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How do spinal cord lesions show up?
There are several symptoms that state unequivocally that there is damage in the spinal cord. In the spinal cord the nerves that deal with the whole body run very close together down the cord. A single lesion can cut across an area that affects a large section of the body. In fact, one good sized lesion can essentially "cut off " the body below it as if the spine had been severed. This is the worst case scenario of the lesions of Transverse Myelitis. But, most lesions are not that large. The areas that deal with the motor functions (driving the muscles) on one side, all run together and the part of the cord that handles the sensory input is all on a different section from the motor.
As the cord runs down the back, the nerves branch off and leave the cord - becoming peripheral nerves. The nerves to the arms leave the cord in the cervical spine. The nerves that drive the muscles of the torso leave in the lower cervical spine and the from the thoracic. The nerves to the legs travel on through the cervical and upper thoracic to leave the spinal cord lower down. Many of them stay in the spinal canal below where the spinal cord ends as a loose-floating bundle of nerves called the "cauda equina" - the horse's tail. These nerves exit through the vertebrae in the lumbar spine.
What are Typical Signs of a Spinal Cord Lesion?
So some combination of problems on the neuro exam point to a specific "level" of damage in the spinal cord where there must be a lesion. Neurologist know that there is no lesion in the more spread out brain that could cause that combination of problems. An example is any kind of "Hug" sensation, especially around the chest or abdomen. Because the sensation usually goes pretty much all around it has to involve a problem with a large section of the spine.
-- The strongest sign is the presence of hyperreflexia. Because the reflex contraction is due to a spinal loop of nerve signals, this finding on neuro exam points to a symptomatic lesion in the spinal cord. If the arms are hyperreflexic, then the lesion must be in the cervical spine. The legs can point to a lesion anywhere in the spinal cord - but often in the thoracic spine.
Numbness, paresthesias or weakness from one level on down is indicative of a cord lesion, like the people that describe being "numb from the waist down." It doesn't have to be at the waist. Numbness to about the same height in both legs shows this, too.
--Specific areas of numbness and paresthesias also generally refer to a spinal lesion.
--Decreased vibration sense and position sense is common. If the pain and temperature sense is intact, this is another good clue that the problem is in the spine.
--Localized Spasticity (like of just one leg) is almost always due to a spinal cord problem.
Bladder and Bowel dysfunction is typically a result of spinal cord lesions.
--Urinary and Anal sphincter paralysis can be seen
--L'Hermitte's Sign is always due to a cervical spine lesion.
The MS Hug at any level or the banding sensation on a limb are caused by spinal cord lesions.
--During some research activity at the University of Miami Project to Cure Paralysis, I learned of investigations that revealed that for many patients, pain below the level of spinal cord involvement and sexual problems were the greatest complaints, even when there were motor difficulties in the limbs. Spinal cord induced pain can be excruciating. It often shoots down the spine (Lhermitte's Sign) or to the limb that is involved due to spinal cord damage.
--Erectile dysfunction is common in men with spinal cord MS. Orgasmic and fertility problems can strike both sexes with cord lesions. Spasticity is another major problem in patients with spinal cord problems of all types. This increase in muscle tone can also be painful and movement limiting.
These are just a few examples.
What do MS Spinal Cord Lesions Look Like?
They look the same as lesions in the brain. They are brighter on the T2 and FLAIR sequences of the MRI. They may be wide and extend across a large portion of the cord, but more commonly they are smaller and extend more up and down, sometimes as long as a couple of vertebral segments. They can be seen both from the sideways cuts (where you see the full length of the cord) called the "sagittal view." And they will also be visible from the crossways cuts (where you see the cord in cross-section as a semirounded object) called "transverse view" or axial view" or (in the brain) "coronal view."
I have been asked repeatedly to describe what my lesions looked like on the 1.5T and the 3T. On the 1.5T my neuro had to zoom way in and enlarge the areas. As you know, often when you super-enlarge an image it becomes coarse and grainy. Well, he pointed to about 4 little areas that looked even more coarse. The pixels were oviously more gray-light-gray-light in those little areas. And the areas that he was concerned about had no clear borders. They were just a little ratty. I'm not even sure that many other neurologists bother to do this "zoom in." But, my neuro said that, based on my exam, he knew he had to look for some spinal cord lesions. I am diffusely hyperreflexic, moreso on the right where there is also spasticity...
Then, when we had the 3T images he showed me the clear, small lesions, in exactly the same areas. These were brighter, these interiors were homogeneous, and their edges very clear and well-demarcated. In my case the difference was night and day.
Why are spinal cord lesions hard to image on the MRI?
There are built-in problems in viewing lesions with the spinal cord. The area that is being looked at is small and it is completely surrounded by CSF. Areas of the body that are right next to fluid are more difficult to image in the MRI. The water causes reflection of the signal and tends to "blur" out the image. That is why they developed different techniques, like the FLAIR, to make the lesions more visible. Even though the minum MRI stregth recommended for use in MS is a 1T, some neurologists feel that even the 1.5T does not show the smaller lesions adequately. My neuro is one of these. He won't even look at a spinal cord MRI on a 1.5T unless there is NO WAY the patient can get the 3T which he prefers.
Recently two forum members have reported on this problem. One is the study posted by Doublevision that Brigham and Womens Hospital in Boston is conducting a study comparing the 1.5T and the 3T for visualizing spinal cord lesions in MS. This indicates that there is enough of a concern about the difference to do a study to confirm or disprove it. Slightlybroken reports that her neurologist felt that her previous spinal cord 1.5T MRI was terrible and insists on repeating it on a 3T. These two things add more weight to the belief that the difference between 1.5T and 3T may be really significant.
Do You Have to Have an MRI of the Spine?
Do You Have to Have an MRI of the Spine?
Does the spine HAVE to be done in the very beginning of the workup? In my reading of the "Protocol" it does not. But, most of the reading I have done about this says "yes, it should be done." One way of thinking is that the doc already knows if there are signs on the neuro exam that indicate spinal cord lesions (eg. hyperreflexia) so you don't have to look. Another is that you should look to verify. If there are signs on the exam, I believe it would be ridiculous not to document them. How else would you know in the future if they increase or resolve?
More recently, I have been reading about "assymptomatic" spinal cord lesions that we should search for, that really help make the diagnosis (this makes a lot of sense to me). Having sorted it all out, I have come down on the side of recommending that the spinal cord SHOULD be imaged if MS is suspected. Yes, you can make the diagnosis on just the brain MRI, but the whole CNS needs to be looked at as a baseline for anyone whose symptoms highly suggest MS.
Something to take away from the information above is 1) Lesions in the spinal cord can be assymptomatic, and 2) they can be invisible. There can be indications that a spinal lesion definitely exists, but it may not be seen on MRI. I would say that this includes images on a 3T. The reason for this is that the 3T is the lowest strength that some are seen on. It only stands to reason that some lesions are still "invisible" at the 3T resolution.