Inside our skull, the spaces within and around the brain are filled with cerebrospinal fluid (CSF). The fluid is constantly being produced and drained so that there is not too little or too much CSF present. In idiopathic intracranial hypertension (IIH), or also known as pseudotumor cerebri, an unknown mechanism causes the CSF to build up and increase the pressure inside the skull. A number of risk factors are associated with this process including being overweight with a recent weight gain. Women are more commonly diagnosed than men. Some medications such as antibiotics in the tetracycline family, Vitamin A derivatives and steroids have also been linked with this process.
Figure: Color photographs of the right and left eyes of a patient with elevated intracranial pressure. The green arrows point to swollen optic nerves in each eye.
The elevated intracranial pressure can cause patients to experience headaches, transient graying of the vision, whooshing sounds that follow the heartbeat, and, in some cases double vision. In addition, untreated and prolonged elevate pressures cause the optic nerve to swell leading to, first, peripheral vision loss and then central vision loss. The vision loss can be severe and become permanent if left untreated.
If IIH is suspected, a complete eye examination including checking for double vision and optic nerve swelling is performed. In addition, visual field testing and special photographs of the eyes will be done. MRI of the brain, a special MRI of the drainage system of the head called a MRV, and a spinal tap will be obtained to rule out tumors, clots, infections, or an inflammatory process. The spinal tap also allows for an estimate of the intracranial pressure.
If the intracranial pressure is high and the MRIs and CSF testing are normal, treatment will depend on the severity of symptoms and vision loss. Any associated medications will be discontinued immediately. If the only underlying cause is weight gain, ultimately the treatment is to lose about 10% of the total weight. If systemic and visual symptoms are only mild, only weight loss will be recommended along with close monitoring. If the symptoms are more prominent, medications (most commonly Diamox, or also known as acetazolamide) to help lower the intracranial pressure in addition to weight loss will be prescribed. In severe cases of severe vision loss and headaches, surgery to place a drain within the skull or spine may be indicated to rapidly reduce the intracranial pressure and pressure around the optic nerves. Sometimes, an “optic nerve sheath fenestration” may be performed to directly relive pressure around the optic nerves if the vision loss is particularly severe without any other symptoms.
Recovery of vision will vary; some patients may experience complete recovery of vision and others may have some amount of permanent vision loss. It is important to maintain the weight loss and a lower intracranial pressure to prevent recurrence of the process and further vision loss.
For more information: view PDF brochure from North American Neuro-Ophthalmology Society (NANOS).