Laboratory Tests and Imaging In Dogs
Metabolic disorders that can adversely affect the functioning of the nervous system can be detected by laboratory tests which include both routine as well as specific blood tests. Infections and poisoning can also be detected by these tests. Neuromuscular disorders of autoimmune origin such as myasthenia gravis can be diagnosed through blood tests that detect the presence of antibodies against neurotransmitters involved in the transfer of electrical signals between nerves and muscles.
Cerebrospinal fluid Analysis
Testing the cerebrospinal fluid found around the brain as well as the spinal cord can help diagnose disorders affecting the central nervous system in dogs. This fluid is extracted by a surgical procedure known as spinal tap. This procedure can be conducted at the base of the skull or at the lower back area. The cerebrospinal fluid is examined for abnormal levels of proteins, WBCs and infective agents. Presence of proteins in excessive amounts is an indication of inflammation of the brain, a condition known as encephalitis. It can indicate meningitis too, which is an inflammation of the tissue layers called meninges that surround the brain. Abnormally high white blood cell count may be caused by an infection or inflammatory condition. While abnormal cells in the fluid indicate cancerous growths, pus cells and red blood cells indicate brain abscesses and bleeding. Presence of Rocky Mountain spotted fever, canine distemper virus, other bacterial and fungal infections can also be detected by cerebrospinal fluid testing.
Radio imaging tests are helpful in the assessing the site and the cause of nervous system disorders. X–rays of the head and the trunk are taken to determine whether the dog has had any fractures in the skull or the vertebral column that may have resulted in injury to the brain and the spinal cord. They can detect cancers of the bone and the presence of certain types of infections and inflammatory conditions. But plain x-rays may not detect tumors of brain or the spinal cord. Hence, another test called myelography is used to detect such abnormalities. The x-rays are taken after injecting a dye into the cerebrospinal fluid. The dye can be detected by x-rays and offers a contrast that shows tumors of the spinal cord as well as herniated vertebral disks that put pressure on the spinal cord.
CT scan or Computed tomography is another radio imaging test useful in detecting abscesses, internal bleeding, inflammations, and cancerous growths besides bone abnormalities.
MRI scan or Magnetic resonance imaging is another test used to detect nervous system abnormalities.
A few other tests used to determine nervous system disorders are:
The electrical activity that takes place in the brain is recorded in this test. Abnormal readings are obtained when there is any injury to the brain or if infections and inflammatory conditions such as encephalitis or meningitis are present. Brain tumors also give abnormal results. If the dog has seizures, an electroencephalogram may help assess their severity and detect what causes them.
This test is conducted by stimulating a nerve with electricity. By measuring the speed at which the electric signal is conducted along the nerve fibers to the muscles, nerve injuries can be detected. This test is used to diagnose myasthenia gravis.
Brain stem auditory evoked response (BAER)
This test is conducted to determine deafness due to damage to the cerebrum and the brain stem. It records the electrical activity between the sound-sensing mechanism located in the ear and the auditory centers in the brain. The BAER will not have any response if the dog has deafness due to any damage to the nerves. Other disorders of the brain stem may alter the response obtained through this test.