Neurologic Disorders that Can be Mistaken for Glaucoma
Chat Highlights
July 11, 2007

On Wednesday, July 11, 2007, Dr. Mark Moster, a neuroophthalmologist at Wills, and the glaucoma chat group discussed "Neurologic Disorders that Can be Mistaken for Glaucoma."

Moderator:  Welcome back, Dr. Moster. Will you tell us a little about your background?

Dr. Mark Moster:  My training was first as a neurologist at the University of Pittsburgh, then a fellowship in neuro-ophthalmology at Wills Eye Hospital.  I practice neuro-ophthalmology, which deals with eye problems due to neurologic disease.

Moderator:  Thank you. Our topic tonight concerns neurologic disorders that can be mistaken for glaucoma.  Dr. Moster, would you like to start with a brief opening statement?

Dr. Mark Moster:  Glaucoma causes visual loss by damage to the optic nerve.  Many other diseases also can affect the optic nerve, so occasionally what looks like glaucoma may be another disorder.

P:  What are some of the neurological disorders that can be mistaken for glaucoma?

Dr. Mark Moster:  The most important one would be a brain tumor compressing the optic nerves, or further back in the visual pathway.  Others include inflammations, infections, degenerative diseases, hereditary conditions, and strokes.

P:  How are those other disorders distinguished from glaucoma?

Dr. Mark Moster:  There are many aspects of the symptoms and examinations that help distinguish them.

P:  What diagnostic tools are used to find out if the disorder is neurologic rather than glaucomatous?

Dr. Mark Moster:  The main diagnostic tools are the evaluation of the optic nerve by directly looking at it, and the character of the visual field defect, as well as the other parts of the examination in the office.  Also, there are tests that can be ordered, such as MRI (magnetic resonance imaging) and blood work.

P:  What would the radiologist look for in the MRI of a patient as an explanation of suspected normal-tension glaucoma?

Dr. Mark Moster:  The most important parts of the visual pathway to look at would be the optic nerve and the optic chiasm.  The MRI will usually focus on the orbit and the brain.  The physician will usually ask the radiologist to look for a mass lesion compressing the nerve or, occasionally, a taking up of contrast by the nerve, which would suggest inflammation.

P:  From the patient's point of view, is there anything that distinguishes glaucoma from those other disorders?

Dr. Mark Moster:  Let's first talk about how the symptoms came on.  If it is open-angle glaucoma, then it is likely slowly progressive.  Some neurologic disorders are sudden.  Also, glaucoma is most often without headache, whereas brain tumors most often cause chronic headache.

Moderator:  Are there any other symptoms?

Dr. Mark Moster:  Glaucoma affects peripheral vision first.  Many neurologic disorders affect central vision first.  Other symptoms can include double vision or symptoms of change in memory, numbness, weakness, etc.

P:  Can a neurologic disorder cause glaucoma?

Dr. Mark Moster:  Some neurologic disorders can raise intraocular pressure and look like glaucoma.  Two such disorders come to mine.  One is a thyroid condition that makes the muscles in the back of the eye large and inflamed.  The other is a dural carotid-cavernous fistula that causes back pressure into the eye.

P:  Many patients are confused about the meaning of peripheral vision.  They think it means vision far off to the side.  Will you please define it?

Dr. Mark Moster:  Well, it does include vision to the sides, as well as the top or bottom of the entire area of vision.  It is anywhere that is not directly straight ahead.

P:  Do the central vision defects of neurological disorders cross the visual midline?  Are they horizontal or vertical defects?  Are they nasal or temporal?  Last, would you consider a superior arcuate scotoma that skims the midline glaucomatous or something else?

Dr. Mark Moster:  The answer is complex.  It depends on the condition.  If it is a hereditary condition, it will likely cross the midline.  If it is a pituitary tumor pressing on the optic chiasm (where visual information crosses to the other side of the brain), it will respect the vertical meridian and stay on the temporal side in either eye.

P:  Would you please explain why, if a defect is hereditary, it will probably cross the midline?  Conversely, if a defect crosses the midline, is that significant?

Dr. Mark Moster:  It turns out that many of the hereditary conditions, for example, Dominant Optic Neuropathy and Leber's Hereditary Optic Neuropathy selectively involve fibers in the nerve dealing with central vision.  The way those fibers run doesn't create a border on the midline. If the defect crosses the midline, it is not likely behind the optic nerve, because once the fibers get further into the brain, they line up with a border at the midline.

P:  When do glaucoma specialists or primary eye care doctors refer a patient to a neuro-ophthalmologist?

Dr. Mark Moster:  If a patient has a typical history and exam for glaucoma, there is no need to refer.  However, when things don't follow the typical course, then referral makes sense.

P:  If no neurological disease is found, the intraocular pressure is normal, but the patient has visual field loss and progression, is that normal-tension glaucoma?

Dr. Mark Moster:  Assuming the progression in terms of optic nerve and visual field are following a course seen in glaucoma, then that would be correct.

P:  Why would a stroke be considered a neurological problem?  Isn't the kind of stroke that affects the optic nerve a vascular problem?  Isn’t it a mechanical blockage or spasm of an artery or arteries providing blood supply to the optic nerve?

Dr. Mark Moster:  It is true that it might be a blockage to the optic nerve.  Remember that the optic nerve is part of the brain, so many doctors would still consider that a stroke.  Also, a stroke further back, at the level of the optic tract, can rarely mimic glaucoma, in the way the optic nerve appears.

P:  What is optic neuropathy?  Can it result in patterns of visual field damage similar to glaucoma?

Dr. Mark Moster:  Optic neuropathy is a term that means a dysfunction of the optic nerve.  The most common acquired optic neuropathy in adults is glaucoma.  Other causes of optic neuropathy include inflammation, optic neuritis, acute loss of blood flow, anterior ischemic optic neuropathy, a mass causing compressive optic neuropathy, etc.  All of those can produce visual field defects that may be similar to those of glaucoma.

P:  Could mechanical stress on a nerve resulting from a 35 m.p.h. crash involving a sharp, sudden, circular wrenching of the head and abrupt stop cause damage that would show up in a visual field test?

Dr. Mark Moster:  A traumatic optic neuropathy can occur when there is a direct blow to the frontal region or forehead.

P:  My 54-year-old husband has glaucoma.  He underwent trabeculectomies in 2003and 2004, but has completely lost his sight.  Eleven months ago he had a stroke.  He has had MRIs and a nuclear scan.  Doctors here in Australia have been unable to find anything wrong. When they examine his optic nerve, they say he should have some sight.  For years my husband had terrible headaches, but his glaucoma was diagnosed many years before his headaches occurred.  Neurologists and glaucoma specialists here in Australia are all baffled. Any suggestions?

Dr. Mark Moster:  Do you know if the stroke affected the visual areas further back in the brain?

P:  I don't think so.  He has complete memory loss (long term) since the stroke.

Dr. Mark Moster:  There may be many other causes of visual loss besides the optic nerve.  With memory loss, sometimes there is loss of some of the nerve fibers in the brain that process the visual input.  There are also other conditions that can be checked for in the blood; for example, a deficiency of vitamin B12.  Sometimes a person can lose vision from loss of blood flow to the retina.  Afterwards, the optic nerve and retina do not appear abnormal.

P:  My husband has had Doppler imaging, blood tests, etc.  They didn't show anything wrong. We spent four-and-a-half years in a third-world country.  Could he have picked up some sort of virus or infection that could be the cause of the vision loss and the stroke?

Dr. Mark Moster:  It's very hard to know without knowing much more detail or seeing what the eye exam looks like.  Theoretically, an infection can cause loss of vision, and could be found with a spinal-tap examination.  Most neuro-ophthalmologists would be able to think of all the causes that are not visible in the eye itself.

P:  How do you measure the blood flow to the optic nerve?

Dr. Mark Moster:  I think that is a question for research or clinical situations.  Clinically, we can look at the carotid and ophthalmic arteries with Doppler ultrasound, CT angiogram, or MRI.  We can also look at some of the smaller circulation with a fluorescein angiogram.

P:  I understand that an adenoma (a benign tumor of the pituitary gland) can compress the optic nerve. How common is that, and how easy is that to diagnose?

Dr. Mark Moster:  It turns out that many people have tiny adenomas and never even know it. When an adenoma becomes larger, it can affect vision.  For women, some of the earlier symptoms include loss of menses and galactorrhea (fluid discharge from the breasts); for men, impotence; for everybody, feeling cold and headaches.  The visual loss tends to be off to the temporal side in both eyes, different from glaucomatous loss, which tends to be on the nasal side.

P:  Would you please discuss the relationship between migraines and glaucoma?  Could they cause glaucoma?

Dr. Mark Moster:  Studies have shown that a higher number of patients with glaucoma have migraines than the population of people without glaucoma.  So, there may be some relationship.  A migraine, however, does not cause glaucoma.

P:  You mentioned infection as a possible cause of optic nerve damage.  Would that include infection of the sphenoid sinuses?  How is that diagnosed?  Are any other infections pertinent?

Dr. Mark Moster:  Many infections can affect the optic nerve.  What you are describing is a sphenoid sinus infection that spreads into the orbit or brain and compresses the optic nerve.  Other infections can directly affect the optic nerve.  These include syphilis, Lyme disease, cat-scratch fever, West Nile virus, and more.  They are not, however, common causes of optic neuropathy.

P:  Can herpes zoster (shingles) damage the optic nerve?

Dr. Mark Moster:  Yes, it is an uncommon complication seen soon after shingles.

P:  I have been under the impression that migraine may be indicative of spasms of blood vessels and that these spasms might temporarily restrict blood flow to the optic nerve, thus causing damage.  Can you please comment?

Dr. Mark Moster:  Migraine is a complicated disorder, which does include decrease in blood flow.  Experts are debating whether there is a true migraine that might occur in the eye, as opposed to a typical migraine in the brain.  You are correct, however, that some experts believe that migraine may decrease blood flow to the optic nerve.

P:  You mentioned using a fluorescein angiogram to study smaller circulation.  Would that be used to look at circulation in the small arteries between the optic nerve head and the chiasm?

Dr. Mark Moster:  The visualized area in the fluorescein angiogram doesn't go that far back.  Most medical centers don't have good ways of looking at that circulation.  A few major eye centers, however, have more sophisticated orbital blood flow techniques that are beginning to see more in that area.

P:  I have amblyopia.  Vision in that eye looks to the left when I am looking straight ahead.  I also have a blind spot in the center of my vision.  Would a visit to a neuro-ophthalmologist help in understanding why I see the way I do?  Even though I was born this way, sometimes seeing in two different directions at the same time can be exhausting.

Dr. Mark Moster:  How can I say not to see a neuro-ophthalmologist?  However, for you I really do think it is a good idea, in case the neuro-ophthalmologist finds something that can help your symptoms.

P:  I am one of those persons without a clear diagnosis.  My vision loss was sudden and is monocular, pressures are normal, and progression has been slow. I was given an MRI without contrast.  What does "with contrast" and "without contrast" mean in relation to optic nerve damage?

Dr. Mark Moster:  Some things can be seen with contrast and not seen without contrast.  An example is a meningioma, a benign tumor that might be encircling the optic nerve and would only be seen with contrast.

P:  Is the retina considered part of the optic nerve?

Dr. Mark Moster:  No.  However, the nerve cells that run through the optic nerve into the brain begin in the retina and are called retinal ganglion cells.  Those are the nerves damaged in glaucoma.

P:  There's one thing I've seldom seen discussed in relation to optic nerve damage: blockage or constriction of episcleral veins.  Can that cause vision damage?  If so, what are the signs of that condition?

Dr. Mark Moster:  There are occasional conditions in the brain, specifically a fistula, that can increase the pressure by back flow into the episcleral veins.  The eyes become red, with the episcleral veins dilated.  There are usually other signs of this condition, which can be found on MRI or orbital color Doppler studies.

P:  Should a patient with sudden and unexplained vision loss have an MRI with and without contrast?

Dr. Mark Moster:  When you say unexplained, I am assuming the retina and optic nerve are normal on examination.  If so, the answer most often is yes.

Moderator:  Thank you for joining us again, Dr. Moster.

Dr. Mark Moster:  Thank you all. Good night.

On July 18, Dr. Pro discussed "Measuring Intraocular Pressure" in the Chat room. Click here for highlights of that meeting.

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