This is a relatively common condition that too often seems to elude diagnosis, but can not be ignored once discovered. Often the presenting complaint is headache. Sometimes headache is not so prominent. The neurologist is called when the eye doctor in the process of an otherwise “routine” evaluation discovers pressure on the optic nerve. Imaging of the head doesn’t show a tumor or a mass in the brain. But the optic nerve is responding as if one was there anyway. This is pseudotumor cerebri.
Also known as Benign Intracranial Hypertension. A misleading name if ever there was one. What can possibly be benign about a condition which left untreated might result in blindness. Once the diagnosis is delivered, hindsight compels the patient to recall that yes they had in fact been less aware of objects to their right or left. In other words the peripheral vision had been diminishing over months if not years. A visual fields test by an eye doctor would disclose the extent of Vision loss and establish a baseline to gauge the treatment course.
So does pseudotumor predispose to actual tumor? No. What is happening in pseudo-tumor is an increase in intracranial pressure for reasons that are often not clear. The usual balance of production and removal of cerebrospinal fluid maintains a certain equilibrium. When this is disrupted, the non pliable skull will not expand to accommodate the increased fluid volume. The result is an increase in pressure exerted on the most vulnerable structures in the head. The optic nerves specifically. But other, perhaps more pain sensitive structures, respond as well. The result is headaches, sometimes postural: worse on standing.
The predisposing factors appear to be recent weight gain. This is not to say it is never seen in individuals of thin build. Again, the abnormality is either in the over-production of cerebrospinal fluid exceeding the ability of the body to remove the extra fluid. Blockage of the exit points may likewise result in the same symptoms appearing. Another factor is the ingestion of certain fat soluble vitamins. Vitamin A is associated most often. Among medications causing the condition, tetracycline is high on the list but other medicines may cause the same picture.
Prevalence is about 1 per 100,000. It may be as high as 4-10 per 100,000 in overweight females under the age of 44 years. Besides headache and Vision loss, other symptoms include ringing in the ears, neck and shoulder pain, pain on moving the eyes, nausea and vomiting, and dizziness. Even treated, the recurrences rate is rather high.
Diagnosis requires a spinal tap. Treatment begins with medication to reduce production of cerebrospinal fluid and to increase its excretion. Some patients require repeated spinal taps to draw off excess fluid. If the only remedy appears to be repeated spinal taps, consideration for a neurosurgical intervention with a shunt placement is made. The shunt remains in place and drains fluid continually. Complications arise from the fact a foreign body (the shunt) now resides in the body. It becomes susceptible to infection, or mechanical twisting. Revision of the shunt has to be undertaken periodically.
Headaches, recent weight gain, and vision changes should all prompt a formal vision evaluation with emphasis on visual field testing. Increased pressure on the optic nerve will require imaging of the head, and a spinal tap. Delaying attention to this may compromise peripheral vision permanently, or lead to total blindness eventually.