demyelinating disease demyelinating disease a demyelinating disease is any disease of the nervous system in which the myelin sheath of neurons is damaged. this damage impairs the conduction of signals in the affected nerves. in turn, the reduction in conduction ability causes deficiency in sensation, movement, cognition, or other functions depending on which nerves are involved. demyelinating diseasephotomicrograph of a demyelinating ms-lesion: immunohistochemical staining for cd68 highlights numerous macrophages (brown). original magnification 10×.specialtyneurology demyelinating diseases can be caused by genetics, infectious agents, autoimmune reactions, and other unknown factors. proposed causes for demyelination include genetics and environmental factors such as being triggered by a viral infection or chemical exposure. organophosphate poisoning by commercial insecticides such as sheep dip, weed killers, and flea treatment preparations for pets, can also result in nerve demyelination. chronic neuroleptic exposure may cause demyelination.vitamin b12 deficiency may also result in dysmyelination. demyelinating diseases are traditionally classified in two kinds: demyelinating myelinoclastic diseases and demyelinating leukodystrophic diseases. in the first group, a normal and healthy myelin is destroyed by a toxic, chemical, or autoimmune substance. in the second group, myelin is abnormal and degenerates. the second group was denominated dysmyelinating diseases by poser. in the most well known example of demyelinating disease, multiple sclerosis, evidence has shown that the body's own immune system is at least partially responsible. acquired immune system cells called t-cells are known to be present at the site of lesions. other immune-system cells called macrophages (and possibly mast cells) also contribute to the damage. signs and symptoms symptoms and signs that present in demyelinating diseases are different for each condition. these symptoms and signs can present in a person with a demyelinating disease: blurred double vision (diplopia) ataxia clonus dysarthria fatigue clumsiness hand paralysis hemiparesis genital anaesthesia incoordination paresthesias ocular paralysis (cranial nerve palsy) impaired muscle coordination weakness (muscle) loss of sensation impaired vision unsteady gait spastic paraparesis incontinence hearing problems speech problems evolutionary considerations the role of prolonged cortical myelination in human evolution has been implicated as a contributing factor in some cases of demyelinating disease. unlike other primates, humans exhibit a unique pattern of postpubertal myelination, which may contribute to the development of psychiatric disorders and neurodegenerative diseases that present in early adulthood and beyond. the extended period of cortical myelination in humans may allow greater opportunities for disruption in myelination, resulting in the onset of demyelinating disease. furthermore, humans have significantly greater prefrontal white matter volume than other primate species, which implies greater myelin density. increased myelin density in humans as a result of a prolonged myelination may, therefore, structure risk for myelin degeneration and dysfunction. evolutionary considerations for the role of prolonged cortical myelination as a risk factor for demyelinating disease are particularly pertinent given that genetics and autoimmune deficiency hypotheses fail to explain many cases of demyelinating disease. as has been argued, diseases such as multiple sclerosis cannot be accounted for by autoimmune deficiency alone, but strongly imply the influence of flawed developmental processes in disease pathogenesis. therefore, the role of the human-specific prolonged period of cortical myelination is an important evolutionary consideration in the pathogenesis of demyelinating disease. diagnosis various methods/techniques are used to diagnose demyelinating diseases: exclusion of other conditions that have overlapping symptoms magnetic resonance imaging (mri) is a medical imaging technique used in radiology to visualize internal structures of the body in detail. mri makes use of the property of nuclear magnetic resonance (nmr) to image nuclei of atoms inside the body. this method is reliable because mris assess changes in proton density. "spots" can occur as a result of changes in brain water content.: 113 evoked potential is an electrical potential recorded from the nervous system following the presentation of a stimulus as detected by electroencephalography (eeg), electromyography (emg), or other electrophysiological recording method.: 117 cerebrospinal fluid analysis (csf) can be extremely beneficial in the diagnosis of central nervous system infections. a csf culture examination may yield the microorganism that caused the infection. quantitative proton magnetic resonance spectroscopy (mrs) is a noninvasive analytical technique that has been used to study metabolic changes in brain tumors, strokes, seizure disorders, alzheimer's disease, depression, and other diseases affecting the brain. it has also been used to study the metabolism of other organs such as muscles.: 309 diagnostic criteria refers to a specific combination of signs, symptoms, and test results that the clinician uses in an attempt to determine the correct diagnosis.: 320 fluid-attenuated inversion recovery (flair) uses a pulse sequence to suppress cerebrospinal fluid and show lesions more clearly, and is used for example in multiple sclerosis evaluation. types demyelinating diseases can be divided in those affecting the central nervous system (cns) and those affecting the peripheral nervous system (pns). they can also be classified by the presence or absence of inflammation. finally, a division may be made based on the underlying cause of demyelination: the disease process can be demyelinating myelinoclastic, wherein myelin is destroyed; or dysmyelinating leukodystrophic, wherein myelin is abnormal and degenerative. cns the demyelinating disorders of the central nervous system include: myelinoclastic or demyelinating disorders: typical forms of multiple sclerosis neuromyelitis optica, or devic's disease idiopathic inflammatory demyelinating diseases leukodystrophic or dysmyelinating disorders: cns neuropathies such as those produced by vitamin b12 deficiency central pontine myelinolysis myelopathies such as tabes dorsalis (syphilitic myelopathy) leukoencephalopathies such as progressive multifocal leukoencephalopathy leukodystrophies the myelinoclastic disorders are typically associated with symptoms such as optic neuritis and transverse myelitis, because the demyelinating inflammation can affect the optic nerve or spinal cord. many are idiopathic. both myelinoclastic and leukodystrophic modes of disease may result in lesional demyelinations of the central nervous system. pns guillain–barré syndrome – demyelination the demyelinating diseases of the peripheral nervous system include: guillain–barré syndrome and its chronic counterpart, chronic inflammatory demyelinating polyneuropathy anti-mag peripheral neuropathy charcot–marie–tooth disease and its counterpart hereditary neuropathy with liability to pressure palsy copper deficiency-associated conditions (peripheral neuropathy, myelopathy, and rarely optic neuropathy) progressive inflammatory neuropathy treatment