Basal Ganglia Flashcards
collection of gray matter nuclei located deep within the cerebral white matter
basal ganglia
Basal ganglia components
caudate nucleus
putamen
globus pallidus (GP)
Subthalamic nucleus (STN) –> nucleus of Luys
Substantia nigra (SN)
Stratum Neostriatum: Caudate, Putamen
Lentiform nucleus: Putamen, Globus Pallidus
Corpus striatum: Caudate, Putamen, Globus Pallidus
Ventral striatum
Similar embryonic development and input/ output connections
limbic system
nucleus accumbens
do not participate in any direct way in modulation of movement
amygdaloid nuclear complex (limbic system) and claustrum
nucleus of Luys
Subthalamic nucleus
elongated arched gray cellular mass related throughout its extent to the lateral ventricle
caudate nucleus
shape of caudate
c shaped
lateral surface of caudate nucleus is related to
internal capsule which separates it from lentiform nucleus
parts of caudate nucleus
head - enlarged, protrudes into anterior horn of lateral ventricle
Body - dorsolateral to the thalamus near the lat wall of the lat ventricle
Tail - follows the curvature of inf horn of lat ventricle and enters the temporal lobe; terminates in the region of the amygdaloid complex
wedge shaped with apex directed medially
lentiform nucleus
lentiform broad convex base is directed
laterally
separates lentiform from claustrum
external capsule
most lat part of the corpus striatum and is darker and larger
putamen
location of lentiform
b/w int and ext capsule
loc of putamen
b/w ext capsule and lat medullary lamina of globus pallidus
rostral part of putamen is continuous
ventromedially with head of caudate
most medial part of lentiform nucleus
globus pallidus (lighter, inner portion)
has high concentration of myelinated fibers
globus pallidus
origin of globus pallidus
diencephalic orgin
separates 2 segments of globus pallidus
medial medullary lamina
medial border of globus pallidus
fibers of post limb of internal capsule
divides corpus striatum into caudate and lentiform
internal capsule
striated appearance produced by grands of gray matter passing through int capsule and connecting the caudate nucleus to putamen
striatum
receives inputs to basal ganglia
striatume
joins caudate and putamen in some places
cellular bridges
putamen is fused with head of caudate forming
ventral striatum
nucleus found in ventral striatum
nucleus accumbens
neurotransmitter in substantia nigra
dopamine
2 portions of substantia nigra
substantia nigra pars reticulata (ventral)
substantia nigra pars compacta (dorsal)
diff between pars reticulata and compacta
pars reticulata is ventral. Cells are similar to globus pallidus interna (GPI) and is seprated by int capsule
pars compacta is dorsal and has darkly pigmented dopaminergic neurons
spindle or cigar shaped
subthalamic nucleus
connections of the basal ganglia
main input/ receptive site: striatum (caudate, putamen)
main output: GPi and substantia nigra pars reticulata
neurons of basal ganglia for input and output
glutamate - excitatory
GABA - inhibitory
other sources of input to basal ganglia
intralaminar nuclei of thalamus (centromedian and parafascicular nuclei) -> (+) glutamate
raphe nuclei - seretonin
Frontal lobe outputs of the four parallel channels through basal ganglia
Motor channel - motor
oculomotor - eye movements
prefrontal channel - cognitive process
limbic channel - emotions
Output pathways from GPi run to thalamus through two bundles:
Ansa Lenticularis
Fasciculus lenticularis
Difference b/w Ansa lenticularis and Fasciculus lenticularis
Ansa lenticularis (H2 field of Forel)
- lenticular loop
- sweeps around internal capsule
- looping course ventrally under int capsule before passing dorsally to thalamus
Fasciculus lenticularis
- traverse int capsule in small fascicles and continues medially and caudally to join ansa in the prerubral field
- penetrate straight through int capsule
Ansa Lenticularis and Lenticular fasciculus both join to form the
thalamic fasciculus
thalamic fasciculus contain what projections
pallidothalamic, mesothalamic, rubrothalamic, dentatothalamic
centromedian group of Ansa Lenticularis and Lenticular fasciculus project back to the putamen and via what to nucleus to caudate
parafasciscular nucleus
origin of projections found in thalamic fasciculus
Mesothalamic - substantia nigra
rubrothalamic - red nucleus
dentatothalamic - cerebellum
Fields of Forel
H1 - thalamic fasciculus
H2 - lenticular fasciculus dorsal to subthalamic nucleus
H(prerubral field) = where ansa lenticularis and lenticular fascisculus join together
where ansa lenticularis and lenticular fascisculus join together
H (prerubral field)
Subthalamic fasciculus carries fibers of indirect pathway from ____ to ___ and from ____ to ____
GPe to STN
STN to GPi
function of basal ganglia
act as brake or switch
- brake (inhibitory action)
- switch (select which of the avail motor programs will be active at a given time)
motor programming
priming of motor systems for rapid execution
pyramidal vs extrapyramidal
pyramidal (lesions in corticospinal/ UMN pathways)
extrapyramidal (lesions in basal ganglia)
unilateral movement disorders is due to
contralateral Basal ganglia because motor pathways cross due to pyramidal tract
movement disorders from slowest to fastest
Slow:
Bradykinesia hypokinesia
rigidity
dystonia
medium:
Athetosis
Chorea
Fast:
Ballismus
tics
Myoclonus
Bradykinesia vs hypokinesia vs akinesia
Bradykinesia - slowed movement
hypokinesia - decreased amount of movements
akinesia- absence of movenent
Marked psychomotor retardation in patients with schizophrenia or severe depression
Catatonia (not a basal ganglia lesion)`
increased resistance to passive movement of the limb
rigidity
lesion in spasticity
upper motor neuron
clasp knife phenomenon in hemiplegic, quadriplegic, monoplegic, or paraplegic distribution
Spasticity
How does the examiner elicits the
clasp-knife phenomenon,
catch and yield sensation
by a quick jerk of resting extremity
lead-pipe phenomenon, often with cogwheeling and tremor at rest; usually in all four extremities but may have a hemi distribution
rigidity
how does the examiner elicits the lead-pipe phenomenon of rigidity
by making a relatively slow movement of pt’s resting extremity
lead pipe rigidity vs cogwheel rigidity
lead pipe rigidity - more continuous throughout attempts to bend the limb
cogwheel - ratchet like interruptions in tone
Rigidity:
frontal lobe dysfunction actively resist movement of their limbs; more active; inconsistent or almost voluntary quality
paratonia/ gegenhalten
phenomenon: spastcity vs rigidity
Spasticity: Clasp-life
Rigidity: lead pipe
abnormal, distorted positions of limbs, trunk, or face that are sustained or slower than athetosis
pt stay at a certain posture
Dystonia
Focal vs Generalized dystonia
focal - torticollis, blepharospasms, spasmodic dysphonia, writer’s cramp
Generalized - XDP
slow, writhing movements usually of the fingers and extremities that sometimes merge with faster choreic movements
athetosis
“dance” characterized by nearly continuous involuntary movements that have a fluid or jerky, constant varying quality
chorea
“throw”
movement of the proximal limb muscles with large-amplitude or more rotatory flinging quality
ballismus
unilat flinging movements of extremities contra to lesion in BG
hemiballismus
leading to decreased pallidal inhibition of the thalamus
subthalamic nucleus lesion
sudden brief action by urge and is followed by a sense of relief
tics
persistent motor and vocal tics
tourette’s syndrome
fastest of all movement disorders
myoclonus
intermittent brief flexion movements of wrists bilat as pt attempts to hold stop the traffic position
asterixis (flapping tumor)
types of tremors
resting tremor (3-5 Hz)
- prominent when limbs are relaxed
- disappears when patient moves their limbs
- parkinsons disease
- aka pill rolling tremor
postural tremor
- when limbs are held in a position
- disappears at rest
Essential tremor (5-8 Hz)
- benign
- increases with stress
- alcohol decreases it temporarily
Physiological (8-13)
- normal
Intention (2-4)
- when pt move limb toward a target
Rubral (2-4)
- low at rest but becomes more violent when limbs are abducted slightly or hold a movement
- lesion in superior cerebellar peduncle
