Neurology Teaching! Multiple Sclerosis Edition

Welcome to Part 7 of neurology teaching! I am a neurology resident who loves teaching medical students, fellow residents, and my patients-- and one of my favorite ways to teach is using images.

Let's talk about a relatively common spectrum of disease I encounter as a neurology resident: multiple sclerosis.

As usual I rely heavily on Radiopaedia.org, which is free to access and a wonderful resource for reviewing imaging.

Part 1: https://imgur.com/gallery/DTKTFU1 (intro)
Part 2: https://imgur.com/gallery/jzjpPoD (strokes)
Part 3: https://imgur.com/gallery/ANw2CDd (meningitis)
Part 4: https://imgur.com/gallery/Fsm9Buv (parasites)
Part 5: https://imgur.com/gallery/s8OvBL2 (intracranial pressure)
Part 6: https://imgur.com/gallery/Xksvovi (pupils)

Before we get to the cool images... Multiple sclerosis (MS) can look very different for different people.

In most people affected by MS, at least at the beginning, they will have recurrent, subacute onset of some focal neurologic symptoms (weakness, numbness, neuropathic pain, vision loss, dizziness, difficulty moving eyes, etc) which improves or resolves over their course of weeks to months, but over time often leads to accumulation of damage. This leads to weakness, numbness, pain, bladder dysfunction, cognitive difficulties, and difficulty walking. This is called relapsing/remitting.

In some people MS starts off as a gradual relentless progressive decline in neurologic functioning. More commonly the relapsing/remitting type evolves over time into the progressive type.

It is important to note that each individual's experience with MS is different.

At its core, Multiple Sclerosis is a chronic disorder characterized by inflammation and de-myelination of the central nervous system (brain, spinal cord). This leads to damage to neurons and their connecting parts, the axons.

Myelin can be thought of like a cable insulator-- it wraps around the axons which connect neurons and allows for the rapid and full transmission of signals. When myelin is damaged, ions leak out of the axon because the insulator is gone. This leads to dysfunction of the affected region of brain because signals are no longer reaching their destination properly. This demyelination can also lead to damage to the neurons themselves.

It is currently unknown exactly what triggers the inflammation/immune mechanisms responsible for MS.

It is not uncommon for multiple sclerosis to present clinically as Optic Neuritis-- or inflammation of the optic nerve, the nerve that is responsible for connecting your eyeball to your brain.

On this post-contrast MRI head of a person who came in with unilateral eye pain and decreased vision, you can see the left optic nerve (which is on the right side of the screen) is much brighter than right optic nerve. This is due to the active inflammation in that nerve.

Optic neuritis is clinically associated with dimming of vision in one eye, pain/discomfort with eye movements. On exam you may see less response of the the pupil to direct light and you can often see bulging of the optic nerve on fundoscopic exam, which is called papilledema.

MS lesions tend to cluster near the fluid-filled spaces in the brain-- such as the optic nerves which are surrounded by CSF, around the ventricles, the cerebral aqueduct, brainstem, and spinal cord.

Both of these pictures are non-contrasted MRI images from the same individual with MS. On the left you see a lot of MS plaques surrounding the lateral ventricles. On the right you see the sort of radial orientation of many of these plaques with respect to the ventricle. It looks a little like finger-like projections, and bears the eponym Dawson's fingers.

Here is an example of internuclear ophthalmoplegia (INO), which is not uncommonly seen when an MS plaque affects a white matter tract in the brainstem called the medial longitudinal fasciculus (MLF). This results in characteristic eye movement abnormality in that the eye on the affected side is unable to look towards the nose when both eyes are moving the same direction. So.. for this guy, when he looks to his LEFT, his RIGHT eye is unable to look to his nose. So his RIGHT MLF is affected.

The differential for acute INO is mostly stroke vs MS. That bright spot sort of in the middle of the picture is where the MLF is.

The spinal cord is also unfortunately a target for MS. When a new spinal cord lesion occurs that is typically called myelitis or transverse myelitis. This can be quite disabling.

On the left, you see the bright oval in the middle of the picture which contains a heterogenous dark and light gray circle? That is the cerebrospinal fluid space and the upper part of the spinal cord. The lighter part of that circle in the oval is a plaque in the spinal cord.

On the right you see a post-contrast image of the cervical spinal cord. Here you see multiple bright spots on an otherwise dark grey (normal) spinal cord. These bright spots are new MS plaques.

The intricacies of MS treatment are a bit beyond me at my level of training (so far!), but many, many options for treatment exist. Many, although not all, disease-modifying therapies are immunosuppressant medications that target different aspects of the immune system. These all come with their own unique risks, particularly during a pandemic.

For acute flares of MS we often will treat patients with a short course of high-dose steroids. In those that cannot have steroids we may do intravenous immune globulin (IVIG), although that requires a hospital admission.

There are many symptomatic therapies for MS, to help with the muscle spasms, improve walking, improve bladder control. There are a multitude of support groups. There are focused physical, occupation, and cognitive therapy programs. There is active and exciting research in the field.

Thanks for reading along and letting me share my love of neurology with all of you!