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Pseudotumor Cerebri Syndrome
Idiopathic Intracranial Hypertension – Headache – Visual Symptoms – Causes – Drug Therapy – Surgical Solutions
Pseudotumor Cerebri Syndrome (Idiopathic Intracranial Hypertension)
Pseudotumor cerebri syndrome is caused by an increased intracranial pressure. The rise of intracranial pressure may be caused by obstruction of a normal cerebrospinal fluid flow (hydrocephalus), infections, lack of sufficient blood drainage, or brain tumors.
Pseudotumor cerebri name reflects the fact that in spite of the symptoms suggestive for a brain tumor, no such tumor or other brain diseases are found.
Headache in pseudotumor cerebri is almost universal. It tends to be chronic and daily. Correlation between the headache intensity and the severity of this condition is poor. Some patients are not disturbed by headaches at all.
The main concern in this disease is an irreversible damage to the optic nerves with some degree of permanent vision loss. The chance of vision loss and blindness is higher in African Americans.
Causes of Pseudotumor Cerebri Syndrome
The cause of pseudotumor cerebri is not known. For some reason, brain tissues accumulate an excessive amount of water.
It may be associated with some medical conditions, such as iron deficiency, pregnancy, thyroid disease, chronic kidney failure. In occasional cases, pseudotumor cerebri may be precipitated by drugs: vitamin A, tetracycline, corticosteroids, hormonal contraceptives, sulfa drugs, tamoxifen, cyclosporine, and some others.
The majority of pseudotumor cerebri cases are not associated with these risk factors. This is when it is called an idiopathic intracranial hypertension.
The classical patient with idiopathic intracranial hypertension is a young obese female. Male gender and slender body type do not rule out this diagnosis, however.
Symptoms of Pseudotumor Cerebri
Headache in Pseudotumor Cerebri
Headache is the least reliable symptoms for this diagnosis. Even though, majority of patients do complain of chronic headaches, there is no specific headache characteristic, besides its persistence. The pain may be holocranial or it may involve any part of the head.
The headache intensity varies from mild to moderate. Severe headache is not common. The pain is described as throbbing, pressure, or band-like. Sensitivity to light is not unusual. Some patients have very mild headaches.
The most important headache quality is its enjoying persistence from days to months. The headache may persist, or even get worse at night, which is not typical for tension headache.
Depression, chronic sleep deprivation, and sleep apnea cause an identical chronic headache. These conditions have to be considered in chronic headache cases as well. It is especially true for those patients, who don’t fit a typical patient profile for pseutotumor cerebri.
One of the earliest symptoms in idiopathic intracranial hypertension are episodes of a brief transient visual disturbance. It is reported as if someone looks though a ground glass; or it is perceived as dimming of lights.
Blurred vision lasts from seconds to minutes. Some patients report sparkles or flashes of lights in the visual fields. Others compare transient vision loss with a blinking computer screen.
Transient visual symptoms are typically provoked by arising after bending over or by eye movements. These symptoms may be present in either one eye or both. Rapidly progressing rise in intracranial pressure may cause an early persistent loss of visual acuity and hazy vision.
We do not notice blind spots in our visual fields, under normal circumstances. Blind spot normally takes a small portion of the visual field in each eye. Optic nerve swelling (see below) increases the size of the blind spots and some patients become aware of its existence. It might be felt as if something is moving the peripheral vision.
Double vision is another early sign of intracranial hypertension. Expanding brain volume exerts pressure on the nerves supplying the muscles responsible for the eye movements. As a result, the images from the eyes become misaligned, which leads to perception of two images. Closing of one of the eyes relieves this type of double vision, since one of the images is not seen any longer.
The most commonly affected nerve is called abducens. It supplies one muscle in each eye than move the eyeball outwards. The result is a horizontal (two images are side-to-side) double vision. Since the eyes are turned inwards, the double vision is worse while looking far away.
Massive swelling of the optic nerve may lead to edema of the retina and cause distortion of the image seen. It is called metamorphopsia. Even though, it may be perceived as a double vision, it is rather a change in the perceived image shapes. Closing another eye does not relieve this type of “double vision”.
Other Symptoms Of Pseudotumor Cerebri
Approximately half of patients with pseudotumor cerebri notice a pulsating noise in the ears.
Besides generalized headaches, many patients report pain in the eyes, behind the eyes, or around the eyes. This pain is often precipitated by eye movements.
Diagnosis of Pseudotumor Cerebri
The cardinal feature on pseudotumor cerebri is a presence of papilledema, or swelling of the optic nerve disc, on examination. It is detected on the eye examination when an eye doctor looks through the pupil at the back of the eye. Papilledema is expected to involve both eyes.
A visual fields test (perimetry) may reveal a variety of visual field defects with enlarged blind spot as the most common finding. Visual acuity is typically normal.
Severe optic nerve disc swelling may cause a substantial and eventually irreversible loss of vision.
Eye movement abnormalities are usually limited to outward movement restriction on one or both sides (abducens nerve palsy).
Neurological examination is expected to be normal with the exception of the eye problems mentioned above. Presence on neurological findings requires an active search for other causes of the increased intracranial pressure.
Brain MRI is normal in most cases of idiopathic intracranial hypertension. It is done to rule out brain tumors, infections, and hydrocephalus. Sometimes MRI has to be done with a contrast.
Blocked blood drainage from the brain, or venous sinus thrombosis, causes very similar symptoms. Brain MRV is usually done in suspicious cases.
CT head is inferior to MRI for evaluation of pseudotumor cerebri. CT with a contrast is usually performed when MRI is either unavailable or contraindicated.
There are no confirmatory findings on the brain imaging that can either prove or rule out pseudotumor cerebri diagnosis. Some abnormalities on the brain MRI may be only suggestive: empty sella turcica, flattening of the eyeball, fluid accumulation around the optic nerve, narrow brain ventricles, or narrowing of the venous sinuses. These finding may be present in healthy people and they may be absent in the setting of pseudotumor cerebri syndrome.
Lumbar Puncture (Spinal Tap)
Cerebrospinal fluid pressure is elevated in pseudotumor cerebri (above >250 mm in adults and >280 mm in children). The technic of pressure measurement has to be performed correctly because the numbers may be artificially elevated. It has to be done while the patient is lying on the side. It might be elevated in obese people. The cerebrospinal fluid (CSF) pressure is constantly changing. False positive readings are possible.
CSF laboratory analysis must be normal in idiopathic intracranial hypertension. Abnormal color, protein and glucose content as well as elevated cell count point to some other disease.
Treatment of Idiopathic Intracranial Hypertension
Please note the difference between the terms “Pseudotumor Cerebri” and “Idiopathic Intracranial Hypertension”. Pseudotumor cerebri refers to the fact of increased intracranial pressure due to any cause. Once no other disease is found, the diagnosis becomes an “idiopathic intracranial hypertension”. The treatment described below is for the idiopathic condition. Each particular other cause has its own treatment.
Regular follow up evaluations by an ophthalmologist (preferably a neuroophthalmologist) are essential during the treatment.
Weight Loss in Pseudotumor Cerebri
There is a proven benefit of weight loss in papilledema. Several studies report decreased papilledema severity in association with a strict calorie restricted diet and subsequent weight loss. Even though, it is an effective treatment, resolution of papilledema is gradual.
There is a correlation between the degree of weight loss and its therapeutic effect. In general, about 6% of body weight has to be lost in order to achieve resolution of a significant papilledema.
Weight loss is an essential component of the treatment, but it is not sufficient alone. In spite of reduction of optic nerve swelling, the long term outcome for the vision is not changed without drug therapy.
Drug Therapy for Pseudotumor Cerebri
The most commonly employed drug is Acetazolamide (Diamox). Acetazolamide reduces the intracranial pressure by inhibiting CSF production in the brain. It belongs to the class of carbonic anhydrase inhibitors. Its effectiveness for papilledema reduction (especially in combination with weight loss) is proven in randomized trial.
Unlike weight loss alone, acetazolamide is proven to improve visual fields defects over time. The dose of Acetazolamide has to be rather high. A starting dose is 1 gram per day in divided doses with a gradual increase up to 4 grams per day; if needed and tolerated.
The most common side effects are numbness and tingling (sometimes profound), stomach upset, and fatigue. Long term use can cause kidney stones and elevated liver enzymes. Acetazolamide is a sulfa drug, but the structure is different from the antimicrobial medications. Presence of allergy to other sulfa drugs doesn’t necessarily translate into allergy to acetazolamide.
Some doctors use Topiramate (Topamax) instead of acetazolamide. This is an antiepileptic drug with carbonic anhydrase inhibition side effect. The rationale for this drug is the fact that long term use of Topiramate is associated with weight loss.
Side effect profile is similar to acetazolamide. It is usually tolerated worse in high doses due to a significant sedative effect.
Corticosteroids may temporarily alleviate the symptoms of intracranial hypertension. Considering weight gain as a side effect and association of pseudotumor cerebri with steroid withdrawal, it is not a good option.
Therapeutic Lumbar Puncture (Spinal Tap)
Besides diagnostic value, spinal tap has some therapeutic effect in pseudotumor cerebri. There is a temporary improvement in symptoms after some CSF is drained.
Considering the amount of cerebrospinal fluid produced/reabsorbed (about 500 ml per day), the effect is short-lasing. As a treatment, spinal tap is reserved for emergency cases and, occasionally, during pregnancy, in order to delay a surgical intervention.
Surgical Solutions for Pseutotumor Cerebri
Surgical interventions are reserved for medication and weight reduction resistant cases. This option is to be considered in severe forms of pseudotumor cerebri with profound papilledema and rapid onset of vision loss.
Optic Nerve Sheath Fenestration (ONSF)
This procedure is meant to protect the vision. It is never performed for headache management alone. A few cuts or windows are made in the dura mater (hard membrane covering the brain) around the optic nerve. It is done under general anesthesia. CSF drainage through the cuts prevents pressure build up on the optic nerve.
ONSF on one side cause improvement on both sides in some patients. In some patients the effects of this treatment is short-lasting. About one third of the patients experience deterioration of vision in 3 to 5 years after initial improvement.
There are multiple shunting procedures employed in idiopathic intracranial hypertension management. The idea is an ongoing drainage of some CSF in order to decrease the intracranial pressure.
Any kind of shunt is a tube with a pressure valve. One end is placed either in the brain ventricle or inside the lumbar part of the spinal canal. The other end drains the CSF to one of the body cavities: peritoneal (abdomen), pleural (chest), or atrium (one of the heart chambers).
Each solution has pros and cons. In pseudotumor cerebri, the ventricles of the brain are small. Putting a tip of the shunt is sometimes technically challenging. Drainage from the lumbar spine is employed more commonly, but the shunt failure in this location is twice as much as in intraventricular shunting.
Initial response of headaches to shunting is robust (95%). It declines by half in 3 years. Overall shunt failure rate is 75% over 2 years, which requires revisions and/or shunt fixes on a regular basis.
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