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6a > Basal ganglia and movement disorders > Flashcards

Basal ganglia and movement disorders Flashcards

1
Q

Main functions of basal ganglia

A

modulation of voluntary motor activity
balance of inhibitory/excitatory pathways, gives input to thalamus and from there to cortex
activity encodes for:
- decision to move
- direction/amplitude of movement
- motor expression of emotions
- making movemetns and behaviour more efficient (proceduralization)

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2
Q

circuits in basal ganglia

A

motor: controls body/eye movements
associative: higher level cognitive function
limbic: emotional/motivational processing

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3
Q

Thalamus main role

A

under chronic inhibition when we are not moving

want to move –> balance of inhibitory and excitatory circuits –> measured input to motor cortex, and measured movement

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4
Q

Release-inhibition model (Direct)

A

release tonic inhibition of thalamus –> increased excitation of motor cortex –> increased motor output

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5
Q

Release-inhibition model (Indirect)

A

inhibits output from thalamus –> decreased excitation of motor cortex –> reduced motor output

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6
Q

Function of direct/indirect pathways

A

happening simultaneously –> fine balance
Target-oriented, efficient movements are facilitated (direct)
superfluos competing movements are inhibited (indirect)
streamline movement –> target-oriented, efficient

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7
Q

Lesions to the Basal Ganglia

A

Parkinson’s: inhibition of motor output

Ballism/Huntington’s: excessive motor output

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8
Q

Ballism

A

hyperkinetic
large amplitude, non-rhythmic, sudden uncontrolled flinging movements of extremities
usually only occurs on one side (hemiballism)
underlying cause –> lesion/stroke of contralateral subthalamic nucleus
LOSS of indirect pathway –> no more suppression of superfluos movement

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9
Q

Huntington’s disease

A

hyperkinetic
deficits in cognition, behaviour and a characteristic hyperkinetic disorder
Brief, irregular unpredictable movements that move randomly from one part of body to another (Chorea)
Degeneration of striatum (caudate/putamen)
- damage to striatum: effects on both direct and indirect pathways
- direct pathway: loss of target-oriented, efficient movemetns
- indirect: subthalamus remains inhibited; no control over superfluous competing movements
CAG repeats on chromosome 4 –> abnormal amount of huntingtin

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10
Q

Parkinson’s disease

A

degeneration of dopaminergic neurons of substantia nigra
Direct: less inhibition of tonic inhibition of thalamus –> target oriented and efficient movements not facilitated
Indirect: GPe is inhibited, less inhibitory input to STN, more excitatoyr input to GPi, more inhibition of thalamus
Hypo/akinesia
Loss of facial expression - hypomimia

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11
Q

PD treatment options

A

L-Dopa
deep brain stimulation of subthalamic nucleus, restores tonic firing pattern from STN to GPi –> less inhibition of the thalamus

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12
Q

Motor circuit of basal ganglia fxn

A

motor performance and regulation of eye movemetns
both direct/indirect
measured and coordinated motor performance
regulation of gaze and orientation of eyes, amplitude of saccades

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13
Q

Associative circuit of basal ganglia fxn

A

participates in planning complex motor activity
when a novel task has been practiced/well-learned, activity in associative circuit decreases and motor circuit becomes more active

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14
Q

Limbic circuit of basal ganglia fxn

A

motor expression of emotion
postures, gestures and facial expresion related to emotion
rich in dopaminergic neurons - mask face in PD

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15
Q

Classification of movement disorders

A

Pyramidal syndromes
Basal ganglia disorders
Cerebellar disorders

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16
Q

Basal ganglia disorders

A

Parnkinsonian syndromes
Dyskinesias
Stereotyped movements

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17
Q

Cerebellar disorder characteristic

A

ataxia

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18
Q

Parkinsonian syndrome characteristics

A

akinesia

rigidity

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19
Q

Dyskinesias characteristics

A 
chorea
dystonia
myoclonus
tics
tremor
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20
Q

Pyramidal symptoms

A

spasticity - velocity/direction dependent
weakness
paralysis
UMN (CST, corticobulbar)

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21
Q

extrapyramidal symptoms

A

rigidity
no overt weakness
insufficient/excessive/abnormal movements
“basal ganglia”

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22
Q

Basal ganglia lesion symptoms

A 
no weakness
no paralysis
slowed movement/involuntary movement
rigidity, not velocity dependent
constant resistance throughout range of movement
normal muscle tone
normal reflexes
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23
Q

Basal ganglia structures

A

caudate-putamen (neostriatum)
Globus pallidus (external/internal)
substantia nigra (source of dopamine), pars reticulata, pars compacta
subthalamic nucleus

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24
Q

General approach to movement disorders

A

Identify pattern of abnormal movement
find out underlying cause, if any
treat underlying cause/give symptomatic therapy

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25
Q

Tremor

A

regular
repetitive
sinusoidal cycles
alternating contractions of antagonistic pairs of muscles

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26
Q

Clinical assessment of tremor

A

Topography - place
Activation condition (rest, posture, non-goal/goal-directed movements)
Frequency of tremor (Low 7)

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27
Q

Common causes of tremor

A

Enhanced physiological tremor - drugs, anxiety, hyperthyroidism
Essential tremor
Parkinson’s disease
Cerebellar disease

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28
Q

Anxiety and tremor

A

movement stretches agonist and causes an afferent volley eliciting reflexes in antagonistic extensors
when reflex gains and conduction times are appropriate, an oscillation will result
Adrenaline/thyroid hormoens sensitize muscle spindles –> stronger afferent volley, increases tremor amplitude

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29
Q

Activation condition of tremor

A

Intention - cerebellar
Postural - essential
Rest - Parkinson’s disease

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30
Q

Essential tremor core criteria

A

Bilateral action tremor of hands and forearms (but no rest tremor)
absence of other neurological signs except cogwheeling
ma have isolated head tremor with no abnormal posture
shouldn’t have slow movements
most common movement disorder

31
Q

Essential tremor red flags

A 
unilateral/focal/leg tremor
gait disturbance
rigidity
bradykinesia
rest tremor
sudden/rapid onset
current drug treatment that might cause/worsen tremor
isolated head tremor with abnormal posture (head tilt/turning)
32
Q

Essential tremor treatment first line

A

Propranolol
CI: cardiac, pulmonary, DM
Primidone: preferentially for patients >60

33
Q

2nd line treatments for essential tremor

A

Gabapentin - conflicting results
Clonazepam - for predominant kinetic tremor
Topiramate - may work with as little as 50 mg/day

34
Q

3rd line treatments for essential tremor

A

Clozapine - usually better for PD

Olanzapine - single open label trial

35
Q

Last resort treatment for essential tremor

A

surgery

VIM thalamus stimulation

36
Q

Essential tremor vs Parkinson’s disease

A

Tremor:

  • Archimides’ spiral poor
  • cogwheeling
  • head/voice may be affected
  • relatively symmetric
  • writing large, tremulous
  • typically better while walking
  • often improves with alcohol
37
Q

Parkinson’s disease features

A 
TRAP
Tremor: resting
Rigidity
Akinesia/bradykinesia
Postural instability: relatively late presentation
Masked face
Micrographia
38
Q

Pathology of Parkinson’s disease

A

loss of dopaminergic cells in substantia nigra (PET scan)

causes: genetics? toxins?

39
Q

Genetic factors of Parkinson’s disease

A 
increased risk in primary relatives
twin studies - low concordance
Recently many genes implicated in rare cases of PD that are strongly familial
 - alpha-synuclein
- Parkin
- LRRK2
40
Q

Environmental factors of Parkinson’s disease

A 
increased risk in people growing up in rural areas
Toxins:
- MPTP
- Hydrocarbons
- Manganese
- methanol
-cyanide
- carbon disulfide
- lacquer thinner
- thiocarbamate
- N-hexane
- organochloride
41
Q

Parkinson’s disease protective agents

A

Coffee

smoking

42
Q

Early signs of PD

A 
Anosmia
Depression, anxiety
REM sleep disorder
masked faces
micrographia
stiffness, neck pain
constipation - risk increased if
43
Q

Early motor symptoms of PD

A

symptoms most predictive of PD (rather than atypical Parkinsonism)
Asymmetric onset of tremor/rigidity/bradykinesia
L-dopa responsiveness
note: 30% of PD patients do not have tremor

44
Q

Parkinson’s plus/Parkinsonism

A 
doesn't respond significantly to medications
symptomatic treatment only
Multiple infarcts --> vascular Parkinsonism
Progressive supranuclear palsy (PSP)
Multisystem atrophy:
- striatonigral degeneration
- shy-Drager
- Olivopontocerebellar atrophy
45
Q

Impulse control disorders in Parkinson’s

A

6-18% of PD subjects on dopamine agonists develop ICD
Pathological gambling
hypersexuality
compulsive shopping, eating

46
Q

Levodopa

A

Levodopa therapy
prolongs survival
BUT problems of long-term complications, e.g. dyskinesia
disease progression and levodopa effectiveness
- symptoms and side effects occur as levodopa therapeutic window diminishes
GI problems: use carbidopa - prevents levodopa conversion to dopamine in gut to reduce GI symptoms; also doesn’t cross BBB, so only acts on gut

47
Q

Surgical treatment of PD

A

Stereotaxic surgery: DBS, pallidotomy

Repalcement: fetal cell transplant, genetic engineered cell lines, human retinal cells

48
Q

Supportive treatment of PD

A

physio
rehab
occupational modification
support groups

49
Q

Chorea

A 
irregular
non-repetitive
non-purposeful
unpredictable
smooth, flowing, fast/slow
not suppressible
50
Q

Causes of chorea

A 
Huntington's disease
Drugs - levodopa, neuroleptic drugs
Infections
Thyrotoxicosis
Pregnancy
51
Q

Huntington’s disease treatment

A

Chorea: anti-dopaminergic drugs - dopamine depleting agents preferred over dopamine receptor blockers
Dementia: no treatment
Counselling

52
Q

Tic

A 
irregular
non-purposeful
predictable in pattern but not in time
stereotypic
suppressible
53
Q

Tourette’s syndrome

A

multiple tics
childhood onset
persistent for > 1 year
Coprolalia (involuntary swearing)

54
Q

Tourette’s treatment

A

Anti-dopaminergic drugs

Dopamine depleting agents preferred > dopamine receptor blockers

55
Q

Ballism

A 
irregular
non-repetitive
non-purposeful
unpredictable
violent, proximal
not suppressible
Normally associated with damage to subthalamic nucleus
56
Q

Causes/treatment for ballism

A 
cerebrovascular (hemiballismus)
infections
tumors
sedation
develops into chorea - treatment with dopamine blocking agents
57
Q

Dystonia

A 
involuntary msucle contractions
co-contraction of antagonists
abnormal postures
may be worse with specific actions
disappears during sleep
Classified by etiology, age of onset, anatomical
58
Q

Dystonia - rule out

A 
drug
DOPA-responsive
WIlson's
Huntington's
Structural lesions of the basal ganglia
59
Q

Generalized dystonia

A 
normal birth history, milestones
autosomal dominant
childhood onset
starts in lower limbs, spread upwards
also know as idiopathic torsion dystonia
60
Q

Focal dystonia

A 
eyelids
face
jaws
neck
voice
upper limbs
task-specific dystonia
lower limb dystonia
truncal dystonia
61
Q

Task-specific dystonia

A

writer’s, musician’s, painter’s, golfer’s, dartsman’s, trapshooter’s cramps

62
Q

Dystonia treatment of primary cause

A

treat primary cause if any
discontinue drugs if possible
DOPA for DOPA-responsive dystonia
Reduce copper if WIlson’s disease

63
Q

Dystonia symptomatic treatment

A

Medications - usually don’t work very well
- anticholinergic, dopaminergic, anti-dopaminergic
- GAGA-ergic
- anticonvulsants
-baclofen
Botox: mainly focal
- blepharospasm, oromandibular, cervical, others

64
Q

Surgical treatment of dystonia

A

myectomy
tenotomy
thalamotomy
?? DBS

65
Q

Myoclonus

A

shock-like movements caused by sudden muscle contraction (positive myoclonus) or by muscle relaxation (negative myoclonus)
Asterexis is a type of negative myoclonus

66
Q

Drug-induced movement disorders

A 
Acute dystonic reactions
Parkinsonism
Akathisia
Neuroleptic malignant syndrome
Tardive dyskinesias
67
Q

Acute dystonic reactions

A

within 96 hours of therapy
oculogyric crisis
seen in 2.3-21%, usually young males
mechanism unknown - related to greater activation of unblocked D1 receptors??
Effectively controlled by anticholinergics

68
Q

Drug-induced Parkinsonism

A 
Dopamine receptor blocking agents
neuroleptics
antiemetics (metoclopramide)
Ca channel blockers (flunarizine)
antihypertensives
69
Q

Drug-induced akathisia

A

inability to remain seated
often seen with neuroleptic use
sensation of inner restlessness, dysphoria, anxiety
compulsion to move legs - walking on spot
may be associated with Parkinson’s disease
usually 1 hour after administration, but may be several weeks later

70
Q

Neuroleptic malignant syndrome

A

uncommon, but canbe fatal
agitation, lethargy, confusion, delirium, stupor, coma
hyperthermia, tachypnea, BP changes
rigidity, akinesia, tremor, dystonia, chorea
seizures
elevated CK
myoglobinuria
may occur with first exposure to neuroleptics, or when re-instituting therapy after a long period of time
acute withdrawal of dopaminergic drugs
general supportive measures - management of hyperthermia, adequate hydration, dopamine agonists

71
Q

Tardive syndrome

A

abnormal involuntary movement
exposure to causative agent within 6 mo of onset
persistence for at least 1 mo after stopping
minimum 3 mo exposure
Tardive dyskinesia: can get almost any movemetn disorder as a tardive phenomenom:
- dyskinesia
- dystonia
- tic
- akathisia
- tremor
- myoclonus

72
Q

Treatment summary of movement disorders

A

tremor - PD: levodopa, dopamine agonists
Essential tremor - beta blockers, anticonvulsants
Chorea, tics, ballism: tetrabenazine (dopamine depleting agent)
dystonia: anticholinergics, botox

73
Q

Braak hypothesis

A 
Parkinson's disease
selective neuronal death in brainstem
caudo-rostrally progressive pattern
1, 2) autonomic/olfactory disturbances
3,4) sleep and motor
5, 6)emotional and cognitive disturbances

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