title: Olfactory stimulation induces delayed responses in epilepsy.
abstract: Precipitation and inhibition of seizures and epileptic discharges by sensory stimuli are receiving increasing attention because they provide insight into natural seizure generation in human epilepsies and can identify potential nonpharmacological therapies. We aimed to investigate modulation (provocation or inhibition) of epileptiform discharges (EDs) in mesial temporal lobe epilepsy (MTLE) versus idiopathic generalized epilepsy (IGE) by olfactory stimulation (OS) compared with standard provocation methods. The underlying hypothesis was that any response would be more likely to occur in MTLE, considering the anatomical connections of the temporal lobe to the olfactory system. This multicenter, international study recruited patients with either MTLE or IGE who were systematically compared for responses to OS using an EEG/video-EEG protocol including a 30-min baseline, twice 3-min olfactory stimulation with ylang-ylang, hyperventilation, and intermittent photic stimulation. The 95% confidence interval (CI) for the baseline EDs in each patient was calculated, and modulation was assumed when the number of EDs during any 3-min test period was outside this CI. A total of 134 subjects (55 with MTLE, 53 with IGE, and 26 healthy controls) were included. Epileptiform discharges were inhibited during OS in about half the patients with both MTLE and IGE, whereas following OS, provocation was seen in 29.1% of patients with MTLE and inhibition in 28.3% of patients with IGE. Olfactory stimulation was less provocative than standard activation methods. The frequent subclinical modulation of epileptic activity in both MTLE and IGE is in striking contrast with the rarity of reports of olfactory seizure precipitation and arrest. Inhibition during OS can be explained by nonspecific arousal. The delayed responses seem to be related to processing of olfactory stimuli in the temporal lobe, thalamus, and frontal cortex.
authors.affiliation: Centro de Epilepsia de Santa Catarina (CEPESC), Hospital Governador Celso Ramos (HGCR), Florianópolis, SC, Brazil.
authors.forename: Mariana S
authors.initials: MS
authors.lastname: Lunardi
authors.affiliation: Centro de Epilepsia de Santa Catarina (CEPESC), Hospital Governador Celso Ramos (HGCR), Florianópolis, SC, Brazil; Serviço de Neurologia, Departamento de Clínica Médica, Hospital Universitário, Universidade Federal de Santa Catarina (UFSC), Florianópolis, SC, Brazil; Centro de Neurociências Aplicadas (CeNAp), Hospital Universitário, Universidade Federal de Santa Catarina (UFSC), Florianópolis, SC, Brazil. Electronic address: linkatia@uol.com.br.
authors.forename: Katia
authors.initials: K
authors.lastname: Lin
authors.affiliation: Epilepsy Centre, Vilnius University Hospital Santariškių Klinikos, Vilnius, Lithuania; Clinic of Neurology and Neurosurgery, Medical Faculty, Vilnius University, Vilnius, Lithuania.
authors.forename: Rūta
authors.initials: R
authors.lastname: Mameniškienė
authors.affiliation: Danish Epilepsy Centre, Dianalund, Denmark; Aarhus University, Aarhus, Denmark.
authors.forename: Sandor
authors.initials: S
authors.lastname: Beniczky
authors.affiliation: Instituto de Neurología, Hospital de Clínicas, Universidad de la República, Montevideo, Uruguay.
authors.forename: Alicia
authors.initials: A
authors.lastname: Bogacz
authors.affiliation: Instituto de Neurología, Hospital de Clínicas, Universidad de la República, Montevideo, Uruguay.
authors.forename: Patricia
authors.initials: P
authors.lastname: Braga
authors.affiliation: Hospital São Paulo, Universidade Federal de São Paulo, São Paulo, Brazil.
authors.forename: Mirian S B
authors.initials: MSB
authors.lastname: Guaranha
authors.affiliation: Hospital São Paulo, Universidade Federal de São Paulo, São Paulo, Brazil.
authors.forename: Elza M T
authors.initials: EMT
authors.lastname: Yacubian
authors.affiliation: Vilnius University Hospital Santariškių Klinikos, Vilnius, Lithuania; Clinic of Children's Diseases, Medical Faculty, Vilnius University, Vilnius, Lithuania.
authors.forename: Rūta
authors.initials: R
authors.lastname: Samaitienė
authors.affiliation: Department of Neurology and Clinical Neurophysiology, Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey.
authors.forename: Betül
authors.initials: B
authors.lastname: Baykan
authors.affiliation: Smell & Taste Clinic, Department of ORL, TU Dresden, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Hummel
authors.affiliation: Serviço de Neurologia, Departamento de Clínica Médica, Hospital Universitário, Universidade Federal de Santa Catarina (UFSC), Florianópolis, SC, Brazil; Danish Epilepsy Centre, Dianalund, Denmark.
authors.forename: Peter
authors.initials: P
authors.lastname: Wolf
mesh_terms: D000293:Adolescent; D000328:Adult; D001921:Brain / Q000503:physiopathology*; D016022:Case-Control Studies; D004569:Electroencephalography; D004829:Epilepsy, Generalized / Q000503:physiopathology*; D004833:Epilepsy, Temporal Lobe / Q000503:physiopathology*; D005260:Female; D005625:Frontal Lobe / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D055696:Olfactory Perception / Q000502:physiology*; D013702:Temporal Lobe / Q000503:physiopathology; D013788:Thalamus / Q000503:physiopathology; D055815:Young Adult
keywords: Generalized seizures; Hippocampal sclerosis; Ictogenesis; Olfactory stimulation; Reflex seizures; System epilepsies