Intracranial Hypertension (IH) means high pressure inside of the skull.

Intracranial Pressure (ICP) is traditionally measured in millimeters of mercury (mmHg). Most scholars agree that on average:^[1]

• Normal ICP: between 5-15 mmHg

• Mild/Moderate ICP: between 20-30 mmHg, “requires treatment in most circumstances”

• Severe ICP: > 40 mmHg indicates “Severe and possibly life-threatening intracranial hypertension”

IH vs IIH

IH = Intracranial Hypertension from a known cause (such as a tumor). IIH = Idiopathic Intracranial Hypertension is a medical misnomer, by any of its names.

• Once called Benign Endocranial/Intracranial Hypertension, only it was not all that benign.

• It was also known as Pseudotumor Cerebri, because the pressure raises like it would if there were a tumor, but that got confusing.

Idio in Greek, technically means something of itself, and path refers to its pathology, so it is a disease that starts on its own. While, it has never been a condition that starts on its own, it developed the understanding that it was "of unknown origin."

Over the last decade, doctors have found several pathologies (causes) behind those diagnosed with IIH, most of those causes center around arterial/venous hypertension. In fact, they believe that the number of those with such underlying factors to be between 90-100% and they are advocating doing away with this idiopathic misnomer altogether.^[3]

When high intracranial pressure is left untreated, it creates a “pushing effect” towards the only natural escape at the base of the skull (the foramen magnum), and the cerebellar tonsils in the pathway are pushed through the foramen magnum (Acquired Chiari)^[2]

Defined as the pressure-volume relationship of the brain.

The cranium (skull) consists of brain matter, cerebrospinal fluid, and blood (both venous and arterial). Once thought to be a mere hypothesis, but now proven by MRI and accepted as doctrine, the Monro-Kellie Doctrine states, “The sum of volumes of the brain, CSF, and intracranial blood is constant. An increase in one should cause a decrease in one or both of the remaining two.”

Therefore, if an abundance of cerebrospinal fluid exists, both cranial blood volume and brain matter will be forced to deplete. This depletion is usually directed in the path of least resistance – into the sella turcica and through the foramen magnum and into the spinal canal. When the brain matter closest to the bottom of the skull (cerebellar tonsils) is pushed through the foramen magnum and into the spinal canal (an Acquired Chiari Malformation), the tonsils act like a cork and blocks the flow of cerebrospinal fluid (regardless of the size of the tonsillar descent), which in turn, continues to raise intracranial pressure.^[4]

When a space occupying mass exists, the additional matter causes both cranial blood volume and cerebrospinal fluid volume are forced to deplete. Again, taking the path of least resistance resistance – into the sella turcica and through the foramen magnum and into the spinal canal, where the low tonsils are pushed through the foramen magnum and into the spinal canal (an Acquired Chiari Malformation). ^[5]