Vestibular syndrome in a cat. Central vestibular apparatus. Causes of nystagmus in cats

Hello, Anastasia! The causes of incoordination can be different, ranging from brain damage to liver and kidney pathologies. Read about possible reasons oh below, but I advise you to still contact to a good veterinarian and examine your pet.

A sudden loss of coordination of movements is explained by a disease of the balance organs and is called “vestibular syndrome of dogs (or cats).” The symptoms can look frightening: an apparently healthy animal suddenly cannot rise to its feet, falls, flounders, and looks frightened. There may also be drooling, vomiting, and rapid breathing. The head is tilted to the side, the muzzle is asymmetrical. The first thing that comes to mind in such cases is that the animal is having a stroke. But a stroke is perhaps the most rare reason listed symptoms. More often similar manifestations are caused by disruption of the balance organs located outside the brain - the so-called peripheral vestibular syndrome.

The causes of peripheral vestibular syndrome are as follows:

Inflammation of the middle and inner ear(otitis) - most common reason peripheral vestibular syndrome. The organ of balance - the labyrinth of the cochlea - is inextricably linked with the organ of hearing. Inflammation during otitis media can spread to the cochlear labyrinth and cause disruption of its functioning. In this case, treatment should include antibiotics and anti-inflammatory drugs. Dealing with this disease can take a lot of time and effort. Symptoms of vestibular disorder disappear within 10-14 days. When treating otitis media, the use of ototoxic drugs such as chlorhexidine and aminoglycoside antibiotics should be avoided.

Neoplasms (tumors, polyps, cysts) of the inner ear, eustachian tube, eardrum. To diagnose these formations, conventional examination and otoscopy are not enough, but additional methods visual diagnostics and cytological analysis. Most effective method tumor treatment - surgical.

Idiopathic vestibular syndrome is the second most common cause of balance problems. In cats, this disease occurs most often during the summer months. Cats of all ages are affected. Dogs get sick more often at older ages and regardless of the time of year. 72 hours after the onset of symptoms, a significant improvement occurs - nystagmus (rhythmic movements) almost disappears eyeballs) and nausea, appetite appears, and the ability to walk. After 7 days the animal can move normally. The head tilt can be maintained for more long time- up to 2 months. Specific treatment not developed. Recovery occurs without treatment, but recurrence of the disease is possible.

Use of ototoxic drugs (aminoglycoside antibiotics, chlorhexidine, metronidazole)

Congenital anomalies The development of the organ of hearing and balance is described in such breeds as: German Shepherd, Doberman, English cocker- spaniel, beagle, Siamese, Burmese cat and some others. Congenital disorders appear from birth or at 3-4 weeks of age. Some animals live with this disorder their entire lives. In some cases, spontaneous recovery occurs within 3-4 one month old. No treatment has been developed.

Temporal bone injury.

Let us remember that above we discussed diseases that do not affect the brain. This is the most common cause of sudden loss of coordination in pets. Less commonly, vestibular disorders are a consequence of diseases affecting the brain. Symptoms of imbalance that occur when these structures are affected are called central vestibular syndrome.

The causes of central vestibular disorders are the following diseases:

Infectious diseases of the brain: canine plague, infectious peritonitis cats (FIP), toxoplasmosis, cryptococcosis.

Inflammatory diseases of the nervous system: granulomatous meningoencephalomyelitis, necrotizing meningoencephalomyelitis.

Brain tumors - meningiomas, lymphomas.

Vascular diseases of the brain: ischemic, hemorrhagic stroke as a result of hypertension, hormonal disorders, sepsis, bleeding disorders, cerebral thrombosis.

Almost everyone knows that the eyes can accurately determine the health status of an animal. If they are clean and clear, then the cat is probably fine. But what if your pet’s eyes periodically twitch from side to side, although he doesn’t seem to be looking anywhere? This phenomenon is called nystagmus. In a cat, its appearance sometimes indicates the presence of some pathologies, but in some cases this phenomenon does not pose a danger.

Rhythmic, oscillating eye movements are called nystagmus. As a rule, they move exclusively in the horizontal plane. Vertical nystagmus is much less common... and is almost always a symptom of serious brain damage. Thus, nystagmus may be a normal physiological response or the result of pathology.

Why does it even arise, what do these erratic movements of the eyeballs mean? The eyes play a very important role in maintaining the balance of the body in space. They are directly connected to other organs of the vestibular apparatus. We can say that the brain checks the “sensor readings” by comparing information from the vestibular system with the data it receives from the eyes. Such a complexly organized system allows cats to maintain balance in any conditions. Judging by the number of comparisons between dexterous people and cats, the animal body is fully capable of this.

Unfortunately, nothing is perfect in the world, and therefore even such a system can be overloaded with information and “fooled.” You yourself could encounter this by going too far with visiting carousels. The fact is that the brain and all analyzers adapt to constant rotation, and by inertia they continue to “feel” it even after the attraction has already stopped. At this moment, if you look at the person, you can see classic nystagmus. But why does this phenomenon occur in cats? They don't ride on carousels, do they?!

Read also: Urinary incontinence in cats

Nystagmus in animals can be congenital or acquired. By the way, congenital pathology this type is exclusively characteristic of Siamese cats. In the second case, the cause of its occurrence is some kind of injury or, possibly, a disease that has a detrimental effect on the state of the cat’s nervous system. Sometimes this leads to this severe stress. For example, the birth of kittens. Childbirth in a cat with nystagmus proceeds normally, and soon the pathology disappears on its own.

Today, veterinarians clearly identify several factors that contribute to the occurrence of nystagmus in adult animals:

• Albinism. In this case, problems with retinal pigmentation are observed, which has a negative effect on visual function.

• Eye diseases. Cataracts, dry keratocojunctivitis and simply - all this can contribute to the development of pathology.

• Inflammation of the inner ear. Everything is clear here: if a key organ of the vestibular system fails, nothing good can be expected.

• Brain lesions.

• Some drugs used to treat neurological disorders.

Sometimes a phenomenon occurs when a kitten has a curved “swan” neck and nystagmus. As a rule, this pathology develops between four months and a year (according to age). Most often, the pathology disappears spontaneously. The causes of nystagmus in cats are still not fully understood.

Functionally, the vestibular system consists of two parts(Fig. 1) - peripheral (outside the brain stem) and central (located in the brain stem and cerebellum). Determining the location (peripheral or central vestibular syndrome) is very important stage in the diagnosis of patients with vestibular disorders.

The peripheral part of the vestibular apparatus (Fig. 2, 3) is located in the petrous part of the temporal bone (bone labyrinth). The bony labyrinth consists of the semicircular tubules, the vestibule and the cochlea (which takes part in the formation of hearing). Inside the bony labyrinth there is a membranous (membranous) labyrinth. The space between the walls of the bony and membranous labyrinth is filled with a fluid - perilymph, whose properties are similar to cerebrospinal fluid. Inside the membranous labyrinth there is another type of fluid called endolymph.
The three semicircular tubules are located at right angles to each other. Each semicircular canal at one end has an extension - an ampulla, in which receptor cells are located (ciliated cells extending their villi into a jelly-like structure - the cupula). When the endolymph in the semicircular tubules moves, the cupula also moves and displaces the villi, and the dendritic endings of the sensory neurons of the 8th pair of cranial nerves (CN) are stimulated.
The utriculus and sacculus also contain a receptor organ - the macula, which is covered with ciliated cells. The cilia extend into a jelly-like structure (otolithic membrane) and are embedded in crystals (otoliths). As the otolithic membrane moves relative to gravity, the villi are displaced and an action potential is generated.
Nerve fibers, extending from nerve cells semicircular tubules and sacs, gather into nerve bundles and exit through the internal ear canal together with the facial nerve into the cranial cavity (in the rostral part medulla oblongata). The combination of vestibular and auditory axons at this level form the 8th pair of cranial nerves. The axons then enter the brainstem at the level of the trapezius body and caudal cerebellar peduncles.

After entering the brainstem, the axons travel in different directions. Most axons form synapses with the vestibular nuclei (Fig. 4). A small amount of the axons bypass the vestibular nuclei and reach the cerebellum through the caudal cerebellar peduncles. Some axons form synapses in the fastigial nucleus of the cerebellum, others ascend to the cerebellar cortex, in the flocculonodular lobe.
There are 4 vestibular nuclei on each side of the brain stem. They are located on the ventral wall of the 4th cerebral ventricle. Axons from these nuclei extend into the spinal cord (lateral vestibulospinal tract) and rostrally into the brainstem (medial longitudinal fasciculus).
Fibers of the vestibulospinal tract influence the tone of the extensors of the limbs.
The medial longitudinal fasciculus passes rostrally (axons end in the nuclei of the cranial nerves III, IV, VI and influence the position of the eyes) and caudally into the spinal cord (forms the medial vestibulospinal tract).
Information from the vestibular system is also projected to other areas of the brain stem (the vomiting center in reticular formation) and brain (including synapses in the thalamus).

Study of the vestibular system

With unilateral damage to the vestibular apparatus, an imbalance occurs nervous activity, because vestibular apparatus on the healthy side it continues to constantly send impulses. This imbalance is interpreted by the brainstem as body movement, and nystagmus will occur with a rapid phase in the opposite direction of the lesion.

Determining the location (peripheral or central vestibular syndrome) is a very important part in the diagnosis of vestibular disorders. A thorough history, physical and neurological examination provide significant assistance in this regard. The main task in determining localization is to identify signs that are characteristic only of central vestibular syndrome.

Head tilt is observed in both peripheral and central vestibular syndrome. With PVS, the tilt of the head always occurs in the direction of the lesion; with PVS, the tilt of the head can be in the direction of the lesion or the opposite (see below - paradoxical vestibular syndrome).

Diseases leading to peripheral vestibular syndrome (PVS)

Metabolic causes
Hypothyroidism is common metabolic cause vestibular syndrome in older animals. Involvement of the peripheral vestibular system may be the first sign of hypothyroidism. Typically, hypothyroidism has an acute onset and a non-progressive course. Nearly all animals exhibit head tilt and positional strabismus, and many patients also show other signs of facial nerve damage, including decreased threat response and palpebral reflex. Such patients may also experience systemic signs of hypothyroidism, such as hypercholesterolemia.
Hypothyroidism can cause both peripheral and central vestibular syndrome; central may be associated with ischemic infarction.
Treatment consists of replacement therapy, most patients with early treatment return to normal condition.
Neoplasms can cause PVS by compressing or invading the vestibulocochlear nerve. Neoplasms peripheral nerves may initially appear as PVS, but over time the tumor may invade the brainstem.
Neoplasms of the ear (eg, adenocarcinoma of the ceruminal glands) can penetrate into the middle and inner ear and call PVS.

Most Frequent toxic causes leading to PVS are aminoglycosides, various means for cleaning ears. The onset of development of vestibular syndrome is usually acute. Treatment is to stop using the medications.

Trauma rarely results in PVS. In this case, vestibular syndrome will often be combined with signs of injury to other areas of the brain.

Diseases leading to central vestibular syndrome
In principle, any brain disease can also involve the central part of the vestibular system. There are no diseases that involve only the central part of the vestibular system.

Neoplasms can be primary or secondary. Maybe chronic course or acute onset. Neoplasms cause compression, ischemia or infiltration. The prognosis depends on the location, size, and type of tumor. Treatment is conservative (for example, corticosteroids to relieve peritumoral edema), chemotherapy, surgical removal, radiation therapy.
Inflammatory diseases can be infectious (canine distemper, feline infectious peritonitis, toxoplasmosis, bacterial meningoencephalitis, etc.) and non-infectious origin(considered autoimmune diseases). Treatment depends on the cause (for non-infectious meningoencephalitis, treatment involves the use of various immunosuppressive drugs). Forecasts are always very cautious.
Metronidazole intoxication– one of the possible causes of damage to the central vestibular system. The onset of the disease is acute, usually observed after long-term use high doses of metronidazole. Symptoms of intoxication – generalized ataxia, nystagmus, vomiting; in more severe cases– depression, convulsions, opisthotonus. Treatment is discontinuation of metronidazole, after which patients return to normal, usually within 1–2 weeks. Using diazepam usually speeds up recovery.
Thiamine deficiency can cause damage to the vestibular system. It can occur due to a lack of thiamine in the feed, the destruction of the vitamin during preparation, or the content of large quantity thiaminase (a substance that destroys thiamine; it is found in abundance in fish). Thiamine deficiency causes bilateral foci of necrosis and hemorrhages in the brain stem. In cats, the vestibular nuclei are primarily affected, and there may also be evidence of cerebellar involvement. Treatment is the administration of thiamine; with early detection and treatment, the prognosis is usually favorable.

Vascular disorders

Literature:

1. Michael D. Lorenz. Handbook of veterinary neurology.
2. Evans H. E., A. de Lahunta. Miller's anatomy of the dog.
3. Curtis W. Dewey. Practical guide to canine and feline neurology.
4. Platt S., Garosi L. Small animal neurological emergencies.