Demyelinating disease

Demyelinating disease
Photomicrograph of a demyelinating MS-Lesion. Immunohistochemical staining for CD68 highlights numerous macrophages (brown). Original magnification 10×.
Classification and external resources
Specialty neurology
ICD-10 G35-G37, G61.0
ICD-9-CM 340-341, 357.0
DiseasesDB 17472
MeSH D003711

A demyelinating disease is any disease of the nervous system in which the myelin sheath of neurons is damaged.[1] 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.

Some demyelinating diseases are caused by genetics, some by infectious agents, some by autoimmune reactions, and some by unknown factors. Organophosphates, a class of chemicals which are the active ingredients in commercial insecticides such as sheep dip, weed-killers, and flea treatment preparations for pets, etc., will also demyelinate nerves. Neuroleptics can also cause demyelination.[2]

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.[3] The second group was denominated dysmyelinating diseases by Poser[4]

In the most known example, multiple sclerosis, there is good evidence 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 as well) also contribute to the damage.[5]

Some demyelinating diseases are caused by genetics, some by infectious agents, some by autoimmune reactions, some by exposure to chemical agents, and some by unknown factors.

Vitamin B12 deficiency can cause demyelination.

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 opportunity for disruption in myelination, resulting in the onset of demyelinating disease.[6] Furthermore, it has been noted that humans have significantly greater prefrontal white matter volume than other primate species, which implies greater myelin density.[7] 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.[8] Therefore, the role of the human-specific prolonged period of cortical myelination is an important evolutionary consideration in the pathogenesis of demyelinating disease.

Signs and symptoms

Symptoms that present in demyelinating diseases are different for each condition. Below is a list of symptoms that can present in a person with a demyelinating disease.:[9]

  • Ocular paralysis
  • Impaired muscle coordination
  • Weakness (muscle)
  • Loss of sensation
  • Impaired vision
  • Neurological symptoms
  • Unsteady gait
  • Spastic paraparesis
  • Incontinence
  • Hearing problems
  • Speech problems

Diagnosis

Below are various methods/techniques used to diagnose demyelinating diseases.

Treatment

Treatment typically involves improving the patient's quality of life. This is accomplished through the management of symptoms or slowing the rate of demyelination. Treatment can include medication, lifestyle changes (i.e. quit smoking, adjusting daily schedules to include rest periods and dietary changes), counselling, relaxation, physical exercise, patient education and, in some cases, deep brain thalamic stimulation (in the case of tremors).[10]:227–248 The progressive phase of MS appears driven by the innate immune system, which will directly contribute to the neurodegenerative changes that occur in progressive MS. Until now, there are no therapies that specifically target innate immune cells in MS. As the role of innate immunity in MS becomes better defined, it may be possible to better treat MS by targeting the innate immune system.[11]

Treatments are patient-specific and depend on the symptoms that present with the disorder, as well as the progression of the condition.

Prognosis

Prognosis depends on the condition itself. Some conditions such as multiple sclerosis depend on the subtype of the disease and various attributes of the patient such as age, sex, initial symptoms and the degree of disability the patient experiences.[12] Life expectancy in Multiple sclerosis patients is 5 to 10 years lower than unaffected people.[13] MS is an inflammatory demyelinating disease of the central nervous system (CNS) that develops in genetically susceptible individuals after exposure to unknown environmental trigger(s). The bases for MS are unknown but are strongly suspected to involve immune reactions against autoantigens, particularly myelin proteins. The most accepted hypothesis is that dialogue between T-cell receptors and myelin antigens leads to an immune attack on the myelin-oligodendrocyte complex. These interactions between active T cells and myelin antigens provoke a massive destructive inflammatory response and promotes continuing proliferation of T and B cells and macrophage activation, which sustains secretion of inflammatory mediators.[14] Other conditions such as central pontine myelinolysis have about a third of patients recover and the other two thirds experience varying degrees of disability.[15] There are cases, such as transverse myelitis where the patient can begin recovery as early as 2 to 12 weeks after the onset of the condition.

Epidemiology

Incidence of demyelinating diseases vary from disorder to disorder. Some conditions, such as Tabes dorsalis appear predominantly in males and begins in mid-life. Optic neuritis on the other hand, occurs preferentially in females typically between the ages of 30 and 35.[16] Other conditions such as multiple sclerosis vary in prevalence depending on the country and population.[17] This condition can appear in children as well as adults.[13]

Types

Demyelinating diseases can be divided in those affecting the central nervous system and those presents in the peripheral nervous system, presenting different demyelination conditions. They can also be divided by other criteria in inflammatory and non-inflammatory, according to the presence or lack of inflammation, and finally, a division can also be made depending on the underlying reason for demyelination in myelinoclastic (myelin is attacked by an external substance) and leukodystrophic (myelin degenerates without attacks)

Demyelinating disorders of the CNS

The demyelinating disorders of the central nervous system include:

These disorders are normally associated also with the conditions Optic neuritis and Transverse myelitis, which are inflammatory conditions, because inflammation and demyelination are frequently associated. Some of them are idiopathic and for some others the cause has been found, like some cases of neuromyelitis optica.

Demyelinating diseases of the peripheral nervous system

The demyelinating diseases of the peripheral nervous system include:

Research

Research is being conducted in a variety of very specific areas. The focus of this research is aimed at gaining more insight into how demyelinating disorders affect the central nervous system and peripheral nervous system,[18][19][20][21][22] how they develop and how these disorders are affected by various external inputs[23][24][25][26][27] . Much of the research is targeted towards learning about the mechanisms by which these disorders function in an attempt to develop therapies and treatments for individuals affected by these conditions.

Insights

Currently it is believed that N-cadherin plays a role in the myelination process. Experimentation has shown that N-cadherin plays an important role in producing a remyelination-facilitating environment.[18] It has been shown in animal models that there is a direct correlation between the amount of myelin debris present and the degree of Inflammation observed.[19]

Effects of environmental inputs

Experimentation has shown that manipulating the levels of thyroid hormone can be considered as a strategy to promote remyelination and prevent irreversible damage in Multiple sclerosis patients.[21] N-cadherin agonists have been identified and observed to stimulate neurite growth and cell migration, key aspects of promoting axon growth and remyelination after injury or disease.[23] It has been shown that intranasal administration of aTf (apotransferrin) can protect myelin and induce remyelination.[25]

Much of the research referenced in this section has been conducted in 2012 and represents very new information about demyelinating diseases and potential therapies for them.

In other animals

Demyelinating diseases/disorders have been found worldwide in various animals. Some of these animals include mice, pigs, cattle, hamsters, rats, sheep, Siamese kittens, and a number of dog breeds (including Chow Chow, Springer Spaniel, Dalmatian, Samoyed, Golden Retriever, Lurcher, Bernese Mountain Dog, Vizsla, Weimaraner, Australian Silky Terrier, and mixed breeds).[28][29]

Another notable animal found able to contract a demyelinating disease is the northern fur seal. Ziggy Star, a female northern fur seal, was treated at The Marine Mammal Center beginning in March 2014 [30] and was noted as the first reported case of such disease in a marine mammal. She was later transported to Mystic Aquarium & Institute for Exploration for lifelong care as an ambassador to the public.[31]

See also

References

  1. ↑ "demyelinating disease" at Dorland's Medical Dictionary
  2. ↑ Konopaske GT; Dorph-Petersen KA; Sweet RA; et al. (April 2008). "Effect of chronic antipsychotic exposure on astrocyte and oligodendrocyte numbers in macaque monkeys". Biol. Psychiatry. 63 (8): 759–65. doi:10.1016/j.biopsych.2007.08.018. PMC 2386415Freely accessible. PMID 17945195.
  3. ↑ Fernández O.; Fernández V.E.; Guerrero M. (2015). "Demyelinating diseases of the central nervous system". Medicine. 11 (77): 4601–4609. doi:10.1016/j.med.2015.04.001.
  4. ↑ Poser C. M. (1961). "Leukodystrophy and the Concept of Dysmyelination". Arch Neurol. 4 (3): 323–332. doi:10.1001/archneur.1961.00450090089013.
  5. ↑ Laetoli (January 2008). "Demyelination".
  6. ↑ Miller Daniel J (2012). "Prolonged Myelination in Human Neocortical Evolution". PNAS. 109 (41): 16480–16485. doi:10.1073/pnas.1117943109.
  7. ↑ Schoenemann, Thomas P., Sheehan Michael J., Glotzer L. Daniel; Sheehan; Glotzer (2005). "Prefrontal White Matter Volume Is Disproportionately Larger in Humans than in Other Primates". Nature Neuroscience. 8 (2): 242–52. doi:10.1038/nn1394. PMID 15665874.
  8. ↑ Chaudhuri Abhijit (2013). "Multiple Sclerosis Is Primarily a Neurodegenerative Disease". J Neural Transm. 120: 1463–466. doi:10.1007/s00702-013-1080-3.
  9. ↑ "Symptoms of Demyelinating Disorders - Right Diagnosis." Right Diagnosis. Right Diagnosis, 01 Feb 2012. Web. 24 Sep 2012
  10. 1 2 3 4 5 6 7 Freedman, Mark S (2005). Advances in Neurology Volume 98: Multiple Sclerosis and Demyelinating Diseases. Philadelphia: Lippincott Williams & Wilkins. p. 112. ISBN 0781751705.
  11. ↑ Mayo, Lior; Quintana, Francisco J.; Weiner, Howard L. (21 June 2012). "The Innate Immune System in Demyelinating Disease". Immunological Reviews. 248 (1): 170–87. doi:10.1111/j.1600-065X.2012.01135.x. PMC 3383669Freely accessible. PMID 22725961.
  12. ↑ Weinshenker BG (1994). "Natural history of multiple sclerosis". Ann. Neurol. 36 (Suppl): S6–11. doi:10.1002/ana.410360704. PMID 8017890.
  13. 1 2 Compston A, Coles A (October 2008). "Multiple sclerosis". Lancet. 372 (9648): 1502–17. doi:10.1016/S0140-6736(08)61620-7. PMID 18970977.
  14. ↑ Minegar, Alireza. "Blood-Brain Barrier Disruption in Multiple Sclerosis". Sage Journals. Retrieved October 28, 2012.
  15. ↑ Abbott R, Silber E, Felber J, Ekpo E (October 2005). "Osmotic demyelination syndrome". BMJ. 331 (7520): 829–30. doi:10.1136/bmj.331.7520.829. PMC 1246086Freely accessible. PMID 16210283.
  16. ↑ Rodriguez M, Siva A, Cross SA, O'Brien PC, Kurland LT (1995). "Optic neuritis: a population-based study in Olmsted County, Minnesota". Neurology. 45 (2): 244–50. doi:10.1212/WNL.45.2.244. PMID 7854520.
  17. ↑ Rosati G (April 2001). "The prevalence of multiple sclerosis in the world: an update". Neurol. Sci. 22 (2): 117–39. doi:10.1007/s100720170011. PMID 11603614.
  18. 1 2 Hochmeister, S.; Romauch, M; Bauer, J; Seifert-Held, T; Weissert, R; Linington, C; Hurtung, H.P.; Fazekas, F; Storch, M.K. (2012). "Re-expression of n-cadherin in remyelinating lesions of experimental inflammatory demyelination". Experimental Neurology. 237 (1): 70–77. doi:10.1016/j.expneurol.2012.06.010. PMID 22735489.
  19. 1 2 Clarner, T.; Diederichs, F.; Berger, K.; Denecke, B.; Gan, L.; Van Der Valk, P.; Beyer, C.; Amor, S.; Kipp, M. (2012). "myelin debris regulates inflammatory responses in an experimental demyelination animal model and multiple sclerosis lesions". GLIA. 60 (10): 1468–1480. doi:10.1002/glia.22367. PMID 22689449.
  20. ↑ Newcombe, J.; Eriksson, B.; Ottervald, J.; Yang, Y.; Franzen, B. (2005). "Extraction and proteomic analysis of proteins from normal and multiple sclerosis postmortem brain". Journal of Chromatography B. 815: 119–202. doi:10.1016/j.jchromb.2004.10.073.
  21. 1 2 Silverstroff, L.; Batucci, S.; Pasquini, J.; Franco, P. (2012). "Cuprizone-induced demyelination in the rat cerebral cortex and thyroid hormone effects on cortical remyelination". Experimental Neurology. 235 (1): 357–367. doi:10.1016/j.expneurol.2012.02.018. PMID 22421533.
  22. ↑ Palumbo, S.; Toscano, C.D.; Parente, L.; Weigert, R.; Bosetti, F. (2012). "The cyclooxygenase-2 pathway via the pge₂ ep2 receptor contributes to oligodendrocytes apoptosis in cuprizone-induced demyelination". Journal of Neurochemistry. 121 (3): 418–427. doi:10.1111/j.1471-4159.2011.07363.x. PMC 3220805Freely accessible. PMID 21699540.
  23. 1 2 Burden-Gulley, S.M.; Gates, T.J.; Craig, S.E.L.; Gupta, M.; Brady-Kalnay, S.M. (2010). "Stimulation of n-cadherin-dependent neurite outgrowth by small molecule peptide mimetic agonists of the n-cadherin hav motif". Peptides. 31 (5): 842–849. doi:10.1016/j.peptides.2010.02.002. PMID 20153391.
  24. ↑ Sherafat, M.A.; Heibatollahi, M.; Mongabadi, S.; Moradi, F.; Javan, M.; Ahmadiani, A. (2012). "Electromagnetic field stimulation potentiates endogenous myelin repair by recruiting subventricular neural stem cells in an experimental model of white matter demyelination". Journal of Molecular Neuroscience. 48 (1): 144–153. doi:10.1007/s12031-012-9791-8. PMID 22588976.
  25. 1 2 Clausi, M.G.; Paez, P.M.; Campagnoni, A.T.; Pasquini, L.A.; Pasquini, J.M.; Ahmadiani, A. (2012). "Intranasal administration of atf protects and repairs the neonatal white matter after a cerebral hypoxic-ischemic event". GLIA. 60 (10): 1540–1554. doi:10.1002/glia.22374. PMID 22736466.
  26. ↑ Gasperini, C.; Ruggieri, S. (2012). "Development of oral agent in the treatment of multiple sclerosis- how the first available oral therapy, fingolimod will change therapeutic paradigm approach". Drug Design, Development and Therapy. 6: 175–186. doi:10.2147/DDDT.S8927.
  27. ↑ Ransohoff, R.M.; Hower, C.L.; Rodriquez, M. (2005). "Growth factor treatment of demyelinating disease- at last, a leap into the light". Trends in Immunology. 23 (11): 512–516. doi:10.1016/S1471-4906(02)02321-9. PMID 12401395.
  28. ↑ Merck Sharp; Dohme Corp (2011). "The Merck Veterinary Manual – Demyelinating Disorders: Introduction". Merck Veterinary Manual. Retrieved 2012-10-30.
  29. ↑ "Johnson RT. DEMYELINATING DISEASES. In: Institute of Medicine (US) Forum on Microbial Threats; Knobler SL, O'Connor S, Lemon SM, et al., editors. The Infectious Etiology of Chronic Diseases: Defining the Relationship, Enhancing the Research, and Mitigating the Effects: Workshop Summary. Washington (DC): National Academies Press (US)". NCBI. 2004. Retrieved 2012-10-30.
  30. ↑ http://wtnh.com/2014/12/22/ziggy-star-at-mystic-aquarium/
  31. ↑ "Ziggy Star has a Neurologic Condition". The Marine Mammal Center. Retrieved 2 February 2014.
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