[Neuropathy versus neuronopathy: distinctive features]

Neuropathy may be difficult to distinguish from neuronopathy, on both motor and sensory sides. A number of disorders that present with characteristic electro-clinical features are readily recognized. Except for those, distinction of the lesions that concern the peripheral nerve cell or the axon may require support of clinical, electrophysiological and other ancillary tests. Distinction between motor neuropathy and neuronopathy can be based on the abnormalities of nerve conduction and on the signs that relate to the reinnervation process. Signs of terminal axonal reinnervation, such as motor axon reflex, may be observed in axonal neuronopathies, whereas only collateral reinnervation occurs in motor neuronopathies. Sensory axonopathies are usually characterized by clinical and electrophysiological findings that are axon length-dependent, by the course of the disorder that is most often chronic, and by possible reversibility. Sensory neuronopathies are usually subacute and induce clinical deficits that are more or less widespread to the whole body surface rather than distal. Follow-up studies disclose limited or absent recovery. A better knowledge of the structural differences of motor and sensory neurons and axons will improve our understanding and lead to the development of specific tests. Meanwhile, although some parameters and techniques should still be improved, electrophysiological and additional tests are useful to detect and to distinguish the peripheral nerve disorders that affect the nerve cell bodies and their axons.