title: Acoustic startle response in patients with orthostatic tremor.
abstract: OBJECTIVE
  Orthostatic tremor is a high frequency tremor predominantly on calf muscles during standing. Brainstem is the most probable generator in the pathogenesis since it comprises bilaterally projecting centers regulating stance or tone. We aimed to investigate the functional role of brainstem through the evaluation of acoustic startle response in primary orthostatic tremor patients.
  
  
  METHODS
  We included 7 (2 males) consecutive patients and 13 (5 males) healthy volunteers. Diagnosis was confirmed by polymyographic surface electromyography. All subjects underwent acoustic startle response and blink reflex investigations.
  
  
  RESULTS
  Presence rate (71.4% vs. 100%, p=0.042) and response rate (27.5% vs. 40.5%, p=0.047) of total acoustic startle response were lower in patient group. Similarly, probability over orbicularis oculi was lower among patients (p=0.003). However, blink reflex was observed in all patients and healthy volunteers and latencies of startle and blink reflexes were similar between groups.
  
  
  CONCLUSIONS
  In our patient group, normal response rate and latencies of R1 and R2 show structural integrity of at least blink reflex circuit at brainstem. On the other hand, suppressed response rates probably reflect decreased excitability of auditory startle reflex pathway.
authors.affiliation: Department of Neurology, Cerrahpasa School of Medicine, Istanbul University, Istanbul, Turkey.
authors.forename: Meral E
authors.initials: ME
authors.lastname: Kızıltan
authors.forename: Ayşegül
authors.initials: A
authors.lastname: Gündüz
authors.forename: Güneş
authors.initials: G
authors.lastname: Kızıltan
authors.forename: Idris
authors.initials: I
authors.lastname: Sayılır
authors.forename: Gülçin
authors.initials: G
authors.lastname: Benbir
authors.forename: Ozlem
authors.initials: O
authors.lastname: Uyanık
mesh_terms: D000161:Acoustic Stimulation; D000368:Aged; D001767:Blinking; D001933:Brain Stem / Q000503:physiopathology; D016022:Case-Control Studies; D004244:Dizziness / Q000503:physiopathology / Q000523:psychology*; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013216:Reflex, Startle; D014202:Tremor / Q000503:physiopathology / Q000523:psychology*