subacute combined degeneration
Introduction
Introduction to subacute combined degeneration The subacute combined degeneration of the spinal cord (subacute combined degeneration of the spinal cord) is referred to as subacute combined degeneration (SCD), which is a disease of central and peripheral nervous system degeneration caused by insufficient vitamin B12 intake, absorption, binding, transport or metabolic disorders. . The lesions mainly involve the posterior cord, lateral cord and peripheral nerves of the spinal cord. The clinical manifestations are deep sensory loss of the lower limbs, sensory ataxia, spastic paralysis and peripheral neuropathy, often accompanied by clinical signs of anemia. basic knowledge The proportion of sickness: 0.003%-0.007% Susceptible people: no special people Mode of infection: non-infectious Complications: anemia
Cause
Subacute combined degenerative cause
Genetic factors (35%):
Recent studies have suggested that subacute combined degeneration of the spinal cord has its own immunological pathogenesis, and its own genetic quality may play an important role. Autoimmune dysfunction can produce antibodies to the parietal cells or antibodies to the internal factors. Gastric mucosal lymphocytic infiltration affects the acid secretion of the stomach and the secretion of internal factors. In patients with autoimmune atrophic gastritis, anti-IF immunoglobulin may be closely related to the selective absorption of vitamin B12.
Disease factors (45%):
Gastrointestinal diseases, gastrointestinal resection can directly affect the absorption of vitamin B12 and lead to vitamin B12 deficiency. There are data indicating that 15% of patients with partial gastrectomy have significant serum vitamin B12 levels, congenital internal factor deficiency or transport of cobalt. Disorders of adiponectin metabolism can affect the metabolic process of vitamin B12. It has also been reported that breast-fed infants are ill due to too little vitamin B12 in the mother.
Pathogenesis
Vitamin B12 is also called cobalamin due to its cobalt content in the molecule. B12 in food needs to be bound to protein, acid-hydrolyzed in the stomach or trypsin in the intestine to separate it from the protein, and then secreted by gastric mucosal cells. A specific glycoprotein called "intrinsic factor" (IF), which is absorbed at the distal end of the ileum. When passing through the ileal mucosa, vitamin B12 dissociates from IF and binds to transcobalamin II in plasma to form B12. -T(II) complex, which is transported by blood and can be combined with cell surface receptors to transform into cells to form hydroxycobalamin, methylcobalamin or 5'-deoxyadenosylcobalamin. The former can Converted into the latter two, more stored in the liver, methylcobalamin is involved in the methylation of homocysteine to form methionine and tetrahydrofolate, 5'-deoxyadenosylcobalamin catalyzes methyl propyl Acyl CoA is converted to succinyl-CoA. Vitamin B12 deficiency can cause methyltetrahydrofolate, cysteine and methylmalonic aciduria, fatty acid synthesis is also affected, branched-chain fatty acid synthesis is increased, and neuromyelin is normal. Synthetic transformation is disturbed, normal cells The structure may be destroyed, the demyelination of the myelin sheath appears, which is the main mechanism of nervous system damage. Some scholars believe that the damage of the nervous system is mainly due to the inactivation of vitamin B12-dependent enzyme (methionine synthetase), making methionine organisms Reduced synthesis.
The lesions are mainly in the posterior cord of the spinal cord and in the lateral cord. The middle and thoracic spinal cord is the earliest and most severely damaged. The more the lesion is to the neck, the less the posterior cord is damaged, especially in the thin section. The bundle of the lower lumbar spinal cord only involves the pyramidal tract, and there is an ovoid pale area in the central white matter of the posterior cord, which extends to the surrounding area, and then involves the lateral cord. In severe cases, the cortex is not damaged, and the white matter includes the posterior cord. The pyramidal tract and the cerebellar tract of the spinal cord are involved. The myelin sheath is swollen and damaged in the damaged area, and then the axon is degenerated. In the past, B12 deficiency was only caused by demyelination, and the same findings were found in animal experiments. It has been proved that B12 deficiency can cause axonal degeneration, and early treatment can achieve complete recovery, indicating that the lesion can be stopped at a certain stage. At this time, the axon may only be damaged in a small part, and whether the myelin sheath has been lost or not can be regenerated. Inconclusive, in the course of the lesion, there may be astrocyte reaction, acute astrocytic body slightly swelling, thickening of the abundance, increased number; chronic development, first in the early damage of the glial fibrosis, And recently Glial hyperplasia in the lesion area is not obvious. A small number of patients have small unclear demyelination around the blood vessels in the white matter of the brain. It can be seen in the coronary radiation, but does not damage the inner capsule, the cerebral peduncle and the conduction beam of the pons. The characteristics of the lesion are similar to those seen in the spinal cord. In addition, hemorrhage and fibrosis of capillaries and arterioles can be seen.
There is controversy about whether vitamin B12 deficiency causes peripheral neurodegeneration. Early studies suggest segmental demyelination. More recent reports suggest that axonal degeneration is predominant. Muscle biopsy can detect axon terminal anterior and endplates. abnormal.
When there is malignant anemia, the proliferation of giant red blood cells in the bone marrow predominates, and the surrounding blood is hyperchromic giant red blood cell anemia, with nucleated red blood cells.
Prevention
Subacute combined degeneration prevention
Reasonable diet to prevent vitamin B1 and B12 deficiency, prevention of gastric malabsorption and pernicious anemia. Pay attention to the usual diet, pay attention to living habits, mainly based on light food.
Complication
Subacute combined degeneration complications Complications anemia
With the degree of vitamin B12 deficiency, and the patient's own immunological pathogenesis, the severity of the disease is different, so the symptoms and signs are diverse, such as various manifestations of pernicious anemia, can also be considered as a complication of the disease.
Symptom
Subacute combined degeneration symptoms Common symptoms Dizziness constipation Easy to fall Reflexes Aizhi ataxia Drowsiness Dementia
Both men and women can be involved, usually starting from middle age (40 to 60 years old), the condition is gradually worsening, mainly the spinal cord, corticospinal and peripheral nerve damage, but also optic nerve damage, may have mental symptoms and brain Symptoms, but less.
The most common symptoms first appear are generalized fatigue and symmetry of the distal part of the limb, such as tingling, burning, chills, etc., especially in the lower limbs. The abnormal feeling can extend up to the trunk and produce a band-like sensation in the chest and abdomen. When the spinal cord lateral degeneration occurs, the two lower extremities are weak or paralyzed, the muscle tension is increased, the sacral reflex is hyperthyroidism and the pyramidal tract sign is positive. When the posterior cord is degenerated, the lower limbs vibrate and position sense are deeper, and the deep sensory disturbance produces different degrees. Lower limb ataxia, awkward limb movements, unstable gait, easy to fall, more obvious when closing eyes or walking in darkness, decreased or disappeared muscle tone and tendon reflexes, sphincter symptoms in the late stage, gloves or The shallow sensation of the distribution of the sock-like distribution is reduced or disappeared, the tenderness of the gastrocnemius muscle and the weakness of the extremities, and the severity of the clinical signs depends on the relative severity of the influence of the lesion on the peripheral nerve, the posterior cord and the pyramidal tract.
In addition to the dark spots of optic neuropathy, visual acuity or blindness, the cranial nerves are generally unaffected, and about 5% of patients have optic nerve damage.
A small number of patients have suspicion, delusions, mania, late sleepiness, delirium, dementia, Korsakoff syndrome, or severe depression, and even mental symptoms such as depression.
Some patients have gastric acid deficiency, some patients have mild or severe anemia, occasionally the surrounding blood is normal, but there are malignant anemia in the bone marrow, which may have mild glossitis, palpitation, dizziness, weakness of both lower limbs and mild edema. When there is a gastrointestinal disease, there is loss of appetite, constipation or diarrhea.
In the early treatment, most of the neurological symptoms were restored, and those with limb paralysis for more than two years were less effective.
Examine
Subacute combined degeneration
1. Blood and bone marrow: Most of the anemia is more serious, it is a large cell positive pigmentation anemia, MCV is increased, MCHC is normal, neutrophil nucleus is too much, bone marrow erythrocyte proliferation is significant, there are giant red blood cells, grain: red ratio Down to 1:1, both blood and bone marrow suggest megaloblastic anemia.
2. Analysis of gastric juice: rapid histamine test, gastric juice analysis can be found to be anti-histamine gastric acid deficiency, antibody can be detected in some patients with anti-gastric cell antibody or IF antibody.
3. Schiling test: oral radionuclide 57Co labeled vitamin B12, determination of its content in urine, stool, is very meaningful for determining the cause of vitamin B12 deficiency, is a more sensitive detection method, the normal person absorption is 62% 82%, urinary discharge is 7% to 10%.
4. Determination of serum vitamin B12: normal content is 140 ~ 900 ng / L, when less than 100 ng / L, there is a diagnostic significance.
5. Determination of urinary methylmalonic acid: Due to the deficiency of vitamin B12, methylmalonyl CoA can not be converted into succinyl-CoA, and the content of methylmalonic acid in urine is increased, so the determination of methylmalonic acid in urine can be Further support for the diagnosis of the disease, there is currently no simple and accurate measurement method.
6. There is no abnormality in cerebrospinal fluid examination.
7. Spinal cord CT, MRI examination: the lesion area can show swelling of the myelin sheath, break and sign.
8. Muscle biopsy can detect abnormalities in the axon terminal and terminal plates.
Diagnosis
Subacute combined degeneration diagnosis
diagnosis
According to middle-aged onset, subacute or chronic course, there are symptoms and signs of typical spinal cord injury with psychiatric symptoms, mental decline, peripheral nerve and optic nerve damage, low serum vitamin B12 levels, gastric malabsorption and anemia changes, combined Schilling test and other auxiliary examinations are generally not difficult to make a diagnosis, but the diagnosis is difficult in the early stage of the disease, especially when the neurological symptoms are earlier than anemia.
Differential diagnosis
1. Spinal cord compression: early symptoms of nerve root irritation can occur, and last for a long time, the sensory disturbance is on the ascending development, generally starting from one side, the spinal cord and the lateral cord can be affected, which is represented by Brown-Sequard synthesis. In the late stage, there was transverse damage, sphincter dysfunction, no brain and optic nerve damage, elevated cerebrospinal fluid protein, spinal MRI angiography can help diagnose, common causes are intramedullary, external tumor, cervical osteoarthrosis, cervical spinal stenosis.
2. Multiple sclerosis: acute onset, obvious history of remission and recurrence, the first symptoms are mostly vision loss or diplopia, nystagmus, cerebellar sign, pyramidal tract sign, posterior dysfunction, no symmetry The manifestations of peripheral nerve damage, cerebrospinal fluid examination, evoked potentials, CT and MRI are helpful in diagnosis.
3. Peripheral neuropathy: peripheral neuropathy caused by poisoning, inflammation, nutritional deficiencies, vascular diseases, etc. may have distal sensory disturbances of the extremities, similar to peripheral nerve damage in subacute combined degeneration of the spinal cord, but generally no change in posterior or lateral cords. No vitamin B12 deficiency, combined with medical history, is not difficult to identify.
4. Spinal cord sputum: the posterior root and posterior cord of the spinal cord are involved, and there is degeneration and atrophy. The A-Luo hole is a typical sign. Combined with the history of smelting, the seropositive syphilis can be identified.
