My Husband Had Posterior Fossa Decompression Surgery In 2002 For

My husband had Posterior fossa decompression surgery in 2002 for an Arnold Chiari malformation. He hasn't been feeling well for 1 1/2 weeks. He's dizzy when laying down or bending over, pressure in the eyes, pressure in the back of his head... His cardiologist said his blood pressure is slightly elevated and he has a stigmatism indicating vertigo, but dizziness with these conditions doesn't happen only in specific positions... My husband and I are both fearful that maybe he has had another shift in his brain or that it's something related to the Chiari malformation. I know only an MRI will answer that question, but "is" it possible the malformation is causing these symptoms? He really doesn't feel good and he's a pretty tough guy...