DIAGNOSED WITH MENINGIOMAOphthalmologist Carolina Valdivia, MD answers a question about meningioma affecting the optic nerve and the potential outcomes for surgery.  A 62 year-old woman from the USA writes:Dear Dr. Valdivia, I will be undergoing surgery soon to remove a meningioma. Part of the tumor is very close to the optic nerve in my left eye. Will the right eye be impacted immediately or long range if the worst case scenario occurs and I lose sight in my left eye as a consequence of the tumor removal?
Because each case of meningioma has its own unique clinical characteristics, I cannot provide a definitive answer to your question. However, I can give you general information about meningioma that will make you better informed and may allay some of your anxiety. Meningiomas are tumors in the meninges.The meninges is a system of membranes that enclose the central nervous system and that has a primary function of protection. This means that the optic nerve of the eye also is covered with meninges. The meninges consists of three layers: the dura mater, the arachnoid mater, and the pia mater. Synaptic transmission of impulses from retinal cells follows the optic nerve, originating in the rear of the eyeball and proceeds back to the optic chiasm. The optic chiasm is an x-shaped junction in the brain, where half the fibers from each eye cross to the other side of the brain.
 As the figure shows, this means that some visual information from the right half of each retina (from the left visual field ) travels to the right visual cortex, and visual information from the left half of each retina (from the right visual field) travels to the left visual cortex. Put simply, information from the left half of our environment is processed in the right hemisphere of the brain, and vice versa. The optic nerve travels about 35-55 mm from the back of the eyeball to the optic chiasm. In the process, it passes through several structures. Medical scientists use these as landmarks to divide the optic nerve into sections along its pathway.
I have included this information in my description because problems can occur at different points along the optic nerve pathway and this may help you to understand where your tumor is occurring. Optic nerve sheath meningiomas (ONSM) are benign tumors of the optic nerve, 60-70% of which occur in middle-age females. As the tumor grows, it compresses the optic nerve and can cause loss of vision in the affected eye. ONSM are divided into primary and secondary categories. Primary ONSM emerge from cells of the arachnoid matter surrounding the orbital optic nerve or, less often, the intracanalicular optic nerve. Secondary ONSM originate in the intracranial meninges covering the brain and extend into the orbit of the eye. In these cases, the secondary ONSM is located close to the optic nerve, or in some instances can wrap around it, but does not involve the meninges of the optic nerve itself. Although these are far more common than primary ONSM, the term optic nerve sheath meningioma usually refers to primary ONSM.ONSM typically are slow-growing tumors and have no record of causing mortality. Nevertheless, the tumor potentially can grow into the brain and cause other types of neurological problems. In some instances, growth of the tumor is so slow that treatment to excise it or to impede its growth is not necessary. When treatment is indicated, it usually involves surgery, radiation therapy, or both in combination. Outcomes of surgery to remove ONSM depend on whether the meningioma is of the primary or secondary type and the degree to which the meningioma involves the optic nerve. Secondary ONSM that are close to, but that do not envelop, the optic nerve are easier to remove and have high success rates with little or no loss of vision. However, primary ONSM or secondary ONSM that envelop the optic nerve are much more challenging to excise and carry a higher risk for loss of vision in the affected eye. This is because the optic nerve is such a fragile structure. In either case, removal of an ONSM in the left eye will not affect vision in the right eye. However, in some cases meningiomas can recur. If this happens, the new tumor could potentially involve the right optic nerve. I have attempted to explain the anatomy of the optic nerves in order to give you an idea of how these structures can be both independent of each other and also work in conjunction. Each optic nerve initially is isolated by the orbits of the eye and the optical canal. It is only in the intracranial section that the optic nerves are in very close proximity. Ask your neurosurgeon if your meningioma is located in this area. It only is here that removal could potentially also affect sight in the right eye. Your neurosurgeon knows your condition the best and can answer your questions specifically. I am limited to explaining anatomy and discussing possibilities. I recommend that you have an open and frank discussion with your neurosurgeon about your meningioma, your concerns, and the prognosis for its successful removal without it affecting your vision. I wish you every success in your surgery. Carolina Valdivia, MD
REFERENCE:Wilkinson I and Lennox G. Essential Neurology, 4th Ed. Oxford, UK: Blackwell Publishing Ltd, 2005:48-53.
My goal in answering your questions is to provide you with information, clear up misconceptions, and to explain options so that you can have an informed conversation with your doctor. However, under no circumstances should my response to your question be considered a substitute for ongoing consultation and examination with your doctor. Since I have not examined you, I only can speak in terms of generalities, whereas your doctor has sufficient clinical details to evaluate your case specifically.
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Dealing with the prospect of brain surgery can be very stressful. From the information that you provided, one of your fears is a loss of vision – not just in your left eye where the tumor is located, but also in the right eye.
