The Diagnosis of Multiple Sclerosis
In medical school, every doctor is taught that the key to a correct diagnosis is obtaining a comprehensive history and performing a thorough physical examination. Though radiographic and laboratory tests are invaluable aids, the diagnosis of multiple sclerosis (MS) is no different. The key to making a diagnosis of MS is to identify two separate episodes of neurological dysfunction that have occurred at different points in time (at least 30 days apart) in different parts of the nervous system.
The Initial Symptoms of MS
Since MS affects the entire brain and spinal cord, the initial symptom of MS can include almost any symptom in neurology. Weakness and sensory disturbances are the two most common initial symptoms in MS, simply because these pathways span the length of the nervous system from the outermost part of the brain to the end of the spinal cord. Any MS lesion is therefore very likely to affect one or both of these pathways. However, it is often easy for a patient to ignore a little numbness or weakness, especially as these symptoms may go away on their own even without any treatment. It is also common for patients and doctors alike to misattribute the initial symptoms of MS to something more benign such as a “pinched nerve” or muscle strain. Often times, a patient will have had the symptoms of MS for many years before they seek medical attention and the correct diagnosis is made. Other symptoms, such as visual loss, double vision, imbalance, and vertigo are less likely to be ignored or misdiagnosed.
How Doctors Diagnose MS
In patients who provide a history of two separate neurological attacks with evidence on physical exam of two or more lesions, no further evidence is required to make the diagnosis. However many patients will come to the doctor after having had a single episode of neurological dysfunction. Once a patient presents with a neurological symptom suggestive of MS, most doctors will order an MRI (magnetic resonance image) of the brain and spinal cord. If this reveals typical lesions of MS, no further tests are necessary. However, if the MRI is not 100 percent clear, a spinal tap might be necessary to look for markers of inflammation in the central nervous system. Only if certain abnormalities (which I will discuss in more detail in future posts) are present on these tests can the diagnosis of MS be made. Until then, patients with only one event are deemed to have clinically isolated syndrome (CIS), and only time will tell if a patient with CIS will go on to develop MS.
It is important to remember that the criteria for diagnosing MS did not come handed to doctors on stone tablets. Rather, experts in the field meet periodically and decide on these criteria. The distinction between MS and CIS is a therefore somewhat artificial. And, as the evidence suggests that MS id best treated in the early stages of the illness, most physicians in the United States suggest initiating treatment after the first event suggestive of MS.