Decline in ambulatory function

Based on this patient's history and presentation, the likely diagnosis is primary progressive multiple sclerosis (PPMS). PPMS represents around 10% of MS cases and tends to develop about a decade later than relapsing MS. Unlike other forms of MS, this phenotype progresses steadily instead of in an episodic fashion like relapsing forms of MS. Most patients with PPMS present with gait difficulty because lesions often develop on the spinal cord. While relapsing-remitting MS (RRMS) is much more common among women than men, men with MS are more likely to have the progressive form.

Although this patient's MRI ultimately points to multiple sclerosis, his functional deficits may initially suggest other conditions in the differential diagnosis. Brainstem gliomas typically manifest in unsteady gait, weakness, double vision, difficulty swallowing, dysarthria, headache, drowsiness, nausea, and vomiting. Transverse myelitis often presents with rapid-onset weakness, sensory deficits, and bowel/bladder dysfunction. Musculoskeletal and neurologic symptoms are common in Lyme disease. B12 deficiency can present with worsening weakness and a sensory ataxia that can present as balance difficulties, but it would not cause focal lesions on the MRI, nor would it present with bladder symptoms. In addition, the patient's steady decline in function rules out RRMS.

PPMS is diagnosed with confirmation of gradual change in functional ability (often ambulation) over time without remission or relapse. These criteria include 1 full year of worsening neurologic function without asymptomatic periods as well as two of these signs of disease: brain lesion, two or more spinal cord lesions, and oligoclonal bands or elevated Immunoglobulin G index. These timing-specific criteria can delay diagnosis, as seen here.

Ocrelizumab is the only FDA-approved disease-modifying therapy (DMT) proven to alter disease progression in ambulatory patients with PPMS. American Academy of Neurology guidelines recommend ocrelizumab for patients with PPMS who are likely to benefit from this therapy. While it is thought that DMTs are more effective at targeting inflammation in RRMS than nerve degeneration in PPMS, these agents may show benefit for patients with active PPMS (relapse and/or evidence of new MRI activity) rather than inactive disease. A recent PPMS study concluded that among patients with relapse or disease activity, DMTs were associated with a significant reduction of long-term disability risk. Together with immunomodulatory therapy, rehabilitation can help manage symptoms.

Krupa Pandey, MD, Director, Multiple Sclerosis Center, Department of Neurology & Neuroscience Institute, Hackensack University Medical Center; Neurologist, Department of Neurology, Hackensack Meridian Health, Hackensack, NJ.

Krupa Pandey, MD, has serve(d) as a speaker or a member of a speakers bureau for: Bristol-Myers Squibb; Biogen; Alexion; Genentech; Sanofi-Genzyme.

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