Neurophysiological Disorders

Question 1

Structural problems in the CNS

Answer 1

Injury
Carcinoma
Ischaemia
Haemorrhage

Question 2

What is first line diagnosis for structural problems in the CNS?

Answer 2

CT/MRI

Question 3

Chemical problems in the CNS

Answer 3

• ionic concentrations
• neurotransmitter production
• neurotransmitter release
• neurotransmitter reception
• neurotransmitter re-uptake

Question 4

Which is harder to diagnose - structural or chemical CNS problems?

Answer 4

Chemical

Question 5

“Wiring” problems in the CNS

Answer 5

• may cause epilepsy
• imaging does not help
• need to find precise 3D location
• problems at synapses
• can cause positive feedback/constant firing

Question 6

Multiple Sclerosis

Answer 6

• 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

Question 7

What is the myelin sheath?

Answer 7

• single cell layer membrane which wraps around the axon

- insulator

Question 8

Types of MS

Answer 8

• relapsing-remitting
• primary-progressive
• secondary-progressive
• progressive-relapsing

Question 9

Motor Neurone Disease

Answer 9

• 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

Question 10

ALS

Answer 10

• amyotrophic lateral sclerosis
• progressive disorder of nervous system
• upper AND lower motor neuron degeneration at once
• muscle weakness

Question 11

ALS Lower motor neurone symptoms

Answer 11

• weakness
• muscle twitching (fasciculations)
• atrophy

Question 12

ALS Upper motor neurone symptoms

Answer 12

• stiffness
• cramping
• weakness

Question 13

What is it called if only lower motor neurone extending from spinal cord to muscle is compromised?

Answer 13

• motor neuron disease
  OR
• spinal/progressive muscular atrophy

Question 14

Progressive bulbar palsy

Answer 14

• lower motor neuron extending from brainstem to muscles of speech and swallowing are compromised

Question 15

Upper motor neuron involvement only

Answer 15

Primary Lateral Sclerosis

Question 16

Guillian-Barre Syndrome

Answer 16

• 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

Question 17

Carpal tunnel syndrome

Answer 17

• 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

Question 18

Myasthenia Gravis

Answer 18

• 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

Question 19

Muscular Dystrophy

Answer 19

• affecting muscle fibres themselves
• muscle wasting
• 9 types
• genetic, degenerative diseases affecting voluntary muscles
• males from early age = Duchenne Muscular Dystrophy

Question 20

Duchenne Muscular Dystrophy

Answer 20

• 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

Question 21

Other types of Muscular Dystrophy

Answer 21

• limb-girdle
• facioscapulohumeral
• myotonic
• ophthalmoplegic
• distal

Question 22

EMG Amplifier

Answer 22

• typically recorded using a differential amplifier with 2 active electrodes and a common reference electrode

Question 23

Types of electrodes

Answer 23

• 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)

Question 24

Surface EMG

Answer 24

• 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

Question 25

Surface EMG Uses

Answer 25

- 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

Question 26

Multi Channel Surface EMG

Answer 26

- 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

Question 27

Concentric needle EMG

Answer 27

- 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

Question 28

Single fibre EMG

Answer 28

- 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

Question 29

Surface EMG with nerve stimulation

Answer 29

- 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

Question 30

F response

Answer 30

- late response