Multiple sclerosis (MS) is a chronic inflammatory disease that affects the central nervous system. It damages the myelin sheath that protects nerve fibers in the brain, spinal cord and optic nerves. This damage slows down or blocks messages between the brain and body, leading to symptoms such as numbness, weakness, fatigue, vision problems and problems with coordination and balance.
MS is typically diagnosed based on clinical presentation, detection of lesions on MRI and presence of oligoclonal bands in the cerebrospinal fluid. However, there are some conditions that can mimic MS lesions on MRI scans. Being aware of MS mimics is important to avoid misdiagnosis.
What are the typical MRI findings in MS?
In MS, MRI commonly shows multiple focal areas of increased T2 signal intensity. These bright, hyperintense lesions on T2-weighted images represent areas of inflammation, demyelination and gliosis (scarring). The lesions are typically ovoid, range from a few millimeters to over a centimeter, and occur in the periventricular white matter, corpus callosum, brainstem, cerebellum or spinal cord.
Lesions can enhance after injection of intravenous gadolinium contrast, indicating breakdown of the blood-brain barrier and active inflammation. As the lesions resolve, enhancement fades but T2 hyperintensities may persist as chronic scars.
Over time, atrophy (tissue loss) of the brain and spinal cord can also be seen on MRI due to neurodegeneration.
What conditions can mimic MS on brain MRI?
Some of the main mimics of MS on brain MRI include:
Migraine
Migraine headaches are common and can have white matter lesions similar to MS on MRI. However, migraine lesions are typically located in the subcortical, deep white matter rather than periventricular regions. They also do not enhance with contrast.
Small vessel ischemic disease
Also known as leukoaraiosis, small vessel ischemic disease causes small, punctate white matter lesions due to chronic ischemia. Lesions are usually bilateral and symmetrical in distribution.
Vasculitis
Inflammatory disorders like systemic lupus erythematosus, Sjogren’s syndrome and Behcet’s disease can have MRI findings mimicking MS. Lesions tend to be located in both gray and white matter and show enhancement with contrast.
Sarcoidosis
This inflammatory condition can form granulomas in the central nervous system, appearing as enhancing masses on MRI. However, sarcoidosis also affects other organs like the lungs and lymph nodes.
CADASIL
Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) causes subcortical white matter lesions from damage to small blood vessels. Unlike MS, lesions spare the corpus callosum and cortex.
PML
Progressive multifocal leukoencephalopathy (PML) is caused by the JC virus in immunocompromised patients. Lesions have a very characteristic appearance on MRI and are usually distinguishable from MS.
NMOSD
Neuromyelitis optica spectrum disorder (NMOSD) can have brain lesions similar to MS but often spares the corpus callosum. There is also more frequent involvement of the hypothalamus and aqueduct.
What mimics spinal cord lesions of MS?
In the spinal cord, longitudinal extensive transverse myelitis (LETM) lesions spanning 3 or more vertebral segments are typical of MS. Mimics include:
Nutritional deficiencies
Vitamin B12 and copper deficiency can cause myelopathy characterized by subtle increased T2 signal but not gadolinium enhancement.
Infections
Viral infections like herpes viruses, bacterial abscess and Lyme disease can mimic inflammatory MS lesions in the spinal cord.
NMOSD
As mentioned above, NMOSD commonly affects the spinal cord with lesions that can resemble MS.
compressive myelopathy
Spinal cord compression from herniated discs, stenosis or trauma can produce T2 hyperintensities and mimic MS lesions.
Conclusion
MS has some characteristic MRI findings that help diagnose the condition. However, there are a number of mimics including migraine, small vessel disease, vasculitis, infections and inflammatory disorders that can produce similar-appearing lesions on MRI.
Being aware of potential MS mimics is important to avoid misdiagnosis. Careful correlation with clinical history and other tests like CSF analysis helps distinguish MS from mimicking conditions.
| MS Mimic | Typical MRI Findings |
|---|---|
| Migraine | Lesions in subcortical white matter without enhancement or mass effect |
| Small vessel disease | Bilateral symmetrical punctate white matter lesions |
| Vasculitis | Lesions in both gray and white matter with enhancement |
| Sarcoidosis | Enhancing granulomas throughout CNS |
| CADASIL | Subcortical lesions sparing corpus callosum and cortex |
| PML | Characteristic asymmetric lesions along gray-white junction |
| NMOSD | Long cord lesions, hypothalamic and aqueductal lesions |
| Nutritional deficiencies | Subtle T2 hyperintensities without enhancement |
| Infections | Enhancing cord lesions |
| Compressive myelopathy | Cord T2 lesions corresponding to level of compression |