Myelogram, CT scan, and MRI of the Spine
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Article Written by Dr. Daniel A. Degner, Board-certified Veterinary Surgeon (DACVS)

Key Points

Myelogram involves injecting dye into the sac around the spinal cord and making x-rays of the spine; if a mass or slipped disc is present, the surgeon will see a disruption in the dye column

CT scan is a special type of x-ray that provides a cross-sectional image of the spine; this test is good for diagnosing a slipped disc that is calcified

MRI is a noninvasive tool that is very useful to diagnose many problems of the spine


Myelogram

  • The word myelogram is derived from 2 root words: myelo (spinal cord) and gram (picture).
  • The spinal cord cannot be seen with plain x-rays of the spine.
  • A myelogram involves injecting contrast media (dye) into the bag (called the dural sac..subarachnoid space) that surrounds the spinal cord.
  • After the injection, the outline of the spinal cord becomes very distinct, thus allowing the neurologist and surgeon to see if there are any masses compressing the cord or if the cord is swollen.
  • This test is an anatomical test, therefore it does not give us an indication of the function of the spinal cord.
  • Below is a myelogram of a dog's thoracolumbar spine.  Take note of the two white lines in the middle of the spine which is dye in the subarachnoid space.  The dye which outlines the spinal cord abruptly stops due to a mass of herniated disc material.  At the site of the herniated disc material the bottom dye line deviates upward because the mass of disc material is beneath the spinal cord. 

    

  • Prior to the myelogram, your pet will undergo a complete neurologic examination, blood work, and in some cases radiographs of the chest (to look for cancer of the lungs).
  • Because a myelogram involves an injection of contrast media near the spinal cord, it is performed with your pet under general anesthesia. This will allow proper positioning of the pet for the x-rays, so that the best study can be obtained. In addition, your pet will not experience any discomfort from the injection

 

Myelogram Procedure

  • An intravenous catheter will be placed and your pet then anesthetized. Very safe gas anesthetics are used during the procedure. Intravenous fluids are administered to all myelogram patients during anesthesia and recovery. Once your pet is anesthetized, a series of spinal x-rays will be taken. They will be examined for any grossly evident problems.
  • The next step is the injection of contrast media. An area over the lower back or sometimes the upper neck will be shaved and cleansed with antiseptics. A spinal needle is inserted between two vertebrae (spinal bones) until spinal fluid starts to drip out. Whenever possible, a sample of spinal fluid is collected for later analysis if indicated. The contrast media is then slowly injected around the spinal cord. The contrast agent will flow throughout the spinal fluid until it outlines most or all of the spinal cord. A series of spinal x-rays is then taken. The contrast media will outline the spinal cord and indicate any area of spinal cord swelling, compression or other abnormalities. Most of the patients that have a myelogram will also have a CT scan of the area of interest to better define the problem. Since we have a CT machine in our hospital this scan is done immediately following the myelogram.
  • Below is a CT scan of the same patient as above at the level of the herniated disc. This is a cross section through the spine; the oval hole in the spine is the spinal canal and the large amount of white material in the canal is herniated disc material; the smaller black crescent in the spinal canal is the spinal cord that is compressed to the top and left.

      

 

Indications for Myelography

  • Myelograms are most often used to diagnose a ruptured or herniated disc. While a patient may be presented with fairly obvious signs of a disc rupture, the myelogram is still needed to differentiate a ruptured disc from other conditions.
  • They are also used to diagnose the degree of spinal cord damage with a spinal fracture, tumors of the spinal cord and nerve roots, and tumors of the spine itself. In some situations a tumor around the spinal cord will have a similar appearance to that of a ruptured disc.
  • The myelogram also demonstrates the precise location of the problem. This is very important so that the surgeon knows the exact location to operate the spine.

 

Potential complications

  • As with any general anesthesia, complications may arise. Even though rare, anesthetic death can occur. With the use of modern anesthetic protocols and monitoring devices, the risk of problems with anesthesia is minimal.
  • Temporary loss of breathing due to irritation of the brain stem can be caused by the contrast media. This is rare and usually transient as the contrast media is excreted from the body fairly rapidly.
  • Allergic reaction (rare occurrence) to the contrast media can cause death.
  • Worsening of the function of the spinal cord may occur due to inflammation or damage to the spinal cord from the injection. If this occurs, it is usually transient.
  • Seizures can occur if the pet is sensitive to the contrast media. If this occurs during recovery from anesthesia, medication is used to control this. Seizure activity is almost always very transient and not fatal.
  • Sometimes a nondiagnostic (non-useful) myelogram will result if the contrast media is injected outside of the sac that surrounds the spinal cord. The study may need to be repeated the next day, once the dye is excreted from the body.

 

 MRI of the spine

  • In some cases in which the patient does not require immediate surgery we may recommend an MRI of the spine
  • We will refer to to the Thames Valley Imaging Center located in London, Ontario Canada for the MRI; this is the only facility in our area that offers MRI for pets.
  • The scans are available on Saturdays and the procedure is scheduled through Ms. Jane Sykes
  • Your pet will require blood work and will be anesthetized for the procedure, but will be able to go home soon after the scans have been made.  Please bring the scans to us for evaluation on Monday
  • Below left is an MRI of a spine with no herniated disc - note the black oval region is the spinal cord and the white halo surrounding the spinal cord is fat; below right is an MRI of a spine with a large amount of herniated disc material - note the flattened black oval region is the spinal cord and the black circular region immediately below the spinal cord is the herniated disc material which is compressing the spinal cord.

          

Frequently Asked Questions After Surgery

When should my dog have the first bowel movement after surgery?

  • Many dogs will not have a bowel movement for the first 4 to 5 days after surgery
  • Reasons that a dog will not have regular bowel movements after surgery include:
    • The dog has been fasted prior to surgery
    • Dogs do not eat well during the hospital stay
    • They frequently do not eat well when they go home
    • They are fed highly digestible food that produces little stool
    • Pain medication that contain narcotics (such as morphine, fentanyl patches, and tramadol) can be constipating
  • If a pet does not have a bowel movement on the 5th day of being home, a stool softener such as metamucil can be fed
    • Dose of metamucil is 1 tsp per 25 Kg mixed in with each meal (canned dog food); feed immediately after mixing, as the metamucil will gel the food and may make it less palatable

My pet had surgery and will not eat.  What can be done?

  • Dogs
    • Most pets will not eat their regular dog food after surgery, especially if it is kibble.
    • Offer a cooked diet having a 1:1 ratio of a protein source and carbohydrate source.  The protein source can be any meat (example: chicken breast, turkey breast, lean hamburger) that is low in fat and should be cooked (drain off all fat after the meat has been cooked).   The carbohydrate can be pasta, potato or white rice.
    • Try canned dog food; to enhance the flavor sprinkle a very small amount of garlic powder or chicken or beef broth (Chicken-in-a- MugTM or Beef-in-a-MugTM products)
    • Try Gerber strained meats for babies such as the chicken, beef, turkey, or veal
    • Try Hill's A/D diet available at most veterinary hospitals
    • Hand feeding: place a small amount of food in the mouth so that your dog gets the flavor
    • Warm the food slightly in a microwave, as the food will be more aromatic; stir the food before feeding and test the temperature on the bottom side of your wrist; it should only be luke warm.
    • Remember that most pets will not eat the first day or two after they get home from surgery
  • Cats
    • Offer smelly foods that contain fish such as tuna or smelly cat foods
    • Try Gerber strained meats for babies such as the chicken, beef, turkey or veal
    • Hand feeding:  with your finger place a small amount of food on the roof of your cat's mouth; use a syringe to get soft food into the mouth
    • Warm the food slightly in a microwave as the food will be more aromatic; remember to stir the food before feeding and test the temperature; it should be only luke-warm
    • Some cats will only eat dry food, try kibble if your cat normally has been fed that food
    • Petting and stroking your cat frequently will help to stimulate appetite
    • Remember that most pets will not eat the first day or two after they get home from surgery
    • Appetite stimulants such as cyproheptadine may be helpful
    • If your cat refuses to eat anything for 7 days a stomach tube or nasogastric tube should be placed to provide nutrition so that a serious liver problem (hepatic lipidosis) does not develop

My pet is vomiting.  What can be done?

  • The first thing for you to discern is whether your pet is vomiting or regurgitating.  Both will result in fluid or food being brought up.  Vomiting always will have heaving or retching of the abdomen prior to expulsion of the vomitus.  Regurgitation is not associated with heaving and the pet usually just opens the mouth and fluid or food will be expelled.  Usually the regurgited material will be clear or brown colored fluid. 
  • Next is to identify the cause of the vomiting or regurgitation.
  • Causes and treatment of vomiting after surgery
    • When some pets return home after a stay in the hospital they may drink excessive amounts of water at one time and then vomit; if this appears to be the case, the water should be limited to frequent smaller amounts.
    • Medications such as antibiotics, narcotics or nonsteroidal anti-inflammatory medication commonly cause vomiting after surgery.  In order to see which medication is causing the problem, the administration of each drug should be separated 2 hours apart.  Usually the pet will vomit or appear nauseated (drooling and sick look) within 1 hour of administration of the medication that they are sensitive to.  The antibiotic in some cases may be changed to a different one, or may be discontinued. 
    • Stomach upset from anesthesia is a potential cause of vomiting and will pass within a couple of days. 
    • An uncommon cause of vomiting after surgery is internal organ failure.  Blood testing will confirm this problem. For this reason vomiting should not be ignored if it persists for more than 24 hours.
    • If your pet had surgery of the bowels or stomach, vomiting is always a concern, as it may indicate that infection of the abdominal cavity, called peritonitis, is present.  Do not ignore this sign.
    • Symptomatic treatment of vomiting involves withholding food for 12 to 24 hours, then introducing small amounts of bland food such as rice and lean cooked hamburger, if your pet does not vomit after that then gradually wean him/her back onto the regular diet after 3 days.  In order to decrease the acidity of the stomach, Pepcid AC 0.5 mg/kg can be given by mouth twice daily for 5 days.  Metoclopramide and Cerenia are good anti-vomiting medications for dogs and cats.  You should always consult a veterinary healthcare professional before administering medication.
  • Causes and treatment of regurgitation after surgery
    • The most common cause of regurgitation is reflux of acid from the stomach into the esophagus while your pet is under anesthesia.  Acidic fluid from the stomach can cause a chemical burn of the esophagus and result in a bad case of heart burn, called esophagitis.  This results in poor motility of the esophagus, therefore water and food will accumulate in this structure.  In most cases, esphagitis is self-eliminating and will resolve within two or three days. 
    • If the esophagitis is severe the esophagus may develop one or more strictures.  A stricture is a narrowing or stenosis of the esophagus and does not allow passage of food down the esophagus, in regurgitation that lasts longer than one week.  This problem should be brought to the attention of your pet's doctor within the first two weeks so that it can be treated by ballooning the stricture (minimally invasive procedure, as it is done with the aide of an endoscope).  If an esophageal stricture is chronic surgery is needed.
    • Symptomatic treatment of regurgitation caused by esophagitis includes feeding bland food, and administering a coating agent (sucralfate) and an acid blocker (omeprazole or other).  Consult a veterinary health care professional if the regurgitation continues for more than a couple of days.

How do I know that my dog is in pain following surgery?

  • Signs of pain include
    • crying
    • biting if you get near the surgical site
    • grimacing (lips are pulled back and the the dog looks anxious)
    • tragic facial expression
    • panting
    • restlessness and unable to sleep; pacing
    • if abdominal surgery was done the pet will not lie down on the incision, or will continually sit up in spite of appearing very tired
    • the worst pain will be for the first 2 to 3 days after surgery

What can I do to control my dog's pain?

  • Narcotic medications that control pain: tramadol, butorphanol, Duragesic (fentanyl patch)
  • Anti-inflammatories used to control pain: Deramaxx, Rimadyl, Previcox, or Etogesic
  • If an orthopedic surgery has been done cold packing the surgical site may be helpful
    • A cold pack may be a pack of frozen peas, crushed ice in a Ziploc bag, or a cold gel pack; place a thin barrier between the skin and the cold pack.  An alternative to a cold pack is to freeze water in a styrofoam cup; after frozen cut the bottom of the styrofoam cup out. Cool the surgical site around the incision by rubbing the exposed ice directly on the skin in a circular pattern.  Cooling the surgical site helps to numb the area.

How do I know that my cat is in pain following surgery?

  • Pain is more difficult to assess in cats versus dogs, as signs can be more subtle and they usually do not vocalize when in pain
  • Signs of pain in a cat include the following:
    • biting if you get near the surgical site
    • growling or deep cry
    • not wanting to eat
    • hiding and not wanting to be near owner (remember that this could also be caused by the cat just being upset about leaving home and coming back)

What can be done for pain at home for my cat?

  • Pain medication such as buprenorphine or a Duragesic (fentanyl) patch
  • Tylenol will kill a cat as they lack abundant glutathione enzyme in the liver
  • Anti-inflammatories can be used, but the dose is much less than dogs

Is it okay for my pet to lick the incision?

  • If a dog licks the incision, the healing process may be delayed.
  • Licking can remove stitches and cause the incision to open
  • Licking can become a severe habit that is difficult to break
  • Licking can cause infection as the mouth has many bacteria
  • Dogs will frequently lick the incision when the owner is not watching such as at night time; if the skin looks red or excoriated the most common cause is from licking.
  • To stop your pet from licking the following can be tried:
    • Elizabethan collar can be placed on the neck; this will not help stop your pet from scratching at the region
    • Cervical collar (bite not collar) is a less awkward device and can be effective at stopping a pet from licking the surgical site
    • A tee shirt can be used to cover an incision on the chest or front part of the abdomen; gather the waist of the shirt up over the dog's back and wrap an elastic band around this part of the shirt.
    • A bandage or sock can be used to cover an incision on a limb; fasten the top of the sock to the dog's limb with tape.
    • Bitter apple can be applied around the incision; many dogs will continue to lick  after application of this topical
    • Bitter Apple and Liquid HeetTM (obtain this from a drugstore...it is used for sore muscles) mixed in a 2:1 ratio can be applied around the skin incision
    • Antipsychotic medication in some cases is needed

Board-certification by the American College of Veterinary Surgeons

What does it mean?

  • Four years of advanced training in surgery beyond the Doctor of Veterinary Medicine Degree

  • Experience in the development of new surgical treatments

  • Rigorous examination by the American College of Veterinary Surgeons to ensure competency in advanced surgical techniques

  • Assurance that a veterinarian is a surgical specialist

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