Multiple Sclerosis Flashcards
What is multiple sclerosis?
Autoimmune disorder which leads to loss of myelin from CNS
What are 5 symptoms of MS?
Blurred vision,
fatigue,
difficulty walking,
paraesthesia (numbness/tingling)
muscle spasms (it’s hard to walk bc they’re tired, struggle to see and have spasms/paraesthesia)
How can you stimulate a peripheral nerve?
Electrical stimulus on peripheral nerve activates both sensory and motor axons, causes contraction in muscles (a twitch)
How can stimulation be detected?
Electromyography EMG
What are the two directions of impulse travelling in peripheral nerves called?
Orthodromic (in normal direction of nerve fibre), Antidromic (in opposite direction of nerve fibre)
Explain what is the M wave
The fast response - electrical stimulus directly activates motor neuron - twitch occurs
Explain what is the H reflex
Activation of the sensory axon, action potential travels to spinal cord activating lower motor neurons, which leads to muscle contraction (twitch)
Explain what is the F wave, usually with high stimulus intensity
Activation of a motor axon, the impulse travels antidromically to the spinal cord, when other motor neurons are activated as a result, and respective contractions occur. It is NOT a reflex
How does TMS work?
Transcranial Magnetic Stimulation activates upper motor neurons in the brain, action potential travels down both upper and lower motor neuron pathways, causing muscle contraction
What is the term for the EMG response from TMS?
Motor-evoked potential (MEP)
What is TMCT?
total motor conduction time (also known as MEP latency) - time from brain stimulation to muscle response
What is PMCT?
peripheral motor conduction time (time from spinal cord to muscle)
How can you calculate PMCT?
(M latency + (F latency - 1)) / 2
What is the purpose of the -1 and /2
F latency -1 accounts for the time taken for the impulse to switch direction in the lower motor neuron //// divide by 2 shows an average between fast response and antidromic stimulation
What is CMCT and how do you calculate it?
central motor conduction time (time from brain to spinal cord) // TMCT- PMCT
