Anatomical Basis of Movement Disorders Flashcards
what is the position of the caudate nucleus with respect ot the
- thalamus?
- lateral ventricles?
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

what is the caudate nucleus?
what are its important anatomic relations?
- 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

what is the amydala?
where is it located?
- the inferior tip of the caudate nucleus
- in the temporal lobe

what is the striatum?
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

what is the lentiform nucleus?
combination of putamen + globus pallidus
- what is the putamen?
- what borders it laterally & mediallly?
- 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)
- its medial surface is

what is the external capsule?
what are its key anatomic relations?
- the insula: a thin sheet of axons
- forms the lateral border of the putamen
what is the subthalamic nucleus?
what are its anatomic relations?
- 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
the substantia nigra
- is bordered by what structures dorsally?
- is histologically divided into what sections?
- 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
the basal ganglia
- recieves its main input frrom?
- provides its main output to?
- 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*
the input (afferent) signals to the basal ganglia
- come from where?
- by which fibers?
- carrying which specific signals?
- arrive at what region?
- come from: cerebral cortex (largely motor cortex)
- carried by: corticostriate fibers
- signals: glutamate (exctiroy)
- arrive at: the striatum (caudate nucleus + putamen)
the output (efferent) fibers from the basal ganglia
- originate where?
- travel via which fibers?
- carrying which specific signals?
- arrive at what region?
- 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

the ansa lenticarus and lenticular fasiculus
- travel how?
- merge to form what tract? where?
- 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

outline the direct pathway of the neural circuitry of the basal ganglia.
what is the ultimate consequence of the direct pathway?
- corticostriate fibers send glutamic (excitory) signals to striatum [afferent]
- stiatum internus, activated, sends GABAnergic (inhibitory) neurons to to globus pallidus internus
- the globus pallidus internus, inhibited, cannot sent GABA (inhibitor) neurons to the thalamus VA & VL [efferent]
- uninhibited VA & VL -> increased motor activity (disinhibition)

outline the indirect pathway of the neural circuitry of the basal ganglia.
what is the ultimate consequence of the direct pathway?
- corticostriate fibers send glutamic (excitory) signals to striatum [afferent]
- 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
- the globus pallidus internus, unhibited, sends GABA (inhibitor) neurons to the thalamus VA & VL [efferent]
- inhibited VA & VL -> decreased motor activity (inhibition)

what signals are the same in the direct & indirect basal ganglia neural circuitry?
which steps lead to the different results of each path?
- 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
draw out the basal ganglia - thalamus - motor cortrex circuit

what is dyskinesia?
abnormal timing of movement
excessive activity of each basal ganglia pathway would lead to which type of dyskinsesia?
- indirect pathway: hypokinesia (parkinsons)
- direct pathway: hyperkinesia (huntingtons chorea)
hemibalismus
- definition
- cause
- presentation
- 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
review the important anatomic relations of the infeior olivary nucleus:
- medially: medial lemniscus
- ventromedially: medullary pyramid
- separated by ventrolateral sulcus

how does the hypoglossal nerve travel through the medulla?
-
travels ventolaterally in between the:
- inferior olivary nucleus & medial lemniscus
- inferior olivary nucleus & medullary pyramids

list the afferents that feed into the inferior olivary nucleus
- spinoolivary tract (dorsal root ganglion)
- central tegmental (red nucleus)
- corticoolivary tract (cerebral cortex)
- cerebroolivary tract (cerebelloolivary)
the spinoolivary tract
- travels in what direction?
- originates where?
- synapse where?
- dessucates where?
- move where after reaching the inferior olive?
- 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
the central tegmental tract
- travels how?
- originates where?
- moves where after going ot the inferior olivary nculeus?
- are descending fibers
- originates: red nucleus.
-
parvocellular portion, specifically:
- rostral portion
- small cells
- densely packed
-
parvocellular portion, specifically:
- after reaching inferior olive: dessucate on the way to travel through inferior cerebellar peduncle [main olivary afferent]
which olivary afferent carries “feedback” fibers
cerebroolivary tract
the inferior olivary efferents
- carry what fibers?
- travel how?
- dessucate where?
- contribute to?
- 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
damage to the inferior olives would lead to what defects?
why?
- b/c it would disrupt efferents to the inferior cerebellar peduncle, which contributing to all cerebellar circuits:
- ataxia
- balance impairment
- motor learning
the corticospinal tracts divides into
- what two descending tracts?
- how do they travel?
- where & how do they synapse?
- 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
the red nucleus is divided into what regions?
by what anatomical landmarks?
that differ how?
- 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
-
parvocellular portion
describe how features of the tegmentum line with horizantally with the superior & inferior colliculi
- the colliculi line up with the red nuclei - superior cerebellar peduncle junction
- red nuclei (most rostral) - superior colliculi
- suprior cerebellar peduncle - superior colliculi
what are the afferents that go into the red nucleus?
- corticorubral tract
- cerebellorubral tract
the corticorubral tract
- originates where?
- travels how?
- goes where?
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
the cerebellorubral tract
- originates where?
- travels how?
- dessucate where?
- goes where?
red nucleus afferent
- originates: dentate nucleus (deep cerebellar nuclei)
- travels: through superior cerebellar peduncle
- dessucate: at the red nucleus surface
- goes to: red nucleus
rubrospinal tract
- originates where?
- travels how?
- dessucates where?
- goes where?
red nucleus efferent
- originates: red nucleus (tegmentum)
-
magnocellular portion
- caudal
- large cells
- loosely packed
-
magnocellular portion
- travels:
- through tegmentum - and dessucates here
- enters spinal cord - descends thru lateral funiculus
- go to: neurons that innervate the upper limb
the rubrospinal tract has what actions?
upper limb:
- flexor excitation
- extensor inhibition
the rubrospinal tract travels near what other major tract?
desends through the lateral lemniscus near the lateral corticospinal tract (dessucated)
rubroolivary tract
- originates where?
- travels how?
- goes where?
red nucleus efferent / inferior olive afferent - i.e., central tegmental tracgt
- originates in: red nucleus
-
parvocellular segment:
- rostral
- small cells
- tightly packed
-
parvocellular segment:
- travels through: central tegmental tract
- goes to: inferior olive
mollaret’s triangle
- is formed by what features?
- clinical relevance?
- 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
lesions to the red nucleus can lead to?
possibly, a rubral tremor (damage to tracts on either side of the red nucleus a more common cause)
what key tracts involve the magnocellular and parvocellular regions of the red nucleus?
- magnocellular: rubrospinal tract (red nucleus efferent) arises here
- parvocellular: ruboolivary / central tegmental tract (red nucleus efferent, inferior olivary afferent) arises here
lateral (medullary) reticulospinal tract
- originates where?
- travels how?
- goes where?
- mediates what?
- originates: reticular formation - gigantocellular nucleus
- travels: descends through the lateral funiculus
- mediates:
- weak flexion
- inhibition of extension of lower limb & trunk
(opposite of lateral vestibulospinal tract)
lateral vesibulospinal tract
- originates from?
- travels how?
- mediates what?
- originates: vestibular nucleus
- travels: in the ventral funiculus
- mediates:
- excitation of extensors
- inhibition of flexors - trunks & legs
(opposite of lateral reticulospinal tract)
what tracts make up the lateral motor system?
- lateral corticospinal
- lateral reticulospinal
- rubrospinal
medial vesitubulospinal tract
- originates where?
- travels how?
- mediates what?
- originates: medial vestibular nucleus
- travels: through the medial funiculus, only to the level of the neck
- mediates: movements of head & neck
medial reticulospinal tract
- origin
- pathway
- mediates
- origin: caudal and oral pontine nuclei (reticular formation)
- pathway: descents in ventral funiculus
- mediates:
- inhibition of flexors
- excitation of trunk + lower limbs
list each descending tract that innervate the legs.
indicate how each tract excites / inhibits muscle groups
- lateral corticospinal - excites everything
- lateral vestibulospinal - excites extensors + inhibits flexors
- pontine reticulospinal tract - excites extensors + inhibits flexors
which lower leg tracts excite the extensors while inhibiting the flexors?
- lateral vestibuospinal
- pontine reticulospinal
how does damage to the lateral corticospinal tract affect the legs?
why?
-
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
list each descending tract innervates the arms
indicate how each tract excites / inhibits individual muscle groups
- lateral corticospinal: excite everything
- rubrospinal: excites flexors + inhibit extensors
- medullary reticulospinal: excites flexors + inhibits extensors
which two arms tract excite the flexors + inhibit the extensors?
- rubrospinal
- medullary reticulospinal
how does damage to the corticospinal tract affect the arms?
why?
-
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
decorticate posture
- is caused by?
- presents as?
- cause: damage to the corticospinal tract
- presents as:
- lower limb extension
- upper limb flexion
decerebrate posture
- is caused by
- presents as
- cause: damage to BOTH the corticospinal tract & rubrospinal tract
- presentation:
- lower limb extension
- upper limb mixed:
- wrist flexion, but
- elbow extension