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Crescent Moon · 04:10 PM

Quote:

Originally Posted by growlycat

I wasn't sure where to post this, sorry if this isn't a good place. Feel free to redirect me.

My Dx is Depression and Anxiety not Psychosis or Schizophrenia. That being said, I have had intermittent experiences of smelling phantom scents, namely cigarette smoke. This has been happening off and on for a few months, and it seems to happen for a few days to a week at a time when I'm stressed more than usual.

Looking it up on line is almost funny. Why does everything have to be a brain tumor? Should I be concerned?

I read somewhere that scent is strongly connected to memory, and I am afraid that I may be closer to remembering something I don't want to.

Thoughts on olfactory hallucinations welcome!

Hi Growly -

I am in the field of neurophysiology, and encounter this kind of thing on a regular basis. Olfactory hallucinations can be caused by a number of different assaults/injuries to the brain - specifically the olfactory tract, which is quite long. This can include what we call 'space occupying lesions' (tumors, benign and malignant, and other things like scar tissue, cysts, etc). It also includes head trauma, and even something going amiss with the blood supply system of the brain, especially migraines. Schizophrenia and Simple Partial Seizures in epilepsy are probably the most common causes.

The temporal lobe of the brain is responsible for a lot of sensory information. Temporal lobe epilepsies (TLE) have symptoms that can mimic psychiatric disorders, including hallucinations that are auditory, visual, olfactory, and gustatory (taste). Other symptoms can include sensations of sudden unexplained emotions of fear, anxiety, rage, and even elation, happiness, and laughing fits. Sensations of self are not uncommon, like depersonalization, derealization, deja vu, jamais vu, just about the whole gamut of hallucinatory experiences felt by those with schizophrenia.

With respect to olfactory hallucinations, there are some characteristics that are more typical if it's a result of a simple partial seizure. First, the odor is usually an almost indescribable obnoxious smell, along the lines of something putrid, chemical-smelling, sulfur, or something burning. Second, if it's a seizure, it is usually brief, lasting anywhere from a few seconds up to a few minutes (usually under two minutes). If the hallucination lasts longer, if not schizophrenia, it's usually a more permanent injury to the brain - like tumors, head trauma, blood supply issues, etc. Third, with seizures the smell is usually consistent - in that it won't smell like flowers one time, fruit another, and like burning rubber another time. If the smell varies, it's usually still pretty close. Seizure-provoked smells can be accompanied by q variety of other sensory symptoms, such as feeling like you're in a time warp, visual hallucinations, feeling like you're 'zoned out' or even also experiencing a taste hallucination (also usually obnoxious).

Interestingly, since many antiepileptic medications (AED's) are often used for psychiatric conditions that include psychosis (Bipolar, Schizophrenia), the patient may be having simple partial seizures but it's symptoms are misinterpreted as being part of the psychiatric disorder, and the symptoms may only pop up if medication is being changed or lowered. Medications would include Lamictal, Topomax, Keppra, Depakote, Trileptal. With most other causes, like tumors or schizophrenia (sorry, I can't do 'sz' because that's the abreveation we use for 'seizure'!), anyway, with most of these other causes, the hallucination lasts longer than it does for a seizure. Seizure-caused hallucinations are typically very brief, although they can certainly happen repeatedly throughout the day or night.

People often think of epilepsy seizures as being something that involves convulsions and loss of consciousness. That's not true. Temporal lobe epilepsies are *the* most common type of epilepsy, and the ones categorized as 'simple partial' specifically do NOT involve loss of consciousness, and certainly don't involve convulsions.

And to clarify, sometimes a simple partial seizure that has sensory symptoms (like hallucinations) can evolve into more traditional generalized seizures that involve convulsions, or even what's called "complex partial" which usually result in brief loss of awareness, but the symptoms are lip smacking, finger movements like picking at clothes, eye blinking, or even something like bicycling movements of the legs. The patient might 'look' like they are awake and aware, but they will not respond during the seizure if you try to engage. Brief simple partial sensory seizures preceding more involved seizures (with loss of consciousness) are called auras. Sensory aura's before a migraine are also very common.

Determining the cause of sensory hallucinations can be difficult. An electroencephalogram (EEG) is often one of the first tests, but temporal lobe seizures, and sensory-symptom seizures are often too deep in the brain to be picked up by scalp electrodes. MRI's and CT scans can help with looking for space occupying lesions and/or blood flow problems or injury to the transmission of impulses in the brain. If nothing is found, and the symptoms are disruptive to life, AED's may be tried, and if they provide no relief, electrodes can be surgically inserted to evaluate deeper parts of the brain in order to evaluate the patient as a candidate for surgery to remove the usually very small tissue in the brain that is causing the seizures.

This may be a whole lot more than you ever wanted to know... but since you asked :-)