The neurological paraneoplastic syndrome can involve any part of the nervous system and therefore, there will be many clinical manifestations of neurological paraneoplastic syndrome in the clinical setting. It can involve the central nervous system to produce diffuse gray matter encephalopathy, cerebellar degeneration, carcinomatous myelopathy and limbic system encephalitis, etc. It can involve the peripheral nervous system to produce polyneuropathy, complex mononeuritis and involve the neuromuscular junction to produce myasthenia gravis, Lambert-Eaton myasthenia syndrome, neuromuscular ankylosis and dermatomyositis/ polymyositis, etc. Paraneoplastic syndromes can involve only a single neural or muscle structure (e.g., Purkinje cells in the cerebellum, cholinergic synapses in the muscle) and present with a single clinical manifestation, the former as cerebellar ataxia and the latter as myasthenia gravis syndrome. The clinical symptoms produced by the neurological paraneoplastic syndrome often do not appear alone, but overlap with those produced by other neurological paraneoplastic syndromes. Sometimes the clinical manifestation is a single neurological damage, but the pathological changes are more extensive, although the symptoms of one of the structural damages are still the main prominent manifestation. The etiology and pathogenesis of paraneoplastic syndrome are not well understood. It was previously generally believed that it may be due to the secretion of certain substances by the carcinoma that directly damage the nervous system, such as the secretion of hormone-like substances (hormone-likesubstances) and cytokines (cytokines). Tumor-produced hormone-like substances can bow/initiate hypercalcemia, weakness, and behavioral abnormalities. Cushing’sSyndrome and behavioral abnormalities caused by ectopic ACTH produced by tumors. Interleukin-1 and tumor necrosis factor can cause muscle atrophy and weakness. It is now believed that immune factors are certainly very important in the pathogenesis. Tumor antigens cause an antigenic antibody response to the tumor itself, producing large amounts of antibodies. This antibody can cross-immune reaction with some similar antigenic components in the nervous system. This cross-immune reaction both inhibits the growth of the tumor, making it smaller or slower, but also damages the nervous system, causing neurological dysfunction. For example, about 2/3 of patients with Lambert-Eaton myasthenia gravis syndrome also have small cell lung cancer in combination, because the specific immunoglobulin IgC produced by the tumor reacts immunologically with the calcium channels of small cell lung cancer cells, as well as with the calcium channels at the cholinergic synapses. It prevents the calcium inward flow when the action potential reaches the synapse, which reduces the release of acetylcholine and produces a cluster of muscle weakness symptoms. gG is removed from the serum of patients with Lambert-Eaton muscle weakness syndrome after plasma replacement, and the patients’ symptoms are restored, and direct inoculation of experimental animals with the replaced plasma can also cause muscle weakness. Certain antibodies can be found in the serum and cerebrospinal fluid of patients with paraneoplastic syndrome that are associated with cancerous tumors or damaged nerves. The detection of such antibodies in laboratory tests may indicate the presence of a certain tumor. For example, anti-Yo antibodies (anti-Y0-antib0dy) are associated with paraneoplastic cerebellar degeneration and certain gynecologic carcinomas, and anti-Hu antibodies (anti-Hu-antibody)y are associated with paraneoplastic sensory neuronopathy, encephalomyelitis and small cell lung cancer. In addition, in some neurobiochemical studies, it has been found that certain proteins in neural tissues have homology with antigens of tumor tissues, such as sensory neuronopathy or encephalomyelitis antigens are homologous with Drosophila growth antigens, and genes related to myasthenia gravis are homologous with the beta subunit of calcium channels. However, not all cancers in paraneoplastic syndrome produce antibodies, so the question of how the immune response occurs in many cancers is not clear. The clinical manifestations of CNS damage in paraneoplastic syndrome mainly depend on the sites of CNS involvement, including cerebral hemisphere, limbic lobe, cerebellum, brainstem and spinal cord, and their clinical manifestations have their own characteristics. Diffusedpolioencephalopathy is common in bronchopulmonary cancer such as Hodgkin’s disease. According to statistics, about 40% of patients with advanced cancer develop psychiatric symptoms, some of which may be caused by the metastasis of cancer to the brain, but most of them belong to this category. Clinical manifestations: Patients present with dementia: at the beginning, patients present with near memory loss, emotional instability, depression, anxiety and agitation, symptoms are progressively aggravated and gradually develop into dementia: the duration of the disease is 5-20 months, usually not more than 2 years. Laboratory examination reveals that the content of cells and proteins in the cerebrospinal fluid of patients can be mildly increased, and no metastatic cancer cells are found in cytological examination. Pathological examination reveals that the patient’s lesions are mainly in the cerebral cortex, especially in the gray matter where there exists by extensive neuronal loss. In addition, lymphocytic infiltration was seen around the blood vessels of the cerebral cortex. Second, paraneoplastic limbic system encephalitis (pamneoplasrticimbiccencephaLitis) In some tumors such as lung cancer and ovarian cancer, a distal effect can occur, manifested by inflammatory and neurodegenerative changes in the gray matter region of the central nervous system. When the limbic system is predominantly involved, the clinical presentation is an amnesic syndrome. The etiology is unknown, but anti-neurogenic autoantibodies have been found to be involved in other paraneoplastic neurological syndromes. The clinical manifestations of amnesic syndrome due to paraneoplastic limbic system encephalitis can be resting, progressive or recurrent in presentation. The clinical presentation of patients is characterized by severe impairment of proximal memory and a marked decrease in the ability to learn new things: distant memory impairment is generally milder and the ability to record is not affected. Fictitiousness may be present in some cases, anxiety and depression usually appear early in the emergence of the syndrome, and hallucinations as well as partial or generalized seizures can be minimally present. In many cases, the amnesic syndrome progresses progressively until dementia develops. Laboratory tests reveal a small amount of mononucleosis in the cerebrospinal fluid and moderate protein elevation. Serologic tests sometimes reveal an antibody against the neuronal Ma2 protein, and the EEG sometimes shows diffuse slow waves or the presence of slow waves or spikes in both temporal lobes. abnormal signal images can be seen on MRI in structures such as the middle temporal lobe, hippocampus, cingulate gyrus, insula, and amygdala. Paraneoplastic limbic system encephalitis is most often associated with the development of small cell lung cancer, and its syndrome usually precedes the detection of the lung cancer. Histological examination reveals neuronal loss, reactive neurogliosis, microglial cell proliferation, and infiltration of peripheral vascular lymphocytes in sets of aggregates in the cerebral cortex. The gray matter in the hippocampus, cingulate gyrus, pyriform cortex, inferior frontal lobe, insula, and amygdala were the most common sites of damage. Amnesic syndrome due to paraneoplastic limbic encephalitis is often associated with symptoms of damage to other sites, depending on the part of the nervous system other than the limbic system affected, such as damage to the cerebellum, medulla oblongata, pyramidal tract, and peripheral nerves. There is no specific treatment available, so treatment of the primary cause is particularly important. Korsakoff syndrome due to vitamin B1 deficiency should be given special attention because cancer patients are often accompanied by severe nutritional deficiencies, and treatment with large amounts of vitamin B may improve the worsening course of the amnesic syndrome. Paraneoplastic cerebellar degeneration (paraneoplaStiCcerebellardegeneratiOn) is often seen as a distal symptom of some tumors, especially in patients with small cell lung cancer, ovarian cancer, Hodgkin’s disease, and breast cancer. Paraneoplastic degeneration diffusely affects the earthworms and hemispheres of the cerebellum. The pathogenesis is the presence of antibodies that cross-react with the tumor cells and the cerebellar Purkinje cells in the patient. The presence of autoantibodies, called anti-Yo antibodies, in the serum and CSF of some patients with gynecologic tumors combined with cerebellar degeneration has been reported. Anti-Y. antibodies are polyclonal IgG antibodies that specifically immunoreact with cerebellar degeneration-related antigens (CDR) in the plasma of Purkinje cells in the cerebellar cortex with the participation of complement, and also react with (CDR) in tumor cells. There are two types of CDR, one with a molecular weight of 34 kDa and the other with a molecular weight of 62 kDa. Anti-Y. antibodies are generally not present in patients with other tumors combined with cerebellar degeneration, but only two reports of anti-Y. antibodies positive in non-Hodgkin’s lymphoma combined with cerebellar degeneration have been seen; H. In breast cancer and ovarian cancer without the presence of cerebellar degeneration, such antibodies do not appear. This antibody is also not present in cerebellar degeneration without the presence of a tumor. Therefore, the detection of anti-Yo antibodies in patients with subacute cerebellar degeneration, for example, suggests the presence of a gynecologic carcinoma. Anti-Hu antibodies can be detected in patients with small cell lung cancer combined with paraneoplastic syndrome. Because anti-Hu antibodies are synthesized in the brain, the titer of such antibodies is higher in CSF than in serum. The specificity of anti-Hu antibody is lower than that of anti-Yo antibody because anti-Hu antibody can be found in neuroblastoma, breast cancer and prostate cancer, in addition to small cell lung cancer. In addition, anti-Hu antibody positivity can be found in other clinical types of paraneoplastic syndromes, such as encephalomyelitis, limbic encephalitis, brainstem encephalitis, myelitis, subacute sensory neuronopathy, anterior horn cell degeneration, and Lambert-Eaton syndrome. Therefore, the presence of anti-Hu antibodies has yet to be specifically analyzed for its clinical significance. Symptoms of cerebellar damage can appear before or after tumor symptoms and progress progressively over several months. Although the symptoms of cerebellar damage usually tend to worsen progressively, the course of the disease can also be stable, and remission of cerebellar damage has been reported with treatment of the primary tumor. Gait and limb ataxia are characteristic of cerebellar damage, and dysarthria is present in many cases. Ataxia of the limbs can be asymmetrical, and nystagmus is less common. Paraneoplastic damage that involves other parts of the nervous system may also produce speech difficulties, dementia, memory impairment, pyramidal fasciculations, or other neuropathy. Anti-Purkinje cell antibodies such as anti-Y. antibodies (ovarian and breast tumors), or anti-Tr antibodies (Hodgkin’s disease), and anti-nuclear antibodies such as anti-Hu (small cell lung cancer) and anti-Ri (breast cancer) are sometimes detected in the blood. moderate lymphocytosis and elevated protein may be present in the CSF.
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