Inclusion Criteria:

1. Diagnosis of IIH by modified Dandy criteria Signs and symptoms of increased intracranial pressure Absence of localizing findings on neurologic examination Absence of deformity, displacement, or obstruction of the ventricular system and otherwise normal neurodiagnostic studies, except for evidence of increased cerebrospinal fluid pressure (>200 mm water). Abnormal neuroimaging except for empty sella turcica, optic nerve sheath enlargement, and smooth-walled non flow-related venous sinus stenosis or collapse106 should lead to another diagnosis Awake and alert No other cause of increased intracranial pressure present
2. Diagnosis of IIH for 6 weeks or less
3. Age 18 to 60 years at time of diagnosis
4. Reproducible visual loss present on automated perimetry (in eye with greatest loss)*
5. Average PMD -2 dB up to -5 dB in the worst eye
6. Presence of bilateral papilledema
7. Able to provide informed consent
8. Women of child-bearing potential must use an acceptable form of birth control during the intervention phase of the study. Acceptable forms include oral contraceptives, transdermal contraceptives,

Exclusion Criteria:

1. Total treatment of IIH of more than one week in the past six weeks
2. Corticosteroids used for IIH treatment within the past six weeks
3. Previous surgery for IIH including optic nerve sheath fenestration, CSF shunting procedures, subtemporal decompression and venous stenting
4. Previous gastric bypass surgery
5. Abnormalities on neurologic examination aside from papilledema and its related visual loss or VI nerve paresis
6. Abnormal CT or MRI scan (intracranial mass, hydrocephalus, dural sinus thrombus or arteriovenous malformation) other than empty sella, unfolded optic nerve sheath, flattened sclera, smooth- walled venous stenosis or secondary Chiari I Malformation
7. CSF pressure less than 200 mm water (patients may have repeat CSF pressure measurements if the first is normal or no opening pressure obtained)
8. Abnormal CSF contents: increased cells: > 5 cells, elevated protein: > 45 mg%, low glucose: < 30 mg% (If the lumbar puncture produces a cell count compatible with a traumatic needle insertion, the patient does not need to be excluded if the CSF WBC after correction is 5 wbc/mm3 or less- see Operations Manual for calculation)
9. Intraocular pressure currently > 28 mm Hg or > 30 mm Hg at any time in the past
10. Refractive error > +/- 6.00 sphere or > +/- 3.00 cylinder in either eye
11. Other disorders causing visual loss except for refractive error and amblyopia including cells in the vitreous or iritis
12. Optic disc drusen on exam or in previous history
13. Presence of diagnosed untreated obstructive sleep apnea
14. Inability to provide reliable and reproducible visual field examination (failure to maintain fixation using an eye monitoring device, more than 15% false positive errors)
15. Abnormal blood work-up indicating a medical or systemic condition associated with raised ICP
16. Study blood results showing severe anemia, leukopenia or thrombocytopenia, renal failure, or hepatic disease, based on the site investigator's judgment
17. Type I diabetes or the presence of diabetic retinopathy
18. Exposure to a drug, substance or disorder that has been associated with elevation of intracranial pressure within 2 months of diagnosis such as lithium, vitamin A, various cyclines, steroid withdrawal (see table in Operations Manual for conditions and drugs)
19. Other condition requiring diuretics, oral, I.V. or injectable steroids or other pressure lowering agents including topiramate (nasal, inhaled, or topical steroids are allowed since the systemic effects are small)
20. Use of topiramate, corticosteroids or diuretics for the treatment of IIH within 2 days of the BEV and during the study
21. Presence of a medical condition such as renal stones that would contraindicate use of the study drugs (acetazolamide)
22. Pregnancy or unwillingness for subject with childbearing potential to use contraception during the first year of the study
23. Nursing mothers are excluded from participation unless willing to discontinue breastfeeding by the baseline visit
24. Presence of a physical, mental, or social condition likely to affect follow-up (drug addiction, terminal illness, no telephone, homeless)
25. Anticipation of a move from the site area within six months and unwillingness to return for follow-up at an IIHTT study site
26. Allergy or to pupil dilating drops or narrow angles precluding safe dilation