Is MS a Diagnosis of Exclusion? Part 2
In my previous post, I explained the phrase “disease of exclusion,” using Parkinson’s disease as an example. In contrast, however, MS in not a disease of exclusion. According to the official criteria, known as the revised McDonald criteria, when a patient with suspected MS presents with a history and examination consistent with the illness, nothing else is required to make the diagnosis. Certainly, in the United States, every patient with a suspected diagnosis of MS would receive at least an MRI of their brain and spinal cord, and possibly a spinal tap as well, to look for markers of inflammation. In patients who have had a single attack of MS, the diagnosis can be made only if there is evidence of both old and new inflammation on a brain and spinal cord MRI. In many cases, it is not possible to determine for certain—based on a single visit with a patient—whether or not a patient has MS.
Certainly, like Parkinson’s disease, there are many mimics of MS, both clinically and on MRI, which must be ruled out. These include a variety of rheumatologic diseases (such as lupus or Sjögren’s syndrome), infections such as Lyme disease, psychiatric disturbances, vascular diseases, complicated migraines, or diseases of the nerves and muscle. You can read a good article on this subject at the Multiple Sclerosis Foundation.
Time will often tell if a person has MS, or some other diagnosis. However, more than once, I have had to retract a diagnosis of MS in a patient when new evidence came to light. Usually, these patients have ended up having very rare diseases such as adult polyglucosan body disease, CADASIL, or adult onset Alexander’s disease. I am certain that in every MS center today, there are some patients who are being treated for MS who in fact have some other illness. (I hope not too many!)
Different doctors have different practices in how far they will go to rule out these mimics. There is almost no end to the number of possible blood or imaging tests a doctor can order. And it is my experience that by ordering a huge swath of tests on every patient, something will eventually come back abnormal in almost everyone. A few abnormal lab tests often leave me more confused than when I started.
In my opinion, an exhaustive work-up should be reserved for those patients who have atypical presentations, which includes:
- Patients outside usual age range for MS (<10 or >60 yrs old).
- Patients outside of the usual geographic locations and racial backgrounds, such as a black immigrant from Africa.
- Patients with symptoms that start abruptly or progress swiftly and relentlessly with poor or no recovery from the attack. Significant cognitive deficits, language deficits, movement disorders, seizures, hearing loss can all occur with MS, but are uncommon as initial presentations of the illness.
- Patients with additional symptoms from outside the brain and spinal cord, such as fever, significant weight loss, disease of the eye (not optic nerves), significant joint pain, prominent rashes, or involvement of the peripheral nervous system.
- A prominent family history of neurologic disease.
- An MRI scan that is not typical for MS.
However, in a 30-year-old white female who grew up in the Northeast who presents with optic neuritis and 10 brain lesions consistent with MS, this is enough for me to make the diagnosis. In this way, MS is not a diagnosis of exclusion.
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