Phantosmia
Phantosmia (phantom smell), also called an olfactory hallucination or a phantom odor,[1] is smelling an odor that is not actually there. This is intrinsically suspicious as the formal evaluation and detection of relatively low levels of odour particles is itself a very tricky task in air epistemology. It can occur in one nostril or both.[2] Unpleasant phantosmia, cacosmia, is more common and is often described as smelling something that is burned, foul, spoiled, or rotten.[3] Experiencing occasional phantom smells is normal and usually goes away on its own in time.[4] When hallucinations of this type do not seem to go away or when they keep coming back, it can be very upsetting and can disrupt an individual's quality of life.[2]
Olfactory hallucinations can be caused by common medical conditions such as nasal infections,
A physician can determine if the problem is with the sense of smell (
Symptoms
Other olfactory disorders such as hyposmia and anosmia have been found to be a symptom of mood disorders (depression). However, it is not known what olfactory disorders occur and if they are indeed a symptom of a depressive disorder.[5] It has been proposed that phantosmia may be an early sign of the neurodegenerative disease Parkinson's disease.[6] It may also be a sign of an intracranial hemorrhage[7] (brain tumours or epilepsy).[8] Other studies have also found that the symptoms of phantosmia have been alleviated after the patient has been treated for depression.[9][10] Another case of a 70-year-old male reported that his first abnormal symptoms were irregular bowel movements. After this the patient developed irregular eye movements and had developed a sleep and behavior disorder. He subsequently developed phantosmia, in which what he smelled was described as "stinky and unpleasant". The patient did not display any of the following symptoms: loss of awareness; confusion; automatisms; convulsive seizures; auditory/visual hallucinations.[3]
Co-occurrence with other conditions
Phantosmia has been found to co-exist in patients with other disorders such as schizophrenia, epilepsy, alcoholic psychosis, and depression. It has also been found that many patients may begin to experience depression after the occurrence of phantosmia and have looked towards committing suicide. The occurrence of depression resulted from the severe symptoms of phantosmia as everything even food smelled spoilt, rotten and burnt for these patients.[3] By the age of 80, 80% of individuals develop an olfactory disorder. As well 50% of these individuals also have anosmia.[11]
Migraines
In 2011 Coleman, Grosberg and Robbins did a case study on patients with olfactory hallucinations and other primary headache disorders. In their 30-month long study, the prevalence rates for phantosmia turned out to be as low as 0.66%.
In their findings, it was observed that a typical hallucination period was of 5–60 minutes, occurred either before or with the onset of head pain, and typically consisted of an unpleasant odor. It was also noted that phantosmia occurs most commonly among women having a migraine complaint.[12] In their study, prophylactic therapy for headaches helped cure phantosmia in most of the patients.
This finding is consistent with the findings of Schreiber and Calvert in 1986 which also mentioned the olfactory hallucinations before the occurrence of a migraine attack in four of their subjects.[13]
Causes
The cause of phantosmia can be either peripheral or central, or a combination of the two. The peripheral explanation of this disorder is that rogue
Other studies on phantosmia patients have found that the perception of the odor initiates with a sneeze, thus they avoid any nasal activity. It has also been found that the perception of the odor is worse in the nostril that is weaker in olfaction ability. It has also been noted that about a quarter of patients with phantosmia in one nostril will usually develop it in the other nostril as well over a time period of a few months or years.[3]
Several patients who have received surgical treatment have stated that they have a feeling or intuition that the phantom odor is about to occur, however it does not. This sensation has been supported by positron emission tomography, and it has been found that these patients have a high level of activity in their contralateral frontal, insular and temporal regions. The significance of the activity in these regions is not definitive as not a significant number of patients have been studied to conclude any relation of this activity with the symptoms. However the intensity of the activity in these regions was reduced by excising the olfactory epithelium from the associated nasal cavity.[15]
There are a few causes for phantosmia, but one of the most common and well-documented involves brain injury or
Other leading causes of phantosmia include neurological disorders such as schizophrenia and Alzheimer's disease. Both of these disorders have well documented cases of hallucinations, most commonly visual and auditory. Both also, however, have instances of phantosmia too, although not as frequently. In both cases, incidences[spelling?] of olfactory delusions are more common, especially in Alzheimer's, where it is exceedingly difficult to convince the patient that these are in fact hallucinations and not real. Specifically in Alzheimer's disease, atrophy in the temporal lobe has been known to occur. As evidenced in trauma and seizures, phantosmia is strongly associated with this area; leading to its appearance in some Alzheimer's patients. Parkinson's disease patients can also experience phantosmia, as well as parosmia, however their appearance is less common than the muscle tremors the patients experience.[16]
Neuroblastoma
Development
The complaints of phantosmia involving the perception of unpleasant odors most commonly include "burnt", "foul", "rotten", "sewage", "metallic" or "chemical". Sometimes the odor is described as exhaust fumes. These odors may be triggered by strong odorants, changes in nasal airflow, or even loud sounds. Sometimes they occur spontaneously. Patients having complaints of phantosmia might self-admit a poor quality of life, with each meal having the unpleasant odor as well. The disorder's first onset, usually spontaneous, may last only a few minutes. Recurrences may gradually increase from monthly, then weekly, and then daily over a period of six months to a year. The duration of the perceived odor may also increase over the same time, often lasting most of a day after one year.[18] Some patients also state that the odor they smell is different from any known odor.
Diagnosis
The most challenging task for the examiner is to determine and obtain the correct symptoms and associate them with one of the olfactory disorders, as there are several of them and they are related to each other.
The first step the examiner usually takes is to investigate if the problem is olfactory or gustatory related. As it may be that the patient releases certain bodily odors that are causing them to have this perception.[19]
If the examiner is able to confirm that the problem is olfactory related, the next step is to determine which olfactory disorder the patient has. The following is a list of possible olfactory disorders:
- anosmia
- hyposmia
- hyperosmia
- dysosmia
- parosmia or troposmia
- phantosmia
The second step is difficult for both the examiner and the patient as the patient has some difficulty describing their perception of the phantom odor. Furthermore, the patient is in a position of stress and anxiety thus it is crucial that the examiner be patient.
After determining the nature of the disorder, and confirming phantosmia, the examiner must then have the patient describe their perception of the phantom odor. In many cases, patients have described the odor to be that of something burning and rotten and have described it to be unpleasant and foul.
The third step for the examiner is to determine the health history of the patient to take note of
Treatment
Due to the rareness of the disorder there is no well-defined treatment. Sometimes the patients are just told to live with the disorder or the patients end up performing "stereotypical methods" that might help in reducing the severity of the odor. This might include forced crying, bending over holding knees while holding breath, rinsing the nose with saline water and gagging. All these behaviours at the end fail to resolve the hallucination. Various treatments like
One of the surgical treatments proposed has included olfactory bulb ablation through a bifrontal craniotomy approach.[21][22] But a counter-argument by Leopold, Loehrl and Schwob (2002) has stated that this ablation process results in a bilateral permanent anosmia and includes risks associated with a craniotomy. According to them, the use of transnasal endoscopic exhibition of olfactory epithelium is a safe and effective treatment for patients with unremitting phantosmia with the olfactory function being potentially spared. It is also cautioned that the surgery is challenging one and is associated with major risks, and that it should be restricted to expertise centres.[18]
On the other hand, many cases have also reported that the strength of their symptoms have decreased with time. (Duncan and Seidan, 1995) A case involving long term phantosmia has been treated with the use of an anti depressive medication by the common name Venlafaxine (Effexor). The relation between mood disorders and phantosmia is unknown, and is a widely researched area. In many cases, the symptoms of phantosmia have been reduced by the use of anticonvulsants and antidepressants that act on the central and peripheral neurons.
The most commonly used treatment method is the removal of the olfactory epithelium or the bulb by means of surgery to alleviate the patient from the symptoms. Other traditional methods include the use of topical anesthetics (Zilstorff-Pederson, 1995) and use of sedatives.[3]
Nasal spray
Many patients seeking a quick form of relief achieved it by rinsing the nose with a saline solution. This treatment option is easily available and can be repeated several times throughout the day to obtain relief. An example of a nasal spray that can be used to alleviate symptoms is Oxymetazoline HCl, which seems to provide relief for a longer time period. The relief achieved by the use of nasal sprays seems to be because it results in the blockage of the nostril that does not allow any air to enter the olfactory cleft.[3]
Topical solutions
Another treatment option is the topical solution of
Venlafaxine
This antidepressant medication is a serotonin norepinephrine reuptake inhibitor (SNRI). In the case study of a 52-year-old female with phantosmia for 27 years, a dose of 75 mg a day relieved and eliminated her symptoms. The drug was prescribed initially in order to treat her depression.[5]
Occurrence
Phantosmia is most likely to occur in women between the ages of 15 and 30 years. The duration of the first hallucination(s) is likely to be from five to twenty minutes. It has also been found that the second hallucination is likely to occur approximately a month later in the same manner as the first. Over time, the length of the hallucination(s) may begin to increase.[15]
Pregnancy
A
Case studies
Surgical treatment with the preservation of olfactory ability
A 26-year-old woman was diagnosed with
The woman consulted many medical practitioners but could not receive a reliable diagnosis. She was prescribed medications including nasal steroid sprays and other drugs, but they would not relieve her of her headaches and phantosmia symptoms. Through chemosensory evaluation, it was found that her senses of smell and taste were working normally. Due to some phantosmias believed to be caused by a blockage causing the odor molecules to not reach the olfactory receptors, doctors surgically widened the olfactory cleft. Unfortunately, the phantosmia symptoms remained. Further unsuccessful treatment included a long-term disruption of the axonal projections from the primary
The patient was successfully treated with a surgical procedure involving permanent disruption of the olfactory epithelium. This was accomplished with the surgical excision of a "plug" of olfactory epithelium from the area of the cribriform plate. This excision was meant to sever all the fila olfactoria entering the central nervous system from her left nostril. Five weeks after surgery, the woman reported a complete absence of her phantosmia symptoms, and her olfactory ability was maintained (Hornung et al. 1991).[3]
Drug treatment
For a 52-year-old woman, phantosmia occurring as fluctuating episodes occurred for a period of 27 years, and there was no discernible reason for the onset of symptoms. She could weaken the symptoms by rinsing her nose with a saline solution, and by going to sleep. The smells she would encounter often were very unpleasant, resembling a burnt and rotten fruity odor. When her family doctor prescribed her the antidepressant venlafaxine, she noticed that the drug resulted in the complete elimination of her phantosmia symptoms. This discovery has caused scientists and doctors to research if a link between phantosmia and mild depressive disorders exists, and this idea is supported by the reported improvement of phantosmia after repeated transcranial stimulation used to treat depression.[25]
Co-morbidity with Parkinson's disease
In the case of a 57-year-old woman, strong olfactory sensations were reported, ranging from odors of perfume to slightly unpleasant odors of "wet dog". The episodes experienced would last between seconds and hours and would occur multiple times per day. The patient would report phantosmia symptoms, but would correctly identify known odors and would claim to have no symptoms of smell loss. She had no history of epilepsy, and her electroencephalographic results were normal. Later on, while the symptoms of phantosmia were decreasing, she developed severe symptoms of Parkinson disease. While the patient was treated for her tremors with
In the case of a 52-year-old woman, the first symptoms of phantosmia reported appeared to the woman as an increased sense of smell. She believed to have the ability to detect odors before other people, and with better accuracy. She later began to experience the typical symptoms of phantosmia and would smell things that she could recognize in the absence of any odor producing molecules. The reported smells were of perfumes, candles, and fruits, however the woman could not accurately identify what type of perfume or fruit she was smelling. Her phantosmia episodes would occur abruptly and would last from minutes to half an hour. A rhinologic examination came back with normal results. When her phantosmia symptoms began to dissipate, she began to complain of clumsiness, slowness, and problems with her left hand that would alternate between tremors and rigidity. A neurologic examination revealed symptoms of Parkinson's disease.[6]
See also
Related disorders
- Anosmia
- Dysosmia
- Hyperosmia
- Hyposmia
- troposmia)
Other
- Odorant-binding protein
- Odorant receptor
- Olfactory bulb mitral cell
- Olfactory receptor neuron
- Olfactory tubercle
References
- ^ "That stinks! 1 in 15 Americans smell odors that aren't there". National Institutes of Health (NIH). National Institute on Deafness and Other Communication Disorders. National Institute on Deafness and Other Communication Disorders. August 16, 2018. Retrieved 23 August 2018.This article incorporates public domain material from websites or documents of the National Institutes of Health.
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- ^ a b c Leopold DA, Myerrose G (1994), "Diagnosis and treatment of distorted olfactory perception", in Kuriha K, Suzuki N, Ogawa H (eds.), Olfaction and Taste XI, Tokyo, Japan: Springer-Verlag, pp. 618–622
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Further reading
- Keller, Andreas & Malaspina, Dolores (2013). "Hidden Consequences of Olfactory Dysfunction", in: BMC Ear Nose Throat Disorders 13:8
- Levitan EB, Kaczmarek LK (2002). The Neuron: Cell and Molecular Biology (3rd ed.). New York: Oxford University Press. ISBN 978-0-19-514523-6.
- Sobol S, Frenkiel S, Mouadeb D (2002). Olfactory dysfunction (PDF). Canada: The Canadian Journal of Diagnosis.
- Andrews JG (2009). "A Pungent Life: The Smells in My Head". The New York Times. New York.
External links
- Mayo Clinic - What causes olfactory hallucinations (phantosmia)?
- Medscape, August 2018 - First Prevalence Data on 'Phantom Odors' Show Women Often Affected
- JAMA Network, September 2018 - Factors Associated With Phantom Odor Perception Among US Adults: Findings From the National Health and Nutrition Examination Survey