Can CIDP Cause One-Sided Symptoms? MADSAM Explained

EMERGENCY WARNING: If you experience sudden one-sided weakness or numbness—especially if it is accompanied by facial drooping, difficulty speaking, vision changes, severe imbalance, or a sudden severe headache—seek emergency medical care immediately. These are signs of a stroke or transient ischemic attack (TIA), not CIDP.

If your symptoms have developed gradually over weeks or months, it is possible for them to be asymmetric. While typical CIDP is usually bilateral and relatively symmetric (affecting both sides of the body somewhat equally), some CIDP variants can be asymmetric or focal ^[1]. However, one-sided symptoms alone do not automatically establish a CIDP diagnosis; a thorough neurologic evaluation is required to rule out other causes ^[2].

Understanding Asymmetric CIDP Variants

Because the “textbook” presentation of CIDP is symmetrical, patients whose symptoms don’t follow this pattern often face confusion and diagnostic doubt. However, the 2021 European Academy of Neurology and Peripheral Nerve Society (EAN/PNS) guidelines formally classify these patchy presentations under the umbrella of multifocal or focal CIDP variants ^[2].

The most recognized asymmetric variant is Multifocal Acquired Demyelinating Sensory and Motor Neuropathy (MADSAM), also called Lewis-Sumner Syndrome ^[1][3]. In MADSAM, the immune system attacks the protective myelin coating of the nerves in a patchy, uneven pattern across multiple areas (multifocal). This leads to:

• Asymmetric symptoms: Weakness, numbness, or tingling that is noticeably worse on one side of the body ^[1].
• Upper limb dominance: While it can affect the legs, MADSAM frequently targets the arms and hands more heavily ^[1].
• Sensory and motor issues: Like typical CIDP, MADSAM affects both the sensory nerves (causing numbness) and motor nerves (causing weakness) ^[1].

If your symptoms are strictly confined to just one limb or one specific nerve bundle, doctors may classify this as focal CIDP rather than MADSAM ^[2].

Getting the Right Diagnosis

Because one-sided symptoms can mimic other conditions—such as a pinched nerve, spinal cord issue, entrapment, or other localized nerve disorders—getting an accurate diagnosis requires a comprehensive approach. Diagnosis relies on combining your symptom history and neurological exam with specific testing ^[2].

Doctors rely heavily on nerve conduction studies (tests that measure how fast and strongly electrical signals travel through your nerves). During this testing, clinicians will often evaluate multiple nerves in multiple limbs, including the less-affected or seemingly unaffected side ^[4][5]. Testing only the symptomatic side can lead to missed diagnoses. Finding abnormalities on the less-symptomatic side provides additional evidence that you are experiencing a broader immune-mediated peripheral nerve disorder rather than a localized injury ^[4].

If initial electrical tests are inconclusive, supportive tests like a nerve ultrasound or an MRI of your nerve bundles (the plexus) can be used ^[2][6]. These imaging tools can sometimes spot localized nerve swelling. While helpful, nerve enlargement is not definitively required for a diagnosis, and an abnormal scan does not automatically establish MADSAM by itself ^[2].

Treatment for Asymmetric CIDP

The primary therapies for the MADSAM variant are similar to typical CIDP: Intravenous Immunoglobulin (IVIG) or corticosteroids are generally considered the initial treatment options ^[7][8]. Plasmapheresis (plasma exchange) is another option, commonly considered if initial treatments are ineffective or not tolerated ^[7].

While many patients respond well to these therapies, some research suggests that patients with the MADSAM variant may have different response rates compared to typical CIDP, and often require individualized maintenance therapy to manage symptoms over time ^[9][3]. Because the nerves are attacked in a patchy way, you and your doctor will need to monitor your specific areas of weakness closely to gauge if the treatment is working. Tracking changes in your grip strength, fine-motor tasks, walking ability, and sensory changes between visits will help you and your care team objectively measure your progress.