Neurological Examination Fact Sheet
What to expect during your pet's neurological examination.
Why is having your animal examined important?
The aims of the neurological examination are to enable your clinician to answer four fundamental questions:
- Is your pet suffering from a neurological problem?
- Which part(s) of your pet’s nervous system is affected?
- What types of diseases could be the underlying cause of your pet’s symptoms?
- How serious is the problem?
1. Is your pet suffering from a neurological problem?
Although some symptoms – such as epileptic seizures, total paralysis, circling – unequivocally suggest a neurological problem, others may be caused by a non-neurological problem. Blindness, weakness and lameness are among the symptoms that can have neurological as well as non-neurological origins.
A complete physical and neurological examination can help your vet to confirm the neurological nature of your pet’s symptoms.
2. Which part(s) of your pet’s nervous system is affected?
Answering this question is probably the most crucial part of a successful neurological consultation. Contrary to common belief, even the most sophisticated diagnostic tools, 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 can also help your vet 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 be relevant to your pet’s condition (defined as an ‘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 vet will only be able to diagnose them by ensuring that the correct part of the nervous system has been examined and any other causes have been ruled out.
An overview of the nervous system
The nervous system is divided into the brain, the spinal cord and the peripheral nervous system. The brain is divided in two main parts:
- Forebrain (or front of the brain) – involved mainly in vision, smell, behaviour and to some degree control of movements
- 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 and controls the limbs and organs in the chest and abdomen. It is protected and runs inside a bony canal within the spine. The latter is made by a column 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.
The spinal cord is practically divided in four parts:
- Cranial cervical (in the higher part of the neck)
- Cervico-thoracic (lower part of the neck at junction between neck and chest)
- Thoraco-lumbar (also called “back”)
- Lumbo-sacral (or “lower back”).
The peripheral nervous system consists of the nerves leaving the back of the brain to innervate the muscles and glands of the head (cranial nerves), and the 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. These reflexes and responses test specific pathways and functions of the nervous system. By combining their results, your vet can determine if your pet’s 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)
- Myopathies (muscle diseases).
Neuropathies, junctionopathies and myopathies are also called neuromuscular diseases. These terms only refer to the part of the nervous system affected, as determined by the neurological examination, but they do not preclude the underlying cause.
3. What types of diseases could be the underlying cause of your pet’s 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 nutrients, such as sugar)
- Idiopathic disease (disease caused by a functional problem, such as a chemical imbalance or disease for which there is no known underlying cause)
- Neoplastic disease (cancer of the nervous system or cancer which has spread from a tumour somewhere else in the body)
- Degenerative disease (disease causing degeneration or premature ageing of the nervous system)
Understanding the development of your pet’s problem, for example:
- Did the problem start suddenly or develop gradually?
- Have 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 tests (see Neuro-Diagnostic Tests Fact Sheet) are then necessary to narrow this differential diagnosis down even further, and, if possible, precisely identify the exact type of disease causing your pet’s symptoms.
4. How serious is the problem?
On the sole basis of the neurological examination it is, unfortunately, often very difficult to predict what the chance will be of successfully treating your pet as this depends on the type of disease 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 related Fact Sheets listed below) often have a very good outcome despite causing sudden and often dramatic symptoms. On the other hand, conditions such as degenerative diseases (degenerative myelopathy) cause progressive and irreversible symptoms despite causing very subtle signs initially.
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