Category: 6. Evaluation of Elevated Intracranial Pressure

Pseudotumor cerebri syndrome occurs when there is raised intracranial pressure but no known etiology.

These patients present with headaches that are typically worst in the morning when they wake up or when they are lying down. Some other symptoms can include transient vision loss, diplopia, pulsatile tinnitus, nausea, or vomiting. Idiopathic intracranial hypertension (IIH) predominately affects overweight women of childbearing age.

This disorder needs to be rigorously monitored to ensure the ICP is not elevating to levels dangerous enough to cause visual loss. Neurology consult and lumbar puncture are recommended after brain imaging to rule out any brain abnormalities. Treatment with a lumbar puncture to remove excess CSF has been shown to significantly reduce the mean ONSD, indicating that this procedure can lower the ICP to normal values.

Pseudotumor Cerebri (Idiopathic Intracranial Hypertension) Ultrasound Findings

On ocular ultrasound, you will find elevated ONSD measurements > 5 mm. Because this is typically a chronic condition, patients often have signs of Papilledema with optic disc bulging/elevation.

Intracranial hemorrhage occurs when a blood vessel within the skull ruptures or leaks. This condition can occur with physical trauma from a head injury or a ruptured aneurysm. The rapid build-up of blood can increase the ICP so quickly that permanent brain damage can occur if the pressure is not alleviated.

Oftentimes, these patients are comatose and will need emergent lowering of their ICP using pharmacologic (mannitol and hypertonic saline) or neurosurgical decompression.

Intracranial Hemorrhage Ultrasound Findings

On ocular ultrasound, you will find elevated ONSD measurements > 5 mm. Because ultrasound scanning for this condition is often done soon after trauma, there may not be enough time for the elevated ICP to progress to papilledema. Therefore, it is unlikely to see optic disc bulging from an acute intracranial hemorrhage on ultrasound. This contrasts with chronically increased intracranial pressure where the optic nerve swelling can be visualized with ultrasound.

It is important to note that optic disc edema doesn’t always correlate with chronic ICP elevation leading to papilledema. Pseudopapilledema is a benign elevation of the optic nerve head that has no related elevation in ICP. This condition often occurs if there is a small crowded optic nerve head, tilted optic disc, or optic nerve head drusen

Below is a table showing the differences between elevated ICP, Papilledema and Pseudopapilledema.

	Acutely Elevated ICP	Papilledema	Pseudopapilledema
ICP	Acutely high	Chronically high	Normal
ONSD	> 5 mm	> 5 mm	Normal
Optic Disc Bulging	Normal	> 0.6 mm	> 0.6 mm
Example	Early intracranial hemorrhage	Pseudotumor cerebri	Small crowded optic nerve head

In the upcoming sections, we will focus on the two most common pathologies of increased ICP and/or papilledema: intracranial hemorrhage and pseudotumor cerebri (idiopathic intracranial hypertension).

If the ICP is chronically elevated, the cerebrospinal fluid will accumulate within the enlarged optic nerve and cause the optic disc to be raised and bulge into the retina. The combination of a widened ONSD along with optic disc edema is known as papilledema.

On ocular ultrasound, papilledema presents with an ONSD > 5 mm and an optic nerve disc bulging of more than 0.6 mm. This differs from an acute elevation in ICP which only shows an ONSD > 5 mm on ultrasound.

Papilledema can be caused by brain masses, hydrocephalus, stroke or idiopathic intracranial hypertension/pseudotumor cerebri. The presence of unilateral papilledema can signal rare etiologies such as optic neuritis.

Elevated intracranial pressure (ICP) may be a sign of a serious or life-threatening medical condition and it may be helpful to augment the fundoscopic exam with ultrasound to evaluate for papilledema which can be from a chronic increase in intracranial pressure.

Intracranial Pressure Evaluation with Ocular Ultrasound

Ultrasound of the optic nerve sheath diameter has proven to be a reliable, non-invasive, and rapid method to estimate ICP measurement. Any elevation in ICP causes distension of the ocular nerve sheath (>5mm) likely within minutes, making it a prime way to measure ICP in emergent situations