title: Differences between orthonasal and retronasal olfactory functions in patients with loss of the sense of smell.
abstract: OBJECTIVE
  To investigate differences between orthonasal and retronasal olfaction in patients with loss of the sense of smell without taste complaints.
  
  
  METHODS
  Electrophysiological and psychophysical testing of orthonasal and retronasal olfactory functions.
  
  
  METHODS
  Outpatient clinics.
  
  
  METHODS
  A series of 18 patients who had olfactory loss due to various reasons but no "taste" complaints.
  
  
  METHODS
  Orthonasal and retronasal olfactory functions assessed by olfactory event-related potentials and psychophysical smell tests.
  
  
  RESULTS
  Psychophysical testing revealed retronasal olfaction to be normal or slightly altered, whereas orthonasal olfaction was either absent or severely compromised. Findings from nasal endoscopic examinations and computed tomographic scans were within the reference range in all subjects. In response to orthonasal stimulation there were neither detectable olfactory event-related potentials nor any with small amplitudes, whereas olfactory event-related potentials in response to retronasal stimulation were clearly present in some patients.
  
  
  CONCLUSIONS
  These clinical observations, together with the psychophysical and electrophysiological findings, suggest that orthonasal and retronasal olfaction might be processed differently.
authors.affiliation: Rhinology-Olfaction Unit, Department of Otorhinolaryngology, University Hospital of Geneva, Geneva, Switzerland.
authors.forename: Basile Nicolas
authors.initials: BN
authors.lastname: Landis
authors.forename: Johannes
authors.initials: J
authors.lastname: Frasnelli
authors.forename: Jens
authors.initials: J
authors.lastname: Reden
authors.forename: Jean Silvain
authors.initials: JS
authors.lastname: Lacroix
authors.forename: Thomas
authors.initials: T
authors.lastname: Hummel
mesh_terms: D000328:Adult; D000368:Aged; D004594:Electrophysiology; D005260:Female; D005858:Germany; D006801:Humans; D008297:Male; D008875:Middle Aged; D009666:Nose / Q000503:physiopathology*; D000857:Olfaction Disorders / Q000503:physiopathology* / Q000523:psychology; D011603:Psychophysiology; D013557:Switzerland