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Final Program


Final Program

Multiple Sclerosis and other Neurological Conditions

228 - Multifocal acquired demyelinating sensory and motor neuropathy (MADSAM) or Lewis-Sumner syndrome with unusually rapid progression, refractory to standard-of-care therapies, and profoundly elevated GM1 antibodies.

Thursday, February 19, 2026
5:00 PM - 6:30 PM AST
Case Diagnosis: Multifocal acquired demyelinating sensory and motor neuropathy (MADSAM) or Lewis-Sumner syndrome with unusually rapid progression, refractory to standard-of-care therapies, and profoundly elevated GM1 antibodies.

Case Description: A 48-year-old woman with previously independent function developed sudden right upper extremity numbness, tingling, and weakness, which rapidly spread to the left arm and then to both lower extremities, resulting in quadriplegia with distal sensory loss and areflexia within four weeks. EMG/NCS demonstrated subacute demyelinating sensorimotor polyneuropathy, and CSF protein was elevated, confirming CIDP. She had profoundly elevated GM1 antibodies, a rare finding in < 5% of CIDP patients. Despite receiving standard-of-care therapies including IVIG, corticosteroids, and plasmapheresis, she showed minimal improvement. Only after escalation to FcRn inhibition alongside ongoing immunotherapy, including Rituximab, did she experience dramatic recovery, ultimately regaining independent ambulation within months.

Discussions:

This case illustrates an atypically rapid CIDP course, progressing from independent function to quadriplegia in just four weeks. CIDP typically develops over at least eight weeks, making this presentation unusually fast. Onset was asymmetric, starting in the right upper extremity, spreading to other limbs, unlike the symmetric, ascending pattern typical of acute inflammatory neuropathies such as GBS. Multifocal conduction block on EMG/NCS confirmed a Lewis-Sumner variant. While this pattern is similar to multifocal motor neuropathy (MMN), the presence of sensory involvement distinguishes it. Considering sensory involvement, GM1 Antibody elevation is atypical given it is marker for MMN or pure motor CIDP. Standard therapies provided limited benefit, whereas combination immunotherapy including FcRn inhibition produced near complete functional recovery. This case emphasizes the need for early recognition of atypical presentations, evaluation for uncommon immunologic markers, and prompt escalation beyond conventional therapies.

Conclusions:

Rapid recognition of atypical CIDP presentations is critical, and when standard therapies fail, clinicians should promptly escalate treatment and consider all appropriate FDA-approved immunomodulators to achieve meaningful recovery.