The obstruction creates a rise in the intraventricular pressure and causes CSF to flow through the wall of the ventricles into the extracellular fluid within brain. The fluid has roughly the same composition of CSF.Other causes of interstitial edema include but are not limited to communicating hydrocephalus, and normal pressure hydrocephalus. Hydrostatic
Hydrostatic extracellular brain edema is typically caused by severe arterial hypertension. A difference in the hydrostatic pressure within the arterial system relative to the endothelial cells allows ultrafiltration of water, ions, and low molecular weight substances (such as glucose, small amino acids) into the brain parenchyma. The blood-brain barrier is intact usually and the extent of the edema depends on the arterial pressure. The regulatory processes of the brain circulation can function up to systolic arterial pressures of 150 mm Hg and will have impaired function at higher blood pressures. Combined types of cerebral edema
Cytotoxic, osmotic, and vasogenic edema exist on a continuum. The mechanism of the cause of cerebral edema can often overlap between these types. In most instances, cytotoxic and vasogenic edema occur together. When the two edema types evolve simultaneously, the damage of one type reaches a limit and will bring about the other type of injury. For example, when cytotoxic edema occurs in the endothelial cells of the blood–brain barrier, oncotic cell death contributes to loss of integrity of the blood–brain barrier and promotes the progression to vasogenic edema.
Thrombophlebitis is a phlebitis (inflammation of a vein) related to a thrombus (blood clot). When it occurs repeatedly in different locations, it is known as thrombophlebitis migrans (migratory thrombophlebitis). Signs and symptoms
The following symptoms or signs are often associated with thrombophlebitis, although thrombophlebitis is not restricted to the veins of the legs. Pain (area affected)
Skin redness/inflammation
Edema
Veins hard and cord-like
Tenderness

Complications
In terms of complications, one of the most serious occurs when the superficial blood clot is associated with a deep vein thrombosis; this can then dislodge, traveling through the heart and occluding the dense capillary network of the lungs This is a pulmonary embolism which can be life-threatening. Causes
Thrombophlebitis causes include disorders related to increased tendency for blood clotting and reduced speed of blood in the veins such as prolonged immobility; prolonged traveling (sitting) may promote a blood clot leading to thrombophlebitis but this occurs relatively less. High estrogen states such as pregnancy, estrogen replacement therapy, or oral contraceptives are associated with an increased risk of thrombophlebitis.Specific disorders associated with thrombophlebitis include superficial thrombophlebitis which affects veins near the skin surface, deep vein thrombosis which affects deeper veins, and pulmonary embolism.Those with familial clotting disorders such as protein S deficiency, protein C deficiency, or factor V Leiden are also at increased risk of thrombophlebitis. Thrombophlebitis can be found in people with vasculitis including Behçets disease. Thrombophlebitis migrans can be a sign of malignancy – Trousseau sign of malignancy. Diagnosis
The diagnosis for thrombophlebitis is primarily based on the appearance of the affected area.