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Profiles of Normal Cognition in Essential Tremor

Published online by Cambridge University Press:  04 October 2019

Tess E. K. Cersonsky Open the ORCID record for Tess E. K. Cersonsky [Opens in a new window] ,
Sarah Kellner ,
Silvia Chapman ,
Edward D. Huey ,
Elan D. Louis  and
Stephanie Cosentino
Tess E. K. Cersonsky
Affiliation:
Division of Movement Disorders, Department of Neurology, Yale School of Medicine, Yale University, New Haven, CT 06520, USA
Sarah Kellner
Affiliation:
Division of Movement Disorders, Department of Neurology, Yale School of Medicine, Yale University, New Haven, CT 06520, USA
Silvia Chapman
Affiliation:
Taub Institute for Research on Alzheimer’s Disease and the Aging Brain, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
Edward D. Huey
Affiliation:
Taub Institute for Research on Alzheimer’s Disease and the Aging Brain, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA Department of Psychiatry, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA Department of Neurology, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
Elan D. Louis
Affiliation:
Division of Movement Disorders, Department of Neurology, Yale School of Medicine, Yale University, New Haven, CT 06520, USA Department of Chronic Disease Epidemiology, Yale School of Public Health, Yale University, New Haven, CT 06520, USA Center for Neuroepidemiology and Clinical Neurological Research, Yale School of Medicine, Yale University, New Haven, CT 06520, USA
Stephanie Cosentino*
Affiliation:
Taub Institute for Research on Alzheimer’s Disease and the Aging Brain, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA Department of Psychiatry, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
*
*Correspondence and reprint requests to: Stephanie Cosentino, Columbia University Medical Center, 630 West 168th Street, P&S Mailbox 16, New York, NY 10032, USA. E-mail: [email protected]
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Abstract

Objectives:

Patients with essential tremor exhibit heterogeneous cognitive functioning. Although the majority of patients fall under the broad classification of cognitively “normal,” essential tremor is associated with increased risk for mild cognitive impairment and dementia. It is possible that patterns of cognitive performance within the wide range of normal functioning have predictive utility for mild cognitive impairment or dementia. These cross-sectional analyses sought to determine whether cognitive patterns, or “clusters,” could be identified among individuals with essential tremor diagnosed as cognitively normal. We also determined whether such clusters, if identified, were associated with demographic or clinical characteristics of patients.

Methods:

Elderly subjects with essential tremor (age >55 years) underwent comprehensive neuropsychological testing. Domain means (memory, executive function, attention, visuospatial abilities, and language) from 148 individuals diagnosed as cognitively normal were partitioned using k-means cluster analysis. Individuals in each cluster were compared according to cognitive functioning (domain means and test scores), demographic factors, and clinical variables.

Results:

There were three clusters. Cluster 1 (n = 64) was characterized by comparatively low memory scores (p < .001), Cluster 2 (n = 39) had relatively low attention and visuospatial scores (p < .001), and Cluster 3 (n = 45) exhibited consistently high performance across all domains. Cluster 1 had lower Montreal Cognitive Assessment scores and reported more prescription medication use and lower balance confidence.

Conclusions:

Three patterns of cognitive functioning within the normal range were evident and tracked with certain clinical features. Future work will examine the extent to which such patterns predict conversion to mild cognitive impairment and/or dementia.

Keywords

Cognitive agingCerebellar diseasesMovement disordersAttentionMemoryPostural balance
Type
Regular Research
Information
Journal of the International Neuropsychological Society , Volume 26 , Issue 2 , February 2020 , pp. 197 - 209
Copyright
Copyright © INS. Published by Cambridge University Press, 2019 

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References

REFERENCES

Bareš, M., Husárová, I., & Lungu, O. V. (2012). Essential tremor, the cerebellum, and motor timing: towards integrating them into one complex entity. Tremor and Other Hyperkinetic Movements (New York, N.Y.), 2, tre-02-93-653-1.Google Scholar
Benito-León, J. & Louis, E. D. (2007). Clinical update: diagnosis and treatment of essential tremor. The Lancet, 369(9568), 1152–1154. https://doi.org/10.1016/S0140-6736(07)60544-3 CrossRefGoogle ScholarPubMed
Benito-León, J., Louis, E. D., Bermejo-Pareja, F., & Neurological Disorders in Central Spain (NEDICES) Study Group. (2006a). Elderly-onset essential tremor is associated with dementia. Neurology, 66(10), 1500–1505. https://doi.org/10.1212/01.wnl.0000216134.88617.de CrossRefGoogle ScholarPubMed
Benito-León, J., Louis, E. D., Bermejo-Pareja, F., & Neurological Disorders in Central Spain (NEDICES) Study Group. (2006b). Population-based case-control study of cognitive function in essential tremor. Neurology, 66(1), 69–74. https://doi.org/10.1212/01.wnl.0000192393.05850.ec CrossRefGoogle ScholarPubMed
Benito-León, J., Louis, E. D., Mitchell, A. J., & Bermejo-Pareja, F. (2011). Elderly-onset essential tremor and mild cognitive impairment: a population-based study. Journal of Alzheimer’s Disease, 23(4), 727–735.CrossRefGoogle ScholarPubMed
Benito-León, J., Louis, E. D., Sánchez-Ferro, Á., & Bermejo-Pareja, F. (2013). Rate of cognitive decline during the premotor phase of essential tremor: a prospective study. Neurology, 81(1), 60–66.CrossRefGoogle ScholarPubMed
Benton, A., des Hamsher, K., Rey, G., & Sivan, A. (1994). Multilingual aphasia examination (3rd ed.). Iowa City, IA: AJA Associates.Google Scholar
Benton, A., Sivan, A., des Hamsher, K., Varney, N., & Spreen, O. (1994). Contributions to neuropsychological assessment (2nd ed.). New York, NY: Oxford University Press.Google Scholar
Benton, A. L. & Van Allen, M. W. (1968). Impairment in facial recognition in patients with cerebral disease. Transactions of the American Neurological Association, 93, 38–42.Google ScholarPubMed
Bermejo-Pareja, F., Louis, E. D., Benito-León, J., & Neurological Disorders in Central Spain (NEDICES) Study Group. (2007). Risk of incident dementia in essential tremor: a population-based study. Movement Disorders, 22(11), 1573–1580. https://doi.org/10.1002/mds.21553 CrossRefGoogle ScholarPubMed
Bruehl, S., Lofland, K. R., Semenchuk, E. M., Rokicki, L. A., & Penzien, D. B. (1999). Use of cluster analysis to validate IHS diagnostic criteria for migraine and tension-type headache. Headache, 39, 181–189.CrossRefGoogle ScholarPubMed
Busch, R. M., Chelune, G. J., & Suchy, Y. (2006). Using norms in neuropsychological assessment of the elderly. In Attix, D. K. & Welsh-Bohmer, K. A. (Eds.), Geriatric neuropsychology: assessment and intervention (pp. 133–157). New York: Guilford.Google Scholar
Cersonsky, T. E. K., Morgan, S., Kellner, S., Robakis, D., Liu, X., Huey, E. D., Louis, E. D., & Cosentino, S. (2018). Evaluating mild cognitive impairment in essential tremor: how many and which neuropsychological tests? Journal of the International Neuropsychological Society, 24(10), 1084–1098. https://doi.org/10.1017/S1355617718000747 CrossRefGoogle ScholarPubMed
Chamorro-Premuzic, T., Von Stumm, S., & Furnham, A. (2011). To what extent do individual differences exist in aging-related cognitive changes? In Chamorro-Premuzic, T., von Stumm, S., & Furnham, A. (Eds.), The Wiley-Blackwell Handbook of Individual Differences (p. 820). Malden, MA: Wiley-Blackwell.CrossRefGoogle Scholar
Chiu, C.-Y., Douglas, J. A., & Li, X. (2009). Cluster analysis for cognitive diagnosis: Theory and applications. Psychometrika, 74(4), 633–665. https://doi.org/10.1007/S11336-009-9125-0 CrossRefGoogle Scholar
Cho, B., Scarpace, D., & Alexander, N. B. (2004). Tests of stepping as indicators of mobility, balance, and fall risk in balance-impaired older adults. Journal of the American Geriatrics Society, 52(7), 1168–1173. https://doi.org/10.1111/j.1532-5415.2004.52317.x CrossRefGoogle ScholarPubMed
Collins, K., Rohl, B., Morgan, S., Huey, E. D., Louis, E. D., & Cosentino, S. (2017). Mild cognitive impairment subtypes in a cohort of elderly essential tremor cases. Journal of the International Neuropsychological Society, 23(5), 390–399. https://doi.org/10.1017/S1355617717000170 CrossRefGoogle Scholar
Cumming, R. G., Salkeld, G., Thomas, M., & Szonyi, G. (2000). Prospective study of the impact of fear of falling on activities of daily living, SF-36 scores, and nursing home admission. The Journals of Gerontology. Series A, Biological Sciences and Medical Sciences, 55(5), M299–M305.CrossRefGoogle ScholarPubMed
Delis, D., Kaplan, E., & Kramer, J. (2001). Delis Kaplan Executive Function System (DKEFS) examiner’s manual. San Antonio, TX: Pearson.Google Scholar
Delis, D., Kramer, K., Kaplan, E., & Ober, B. (2000). California verbal learning test - second edition (CVLT-II). San Antonio, TX: Psychological Corporation.Google Scholar
Deuschl, G., Wenzelburger, R., Löffler, K., Raethjen, J., & Stolze, H. (2000). Essential tremor and cerebellar dysfunction clinical and kinematic analysis of intention tremor. Brain, 123(8), 1568–1580. https://doi.org/10.1093/brain/123.8.1568 CrossRefGoogle ScholarPubMed
Dogu, O., Sevim, S., Camdeviren, H., Sasmaz, T., Bugdayci, R., Aral, M., Kaleagasi, H., Un, S., & Louis, E. D. (2003). Prevalence of essential tremor: door-to-door neurologic exams in Mersin Province, Turkey. Neurology, 61(12), 1804–1806.CrossRefGoogle ScholarPubMed
Farrell, K., Cosentino, S., Iida, M. A., Chapman, S., Bennett, D. A., Faust, P. L., Louis, E. D., & Crary, J. F. (2019). Quantitative assessment of pathological Tau burden in essential tremor: a postmortem study. Journal of Neuropathology & Experimental Neurology, 78(1), 31–37. https://doi.org/10.1093/jnen/nly104 CrossRefGoogle ScholarPubMed
Folstein, M. F., Folstein, S. E., & McHugh, P. R. (1975). “Mini-mental state”: A practical method for grading the cognitive state of patients for the clinician. Journal of Psychiatric Research, 12(3), 189–198.CrossRefGoogle ScholarPubMed
Frisina, P. G., Tse, W., Hälbig, T. D., & Libow, L. S. (2009). The pattern of cognitive-functional decline in elderly essential tremor patients: an exploratory-comparative study with Parkinson’s and Alzheimer’s disease patients. Journal of the American Medical Directors Association, 10(4), 238–242. https://doi.org/10.1016/j.jamda.2008.10.013 CrossRefGoogle ScholarPubMed
Gasparini, M., Bonifati, V., Fabrizio, E., Fabbrini, G., Brusa, L., Lenzi, G. L., & Meco, G. (2001). Frontal lobe dysfunction in essential tremor: a preliminary study. Journal of Neurology, 248(5), 399–402.CrossRefGoogle ScholarPubMed
Goldman, J. G., Holden, S., Ouyang, B., Bernard, B., Goetz, C. G., & Stebbins, G. T. (2015). Diagnosing PD-MCI by MDS Task Force criteria: How many and which neuropsychological tests? Movement Disorders : Official Journal of the Movement Disorder Society, 30(3), 402–406. https://doi.org/10.1002/mds.26084 CrossRefGoogle ScholarPubMed
Hanajima, R., Tsutsumi, R., Shirota, Y., Shimizu, T., Tanaka, N., & Ugawa, Y. (2016). Cerebellar dysfunction in essential tremor. Movement Disorders, 31(8), 1230–1234. https://doi.org/10.1002/mds.26629 CrossRefGoogle ScholarPubMed
Hauser, J., & Rybakowski, J. (1997). Three clusters of male alcoholics. Drug and Alcohol Dependence, 48(3), 243–250. https://doi.org/10.1016/S0376-8716(97)00130-0 CrossRefGoogle ScholarPubMed
Higginson, C. I., Wheelock, V. L., Levine, D., King, D. S., Pappas, C. T. E., & Sigvardt, K. A. (2008). Cognitive deficits in essential tremor consistent with frontosubcortical dysfunction. Journal of Clinical and Experimental Neuropsychology, 30(7), 760–765. https://doi.org/10.1080/13803390701754738 CrossRefGoogle ScholarPubMed
Janicki, S. C., Cosentino, S., & Louis, E. D. (2013). The cognitive side of essential tremor: what are the therapeutic implications? Therapeutic Advances in Neurological Disorders, 6(6), 353–368. https://doi.org/10.1177/1756285613489591 CrossRefGoogle ScholarPubMed
Kaplan, E., Goodglass, H., & Weintraub, S. (1983). Boston naming test. Philadelphia, PA: Lea & Febiger.Google Scholar
Kim, J.-S., Song, I.-U., Shim, Y.-S., Park, J.-W., Yoo, J.-Y., Kim, Y.-I., & Lee, K.-S. (2009). Cognitive impairment in essential tremor without dementia. Journal of Clinical Neurology, 5(2), 81. https://doi.org/10.3988/jcn.2009.5.2.81 CrossRefGoogle ScholarPubMed
LaRoia, H. & Louis, E. D. (2011). Association between essential tremor and other neurodegenerative diseases: what is the epidemiological evidence? Neuroepidemiology, 37(1), 1–10. https://doi.org/10.1159/000328866 CrossRefGoogle ScholarPubMed
Lawton, M. P. & Brody, E. M. (1969). Assessment of older people: self-maintaining and instrumental activities of daily living. The Gerontologist, 9(3), 179–186. https://doi.org/10.1093/geront/9.3_Part_1.179 CrossRefGoogle ScholarPubMed
Lombardi, W. J., Woolston, D. J., Roberts, J. W., & Gross, R. E. (2001). Cognitive deficits in patients with essential tremor. Neurology, 57(5), 785–790. https://doi.org/10.1212/WNL.57.5.785 CrossRefGoogle ScholarPubMed
Louis, E. D. (2010). Functional correlates of lower cognitive test scores in essential tremor. Movement Disorders, 25(4), 481–485. https://doi.org/10.1002/mds.22920 CrossRefGoogle ScholarPubMed
Louis, E. D. (2016). Linking essential tremor to the cerebellum: neuropathological evidence. The Cerebellum, 15(3), 235–242. https://doi.org/10.1007/s12311-015-0692-6 CrossRefGoogle ScholarPubMed
Louis, E. D., Babij, R., Ma, K., Cortés, E., & Vonsattel, J.-P. G. (2013). Essential tremor followed by progressive supranuclear palsy: postmortem reports of 11 patients. Journal of Neuropathology and Experimental Neurology, 72(1), 8–17. https://doi.org/10.1097/NEN.0b013e31827ae56e CrossRefGoogle ScholarPubMed
Louis, E. D., Benito-León, J., Vega-Quiroga, S., Bermejo-Pareja, F., & Neurological Disorders in Central Spain (NEDICES) Study Group. (2010a). Cognitive and motor functional activity in non-demented community-dwelling essential tremor cases. Journal of Neurology, Neurosurgery & Psychiatry, 81(9), 997–1001. https://doi.org/10.1136/jnnp.2009.202838 CrossRefGoogle ScholarPubMed
Louis, E. D., Benito-León, J., Vega-Quiroga, S., Bermejo-Pareja, F., & Neurological Disorders in Central Spain (NEDICES) Study Group. (2010b). Faster rate of cognitive decline in essential tremor cases than controls: A prospective study. European Journal of Neurology, 17(10), 1291–1297. https://doi.org/10.1111/j.1468-1331.2010.03122.x CrossRefGoogle ScholarPubMed
Louis, E. D. & Ferreira, J. J. (2010). How common is the most common adult movement disorder? Update on the worldwide prevalence of essential tremor. Movement Disorders, 25(5), 534–541. https://doi.org/10.1002/mds.22838 CrossRefGoogle ScholarPubMed
Louis, E. D., Ford, B., & Bismuth, B. (1998). Reliability between two observers using a protocol for diagnosing essential tremor. Movement Disorders, 13(2), 287–293. https://doi.org/10.1002/mds.870130215 CrossRefGoogle ScholarPubMed
Louis, E. D., Kellner, S., Morgan, S., Collins, K., Rohl, B., Huey, E. D., & Cosentino, S. (2017). Cognitive dysfunction is associated with greater imbalance and falls in essential tremor. Frontiers in Neurology, 8, 154. https://doi.org/10.3389/fneur.2017.00154 CrossRefGoogle ScholarPubMed
Louis, E. D., Ottman, R., Ford, B., Pullman, S., Martinez, M., Fahn, S., & Hauser, W. A. (1997). The Washington heights-inwood genetic study of essential tremor: methodologic issues in essential-tremor research. Neuroepidemiology, 16(3), 124–133. https://doi.org/10.1159/000109681 CrossRefGoogle ScholarPubMed
Louis, E. D., & Rao, A. K. (2014). Tandem gait performance in essential tremor patients correlates with cognitive function. Cerebellum & Ataxias, 1, 19. https://doi.org/10.1186/s40673-014-0019-2 CrossRefGoogle ScholarPubMed
Louis, E. D., Rao, A. K., & Gerbin, M. (2012). Functional correlates of gait and balance difficulty in essential tremor: balance confidence, near misses and falls. Gait & Posture, 35(1), 43–47. https://doi.org/10.1016/j.gaitpost.2011.08.002 CrossRefGoogle ScholarPubMed
Louis, E. D., Vonsattel, J. P. G., Honig, L. S., Lawton, A., Moskowitz, C., Ford, B., & Frucht, S. (2006). Essential tremor associated with pathologic changes in the cerebellum. Archives of Neurology, 63(8), 1189. https://doi.org/10.1001/archneur.63.8.1189 CrossRefGoogle ScholarPubMed
Louis, E. D., Wendt, K. J., Albert, S. M., Pullman, S. L., Yu, Q., & Andrews, H. (1999). Validity of a performance-based test of function in essential tremor. Archives of Neurology, 56(7), 841–846.CrossRefGoogle ScholarPubMed
Mameli, F., Tomasini, E., Scelzo, E., Fumagalli, M., Ferrucci, R., Bertolasi, L., & Priori, A. (2013). Lies tell the truth about cognitive dysfunction in essential tremor: an experimental deception study with the guilty knowledge task. Journal of Neurology, Neurosurgery, and Psychiatry, 84(9), 1008–1013. https://doi.org/10.1136/jnnp-2012-304674 CrossRefGoogle ScholarPubMed
Manly, J. J., Touradji, P., Tang, M.-X., & Stern, Y. (2003). Literacy and memory decline among ethnically diverse elders. Journal of Clinical and Experimental Neuropsychology, 25(5), 680–690. https://doi.org/10.1076/jcen.25.5.680.14579 CrossRefGoogle ScholarPubMed
Middleton, F. A., & Strick, P. L. (2000a). Basal ganglia and cerebellar loops: motor and cognitive circuits. Brain Research. Brain Research Reviews, 31(2–3), 236–250.CrossRefGoogle ScholarPubMed
Middleton, F. A., & Strick, P. L. (2000b). Basal ganglia output and cognition: evidence from anatomical, behavioral, and clinical studies. Brain and Cognition, 42(2), 183–200. https://doi.org/10.1006/brcg.1999.1099 CrossRefGoogle ScholarPubMed
Middleton, F. A. & Strick, P. L. (2001). Cerebellar projections to the prefrontal cortex of the primate. The Journal of Neuroscience : The Official Journal of the Society for Neuroscience, 21(2), 700–712.CrossRefGoogle ScholarPubMed
Montgomery, E. B., Baker, K. B., Lyons, K., & Koller, W. C. (2000). Motor initiation and execution in essential tremor and Parkinson’s disease. Movement Disorders, 15(3), 511–515. https://doi.org/10.1002/1531-8257(200005)15:3<511::AID-MDS1014>3.0.CO;2-R 3.0.CO;2-R>CrossRefGoogle ScholarPubMed
Morris, J. C. (1993). The Clinical Dementia Rating (CDR): current version and scoring rules. Neurology, 43(11), 2412–2414.CrossRefGoogle ScholarPubMed
Morris, J. C. (1997). Clinical dementia rating: a reliable and valid diagnostic and staging measure for dementia of the Alzheimer type. International Psychogeriatrics, 9(Suppl 1), 173–176; discussion 177-8.CrossRefGoogle ScholarPubMed
Nasreddine, Z. S., Phillips, N. A., Bédirian, V., Charbonneau, S., Whitehead, V., Collin, I., Cummings, J. L., & Chertkow, H. (2005). The Montreal Cognitive Assessment, MoCA: a brief screening tool for mild cognitive impairment. Journal of the American Geriatrics Society, 53(4), 695–699. https://doi.org/10.1111/j.1532-5415.2005.53221.x CrossRefGoogle ScholarPubMed
Pan, J. J., Lee, M., Honig, L. S., Vonsattel, J.-P. G., Faust, P. L., & Louis, E. D. (2014). Alzheimer’s-related changes in non-demented essential tremor patients vs. controls: links between tau and tremor? Parkinsonism & Related Disorders, 20(6), 655–658. https://doi.org/10.1016/j.parkreldis.2014.03.003 CrossRefGoogle ScholarPubMed
Passamonti, L., Novellino, F., Cerasa, A., Chiriaco, C., Rocca, F., Matina, M. S., Fera, F., & Quattrone, A. (2011). Altered cortical-cerebellar circuits during verbal working memory in essential tremor. Brain, 134(8), 2274–2286. https://doi.org/10.1093/brain/awr164 CrossRefGoogle ScholarPubMed
Peretz, C., Herman, T., Hausdorff, J. M., & Giladi, N. (2006). Assessing fear of falling: can a short version of the activities-specific balance confidence scale be useful? Movement Disorders, 21(12), 2101–2105. https://doi.org/10.1002/mds.21113 CrossRefGoogle ScholarPubMed
Salthouse, T. A. (2004). What and when of cognitive aging. Current Directions in Psychological Science, 13(4), 140–144. https://doi.org/10.1111/j.0963-7214.2004.00293.x CrossRefGoogle Scholar
Schmahmann, J. D. & Caplan, D. (2006). Cognition, emotion and the cerebellum. Brain, 129(2), 290–292. https://doi.org/10.1093/brain/awh729 CrossRefGoogle ScholarPubMed
Sengul, Y., Sengul, H. S., Yucekaya, S. K., Yucel, S., Bakim, B., Pazarcı, N. K., & Özdemir, G. (2015). Cognitive functions, fatigue, depression, anxiety, and sleep disturbances: assessment of nonmotor features in young patients with essential tremor. Acta Neurologica Belgica, 115(3), 281–287. https://doi.org/10.1007/s13760-014-0396-6 CrossRefGoogle ScholarPubMed
Sinoff, G. & Badarny, S. (2014). Mild cognitive impairment, dementia, and affective disorders in essential tremor: a prospective study. Tremor and Other Hyperkinetic Movements (New York, NY), 4, 227. https://doi.org/10.7916/D85B00KN Google ScholarPubMed
Smith, A. (1982). Symbol digit modalities test. Los Angeles, CA: Western Psychological Services.Google Scholar
Souza, C. P., Oliveira, G. N., Foss, M. P., & Tumas, V. (2016). Cluster analysis of cognitive performance in a sample of patients with Parkinson’s disease. Dementia & Neuropsychologia, 10(4), 315–319. https://doi.org/10.1590/s1980-5764-2016dn1004010 CrossRefGoogle Scholar
Szeto, J. Y., O′Callaghan, C., Shine, J. M., Walton, C. C., Mowszowski, L., Naismith, S. L., Halliday, G. M., & Lewis, S. J. (2015). The relationships between mild cognitive impairment and phenotype in Parkinson’s disease. NPJ Parkinson’s Disease, 1(1), 15015. https://doi.org/10.1038/npjparkd.2015.15 CrossRefGoogle ScholarPubMed
Thawani, S. P., Schupf, N., & Louis, E. D. (2009). Essential tremor is associated with dementia: Prospective population-based study in New York. Neurology, 73(8), 621–625. https://doi.org/10.1212/WNL.0b013e3181b389f1 CrossRefGoogle ScholarPubMed
Tröster, A. I., Woods, S. P., Fields, J. A., Lyons, K. E., Pahwa, R., Higginson, C. I., & Koller, W. C. (2002). Neuropsychological deficits in essential tremor: an expression of cerebello-thalamo-cortical pathophysiology? European Journal of Neurology, 9(2), 143–151.CrossRefGoogle ScholarPubMed
Wechsler, D. (1987). Wechsler memory scale – revised. San Antonio, TX: Psychological Corporation.Google Scholar
Wechsler, D. (1997). Manual for the Wechsler adult intelligence scale (3rd ed.). San Antonio, TX: Psychological Corporation.Google Scholar
Wechsler, D. (2008). Wechsler memory scale (4th ed.). San Antonio, TX: Pearson.Google Scholar
Yesavage, J. A., Brink, T. L., Rose, T. L., Lum, O., Huang, V., Adey, M., & Leirer, V. O. (1982). Development and validation of a geriatric depression screening scale: a preliminary report. Journal of Psychiatric Research, 17(1), 37–49. https://doi.org/10.1016/0022-3956(82)90033-4 CrossRefGoogle ScholarPubMed