Idiopathic intracranial hypertension (IIH), sometimes called benign intracranial hypertension (BIH) or pseudotumor cerebri (PTC) is a neurological disorder that is characterized by increased intracranial pressure (ICP), in the absence of a tumor or other intracranial pathology.

Explanation of terms

The terms "benign" and "pseudotumor" have often been used for this disorder to make clear that the increased ICP is not caused by a tumor or malignancy. However, these terms belie the significance and potential morbidity of the disorder - Thus, it is most appropriately referred to as IIH, and not by its other names. Cases of increased ICP with a known cause can be called secondary intracranial hypertension (SIH), but for the purposes of this article the distinction is not entirely vital.

Diagnosis

The diagnosis of IIH is one of exclusion. The principle sign of IIH, papilledema, can occur because of brain tumors (hence the term "pseudotumor cerebri," which literally means "false brain tumor"), or in other conditions involving increased ICP. Thus, a thorough evaluation is essential to the diagnosis of IIH. Radiologic imaging scans are, as a rule, normal in IIH save for the finding of small or slit-like cerebral ventricles, and what may appear to be an 'empty' sella turcica (caused by flattening of the pituitary under pressure). Cerebrospinal fluid (CSF) is a clear fluid which surrounds and circulates through the brain and spinal cord - it is to the fluid pressure of the CSF that the concept of 'intracranial pressure' refers. The chronic pressure increase in IIH is, as the word "idiopathic" indicates, of uncertain etiology; Most researchers believe that the body's ability to absorb CSF is somehow impaired in those individuals with IIH. A less likely possibility (one that is now generally dismissed) is that of CSF overproduction. Many scientists and doctors believe that there is also some degree of brain swelling or engorgement.

Signs and symptoms

IIH most commonly affects women, particularly overweight women between ages 15 and 45. However, the disorder is not limited to women, and can affect people of all ages and races, both male and female, of all shapes and sizes. The 'cardinal sign' of IIH is papilledema (swelling of the optic nerves), although some atypical patients may not have papilledema. Occasionally patients may present with abducens or other cranial nerve palsies. Symptoms can include severe headache, pulsatile tinnitus, visual disturbances (e.g. diplopia), nausea/vomiting, etc. Most serious is the potential for permanent loss of vision or even blindness. Risk factors include female gender, obesity, excess or deficiency of vitamin A, certain medications, and some other disorders. In cases linked to medication or other clear causes, the line between truly idiopathic IH and secondary IH (as mentioned above) can become quite murky.