Clinical Neuorphysiology Flashcards
What is clinical neurophysiology?
Diagnostic speciality that looks at nerve function
What are nerve conduction studies/ electromyography (EMG) carried out?
To investigate problems of peripheral nerve and muscle.
Why is EEG carried out?
Electrical activity within the brain, investigate epilepsy and states of altered consciousness.
What are evoked potentials carried out?
Visual and somatosensory, investigate problems in central pathways
What is examined in nerve conduction studies?
Nerve function by looking at conduction velocity and amplitude
How are sensory studies carried out?
Technique used t stimulate the sensory fibres in the fingers allowing measurement of sensory and motor functions separately
What is the pathophysiology behind myasthenia gravis?
- Antibodies to post-synaptic ACh Receptor.
- Decrease effectiveness of released ACh
How do patients with myasthenia gravis present?
- Present with weakness, fatigue, normal sensation
- Weakness may be generalised
What facial feature is often affected in myasthenia gravis?
Often affects the eyes and present with ptosis and diplopia
How is myasthenia gravis diagnosed?
- Detect Antibodies (takes some weeks, only +ve in 70%)
- Neurophysiology (repetitive stimulation, single fire EMG)
What does routine EMG look at?
Action potentials from whole motor units
How does SF EMG work?
SF EMG uses filter, sensitivity and timebase settings to isolate the action potentials from individual muscle fibres within one motor unit.
How is SF EMG useful?
- Needle can be positioned to record from two fibres within the same motor unit.
- Normally little variation in time of firing between two such fibres.
What results in jitter?
Tight relationship of 2 fibres from the same motor fibre is lost, therefore there is variation in the firing time producing jitter
How can neurophysiology diagnose conditions such as myasthenia, botulism and guide medical treatment?
It can investigate the function of the NMJ
