title: Olfactory event-related potentials in patients with brain tumors.
abstract: OBJECTIVE
  The aim of the study was to determine how odor processing is altered in patients with unilateral supratentorial brain tumors.
  
  
  METHODS
  Olfactory event-related potentials (OERPs) were evaluated in 10 patients with unilateral brain tumors of the frontal or temporal lobe in response to linalool and allylcaproate. Both odors were presented monorhinally by a constant-flow olfactometer. In addition, 20 healthy subjects were examined. While sniffing, the subjects were asked to discriminate the two odors. EEG was recorded from 7 electrode positions (Fz, Cz, Pz, F3/4, P3/4). Amplitudes and latencies of 3 peaks (N1, P2, P3) were measured. To control for effects of modality-non-specific alterations on the olfactory components acoustic event-related potentials (AERPs) were registered by use of an oddball paradigm.
  
  
  RESULTS
  Patients with right-sided lesions showed distinct deficits in the discrimination task after stimulation of the right and left nostril. In contrast, patients with left-sided lesions only had an attenuation of correct reactions after left-sided stimulation. In the OERPs, patients with right-sided lesions showed P2- and P3-components with decreased amplitudes at parietal electrode positions. These alterations appeared after ipsi- and contralateral stimulation. Patients with left-sided lesions showed a significant effect of the side of stimulation. Their OERP-amplitudes were decreased after left-sided stimulation but not after right-sided stimulation. After right-sided olfactory stimulation a correlation between the olfactory and the acoustic ERP was seen in patients with right-sided lesions.
  
  
  CONCLUSIONS
  Olfactory performance of the participating patients was markedly reduced. Patients with right-sided lesions showed bilateral impairment, which would support the importance of the right hemisphere in olfaction. The alteration of the topographic distribution of P2- and P3-amplitudes in patients with right-sided lesions might reflect an impairment of early and late olfactory processing steps.
authors.affiliation: Department of Neurosurgery, University of Kiel, Kiel, Germany. gottwaldb@nch.uni-kiel.de
authors.forename: C
authors.initials: C
authors.lastname: Daniels
authors.forename: B
authors.initials: B
authors.lastname: Gottwald
authors.forename: B M
authors.initials: BM
authors.lastname: Pause
authors.forename: B
authors.initials: B
authors.lastname: Sojka
authors.forename: H M
authors.initials: HM
authors.lastname: Mehdorn
authors.forename: R
authors.initials: R
authors.lastname: Ferstl
mesh_terms: D000080462:Acyclic Monoterpenes; D000293:Adolescent; D000328:Adult; D001932:Brain Neoplasms / Q000150:complications* / Q000503:physiopathology; D002208:Caproates / Q000494:pharmacology; D004569:Electroencephalography; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D005625:Frontal Lobe; D007839:Functional Laterality; D006801:Humans; D007306:Insecticides / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D039821:Monoterpenes; D000857:Olfaction Disorders / Q000209:etiology; D010944:Plants; D012903:Smell / Q000502:physiology*; D013702:Temporal Lobe; D013729:Terpenes / Q000494:pharmacology
chemical_list: D000080462:Acyclic Monoterpenes; D002208:Caproates; D007306:Insecticides; D039821:Monoterpenes; D013729:Terpenes; C016972:allyl caproate; C018584:linalool