The Nervous System is subdivided into two components: the Central Nervous System and the Peripheral Nervous System. The former comprises the brain and spinal cord, while the latter refers to all the parts of the nervous system outside the brain and spinal cord. Together, they allow both humans and animals to experience life and regulate bodily functions. However, like any other bodily system, the nervous system can be affected by congenital diseases, inflammation, infection, nutritional and metabolic problems, trauma, degenerative diseases, neoplastic diseases, among others. With this short article, we intend to inform owners of the most common neurological diseases in dogs and how to recognise them. Whenever one of these diseases is suspected, you should take your pet to your veterinary surgeon or, in some cases that we will identify, to an emergency room.

The most common neurological diseases in dogs:

• Intervertebral disc disease
• Epilepsy
• Otitis media and internal otitis o Injuries resulting from trauma and fractures
• Poisoning

Diseases of the intervertebral discs

Intervertebral discs are structures located between two vertebrae (the bones of the spine) and their main purpose is to reduce friction between the vertebrae and allow the spine to have some degree of mobility. With ageing, these discs can undergo a series of changes, among which the most common is called spondylosis, commonly known as “parrot beak”.

This condition is often a radiographic finding in dogs without symptoms, however, when symptomatic, it is quite painful and limiting, causing significant instability in the spine. On the other hand, the centre of the intervertebral discs is made up of a kind of jelly called the nucleus pulposus which, with ageing, can undergo changes, and calcify, making it easier for the nucleus pulposus to leak into the spinal canal, where the spinal cord is located, and compress this structure – forming a disc herniation.

The formation of the hernia is a sudden event, in which suddenly, the dog becomes full of pain and with paresis or paralysis of the limbs. If this happens, your dog should be seen quickly by a veterinarian so that action can be taken as quickly as possible, in an attempt to avoid permanent paralysis.

Epilepsy

Epilepsy is the most common neurological disease seen in dogs and is estimated to affect around 0.75 per cent of the canine population. The term epilepsy refers to the presence of recurrent, unprovoked seizures that result from alterations in the brain.

This disease can be hereditary (of genetic or idiopathic origin), caused by structural problems in the brain (structural epilepsy) or, the most common form, have an undetermined cause (epilepsy of unknown cause – idiopathic). Although it’s not an emergency in itself, as these episodes are usually limited in time, a seizure that doesn’t stop is a real emergency. In other words, if your dog has a seizure and stops, or stops taking medication (if it’s not the first time it has happened and you already have a prescription for emergency medication) it’s not an emergency, but should be seen in the next few hours, a dog that goes into status epilepticus, that is, a seizure that doesn’t stop, should be seen immediately.

Most dogs will not be medicated chronically after the first seizure, but we should always try to diagnose the source of the seizures so that we can treat the dog in the best way. Unfortunately, most dogs develop idiopathic epilepsy and no diagnosis can be made.

Middle and inner ear infection

Otitis is an inflammation of the ear. It can be external if it’s limited to the external ear canal, middle if it reaches the middle ear and internal if it reaches the inner ear. As a general rule, otitis is progressive, but internal otitis can develop haematogenously, in other words through the bloodstream.

Neurological signs appear in cases of middle or inner ear otitis. In the case of middle otitis, the most common signs include the signs of external otitis (shaking the head, scratching the ears, exudate in the ear canal), Horner’s syndrome (protrusion of the third eyelid unilaterally, constriction of the pupil, retraction of the eye into the eyelid and drooping upper eyelid), facial paralysis, decreased hearing and dry keratoconjunctivitis (decreased tear production leading to inflammation of the eye).

When it comes to internal otitis, the most common signs are head tilt, circling, loss of balance, motor incoordination and horizontal nystagmus (involuntary eye movements). In very serious cases, the infection and inflammation can spread from the inner ear to the meninges and brain, causing meningitis or meningoencephalitis.

Injuries resulting from trauma and fractures

Traumas and fractures can cause a wide range of neurological signs, from paresis, paralysis, pain due to compression of nerve structures, convulsions and, in the most extreme cases, coma and death.

Poisoning

Certain insecticides such as organophosphates and carbamates are common sources of poisoning dogs – both cause unspecific signs with stimulation of certain receptors (naming them is beyond the scope of this article) such as salivation, involuntary muscle contractions, muscle weakness, involuntary urination, diarrhoea, vomiting and bronchospasm. Another toxicant, now less used, is strychnine. Strychnine causes muscle rigidity in which dogs are always in extension, accelerated heart and respiratory rate, increased temperature, apnoea and extensive salivation. Fortunately, poisoning is becoming less and less common, but when it does happen, dogs should be assisted as soon as possible to give them a better chance of survival.

In short, neurological diseases in dogs are very varied and their presentations aren’t always clear-cut. If you suspect that your dog may be suffering from one of these diseases, you should contact your veterinary doctor who will be able to give you the best advice.

Vet.Point – Oeiras Veterinary Clinic
Emergency 24h | 927896112 – 211918923 | geral@vetpoint-ivl.com