Weakness (synonyms: partial or complete paralysis, paresis, paralysis) in the arms and legs can have different causes. These include firstly the muscles themselves, secondly, the motor nerves that run from the spinal cord to the muscles (peripheral motor neurons) and thirdly, the motor nerves that control the peripheral motor neuron in the spinal cord from the brain (central motor neurons). In milder forms, people may often drop things for no apparent reason or simply notice that they are stumbling or falling more often. 1) Muscular Direct diseases affecting the musculature, such as muscular dystrophies, myasthenia 2) Peripheral Nervous System Herniated disc, constriction syndromes (carpal tunnel syndrome), polyneuropathies, spinal stenosis, nerve root inflammation 3) Central Nervous System Stroke, multiple sclerosis, tumors, paraplegia, Various, often very severe diseases involving structural damage to the central nervous system (stroke, multiple sclerosis, tumors, paraplegia, spinal stenosis, craniocerebral injury, etc.) can be the cause of this weakness. In the case of paralysis caused by the central nervous system, there is usually also stiffness (spasticity), which can be so strong that the examiner is only able to move the arm or leg by applying a very large force. Amyotrophic lateral sclerosis (ALS) is a special case, in which both peripheral and the central motor motor neurons are usually affected.
