L15 - Disorders of Motor control Flashcards
What is Ataxia?
- Group of disorders that affect:
a) co-ordination
b) balance
c) speech - Impaired calibration of movement.
Briefly state the different categories of ataxia?
- Acquired ataxia
- symptoms develop as result of trauma, stroke, MS - Hereditary ataxia
- symptoms develop slowly over many year, caused by faulty genes a person inherits from parents e.g. Friedreich’s ataxia - Idiopathic late-onset cerebellar ataxia
- brain progressively damaged for unclear reasons
What is sensory ataxia?
- Loss of coordination
- caused by loss of sensory input into control of movement
NOT BY cerebellar dysfunction.
How may sensory ataxia be distinguished from cerebellar ataxia?
- Patient has near-normal coordination when movement is visually observed by patient
- but marked worsening of coordination when eyes are shut
- indicating positive Rhomberg’s sign.
Hypokinesia
Motor activity is reduced or slowed, except for the resting tremor.
e.g. Parkinson’s
Akinesia
No movement
Diskinesia
Bad movement
Apraxia
Brains inability to select correct movement.
What causes ataxia?
Lesions of the cerebellum or its connections.
What may cause hypokinesia / hyperkinesia?
Lesions of the Basal ganglia.
What may cause apraxia?
Lesions of the motor association cortices.
Describe central ataxia?
impaired ……..? processing
Impaired cerebellar processing.
State some signs of sensory ataxia?
- Discrepancy in finger-nose performance when performed with eyes closed then open.
- Psuedoathetosis
- Romberg sign
What is Psuedoathetosis?
Inability to maintain posture with eyes closed, giving rise to a wandering movement of the fingers or hands)
Recap: Romberg’s sign
Inability to remain standing when eyes are closed.
What may cause sensory ataxia?
Damage to nerves in spinal cord or nerves leading to extremities such as the feet and legs.
What does cerebellar ataxia lead to?
- Lack of muscle movement coordination
- caused by a dysfunction in cerebellum.
- Cerebellum controls timing and force of muscle movement.
State some common symptoms of ataxia?
- Incoordination of hands, arms and legs
- Slurring of speech
- Wide-based gait
- Difficulty with writing and eating
- Slow eye movements.
Dysmetria
Lack of coordination of movement.
Undershoot or Overshoot
Dysdiadochokinesia
Medical term for an impaired ability to perform rapid, alternating movements.
Complete inability - adiadochokinesia
Nystagmus
Vision condition in which the eyes make repetitive, uncontrolled movements.
- result in reduced vision
- depth perception
- can affect balance and coordination
Dysarthria
Difficult or unclear articulation of speech that is otherwise linguistically normal.
What are some signs of central ataxia?
- Dysmetria on finger nose test.
- Impaired ability on rapid supination and pronation of the hands.
- Gait Ataxia (broad-based)
- Impaired heel-toe walking (tandem gait)
- Lack of coordination of eye movement
- Slurred speech
Describe some important causes of brain disease?
- Vascular (posterior circulation)
- Compression from tumour
- Trauma
- demyelinating inflammation (MS)
- infection (viral cerebelitis, abscess e.g. from inner ear)
State some metabolic causes of cerebellar disease?
- Vit B12 deficiency
- Vit E deficiency
- Severe hypothyroidism
What is spinocerebellar ataxia?
- Group of genetic disorders
- characterised by slowly progressive incoordination of gait.
- often associated with poor coordination of hands, speech and eye movements
Types and causes of hyperkinetic movements:
Dystonia
Movement disorder in which a person’s muscles contract uncontrollably.
- contraction causes affected body part to twist involuntarily..
Types and causes of hyperkinetic movements:
Chorea
Chorea
- neurological disorder characterised by jerky involuntary movements affecting especially the shoulders, hips and face.
Types and causes of hyperkinetic movements:
Myoclonus
Spasmodic jerky contraction of groups of muscles.
What are prion’s diseases?
A prion - type of protein that can trigger normal proteins in brain to fold abnormally.
- most common is Creutzfeldt-Jakob disease.
Recap.
What does the basal ganglia consist of?
- Striatum (caudate and putamen)
- Globus Pallidus
- Substantia nigra
- Subthalamic nucleus
What causes the slow / absent movements observed in Parkinson’s disease?
- Progressive loss of dopaminergic neurons in substantia nigra.
- causes less ‘direct pathway’ inhibition.
- more ‘indirect pathway’ stimulation of medial globus pallidus.
- net increases inhibitory output of the GPm to ventrolateral thalamic motor nuclei reduces stimulation of motor cortex.
- leads to slow or absent movements.
Describe how in hyperkinetic disorders of the basal ganglia, excessive movement is observed?
Net decrease of medial globus pallidus (GPm) output.
- reduced inhibition of ventrolateral thalamic motor nuclei.
- greater stimulation of motor cortex.
- excessive motor activity.
Briefly describe what is Huntington’s disease?
some symptoms
- Inherited disease
- causes progressive breakdown (degeneration) of nerve cells in brain.
Symptoms:
- involuntary jerking
- impaired gait
- difficulty with physical production of speech or swallowing.
In Huntington’s disease there is a loss of what neurons?
what does this result in? (4)
Loss of ‘indirect pathway’ putaminal neurones to the lateral Globus Pallidus.
- Increases inhibition of subthalamic nucleus
- Lessens stimulation of the GPm
- lowers GPm output
- causes choreoathetosis
Choreoathetosis
Occurrence of involuntary movements in a combination of:
- chorea (irregular migrating contractions)
- athetosis (twisting and writhing).
Where are the neuron’s mainly affected in Huntington’s disease found?
Neostratium
What causes Huntington’s disease?
Triplet expansion (CAG) in the Huntingtin gene, Chr4, polyglutamine chain in protein.
Parkinson’s disease is characterised by loss of what cells of the substania nigra?
- loss of pigment producing dopaminergic cells of substantia nigra.
What is apraxia?
Loss of ability to execute or carry out skilled movements and gestures, despite having the desire and the physical ability to perform them.
Compare and contrast Ataxia and Apraxia?
Ataxia - you want to perform an activity and ask you try to you realise that your movements are really uncoordinated.
Apraxia - you wake up and even though you a willing and able to do an activity, you can’t do it.
Dysfunction where might result in Apraxia?
Dysfunction of cerebral hemispheres of the brain.
- esp. parietal lobe, can arise from many diseases or damage to the brain.
State examples of cortical diseases which may cause apraxia? (3)
- Infarction
- Tumour
- Neurodegenerative disease
What are causes of gait apraxia? (2)
- small vessel ischaemia
- hydrocephalus
State some different types of Apraxia?
- Ideomotor apraxia
- Ideational apraxia
- Limb-kinetic apraxia
- constructional apraxia
Describe Ideomotor apraxia?
Neurological disorder characterised by inability to correctly imitate hand gestures and voluntarily mime tool (e.g. pretend to brush one’s hair)
What is the cortical localisation for ideomotor apraxia?
Motor association cortex
Describe ideational apraxia?
- Neurological disorder
- explains loss of ability to conceptualise, plan and execute complex sequences of motor actions involves in use of tools
What cortex of brain is affected in ideational apraxia?
Pre-frontal cortex
Describe limb-kinetic apraxia?
example scenario?
Inability to make precise or exact movements with a finger, arm or a leg.
e.g. inability to use screwdriver when person knows how to use one.
What cortex of brain is affected in limb-kinetic apraxia?
Primary motor cortex
What is constructional apraxia?
Affects person’s ability to draw or copy simple diagrams or to construct simple figures.
What lobe of the brain is affected in constructional apraxia?
Parietal lobe
What are the most common causes of acquired apraxia?
- Brain tumor
- neurodegenerative illness
- dementia
- stroke
- traumatic brain injury
