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TABLE 2.1 Varieties of MS

Asymptomatic MS

Autopsy studies indicate there are individuals without any known clinical history who have neuropathologic changes typical of MS. It is difficult to get an accurate estimate of subclinical disease, but one recent review suggested asymptomatic MS might account for up to 25% of all cases.

Relapsing-remitting MS

This is the major MS subtype. Approximately 85% of patients with a diagnosis of MS start out with relapsing MS. Overall, this subtype accounts for 55% of MS. Relapsing MS patients show a high rate of inflammatory lesion activity (gadolinium-enhancing lesions).

Benign relapsing MS

This category represents a subset of relapsing patients who have few attacks and make an excellent recovery. They show minimal impairment and disability, even after 20-30 years. The proportion of MS patients with benign disease is controversial. Reasonable studies suggest 10-20% of people with MS fit into this category.

Primary progressive MS

This subtype accounts for 10% of MS. Patients show gradual worsening from onset, without disease attacks. These patients tend to be older and often present with a spinal cord dysfunction without obvious brain involvement. This subtype is the least likely to show inflammatory lesion activity on MRI (gadolinium-enhancing). Unlike the other subtypes of MS, men are as likely as women to develop primary progressive MS.

Progressive relapsing MS

This subtype accounts for 5% of MS. Patients show slow worsening from onset, with superimposed attacks. Recent studies suggest these patients are similar to primary progressive patients.

Secondary progressive MS

This is the major progressive subtype and accounts for approximately 30% of MS. Relapsing MS patients usually transition to secondary progressive disease. They show gradual worsening, with or without superimposed relapses. Natural history studies of untreated relapsing MS indicate 50% of patients will be secondary progressive at 10 years and almost 90% by 25 years. This form of MS shows a lower rate of inflammatory lesion activity than relapsing MS, yet the total burden of disease continues to increase. This most likely reflects ongoing axonal loss.

Acute MS

Also referred to as Marburg variant MS, this is the most severe form of MS. Significant disability develops much more rapidly than usual, over weeks to months. Pathologic changes are widespread and destructive. These cases are rare and generally occur in young people.

Clinically isolated syndromes

This refers to patients who present with an isolated CNS syndrome (optic neuritis, incomplete transverse myelitis, brainstem or cerebellar lesion), which is often the first MS attack. Clinical, MRI, and CSF studies indicate that such patients with normal brain MRI and CSF have a low risk of developing MS. In contrast, those with abnormal MRI have a high risk of developing MS.

NOTE: CSF = cerebrosinal fluid; MRI = magnetic resonance imaging

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