Year : 2016 | Volume
: 6 | Issue : 3 | Page : 136--138
Olfactory hallucinations in schizophrenia: Does it carry any meaning?
Sujita Kumar Kar, Kabir Garg, Adarsh Tripathi
Department of Psychiatry, King George's Medical University, Lucknow, Uttar Pradesh, India
Dr. Sujita Kumar Kar
Department of Psychiatry, King George«SQ»s Medical University, Lucknow - 226 003, Uttar Pradesh
Olfactory dysfunctions are reported in multiple psychiatric disorders, including schizophrenia. The patterns of olfactory distortion in schizophrenia include impairments in olfactory perception, olfactory discrimination, olfactory memory, and olfactory perception threshold sensitivity. Olfactory dysfunction is believed to be an early warning sign of schizophrenia and is an important endophenotypic marker. We highlight a case of late onset acute and transient psychotic disorder with olfactory hallucination. Different implications of olfactory hallucinations in a psychotic patient are discussed with a review of the literature.
|How to cite this article:|
Kar SK, Garg K, Tripathi A. Olfactory hallucinations in schizophrenia: Does it carry any meaning?.Int J Nutr Pharmacol Neurol Dis 2016;6:136-138
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Kar SK, Garg K, Tripathi A. Olfactory hallucinations in schizophrenia: Does it carry any meaning?. Int J Nutr Pharmacol Neurol Dis [serial online] 2016 [cited 2022 Aug 8 ];6:136-138
Available from: https://www.ijnpnd.com/text.asp?2016/6/3/136/184597
Olfaction in human beings is an important modality of special sensation. It may get distorted in many physical as well as psychiatric disorders. Olfactory hallucination is a distorted perception of smell in the absence of any olfactory stimuli.  The odor perceived in olfactory hallucination is usually unpleasant, and when the hallucinatory phenomenon lasts longer than few seconds, the term "phantosmia" is used.  "Cacosmia" term is sometimes used for the unpleasant phantosmia.  Research evidence suggests that unpleasant phantosmia is usually associated with olfactory sensory deficits with more marked phantosmia in the nose with added olfactory deficit.  There is some anecdotal evidence of improvement of olfactory function with antiepileptic and antidepressant medications.  Olfactory system has a close association with frontotemporal cerebral cortex as demonstrated by olfactory probes in various studies. ,,, Frontotemporal cerebral cortex has an important role in cognitive as well as emotional processing and is also involved in schizophrenia.  Olfactory dysfunction in patients with schizophrenia can be directly correlated to this neuronal circuitry. Hence, it has been considered an early warning sign or endophenotypic marker of schizophrenia. 
In the early phase of schizophrenia as well as in asymptomatic high-risk groups, olfactory deficits in the form of impairment of olfactory perception and discrimination were evident.  Nguyen et al. have also reported about abnormal olfactory perception threshold sensitivity and odor memory deficits in schizophrenic patients in addition to the above-mentioned deficits.  Patients with schizophrenia also exhibit depolarization response abnormalities in olfactory electrophysiological evaluations, which may be due to interference in the intracellular signaling process mediated by cyclic-adenosine monophosphate in the abnormally matured or grown olfactory neurons.  Evidence also suggests that the degree of olfactory deficit is independent of the symptom severity of schizophrenia, smoking status as well as the use of antipsychotic medications. ,
A 60-year-old illiterate, homemaker from a rural lower socioeconomic family was hospitalized with acute onset of suspiciousness, irritability, reduced sleep, and active refusal of water and food for 1 month. The patient had no contributory past, personal, or family history. On probing, she reported that food and water smelled like diesel; thus, they were contaminated. Over 1-month period, the patient had reduced usage of water and would also not bathe or wash herself. At admission, her physical examination was within normal limits. She was conscious and oriented. Her investigations, including hemogram, liver and kidney function tests, were within normal limits. Her ear-nose-throat examination and magnetic resonance imaging (MRI) of the brain did not reveal any abnormality. The patient had persecutory delusions against her family members and held them responsible for contaminating water with diesel. The patient actively avoided interacting with the family members and hospital staff. She remained mostly uncooperative and also actively avoided liquids. She would accept only solid and semi-solid food items, mandating the use of intravenous fluids. The patient was diagnosed with "other acute and transient psychotic disorder" as per International Classification of Diseases-10 diagnostic criteria and started on olanzapine (titrated up to 20 mg/day).
On this treatment, the patient had improvement. She started accepting fluids orally by the end of the 2 nd week of treatment. The patient's symptoms were in remission by the 3 rd week, and she was discharged.
In our patient, persecutory delusion and olfactory hallucination developed simultaneously as reported by the family members. However, the patient was attributing her persecutory beliefs secondary to olfactory hallucination. Thus, it was possible that the olfactory symptoms developed earlier than the persecutory delusion and may have been of lesser severity, which went unreported by the elderly female or were unnoticed by the family members. The olfactory symptoms had developed before initiation of antipsychotic treatment and had been improved with treatment; hence, the possibility of drug-mediated side effect was unlikely.
As olfactory perception sensitivity is dysfunctional in schizophrenia, it has important implication in genesis of olfactory hallucination.  It may thus be considered akin to the dysfunctional thalamic filtering leading to auditory hallucinations in psychosis.
The occurrence of the first episode of psychosis in an elderly individual, without any significant family history, warrants evaluation to rule out possible organicity. However, the neurological examination including neuroimaging (MRI brain) did not reveal any abnormality. It is of note that the absence of structural brain abnormalities in MRI do not necessarily rule out disruption in the neuronal integrity, which have been found in many studies using functional neuroimaging. Hence, functional neuroimaging-guided olfactory probes may be used to detect such types of fiber neurophysiological abnormalities for research purposes.
The patient had shown significant improvement within 3 weeks of initiation of antipsychotic treatment. The olfactory hallucination as well as the persecutory delusion improved concurrently and completely resolved within a month's time. The patient did not report any difficulty in odor perception or discrimination. There were no reported olfactory deficits before onset or after the resolution of the psychosis. Hence, patient's olfactory hallucination seems to be purely, a part of psychosis, which started early in the disease process and completely resolved after the treatment; hence, it may be considered an early warning sign of psychosis.
The absence of any obvious structural brain abnormality in neuroimaging, negative family history of psychiatric disorder, presence of predominant positive symptoms, and late onset of the psychotic episode were some good prognostic factors in our case. Olfactory hallucination being a positive symptom can be considered a good prognostic factor. However, it needs to be studied whether prognostic significance of olfactory hallucination overweighs hallucinations in other modalities.
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