Pseudotumor cerebri pathophysiology
|
Pseudotumor cerebri Microchapters |
|
Diagnosis |
|---|
|
Treatment |
|
Case Studies |
|
Pseudotumor cerebri pathophysiology On the Web |
|
American Roentgen Ray Society Images of Pseudotumor cerebri pathophysiology |
|
Risk calculators and risk factors for Pseudotumor cerebri pathophysiology |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief:
Overview
Pathophysiology
Pathogenesis
The exact pathogenesis of pseudotumor cerebri is not completely understood. Idiopathic intracranial hypertension or pseudotumor cerebri is defined by the symptoms of increased intracranial pressure which is the common final pathway of all IHH etiologies, without any evidence of Intracranial mass lesions. (1uptodate)
Any theory regarding the pathophysiology of this disease should explain the following statements:
- High incidence rate in women with childbearing age
- Reduced conductance to CSF outflow(25 wall)
- Normal ventricle size and lack of hydrocephalus(26 wall)
- No evidence of cerebral edema(27 wall)
The basic etiology behind every IIH pathogenesis theory is Increased production of CSF and reduced resorption.
Cerebrospinal fluid lifecycle: 600 ml of CSF is produced daily. this amount will decrease with age.(17) 2/3 of this fluid is produced by choroid plexus of brain ventricles and the other 1/3 by ependymal lining of ventricles.(15) CSF production is a energy consuming process and use Na/K ATPase to flow ions into lumen and attract water with it through aquaporins.(18) CSF flows out to subarachnoid granulation where it can be absorbed.(19) Some part of CSF flows into lymphatics of head and neck and some part absorbed through spine.(20-22)
CSF Changes in Pseudotumor Cerebri: The production of CSF is constant so the main problem in IIH pathogenesis is related to CSF reabsorbtaion. Many studies suggested that increased resistant to CSF reabsorbtion in the main cause of IIH disease.(28-32-33-34-35)
The venous sinuses: It has been suggested that primary or secondary venous outflow narrowing or stenosis can cause IHH. (38-47) One of the causes of venous sinuses narrowing is thrombotic event. In one of the IIH studies the amount of MTHFR was higher in IIH patients (38%) in comparison to control group (14%). This result suggests that thrombophilia-hypofibrinolysis can cause IIH. One other study demonstrated that fibrinogen level and RBC aggregation is higher in II patients.(57-59)
Sodium and Water Regulation: Aldosterone and Vasopressin: In addition to kidneys, aldosterone also works on epithelial cells of choroid plexus inhancing the Na-K ATPase and CSF production. Based on this, primary or secondary hyperaldosteronism can cause IIH.(60-61) Like aldosterone, AVP also works on kidneys and CNS but it seems that the rise in AVP in IIH is the result of increase intracranial hypertension not the cause.(68-69-70)
Obesity: Some evidences suggest that obesity can increase intra abdominal and intra cranial pressure and have a role in pathogenesis of IHH. (106 uptodate) In a study on 7 obese women with IHH it was seen that weith loss improved their symptoms.(107 uptodate) In the other hand higher level of leptin (a protein released from adipose tissue) was found in IHH patiets.(125uptodate) Obesity also cause increased plasminogen activator inhibitor activity which leads to hypofibrinolysis(58 mcgeeney) In the other hand the amount of ANP and BNP decreases as BMI increases.(71mcgeeney)
Vitamin A: both hypo and hypervitaminosis A are suggested to be related to IIH pathogenesis. Hypovitaminosis A can interfere with reabsorbtion of CSF and hypervitaminosis A can activate the mineralocorticoid receptor.(98-99)
Corticosteroids: Corticosteroid withdrawal can decrease CSF absorbtion and increase intracranial pressure.(115)
Sex hormones: In one study regarding IIH etiology which was done on 8 men with this disease, Four of them had abnormal FSH and LH level, 2 of them had estradiol abnormalities and seven of them had reduced testosterone level.(127 uptodate) Progesterone can increase CSF with its mineralocorticoid effect and estrogen can reduce cellular tight junctions and reduce CSF permeability(57-117)
Genetics
[Disease name] is transmitted in [mode of genetic transmission] pattern.
OR
Genes involved in the pathogenesis of [disease name] include:
- [Gene1]
- [Gene2]
- [Gene3]
OR
The development of [disease name] is the result of multiple genetic mutations such as:
- [Mutation 1]
- [Mutation 2]
- [Mutation 3]
Associated Conditions
Gross Pathology
On gross pathology, [feature1], [feature2], and [feature3] are characteristic findings of [disease name].
Microscopic Pathology
On microscopic histopathological analysis, [feature1], [feature2], and [feature3] are characteristic findings of [disease name].