title: [123I]-FP-CIT-SPECT demonstrates dopaminergic deficit in orthostatic tremor.
abstract: There is increasing evidence of a potential role of the dopaminergic system in orthostatic tremor (OT): Association with parkinsonism and treatment effects of L-dopa and dopamine agonists have been reported. Eleven patients with isolated OT had single-photon emission computed tomography (SPECT) using (123)I-FP-CIT ([(123)I]-2 beta-carbomethoxy-3beta-(-4-iodophenyl)-N-(3-fluoropropyl)-nortropane) as dopamine transporter tracer. Results were compared with 12 age-matched normal controls and 12 patients with Parkinson's disease (PD). A marked reduction in striatal tracer binding was found in OT compared to normal controls (p < 0.001). Tracer uptake was significantly higher and more symmetrical than in PD, and caudate and putamen were equally affected. L-dopa challenges, performed in seven patients, showed a small but non-significant improvement on EMG and a small but significant improvement in clinical parameters on blinded video rating. Two-month open-label L-dopa treatment (600 mg/day) led to a small improvement in two of five patients but no significant overall change. Olfactory function on University of Pennsylvania Smell Identification Test was normal. Our finding of a marked tracer uptake reduction on dopamine transporter SPECT supports a role of the dopaminergic system in OT. Lack of evidence of a clinically relevant therapeutic response to L-dopa suggests that other mechanisms must also be involved in the pathogenesis.
authors.affiliation: National Hospital for Neurology and Neurosurgery, London, United Kingdom.
authors.forename: Regina
authors.initials: R
authors.lastname: Katzenschlager
authors.forename: Durval
authors.initials: D
authors.lastname: Costa
authors.forename: Willibald
authors.initials: W
authors.lastname: Gerschlager
authors.forename: John
authors.initials: J
authors.lastname: O'Sullivan
authors.forename: Jan
authors.initials: J
authors.lastname: Zijlmans
authors.forename: Svetoslav
authors.initials: S
authors.lastname: Gacinovic
authors.forename: Walter
authors.initials: W
authors.lastname: Pirker
authors.forename: Adrian
authors.initials: A
authors.lastname: Wills
authors.forename: Kailash
authors.initials: K
authors.lastname: Bhatia
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Lees
authors.forename: Peter
authors.initials: P
authors.lastname: Brown
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D004298:Dopamine / Q000502:physiology*; D015259:Dopamine Agents / Q000008:administration & dosage; D004576:Electromyography; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes; D007980:Levodopa / Q000008:administration & dosage; D008297:Male; D008875:Middle Aged; D012903:Smell / Q000502:physiology; D015899:Tomography, Emission-Computed, Single-Photon; D014202:Tremor / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000503:physiopathology*; D014326:Tropanes; D014743:Videotape Recording
chemical_list: D015259:Dopamine Agents; D007457:Iodine Radioisotopes; D014326:Tropanes; C087552:2-carbomethoxy-8-(3-fluoropropyl)-3-(4-iodophenyl)tropane; D007980:Levodopa; D004298:Dopamine