Pseudotumor Cerebri, also known as Idiopathic Intracranial Hypertension (IIH) or benign intracranial hypertension (BIH), is when the pressure increases inside the craniumat the level of the CSF.

In ophthalmology we see primarily two signs: swelling of both optic nerves (papilledema) and occasionally an abducens palsy (CN6). The abducens nerve pops out the bottom of the pons and runs up the floor of the cranium before taking a 90-degree turn to enter the cavernous sinus. Something about this course makes it more susceptible to high ICP.

Causes
You can think of PTC as analogous to glaucoma in the eye. Both CSF and aqueous have similar fluid content, both are susceptible to diamox. While glaucoma occurs from a resistance to outflow at the trabecular meshwork, pseudotumor cerebri occurs from resistance to outflow at the arachnoid villi.

The precipitating cause can be many fold … anywhere from idiopathic, to secondary to drug side effects, to a temporary dural or transverse venous thrombus.

Modified Dandy Criteria (from Walter Dandy circa 1930s) for PTC
1. Signs/Symptoms of increased ICP
2. No neurological signs except for 6th nerve abducens palsy
3. Normal CSF lab values
4. Normal or small ventricals on imaging without signs of other abnormal masses

Drugs that Can Precipitate:
Pregnancy and estrogen treatment
Antibiotics (tetracycline)
Vitamin A (including polar bear liver which has very high levels of vitamin A)
Nalidixic Acid