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Brain Sci. 2013, 3(4), 1483-1553; doi:10.3390/brainsci3041483

Olfactory Hallucinations without Clinical Motor Activity: A Comparison of Unirhinal with Birhinal Phantosmia

1
Center for Molecular Nutrition and Sensory Disorders, The Taste and Smell Clinic, 5125 MacArthur Blvd, NW, Suite 20, Washington, DC 20016, USA
2
Department of Neurology, The George Washington University Medical Center, 2150 Pennsylvania Avenue, NW, 7th Floor, Washington, DC 20037, USA
3
Department of Radiology, The George Washington University Medical Center, 900 23rd Street, NW, Washington, DC 20037, USA
These authors contributed equally to this work.
*
Author to whom correspondence should be addressed.
Received: 26 June 2013 / Revised: 11 October 2013 / Accepted: 12 October 2013 / Published: 15 November 2013
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Abstract

Olfactory hallucinations without subsequent myoclonic activity have not been well characterized or understood. Herein we describe, in a retrospective study, two major forms of olfactory hallucinations labeled phantosmias: one, unirhinal, the other, birhinal. To describe these disorders we performed several procedures to elucidate similarities and differences between these processes. From 1272, patients evaluated for taste and smell dysfunction at The Taste and Smell Clinic, Washington, DC with clinical history, neurological and otolaryngological examinations, evaluations of taste and smell function, EEG and neuroradiological studies 40 exhibited cyclic unirhinal phantosmia (CUP) usually without hyposmia whereas 88 exhibited non-cyclic birhinal phantosmia with associated symptomology (BPAS) with hyposmia. Patients with CUP developed phantosmia spontaneously or after laughing, coughing or shouting initially with spontaneous inhibition and subsequently with Valsalva maneuvers, sleep or nasal water inhalation; they had frequent EEG changes usually ipsilateral sharp waves. Patients with BPAS developed phantosmia secondary to several clinical events usually after hyposmia onset with few EEG changes; their phantosmia could not be initiated or inhibited by any physiological maneuver. CUP is uncommonly encountered and represents a newly defined clinical syndrome. BPAS is commonly encountered, has been observed previously but has not been clearly defined. Mechanisms responsible for phantosmia in each group were related to decreased gamma-aminobutyric acid (GABA) activity in specific brain regions. Treatment which activated brain GABA inhibited phantosmia in both groups.
Keywords: phantosmia; hallucination; aura; olfaction; taste; phantageusia; epilepsy; Valsalva; GABA; brain plasticity phantosmia; hallucination; aura; olfaction; taste; phantageusia; epilepsy; Valsalva; GABA; brain plasticity
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).

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MDPI and ACS Style

Henkin, R.I.; Potolicchio, S.J.; Levy, L.M. Olfactory Hallucinations without Clinical Motor Activity: A Comparison of Unirhinal with Birhinal Phantosmia. Brain Sci. 2013, 3, 1483-1553.

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