Pseudotumor Cerebri

Definition and Causes:

Increased pressure within the skull (intracranial pressure) without any obvious cause is called pseudotumor cerebri (Soo-do-too-mur Se-ri-bri) meaning “false brain tumor”. As the name suggests it mimics the signs and symptoms of brain tumors. It often involves cerebrospinal fluid (CSF) outflow resistance, leading to headache and swelling of the nerve to the eye (optic nerve) which can result in vision loss.

The brain and spinal cord are bathed in a clear fluid called cerebrospinal fluid (CSF). This supplies nutrients and oxygen to certain parts of the brain that do not have its own blood supply; and also protects against the trauma/injury by providing a cushion between the hard bony skull and brain matter. It is this fluid which is increased due to some unknown outflow obstruction and causes the disorder.

It is mostly seen in obese adults and children, between the ages of 20-50 years; obese females of childbearing age are more prone to get the disease.

Causes:

There is no known cause for the increased pressure, but it is linked to an excess amount of fluid within the skull which fails to get absorbed into the bloodstream due to unknown outflow resistance.

Symptoms:

The symptoms usually include:

• Headache; mild to moderate originating from behind the eye
• The headaches worsen with eye movement
• Ringing of the ear (tinnitus)
• Nausea, vomiting or dizziness
• Difficulty seeing on the sides
• Blurred or dim vision
• Brief episodes of blindness for few seconds
• Double vision (diplopia)
• Light flashes in the eye
• Neck shoulder and back pain

Investigations and Treatment:

Diagnosis is usually made on the basis of characteristic symptoms, physical examination, imaging, and labs.

History:

• The nature of headaches
• Severity and intensity
• Location with associated symptoms like episodic blindness etc.
• Association with the movement of the eye
• Pain in the neck or shoulders
• Vision changes during headaches

Physical exam will include:

• BP, pulse, and temperature, to exclude other causes of headaches
• After a complete physical examination by the family physician, if needed a referral to an ophthalmologist (eye specialist) or a neurologist (brain specialist) may be considered depending on the patient’s presentation; for a complete eye examination and careful monitoring
• The eye examination will include:
  • Visual field test to determine the normal blind spot of the eye
  • Ophthalmoscopy will be done to see the back of your eye; with a handheld scope with a lens and a light to exclude any swelling of the optic nerve

Investigations:

There may be certain disease conditions which may present with similar symptoms and signs, which are to be excluded and may require some investigations which are:

Labs:

Blood samples would be sent to the lab for following tests to exclude other conditions

• Complete blood count
• Antinuclear antibody (ANA) to Lupus
• Metabolic screening

Lumbar puncture (spinal tap):

• Is a procedure to determine high or low pressure of cerebrospinal fluid (CSF); involves inserting a needle between the two spines of the backbone in the lower back and taking the sample of the fluid; and observing the force with which it may come out. Sometimes the same procedure is used to treat very high pressure by draining the fluid out

Imaging:

• Computed tomography (CT) scan: This device uses x-rays. Patients will lie on a table with the head placed inside of the scanner (resembles a large donut). Computer analysis of x-ray images produces detailed images of the brain that can be obtained in this fashion. The scanning time is usually very rapid (less than 1 minute). In special circumstances, a dye might be injected into the veins just before the scan (CT with contrast). This can sometimes help to identify areas of infection (abscesses), inflammation, tumors, etc.

• Magnetic resonance imaging (MRI): This does not use x-rays. Instead, MRI uses magnetic fields over the body. The device looks like a long cylindrical tube. Patients will lie on a table that slides into the hollow tube. Computer analysis of magnetic fields within the machine can generate images of the internal structures of the body’s organs, including the brain. MRI of the brain will show the normal structures, plus any area(s) of brain injury caused by the inflammation, tumors, previous stroke, etc. Patients must lie still inside an MRI machine for about 30-60 min. In some circumstances, a dye might be injected into the veins (enhanced MRI) just before the scan to help improve the detection of abnormalities. Patients who complain of claustrophobia or discomfort may be given a mild sedative to help relax prior to MRI scanning.

TREATMENT:

Typically begins with medications along with advice to lose weight; there are no activity restrictions and exercise programs are strongly recommended.

– Patients with a visual loss most often are treated with carbonic anhydrase (e.g acetazolamide) to lower the pressure, Loop diuretics (e.g furosemide) is another option

– Patients who do not benefit from standard therapy; a short course of high dose corticosteroids (e.g. prednisolone) may be helpful

– If visual functions continue to deteriorate, and is not improving with steroids then medical management coupled with emergency, surgical intervention is advised

Surgical options include:

• Optic nerve sheet fenestration: There is a membrane that surrounds the optic nerve; the procedure involves making a tiny window in the membrane to drain the excess fluid which causes pressure around the nerve causing vision problems. Often done in one eye although the benefit is seen in both eyes

• Therapeutic lumbar puncture: Sometimes the same procedure as discussed above is used to treat very high pressure by draining the fluid out

• Shunt: Sometimes a long thin tube called a shunt is surgically placed into the brain or lower spine to help drain excess intracranial fluid

Note: All the above surgical procedures are done to reduce the intracranial pressure.

Medications:

Risk Factors and Prevention:

Following factors have been associated:

• Obesity
• Medications such as; growth hormones, oral contraceptives, tetracycline, etc.
• Health problems such as; Addison’s disease, sleep apnea, lupus kidney disease, etc.

Outcome:

• Sometimes the condition disappears on its own within 6 months
• About 10-20%; individuals will have the symptoms recur
• Small percentage of patients may have progressive damage, leading to permanent visual loss