title: Is there a one-way street from essential tremor to Parkinson's disease? Possible biological ramifications.
abstract: There is considerable evidence for an association between essential tremor (ET) and Parkinson's disease (PD), although the topic remains somewhat controversial. An important issue, not previously addressed, is what seems to be the unidirectional nature of the relationship (ET→ET + PD and not PD→PD + ET). The aims of this review are (i) to discuss the evidence for and against a unidirectional relationship and (ii) to discuss the implications of such a unidirectional relationship, if it exists, for disease mechanisms. Evidence 'for' a unidirectional relationship includes (i) abundant clinical anecdotal observation and (ii) clinical and epidemiological studies. Evidence 'against' is theoretical rather than empirical. Overall, the evidence 'for' is stronger, although additional studies are needed in order to be certain; for the time being, it might be best to leave this as an open question. The biological ramifications/extensions of such a unidirectional relationship include (i) that the association is causal (i.e., some aspect of ET pathophysiology predisposes an individual to develop PD) and (ii) that some ET cases may have a circumscribed form of Lewy body disease, and the secondary development of PD may represent a spread of those Lewy bodies in the brainstem. The presence and nature of the links between ET and PD are controversial. Further primary data (epidemiological and pathological) are needed to improve understanding of the relationship and its implications for the pathogenesis of both disorders.
authors.affiliation: GH Sergievsky Center, College of Physicians and Surgeons, Columbia University, New York, NY, USA; Department of Neurology, College of Physicians and Surgeons, Columbia University, New York, NY, USA; Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, NY, USA.
authors.forename: E D
authors.initials: ED
authors.lastname: Louis
authors.forename: R
authors.initials: R
authors.lastname: Ottman
mesh_terms: D020329:Essential Tremor / Q000150:complications / Q000209:etiology*; D006801:Humans; D010300:Parkinson Disease / Q000209:etiology*
keywords: Parkinson's disease; biology; epidemiology; essential tremor; neurodegeneration
references.citation: Brain. 2007 Dec;130(Pt 12):3297-307
references.pmid: 18025031
references.citation: J Neurol Neurosurg Psychiatry. 1999 Nov;67(5):646-50
references.pmid: 10519872
references.citation: J Neurol. 2005 Aug;252(8):964-7
references.pmid: 15772736
references.citation: Neuroepidemiology. 2011;37(1):1-10
references.pmid: 21757958
references.citation: Lancet Neurol. 2010 Jun;9(6):613-22
references.pmid: 20451458
references.citation: J Neurol. 2000 Dec;247(12):955-9
references.pmid: 11200689
references.citation: Neurology. 2008 Apr 15;70(16 Pt 2):1452-5
references.pmid: 18413570
references.citation: Parkinsonism Relat Disord. 2003 Mar;9(4):225-31
references.pmid: 12618058
references.citation: Science. 1983 Feb 25;219(4587):979-80
references.pmid: 6823561
references.citation: J Neurol Neurosurg Psychiatry. 2005 Jan;76(1):115-7
references.pmid: 15608009
references.citation: Mov Disord. 2008 Aug 15;23(11):1602-5
references.pmid: 18618664
references.citation: Mov Disord. 2008 May 15;23(7):993-997
references.pmid: 18383536
references.citation: Neurology. 2004 Mar 9;62(5):734-41
references.pmid: 15007123
references.citation: Can Med Assoc J. 1973 Nov 3;109(9):876-8
references.pmid: 4750302
references.citation: Neuroepidemiology. 2007;29(3-4):208-12
references.pmid: 18043006
references.citation: Ann Neurol. 1988 Jul;24(1):23-6
references.pmid: 3415197
references.citation: Neurology. 2005 May 24;64(10):1721-5
references.pmid: 15911798
references.citation: Eur J Neurol. 2006 Dec;13(12):1302-5
references.pmid: 17116212
references.citation: Tremor Other Hyperkinet Mov (N Y). 2012;2:
references.pmid: 23439850
references.citation: Arch Neurol. 2006 Aug;63(8):1100-4
references.pmid: 16908735
references.citation: Mov Disord. 2011 Feb 15;26(3):391-8
references.pmid: 21462256
references.citation: Neurobiol Aging. 2003 Mar-Apr;24(2):197-211
references.pmid: 12498954
references.citation: J Neurol Neurosurg Psychiatry. 1984 May;47(5):466-70
references.pmid: 6736976
references.citation: Neurology. 1997 Feb;48(2):376-80
references.pmid: 9040725
references.citation: Mov Disord. 2009 Mar 15;24(4):626-7
references.pmid: 19185016
references.citation: Arch Neurol. 2009 Oct;66(10):1202-8
references.pmid: 19822775
references.citation: Neurology. 1991 Feb;41(2 ( Pt 1)):234-8
references.pmid: 1992367
references.citation: Brain. 1949 Jun;72(Pt. 2):113-39
references.pmid: 18136705
references.citation: J Neurol Neurosurg Psychiatry. 2009 Apr;80(4):423-5
references.pmid: 19289477
references.citation: Brain. 1963 Mar;86:95-110
references.pmid: 13928399
references.citation: Mov Disord. 2011 Feb 15;26(3):372-7
references.pmid: 21284040
references.citation: Ann Neurol. 1994 Jun;35(6):717-23
references.pmid: 8210229
references.citation: J Neurol Neurosurg Psychiatry. 1980 Mar;43(3):257-63
references.pmid: 7373323
references.citation: J Neurol Neurosurg Psychiatry. 1984 Jul;47(7):734-5
references.pmid: 6747649
references.citation: J Neurol Neurosurg Psychiatry. 2011 Jul;82(7):761-5
references.pmid: 21436230
references.citation: J Neurol. 1993 Nov;241(1):54-61
references.pmid: 8138823
references.citation: Mov Disord. 2009 Aug 15;24(11):1606-12
references.pmid: 19526587
references.citation: Arch Neurol. 2003 Mar;60(3):405-10
references.pmid: 12633153
references.citation: Expert Rev Neurother. 2012 Jun;12(6):687-96
references.pmid: 22650171
references.citation: Parkinsonism Relat Disord. 2008;14(1):15-8
references.pmid: 17703985
references.citation: Arch Neurol. 2005 Jun;62(6):1004-7
references.pmid: 15956174
references.citation: Dis Mon. 2011 Mar;57(3):109-26
references.pmid: 21447420
references.citation: Parkinsonism Relat Disord. 2007 Mar;13(2):67-76
references.pmid: 16887374
references.citation: Arch Phys Med Rehabil. 2006 May;87(5):661-70
references.pmid: 16635629
references.citation: Genet Med. 2001 May-Jun;3(3):197-9
references.pmid: 11388761