DI from adenoma vs skull base surgery

I am a 38yo f who is s/p posterior fossa craniectomy 10/02 for right CPA arachnoid cyst fenestration.  Prior to surgery had severe dizziness and occasional vertigo. The cyst was enlarging (post CT myelogram) and I had complete resolution of symptoms.  Following surgery noticed galactorrhea and nocturia.  MRI w/ pituitary sequence revealed microademoma approx 6 x 8.  All hormone levels including prolactin normal.  I have recently started experiencing vertigo and dizziness with urine output >3.5 liters/day.  MRI in 3/05 normal with no evidence of cyst recurrence. I have hypernatremia if no access to fluid and become extremely ill very quickly.  My question is are there varying degrees of DI? or could this be related to the skull base/retromastoid crani?  I am able to concetrate my urine but become so ill.  I thought that in DI concetration was not possible.  I take Dilantin 400mg/day for 2 grand mal seizures.  Levels are normal.  Also take hctz for htn.  I would appreciate direction as to what to do.  Visual fields also ok.  I do also have a pineal gland cyst which is loculated and not generally an issue.
Thank you for your time

[CCF-Neuro-M.D.-PW]

Diabetes insipidus can occur after brain surgery or trauma, and is usually self-limiting and resolves after days to weeks. In a minority it may persist, and produces the symptoms that you describe. There may be partial production of ADH resulting in some residual ability to concentrate urine. You should be checked for adrenal insufficiency as this also results in an inability to concentrate the urine and dizziness etc. Treatment for persistent is with DDAVP which can replace the effect of the ADH hormone. Perhaps an alternative blood pressure medication to HCTZ could be used as this will also interfere with your ability to concentrate urine. I would suggest an opinion from an endocrinologist to confirm the diagnosis of cranial diabetes insipidus versus other causes.

Good luck

[ingcam]

I went to my  GP because I am so tired from the lack of sleep because I am up 3-4 times/night voiding.  I must admit that I am thirsty all the time- the issue is that I work 10 hour shifts and my profession does not allow me to satisfy my thirst as needed- and if I did- I couldn't run to the bathroom every hour. My electrolytes were normal but my urine osmolality was less than 1/2 of the lowest normal value.  I really don't know what I should do. I have had to go without fluid before and my muscles start twitching, it becomes difficult for me to speak, my head hurts so bad and I am sick to my stomach.  I also start to decompensate mentally.  I become confused and irritable.  I notice that the dizziness becomes more prominent the longer I go without fluid.  I attempted to do the dehydration test- I was only able to go 4 hours without drinking because I was driving and I honestly couldn't have driven to the lab safely. My sodium level was only slightly elevated.  My questions are:  If my posterior pituitary enhances on MRI does that r/o DI?  I am scared of a transphenoidal, and of taking DDAVP- .I did a 24 hour urine collection and had about 4L- I didn't take my hctz as to not skew the results. My doctor also told me he noticed that I have aniscoria of over 1mm difference R>L and my rt. eyelid droops.  What could cause this?  I am also not sure- but I might be having some seizures. Could high sodium levels cause this?  I work full time and really can't be running to alot of different doctors.  I know this is stupid but I really can't miss work either.  Any suggestions? Thanks