Smell and taste disorders

Many neurological disorders cause smell and taste disorders. The olfactory and gustatory nerves are not next to each other, but the functions of smell and taste are closely related.


Not being able to smell anymore
Permanent or temporary loss of smell (anosmia) occurs when the olfactory nerves are damaged by the brain injury.
In addition, the brain area (middle part of the temporal lobe/temporal lobe) that is responsible for the perception of odors may be damaged
(sensorineural disorder). Finally, the brain stem may be damaged and no longer transmit sensory perception.
There are people whose sense of smell recovers slowly or intermittently, but there are also people for whom this is not the case. That depends on the nature of the injury.


No longer recognize smell or taste
With some brain injuries, a person can no longer recognize/identify the smell or taste. That's called olfactory agnosia. This does not involve memory loss. The senses are still intact.

For example, a person will smell gas, but does not know its meaning, so he or she will not remember to turn off the gas tap.


Smelling too much and tasting too much
With sensory overstimulation, a person can smell too much and taste too much. Odors can become unbearable. Examples include perceiving perfume, food smells, body odor, street air, etc. too strongly.


The food tastes so different
Brain damage can also cause food to taste different and it also happens that people like different things than before the injury. This can sometimes lead to (rapid) weight loss.


Being able to enjoy
Without smell, all food seems tasteless and bland.

Scent is necessary to distinguish taste. Without smell and taste you lose the ability to enjoy food, drinks and pleasant smells.

Imagine the impact of no longer being able to enjoy your food. Why would you go to a restaurant? Would you still cook or bake a cake? Wouldn't you really miss the smell of forest, sea, flowers, freshly mown grass?


Smell and taste have an important signaling function. They warn of spoiled food, smells of fire, gas, potentially dangerous chemicals and gases, and so on.


Ethmoid bone

The top of the nasal cavity is formed by a bone that separates the brain from the nasal cavity. That bone is called the ethmoid bone. Outgrowths of nerve cells together form the olfactory nerve.
A break in the ethmoid bone or an abscess or malignant tumor near this bone leads to damage to the olfactory nerves. Taste nerve fibers, which are connected to the gustatory nerves (facial nerve and glossopharyngeal nerve) travel via the brain stem to the brain, to the temporal lobe.
In the event that a tumor was the cause of loss of smell and taste, surgical removal of this tumor unfortunately cannot bring back the taste and smell.


Neurological causes


Explanation of words


Related to odor

  • Anosmia - Inability to perceive olfactory stimuli
  • Cocosmia - An unpleasant wrong taste or smell
  • Hyposmia - Decreased ability to perceive olfactory stimuli
  • Hyperosmia - Increased ability to perceive olfactory stimuli
  • Dysosmia - Altered perception of olfactory stimuli
  • Euosmia - Tasting a pleasant wrong taste or smelling odor
  • Parosmia - Tasting the wrong taste or smelling the wrong odor
  • Phantosmia - Tasting or smelling something without a source present
  • Olfactory agnosia - Inability to identify/classify olfactory stimulus


Related to taste

  • Ageusia - Inability to perceive taste stimuli
  • Hypogeusia - Reduced ability to perceive taste stimuli
  • Hypergeusia - Increased ability to perceive taste stimuli
  • Dysgeusia - Altered perception of taste stimuli
  • Taste agnosia - Inability to identify/classify taste stimulus



In parosmia, a distinction is made between experiencing an unpleasant incorrect smell or taste (cacosmia), or a pleasant but incorrect taste or smell (euosmia).

Well-known triggers for the occurrence of parosmia are coffee, meat, onion, toothpaste.
Loss of sense of smell and taste can occur with a viral infection.
When tasting and smelling recover, parosmia, the experience of an inappropriate taste and smell, is the first to disappear.
The sudden loss of taste and sense of smell is a well-known symptom of COVID-19 infection.
Phantosmia, research showed, mainly occurred among people after a previous traumatic head injury, and among people diagnosed with a psychiatric illness, people familiar with temporal epilepsy and people familiar with the occurrence of episodes of disturbed smell or taste sensation prior to to epileptic seizures.


The website of Abscent provides interesting information.


Umami: Van Nieuw Amerongen, 1994; Lindemann, 1996; Spielman, 1998 en Ackerman en Kasbekar, 1997; Spielman, 1998

Farbman, Injury-stimulated neurogenesis in sensory systems. Adv Neurol 1997; 72: 157-161, Mott, Leopold. Disorder in taste and smell. Med Clin North America 1991; 75: 1321-1353,, Small DM, Gerber JC, Mak YE, Hummel T. Differential neural responses evoked by orthonasal versus retronasal odorant perception in humans. Neuron. 2005 Aug 18;47(4):593-605

A report on the results of a study by AbScent, a patient advocacy group for people with reduced sense of taste and smell.See