Olfactory nerve: symptoms and signs

Smelling is one of the first sensations that appear in a baby. From him begins the knowledge of the world around him and himself. The taste that a person feels during meals is also a result of the sense of smell, not of language, as it seemed before. Even the classics argued that our scent is able to help in a difficult situation. As JRR Tolkien wrote: "If you get lost, always go to where it smells better."

Anatomy

The olfactory nerve refers to a group of cranial, as well as nerves of special sensitivity. His origin, he takes on the mucosa of the upper and middle nasal passage. The processes of the neurosensory cells form the first neuron of the olfactory tract there.

Fifteen to twenty demyelinated fibers penetrate the cranial cavity through the horizontal plate of the trellis. There they unite into the olfactory bulb, which is the second pathway neuron. Out of the bulb, there are long nerve processes that go to the olfactory triangle. Then they are divided into two parts and immersed in the anterior perforated plate and the transparent septum. There are third neurons of the path.

After the third neuron, the path is sent to the cerebral cortex, namely to the hook region, to the olfactory analyzer. On this site, the olfactory nerve ends. Its anatomy is quite simple, which allows doctors to identify violations at different sites and to eliminate them.

Functions

The very name of the structure indicates what it is intended for. Functions of the olfactory nerve consist in catching the smell and deciphering it. They cause appetite and salivation, if the fragrance is pleasant, or, on the contrary, provoke sickness and vomiting, when the ambre leaves much to be desired.

In order to achieve this effect, the olfactory nerve passes through the reticular formation and is sent to the brain stem. There, the fibers are connected to the nuclei of the intermediate, glossopharyngeal and vagus nerves. In this area, the nuclei of the olfactory nerve are also located.

The fact is known that these or those smells cause certain emotions in us. So, to provide a similar reaction, the fibers of the olfactory nerve connect with the subcortical visual analyzer, hypothalamus and limbic system.

Anosmia

"Anosmia" translates as "lack of smell." If this condition is observed from two sides, then this is evidence in favor of the defeat of the nasal mucosa (rhinitis, sinusitis, polyps) and, as a rule, does not threaten any serious consequences. But with one-sided loss of smell, it is necessary to think about the fact that the olfactory nerve can be affected.

Causes of the disease may be an underdeveloped olfactory tract or fractures of the bones of the skull, for example, a trellis plate. The course of the olfactory nerve is generally closely related to the skeletal structures of the skull. Damage to the fibers can and splinters of the bone after a fracture of the nose, upper jaw, orbit. Damage to the olfactory bulb is also possible due to a bruise of the brain substance, when it falls to the back of the head.

Inflammatory diseases such as etmoiditis, in advanced cases, melt the trellis bone and damage the olfactory nerve.

Hyposmia and Hyperosmia

Hyposmia is a reduction in smell. It can arise because of the same reasons as anosmia:

• Thickening of the nasal mucosa;
• Inflammatory diseases;
• Neoplasms;
• Injuries.

Sometimes this is the only sign of cerebral aneurysms or a tumor of the anterior cranial fossa.

Hyperosmia (increased or heightened sense of smell), is noted in emotionally labile people, as well as in some forms of hysteria. Hypersensitivity to smells is observed in people who inhale drugs, for example, cocaine. Sometimes hyperosmia is caused by the innervation of the olfactory nerve extending over a large area of the nasal mucosa. Such people, most often, become workers in the perfume industry.

Parosmia: olfactory hallucinations

Parosmia is a perverted perception of the smell, which normally occurs during pregnancy. Pathological parosmia is sometimes observed in schizophrenia, affection of the subcortical centers of smell (paragippocampal gyrus and hook), with hysteria. In patients with iron deficiency anemia, there are similar symptoms: pleasure from the smell of gasoline, paint, wet asphalt, chalk.

The defeat of the olfactory nerve in the temporal lobe causes a specific aura in front of epileptic seizures and causes hallucinations in psychoses.

Research Methodology

In order to determine the state of smell in a patient, the neuropathologist performs special tests for recognition of various odors. Indicator aromas should not be too sharp not to violate the purity of the experiment. The patient is asked to calm down, close his eyes and press his nostril with a finger. After this, a smelling substance is gradually brought to the second nostril. It is recommended to use familiar smells for a person, but at the same time avoid ammonia, vinegar, since when inhaled, except for the olfactory, the trigeminal nerve is irritated.

The doctor records the test results and interprets them with respect to the norm. Even if the patient can not name the substance, the very fact of sensation of smell excludes the defeat of the nerve.

Brain tumors and smell

With tumors of the brain of different localization, hematomas, disturbance of the outflow of the cerebrospinal fluid and other processes that squeeze the substance of the brain or press it into the bone formations of the skull. In this case, one- or two-sided impairment of the sense of smell may develop. The doctor should remember that the nerve fibers are crossed, so even if the lesion is localized on one side, the hyposmia will be bilateral.

The defeat of the olfactory nerve is an integral part of the craniobasal syndrome. It is characterized not only by the compression of the brain substance, but also by its ischemia. Patients develop the pathology of the first six pairs of cranial nerves. Symptoms can be uneven, there are different combinations.

Treatment

Pathologies of the olfactory nerve in the first part of it are found most often in the autumn-winter period, when there is a massive incidence of acute respiratory infections and influenza. A prolonged course of the disease can cause a complete loss of smell. Recovery of nerve functions takes from ten months to a year. All this time it is necessary to conduct course treatment for stimulation of regenerative processes.

In an acute period, the ENT prescribes physiotherapeutic treatment:

• Microwave therapy of the nose and maxillary sinuses;
• Ultraviolet irradiation of the nasal mucosa, with a capacity of 2-3 bio-doses;
• Magnetotherapy of the wings of the nose and sinuses of the upper jaw;
• Infrared radiation with a frequency of 50-80 Hz.

You can combine the first two methods and the last two. This accelerates the restoration of lost functions. After clinical recovery, the following physiotherapeutic treatment is also carried out for rehabilitation:

• Electrophoresis with the use of "No-shpa", "Proserin", as well as nicotinic acid or lidase;
• Ultraphonophoresis of the nose and maxillary sinuses for ten minutes every day;
• Irradiation with a red laser spectrum;
• Endonasal electrical stimulation.

Each course of therapy is carried out for up to ten days with interruptions for fifteen to twenty days before the complete restoration of the function of the olfactory nerve.