Motor Disorders Flashcards
Where is the cerebellum located
In posterior cranial fossa
Inferior to occipital lobe, separated by tentorium cerebelli
Posterior to Pons, separated by 4th ventricle
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
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
What is the overall function of cerebellum
Coordination
Precision of movements
Motor learning
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
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
What are the clinical features of cerebrocerebellum and spinocerebellum lesion
IPSILATERAL signs: Dysdiadochokinesia / dysmetria Ataxic gait Nystagmus Intention tremor Slurred speech Hypotonia
What is dysdiadochokinesia
Difficulty in carrying out rapid alternating movements
What is dysmetria
Lack of coordination characterised by overshooting of hand past intended position
What is ataxic gait
Wide and slow gait with tendency to fall on side of lesion
What is nystagmus
Involuntary eye movement, maximal on gaze towards lesion
What is intention tremor
Tremor when attempting voluntary and precise movements
Amplitude increases as you reach the target
How might lesion in vestibulocerebellum manifest
Loss of balance
Abnormal gait with a Wide stance
How might midline lesions present
Truncal ataxia on ipsilateral side
Hydrocephalus: compression of 4th ventricle, leading to signs of raised ICP
How might a cerebral hemisphere lesion present
Limb ataxia on Ipsilateral side
What is ataxia
Lack of coordination of voluntary movement, involving balance, coordination, speech
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
