Motor Disorders Flashcards by Minhee Kim

Where is the cerebellum located

In posterior cranial fossa
Inferior to occipital lobe, separated by tentorium cerebelli
Posterior to Pons, separated by 4th ventricle

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What are the structural divisions of cerebellum

Anatomical lobes:
Anterior lobe
Posterior lobe
Flocculonodular lobe 
Separated by primary fissure and posterolateral fissure

Anatomical zones:
Vermis
Intermediate zone
Lateral hemispheres

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What are the functional divisions of cerebellum

What are their functions

Vestibulocerebellum:
Balance and ocular reflex (fix gaze)
Input from vestibular system, output to vestibular nuclei

Spinocerebellum:
regulate movements by error correction (enable reliable delivery of signals over unreliable channels)

Cerebrocerebellum:
planning movements, motor learning, coordination of muscle activation
Input from cortex and pontine nuclei, output to Thalamus and red nucleus

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What is the overall function of cerebellum

Coordination
Precision of movements
Motor learning

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What is the blood supply of cerebellum

Superior cerebellar artery
Anterior inferior cerebellar artery
Posterior inferior cerebellar artery

SCA + AICA from basilar artery
PICA from vertebral artery

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What are possible causes of cerebellar dysfunction

Stroke/TIA
Tumours (can cause hydrocephalus)
Thiamine deficiency 
Toxins: alcohol, barbiturates,phenytoin 
Multiple sclerosis
Infection: meningo-encephalitis, HIV

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What are the clinical features of cerebrocerebellum and spinocerebellum lesion

IPSILATERAL signs: 
Dysdiadochokinesia / dysmetria 
Ataxic gait  
Nystagmus 
Intention tremor 
Slurred speech 
Hypotonia

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What is dysdiadochokinesia

Difficulty in carrying out rapid alternating movements

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What is dysmetria

Lack of coordination characterised by overshooting of hand past intended position

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What is ataxic gait

Wide and slow gait with tendency to fall on side of lesion

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What is nystagmus

Involuntary eye movement, maximal on gaze towards lesion

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What is intention tremor

Tremor when attempting voluntary and precise movements

Amplitude increases as you reach the target

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How might lesion in vestibulocerebellum manifest

Loss of balance

Abnormal gait with a Wide stance

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How might midline lesions present

Truncal ataxia on ipsilateral side

Hydrocephalus: compression of 4th ventricle, leading to signs of raised ICP

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How might a cerebral hemisphere lesion present

Limb ataxia on Ipsilateral side

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What is ataxia

Lack of coordination of voluntary movement, involving balance, coordination, speech

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What is the basal ganglia

Group of subcortical nucleiin forebrain:
Lentiform nucleus (Globus Pallidus interna and externa, Putamen)
Subthalamic nucleus
Caudate nucleus
Substantia nigra pars compacta

What is the role of basal ganglia

Acts as a feedback circuit, to modulate and refine cortical activation
Main function as editing motor plan: reduce excitatory input to cortex to inhibit excessive movements

What does editing motor plan involve

Stimulation of direct pathway to facilitate appropriate movements
Stimulation of indirect pathway to inhibit inappropriate/excessive movements

How does basal ganglia facilitate appropriate movement

Putamen receives cortical input for appropriate movement
Activation of direct pathway
Putamen inhibits Globus Pallidus Interna
Loss of inhibition of thalamus by GPi
Increased thalamic activity
Increased motor cortical activity
Increased descending motor signal / movement

How does basal ganglia inhibit inappropriate movement

Putamen receives input from cortex (for inappropriate movement) 
Putamen stimulates indirect pathway 
Putamen inhibits GPe 
Loss of inhibition of STN by GPe
Stimulation of GPi
Thalamic inhibition by GPi
Decreased motor cortex stimulation 
Decreased descending motor signal / movement

What is the role of substantia nigra pars compacta

Regulate Putamen activity by release of dopamine
Dopamine excites direct pathway + inhibits indirect pathway
Overall increased thalamic activity
Increased motor cortical activity and movement

What is Parkinsons Disease

Progressive neurodegenerative disorder involving degeneration of dopaminergic neurones of Substantia nigra pars compacta

Clinical triad of PD

Bradykinesia
Tremor
Rigidity

Clinical features of PD

``` Bradykinesia Tremor Rigidity Postural instability Shuffling gait Reduced facial expression Hypophonia Micrographia Lewy body dementia ```

What is bradykinesia

Slowness of movement

What type of tremor do you get with PD

``` Resting tremor: Lips and tongue Pronation-supination of forearm Flexion-extension of fingers Pill-rolling - index/middle fingers against thumb pad ```

What is rigidity | What are features of rigidity

Stiffness | Cog wheeling - tremor superimposed on rigidity

What is Huntington’s disease

Autosomal dominant progressive neurodegenerative disorder involving degeneration of GABA neurones of indirect pathway

What is the age of onset for HD

30-50

What are clinical features of HD

Chorea Athetosis Abnormal eye movements Personality changes Dementia

What is chorea

Increased involuntary movements, Type of hyperkinetic movement disorder Presents with dance-like movements: not repetitive but flow from one muscle to next

What is athetosis

Slow, involuntary snake like movements of hands, feet

What would occur to the basal ganglia feedback mechanism if STN was damaged

Reduced stimulation/activity of GPi Loss of inhibition of thalamus by GPi Increased thalamic thus cortical activity Increased descending motor signals + movement Hyperkinesia (loss of inhibition)

What is a possible cause of STN damage

Small vessel stroke

How may STN lesion present

Ballismus: Repetitive, large amplitude involuntary movements of proximal limbs. Movements appear violent, continuous and random Hemiballismus in stroke Type of chorea

How do you perform a Romberg’s test

Ask patient to stand with eyes closed | Look for INCREASED loss of balance

What sensory inputs does Balance require

Vision Vestibular function Proprioception Balance requires at least 2/3 of inputs

What is a Romberg’s test testing

Proprioception and vestibular function Loss of vision on standing means balance is dependent on both proprioception and vestibular function Loss of balance with no vision means either of the inputs are not working

What might Romberg’s test be used to investigate

Ataxia

What does a +ve Rombergs test mean

Ataxia is sensory in nature

What does a -ve Romberg’s test mean

Ataxia is cerebellar in nature: | Patient is ataxic but no increase in ataxia with eyes closed