12th August 2024

Terminology

Neuropathies affecting a single nerve are termed mononeuropathies and are generally secondary to trauma or compression. Specific deficits and causes are discussed below.

Mononeuritis multiplex involves multiple, asymmetric, non-contiguous nerves. It is most commonly caused by a vasculitic process (polyarteritis nodosa, rheumatoid arthritis, systemic lupus erythematosus, or the ANCA-associated vasculitides) but can also have infectious (HIV, hepatitis), drug-related or infiltrative (sarcoidosis) aetiologies.

Polyneuropathy refers to a generally systemic, relatively homogenous process affecting multiple peripheral nerves.  They can be divided by aetiology or by pathological process (axonal or demyelinating), as in the table below. Nerve conduction studies (NCS) can be used to differentiate these latter distinctions, with demyelination giving a slowed conduction velocity with or without conduction blocks. An axonal neuropathy, by contrast, decreases the amplitude of potentials (compound muscle action potentials, CMAPs, and sensory nerve action potentials, SNAPs) due to damage to axons, while conduction velocity is generally relatively preserved until the disease is severe.