Chronic inflammatory demyelinating polyneuropathy (CIDP)

CIDP is an inflammatory disease of the peripheral nerves (the nervous system outside the brain and spinal cord). Demyelination means that the fat-rich insulating layer (myelin) around the nerve fibers is broken down, and polyneuropathy means that the function of several nerves is impaired.

The American neurologist James H Austin contributed with one of the earliest descriptions of CIDP in 1958, by describing how a chronic polyneuropathy was improved by treatment with cortisone. It was not until 1984 that the American doctors Peter J Dyck and Barry G Arnason were able to confirm that it was an inflammatory reaction that affected the myelin in peripheral nerves.

In CIDP an inflammatory attack is directed against nerve fibers that control muscle power (motor nerves), sensation (sensory nerves) and sometimes also nerves that control involuntary functions such as heart rhythm or bowel movements (autonomic nerves). The disease often occurs as relapses (periods of deterioration) or has a long-term chronic progressive course. It usually develops symmetrically in several nerves at the same time. Some patients with CIDP have other immune-mediated diseases affecting other organs, simultaneously as CIDP. CIDP can in rare cases be induced by the use of drugs used to treat other immunological disorders.

Guillain-Barré syndrome (GBS)
There is also an acute form of inflammatory polyneuropathy, i.e. Guillain-Barré syndrome (GBS). The most common form of GBS is the acute inflammatory demyelinating polyneuropathy, AIDP), where the myelin is attacked by an acute inflammatory process. There are also axonal forms of GBS, where the nerve fibers are primarily attacked. GBS is potentially life-threating in the acute phase of disease due to the risk of involvement of nerves controlling the breathing muscles and the heart rate.
Whereas the onset of CIDP is insidious and the disease is progressive, GBS progresses rapidly, with a large proportion recovering within 6 to 12 months. GBS is monophasic in ca 95% of cases, i.e. does not re-occur later in life. In around 2/3 of cases, GBS is preceded by an infection during a 4-6 week period prior to developing the neurological symptoms. The covid-19 pandemia in the years 2020-2021 has as yet not been reported to increase the risk of developing GBS.

Multifocal Motor Neuropathy (MMN)

MMN means that there is a disturbance in the motor nerve fibers' transmission of nerve impulses in the peripheral nervous system. This reduces muscle strength, especially in the arms and legs. MMN is caused by inflammation of motor nerves, and is associated with specific types of anti-ganglioside antibodies blocking the nerve signals in motor nerves. The disease is hence also called motor neuropathy with multiple conduction blockages. The symptoms consist of slowly progressive muscle weakness which usually starts in one hand or foot. Over time the weakness spreads unevenly (asymmetrically) to the other limbs, and muscle atrophy (loss of muscle) may be seen, especially if treatment is delayed.