migraines caused by increased spinal fluid?

My 5 year old grandson had surgery 7/2007 for a tethered cord.  All went well with no problems.  He has had severe headaches, typical of migraines even before the surgery but they happen about every two months.  Could they be caused somehow by the fluid in his spine?  The doctors said he still had a little more than they wanted but released him from their care.  We don't want to just assume he has migraines (which run in his family) but the timing seems strange the way they happen every two months.   Would an MRI answer these questions?  Thank you so much.

[DrNoopurMD]

Hi,

MRI will be able to show excessive collection of spinal fluid in the brain or in the spinal cord. However, headaches due to raised intracranial pressure due to excess accumulation of spinal fluid are dull constant headaches and not episodic headaches occurring after every two months. The possibility of migraine cannot be denied but still it will be better to get him evaluated.
Good luck and keep us posted.