What Is a Demyelinating Disease?

Nerve fibers are divided into unmyelinated nerve fibers and myelinated nerve fibers. Myelinated nerve fibers, such as preganglionic fibers and larger somatic nerve fibers, have an outer sheath called a myelin sheath. Myelin consists of the cell membrane of myelin cells. Myelin sheath cells of the central nervous system are oligodendrocytes, and myelin sheaths of peripheral nerve fibers are composed of Schwann cells. Myelin consists of lipids and proteins. It protects the axon and has an insulation effect on nerve impulses, which can accelerate the conduction of nerve impulses. Impulse transmission of thick myelin fibers is also fast. When the myelin sheath is damaged, the conduction speed slows down. Nerve conduction is also affected by temperature, and an increase in body temperature during demyelination can cause conduction block.

Demyelinating disease

Nervous system diseases with neuromyelin depletion as the main or primary lesion and axon, cell body and glial damage being relatively mild. Can occur in the central nervous system or the peripheral nervous system.

Demyelinating disease concept

Demyelinating disease group

That is, myelin formation disorder and myelin destruction. Myelin sheath dysmyelinating disease is a myelin sheath disorder caused by genetic metabolic defects, mainly including malnutrition of white matter caused by abnormal myelin phospholipid metabolism, such as metachromatic white matter encephalopathy, white matter sponge-like degeneration, and adrenal white matter nutrition Bad etc. Demyelinating demyelinating disease is an acquired demyelinating disease.

Causes of demyelinating disease

Immune-mediated, such as multiple sclerosis, acute infectious polyradiculoneuritis. Viral infections, such as progressive multifocal leukoencephalitis and subacute sclerosing panencephalitis. Nutrition disorders, such as central pontine myelinolysis. Hypoxia, such as demyelinating encephalopathy and progressive subcortical ischemic encephalopathy after delayed hypoxia. Generally, the clinical diagnosis of demyelinating diseases refers to immune-mediated demyelinating diseases, including multiple sclerosis, acute infectious polyradiculoneuritis and so on.

Pathological manifestations of demyelinating disease

The sacroiliac nerve fiber myelin damage is mainly distributed around the veins of the white matter region of the central nervous system, or it is multiple, scattered in small lesions, or merges into multiple lesions, or forms multiple centers; sacroiliac nerve cells, axons and nerve tissues Remain relatively intact; inflammatory cells infiltrate around blood vessels; no Wallerian degeneration or secondary fibrous bundle degeneration

Causes of headaches in demyelinating diseases

Demyelinating diseases are a large group of diseases with different etiology and different clinical manifestations, but they have similar characteristics of acquired diseases. The characteristic pathological change is the loss of myelin sheath of nerve fibers while the nerve cells remain relatively intact. The role of myelin sheath is to protect neurons and make nerve impulses pass quickly. Therefore, the loss of myelin sheath will affect the transmission of nerve impulses. Nerve myelin sheaths in acute demyelinating diseases can be regenerated at a faster and more complete degree. Although the regenerated myelin sheaths are thin, they generally have little effect on functional recovery. Chronic demyelinating neuropathy, due to repeated demyelination and remyelination, Schwann cells obviously proliferate, nerves become thicker, and axons are lost, so functional recovery is incomplete. The incidence of headache in demyelinating diseases is not high, but patients with demyelinating sheaths also have headache attacks. There are two reasons to summarize: nerve irritating symptoms, normal nerve fibers, sensory impulses occur in nerve endings and cell bodies, exercise Impulses occur in the cell body; diseased nerve fibers can occur in the middle of the axon and be transmitted to the surroundings and the center. Such ectopic impulses can be caused by increased susceptibility, are very sensitive to mechanical stimulation, or can be spontaneous. Occurs immediately following the normal impulses of the same fiber or a stimulus causes repeated excitement at the diseased site, which can cause pain. Demyelination is accompanied by infiltration of lymphocytes, plasma cells, and polymorphonuclear leukocytes, forming a severe inflammatory response. Stimulating the meninges may even cause increased intracranial pressure and cause headaches.

Classification of demyelinating diseases

Demyelinating disease

It is a nervous system autoimmune disease that develops through a hypersensitivity reaction with myelin sheaths or myelin cells as target organs. Among them, acute infectious polyradiculoneuritis is a common multiple peripheral neuropathy, and it is also common in China. Acute disseminated encephalomyelitis is also a common disease in sporadic encephalitis in China. Multiple sclerosis is an extremely frequent neurological disorder in the Caucasian race in North America and Northern Europe. Western countries have conducted extensive clinical and basic research on this disease to illustrate the pathogenesis of immune-mediated demyelination and promote immunological progress. Multiple sclerosis has a lower incidence in China than in the West. Experimental allergic encephalomyelitis (EAE) can be used as an animal model of acute disseminated encephalomyelitis. EAE is caused by injection of brain tissue extract or myelin basic protein (MBP) with an adjuvant. The course of EAE is prolonged and recurrent, and it may belong to the animal model of multiple sclerosis. Clinicopathological and immune studies indicate that both cellular and humoral immunity are involved in the pathogenesis of allergies. Studies have shown that suppressor T cells (TS) decrease and the ratio of suppressor T cells / helper T cells (TS / TH) decreases during the active phase of the disease. This indicates that there is an immune disorder. Family history, co-morbidity and HLA-related studies have shown that there are genetic factors in the onset of multiple sclerosis, and epidemiological investigations indicate that it is also affected by environmental factors. It is generally believed that multiple sclerosis is caused by immune regulation disorders caused by certain external causes on the basis of heredity. The exact etiology is not clear, and it is suspected as lentivirus. The main lesion of acute infectious polyradiculoneuritis is the peripheral nerve. The pathogenesis is similar to multiple sclerosis. Experimental allergic neuritis (EAN) is an animal model of the disease. EAN is caused by injection of the basic protein component (P2) of peripheral nerve tissue or myelin sheath with adjuvant. Clinical and immunological studies have also shown that it is immune-mediated peripheral neuropathy.

Acute disseminated encephalomyelitis with demyelinating disease

It is a demyelinating disease characterized by extensive white matter inflammatory demyelinating changes in the brain and spinal cord. It can be seen after vaccination (referred to as post-vaccination encephalomyelitis), such as after rabies vaccination; also after infection (referred to as post-infection encephalomyelitis), it is more common after virus infection, especially in children with rash It is not uncommon for patients with sexually transmitted diseases, such as measles, mumps, chickenpox, to have an upper respiratory tract infection before the disease. In some patients, the symptoms of pre-ill infection may be insignificant or clinically infected.

Acute disseminated encephalomyelitis is usually acute or subacute. It is characterized by symptoms and signs of diffuse brain damage, such as hemiplegia, aphasia, cranial nerve palsy, convulsions, and mental disorders. In severe cases, disturbance of consciousness, debraining, or decortical rigidity can occur. Increased intracranial pressure may occur when cerebral edema is severe. Some patients have symptoms limited to the brainstem or spinal cord. Cerebrospinal fluid examination of cells and proteins may be mild or moderately elevated, and it is not uncommon to see normal in routine examinations. EEG examinations can have severe, diffuse abnormalities. CT and MRI (Magnetic Resonance Examination) can show multiple demyelinating lesions mainly in the white matter of the brain.

The diagnosis needs to be distinguished from sporadic viral encephalitis, especially herpes simplex virus encephalitis. The prognosis of this disease is good. Some cases can recur, and the relationship with multiple sclerosis is inconclusive. In addition to symptomatic and supportive treatment, corticosteroids are effective.

Acute hemorrhagic leukoencephalitis with demyelinating disease

Pathological and experimental allergic encephalomyelitis studies have shown that the disease is an outbreak of acute disseminated encephalomyelitis. Pathologically, it is characterized by allergic vasculitis and spot-like bleeding of white matter that can be fused into a slice. Onset is severe, symptoms are severe, and prognosis is poor.

Diffuse sclerosis of demyelinating disease

Demyelinating encephalitis is characterized by inflammatory myelination of diffuse white matter in the brain. PF Hilde was first described in 1912 and named as diffuse periaxial encephalitis, so this disease is also called Hilde's disease. But the diseases described by Hilde actually include three different diseases: white matter malnutrition and subacute sclerosing panencephalitis. Diffuse sclerosis currently diagnosed refers to those with acute demyelinating encephalitis. More than the onset of childhood, subacute progressive course, manifested as cone bundle sign, hemiplegia, central deafness, central dark vision loss, behavior changes, etc.

Concentric circular sclerosis

The inflammatory demyelinating disease is characterized by pathological features in which the myelin depletion area and the relatively complete area are alternately arranged in a concentric circle, fan-shaped or corrugated type. J. Baoji was first reported in 1928, so it is also called Baoji's disease. Head CT can display low-density images. Some people think that it is a special manifestation of multiple sclerosis or diffuse sclerosis. In fact, it is a pathological diagnosis, which is difficult to distinguish clinically from other demyelinating encephalitis such as acute disseminated encephalomyelitis. Since the 1980s, it has been found that MRI examinations can show similar pathological demyelinating shadows for clinical diagnosis.

Demyelinating disease multiple sclerosis

It is a demyelinating disease characterized by multiple lesions of the central nervous system white matter, remission and recurrence. In the acute active phase, there are multiple inflammatory demyelinating plaques in the white matter of the central nervous system, and sclerotic plaques are formed due to the proliferation of glial fibers in old lesions. This disease is a common and multiple neurological disorder in the Northeastern and North American Caucasians, with a prevalence of more than 40 / 100,000. The prevalence of Chinese people is much lower than that of the West and is similar to that of Japan, which is about 2-3 per 100,000. More common in young and middle-aged; women are more common than men.

The disease is mostly acute or subacute, and may have a history of pre-ill infection, or it may occur after vaccination or childbirth. Excessive fatigue, tension, and mood swings can also be used as triggers for onset or recurrence.

Symptoms are complex due to multiple lesions, which vary from lesion to lesion. Lesions were found in the spinal cord and optic nerve, followed by the brain stem, hemisphere and cerebellum. Paraplegia, bundle or segmental sensory disturbances can occur when the lesion is located in the spinal cord; unilateral or bilateral neuritis or posterior optic neuritis occurs when located in the optic nerve; cranial nerve palsy, limb paralysis occurs when located in the brainstem; appears in the cerebellum Ataxia, limb tremor (intentional tremor), and nystagmus; symptoms such as hemiplegia, aphasia, mental retardation, and mental disorders when located in the cerebral hemisphere. It is worth noting that the symptoms and signs of the patient at the first onset may be limited to a single lesion. Another feature is that transient, transient symptoms can occur, such as continued diplopia for a few minutes or hours, and transient, frequent episodic symptoms, such as painful cramps and paresthesia.

Cerebrospinal fluid examination revealed a mild or moderate increase in white blood cells and proteins, but it was normal. Immune indicators such as oligoclonal zone and IgG intrathecal synthesis rate were mostly positive. Imaging studies (CT, magnetic resonance) can show lesions, especially lesions in the cerebral hemisphere. The typical findings are multiple lesions located around the ventricle and subcortical white matter.

Multiple sclerosis is characterized by its course of remission and relapse. After the initial remission, symptoms can be asymptomatic or only slight residual symptoms can be left, and after several attacks, the disease gradually worsens. Some patients have no significant residual symptoms after several episodes and can be relieved for a long time. This is a benign type, and a small number of patients can progress without obvious relief. The average survival time is 30 years.

The main points of diagnosis are multiple lesions and the course of remission and relapse. Electrophysiological (evoked potential) and imaging examinations can find clinically infamous lesions, which is helpful for diagnosis. Cerebrospinal fluid immune abnormalities can support clinical diagnosis.

Corticosteroid treatment can promote the relief of symptoms in the acute phase. It has obvious effect on the frequent epidemic symptom. To prevent recurrence, avoid predisposing factors.

Demyelinating disease optic neuromyelitis

It is a demyelinating disease that affects the optic nerve and spinal cord simultaneously or successively. At present, it is generally considered to belong to the multiple spinal optic nerve spinal cord type. In 1894, the French physician E. De Wick first reported, so it is also called De Wick's disease, more common in China than multiple sclerosis. It is manifested by binocular vision loss, limb weakness, numbness, and difficulty urinating.

Demyelinating disease acute polyradiculoneuritis

Also known as acute infectious radiculoneuritis (Guillain-Barre's syndrome), it is an acute onset of peripheral neuroinflammatory, segmental demyelinating disease. Most often occur in children and young people. The male to female ratio is approximately 2: 1. Can be distributed throughout the year, but it is more common in summer. Most patients have a history of upper respiratory infections, intestinal infections, or other infections. The main clinical manifestation of this disease is flaccid paralysis of the extremities, and about half of the patients may be complicated by unilateral or bilateral multiple cranial nerve palsy, which is mainly caused by dyskinesia. In severe cases, swallowing, difficulty in expectoration, and paralysis of the respiratory muscles can occur. Cerebrospinal fluid protein cell separation (normal or slightly higher white blood cells in the cerebrospinal fluid and significantly increased protein) is a prominent manifestation of the disease. The electroencephalogram showed a slowing of the impulse conduction speed and a delayed F-reflex. The prognosis of this disease is good. If you can survive the acute phase safely, especially critically ill patients can keep the airway open, maintain respiratory function, and prevent complications of pulmonary infection, they will be able to heal themselves. Individual patients can die from cardiac arrest caused by autonomic nerve disorders. In a few cases, residual dyskinesia and muscle atrophy have differing opinions on corticosteroid treatment, and plasma exchange can be used in critically ill patients.

Polyradiculoneuritis can also have a chronic course called chronic inflammatory demyelinating polyneuropathy (CID, or chronic Guillain-Barre's syndrome). General clinical features such as acute patients, but the course of the disease is delayed, more than 3 months, and remission and relapse can occur. Can be acute or slow. Pathological changes of onion-like myelin sheaths are formed due to repeated demyelination and regeneration. The increase of thoracic spinal fluid protein is more prominent than that of acute patients, and it tends to decrease as the disease improves. The effect of corticosteroid treatment is significant. To avoid relapses, maintenance doses are required. Early diagnosis and treatment can prevent severe sequelae.

Demyelinating disease due to nutritional disorders

Such as central pontine myelin disintegration, which may be caused by malnutrition and alcoholism, is manifested as rapid paraplegia or quadriplegia, with obvious symptoms of pseudobulbar palsy, in severe cases often coma, can be 2 to 3 He died within a week without specific therapy.

Demyelinating disease

It is a hereditary disorder of lipid metabolism. Most are autosomal recessive, and most often develop after birth or childhood, with different clinical manifestations. No specific therapy.

Demyelinating disease acid lipase deficiency can cause Walman's disease

After birth, he showed weakness, hepatosplenomegaly, diarrhea, bloating, and retarded intellectual development. Galactosylsphingosine lipid storage disease, also known as globular cell white matter dystrophy, is caused by galactocerebroside -galactosidase deficiency, showing severe mental and motor disorders. Metachromatic leukodystrophy, that is, thiocerebral lipid storage disease, is caused by a lack of arylsulfatase activity, manifesting as gait instability, mental degradation, urinary incontinence, blindness, etc. Cerebral tendon xanthomatosis, showing tendon xanthomas, mental retardation, dementia, progressive cerebellar ataxia, spasticity, cataracts, etc. Spongiform degeneration of white matter in the brain is more common in boys. The pathological feature is spongiform degeneration of white matter, which stops myelin formation during the fetal period. It is manifested by low to high muscle tone, spastic bilateral paralysis, progressive dementia, seizures, and optic atrophy Wait. Leukodystrophia in megacephaly infants, the main pathological changes are brain enlargement, extensive myelin sheath loss, manifested as hydrocephalus, muscle tension first and then increase, mental retardation, mostly death within 3 years of age.