L2 - Motor Disorders Flashcards
At rest, what proportion of metabolic energy does the brain require?
1/3
What is the cost of loss of employment and care for those affected by strokes per year? (globally?)
€27 million
What percentage of people have had/will have a stroke at some point in their lifetime?
15-20%
What is kinesis?
Movement without a specific goal in mind - undirected movement
What is akinesia?
Disruption of normal movement
What is dyskinesia?
Same as akinesia; disruption of normal movement, but akinesia’s refer to loss of normal posture (hypo/lack of movement) where dyskinesia’s refer to loss of normal movements (typically hyper/too much movement)
What is hyperkinesia?
Excessive or involuntary movement
What is hypokinesia?
Lack of movement
What is a taxis?
Movement towards a goal; a directed movement
What is ataxia?
Loss of coordination when trying targeted movements
e.g. able to pick up a cup, but not when instructed to.
What is spasticity?
The continuous contraction of muscles which causes stiffness, tightness and interference with gait, speech or movement.
Sitting, almost counter-intuitively, involves what?
Maintenance and active control of posture
What are the two main categories of movement disorders?
Jerky or non-jerky movements
What are two examples of postural disorders?
Dystonia (disruption of muscle tone)
Rigidity
What are two types of jerky movement disorders?
Chorea
Tics
What are two types of non-jerky movement disorders?
Dystonia
Tremor
What allows clinicians to identify the location of damage in the motor system hierarchy?
Differences in the symptoms that result from damages at different levels of the motor system hierarchy
Clinicians begin to recognise clusters of symptoms associated with specific disorders.
Name 4 scales used by clinicians to quantify how bad a disorder is once it has been diagnosed.
Barthel index
Fugl-Meyer
Unified Parkinson’s Disease Rating Scale (MDS-UPDRS)
SARA
Describe the Barthel Index
A scale used to quantify how bad general, non-specific motor symptoms are.
- assesssesimpact of disease on the patient
- 3/4 point scale (no functioning, to reasonable functioning)
- 4 point scale for mobility
Crude scale - takes a lot to move from one point to the next in terms of rehab
Describe the Fugl-Meyer scale.
A scale used to quantify how bad specific diseases are - namely, strokes.
- Assesses patients’ ability to make normal movements.
- measures reflexes, movements and ability to pick up a variety of props/objects.
- very crude scoring system, but rich picture of extent of impairment due to variety of measures
Describe the MDS-UDPRS
Set of 50 questions. Assesses features of motor abilities, as well as the functional impact of the disorder (PD), such as cognition, sleep and impact on family members.
Describe the SARA scale for ataxia.
Ataxia is typically associated with the cerebellum.
Small set of 7/8 different behaviours - finger chasing, gait, stance, sitting, speech disturbance, etc.
0-8, so slightly less crude, as it is easier to move up and down the scale.
What are alpha motor neurons sometimes called, and why?
Final common pathway between the CNS and muscles. Because alpha motor neurons innervate the muscles.
Features of locomotion occur where?
Spinal level, rather than CNS level - this frees up processing power for higher level, voluntary independent skillful actions.
Describe the effects of damage to alpha motor neurons.
Typically, a small cluster of muscles will be severely affected, potentially an inability to move or activate them.
e.g. polio results in loss of control of one leg
Describe the general symptoms of lower motor neuron disorders.
Atrophy
Weakness
Hypotonia
What is atrophy?
Reduction of muscle mass due to lack of usage/activation
What is hypotonia?
Reduction in muscle tone due to loss of alpha motor neurons, and resulting lack of muscle activation.
What is fasciculation?
Muscle twitching
What is hyporeflexia?
Failure of the stretch reflex. Stretching a tendon and activation of muscle to counteract stretch can be reduced or lost if the final pathway is damaged.
What are typical symptoms of upper motor neuron disorders?
- Weakness due to lack of signal reaching muscles
- Hypertonia, increased muscle tone
Why does hypertonia result from AMN syndromes?
When signals are no longer received from the CNS, alpha motor neurons switch on, almost by default, in the absence of any clear instruction. This results in excessive tone. The term hypertonia can be used interchangeably with spasticity and rigidity.
What are SCIs, and are they classed as higher or lower motor neuron syndromes?
They are either, depending on where the injury has occurred and which level it has caused communication blockage.
The spinal cord is a two-way channel. What does this mean for SCIs?
May have impairments in function due to inability to get messages to muscles, but may also have impairments in sensation, due to inability to send sensory feedback.
What is the scope for rehab after SCIs?
Large, but incomplete breaks to the spinal cord still allow for functioning and recovery, but the same cannot be said for complete breaks.
Describe how the location of damage in the hierarchy relates to impairments in the arms and legs.
The nerves feedng the arms come up to the neck. Damage below this level keeps control of the arms intact, but impairs leg movement. Damage above the level of the arm nerves leads to leg and arm impairment.
Disorders of the basal ganglia leads to which two main types of disorders?
Dyskinesia’s (abnormal involuntary movements)
Akinesia’s (loss of voluntary movements)
What are the 4 main elements of the basal ganglia?
- striatum
- globus pallidus
- substantia nigra
- subthalamic nucleus
What are the 4 main symptoms resulting from basal ganglia damage?
- tremor
- chorea’s (involuntary, continuous writhing movements)
- akinesia’s
- bradykinesia
What is bradykinesia?
Slowness of movement or speech
What are chorea’s?
Involuntary, writhing movements
What is the most common disorder of the basal ganglia?
Parkinson’s disease
What proportion of men have had PD by the time they are 75?
2.5%
What are the cardinal symptoms of PD?
- tremor (resting tremor specifically)
- bradykinesia
- postural instability (tipped forwards)
- muscle rigidity
What do PD symptoms result from?
Loss of dopamine in the basal ganglia.
What is the proportion of cortical dopamine found in the basal ganglia?
70%
When do PD symptoms appear, in terms of dopamine loss?
When 70% of dopamine functioning has been lost.
What percentage of PD patients have a genetic version of the disease?
5%
Which environmental factors have been linked to an increased incidence of PD?
Exposure to
- pesticides
- solvents
- metal poisoning
- other pollutants
What lifestyle factor leads to a decreased risk of PD and why?
Smoking! We do not know, its a complicated disorder with multiple causes and factors.
How is PD treated?
Administering dopamine through L dopa, its precursor.
When doing this, 80% of the dopamine supplied will hit the basal ganglia circuit, only 20% won’t.
Gait freezing can be reduced, by what?
tDCS - anodal excitatory stimulation on the impaired side of the brain.
What is HD?
Huntington’s disease - an inherited, progressive disorder which is the most common single gene neurological disorder.
What are the 4 stages of HD?
- pre-manifest: haven’t been diagnosed, but can be via genetic testing
- pre-symptomatic: changes at a biological level (e.g. dopamine loss) but no symptoms
- prodromal: a skillful clinician could detect subtle signs of symptoms that are likely to lead to HD.
- manifest: full diagnosis of symptoms that definitely belong to HD. Functional impairments.
What are the 3 main symptoms of HD?
- motor impairment
- cognitive impairment
- chorea
What are two neurological presentations of HD?
Loss of tissue in the basal ganglia, and also the rest of the brain.
Wider vesicles caused by loss of tissue, apparent even in the prodromal stage.
What is HD caused by?
A protein called Huntingtin, which is produced by a certain number of excessive CAG repeats in the patients’ DNA sequence.
When it is passed on down generations, the number of repeats tends to increase.
What is a ballismus?
An uncontrolled, violent movement.
What is a hemiballismus and what is it caused by?
Violent writhing movements that leads patients to wear themselves out.
Caused by lesions to the subthalamic nucleus (region important for inhibition of excessive movements)
How can PD and HD both be modelled based on the direct and indirect pathways?
PD:
Loss of direct pathway and bias to the indirect pathway
–> poverty of movement
HD:
Loss of neurons in the indirect pathway, excessive activity on direct pathway
–> hyperkinetic disorders
What does the direct vs indirect model of motor disorders not address?
Some symptoms, such as tremor, or non-motor symptoms, such as cognitive behavioural problems.
Damage to the cerebellum leads to what symptoms?
Impaired movement coordination, posture and balance. Patients may overshoot, have intention tremor and loss of skill. Looks like someone who is drunk.
+ more subtle symptoms such as loss of flexibility, adaptation, complex voluntary movements and learning new skills.
The cerebellum receives information from all what?
Senses, including proprioceptive and vestibular information.
What proportion of CNS neurons are estimated to be in the cerebellum?
80% (estimation has increased from 2/3rds)
Why are strokes common in the cerebellum?
Excessive blood supply from the large proportion of neurons.
