I had ventricular shunt surgery for advanced hydrocephalus in Apr., and was recovering well for a few months, but some symptoms are coming back, mainly lack of focus and short-term memory loss. My neurologist ordered a new m.r.i. which found a subdural hematoma, and wants me to get in with my neurosurgeon asap. How dangerous is this, and what can be done to correct it? (My neorsurgeons office was closed by the time I got this info.)