Since my posts on multiple sclerosis are getting many hits from readers, I thought that I would in this post describe how a definitive diagnosis of MS is made.
First and foremost, a definitive diagnosis of MS can be made just clinically without any other imaging studies like MRI or the need for invasive tests like lumbar puncture (spinal tap). How you may ask?
Well if by history you have had two attacks suggestive of MS which are disseminated in time and space, then a definitive diagnosis of MS can be made. Let me explain this in simple language. Lets assume you go to your doctor because you have been having numbness in your right arm. Your doctor examines you and finds that apart from sensory loss in the right arm, you have other examination findings such as you have ataxia (your gait is off and unsteady), you have incoordination and tremor in your right arm, your eyes do not move well and you have what we call internuclear opthalmoplegia. Hmm sorry for all that medical jargon, let me try to make it more simple. What I am trying to say that your examination findings are suggestive of not one but multiple sites of pathology in your brain.
Numbness right arm localizes to the sensory cortex on the left side of your brain.
Ataxia might be due to midline cerebellar problem
Right arm tremor localizes to the right cerebellum (cerebellar pathways are double crossed in the brain)
The eye findings and internuclear opthalmoplegia localizes to the midbrain.
So you have signs that whatever your disease is it is disseminated in space (SPACE AS IN DISSEMINATED IN DIFFERENT PARTS OF THE BRAIN). Your findings cannot be explained by one single lesion rather by multiple small lesions.
So you have met the first criteria to make a definitive diagnosis of MS-dissemination in space. (OF COURSE DISSEMINATION IN SPACE SHALL ALSO BE CLEARLY SHOWN IF YOU DO A MRI SCAN)
Now how do we prove you have dissemination in time? Well that is done by history. Lets assume your doctor now asks you ” Miss Smith have you ever had a problem with your eye before? Did you ever lose vision in one eye?”
Miss Smith: “ Now that you ask doctor Sethi, yes. When I was 18, I had an episode where I had pain in my left eye and lost vision rather abruptly. By the time I saw my doctor, it had started to improve by itself and I did not think much of it.”
Viola!!! here the history is telling you that Miss Smith has in fact had dissemination in time. Likely she had an attack of optic neuritis when she was 18 which had resolved by itself.
So as a doctor examining Miss Smith, I now know that her disease is disseminated in time (she has had attacks in the past) and also in space (from my examination findings I know that she likely has multiple lesions in the brain, only then I can explain all her findings).
I DO NOT NEED ANY ADDITIONAL TESTS TO MAKE A DIAGNOSIS OF MS. SHE HAS HAD 2 ATTACKS DISSEMINATED IN TIME AND SPACE.
Of course as part of her management I would do a MRI study of the brain and some doctors might still do a lumbar puncture.
Additional tests like MRI brain, spinal tap and evoked potentials (visual and somatosensory evoked potential) are needed when either of the above 2 is missing. Either Miss Smith has had just one clinical attack or her examination finding are suggestive of one lesion.
Nitin Sethi, MD