Just a reminder, if you have a programmable shunt valve, even if it's a lp shunt, be certain to get the valve reprogrammed immediately after having an MRI done.  The magnets are strong enough, even on the newer MRI's to affect the dial of a programmable shunt valve.  I had an MRI of the brain today, in a new MRI (state of the art) and yet my lp shunt valve's setting had changed from the 90mm it was set at, to 50mm.  That could have resulted in miserable low pressure symptoms. 

Be sure to contact your neurosurgeon before having an MRI so that someone will be available to reset your programmable valve right after the MRI test.