6. Devos D, Schraen-Maschke S, Vuillaume I, et al. Clinical features and genetic analysis of a new form of spinocerebellar atrophy. Neurology 2001;56:234 –238. 7. Lang AE. Movement disorders: symptoms. In: Bradley WG, Da- roff RB, Fenichel GM, Marsden CD, editors. Neurology in clinical practice (3rd ed.). New York: Butterworth-Heineman; 2000. p 319 –340. 8. Wood NW, Harding AE. Ataxic disorders. In: Bradley WG, Daroff RB, Fenichel GM, Marsden CD, editors. Neurology in clinical practice (3rd ed.). New York: Butterworth-Heineman; 2000. p 309 –317. 9. Scho ¨ls L, Gispert S, Vorgerd M, et al. Spinocerebellar ataxia type 2, genotype and phenotype in German kindreds. Arch Neurol 1997;54:1073–1080. 10. Day JW, Schut LJ, Moseley ML, Durand MS, Ranum LPW. Spinocerebellar ataxia type 8. Clinical features in a large family. Neurology 2000;55:649 – 657. 11. Schelhaas HJ, Ippel PF, Hageman G, Sinke RJ, Van der Laan EN, Beemer FA. Clinical and genetic analysis of a four-generation family with a distinct autosomal dominant cerebellar ataxia. J Neu- rol 2001;248:113–120. 12. Yamashita I, Sasaki H, Yabe I, et al. A novel locus for dominant cerebellar ataxia (SCA14) maps to a 10.2-cM interval flanked by D19S206 and D19S605 on chromosome 19q13.4-qter. Ann Neurol 2000;48:156 –163. 13. Rolfs A, Koeppen AH, Bauer I, et al. Clinical features and neuro- pathology of autosomal dominant spinocerebellar ataxia (SCA 17). Ann Neurol 2003;54:367–375. 14. Van Swieten JC, Brusse E, De Graaf B, et al. A mutation in the fibroblast growth factor 14 gene is associated with autosomal dominant cerebellar ataxia (corrected). Am J Hum Genet 2003;72: 191–199. 15. Ford-Perriss M, Abud H, Murphy M. Fibroblast growth factors in the developing central nervous system. Clin Exp Pharmacol Physiol 2001;28:493–503. 16. Wang Q, Bardgett ME, Wong M, et al. Ataxia and paroxysmal dyskinesia in mice lacking axonally transported FGF14. Neuron 2002;35:25–28. 17. Dalski A, Atici J, Kreuz FR, Hellenbroich Y, Schwinger E, Zu ¨hlke C. Mutation analysis in the fibroblast growth factor 14 gene: frameshift mutation and polymorphisms in patients with inherited ataxias. Eur J Hum Genet 2005;13:118 –120. 18. Stevanin G, Durr A, Dussert C, Penet C, Brice A. Mutations in the FGF14 gene are not a major cause of spinocerebellar ataxia in Caucasians. Neurology 2004;63:936. On-Demand Deep Brain Stimulation for Essential Tremor: A Report on Four Cases Martin Kronenbuerger, MD, 1 * Christoph Fromm, MD, 1 Frank Block, MD, 1 Volker A. Coenen, MD, 2 Ina Rohde, MD, 2 Veit Rohde, MD, 2 and Johannes Noth, MD 1 1 Department of Neurology, University Hospital, RWTH Aachen, Germany; 2 Department of Neurosurgery, University Hospital, RWTH Aachen, Germany Abstract: Deep brain stimulation (DBS) is an established therapy for essential tremor (ET), but loss of efficacy due to tolerance can occur. Our objective was to evaluate if it is feasible to use DBS only on-demand and if this would prevent tolerance. We report on the effects of left-side thalamic DBS in 4 ET patients who were instructed to switch on stimulation only when using their right hand for motor tasks and were followed-up to 30 months after sur- gery. The patients were capable of using DBS only on- demand (DBS use of 22.0  13.5%/day). DBS led to a stable suppression of right arm tremor throughout the follow-up. No problems associated with tolerance such as tremor re- bound or late therapy failure occurred. In comparison to publications stating that ET patients had been using DBS continuously during the daytime, the use of on-demand DBS saves battery life, which delays surgical replacement of the stimulator. Thus, on-demand DBS saves money, may help to prevent tolerance, and should be adopted for the long-term treatment of ET patients. © 2005 Movement Dis- order Society Key words: deep brain stimulation; thalamus; on-demand use; essential tremor Thalamic deep brain stimulation (DBS) is an estab- lished therapy for disabling essential tremor (ET), 1–6 but loss of efficacy due to tolerance can occur. 1–3,5,7–9 Prob- lems attributed to tolerance are (1) the need for an increase of stimulation intensity to maintain tremor sup- pression in the first months after DBS implantation 1–3 ; (2) tremor rebound, which is a temporary increase of tremor intensity over the preoperative state after switch- ing off DBS 1,3 ; and (3) late therapy failure, which occurs up to a year after stable DBS effect on tremor has been established. 1,3,5,7–9 In the latter case, the increase of stim- *Correspondence to: Dr. Martin Kronenbuerger, Universitaetsklini- kum Aachen, Neurologische Klinik, Pauwelsstr. 30, 52074 Aachen, Germany. E-mail: martin_kronenbuerger@web.de Received 15 November 2004; Revised 10 March 2005; Accepted 26 June 2005 Published online 6 October 2005 in Wiley InterScience (www. interscience.wiley.com). DOI: 10.1002/mds.20714 ON-DEMAND DBS FOR ESSENTIAL TREMOR 401 Movement Disorders, Vol. 21, No. 3, 2006