
A

(extrapyramidal tract)

  • originates from: red nucleus (tegmentum)
  • carriers: info that mediates postural tone
  • dessucates: ventral tegmentum
  • synapses onto: LMNS in medial ventral horn - trunk (postural muscles)

Neuro Exam I (15 decks)

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