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Nervous System

Spina Bifida

Spina bifida is a birth defect that affects not only people but also dogs and cats. During gestation, the vertebrae typically grow around the spinal cord. When they fail to complete this developmental step, the spinal cord is left exposed at birth. If not immediately obvious upon whelping or queening, symptoms of spina bifida will show up as soon as a puppy or kitten begins to walk. Weakness in the back legs and an unsteady gait may be evident, or the animal could be incontinent, depending on the severity of the defect. In some cases, surgery can make small repairs, such as preventing spinal cord exposure through the skin, but in most cases, there is no procedure that can completely reconstruct the vertebrae. As a result, spina bifida is often an extreme disorder with a bleak outcome.

Overview

Spina bifida is a congenital abnormality of the spine in which the vertebrae fail to develop normally. Depending on the severity of the defect, it can manifest as anything from a devastatingly malformed, exposed spinal cord to a wholly inconsequential, incidental finding observed only on X-rays and for which the patient requires no treatment.

The lumbar spine (lower back) is most commonly affected, though it’s possible for any part of the spine to be affected. Several adjacent vertebrae are usually involved, though very mild cases may affect only one vertebrae. Unfortunately, the mode of inheritance of this defect has not been determined. Other possible causes include exposure to drugs or toxins that cause birth defects, nutritional deficiencies and maternal stress during pregnancy.

Symptoms and Identification

Severely affected puppies and kittens are usually identified as spina bifida patients when they’re born –– that is, if their spinal cords are exposed. In these cases, the pets are predisposed to meningitis, or an inflammation of the covering of the spinal cord, which worsens the prognosis. Others, however, are flagged as potential candidates when they begin walking. The signs are usually associated with the location of the deformity within the spinal column. Hind limb weakness or a stumbling gait are common findings. Some patients may also experience urinary or fecal incontinence.

At this point, diagnosis is undertaken using basic radiographic (X-ray) techniques to demonstrate the incomplete vertebrae. Myelograms, or radiographic studies using dye, and CT scans may also be helpful in these instances.

Affected Breeds

The English Bulldog is the breed most commonly affected by spina bifida. Among cats, the tailless Manx is over-represented.

Treatment

Severe cases of spinal disorders like spina bifida are considered untreatable. Pups and kittens are typically euthanized immediately upon diagnosis.

It may also be the case that no treatment is necessary, for example in those cases in which the deformity is detected incidentally upon routine radiography or X-rays undertaken for another issue altogether.

Prevention

There is no known form of prevention beyond genetic counseling to recommend the sterilization of affected animals and their first-degree relatives.

 

Motion Sickness in Dogs

A car ride! A car ride! A car ride! For most dogs it’s the greatest thing since the cookie. But a dog can get motion sickness just like people do, which can mean that even a short car trip becomes stressful for the dog — and disgusting for the owner. Fortunately, there are ways to ease or eliminate a dog’s motion sickness, including conditioning and medication.

Overview

Motion sickness is much more common in puppies and young dogs than in older dogs, presumably because the ear structures used for balance aren’t fully developed in puppies. If the first few car rides of a dog’s life result in nausea, the dog may begin to equate travel with uncomfortable sensations, even after his or her balance system fully matures. Therefore, a dog who suffers motion sickness should be treated as soon as possible.

Stress can also add to motion sickness; if a dog rides in a car only to go to the veterinarian the negative sensations associated with travel can be more pronounced. If a dog continues to appear ill even after several car rides, the owner should consult a veterinarian about treatment for motion sickness.

Signs and Identification

Not all motion sickness manifests as vomiting. Signs of motion sickness in dogs include:

  • Inactivity
  • Listlessness
  • Uneasiness
  • Yawning or panting
  • Whining
  • Excessive drooling
  • Vomiting (even on an empty stomach)
  • Fear of cars

If a dog develops a secondary fear of riding in cars, a veterinarian or veterinary behaviorist can help determine whether the cause is motion sickness or something else, such as an orthopedic condition or anxiety unrelated to motion sickness.

Affected Breeds

All breeds of dogs seem equally susceptible to motion sickness.

Treatment

To help owners prevent or treat motion sickness in dogs, veterinarians often recommend one or more of the following approaches:

  • Help your dog face forward while traveling by strapping him or her into the seat with a specially designed canine seatbelt.
  • If you buckle your dog into the front passenger seat, position the seat as far as possible from the dashboard or disable the passenger air bag, which can be hazardous to dogs.
  • Lower car windows a few inches to equalize the inside and outside air pressures.
  • Keep the vehicle cool.
  • Limit your dog’s food and water consumption before travel.
  • Give your dog a treat or two every time he or she gets into the car.
  • Give your dog a toy that he or she enjoys and can have only in the car.
  • Give your dog a one- to two-week break from car rides.
  • Use a different vehicle to avoid triggering your dog’s negative response to your usual vehicle.
  • Take short car rides to places a dog enjoys, such as the park, especially if your dog associates car rides only with trips to the veterinarian’s office.

Gradually build up a dog’s tolerance to car rides. The following steps should take a few days to a week:

  1. Accustom your dog to approaching the car without getting in it.
  2. Spend time with your dog in the car with the engine off.
  3. Take short trips (e.g., around the block).
  4. Take longer trips. Reward your dog with praise and/or treats every time he or she does something well.

If a dog doesn’t outgrow motion sickness or respond to conditioning techniques, consult your veterinarian about medication to help your dog. There is a medication approved for preventing vomiting due to motion sickness in dogs. However, if anxiety or other issues are involved, additional therapies may be recommended.

Prevention

In many cases treatment and prevention are the same thing, so see the list above.

Hydrocephalus in Cats and Dogs

Hydrocephalus, which literally means “water on the brain,” is a buildup of fluid inside the skull. This accumulation puts pressure on the brain, causing signs such as an enlarged, dome-shaped head, seizures, blindness, and behavioral changes. The condition is often congenital, meaning that is present before or at birth, and can occur in both dogs and cats. Small dogs are particularly susceptible. In mild cases, drugs can help treat signs, but severe cases often end in euthanasia, as surgery is costly.

Overview

With hydrocephalus, cerebrospinal fluid (CSF) accumulates inside the skull and the brain. The congenital form of hydrocephalus is called primary hydrocephalus. Secondary hydrocephalus is acquired later in life and is often associated with tumors, trauma, or inflammation, which may block the flow of CSF or alter the normal production or drainage of the fluid. Only the primary form will be discussed here.

Congenital hydrocephalus can be caused by a number of factors, including heredity, prenatal infection, exposure to drugs that cause birth defects, and trauma from a difficult birthing process. After birth, they experience fluid buildup, which exerts damaging pressure on the brain.

Symptoms and Identification

Affected animals will typically begin showing signs of head enlargement in the first weeks after birth. This is because the bones of the skull have not yet fused, making enlargement possible. Once the skull reaches its growth limit, the fluid continues to build, causing pressure on the brain and leading to neurological symptoms, which usually start around eight to twelve weeks.

Young animals with hydrocephalus are often the “runt” of the litter, being smaller in size than littermates and slower to learn. Approximately 75 percent of diagnosed canines were reportedly impossible to housebreak.

Other signs can include seizures, head pressing, eyes that gaze downward and outward (called ventrolateral strabismus), gait abnormalities and blindness. Some pets with hydrocephalus may show no clinical signs, or have signs that gradually worsen over time.

Diagnosis is often presumed, based on history and physical examination, without taking additional steps to confirm the condition. Severe cases, however, will become unmanageable well before then and require a definitive diagnosis via CT scan or MRI in order to determine the extent of fluid accumulation. If available, EEG, or electroencephalography, may help support the diagnosis of hydrocephalus. An ultrasound can also be helpful but may only be possible when the skull has not fused completely. Even when hydrocephalus is diagnosed, the underlying cause is often unknown.

Affected Breeds

Small dogs are predisposed to the condition, including Cairn Terriers, Chihuahuas, Maltese, Pomeranians, Toy Poodles, Yorkshire Terriers, Boston Terriers, English Bulldogs, Lhasa Apsos, Pekingese, Pugs, and Shih Tzus. Siamese cats may also be predisposed to the condition.

Treatment

Definitive treatment involves a shunt that redirects CSF from the sensitive site surrounding the brain to a more benign location, such as the abdominal cavity, where it can be easily reabsorbed. Because the procedure is expensive, and requires a specialized brain surgeon, most canines never receive it.

Symptomatic treatment can include drug therapy to reduce seizure activity, corticosteroids to relieve brain swelling and inflammation, and diuretics to reduce the amount of fluid. However, most medical treatment only provides a temporary solution to the problem.

Unfortunately, euthanasia is the most common outcome for pets that suffer anything but the mildest signs of the disease.

Prevention

All affected dogs should be removed from the breeding pool. Any animals with a family history of hydrocephalus should be considered carefully during breeding selection.

Epilepsy and Seizures in Pets

Epilepsy is a brain disorder that strikes humans as well as pets. While this condition is relatively rare in cats, it is common in dogs. Unpredictable, recurring seizures caused by an electrical ”storm” in the brain are the hallmark of epilepsy. A diagnosis of epilepsy is made only after all other reasons for such seizures have been ruled out. Although there is no cure for epilepsy, frequent seizures can typically be managed with drugs.

Summary

A seizure consists of spontaneous, uncontrolled movements such as trembling, twitching or leg paddling, or changes in consciousness or behavior, which are caused by electrical abnormalities in the brain. Seizures can be localized, such as in areas of the face, or generalized, involving the entire body. During a seizure, a pet may salivate, and lose bladder or bowel control. It is common for pets to appear disoriented for minutes or hours after a seizure.

In many cases, a seizure may be an isolated event, brought on by any number of reasons, such as low blood sugar, infectious diseases, toxins, kidney or liver failure or trauma. Anything that puts pressure on the brain, such as a tumor, can also cause seizures. Treatment of the underlying cause can often resolve the seizure activity.

When seizures recur over a period of weeks, months and years, the condition is known as epilepsy. Epilepsy is often called “idiopathic epilepsy,” meaning that the exact cause of recurring seizures cannot be identified.

Epileptic dogs can present at any age, but most will make their disease known via owner-observed seizure activity before the age of five. The condition may have varying degrees of severity and amenability to treatment. While very mild cases carry an excellent prognosis, a few dogs can suffer from an intransigent form that leads almost inevitably to euthanasia. Most dogs, however, fall somewhere in the middle.

Based on the evaluation of breed and line-specific predispositions to epilepsy, it’s suspected that this disorder may be inherited. The mode of inheritance, however, has not been worked out and seems to vary depending on the affected breed. Multiple genes may be involved in some cases.

Symptoms and Identification

Signs may vary widely in terms of the length, frequency, and general manifestation of the seizures. Generally, signs may include trembling, twitching, paddling of limbs, salivation, urination, defecation and changes in consciousness. While most seizures only last a few minutes, pets experiencing seizures of longer duration should be seen by a veterinarian immediately. In most cases, the timing of the seizures is effectively unpredictable.

Typically, idiopathic epilepsy is diagnosed only after all other obvious causes of seizures have been eliminated from the list of possibilities. A physical examination and basic laboratory testing (complete blood count, chemistry, urinalysis) are usually recommended. Toxicology studies, specific testing for infectious diseases and cerebral spinal fluid analysis can be very helpful as well, especially for patients with severe or seemingly progressive symptoms. Advanced imaging studies (MRI or CT scan) are strongly recommended for middle-aged to older animals to rule out the possibility of brain tumors or other lesions.

Affected Breeds

Epilepsy can occur in all breeds of dogs. Those most affected include the Belgian Tervuren, Beagle, Bernese Mountain Dog, Cocker Spaniel, Collie, German Shepherd, Golden Retriever, Irish Setter, Keeshond, Labrador Retriever, Poodle, Miniature Schnauzer, Saint Bernard, and Wirehaired Fox Terrier.

Treatment

Idiopathic epilepsy itself is considered incurable, but the disease can be managed with the long-term use of drugs. These medications typically serve to raise the brain’s resistance to the abnormal electrical impulses that trigger seizures.

The most common drug used for dogs is phenobarbital, but several other choices exist for chronic therapy if this drug produces intolerable side effects or if seizures remain uncontrolled. Unfortunately, almost all other drug choices are significantly more expensive. In almost all cases in which drug therapy is elected, frequent monitoring of these patients (typically through serial lab work) is necessary.

For more severe sufferers, however, treatment may also include hospitalization to manage more severe episodes during which prolonged seizure activity can lead to life-threatening consequences.

Some dogs, however, may not require any treatment at all. Dogs with infrequent seizures may, in fact, be more amenable to experiencing the occasional seizure than to risking the side effects of the drugs used to treat them.

Prevention

There is no known mode of prevention for idiopathic epilepsy save a dedicated breeding program that seeks to eradicate the trait via sterilization of affected animals and at least all first-degree relatives.

Some seizures may be prevented by avoiding specific drugs that can reduce the seizure threshold.