Intraoperative mapping Flashcards
Who first described intraoperative mapping?
Penfield 1937
What is Ojemann stimulation?
60Hz 1ms biphasic current constant bipolar stimulation
What is rheobasis?
Minimum about of current needed to generate an excitation with a long duration pulse
What is chronaxie?
Pulse duration for a stimulating current at twice the rheobasis
What is the difference in resistance between GM and CSF?
GM resistance is 5x CSF, so current from DES can be shunted through CSF instead of GM
What is the difference in resistance between GM and CSF?
WM resistance is 2x GM
Which phenomena make Ojemann stimulation less reliable?
Delayed onset of deficit (e.g. SMA resections)
Dynamic short-term plasticity
Biological long term plasticity
What are false negative stimulations?
Where stimulation did not result in a functional response, but resection resulted in a deficit
What are the causes of false negative stimulation?
Subthreshold stimulation (intensity, duration or shunting)
Stimulation during a refractory period
Wrong testing task
What is the duration of OS?
3 s
What are false positive stimulations?
Where stimulation elicits a functional response but resection did not result in a deficit
What are the causes of false positive stimulation?
Activation of a connected network
What happens to the S1 if regions are overstimulated?
They enlarge
What happens to M1 if motor activities are practised?
The activations get smaller indicating that fewer neurons are needed to control the same movements
