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THE REFERRAL PROCESS
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Neurological Examination
Why having your animal examined is important?

The aims of the neurological examination are for your veterinarian to answer four fundamental questions:

  1. Does your animal has a neurological problem
  2. Which part(s) of your animal's nervous system is affected
  3. What types of diseases could be the underlying cause of your animal symptoms
  4. How serious is the problem.


Does your animal have a neurological problem?

Although some symptoms such as epileptic seizures, total paralysis, circling unequivocally suggest a neurological problem, others can be caused by non-neurological problem. Blindness, weakness, lameness are among the symptoms that can have neurological as well as non-neurological origin.

A complete physical and neurological examination can help your veterinarian to confirm the neurological nature of your animal symptoms.

Which part(s) of the animal's nervous system is affected?
Answering this question is probably the most crucial part of a successful neurological consultation. Contrary to the common belief, even the most sophisticated diagnostic tool such as MRI can only look at a small portion of the nervous system at a time. Knowing exactly where to look can not only save lots of time and expense, but it can also help your veterinarian interpret the tests your animal will go through.

Looking at the wrong place can lead to misdiagnosis by finding some abnormality or defect that may not have any relevance for your animal's problem (defined as incidental finding). Similarly, other conditions such as primary (idiopathic) epilepsy or degenerative myelopathy (commonly known as CDRM) may not show up on any diagnostic test by their nature and your veterinarian is only able to diagnose them by ensuring that the correct part of the nervous system has been looked at and any other causes have been ruled-out.

The nervous system is divided into the brain, the spinal cord and the peripheral nervous system [drawing]. The brain is divided in two main parts: (1) forebrain (or front of the brain) involved mainly in vision, smell, behaviour and to some degree control of movements, (2) mid- and hindbrain (or back of the brain) controlling balance, initiation and co-ordination of movements, breathing and heart function, as well as part of the peripheral nervous system (cranial nerves) involved in control of swallowing, movement of the jaw, tongue, eyelid and eyeball, ears and lips.

The spinal cord is made of cables joining the brain to the peripheral nervous system controlling the limbs and organs in the chest or abdomen. It is protected and runs inside a bony canal within the spine. The later is made by an assembling of vertebrae articulated by intervertebral discs (located just under the spinal cord) and a couple of joints located on each side and on top of the vertebrae [picture spine].

The spinal cord is practically divided in four parts:

  1. Cranial cervical (in the higher part of the neck)
  2. Cervico-thoracic (lower part of the neck at junction between neck and chest)
  3. Thoraco-lumbar (also called "back")
  4. Lumbo-sacral (or "lower back").

The peripheral nervous system consists of the nerves leaving the back of the brain to innervate muscles and glands of the head (cranial nerves) and peripheral nerves leaving the spinal cord to control in particular the muscles of the limbs. The junction between the peripheral nerve and its effector (muscle or gland) is called the neuromuscular junction.

Each part of the nervous system can be evaluated by testing the animal's reflexes and responses [picture patellar reflex, paw position response]. These reflexes and responses test specific pathways and functions of the nervous system. By combining their results, your veterinarian can determine if your animal problem is affecting the brain, the spinal cord or peripheral part of the nervous system.

Diseases affecting specific part of the nervous system are collectively called: encephalopathies (brain diseases), myelopathies (spinal cord diseases), neuropathies (peripheral nerve diseases), junctionopathies (diseases of the junction between peripheral nerve and muscle) and myopathies (muscle diseases). Neuropathies, junctionopathies and myopathies are also called neuromuscular diseases. These terms only refer to which part of the nervous system is affected, as determined by the neurological examination, but they do not preclude the underlying cause.

What types of diseases could be the cause of your animal symptoms?
The neurological symptoms displayed by an animal are specific of a defective part of the nervous system and rarely of a specific disease.

Neurological diseases are initially considered in broad terms as:

  • vascular disease (defective blood supply or vessel rupture causing a bleed)
  • inflammatory or infectious disease, traumatic disease (spinal or head trauma, acute 'slipped disc')
  • malformation (cyst, hydrocephalus)
  • metabolic disease (organ dysfunction causing accumulation of product toxic for the brain or insufficient nutrient such as sugar)
  • idiopathic disease (disease caused by a functional problem such as a chemical unbalance or disease for which there is no known underlying cause)
  • neoplastic disease (cancer of the nervous system or spread from a cancer somewhere else in the body)
  • degenerative disease (disease causing degeneration or premature ageing of the nervous system)

Knowing the course of your animal's problem (did the problem started suddenly or more insidiously? - had the symptoms remained the same, got worse or improved?), it is possible to narrow down these disease categories to three or four possibilities collectively named 'differential diagnosis'.

Further diagnostic test [see specific sheet - diagnostic tests] are then necessary to narrow down even further this differential diagnosis and if possible precisely identify the exact type of disease causing your animal's symptoms.

How serious is the problem?
It is unfortunately often very difficult on the sole basis of the neurological examination to predict what could be the chance of successfully treating your animal as this depends on what disease is causing the problem and how advanced it is. Not only are the symptoms displayed by your animal not specific of a particular disease, they are also not precluding the severity of whatever disease is underlying them.

For example, some conditions such as vascular diseases (stroke and ischemic myelopathy - see specific sheets) often have a very good outcome despite causing sudden and often dramatic symptoms. On the other hand, conditions such as degenerative diseases (degenerative myelopathy - see specific sheet) cause progressive and irreversible symptoms despite causing very subtle signs initially.

If you are concerned about the health of your pet you should contact your veterinary surgeon.


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