IDIOPATHIC INTRACRANIAL HYPERTENSION
What is Idiopathic intracranial hypertension (IIH)?
IIH is a condition characterized by raised intracranial pressure (ICP) of unknown etiology. It is also known as benign intracranial hypertension or pseudotumor cerebri.
What are the common symptoms of IIH?
The commonest symptom of IIH is headache. In some cases, visual blurring or double vision may occur.
What is the dreaded complication in patients with IIH?
If IIH is left untreated, there is a threat to vision. Partial or complete loss of vision may occur. In many of the cases with visual loss, vision may not revert to normal even after treatment.
How is the diagnosis of IIH confirmed?
The diagnostic criteria for IIH, including those of the Dandy criteria as described by Dandy in 1937 and later modified, are as follows (source: Medscape)
- There are symptoms and signs of increased intracranial pressure
- There are no localizing neurologic signs (with the exception of a unilateral or bilateral sixth nerve paresis)
- Cerebrospinal fluid (CSF) may show increased pressure, but there are no cytologic or chemical abnormalities
- Neuroimaging reveals no structural cause or hydrocephalus
- No other causes of increased intracranial pressure found through workup
Subsequent additions to these criteria include the following
- The diagnostic lumbar puncture should be performed with the patient in the lateral decubitus position
- Magnetic resonance venography should be included to rule out intracranial venous sinus thromboses
What are the common abnormalities of IIH on MRI/MR Venogram brain?
Brain MRI with gadolinium contrast venogram is the imaging modality of choice, as it can effectively rule out meningitis/meningeal infiltrates, hydrocephalus, mass lesions, cerebral venous sinus thrombosis, etc as a cause of raised ICP. In addition, there are certain abnormalities on MRI brain, which are typically seen in patients with IIH:
- Partial empty sella
- Flattening of posterior globe
- Distension of perioptic subarachnoid space
- Vertical tortuousity of orbital optic nerve
What is the role of lumbar puncture in the diagnosis of IIH?
Lumbar puncture (LP) should be done with patient in left lateral decubitus. LP confirms the elevated ICP, an opening pressure >200 mm water. Lumbar puncture also helps in excluding meningitis.
What is the mainstay of treatment?
Medical treatment with diamox (acetazolamide) is the primary treatment in patients with IIH. Starting dose should be 500-1000 mg per day and a maximum dose of 4 grams per day can be used. Common side effects include paresthesia and tingling.
Diamox to lower intracranial pressure is indicated when there is 1) visual field loss on automated perimetry, 2) transient visual obscurations, 3) binocular diplopia, or 4) pulsatile tinnitus.
Topiramate or frusemide can be used in patients who can not tolerate acetazolamide.
Does weight loss help in patients with IIH?
Yes, a weight loss of 5-10% of body weight can lead to substantial reduction in symptoms of IIH and papilledema.
Do patients with IIH need surgery?
There are a group of patients that need surgery. Patients with severe papilledema with impending threat to visual loss or those presenting with loss of vision require an early surgery. Another group of patients who may need surgery are those that continue to worsen despite being on adequate doses of acetazolamide.
What are the surgical options in IIH?
- Optic nerve sheath fenestration
- CSF diversion procedures such as theco-peritoneal or ventriculo-peritoneal shunt surgery.