Intracranial hypertension

Intracranial hypertension (IH) is a condition of increased pressure inside the skull. It results from increases in the volume of the brain, blood or spinal fluid within the fixed volume of the cranium (skull). These changes can be caused by brain swelling (meningitis or encephalitis), excess cerebrospinal fluid production, poor spinal fluid drainage, excess blood flow to the brain, and poor drainage of blood from the brain.

Signs and symptoms
The most common sign is papilledema (swelling of the optic nerve sheath).
 * Headache (worse when lying down)
 * Dizziness
 * Nausea / vomiting
 * Altered vision
 * Pulse synchronous tinnitus
 * Stiff neck
 * Back and arm pain
 * Pain behind the eyes
 * Photophobia
 * Exercise intolerance
 * Memory difficulties
 * Radiculopathy, back pain

Diagnosis
There are many tools that can be used in the diagnosis of intracranial hypertension. The most typical method is a lumbar puncture, during which the opening pressure is measured. Opening pressures of 20 H2O or greater are considered abnormal in non-obsese people, 25 H2O or greater in obese people.

However, as pressure can fluctuate and change with position, a more accurate method is a 24 hour intracranial bolt test. This involves inserting an intracranial pressure monitor directly into the cranium to continuously measure pressure over the course of a day. Normal is 7-15 mm Hg in a supine adult.

An MRI can also aid in diagnosis. While generally considered benign, an empty sella can suggest intracranial hypertension, particularly in patients manifesting the symptoms of intracranial hypertension. An empty sella is when the sella, a bony space which holds the pituitary gland, appears “empty” (dark/black) on an MRI. This is because, due to high pressure, the space has been filled with cerebrospinal fluid, flattening the pituitary gland. Patients can also have excess spinal fluid in their optic nerve sheath, which can cause pain behind the eyes and papilledema.

Finally, an MR venogram (a type of MRI that uses contrast to visualizes the veins in the brain) can detect bilateral transverse venous sinus stenosis (TSS), a narrowing of two veins in the back of the head that drain blood from the brain. TSS is found in 83% of cases of intracranial hypertension (compared to 3% of controls). It is not known whether TSS is cause or effect, but there is growing evidence that stenting one of the transverse sinus veins can improve or resolve intracranial hypertension.

Causes
Some causes of intracranial hypertension include: When the cause of increased pressure is unknown it is called idiopathic intracranial hypertension (IIH). It was previously known as pseudotumor cerebri, as the symptoms can mimic that of a brain tumor, even though no tumor is present. It is considered to be a rare disease, affecting just 1 in 100,000 but milder forms may simply go unrecognized.
 * Venous stenosis
 * craniocervical instability
 * Chiari malformation
 * and many more

Treatment
Treatment approaches may depend on the cause and whether it can be identified. In idiopathic cases, treatments can include reducing spinal fluid volume, e.g., through drug treatments like Diamox or surgical treatments like a shunt, or improving venous outflow (blood draining from the brain) by stenting veins in the brain or neck that may be narrowed.

Ketamine is not a standard treatment for intracranial hypertension but was shown to reduce ICP by 30% in a controlled trial of 82 pediatric patients in a trauma setting.

Risk factors

 * Ehlers-Danlos syndrome

Related conditions
It has been observed by some clinicians that ME/CFS and Ehlers-Danlos syndrome patients may have borderline or subclinical intracranial hypertension and benefit from IIH treatments such as Diamox, venous stents, or shunts. While these treatments are rarely used by ME/CFS clinicians they are more commonly employed in the clinical care of EDS patients.

ME/CFS
A case study of a woman presenting with symptoms of CFS and pressure headache, who was diagnosed with borderline intracranial hypertension, found that her CFS symptoms resolved with the placement of a transverse sinus stent. A cross-sectional study of twenty patients presenting at a headache clinic found that a large proportion of patients had borderline intracranial hypertension, with four meeting the diagnostic criteria for IIH (mean cerebrospinal fluid pressure was 19 cm H2O (range 12–41 cm H2O); however, none had clinical signs of IIH. Cerebrospinal fluid drainage via lumbar puncture improved symptoms in 17/20 patients. Researchers speculate that a subset of CFS patients may have borderline cases of idiopathic intracranial hypertension without papillodema, that is, swelling of the optic nerve.

A Swedish study of 234 ME/CFS patients meeting the Canadian Consensus Criteria found that a substantial proportion of patients had signs on their brain MRIs suggestive of intracranial hypertension: 55% had increased diameter of the optic nerve sheath. In addition 80% had cerebellar tonsillar descent that could potentially cause disruptions to spinal fluid flow, and thus increased intracranial pressure. 13.2% had tonsillar herniations severe enough to be considered a Chiari Malformation.

Ehlers-Danlos syndrome
A number of EDS neurosurgeons have observed an association between intracranial hypertension and EDS. Penn State vascular neurosurgeon, Dr. Kenneth Liu, has presented case studies of patients with EDS whose symptoms improve with venous stenting.

Notable studies

 * 2018, The link between idiopathic intracranial hypertension, fibromyalgia, and chronic fatigue syndrome: exploration of a shared pathophysiology - (Full text)

Learn more

 * Video: Venous Stenting in Intracranial Hypertension, Dr. Kenneth Liu