What is false regarding McDonald criteria for diagnosis of MS?
## Core Concept
The McDonald criteria are a set of diagnostic criteria used for the diagnosis of multiple sclerosis (MS). They were developed to facilitate the diagnosis of MS based on a combination of clinical and radiological findings. The criteria include the dissemination of lesions in space and time.
## Why the Correct Answer is Right
The McDonald criteria require evidence of dissemination in space (DIS) and dissemination in time (DIT) for the diagnosis of MS. DIS can be shown by the presence of lesions in at least two of the four typical locations (periventricular, juxtacortical, infratentorial, or spinal cord) on MRI. DIT can be demonstrated by the simultaneous presence of asymptomatic enhancing and non-enhancing lesions at any time or by a new T2 lesion on follow-up MRI compared to a reference scan done at least 30 days after the initial scan.
## Why Each Wrong Option is Incorrect
- **Option A:** This option might suggest that the McDonald criteria do not require dissemination in space and time, which is incorrect as both are essential.
- **Option B:** This could imply that a single MRI is sufficient for diagnosis, which contradicts the need for evidence of lesions at different times.
- **Option C:** This might state that CSF analysis is not needed, which could be misleading because while not required for the McDonald criteria, CSF analysis can support the diagnosis.
- **Option D:** This option might incorrectly suggest that clinical relapses are necessary for the diagnosis, which is not entirely accurate since the McDonald criteria can be fulfilled based on MRI findings alone.
## Clinical Pearl / High-Yield Fact
A key point to remember is that the McDonald criteria have evolved over time to facilitate earlier diagnosis and treatment of MS. They emphasize the role of MRI in demonstrating dissemination in space and time, making it possible to diagnose MS in patients with a single clinical event (monosymptomatic presentation) if the MRI criteria are met.
**Correct Answer:** D. Clinical relapses are necessary for the diagnosis.