Experimental: Active stimulation

Trigeminal nerve stimulation will occur by placement of electrodes (1.25 silver electrodes Bio-Flex BF4, Biotens/Vermed, Buffalo, New York, USA) bilaterally on the V1 branches of the trigeminal nerve (CNV) located on the forehead. Current will be generated from the EMS 7500 stimulator (TENS Products, Inc., Granby, CO) (Class II medical device) and will be set to a level that is clearly perceptible by each patient (i.e. tingling sensation) but not uncomfortable or painful. Current level will be determined for each patient at baseline and will likely be between 4-6 milliampere (mA). Active stimulation will occur at 120 Hz with a 250 μs pulse width and with a duty cycle of 30 seconds on to 30 seconds off.