Chronic IH: Idiopathic IH and Secondary IH
What’s the difference between pseudotumor cerebri, idiopathic intracranial hypertension and secondary intracranial hypertension?
High intracranial pressure has been given several names through the years. Intracranial hypertension (IH) is the general medical term that encompasses all forms of high intracranial pressure.
In the 1890s, a German physician named Heinrich Quincke coined the term “pseudotumor cerebri” to describe a neurological disorder which he believed had all the symptoms of a brain tumor, but without the presence of an actual tumor. The “false brain tumor” that Quincke identified more than a century ago is known today as idiopathic intracranial hypertension (IIH).
IIH is one of two forms of chronic intracranial hypertension. Idiopathic intracranial hypertension occurs spontaneously, without warning. The term “idiopathic” refers to the fact that in IIH, there is no identifiable cause that triggers the raised intracranial pressure. Idiopathic intracranial hypertension is sometimes also called primary intracranial hypertension. (Benign intracranial hypertension, like pseudotumor cerebri, is another older term for IIH but it does not accurately describe the disorder or its consequences.)
The other form of chronic IH is known as secondary intracranial hypertension (SIH). In contrast to IIH, secondary intracranial hypertension always has an identifiable cause. Something–head trauma, an underlying disease, a reaction to a certain drug–directly causes the intracranial hypertension. An SIH cause can also be a physical obstruction (such as a blood clot in the cerebral venous sinus), which causes IH by literally blocking the normal flow of CSF.