she said her headache started abruptly a week previously and that this co - occurred with impaired color perception and blurred vision . when she visited our office , she still complained of blurred vision , especially in her left eye , but her vision was 20/20 and color vision was normal in both eyes . both of her optic discs were swollen and goldmann perimetry showed enlarged blind spots bilaterally [ figs . lumbar puncture was performed and the opening pressure was checked at 130 mm h2o ; the csf composition was normal . brain magnetic resonance imaging ( mri ) and magnetic resonance venography ( mrv ) neuroimaging results were also normal ; and no empty sella , globe flattening , or venous narrowing was detected by brain imaging . she was on no medication regimen , and had no other significant past medical history . we recommended another lumbar puncture , but she refused ; and thus , because of the definite bilateral disc swelling and headache , which are typical features of iih , we prescribed acetazolamide 500 mg twice daily . a week later , she told us that her headache and blurred vision had subsided , and thus , we gradually tapered the dosage during follow - up . at last visit , 4 months after the onset of her symptoms , both optic discs were normal without any swelling or temporal pallor and she no longer complained of a headache or visual symptoms . the sizes of enlarged blind spots were prominently reduced on follow - up goldmann perimetry [ fig . bilateral optic disc edema with surrounding retinal nerve fiber layer swelling in a 52-year - old woman ; who presented with blurred vision , impaired color perception , and headache . ( a ) bilateral disc swelling with a blurred disc margin in a 15-year - old girl who presented with headache , pulsatile tinnitus , and transient visual obscuration ( b ) visual field tests of the patients before and after treatment with acetazolamide . initial visual fields showing the presence of enlarged blind spots in both eyes ( a and c)follow - up visual fields demonstrating diminished enlarged blind spot sizes after treatment ( b and d ) a 15-year - old girl presented with a headache , pulsatile tinnitus , and transient visual obscuration of 2 months duration . she had bilateral disc swelling with a blurred disc margin and goldmann perimetry showed enlarged blind spots in both eyes [ figs . brain mri / mrv was also normal with no empty sella , globe flattening , or venous narrowing . a few days after the initial lumbar puncture , the puncture was repeated , and the rechecked csf opening pressure was 205 mm h2o . even though her icp was still within the normal range , iih was strongly suspected since she had several typical symptoms , and she told us her headache improved after the lumbar punctures . three months after her first visit , she had minimal swelling of both optic discs , but did not have headache or tinnitus . currently ( at 7 months after her initial visit ) , she is on acetazolamide 250 mg twice daily . she said her headache started abruptly a week previously and that this co - occurred with impaired color perception and blurred vision . when she visited our office , she still complained of blurred vision , especially in her left eye , but her vision was 20/20 and color vision was normal in both eyes . both of her optic discs were swollen and goldmann perimetry showed enlarged blind spots bilaterally [ figs . lumbar puncture was performed and the opening pressure was checked at 130 mm h2o ; the csf composition was normal . brain magnetic resonance imaging ( mri ) and magnetic resonance venography ( mrv ) neuroimaging results were also normal ; and no empty sella , globe flattening , or venous narrowing was detected by brain imaging . she was on no medication regimen , and had no other significant past medical history . we recommended another lumbar puncture , but she refused ; and thus , because of the definite bilateral disc swelling and headache , which are typical features of iih , we prescribed acetazolamide 500 mg twice daily . a week later , she told us that her headache and blurred vision had subsided , and thus , we gradually tapered the dosage during follow - up . at last visit , 4 months after the onset of her symptoms , both optic discs were normal without any swelling or temporal pallor and she no longer complained of a headache or visual symptoms . the sizes of enlarged blind spots were prominently reduced on follow - up goldmann perimetry [ fig . bilateral optic disc edema with surrounding retinal nerve fiber layer swelling in a 52-year - old woman ; who presented with blurred vision , impaired color perception , and headache . ( a ) bilateral disc swelling with a blurred disc margin in a 15-year - old girl who presented with headache , pulsatile tinnitus , and transient visual obscuration ( b ) visual field tests of the patients before and after treatment with acetazolamide . initial visual fields showing the presence of enlarged blind spots in both eyes ( a and c)follow - up visual fields demonstrating diminished enlarged blind spot sizes after treatment ( b and d ) a 15-year - old girl presented with a headache , pulsatile tinnitus , and transient visual obscuration of 2 months duration . she had bilateral disc swelling with a blurred disc margin and goldmann perimetry showed enlarged blind spots in both eyes [ figs . brain mri / mrv was also normal with no empty sella , globe flattening , or venous narrowing . a few days after the initial lumbar puncture , the puncture was repeated , and the rechecked csf opening pressure was 205 mm h2o . even though her icp was still within the normal range , iih was strongly suspected since she had several typical symptoms , and she told us her headache improved after the lumbar punctures . three months after her first visit , she had minimal swelling of both optic discs , but did not have headache or tinnitus . currently ( at 7 months after her initial visit ) , she is on acetazolamide 250 mg twice daily . johnston et al . , reported a series of atypical iih patients , one of which was a 13-year - old boy whose disc edema rapidly resolved after lumboperitoneal shunt insertion even though his initial csf pressure was normal . subsequently , green et al . , reported the case of an 18-year - old woman iih patient with a normal icp , and introduced the term  normal pressure iih  to describe this variant of iih . the mechanism responsible for this iih variant is not known , but it has been proposed that patients may have different susceptibilities to icp levels . repeat lumbar puncture or 24-h icp monitoring is occasionally suggested in patients who are suspected of having iih but with a normal icp by single lumbar puncture . we recommended a second lumbar puncture to both of our patients , but our adult patient refused , and repeat lumbar puncture in the 15-year - old girl confirmed a normal icp . we had considered continuous icp monitoring in both cases , but we decided to start treatment first because they complained of a headache and showed definite bilateral disc swelling with related visual field defects . papilledema is a warning sign of an elevated icp and ophthalmologists should be alert when a patient has papilledema without any symptoms . it is known that papilledema is usually reversible with appropriate treatment in iih patients , but untreated papilledema can result in progressive and irreversible visual loss . iih patients with persistent signs and symptoms can be treated using medical or surgical approaches , and carbonic anhydrase inhibitors , such as , acetazolamide , are perceived as the main medical treatment of iih . surgical interventions , such as ventriculoperitoneal / lumboperitoneal shunting or optic nerve sheath fenestration , are currently the mainstay treatments when medical therapy is insufficient . as both of our patients responded well to acetazolamide , surgical intervention was not considered in our patients . although increased icp , defined as an opening pressure of over 250 mm h2o , is one of the diagnostic criteria of iih , it should be kept in mind that some patients may have discs that are more susceptible to lower icp than others . even when a patient 's icp is within the normal range , the possibility of iih should always be considered in a patient with typical clinical features of iih , such as , papilledema , a headache , pulsatile tinnitus , and blind spot enlargement by visual field testing .
idiopathic intracranial hypertension ( iih ) is a condition of raised intracranial pressure ( icp ) in the absence of space occupying lesions . 
 icp is usually measured by lumbar puncture and a cerebrospinal fluid ( csf ) pressure above 250 mm h2o is one of the diagnostic criteria of iih . 
 recently , we have encountered two patients who complained of headaches and exhibited disc swelling without an increased icp . 
 we prescribed acetazolamide and followed both patients frequently ; because of the definite disc swelling with iih related symptoms . 
 symptoms and signs resolved in both patients after they started taking acetazolamide . 
 it is generally known that an elevated icp , as measured by lumbar puncture , is the most important diagnostic sign of iih . 
 however , these cases caution even when csf pressure is within the normal range , that suspicion should be raised when a patient has papilledema with related symptoms , since untreated papilledema may cause progressive and irreversible visual loss .