Phantosmia


Phantosmia, also called an olfactory hallucination or a phantom odor, is smelling an odor that is not actually there. It can occur in one nostril or both. Unpleasant phantosmia, also called cacosmia, is more common and is often described as smelling something that is burned, foul, spoiled, or rotten. Experiencing occasional phantom smells is normal and usually goes away on its own in time. When hallucinations of this type do not improve on their own or when they keep coming back, it can be very upsetting and can disrupt an individual's quality of life.
Olfactory hallucinations can be caused by common medical conditions such as nasal infections, nasal polyps, or dental problems. It can result from neurological conditions such as migraines, head injuries, strokes, Parkinson's disease, seizures, or brain tumors. It can also be a symptom of certain mental disorders such as depression, bipolar disorder, intoxication or withdrawal from drugs and alcohol, or psychotic disorders. Environmental exposures are sometimes the cause as well, such as tobacco smoke, exposure to certain types of chemicals, or radiation treatment for head or neck cancer.
A physician can determine if the problem is with the sense of smell or taste, or if it is caused by a neurological or psychiatric disorder. Phantosmia usually goes away on its own though this can sometimes be gradual and occur over several years. When caused by an illness, it should go away when the illness resolves. If the problem persists or causes significant discomfort, a doctor might recommend nasal saline drops, antidepressant or anticonvulsant medications, local anesthesia to parts of the nose, or in very rare circumstances, surgical procedures to remove the olfactory nerves or bulbs.

Symptoms

Other olfactory disorders such as hyposmia and anosmia have been found to be a symptom of mood disorders. However, it is not known what olfactory disorders occur and if they are indeed a symptom of a depressive disorder.
It has been proposed that phantosmia may be an early sign of the neurodegenerative disease Parkinson's disease. It may also be a sign of an intracranial hemorrhage.
Other studies have also found that the symptoms of phantosmia have been alleviated after the patient has been treated for depression.
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.

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. By the age of 80, 80% of individuals develop an olfactory disorder. As well 50% of these individuals also have anosmia.

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. 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.

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 neurons malfunction and transmit incorrect signals to the brain or it may be due to the malfunction of the olfactory neurons. The central explanation is that active or incorrectly functioning cells of the brain cause the perception of the disturbing odor. Another central cause is that the perception of the phantom odor usually follows after the occurrence of seizures. The time span of the symptoms usually lasts a few seconds.
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.
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.
There are a few causes for phantosmia, but one of the most common and well-documented involves brain injury or seizures in the temporal lobe. During a temporal lobe seizure the patient rarely faints, but usually blacks out and cannot remember anything that happened during the seizure. Several people who have had these seizures did, however, recollect having phantosmia just prior to blacking out. Epilepsy is a disease characterized by seizures. In the case of phantosmia, if smelling and something else become so strongly linked, the action of "something else" occurring can induce activation of the olfactory bulb even though there was no stimulus for the bulb present. This is an example of plasticity gone awry. Those with lesions on the temporal lobe, often brought about by a stroke but also from trauma to the head, also experience these olfactory hallucinations.
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, instances 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.

Neuroblastoma

is a rare form of a malignant cancer which can start in the olfactory nerve, which is responsible for smell sensation. This cancer can become aggressive and progress into the ethmoid sinuses, brain cavity, surrounds the cribriform plate. The tumor can be tested for by performing a surgical biopsy and the possible treatment options include surgical removal of the tumor, radiation therapy and chemotherapy, which can cause damage to the olfactory system and possibly result in phantosmia, in turn.

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.
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.
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:
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 head trauma, accidents, upper respiratory infections, allergic rhinitis or chronic rhinitis. Although these may be events that have resulted in the phantom odor, studies conducted by Zilstrof have found that the majority of phantosmia patients have no previous history of head trauma and upper respiratory infections.