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Neuro Exam I > Anatomical Basis of Movement Disorders > Flashcards

Anatomical Basis of Movement Disorders Flashcards

1
Q

what is the position of the caudate nucleus with respect ot the

  • thalamus?
  • lateral ventricles?
A

caudate nucleus is a strucutre that moves in a horizantal plane, an caudally, runs in between the lateral vencticles (superior structure) and thalamus (inferior structure)

  • the tail of the caudate nucleus is bilaterally:
    • is along the superolateral surface of thalamus
    • along the deep (inferior) surface fo the lateral ventricles
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2
Q

what is the caudate nucleus?

what are its important anatomic relations?

A
  • an anteroinferior (rostral) expansion of the caudate nucleus
  • anatomic relations: to the more lateral putamen
    • inferior portion: is fused to the lateral putamen
    • superior portion: is separated from putamen by the anterior limb of the internal capsule
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3
Q

what is the amydala?

where is it located?

A
  • the inferior tip of the caudate nucleus
  • in the temporal lobe
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4
Q

what is the striatum?

A

a combination of the caudate nucleus + putamen

  • seen in the anteiror part of brain
  • superiorly are separated by the IC (anterior crus), inferiorly are directly fused
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5
Q

what is the lentiform nucleus?

A

combination of putamen + globus pallidus

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6
Q
  • what is the putamen?
  • what borders it laterally & mediallly?
A
  • the most lateral component of the basal ganglia:
  • borders:
    • its medial surface is
      • fused to head of the _caudate nucleu_s (superiorly)
      • fused to globus pallidus (inferiorly)
    • its lateral surface is: fused to the external capsule - i..e, the insula (thin sheet of axons)
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7
Q

what is the external capsule?

what are its key anatomic relations?

A
  • the insula: a thin sheet of axons
  • forms the lateral border of the putamen
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8
Q

what is the subthalamic nucleus?

what are its anatomic relations?

A
  • a small disc shaped body in the forebrain
  • anatomic relations:
    • inferior to the thalamus
    • thus, at the vertical level of the midbrain
      • medial to the IC (like the thalamus), and thus separated from the tegmentum by the external IC that covers it
      • lateral to the red nucleus
      • dorsal to the substantia nigra
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9
Q

the substantia nigra

  • is bordered by what structures dorsally?
  • is histologically divided into what sections?
A
  • bordered dorsally by the
    • red nucleus (medially)
    • subthalamic nucleus (laterally)
  • histologically divided into the:
    • substantia nigra pars compacta: neurons dense region
    • substasntia nigra pars reticula: neuron sparse region
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10
Q

the basal ganglia

  • recieves its main input frrom?
  • provides its main output to?
A
  • main input from: cerebral cortex
  • main output to: thalamus
    • which coordinates to the brain stem: the brainstem have no direct connections with the spinal cord*
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11
Q

the input (afferent) signals to the basal ganglia

  • come from where?
  • by which fibers?
  • carrying which specific signals?
  • arrive at what region?
A
  • come from: cerebral cortex (largely motor cortex)
  • carried by: corticostriate fibers
  • signals: glutamate (exctiroy)
  • arrive at: the striatum (caudate nucleus + putamen)
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12
Q

the output (efferent) fibers from the basal ganglia

  • originate where?
  • travel via which fibers?
  • carrying which specific signals?
  • arrive at what region?
A
  • originate in: globus pallidus interna
  • travel via the:
    • ansa lensicarus: travel inferior to posterior crus of IC
    • lenticarus fasciulus: travel perpendicular to posterior crus of IC
  • carrying: GABAnergic (inhibitory)
  • arrive at: the VA & VL (motor nuclei) of the thalamus
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13
Q

the ansa lenticarus and lenticular fasiculus

  • travel how?
  • merge to form what tract? where?
A
  • travel from globuls pallidus interna -> thalamus (VA & VL)
    • ansa lenticaris: courses inferior to posterior crus of IC
    • lenticular fasiculus: courses perpendicular to (through) posterior crus of IC
  • merge to form the pallidothalamic tract (thalamic fasciculus) once medial to the posterior crus - i.e., once in the thalamus
    • ansa lenticaris: courses inferior to posterior crus of IC
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14
Q

outline the direct pathway of the neural circuitry of the basal ganglia.

what is the ultimate consequence of the direct pathway?

A
  1. corticostriate fibers send glutamic (excitory) signals to striatum [afferent]
  2. stiatum internus, activated, sends GABAnergic (inhibitory) neurons to to globus pallidus internus
  3. the globus pallidus internus, inhibited, cannot sent GABA (inhibitor) neurons to the thalamus VA & VL [efferent]
  4. uninhibited VA & VL -> increased motor activity (disinhibition)
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15
Q

outline the indirect pathway of the neural circuitry of the basal ganglia.

what is the ultimate consequence of the direct pathway?

A
  1. corticostriate fibers send glutamic (excitory) signals to striatum [afferent]
  2. intermediate steps:
    • stiatum internus: uninhibited, sends GABA neurons to globus pallidus externus
    • globus pallidus: inhibited, cannot send GABA neurons to subthalamic nucleus
    • subthalamic nucleus: unihibited, sends sends glutamic globus pallidus internus
  3. the globus pallidus internus, unhibited, sends GABA (inhibitor) neurons to the thalamus VA & VL [efferent]
  4. inhibited VA & VL -> decreased motor activity (inhibition)
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16
Q

what signals are the same in the direct & indirect basal ganglia neural circuitry?

which steps lead to the different results of each path?

A
  • afferents to basal ganglia: always glu (excitatory)
  • efferents from basal ganglia: always GABA (inhibitory)
  • efferents from thalamus: always glu (excitatory)

direct pathway: striatum -> GABA -> globus internus -> no GABA -> VA & VL disnihibited -> increased motor cortex activity

indirect pathway: striatum -> GABA -> globus externus -> no GABA -> subthalamic nucleus -> glu -> globus internus -> GABA -> VA & VL inhibited -> decreased motor cortex activity

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17
Q

draw out the basal ganglia - thalamus - motor cortrex circuit

A
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18
Q

what is dyskinesia?

A

abnormal timing of movement

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19
Q

excessive activity of each basal ganglia pathway would lead to which type of dyskinsesia?

A
  • indirect pathway: hypokinesia (parkinsons)
  • direct pathway: hyperkinesia (huntingtons chorea)
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20
Q

hemibalismus

  • definition
  • cause
  • presentation
A
  • defintion: type of dyskinesia
  • cause: subthalamic nucleus disruption (indirect pathway)
    • leading to impaired disinhibition of thalamus & increased motor activity
  • presentation: violent, uncontolled motor activity on side of body contralateral to disruption
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21
Q

review the important anatomic relations of the infeior olivary nucleus:

A
  • medially: medial lemniscus
  • ventromedially: medullary pyramid
    • separated by ventrolateral sulcus
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22
Q

how does the hypoglossal nerve travel through the medulla?

A
  • travels ventolaterally in between the:
    • inferior olivary nucleus & medial lemniscus
    • inferior olivary nucleus & medullary pyramids
23
Q

list the afferents that feed into the inferior olivary nucleus

A
  • spinoolivary tract (dorsal root ganglion)
  • central tegmental (red nucleus)
  • corticoolivary tract (cerebral cortex)
  • cerebroolivary tract (cerebelloolivary)
24
Q

the spinoolivary tract

  • travels in what direction?
  • originates where?
  • synapse where?
  • dessucates where?
  • move where after reaching the inferior olive?
A
  • ascending tract (sensory)
  • path:
    • originates in dorsal root ganglion (1st order nueonrs)
    • 1st order neurons synapse in dorsal root (2nd order neurons)
    • 2nd order neurons
      • dessucate while moving to to ventral funiculus
      • ascend through the ventrl funiculus
      • synapse onto inferior olivary nucleus (3rd order neurons)
  • after reaching inferior olive: 3rd order neurons move to inferior cerebellar peduncle (main inferior olivary output0
25
Q

the central tegmental tract

  • travels how?
  • originates where?
  • moves where after going ot the inferior olivary nculeus?
A
  • are descending fibers
  • originates: red nucleus.
    • parvocellular portion, specifically:
      • rostral portion
      • small cells
      • densely packed
  • after reaching inferior olive: dessucate on the way to travel through inferior cerebellar peduncle [main olivary afferent]
26
Q

which olivary afferent carries “feedback” fibers

A

cerebroolivary tract

27
Q

the inferior olivary efferents

  • carry what fibers?
  • travel how?
  • dessucate where?
  • contribute to?
A
  • carried by: climbing fibers
  • travel through: the inferior cerebellar peduncle
  • dessucate in: the medulla
  • contribute to: all three functional circuits within the cerebellum
    • ​pontocerebellum
    • spinocerebellum
    • vestibulocerebellum
28
Q

damage to the inferior olives would lead to what defects?

why?

A
  • b/c it would disrupt efferents to the inferior cerebellar peduncle, which contributing to all cerebellar circuits:
    • ataxia
    • balance impairment
    • motor learning
29
Q

the corticospinal tracts divides into

  • what two descending tracts?
  • how do they travel?
  • where & how do they synapse?
A
  • forms the lateral & ventral corticospinal tracts
    • lateral corticospinal tracts: synapse onto LMNs in lateral ventral horn
    • ventral corticospinal tracts: syanpse onto LMNs in medial ventral horn
30
Q

the red nucleus is divided into what regions?

by what anatomical landmarks?

that differ how?

A
  • divided into rostral (superior) and caudal (inferior) portions by an imaginary line between the superior & inferior colliculus of the tectum:
    • parvocellular portion
      • rostral
      • small cells
      • densely packed
    • magnocellular portion
      • caudal
      • large cells
      • loosely packed
31
Q

describe how features of the tegmentum line with horizantally with the superior & inferior colliculi

A
  • the colliculi line up with the red nuclei - superior cerebellar peduncle junction
    • red nuclei (most rostral) - superior colliculi
    • suprior cerebellar peduncle - superior colliculi
32
Q

what are the afferents that go into the red nucleus?

A
  • corticorubral tract
  • cerebellorubral tract
33
Q

the corticorubral tract

  • originates where?
  • travels how?
  • goes where?
A

red nucleus afferent

  • originates: primary motor cortex (precentral gyrus) + premotor cortices
  • travels through: the posterior crus of the IC (like the corticorubral tract)
  • goes to: red nucleus
34
Q

the cerebellorubral tract

  • originates where?
  • travels how?
  • dessucate where?
  • goes where?
A

red nucleus afferent

  • originates: dentate nucleus (deep cerebellar nuclei)
  • travels: through superior cerebellar peduncle
  • dessucate: at the red nucleus surface
  • goes to: red nucleus
35
Q

rubrospinal tract

  • originates where?
  • travels how?
  • dessucates where?
  • goes where?
A

red nucleus efferent

  • originates: red nucleus (tegmentum)
    • magnocellular portion
      • caudal
      • large cells
      • loosely packed
  • travels:
    • through tegmentum - and dessucates here
    • enters spinal cord - descends thru lateral funiculus
  • go to: neurons that innervate the upper limb
36
Q

the rubrospinal tract has what actions?

A

upper limb:

  • flexor excitation
  • extensor inhibition
37
Q

the rubrospinal tract travels near what other major tract?

A

desends through the lateral lemniscus near the lateral corticospinal tract (dessucated)

38
Q

rubroolivary tract

  • originates where?
  • travels how?
  • goes where?
A

red nucleus efferent / inferior olive afferent - i.e., central tegmental tracgt

  • originates in: red nucleus
    • parvocellular segment:
      • rostral
      • small cells
      • tightly packed
  • travels through: central tegmental tract
  • goes to: inferior olive
39
Q

mollaret’s triangle

  • is formed by what features?
  • clinical relevance?
A
  • features
    • dentate nucleus (arbor vitae of cerebellum)
    • red nucleus (tegmentum)
    • inferior olivary bodies (medulla)
  • clinical: lesions in this region can lead to palatal myoclonus - contraction of the soft palate
40
Q

lesions to the red nucleus can lead to?

A

possibly, a rubral tremor (damage to tracts on either side of the red nucleus a more common cause)

41
Q

what key tracts involve the magnocellular and parvocellular regions of the red nucleus?

A
  • magnocellular: rubrospinal tract (red nucleus efferent) arises here
  • parvocellular: ruboolivary / central tegmental tract (red nucleus efferent, inferior olivary afferent) arises here
42
Q

lateral (medullary) reticulospinal tract

  • originates where?
  • travels how?
  • goes where?
  • mediates what?
A
  • originates: reticular formation - gigantocellular nucleus
  • travels: descends through the lateral funiculus
  • mediates:
    1. weak flexion
    2. inhibition of extension of lower limb & trunk

(opposite of lateral vestibulospinal tract)

43
Q

lateral vesibulospinal tract

  • originates from?
  • travels how?
  • mediates what?
A
  • originates: vestibular nucleus
  • travels: in the ventral funiculus
  • mediates:
    • excitation of extensors
    • inhibition of flexors - trunks & legs

(opposite of lateral reticulospinal tract)

44
Q

what tracts make up the lateral motor system?

A
  • lateral corticospinal
  • lateral reticulospinal
  • rubrospinal
45
Q

medial vesitubulospinal tract

  • originates where?
  • travels how?
  • mediates what?
A
  • originates: medial vestibular nucleus
  • travels: through the medial funiculus, only to the level of the neck
  • mediates: movements of head & neck
46
Q

medial reticulospinal tract

  • origin
  • pathway
  • mediates
A
  • origin: caudal and oral pontine nuclei (reticular formation)
  • pathway: descents in ventral funiculus
  • mediates:
    • inhibition of flexors
    • excitation of trunk + lower limbs
47
Q

list each descending tract that innervate the legs.

indicate how each tract excites / inhibits muscle groups

A
  • lateral corticospinal - excites everything
  • lateral vestibulospinal - excites extensors + inhibits flexors
  • pontine reticulospinal tract - excites extensors + inhibits flexors
48
Q

which lower leg tracts excite the extensors while inhibiting the flexors?

A
  • lateral vestibuospinal
  • pontine reticulospinal
49
Q

how does damage to the lateral corticospinal tract affect the legs?

why?

A
  • excess leg extension
    • w/out the lateral corticospinal, the legs are only innervated by the lateral vesitbulospinal & pontine reticulospinal, which both excite the extensors + inhibit the flexors
50
Q

list each descending tract innervates the arms

indicate how each tract excites / inhibits individual muscle groups

A
  • lateral corticospinal: excite everything
  • rubrospinal: excites flexors + inhibit extensors
  • medullary reticulospinal: excites flexors + inhibits extensors
51
Q

which two arms tract excite the flexors + inhibit the extensors?

A
  • rubrospinal
  • medullary reticulospinal
52
Q

how does damage to the corticospinal tract affect the arms?

why?

A
  • excess arm flexion
    • ​w/out the lateral corticospinal, the arms are only innervated by the rubrospinal & medullary reticulospinal which both excite the flexors + inhibit the extensors
53
Q

decorticate posture

  • is caused by?
  • presents as?
A
  • cause: damage to the corticospinal tract
  • presents as:
    • lower limb extension
    • upper limb flexion
54
Q

decerebrate posture

  • is caused by
  • presents as
A
  • cause: damage to BOTH the corticospinal tract & rubrospinal tract
  • presentation:
    • lower limb extension
    • upper limb mixed:
      • wrist flexion, but
      • elbow extension

Neuro Exam I (15 decks)

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