Neurophysiological Disorders Flashcards
Structural problems in the CNS
Injury
Carcinoma
Ischaemia
Haemorrhage
What is first line diagnosis for structural problems in the CNS?
CT/MRI
Chemical problems in the CNS
- ionic concentrations
- neurotransmitter production
- neurotransmitter release
- neurotransmitter reception
- neurotransmitter re-uptake
Which is harder to diagnose - structural or chemical CNS problems?
Chemical
“Wiring” problems in the CNS
- may cause epilepsy
- imaging does not help
- need to find precise 3D location
- problems at synapses
- can cause positive feedback/constant firing
Multiple Sclerosis
- affects the CNS (brain and spinal cord)
- myelin sheath damage
- inflammation and scarring of myelin sheath
- myelin attacked by the immune system
- myelin replaced by scarred and sclerotic tissue
- nerve transmission impaired
- some nerves permanently damaged
What is the myelin sheath?
- single cell layer membrane which wraps around the axon
- insulator
Types of MS
- relapsing-remitting
- primary-progressive
- secondary-progressive
- progressive-relapsing
Motor Neurone Disease
- a group of diseases of upper and lower motor neurones
- typical onset in 50s to 70s
- slightly higher incidence in men
- causes peripheral weakness
- can affect speech, swallowing and ocular muscles
- autonomic nervous system spared
- no effect on senses
ALS
- amyotrophic lateral sclerosis
- progressive disorder of nervous system
- upper AND lower motor neuron degeneration at once
- muscle weakness
ALS Lower motor neurone symptoms
- weakness
- muscle twitching (fasciculations)
- atrophy
ALS Upper motor neurone symptoms
- stiffness
- cramping
- weakness
What is it called if only lower motor neurone extending from spinal cord to muscle is compromised?
- motor neuron disease
OR - spinal/progressive muscular atrophy
Progressive bulbar palsy
- lower motor neuron extending from brainstem to muscles of speech and swallowing are compromised
Upper motor neuron involvement only
Primary Lateral Sclerosis
Guillian-Barre Syndrome
- neuropathy
- inflammatory disorder of peripheral nerves
- rapid onset of weakness
- often paralysis of legs, arms, breathing muscles and face
- most recover but length of illness is unpredictable
- often months of hospital care required
- like MS, myelin sheath damaged but in PNS not CNS, possibly by the immune system
Carpal tunnel syndrome
- neuropathy
- much more common
- median nerve
- over-usage
- non invasive treatment = stop activity, splint to hold hand backwards and relieve compression, steroid injections
- invasive treatment = surgery
- numbness/pins and needles/ pain
Myasthenia Gravis
- neuromuscular transmission problem
- not many others
- autoimmune
- receptors get attacked by immune system so less effective
- some types only affect orbicularis oculi (double vision, trouble focusing)
- some types only affect masseter (chewing fatigue)
- treatments = disease modifying drugs, anti-Ach-esterase to prevent recycling of Ach
Muscular Dystrophy
- affecting muscle fibres themselves
- muscle wasting
- 9 types
- genetic, degenerative diseases affecting voluntary muscles
- males from early age = Duchenne Muscular Dystrophy
Duchenne Muscular Dystrophy
- absence of dystrophin (protein keeping muscle cells intact)
- onset: 2-6 years (early childhood)
- generalised weakness, muscle wasting, first hip muscles/ pelvic area/ thighs/ shoulders/ calves often enlarged
- progresses to affect ALL voluntary muscles, heart and breathing muscles
- survival is rare beyond early 30s
- less severe variant is Becker muscular dystrophy
- X linked recessive
- primary affects boys who inherit through mothers
- woman can be carriers but no symptoms
Other types of Muscular Dystrophy
- limb-girdle
- facioscapulohumeral
- myotonic
- ophthalmoplegic
- distal
EMG Amplifier
- typically recorded using a differential amplifier with 2 active electrodes and a common reference electrode
Types of electrodes
- surface electrodes (non invasive)
- concentric needle electrode (cannula forms 1 electrode and core forms the other, invasive, picks up activity from individual motor units)
- single fibre electrode (very fine wire exposed through side of cannula, 25 microns, picking up single muscle fibre activity)
- earth strap (reference electrode, reference can also be surface, velcro strip with mesh inside, dip in saline)
Surface EMG
- limited to superficial muscles
- cannot completely isolate muscles
- attenuated according to thickness of fat and other tissues
- most useful info. from surface EMG is temporal
- common application is gait analysis
Surface EMG Uses
- unacceptable as clinical tool in diagnosis of neuromuscular disease, low back pain
- acceptable for kinesiological analysis of movement disorders for differentiating types of tremors, myoclonus, dystonia, evaluating gait and posture disturbance, psychophysical measures of reaction and movement time
Multi Channel Surface EMG
- 128 channels
- action potentials propagate down nerve so can track them
- lots of measurements made at once so can use it to identify problem in larger area where you don’t know where the problem is
Concentric needle EMG
- stick into muscle
- in specific muscle
- well trained clinicians
- picking up different action potentials in muscle fibres at different times depending on distance from terminal
- can make a number of measurements from this = number of phases, turns, amplitude, duration
Single fibre EMG
- 2 or more muscle fibres within the same motor unit
- need to adjust position of needle to get right location
- IPI = interpotential interval = separation
- healthy individual = intervals not changing in distance
- not healthy = jitter and blocking
- blocking when nothing appears = could be myasthenia gravis for example
- raised jitter/frequency = early sign of neuromuscular transmission disturbance
Surface EMG with nerve stimulation
- recording electrodes (want to position one in center and one further away as other difference in potential will just cancel out)
- earth strap
- stimulating electrodes (
- routine test
- carpal tunnel/ulnar nerve
F response
- late response