- Mild cognitive impairment
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Mild cognitive impairment Classification and external resources ICD-10 F06.7 ICD-9 331.83 Mild cognitive impairment (MCI, also known as incipient dementia, or isolated memory impairment) is a brain-function syndrome involving the onset and evolution of cognitive impairments beyond those expected based on the age and education of the individual, but which are not significant enough to interfere with their daily activities.[1] It is often found to be a transitional stage between normal aging and dementia. Although MCI can present with a variety of symptoms, when memory loss is the predominant symptom it is termed "amnestic MCI" and is frequently seen as a prodromal stage of Alzheimer's disease.[2] Studies suggest that these individuals tend to progress to probable Alzheimer’s disease at a rate of approximately 10% to 15% per year.[2]
Additionally, when individuals have impairments in domains other than memory it is classified as non-amnestic single- or multiple-domain MCI and these individuals are believed to be more likely to convert to other dementias (e.g. dementia with Lewy bodies).[3] However, some instances of MCI may simply remain stable over time or even remit. Causation of the syndrome in and of itself remains unknown, as therefore do prevention and treatment.
Contents
Diagnosis
The diagnosis of MCI requires considerable clinical judgement,[2] and as such a comprehensive clinical assessment including clinical observation, neuroimaging, blood tests and neuropsychological testing are best in order to rule out an alternate diagnosis. A similar assessment is usually given for diagnosis of Alzheimer's disease.
MCI is diagnosed when there is:[4]
- Evidence of memory impairment
- Preservation of general cognitive and functional abilities
- Absence of diagnosed dementia
Neuropathology
There is evidence suggesting that while amnestic MCI patients may not meet neuropathologic criteria for Alzheimer's disease, patients may be in a transitional stage of evolving Alzheimer's disease; patients in this hypothesized transitional stage demonstrated diffuse amyloid in the neocortex and frequent neurofibrillary tangles in the medial temporal lobe.[5]
There is emerging evidence that magnetic resonance imaging can observe deterioration, including progressive loss of gray matter in the brain, from mild cognitive impairment to full-blown Alzheimer disease.[6] A technique known as PiB PET imaging is used to clearly show the sites and shapes of beta amyloid deposits in living subjects using a C11 tracer that binds selectively to such deposits.[7] Such tools may help greatly in assisting clinical research for therapies.
Treatment
Main article: Clinical research to halt Alzheimer's disease & mild cognitve impairmentThere is no proven treatment or therapy for mild cognitive impairment. As MCI may represent a prodromal state to clinical Alzheimer’s disease, treatments proposed for Alzheimer’s disease, such as antioxidants and cholinesterase inhibitors, may be useful. However, several potential treatments are still under investigations.[2] Two drugs used to treat Alzheimer's disease have been assessed for their ability to treat MCI or prevent progression to full Alzheimer's disease. Rivastigmine failed to stop or slow progression to Alzheimer's disease or on cognitive function for individuals with mild cognitive impairment,[8] and donepezil showed only minor, short-term benefits and was associated with significant side effects.[9]
In a two-year randomized trial of 168 people with MCI given either high-dose vitamins or placebo, vitamins cut the rate of brain shrinkage by up to half. The vitamins were the three B vitamins folic acid, vitamin B6, and vitamin B12, which inhibit production of the amino acid homocysteine. High blood levels of homocysteine are associated with increased risk of dementia and cardiovascular disease.[10][11]
References
- ^ Petersen RC, Smith GE, Waring SC, Ivnik RJ, Tangalos EG, Kokmen E (1999). "Mild cognitive impairment: clinical characterization and outcome". Arch. Neurol. 56 (3): 303–8. doi:10.1001/archneur.56.3.303. PMID 10190820.
- ^ a b c d Grundman M, Petersen RC, Ferris SH, et al. (2004). "Mild cognitive impairment can be distinguished from Alzheimer disease and normal aging for clinical trials". Arch. Neurol. 61 (1): 59–66. doi:10.1001/archneur.61.1.59. PMID 14732621.
- ^ Tabert MH, Manly JJ, Liu X, et al. (2006). "Neuropsychological prediction of conversion to Alzheimer disease in patients with mild cognitive impairment". Arch. Gen. Psychiatry 63 (8): 916–24. doi:10.1001/archpsyc.63.8.916. PMID 16894068.
- ^ Morris JC, Storandt M, Miller JP, et al. (2001). "Mild cognitive impairment represents early-stage Alzheimer disease". Arch. Neurol. 58 (3): 397–405. doi:10.1001/archneur.58.3.397. PMID 11255443.
- ^ Petersen RC, Parisi JE, Dickson DW, et al. (2006). "Neuropathologic features of amnestic mild cognitive impairment". Arch. Neurol. 63 (5): 665–72. doi:10.1001/archneur.63.5.665. PMID 16682536.
- ^ Whitwell JL, Shiung MM, Przybelski SA, et al. (2008). "MRI patterns of atrophy associated with progression to AD in amnestic mild cognitive impairment". Neurology 70 (7): 512–20. doi:10.1212/01.wnl.0000280575.77437.a2. PMC 2734138. PMID 17898323. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2734138.
- ^ Jack CR, Lowe VJ, Senjem ML, et al. (2008). "11C PiB and structural MRI provide complementary information in imaging of Alzheimer's disease and amnestic mild cognitive impairment" (pdf). Brain 131 (Pt 3): 665–80. doi:10.1093/brain/awm336. PMC 2730157. PMID 18263627. http://brain.oxfordjournals.org/cgi/reprint/131/3/665.
- ^ Feldman HH, Ferris S, Winblad B, et al. (2007). "Effect of rivastigmine on delay to diagnosis of Alzheimer's disease from mild cognitive impairment: the InDDEx study". Lancet Neurol 6 (6): 501–12. doi:10.1016/S1474-4422(07)70109-6. PMID 17509485.
- ^ Birks J, Flicker L (2006). Birks, Jacqueline. ed. "Donepezil for mild cognitive impairment". Cochrane Database Syst Rev 3: CD006104. doi:10.1002/14651858.CD006104. PMID 16856114.
- ^ Kelland, K. (2010). B vitamins found to halve aging brain shrinkage. Reuters Health.
- ^ Ravaglia, G. Forti, P., Maioli, F., Matelli, M., Servadei, L., Nicoletta, B., Elisa, Porcellini & Licastor, F. (2005). "Homocysteine and folate as risk factors for dementia and Alzheimer disease". the American Journal of Clinical Nutrition 82 (3): 636–643. PMID 16155278. http://www.ajcn.org/content/82/3/636.full.
External links
- MCI information from the UCSF Memory and Aging Center
- Mild cognitive impairment Alzheimer's Society fact sheet
- Topic Sheet on Mild Cognitive Impairment
Pathology of the nervous system, primarily CNS (G04–G47, 323–349) Inflammation Encephalitis (Viral encephalitis, Herpesviral encephalitis) · Cavernous sinus thrombosis · Brain abscess (Amoebic)Myelitis: Poliomyelitis · Demyelinating disease (Transverse myelitis) · Tropical spastic paraparesis · Epidural abscessBoth/eitherBrain/
encephalopathyBasal ganglia disease: Parkinsonism (PD, Postencephalitic, NMS) · PKAN · Tauopathy (PSP) · Striatonigral degeneration · Hemiballismus · HD · OADyskinesia: Dystonia (Status dystonicus, Spasmodic torticollis, Meige's, Blepharospasm) · Chorea (Choreoathetosis) · Myoclonus (Myoclonic epilepsy) · Akathesiaautoimmune (Multiple sclerosis, Neuromyelitis optica, Schilder's disease) · hereditary (Adrenoleukodystrophy, Alexander, Canavan, Krabbe, ML, PMD, VWM, MFC, CAMFAK syndrome) · Central pontine myelinolysis · Marchiafava-Bignami disease · Alpers' diseaseEpisodic/
paroxysmalIntracranial hypertension (Hydrocephalus/NPH, Idiopathic intracranial hypertension) · Cerebral edema · Intracranial hypotensionOtherSpinal cord/
myelopathyBoth/either LMN only: PMA · PBP (Fazio-Londe, Infantile progressive bulbar palsy) · SMA (SMN-linked, Kennedy disease, SMAX2, DSMA1)both: ALSCategories:
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