4 - motor disorders

Question 1

what causes cerebral palsy?

Answer 1

damage to motor control structures of the brain, usually the motor cortex

injury often occurs pre- or peri- fatally

Question 1

what does the motor cortex do?

Answer 1

• issues descending motor commands for muscle activation
• regulates activity levels in spinal cord circuits
• where the upper motor neuron begins

Question 2

what are the results of cerebral palsy?

Answer 2

• stiffness and weakness of muscles
• poor coordination
• affects upper motor neurons
• affects ~2 in every 1000 births

Question 3

what causes stroke?

Answer 3

interruption of the blood supply to the cortex (often motor cortex)

1. cerebral haemorrhage - often results for aneurism
2. cerebral ischaemia - interruption of blood supply to part of brain due to blockage of blood vessel

Question 4

what are the results of stroke?

Answer 4

• upper motor neurons affected
• symptoms depend on extend and location
• FAST (face, arms, speech, time)

Question 5

how can stroke be treated?

Answer 5

goal is to rescue the penumbra (recoverable tissue) by reopening blocked blood vessel (time sensitive)

core - non recoverable

Question 6

what are the most common symptoms of damage to the motor cortex?

Answer 6

fine motor control

because the homunculus has large representations for these activities, so unlikely to be missed by damage, and require co-ordination across sub-regions

Question 7

what is upper motor neuron syndrome?

Answer 7

lack of voluntary control of muscles via lower motor neurons

lack of regulation of LMNs and spinal reflex circuits

reflexes can thus become abnormal

Question 8

what is the Babinksi reflex?

Answer 8

fanning out of toes when the sole of the foot is stroked

indicative of upper motor neuron problem

Question 9

what are conditions caused by damage to the motor cortex?

Answer 9

• cerebral palsy
• stroke
• upper motor neuron syndrom

Question 10

what does the basal ganglia do at rest?

Answer 10

cortex sends signals to basal ganglia structures (striatum- globus pallidus)

this inhibits the thalamus therefore it can’t excite the cortex

causes reduced activation of motor cortex

Question 11

what does the basal ganglia do when excited?

Answer 11

excitation in striatum, which briefly inhibits globus pallid us

thamalus is then disinhibited (excitable)

causes increases excitation of motor cortex

Question 12

what do diseases related to the basal ganglia have in common?

Answer 12

poor selection of appropriate sequences of movement

not selecting motor programmes or inappropriate activation of motor programmes

Question 13

parkinson’s statistics

Answer 13

2nd most common neurodegenerative disease after Alzheimers

affects 3/1000 people, 1/100 in >60s, 1/25 >80s

affects~50% more males than females

10% of cases occur due to mutation of one of several genes

Question 14

what is the cause of symptoms of Parkinson’s disease?

Answer 14

initiation (selection) of movement is impaired, but certain cues/contexts can help

• shuffling gait
• resting tremor
• lack of movement

Question 15

what happens in the basal ganglia in Parkinson’s disease?

Answer 15

burst of dopamine when excited doesn’t occur so no disinhibition

because neurons that produce it die off

therefore thalamus is inhibited, reduced excitation of motor cortex so unable to initiate a movement

Question 16

how to treat Parkinson’s disease?

Answer 16

give L-dopa which increases production of dopamine in dopaminergic neurons

deep brain stimulation

Question 17

how is deep brain stimulation used to treat Parkinson’s disease?

Answer 17

electrical stimulation of basal ganglia structures (globus pallidus) which shrinks down excessive inhibition

resulting in disinhibition of thalamus and excitation of motor cortex

Question 18

what are limitations of deep brain stimulation?

Answer 18

• side effects
• fails to deal with non-motor symptoms (depression, anxiety)
• can make some non-motor symptoms worse

Question 19

what are limitations of using L-dopa to treat Parkinson’s disease?

Answer 19

dopaminergic neurons are dying so eventually there are not enough neurons to make dopamine and it stops being effective

Question 20

features of cerebellum

Answer 20

contains half number of CNS neurons

10% of total brain weight

projects to almost all upper motor neurons

Question 21

what does damage to cerebellum result in?

Answer 21

ataxia - two types:
- disturbances of posture or gait
- decomposition of movement

voluntary movement loses fluidity and appears mechanical, slow and robot-like

intention tremor (not resting)

Question 22

what is motor neuron disease?

Answer 22

motor neuron (upper and/or lower) degeneration and muscle wasting

• degenerative
• progressive
• incurable

10% of cases have genetic component