24/7 Emergency
While examining a dog or cat for a neurological problem, a neurologist’s primary aim is to pinpoint where exactly the problem is located in the nervous system. We do not start with a CT or MRI. Instead, we begin by asking our patients a series of questions. For example, “Do you know where your feet are? Can you see this?” We then compile the answers into what is known as a neuroanatomic localization to designate where the problem is.
After locating the problem, we consider all the possible causes. More often than not, we rely on advanced imaging testing for diagnosis. Why? The nervous system is a soft, three-dimensional and symmetrical structure encased in bone, which makes imaging a challenge. In fact, the complex structure prohibits conventional imaging as X-rays and ultrasounds cannot see past the bone to the nervous tissue.
The ability to slice the nervous system in different planes and sections is paramount to identifying abnormalities. Therefore, cross-sectional imaging is the mainstay of diagnosis. There are two options of cross-sectional imaging: CT or MRI.
CT or MRI?
CT (computerized tomography) or “CAT scans” is the older modality of the two and is based on the principle of X-rays. How does it work? The CT scan directs hundreds of X-rays at the patient to generate detailed images. Because it is based on density like an X-ray, CT is very good at imaging bone since it is full of calcium. Thus, it is the preferred modality for cases of external trauma. It also tends to be slightly quicker and occasionally less expensive than MRI.
However, CT is very poor for imaging the nervous system itself because of its poor soft tissue resolution. To be useful, external contrast must be injected around the nervous system (myelogram) which has inherent dangers including seizures. Another disadvantage of CT is that it produces large amounts of ionizing radiation.
For this reason, MRI (magnetic resonance imaging) has become the gold standard for nervous system imaging. MRI creates incredibly detailed images of sections of the brain and spinal cord. Why? The technology is unique in that it is based on water content rather than tissue density. A powerful magnet aligns water molecules and sounded pulses knock them off their axis. Based on the speed they return to their resting position, the MRI can determine differences between tissue water content.
Because of its superiority in visualizing the brain and spine, MRI has largely replaced CT in all types of neuroimaging. However, MRI does have limitations. These include a longer scan time, inability to image near metal and cost (occasionally, MRI is more expensive than CT).
CARE’s Neuroimaging Options
At CARE, we use both a multi-slice Toshiba CT and high-field 1.5 Tesla General Electric MRI. These instruments allow us to perform the highest quality neuroimaging, allowing us to accurately diagnose and determine the best treatment option for our patients. As neurosurgeons, we are better prepared for our procedures and expect improved outcomes, including less perioperative discomfort and more complete recoveries.
How CARE Can Help Your Pet
If your pet is showing clinical signs of a neurological problem, schedule an immediate examination with your primary veterinarian. Your vet’s evaluation will help determine whether your pet needs to see a specialist. It will also help decide if a CT or MRI is necessary for diagnosis. Ask for a referral to CARE’s Neurology/Neurosurgery team. 704-457-2300.
