Does an MRI Diagnose Multiple Sclerosis?
Abstract & Commentary
By Joseph E. Scherger, MD, MPH, Clinical Professor, University of California, San Diego. Dr. Scherger reports no financial relationships to this field of study.
Synopsis: An MRI is often used to assist in the diagnosis of multiple sclerosis. This systematic review of 29 studies shows that an MRI will result in an overdiagnosis of MS when used after one episode of neurologic dysfunction. A negative MRI may contribute to an underdiagnosis of MS. While the MRI may be useful in the diagnosis of MS, the study lacks the specificity and sensitivity to be relied on as a primary diagnostic tool.
Source: Whiting P, et al. Accuracy of magnetic resonance imaging for the diagnosis of multiple sclerosis: systematic review. BMJ. 2006;332:875-884.
Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system characterized by multifocal areas of demyelination and variable degrees of axonal loss and gliosis resulting in neurologic dysfunction. This definition based on neuropathologic evidence is not practical clinically since biopsy of the central nervous system is not feasible. Hence, the diagnosis is made clinically based on recurrent episodes of neurologic dysfunction such as optic neuritis, transverse myelitis, double vision, or numbness or tingling of the leg. Many years may elapse between first and second episodes, and not all patients who experience a first attack develop multiple sclerosis.
Magnetic resonance imaging (MRI) may assist in earlier diagnosis of MS by visualization of white matter lesions suggesting demyelination in the brain or spinal cord that are clinically silent. In 2001, an international panel on the diagnosis of multiple sclerosis published diagnostic criteria which allows for an early diagnosis of MS after one clinical attack if the patient also meets criteria for a positive result on an MRI.1 These are referred to as the McDonald criteria and have resulted in earlier diagnosis of MS worldwide, both to the benefit and detriment of patients.
Patients may benefit from early diagnosis by receiving early disease limiting treatment, such as interferon beta-1α. It remains controversial whether the ultimate course of the disease can be modified by early treatment due to a lack of long-term studies of more than 10 years. Patients may be harmed from early diagnosis if they do not ultimately have MS, and receive both the negative psychological consequences of being labeled with the disease and an inability to get life and health insurance.
This systematic review concludes that the accuracy of MRI for the early diagnosis of MS has inflated estimates of test performance based on studies with methodological weaknesses. The use of MRI to confirm multiple sclerosis on the basis of a single attack of neurological dysfunction may lead to overdiagnosis and overtreatment.
Over the past 10 years I have noticed an increasing number of patients reporting a diagnosis of MS. Some have no apparent neurologic dysfunction. They report a past episode of weakness of some type and that an MRI confirmed the diagnosis of MS. Such a diagnosis has a profound impact on a patient's sense of well-being and potential in life!
To get an idea of the passion and controversy in the criteria for diagnosing MS, look at the responses to this article in the BMJ (available through Pub Med and bmj.com). Many clinicians are wedded to the early diagnosis of MS, and strongly believe that early therapy may prevent the development and progression of the disease. This is fine if the patient actually has MS. Receiving interferon therapy is not a matter to be taken lightly.
The systematic review by Whiting et al gives some idea of the natural history of transient neurologic dysfunction. In one study of optic neuritis, a common presenting symptom of MS, only 38% of patients developed the disease by 10 years.2 Other clinically isolated symptoms of the brain and spinal cord showed that 68% developed MS by 14 years.3 In patients with mild and transient findings, a wait and see approach is still taken by the wise clinician.
This systematic review of the use of MRI in the diagnosis of MS, the first of its kind, reminds us that advanced imaging does not make a definitive diagnosis. Only tissue can do that. While this is not practical for MS, and the diagnosis must be made clinically, we must avoid an over reliance on MRI and avoid the mislabeling of patients with this very serious disease.
1. McDonald WI, et al. Recommended diagnostic criteria for multiple sclerosis: guidelines from the international panel of the diagnosis of multiple sclerosis. Ann Neurol. 2001;50:121-127.
2. Beck RW, et al. High- and low-risk profiles for the development of multiple sclerosis within 10 years after optic neuritis: experience of the optic neuritis treatment trial. Arch Ophthalmol. 2003;121:944-949.
3. Brex PA, et al. A longitudinal study of abnormalities on MRI and disability from multiple sclerosis. N Engl J Med. 2002;346:158-164.