Alzheimer's disease and essential tremor finally meet

✍ Scribed by Rodger J. Elble; Richard M. Dubinsky; Tom Ala

• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 48 KB
• Volume: 22
• Category: Article
• ISSN: 0885-3185
• DOI: 10.1002/mds.21595

✦ Synopsis

Classic essential tremor (ET) is a monosymptomatic tremor disorder with no other neurological signs except for mild impairment of balance and tandem walking in some advanced patients. 1 Consequently, neurological abnormalities other than tremor should be regarded as "red flags" that some other disorder is present, either in isolation or in combination with ET. 2 However, recent studies have revealed other subclinical deficits in ET. Decreased initial ocular smooth pursuit acceleration and impaired reduction of the time constant of post-rotatory vestibular nystagmus were found by Helmchen et al. 3 and are consistent with vestibulocerebellar dysfunction. Reports of mild olfactory impairment have been disputed. 4,5 Subclinical deficits in cognitive function 6 -9 and increased prevalence of dementia 10 have also been reported.

In this issue of Movement Disorders, Bermejo-Pareja et al. used an already well-established cohort of people from central Spain to estimate the incidence of dementia in ET patients and controls. ET patients with tremor onset after age 65 were twice as likely to develop dementia, compared with controls and ET patients with tremor onset at a younger age. Sixteen (7.8%) of 206 ET cases developed incident dementia compared with 145 (3.9%) of controls. The mean latency between the onset of ET and the onset of dementia was 10.5 years (median 6.8 years, range 2.5-53 years). Only two of the 97 (2.1%) young-onset ET cases developed dementia, compared