Understanding NMOSD Lesions

Neuromyelitis optica spectrum disorder (NMOSD) affects the central nervous system. The brain, spinal cord, and the optic nerve are some of the parts of the central nervous system. Since NMOSD is an autoimmune disease, it causes the body’s immune system to attack healthy cells. In NMOSD, healthy brain cells (neurons) are targeted by the immune system. This damages the central nervous system and causes lesions.¹

What are lesions?

Lesions are damaged parts of the brain or central nervous system that are visible. Lesions can disrupt the signals passing to and from different parts of the brain. As a result, lesions can greatly affect the normal functioning of the brain.^1,2

Different types of damage can cause lesions. In people with NMOSD, the immune system is responsible for the lesions. NMOSD causes the immune system to attack astrocytes, which are cells that make up the central nervous system. The protective layer around these cells becomes damaged, resulting in NMOSD lesions.^1,2

How are lesions seen?

Different imaging techniques can be used to see lesions. A magnetic resonance imaging (MRI) scan uses a large magnet to see the organs inside the body. The water in different body organs responds differently to the large magnetic field within the MRI machine. These differences in how the water behaves can be analyzed to create clear images of the organs.³

To increase the quality of the images, an MRI with contrast can also be used. The contrast solution contains a metal called gadolinium. This contrast solution is injected right before the MRI scan. The contrast as well as the MRI are safe to use. Depending on the situation, doctors may use MRI scans to diagnose or follow the progress of a disease.³

What do lesions look like?

The MRI scans can be done in different ways to get a better look at:⁴

• New NMOSD lesions
• Old NMOSD lesions
• Old damage to the central nervous system

Without using any contrast solution, MRI scans can be done in T1 or T2 sequence.⁴

T1 MRI scans show the general shape and different parts of the central nervous system. Any areas which have shrunk will appear as dark spots. These are areas which were damaged earlier.⁴

T2 MRI scans show lesions in the brain, spinal cord, and other parts of the central nervous system. The damaged protective layer of neurons or lesions appear as bright white spots in the MRI scan. This type of MRI scan shows old and new lesions.^4,5

MRI scans with contrast are used to see only new lesions. These scans can be used to find out how a disease is progressing and whether treatments are working.⁴

How are lesions used in diagnosis?

Using MRI scans to see NMOSD lesions is an important part of diagnosis. Other diseases, such as multiple sclerosis (MS), can also cause lesions in the central nervous system. A doctor can use the MRI scans along with other tests to tell apart MS and NMOSD. Usually, long lesions on the spinal cord are due to NMOSD. Lesions in the brain can also occur as NMOSD progresses.^1,5

The part of the brain or central nervous system that has lesions can determine the symptoms that might be present. Lesions on the brain stem, which connects the brain to the spinal cord, can cause:¹

• Nausea
• Vomiting
• Hiccups

Lesions on a part of the brain called the hypothalamus can cause:¹

• Weight gain
• Sleepiness during the day
• Other problems with regulating body functions

Lesions or damage to the optic nerve, which sends signals from the eyes to the brain, can cause:¹

• Loss of sight
• Pain during eye movement

Lesions in the central nervous system, particularly the spinal cord, are caused by NMOSD. These lesions play an important role in diagnosing NMOSD and differentiating it from other diseases like MS. MRI scans can be used to look at new and old lesions to see how well treatments are working.^1,5