Phantosmia

Smelling of an odor not actually there

Phantosmia (phantom smell)<! 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. 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. 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 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 (brain tumours or epilepsy). 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.

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.

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.

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.

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.

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 prophylaxis have been suggested but more research is needed for its confirmation. Also, due to being a poorly understood disorder, and having analogies to some psychiatric conditions, some patients are told that they have a mental illness. One of the surgical treatments proposed has included olfactory bulb ablation through a bifrontal craniotomy approach. 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. It has also been found that 75% of women alter their diets during pregnancy. Further research is being conducted to determine the mechanism behind food cravings during pregnancy.

A 26 year old woman was diagnosed with mononucleosis at the age of 18. After this diagnosis she began to experience headaches on the right side of her head, and phantosmia in her left nostril that would often occur together. The olfactory hallucination reported by the woman was an unpleasant mixture of vinegar, fecal material, and rotten eggs. This would happen every day beginning in the morning, and the symptoms would worsen during the few days before her menstrual period. If the symptoms did not occur in the morning, they would be triggered by strong olfactory stimuli or by loud noises. Occasionally she could avoid the phantosmia symptoms by forcing herself to sneeze. 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 olfactory sensory neurons onto the olfactory bulb. This was accomplished by intranasal irrigation with zinc sulfate. 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).

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 pramipexole, amantadine hydrochloride, levodopa, carbidopa and entacapone, the phantosmia symptoms disappeared completely. 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.