The hug reflex is the most defensive reflex of infants. For infants under 3-4 months old, when the mother or family members suddenly walk up to the child or make loud noises, the child will be found to have two arms abducted and straightened, and then flexed and received in front of the chest in the shape of hug, which is a physiological phenomenon, medically known as hug reflex. This is a physiological phenomenon, which is medically known as hug reflex. The weakening or disappearance of hug reflex may be caused by the neurological damage of newborns, and the following are the specific possible causes. Infections include bacterial infections, such as septic meningitis, brain abscess, caused by various septic bacteria; viral infections, such as epidemic B encephalitis caused by epidemic B encephalitis virus, epidemic chest pain caused by type B Coxsackie virus, poliomyelitis caused by poliovirus, kuru disease or lentiviral infections, while subacute sclerosing alloencephalitis may be caused by a mutant strain of measles virus; parasitic infestations, such as cerebral malaria, cerebral and Parasitic infestations, such as cerebral malaria, cerebral schistosomiasis, cerebral cysticercosis; fungal infections, such as Candida albicans and cryptococcal meningitis; and leptospira may also cause meningoencephalitis. Some of the causes of epilepsy are local scar formation as foci after meningeal or cortical infections. Poisoning includes metal poisoning, such as lead poisoning, which can cause peripheral motor nerve paralysis and lead encephalopathy; mercury, arsenic, and thallium poisoning, which also affect the nervous system; organic poisoning, such as alcohol poisoning and barbiturate poisoning, which can suppress the central nervous system; organophosphorus poisoning, which can cause cholinergic hyperexcitability; bacterial toxin poisoning, such as botulism, which can cause cranial nerve paralysis and limb weakness; diphtheria toxin, which can cause nerve paralysis; and tetanus toxin, which can cause generalized skeletal muscle strength. Toxins can cause tonic spasms of skeletal muscles throughout the body; animal toxins (toxins contained in coelenterates, shellfish, poisonous mosquitoes, spiders, puffer fish, etc.) can also cause neurological symptoms (muscle weakness, paralysis, convulsions, ataxia, etc.). Genetic defects Many metabolic diseases (such as phenylpropionic aciduria, glycogen storage disease, mucopolysaccharidosis, lipid storage disease), degenerative diseases (such as cerebral leukodystrophy, Parkinson’s disease, amyotrophic lateral sclerosis, hereditary optic nerve atrophy, etc.) and myopathies (such as progressive muscular dystrophy) affecting the nervous system are genetic diseases. Most of them are autosomal recessive. In contrast, hyper- and hypokalemic periodic paralysis is autosomal dominant. Nutritional disorders Patients with Kwashiorkor disease (a type of protein-thermal malnutrition) may have neurological symptoms such as tremor, slow movement, and myoclonus. Intracranial hypertension can be caused by either vitamin A deficiency or toxicity. Vitamin B deficiency can affect the nervous system, e.g., vitamin B1 deficiency (pediculosis) manifests as most peripheral nerve damage, and vitamin B12 deficiency can cause subacute combined degeneration. Immune damage Post-vaccination encephalitis may be the result of a metamorphic reaction caused by protein antigens contained in the vaccine. Infected polyneuritis, facial nerve palsy, post-infection abducens nerve palsy, and post-infection glossopharyngeal nerve palsy may be metaplastic disorders of the peripheral nerves. Connective tissue diseases such as rheumatic fever, systemic lupus erythematosus, and polyarteritis nodosa are autoimmune diseases that may involve the nervous system, such as rheumatic fever that may manifest Sydenham’s chorea. Demyelinating diseases of the central nervous system may be autoimmune diseases caused by viral infections, such as diffuse sclerosis, acute disseminated encephalomyelitis, multiple sclerosis, subacute sclerosing holoprosencephalitis, optic neuromyelitis optica, transverse myelitis optica, acute cerebellar ataxia, and pontocerebellar central myelin melting disease. Myasthenia gravis is also an autoimmune disease. Metabolic disorders In addition to the above genetic metabolic diseases (such as glycogen storage disease) that can affect the nervous system, acquired metabolic diseases, such as hypoxia, hypernatremia, hyponatremia, hypocalcemia, uremia, hypoglycemia, and hepatic encephalopathy, can be associated with neurological symptoms. Endocrine disorders Thyroid hormone can promote brain myelination and stimulate RNA and protein synthesis, and children with cretinism have delayed brain development and cerebellar ataxia. Hyperthyroidism may be accompanied by tremor and hyperreflexia. In diabetes mellitus, insufficient insulin secretion leads to peripheral nerve demyelination and neurological deficits. Congenital malformations are caused by teratogenic factors such as viruses or toxins, or are hereditary. For example, spina bifida, congenital hydrocephalus, cerebral penetration malformation, etc. Blood circulation disorders Cerebrovascular disorders can be caused by vascular disorders, blood component mutagenesis, hemodynamic disturbances, or emboli. Abnormal proliferation Abnormal tissue proliferation can form tumors. They can be seen in the central and peripheral nerves.