Ultrasound of the optic nerve showing<unk>  The diagnosis may be suspected on the basis of the history and examination. To confirm the diagnosis, as well as excluding alternative causes, several investigations are required; more investigations may be performed if the history is not typical or the person is more likely to have an alternative problem: children, men, the elderly, or women who are not overweight. Investigations Neuroimaging, usually with computed tomography (CT/CAT) or magnetic resonance imaging (MRI), is used to exclude any mass lesions. In<unk>  these scans typically appear to be normal, although small or slit-like ventricles, dilatation and buckling of the optic nerve sheaths and "empty sella sign" (flattening of the pituitary gland due to increased pressure) and enlargement of Meckel's caves may be seen. An MR venogram is also performed in most cases to exclude the possibility of venous sinus stenosis/obstruction or cerebral venous sinus thrombosis. A contrast-enhanced MRV (ATECO) scan has a high detection rate for abnormal transverse sinus stenoses. These stenoses can be more adequately identified and assessed with catheter cerebral venography and manometry. Buckling of the bilateral optic nerves with increased perineural fluid is also often noted on MRI imaging. Lumbar puncture is performed to measure the opening pressure, as well as to obtain cerebrospinal fluid (CSF) to exclude alternative diagnoses. If the opening pressure is increased, CSF may be removed for transient relief (see below). The CSF is examined for abnormal cells, infections, antibody levels, the glucose level, and protein levels. By definition, all of these are within their normal limits in<unk> . Occasionally, the CSF pressure measurement may be normal despite very suggestive symptoms. This may be attributable to the fact that CSF pressure may fluctuate over the course of the normal day. If the suspicion of problems remains high, it may be necessary to perform more long-term monitoring of the ICP by a pressure catheter. Classification The original criteria for<unk>  were described by Dandy in 1937. + Dandy criteria 1 Signs & symptoms of increased ICP – CSF pressure >25 cmH2O 2 No localizing signs with the exception of abducens nerve palsy 3 Normal CSF composition 4 Normal to small (slit) ventricles on imaging with no intracranial mass They were modified by Smith in 1985 to become the "modified Dandy criteria". Smith included the use of more advanced imaging: Dandy had required ventriculography, but Smith replaced this with computed tomography. In a 2001 paper, Digre and Corbett amended Dandy's criteria further. They added the requirement that the person is awake and alert, as coma precludes adequate neurological assessment, and require exclusion of venous sinus thrombosis as an underlying cause. Furthermore, they added the requirement that no other cause for the raised ICP is found. + Modified Dandy criteria 1 Symptoms of raised intracranial pressure (headache, nausea, vomiting, transient visual obscurations, or papilledema) 2 No localizing signs with the exception of abducens (sixth) nerve palsy 3 The patient is awake and alert 4 Normal CT/MRI findings without evidence of thrombosis 5 LP opening pressure of >25 cmH2O and normal biochemical and cytological composition of CSF 6 No other explanation for the raised intracranial pressure In a 2002 review, Friedman and Jacobson propose an alternative set of criteria, derived from Smith's. These require the absence of symptoms that could not be explained by a diagnosis of<unk> , but do not require the actual presence of any symptoms (such as headache) attributable to<unk> . These criteria also require that the lumbar puncture is performed with the person lying sideways, as a lumbar puncture performed in the upright sitting position can lead to artificially high pressure measurements. Friedman and Jacobson also do not insist on MR venography for every person; rather, this is only required in atypical cases (see "diagnosis" above).
Idiopathic intracranial hypertension
Brain tumor
Intracranial hypertension syndrome
Arachnoiditis
Meningitis
Subarachnoid hemorrhage
Migraine
Infectious intracranial aneurysm