1. Affected had various tremors Spouses as controls, therefore produced bias Detailed analysis supported polygenic inheritance Relatives not examined Spouses as controls Potentially biased recruitment First degree relatives only Specialist clinic but consecutive patients Specialist clinic but consecutive patients points against a major X linked gene or mitochondrial inheritance;De Michele et al
2. Using a method which screens for an excess of repeats Carrero-Venezuela et al assessed 46 unrelated patients with Parkinson's disease and 11 families in whom "anticipation" was suspected and found no evidence of an association between prolonged CAG repeats and either sporadic or familial Parkinson's disease. Huntington's disease can present as a parkinsonian syndrome, particularly in the juvenile onset form. Rubinsztein et a!54 studied 45 patients for the CAG repeat expansion in the Huntington gene and found no differences between the patients and a control group
3. Worldwide occurrence of Parkinson's disease: an updated review;Zhang, Z.; Roman, G.C.;Neuroepidemiology,1993
4. Prevalence of Parkinson's disease in the elderly: the Rotterdam study;MC, De Rijk; MM, Breteler; GA, Graveland;Neurology,1995
5. Parkinson's disease: pathophysiology;Agid, Y.;Lancet,1991