One of readers emailed me this question. My response to it follows.
on October 17, 2008 said: 
Hello Dr,
I am a 28 asian/indian female. I was brought up in India for large part of my file.
I had symptoms of blind spots in my vision sometime back. The condition persisted for 2 days before I scheduled an appointment with my opthamalogist. He suspected that I have optic nueritis and advised me for a MRI. Now the lab technician says that I have a few lesions in my brain and asked me to consult a nuerologist. I have a pending appointment. My eye became completely normal in about 10 days from onset. By googling I found that it might be a case of MS.
Is it always the case optic nueritis + MRI lesions = MS? Is there anything else I should be looking at? I’ve had problems of vitamin deficiencies in the past. I have had some tongue rashes, gastro problems. Nothing serious but minor issues though.
Thanks,
Riddler
Dear Riddler,
patients who have optic neuritis usually do not complain of blind spots, rather they have acute/sudden loss of vision (usually in one eye, though in a condition called neuromyelitis optica they may have optic neuritis in both eyes). This condition may be painful (complaint of pain in the eye). Not all patients who have optic neuritis have multiple sclerosis. There can be many other causes of optic neuritis namely other infectious and inflammatory conditions. Patients who present with optic neuritis and are in the right age group (eg a woman in her 20s or 30s presenting with optic neuritis), need to be worked up for multiple sclerosis. Usually we order a MRI brain, to see if there is evidence of multiple sclerosis (read my posts on white matter lesions in the MRI brain of MS patients at http://braindiseases.info). As I have stated repeatedly, not all white matter lesions on the MRI represent multiple sclerosis.
In answer to your question, yes some vitamin deficiencies can cause blind spots and lesions in the brain. My advise to you would be to see a neurologist, the diagnosis of optic neuritis can be confirmed with the aid of certain tests like visual evoked potentials (VEP). Then the MRI can be interpreted in the right context.
Personal Regards,
Nitin Sethi, MD
Braindisease's Weblog 
Thanks for the reply. I took B12 test also and was diagnosed with low B12 level 130 PG/ML. I am meeting the neurologist for VEP and further testing. What should I be keeping in mind, and what questions should I be asking him?
I read B12 deficiency can also result in brain lesions and optic neuritis.
Thanks,
Dear Riddler,
you are very welcome. Low vitamin B12 levels may cause optic atrophy (slight difference from optic neuritis). Your B12 levels are quite low and it needs investigation. There can be many causes of vitamin B12 deficiency. Vitamin B12 is usually found in meat and meat products and hence deficiency usually occurs in people who are strict/ pure vegetarians. Other causes include pernicious anemia (where even though your diet may have adequate vitamin B12, your body cannot absorb it because of lack of intrinsic factor. This is a factor secreted by the acid producing cells of the stomach which aids in absorption of vitamin B12), people who have Crohn’s disease and other similar inflammatory bowel diseases, infestation with worms etc may also have inadequate vitamin B12 absorption.
Your doctor may order a couple of other blood tests to determine the extent of vitamin B12 deficiency. These include methyl malonyl CoA and homocysteine levels.
The VEP shall help to confirm demyelination of optic nerve (optic neuritis).
Like I stated earlier, it is only after taking a good history of your clincial presentation, consideration of the results of your blood tests that the MRI findings can be interpreted in the proper context.
Your doctor and neurologist shall be the best people to help guide you through this. You can read more about how diagnose of multiple sclerosis is made on my website http://braindiseases.info.
Personal Regards,
Nitin Sethi, MD
Hello,
This is what my MRI report says.
Standard sequences including axial FLAIR, T2, and diffusion weighted
images with ADC maps, plus coronal FLAIR sequences and sagittal T1
weighted images
Post contrast scans in 2 planes are obtained.
Because of potential concern for multiple sclerosis we also included
thin section sagittal FLAIR sequences
12 cc of gadolinium were given for the IV contrast
the patient has bilateral white matter lesions most concentrated in
the periventricular regions are also scattered in the subcortical
white matter. The pattern of abnormalities including linear and
ovoid lesions perpendicular to the adjacent lateral ventricles is
highly suggestive of demyelinating disease, in the proper clinical
context.
The largest lesion lies adjacent to the anterior horn of the right
lateral ventricle and shows contrast enhancement and is most
consistent with an active plaque. It measures about 2 cm in
diameter. (A thin rim of low signal at the margins of the lesion
with more peripheral inflammatory changes are noted on T2 weighted
axial image and is occasionally seen with an active demyelinating
plaque)
There is a smaller enhancing lesion in the posterior inferior right
parietal region which also shows contrast enhancement. A tiny focus
in the left periventricular region also shows enhancement. Possibly
one at the posterior margin of the right lateral ventricle.
Thin section STIR sequences in the orbits show patchy distribution of
peripheral bright signal in the optic nerves bilaterally suggestive
of optic neuritis. This is less likely to represent normal fluid in
the optic sheath.
The largest plaque is measuring 2 cm in diameter.
I am really scared now :-(.
Dear Riddler,
I apologize for the delay in getting back to you. While I shall not comment on your case specifically as I have not examined you, the MRI report (remember I have not seen your scan myself) is compatible with a diagnosis of multiple sclerosis in THE RIGHT CONTEXT.
Follow up with your neurologist. He/ she shall be the best to guide you further.
Keep in touch.
Personal Regards,
Nitin Sethi, MD