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 these cases, 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. In addition,
there are certain abnormalities, which are typically seen in patients with IIH:
· Partial empty sella
· Flattening of posterior globe
· Distension of perioptic subarachnoid space
· Vertical tortuosity of orbital optic nerve
What is the role of lumbar puncture in the diagnosis
of IIH?
Lumbar puncture should
be done in left lateral decubitus. It confirms the elevated ICP, 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 to be started 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.
Does weight loss help in patients with IIH?
Yes, a weight loss of
5-10% can lead to substantial reduction in reducing 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?
1.
Optic nerve sheath fenestration
2.
CSF diversion procedures such as
theco-peritoneal or ventriculo-peritoneal shunt surgery.
