Clinical Neurophysiology Flashcards
what investigations can be done for neurophysiology?
Electromyography (EMG)
EEG
Evoked potentials
what two factors of nerve conduction are measured by nerve conduction studies ?
velocity
amplitude
what nerve could be damaged if there was lost sensation in the little and half of the ring finger ?
ulnar nerve
what could wasting for a muscle suggest?
motor fibres damage resulting in the muscle not being used and hence waste away
where does ulnar neuropathy usually occur?
most often at the elbow
what happens to conduction after demyelination ?
conduction block and slowing
describe what happens during conduction block and how the signal gets sent through the nerve?
- the AP jumps between the nodes of ravier between the myelin
- at the demyelination the AP can’t be conducted
- the AP reduces amplitude and velocity
- the nerve adapt during demyelination and redistribute the ion channels to allow the AP to pass through the nerve in the absent of myelin
what three areas of the arm should be stimulated during electrophysiology ?
wrist
below the elbow
above the elbow
what is the main symptom of myaesthenia gravis?
becoming tired more easily since contraction of muscles is less
what is the pathophysiology of myaesthenia gravis?
antibodies bind to the ACh receptor at the synaptic cleft so less ACh can bind and hence decreased effectiveness of ACh
what are the symptoms of myaesthenia gravis ?
weakness fatigue normal sensation diplopia ptosis
what is EMG?
looks at the action potentials of the whole motor units
what is SF EMG ?
looks at the action potential of a single muscle fibre within a motor unit
how is SF EMG useful?
can show if the muscle fibres in the muscle unit are all being stimulated at the same time
what is jitter in relation to muscle fibres ?
when muscle fibres in a motor unit don’t contract at the same time since some axon conduct slower maybe due to demyelination
