Numbness in the extremities is mostly seen in central nervous system diseases and peripheral nervous system diseases, as follows: 1. Central nervous system diseases: mainly include brainstem lesions and spinal cord lesions, which can lead to numbness in the extremities, accompanied by weakness in the extremities, positive pyramidal fasciculus signs and other symptoms. 2. Peripheral neuropathy: this is a common cause of numbness in the extremities, including diabetes, poisoning, drug factors, metabolic factors and so on, which can lead to numbness in the extremities and weakness. This is a common cause of peripheral neuropathy, including diabetes, poisoning, drug factors, metabolic factors and so on, which may lead to numbness and weakness of the limbs, and these patients may also have symptoms such as low tendon reflexes and negative cone bundle signs. Therefore, when patients have symptoms of numbness in the extremities, they need to selectively improve the relevant tests and examinations such as cranial MRI, cervical MRI, electromyography, lumbar puncture cerebrospinal fluid, etc. according to the form of morbidity and physical examination to clarify the cause.