ConditionBrain & nerves
Lewis-Sumner Syndrome (Multifocal CIDP)
Lewis-Sumner syndrome is a rare, treatable autoimmune nerve disease in which the immune system strips the insulating coating (myelin) from individual nerves in patches. It causes slowly worsening weakness and numbness in the area of one or a few nerves, most often starting in one hand or arm, and usually uneven between the two sides. It is now classed as a multifocal form of CIDP. Most people improve with immunoglobulin (IVIG) or steroid treatment.
Also called: Multifocal acquired demyelinating sensory and motor neuropathy (MADSAM), multifocal CIDP, Lewis-Sumner variant of CIDP
At a glance
- What it is
- An immune attack on myelin in patches along individual nerves, a multifocal variant of CIDP.
- Pattern
- Asymmetric weakness and sensory loss in the territory of specific nerves, often starting in one arm.
- Course
- Slowly progressive over months to years, or relapsing.
- Diagnosis
- Nerve conduction studies showing conduction block, plus nerve imaging and sometimes spinal fluid tests.
- Treatment
- IVIG first line; steroids, plasma exchange or immunosuppressants as alternatives.
When to get help
Call 911 or go to the ER
- Weakness spreading quickly over days to both sides, with trouble breathing or swallowing
- Sudden weakness or numbness of one side of the body with facial droop or speech trouble (possible stroke). Call 911 or your local emergency number
See a doctor within a day or two
- New weakness of a hand, wrist or foot that is getting worse over weeks
- Worsening weakness while on treatment, or after a planned IVIG dose was delayed
Book a routine appointment
- Patchy numbness, tingling or weakness in one arm or leg lasting more than a few weeks without an injury
- A diagnosis of multifocal motor neuropathy or nerve entrapment that is not responding as expected, especially if numbness is present
What happens in Lewis-Sumner syndrome
Peripheral nerves carry signals between the spinal cord and the limbs. Myelin, the fatty coating around nerve fibers, lets those signals travel fast. In Lewis-Sumner syndrome the immune system damages myelin at scattered spots along certain nerves. At these spots, signals slow down or are stopped completely, which is called conduction block. Muscles supplied beyond the block become weak and the skin they supply loses sensation, even though the nerve fibers themselves may still be intact.
The condition was described by neurologists Richard Lewis and Austin Sumner in 1982. International guidelines now group it under chronic inflammatory demyelinating polyneuropathy (CIDP) as multifocal CIDP. Typical CIDP affects both sides evenly; Lewis-Sumner syndrome is patchy and uneven.
Symptoms
- Weakness in the area of one nerve, for example trouble gripping, pinching or lifting the wrist
- Numbness, tingling or pain in the same area
- Symptoms usually begin in one hand or arm, then spread to other nerves in the same or opposite limb over months
- Legs can be affected, sometimes causing foot drop
- Muscle wasting and cramps in long-standing cases
- Occasionally cranial nerves are involved, causing facial weakness or double vision
It typically starts in adults between their 30s and 50s and is slightly more common in men.
How it differs from similar conditions
| Condition | Sensory loss | Pattern | Other clues |
|---|---|---|---|
| Lewis-Sumner syndrome | Yes | Patchy, asymmetric, often arms first | Conduction block; anti-GM1 antibodies usually absent |
| Multifocal motor neuropathy | No | Patchy, asymmetric | Purely motor; anti-GM1 antibodies often present; steroids ineffective |
| Typical CIDP | Yes | Symmetric, both near and far muscles | Raised spinal fluid protein common |
| Vasculitic neuropathy | Yes | Patchy, often sudden | Painful, axonal damage, may have systemic illness |
| Hereditary neuropathy with pressure palsies | Yes | Recurrent palsies at pressure points | Family history, genetic test |
Distinguishing it from multifocal motor neuropathy matters because steroids can help Lewis-Sumner syndrome but can make multifocal motor neuropathy worse.
Diagnosis
A neurologist examines strength, reflexes and sensation nerve by nerve. Tests include:
- Nerve conduction studies and EMG: the key test. They show conduction block or slowing at sites away from common compression points, and abnormal sensory nerve responses.
- Nerve ultrasound or MRI of the brachial or lumbar plexus: may show thickened, inflamed nerves.
- Lumbar puncture: spinal fluid protein is raised in some patients.
- Blood tests: to exclude diabetes, vitamin B12 deficiency, thyroid disease, paraproteins, vasculitis, HIV and antibodies linked to MMN and other neuropathies.
- Nerve biopsy: rarely needed.
A good response to treatment also supports the diagnosis.
Treatment
- Intravenous immunoglobulin (IVIG): the usual first choice, with many patients improving. It is often given as repeated infusions every few weeks, and the dose and interval are adjusted to the lowest that keeps symptoms stable. Some people switch to immunoglobulin under the skin (subcutaneous) at home.
- Corticosteroids: helpful in some patients, though responses appear less consistent than in typical CIDP.
- Plasma exchange: removes antibodies from the blood; used when other treatments fail.
- Immunosuppressants: such as azathioprine, mycophenolate or rituximab, to reduce reliance on IVIG or steroids, with variable evidence.
- Supportive care: physical and occupational therapy, wrist or ankle splints, and treatment of nerve pain.
Outlook
Lewis-Sumner syndrome is chronic, but most people respond to treatment and keep good function. Early treatment matters, because long-standing demyelination can lead to permanent loss of nerve fibers and fixed weakness. Some people eventually reduce or stop treatment; others need it long term. Regular review by a neuromuscular specialist helps adjust therapy.
Frequently asked questions
What is MADSAM?
MADSAM stands for multifocal acquired demyelinating sensory and motor neuropathy, another name for Lewis-Sumner syndrome. "Multifocal" means patches on several nerves, "demyelinating" means the myelin coating is damaged, and "sensory and motor" means both feeling and strength are affected.
Is Lewis-Sumner syndrome the same as CIDP?
It is considered a variant of CIDP. Current European and Peripheral Nerve Society guidelines call it multifocal CIDP. It shares the same immune mechanism but affects nerves in an uneven, patchy way, unlike typical CIDP, which affects both sides of the body symmetrically.
What is the difference between MADSAM and multifocal motor neuropathy?
Both cause patchy weakness with conduction block. MADSAM also causes numbness and abnormal sensory nerve tests, while multifocal motor neuropathy is purely motor and often shows anti-GM1 antibodies. Steroids may help MADSAM but can worsen multifocal motor neuropathy, so the distinction affects treatment.
Is Lewis-Sumner syndrome progressive?
Untreated, it usually progresses slowly over months to years or follows a relapsing course, spreading to more nerves. With IVIG or other immune treatment, most people stabilize or improve. Treating early helps prevent permanent nerve fiber loss and lasting weakness.
Sources
This guide was written from current patient and clinical guidance, including:
- European Academy of Neurology and Peripheral Nerve Society: Guideline on diagnosis and treatment of CIDP (2021)
- National Institute of Neurological Disorders and Stroke (NINDS): Chronic inflammatory demyelinating polyneuropathy
- GBS/CIDP Foundation International: Lewis-Sumner syndrome (MADSAM)
- Genetic and Rare Diseases Information Center (GARD): Lewis-Sumner syndrome
- NORD: Chronic inflammatory demyelinating polyneuropathy