Multiple sclerosis (MS) is a tough illness to diagnose. Its symptoms are
similar to several other illnesses, and the National Multiple Sclerosis
Society says MS is incorrectly diagnosed 5% to 18% of the time. It can also
take a long time to reach a firm MS diagnosis and that can mean months, or
even years, of delay in starting an MS treatment.
Tools to assist a neurologist in making an MS diagnosis include magnetic
resonance imaging (MRI), lumbar punctures, the physical exam, and the
patient’s history. But it wasn’t until 2001 that diagnostic criteria were
created; the McDonald Criteria, named for Dr. Ian McDonald who led the
international panel of experts that wrote them. The latest revision of the McDonald Criteria was written in 2024 and was published in the September 17, 2025 issue of the journal Lancet
Neurology.
The revised criteria expand on the 2017 version and allow for a
quicker diagnosis, using fewer benchmarks. “The revisions offer a clearer
and faster path to diagnosis, giving [patients] the chance to begin treatment
sooner and move forward with greater certainty,” says Dr Lydia Makaroff,
Chief Executive of the MS International Federation.
What’s changed in the McDonald Criteria?
The 2017 criteria required evidence that damage to the central nervous
system (CNS) was observed on different dates. That dissemination in time
requirement (DIT) has been removed. The 2017 criteria also required that
damage be observed in two of four different locations of the CNS, known as
dissemination in space (DIS):
1. The spinal cord
2. The periventricular
3. The cortex
4. The brain stem and cerebellum
The 2024 revision adds the optic nerve as a fifth location. That’s important
because optic neuritis is frequently one of the first MS symptoms that occur
pre-diagnosis. Also, the central vein sign, paramagnetic rim lesions, and
kappa free-light chain concentrations in spinal fluid can now be used to
support an MS diagnosis.
The criteria also contain new considerations for diagnosing children and
people over 50, because it can be more difficult to diagnose MS in these age
groups. The criteria strongly recommend that people over 50 who have
headaches or vascular disease, or risk factors such as smoking, high blood
pressure, high cholesterol or diabetes, undergo additional testing before an
MS diagnosis is made. Additional testing is also recommended for children
under 12 and adolescents.
Faster MS recognition with fewer misdiagnoses
All in all, the 2024 McDonald Criteria revision makes the MS diagnostic process more streamlined than it’s ever been. “By integrating noveliomarkers and rigorous consensus methodology,” says ECTRIMS President Professor Bruno Stankoff, “the updated criteria strengthen diagnostic
accuracy and become more globally applicable. This balance between
sensitivity and specificity is essential — and now ensures that people with
MS can be identified earlier, equally across all ages, and that misdiagnosis
is reduced.”
According to Julie Fiol, the MS Society’s associate vice president of clinical
innovation and strategy, the goal “is not to make patients get all of the tests,
but to use the ones that make sense.” In Momentum magazine Fiol says the
new criteria are “intended to provide more options to do what makes sense
for the patient in front of you and to get to an MS diagnosis more quickly.”
The position paper in The Lancet Neurology that details the 2024 McDonald
Criteria concludes “Diagnosing multiple sclerosis requires a balance
between facilitating early recognition and avoiding misdiagnosis, without
unnecessary complexity and considering the diversity of clinical settings
worldwide.”
It seems to me this recent revision is one step closer to meeting that goal.
(This post first appeared on the Rare Disease Advisor website)
(Image by Dmitriy Kievskiy from Pixabay)