Deafness in dogs and cats. Deafness in dogs, congenital and acquired character The dog does not hear well what to do the reason

Deafness can be caused by problems with the transmission of sound to the inner ear, or by disturbances in the delicate parts of the inner ear that convert sound signals to electrical signals.

In addition, there may be dysfunction of the auditory nerve, which transmits a signal to the brain or to the region of the brain responsible for hearing.

Common symptoms of deafness in a dog

Dog breeders often do not notice the deafness of the dog, believing that she simply does not want to follow the commands. The signs of the disease are as follows:

• If only one ear is affected, then the dog continues to hear, but cannot determine the direction to the sound source.
• The dog does not respond to a sound that has recently piqued its interest.
• Your dog has a hard time finding you when you call him for a walk.

Causes of deafness in a dog

Possible causes of deafness are as follows:

• Blockage of the ear canal by a foreign body or discharge from otitis media.
• Damage to the tympanic membrane.
• Damage to the auditory hammer or rupture of the fluid sac in the middle ear.
• Changes in the middle ear as a result of aging.
• Anatomical disorders associated with abnormal development of the body.

Dogs at risk

Deafness is a well-known problem in young Dalmatians as well as in breeds:

• boston, bull terriers and fox terriers,
• redhead and border collie,
• cocker spaniels,
• Doberman Pinschers,
• German shepherds,
• Old English Shepherd Dogs.

How to proceed

If you suspect that your dog has a hearing problem, then a simple test should be performed to check how your dog responds to sounds of varying volume and pitch. If the test shows that the dog does not hear everything, then immediately show it to the veterinarian.

The doctor examines the condition of the dog's ears for obvious causes of the condition before proceeding with the hearing test. If the appropriate equipment is available, verification can be carried out using electronic testing.

Treating deafness in a dog

If the ear canal is blocked by a foreign body or secretions from otitis media, the veterinarian will clean it.

Anatomical changes cannot be treated. If your puppy has intermittent deafness, you can help by teaching him to follow hand commands. It is very helpful to seek advice from breeders whose dogs are also deaf.

In this article I will talk about deafness in dogs. I will describe the symptoms of the disease, the types and causes of deafness. I will explain how to treat an ailment and properly maintain a deaf dog.

Deafness is a hearing impairment that results in a decreased ability to detect and understand sounds.

Causes of Deafness in Dogs

The main reasons for the development of the disease are:

Deafness happens:

• congenital and acquired;
• one-sided and two-sided;
• full and partial;
• temporary and permanent;
• sudden and chronic.

Congenital deafness, as a hereditary (genetic) pathology, is associated with a set of certain genes in a dog that are responsible for white pigmentation.

The merle gene (white coat and blue iris of the eyes) is transmitted in dogs of the breed: collie, Old English Shepherd, American Foxhound, etc. The piebald gene (spotted color) is found in breeds: Bull Terrier, Dalmatian, English Setter, Bulldog, etc.

The presence of these genes in the animal's DNA affects the process of blood circulation and blood supply to the cochlea of ​​the inner ear.

Which leads to the death of cells of the auditory ossicles.

The acquired ailment is associated with trauma to the hearing system (mechanical damage, tumors, the consequences of infectious and autoimmune diseases), impaired blood supply and innervation.

Symptoms of the disease

Signs that your dog's hearing has deteriorated include:

• non-responsiveness to one's own name;
• failure to comply with well-trained commands;
• the inability to wake up the dog with a voice, only by touch;
• fear of a pet when sneaking up on it from behind;
• increase in daily sleep duration;
• possibly disorientation in space;
• decreased activity;
• loss of desire to play outdoor games.

With congenital hearing loss, a deaf puppy among the litter is different:

• complete immunity to sounds;
• inappropriate and aggressive behavior towards their fellow tribesmen.

Congenital deafness is not felt by dogs as they never knew what sound was

Treatment of the disease in dogs

Treatment of the disease is prescribed after a diagnostic examination, consisting of:

• inspection;
• sound testing;
• X-ray, CT and MRI;
• neurological examination.

Therapy is determined based on the established causes of the disease:

With neurological diseases and significant injuries, as a rule, it is impossible to cure the ailment. It is only possible to suspend the development of the disease.

Congenital deafness, like senile deafness, cannot be cured.

How to properly maintain a deaf dog

In the case of congenital deafness, the dog is from birth in soundproofing and does not experience any inconvenience. As compensation for hearing, he develops other analyzers of the surrounding world, which allows him to fully exist in the world around him.

With acquired deafness, adaptation to new living conditions is slow and requires help from the dog's owners.

To improve the quality of life of your deaf four-legged friend, you need to:

1. Protect the animal from injury. Remember and realize that the dog now really does not hear sounds. When something falls or approaches nearby, the animal may not notice it and not assess the potential threat.
2. You can only walk a deaf dog on a leash and not leave it unattended on the street. Since the pet does not hear sounds, the approach of a car or other dangerous animal may not be noticed.
3. If walking without a leash, use the bell on the dog's collar during walks, so that you can find it by sound. The animal does not hear the owner's voice and will not come running to the call.
4. Teach your pet to understand the movements, gestures and facial expressions of the owner. Train him to do this every day. Dogs in the absence of hearing, lend themselves well to training through human gestures, tactile sensations and the expression on the face of their owner.
5. Learn to respond to tactile stimuli, such as waking up, eating, or walking after stroking or patting his body.
6. Do not sneak up on the dog from behind and do not wake up with sharp touches. Before you approach the pet, if you are out of its field of vision, you must stomp on the floor. So that the pet feels vibration and does not get scared.

It will take some time to get back to normal life with a hearing impaired animal.

With a careful and caring attitude towards a deaf dog, it is possible to adapt it to the changed conditions of existence so much that the inability to hear will not affect the quality of life of a four-legged friend.

In this article, I talked about deafness in dogs. She described the symptoms of the disease, the types and causes of deafness. Explained how to treat ailment and properly maintain a deaf pet.

Evaluation of dogs and cats with hearing loss has interested few researchers. However, over the past decade, there has been an increase in basic and clinical studies of deafness in animals. In part, this interest has resulted in an increased focus on congenital deafness, which has always been a concern for breeders and owners of deaf animals. In the last study, 1,031 Dalmatian dogs were examined, of which 29.7% were diagnosed with congenital deafness by the auditory brain stem evoked potential (Strainetal., 1992). The incidence of congenital deafness in dogs of other breeds was also high. Hearing loss in old age has turned out to be another interesting area of ​​research. Many owners of older animals often ask when hearing loss will reach such a limit that the animal will be cut off from the outside world. That is why knowledge of the different types of hearing loss, their causes, treatment and prevention methods is so important for a veterinarian.

Anatomy and physiology of the hearing aid

The hearing aid is subdivided into the outer, middle, and inner ear and central pathways. Sound is collected through the outer ear and mechanically transmitted through the eardrum and ossicular chains to the fluid system of the cochlea. The cochlea contains the auditory receptors, or organ of Corti. It is made up of rows of intrinsic sensory cells that reside on the main membrane. The continuation of each cell is the stereocilia, which lies in the integumentary membrane - a gelatinous structure that covers the organ of Corti. Acoustic vibrations vibrate the main membrane; upward displacement of the main membrane bends the sterocilia onto the organ of Corti. This displacement leads to mechanical deformation of sensitive cells, which changes their electrical conductivity and provides an adequate stimulus for their activation. The activation of sensory cells generates neural activity in the cochlear nerve. The cells of the cochlear nerve lie in the spiral ganglion. Central fibers from the central ganglion enter the cranial cavity through the internal auditory canal (accompanying the facial and vestibular nerves). Upon entering the brainstem, the cochlear nerve ends in the cochlear nucleus, which runs to the auditory cortical center in the temporal lobe.

Deafness classification

Hearing impairment can occur anywhere in the auditory tract and is classified by the anatomical site of the impairment. Deafness (hearing loss) can be divided into two types: conductive and sensorineural. Conductive deafness is a consequence of pathological changes in the outer and middle ear, which leads to a defect in the mechanical transmission of sound to the cochlea. Diseases that cause occlusion of the ear canal, hardening or rupture of the tympanic membrane, damage to the ossicular chain, or effusion in the middle ear can lead to conductive hearing loss. Sensorineural deafness (also called nerve deafness) is the result of dysfunction of the cochlea or cochlear nerve caused by degeneration of the organ or cochlear nerve of Corti. It is rare to recognize hearing impairments resulting from impairments to the cochlear nucleus or the ascending auditory tract, since rupture of the central tract requires extensive damage, which will necessarily result in severe neurological impairment.

Common Causes of Hearing Loss

Conductive hearing loss
Outer ear
Obstruction of the external auditory canal can be caused by compressed earwax, otitis externa with stenosis of the external auditory canal, and neoplasia. Atopic dogs often have persistent otitis externa and perforation of the eardrum, which in chronic cases can lead to infection spreading into the middle ear cavity. Foreign bodies in the ear canal or trauma following a blow to the head or penetrating injury can cause exudation in the ear canal and subsequent conductive hearing loss.

Middle ear
Otitis media with exudation is a common cause of hearing loss. Infection and inflammation can reach the middle ear cavity in three different ways: by direct spread through the damaged tympanic membrane, through the Eustachian tube, or by hematogenous dissemination. Exudation in the middle ear cavity can be caused by bacterial, viral and fungal microorganisms. Obstruction of the Eustachian tube after chronic inflammation or as a result of a tumor can lead to exudation in the middle ear cavity. An inflammatory polyp in cats often originates in the middle ear or Eustachian tube and produces a serous or suppurative inflammatory response. Irradiation of the head and neck can cause osteoradionecrosis of the tympanic bladder or disrupt the lymphatic drainage of the nasopharynx, which will also lead to exudative processes in the middle ear cavity.

Sensorineural hearing loss
Inner ear
Most of the conditions that cause sensorineural hearing loss result in the degeneration of sensory cells in the organ of Corti or the cochlear nerve itself. While there are many reasons for this, genetic and congenital disorders, as well as aging changes, are the main causes of this type of hearing loss.

Congenital / hereditary deafness is a complete loss of hearing in the affected ear, it can be uni- and bilateral. The overall incidence of congenital / acquired deafness is not known, but it is clear that it is a common, if not the main, cause of hearing loss in young animals. Congenital / inherited deafness is present in at least 48 dog breeds (Table 1).

Table 1. Breeds of dogs with congenital and hereditary deafness
Akita American staffordshire terrier Australian shepherd Australian shepherd Beagle Border Collie Boston terrier Boxer Bulldog Bull terrier Leopard dog Catahoulas American cocker spaniel Collie Dalmatian Dachshund Doberman Dogo argentino English setter Foxhound Fox terrier German Shepherd German dog Large pyrenean dog Ibizan greyhound	Jack Russell Terrier Kuvasz Maltese Miniature pinscher Miniature poodle Mestizo Norwegian Hound Old english shepherd Papillon Pit bull terrier Pointer Rhodesian ridgeback Rottweiler St. Bernard Schnauzer Scottish terrier Sealyham Terrier Sheltie Shropshire terrier Siberian Husky English springer spaniel Toy poodle American foxhound West Highland White Terrier

Highest incidence among Dalmatians, Bull Terriers and English Setters. Congenital / acquired deafness is usually associated with a pigmentation disorder. Affected breeds always have genes for black or white pigmentation, and the incidence rises sharply with a predominance of white pigmentation. Hereditary deafness is transmitted as an autosomal dominant trait in some white cats with blue eyes. Almost all dogs and cats with congenital / hereditary deafness will have cochleosaccular degeneration histopathologically. It is characterized by loss of blood supply to the cochlea (striavascularis) after degeneration of sensitive cells of the organ of Corti. In Dalmatians and white cats with blue eyes, pathology is observed already at the age of three weeks, the subsequent loss of spiral ganglion cells occurs by the first year of life, and in old animals, degeneration of neurons of the central auditory tract was noted. Dalmatians showed no or decreased melanocytes striavascularis, which may be related to the initial streaky degeneration.

Congenital peripheral vestibular syndrome associated with deafness as a consequence of the degeneration of the organ of Corti was noted in young Dobermans. This syndrome has been described in English Cocker Spaniel, Beagle, German Shepherd, Akita, and Sim and Burmese cats. Although deafness is sometimes associated with this syndrome, in most cases hearing tests are not performed, so the true incidence of deafness is not well understood.

Acquired sensorineural hearing loss as a result of dysfunction of membranous structures inside the cochlea is observed in hypothyroidism, infectious labyrinthitis, injuries and neoplasia of the temporal bone. Ototoxicity of systemic and local aminoglycosides can lead to severe degeneration of the cochlea and sensitive cells. Other ototoxic drugs for dogs and cats are loop diuretics and antiseptic ear drops. Age-related hearing loss and deafness in dogs is degenerative and is associated with atrophy and loss of spiral ganglion cells in the cochlea. This loss is possibly due to degenerative changes in sensory cells in the organ of Corti.

Clinical symptoms of deafness

Clinical diagnosis of incomplete bilateral or complete unilateral deafness is always difficult. With complete bilateral deafness, the animal is easily frightened, and if it does not see the cause of anxiety, it sleeps peacefully with a lot of noise and does not wake up. Completely deaf animals do not respond to sound signals of varying intensity, they are difficult to train, because they have to give signals with their hand, they are shy and aggressive. The only clinical symptom of unilateral deafness is poor sound localization.

Diagnostic approach

Given the many causes of hearing loss, a careful history must be taken to diagnose. The age at which the disease began, the course of the disease, history of previous hearing problems and the appointment of ototoxic drugs should be recorded. When symptoms appear before the age of 5 weeks, the likelihood of a breed predisposition to congenital and hereditary deafness is high. Since conductive deafness responds well to treatment, the first step is to rule out all diseases of the outer and middle ear. A general examination should include not only a complete otoscopy, but also a thorough examination of the head, neck, and cranial nerves. Head shaking, pain and discharge from the ear canal, or cranial nerve damage (Horner's syndrome, keratoconjunctivitis, head tilt, nystagmus) help in choosing a direction for further research. With purulent otitis media / otitis media, cytological tests, bacterial culture and a sensitivity test of the outer and middle ear are shown. In the case of infectious labyrinthitis and neoplasia, an x-ray of the tympanic bladder and temporal bone is shown.

Hearing test

The most widely used electrodiagnostic test of the integrity of the auditory analyzer is the auditory brainstem evoked potential (ACBP). It is especially useful when evaluating naughty or young animals in which behavior interferes with correct diagnosis. This test does not require the conscious participation of the animal and therefore provides an objective assessment of hearing. During the test, the neural response to sound stimuli is recorded by electro-encephalographic signal averaging. The electrical activity that occurs after a series of clicks, first near one ear, then near the other, is recorded by electrodes installed in the head area.

Since each ear is tested separately, unilateral deafness can be detected immediately. The SPSGM recording consists of a series of four or seven waves with an interval of approximately 1 ms after the sound stimulus. These waves reflect electrical activity in the cochlear nerve and central pathways. Since any activity of Corti's organ or cochlear nerve will be expressed in waves, their absence indicates the complete deafness of this ear. By varying the intensity of sound stimuli, a behavioral threshold is determined. Recording responses to sounds of varying intensity can give an elevated threshold, suggesting conductive or sensorineural hearing loss. Audiometric impedance (tympanometry, acoustic reflex) is used to study the interaction of the middle ear, cochlea, seventh and eighth cranial nerves and the pathways of the brain stem. These tests are used in combination with UHCS and clinical interventions. Audiometric impedance is still under development, so it is not used in all clinics.

Treatment and prognosis

Most animals with conductive hearing loss due to otitis media improve or recover hearing after prolonged antibiotic treatment. Sensorineural deafness due to congenital / hereditary causes or old age is irreversible. Some improvement can be achieved after treatment of infectious labyrinthitis or withdrawal of ototoxic drugs. When conductive deafness does not respond to medication or surgery, hearing aids can be used to amplify the sound. Hearing aids also help in some cases of age-related sensorineural deafness. However, animals do not perceive working models of hearing aids well.

For breeds with a high predisposition to congenital deafness, it is recommended to carry out SPSGM in stud dogs, bitches and litters. Owners of animals with congenital deafness are prohibited from participating in breeding programs. Although there are variations, animals with bilateral congenital deafness may not make good companions because they are shy, aggressive, and prone to injury. Animals with unilateral congenital deafness can be excellent companions.