Idiopathic Intracranial Hypertension (IIH) or Pseudotumor Cerebri is a neurological disorder. It affects predominantly obese women of childbearing age. The primary problem is chronically elevated intracranial pressure (ICP), and the most important neurological manifestation is papilledema, which may lead to progressive optic atrophy an blindness.
Pathophysiology :
A dominant early theory concerning the pathogenesis of elevated Idiopathic Intracranial Hypertension (ICP) in these patients was cerebral edema. Against this the fact that no altered level of alertness, cognitive impairment, of focal neurological findings are associated with the elevated ICP. In addition, no pathologic signs of cerebral edema have been documented in these patients. Early reports describing edema were later considered to represent fixation artifact (ie, from tissue preparation) rather than in vivo edema.
Current theories include increased resistance to cerebrospinal fluid (CSF) outflow reabsorption is thought to occur by bulk flow. Alternatively, occult cerebral venous outflow abnormalities may produce Idiopathic Intracranial Hypertension (IIH).
- CSF production rate (cc/min) should be equal to the CSF reabsorption rate.
- If production exceeds absorption, ICP rises until it exceeds mean arterail pressure, which, if sustained, would be fatal
- In IIH the production rate equals the absorption rate; however, a higher than normal pressure is required to achieve this owing to the increased resistance at the arachnoid granulation.
Idiopathic Intracranial Hypertension Epidemiology
Mortality / Morbidity :
- IIH is associated with no known specific mortality risk. The increased mortality rate associated with morbid obesity has a selective expression int this group because of the strong predilection of the disease to affect obese female.
- Visionloss
The only permanent morbidity in IIH is vision loss from decompensation of papilledema with progressive optic atrophy. The frequency and degree to which visiual loss accurs in this disease is difficult to establish form the existing literature.
Race :
No evidence exists to suggest predilection for any particular racial or ethnic group apart from variation in the prevalence of obesity in the different groups.
Sex :
- Obese females of childbearing age are affected selectively by IIH
- Specific numbers are available from epidemiological studies: Radhakarishnan ( Mayo series, 1993) female-to-male ration 8:1 (N=9); Radhakrishnan (Libyan series 1993) Female-to-male ration 8:1 (N=76)
Age:
The highest incidence is among obese women of "childbearing age". For most of the epidemiological series this was between 15-44 years
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