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Musculoskeletal and Nervous System Injuries, Disorders, and Diseases

Musculoskeletal and Nervous System Injuries, Disorders, and Diseases

By Arnold Plotnick, DVM

Even though cats walk on all fours, compared to humans who walk upright, the feline skeleton and the human skeleton are fairly similar. Cats have more bones than humans (230 vs. 206), but that's primarily due to the tail bones. Feline muscles are strong and well-constructed, as you'd expect for such an agile hunter. The nervous system can be divided into two main portions: the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS includes the brain and the spinal cord. The PNS is made up of all of the rest of the nerves that are found throughout the body. The nervous system and the musculoskeletal system work together like a well-oiled machine, allowing the cat to finely coordinate her activities, like running, jumping, and pouncing. Despite their exceptional athletic ability, cats do not always land on their feet; injuries and disorders of the musculoskeletal and nervous system do occur in cats, although less commonly than in their canine counterparts.

Musculoskeletal Injuries and Disorders

Musculoskeletal Injuries and Disorders

The skeleton can be divided into two parts: the axial skeleton-the skull, spine, ribs, and sternum-and the appendicular skeleton, which comprises the front and hind legs, as well as the hips and shoulder blades. Although cats are very limber and coordinated, their bones are fairly fragile, and orthopedic injuries such as broken bones are common. Ligaments are strong pieces Bibleof connective tissue that connect bones to other bones. Ligament injuries are not as common in cats as in dogs, but they do occur.

Despite the adage, a cat does not always land on her feet, and a fall from a height can cause her injury.

Luxating Patella

Luxating Patella

The patella is the kneecap. In order for the rear legs to flex and extend properly, the patella needs to glide within the natural groove that is present at the end of the femur (thigh bone). In some cats, the patella does not glide properly in the groove. It slips out of the groove, usually toward the inside (medial) part of the leg (as opposed to the outside or lateral part). Cats with this problem are said to have a medial patellar luxation (MPL). It is much more common in dogs, however, than in cats.

Causes and symptoms

The most common cause of MPL in cats is developmental; cats are born with a tendency to develop the problem, usually within the first year of life. Severe cases may lead to lameness problems early in the cat's life, but this is rare. Most cases show no symptoms at all. As the cat ages, mild cases of MPL may progress in severity, eventually leading to persistent lameness. Again, this is uncommon. Cats with this condition are rarely bothered by it. Trauma is the second most likely cause of MPL in cats, usually as a result of being hit by a car.The main clinical sign of MPL is lameness. This can vary from a very mild limp to a complete lameness, with the cat's not being able to bear weight on the affected limb.

Diagnosis and treatment

Diagnosis is based mainly on physical exam findings. During an orthopedic examination, the veterinarian will manipulate the patella to see whether it is firmly in its groove or can easily be displaced. Both knees will be evaluated. In many cases, the luxation is bilateral, although there may be differing degrees of severity between knees. x-rays may be useful in confirming the diagnosis. Treatment varies, depending on the severity of the MPL and the cat's clinical signs. Mild cases may not require treatment or may be managed with a short course of pain medication. More severe cases may require surgery. The most common surgery for MPL involves deepening the groove that the patella glides in, making the kneecap less likely to pop out of place. Most cats respond well to surgery and are walking normally several weeks later. However, arthritis is likely to develop in the joint later in life.

Radiographs showing metal plates implanted to fix a cat's fractured leg.

Ruptured Cruciate Ligament

Ruptured Cruciate Ligament

The cruciate ligaments are two bands of fibrous tissue found in the knee joint, one running toward the front of the joint (the cranial cruciate ligament), the other situated toward the rear of the joint (the caudal cruciate ligament). The ligaments cross in center of the joint-hence the name cruciate, from the Latin, meaning "cross"-keeping the tibia (shin bone) and the femur (thigh bone) stable and properly aligned relative to each other. Although not a common occurrence in cats, a cruciate ligament (specifically, the cranial cruciate ligament) can suffer a tear or rupture, leading to lameness.

Causes and symptoms

By far the most common cause of a torn cruciate ligament is some type of trauma, such as landing improperly after a jump, falling from an elevated height, or being hit by a vehicle. The severity of the lameness depends on the type of injury. An acute, sudden tear can lead to lameness so severe that the cat cannot bear weight on the limb at all. Tears that occur as a result of a slow, progressive breakdown of the ligament usually cause milder clinical signs such as an intermittent limp.

Diagnosis and treatment

Diagnosis is made on physical examination. After observing your cat walk, your veterinarian will perform an orthopedic exam on the affected rear leg. While holding the tibia and the femur firmly, your veterinarian will see whether the tibia can be moved excessively in a forward motion compared with the femur. This excessive movement is called cranial drawer and indicates that the cranial cruciate ligament is torn. x-rays may be helpful in supporting the diagnosis. Most cats require surgery to repair the ligament. Some cats may be able to recover from their lameness without surgery, but healing takes time, and the cat has to be restricted from exercising the affected leg. This may require confinement in a cage for several weeks. Cats who do not respond to conservative treatment (rest and anti-inflammatory medication) will need to have the ruptured ligament surgically repaired. Most cats do well after surgery, although the affected knee may become arthritic as the cat ages. Overweight cats do much better if they are put on a diet to lose weight.

Kitten with a broken leg. Falls are the most common cause of broken bones in cats.

Soft-Tissue Injuries

Soft-Tissue Injuries

Although cats are very agile creatures, they occasionally suffer sprains and other soft-tissue injuries to the limbs and joints. In most cases, the tissue damaged is a ligament.

Causes and symptoms

The most common cause of these injuries is trauma-such as being hit by a car, falling from a window or other high area, or as a result of running or playing. Signs of a sprain include pain, swelling, and lameness in the affected limb. The signs can vary in severity, from a barely perceptible limp to a complete non-weight-bearing lameness.

Diagnosis and treatment

In most cases, the diagnosis can be based on the physical exam Biblefindings along with a history of trauma. x-rays may be necessary to rule out a fracture or dislocation, which can have similar clinical signs. Mild sprains and soft tissue injuries heal on their own over the course of a few days. Anti-inflammatory medication may be warranted for cases in which there is obvious discomfort. More severe cases may require a splint to protect and support the affected joint, as well as strict confinement. The incidence of sprains (and more serious traumatic injuries) can be reduced by keeping cats indoors.

Nervous System Disorders, Diseases, and Injuries

Nervous System Disorders, Diseases, and Injuries

As with the other body systems, the nervous system is susceptible to a variety of ailments. Diagnosing neurological disorders can be especially challenging because many of the clinical signs are subtle, intermittent, or subjective. Sophisticated equipment is often required to achieve a definitive diagnosis of some neurologic disorders, such as disc disease and brain or spinal tumors, and may warrant a visit to a referral center or veterinary university.

Intervertebral disc disease is less common in cats than in dogs, but it can occur in cats of any breed.

Brain Tumors

Brain Tumors

Brain tumors are uncommon in cats, but they do occur. Tumors can be primary (the tumor originated in the brain) or secondary (the initial tumor originated elsewhere in the body and has spread to the brain).

Causes and symptoms

The most common brain tumor in cats is a meningioma. This is a tumor that arises from the membranes that cover the brain. The next most common brain tumor is lymphoma. Clinical signs of a brain tumor depend on the size, location, and rate of growth of the tumor. Primary brain tumors tend to grow slowly, initially allowing the brain to adapt. During this time, there may only be vague, subtle behavioral changes. Clinical signs progress as the tumor continues to grow. Common signs include altered mental attitude, seizures, blindness, walking in circles, and compulsive pacing.

Diagnosis and treatment

Making the diagnosis can be challenging. Common tests, such as blood tests or x-rays, rarely allow for a diagnosis. Advanced imaging techniques, such as computed tomography (CT) or magnetic resonance imaging (MRI), are often necessary.

Depending on their location, some meningiomas can be surgically removed. Cats typically show marked improvement within several days after surgery. Cats who had seizures before the surgery may continue to have seizures after the tumor is removed and will continue to require anticonvulsant medication. Brain surgery in cats requires special equipment that is often only available at universities and referral centers. Although lymphoma is generally not treatable via surgery, it may respond to chemotherapy, radiation, or a combination. For tumors that are not amenable to surgery or that fail to respond to chemotherapy and/or radiation, palliative therapy with antiinflammatory medications may lead to significant improvement in clinical signs. Unfortunately, this is usually short-lived. Unless the tumor can be removed completely, most cases of brain cancer have a guarded to poor prognosis.

Disc Disease

Disc Disease

Between the individual bones of the spine (the vertebrae) are structures called discs. The discs have a hard outer surface and a soft inner core, similar to a jelly doughnut. The discs act as cushions between the vertebrae.

Causes and symptoms

Intervertebral disc disease (IVDD) is a condition that occurs when one or more discs get compressed between the vertebrae. This causes the "jelly" inside to leak out, or herniate, irritating or damaging the spinal cord just above it. Herniation of disc material can occur suddenly as a result of trauma, or it can happen gradually. IVDD is much more common in dogs than in cats.

The signs of IVDD can vary, from mild back pain to complete paralysis of the front and/or rear legs. In most cases of feline IVDD, the disc problem occurs in the mid to lower spine. If paralysis occurs, the front legs are often spared, with only the rear legs affected. Other possible signs of IVDD include reluctance to play, crying in pain when picked up or petted along the spine, reluctance to jump or climb stairs, and an uncoordinated gait.

Diagnosis and treatment

To diagnose IVDD, your veterinarian will perform a complete neurologic examination. Once a neurologic problem is confirmed, other diagnostic tests will likely be necessary. X-rays can sometimes help point to the suspected area of the spinal cord that is being compressed, but a definitive diagnosis often requires more advanced techniques such as a CT scan, an MRI, or a myelogram. A myelogram is a procedure in which a dye is injected into the spinal canal, allowing for better visualization of the spinal cord on X-rays. The exact location of the spinal cord compression can then be determined. Treatment for IVDD depends on how severely the cat is affected. Mild signs of IVDD can often be treated with strict cage rest, anti-inflammatory medication, and muscle relaxants. More severe cases may require surgery to remove the extruded disc material and relieve the pressure on the spinal cord. The prognosis in mild cases is favorable. For cats who require surgery, the prognosis depends on how severely the spinal cord was damaged and whether the surgery to remove the extruded disc material was done in a timely fashion. It may take several weeks or months for a cat to recover from a spinal cord injury.

Landing on Their Feet

Despite their flexible muscular bodies and excellent righting reflex, many cats have acquired severe injuries after falling only a short distance. Any windows that a cat has access to should have strong, intact screens, and rooftops and unscreened balconies should be off limits to your cat.

Feline Hyperesthesia Syndrome

Feline Hyperesthesia Syndrome

Feline hyperesthesia syndrome (FHS) is an uncommon, mysterious condition that manifests as a variety of behavior changes, the most common being a heightened sensitivity to touch especially over the lower back and rump.

Causes and symptoms

Most affected cats will become fixated on their tails, swishing them back and forth, chasing them, frantically overgrooming them, or viciously attacking them. The skin along a cat's back may twitch or ripple, and a cat may show sudden bouts of bizarre hyperactive or aggressive behavior. Other signs that may accompany this condition are sudden mood swings, in which cats can go from extremely affectionate to aggressive, increased vocalization, and apparent hallucinations, manifested in behavior such a cat's appearing to follow the movement of something that isn't there or running away from some unseen adversary. Some people find this behavior amusing and will jokingly describe their cat as being "possessed." Abyssinians, Burmese, Himalayans, and Siamese are especially prone to the condition, although any breed may be affected. The cause of FHS remains elusive. Some people think that it is some type of seizure activity. Others feel that it is a form of obsessive-compulsive behavior. The fact that Oriental breeds are somewhat predisposed to FHS suggests a possible inherited tendency. Stress is considered to be a factor in this disorder.

Diagnosis and treatment

There is no specific test for FHS. Diagnosis is based on the clinical signs and ruling out other medical disorders, such as hyperthyroidism or skin allergies. Treatment involves reducing stress in the cat's environment. Some behaviorists recommend allowing the cat to "blow off steam" by encouraging predatory play activities using interactive toys such as feather toys on a string or a wand and laser toys. This helps reduce any bottled-up prey drive the cat may have. Actions that trigger the behavior, such as petting or scratching near the base of the tail or the rump should be avoided. In cases in which the symptoms occur spontaneously or where symptoms are severe, medical therapy may be warranted. Anti-obsessional drugs, such as fluoxetine (Prozac), have been shown to be effective. Anticonvulsant medication, such as phenobarbital, is also effective for this condition. Severely affected cats can usually live a normal life if treated appropriately.

The Abyssinian is one of the breeds that is most susceptible to feline hyperesthesia syndrome.

Idiopathic Vestibular Disease

Idiopathic Vestibular Disease

The vestibular system in the cat comprises nerves and sensors that start in the brain and extend to the inner ear. It is responsible for a cat's balance and coordination. Occasionally, a disorder of the vestibular system arises, and cats become dizzy and lose their balance.

Causes and symptoms

This disease is typically manifested through a variety of clinical signs, such as tilting the head, walking in circles or as if drunk, stumbling, falling, incoordination, and nystagmus (a back and forth beating motion of the eyes). In severe cases, the cat may not be able to stand at all. Although vestibular disease can occur as a result of inner ear infections, thiamine deficiency, poisonings, and tumors or polyps in the middle ear, in most cases an underlying cause is never determined and the condition is referred to as idiopathic (meaning "no known cause").

Diagnosis and treatment

In dogs, idiopathic vestibular disease typically affects older animals. In cats, however, the disorder can strike at any age. The sudden onset of signs can be drastic and frightening to owners and often causes them (and some veterinarians) to mistakenly diagnose cats as having suffered strokes. It is not a stroke, and euthanasia should not be considered. Idiopathic vestibular disease in cats usually shows rapid, dramatic improvement over twenty-four to seventy-two hours, and most cats are completely back to normal two weeks after the initial onset of clinical signs. Severely affected cats may need to be isolated to a small area so that they don't injure themselves by trying to go up or down stairs or jump on furniture. Obviously, they should be prevented from going outdoors until fully recovered. If confinement at home isn't possible, the cat can be admitted to the veterinary hospital and kept in a cage with blankets and protective soft bedding to prevent injury. Cats who developed a head tilt at the onset of clinical signs may continue to have one after recovery; the head tilt has no effect on the cat (other than giving him an unusual appearance).

If your cat has a seizure, take her for examination by a veterinarian as soon as possible after the seizure ends.

Seizures/Epilepsy

Seizures/Epilepsy

Few things are more upsetting for a cat owner than witnessing his or her beloved companion in the throes of a seizure. Luckily for cat owners, feline seizure disorders are fairly uncommon. Whereas epilepsy affects up to 3 percent of the canine population, cats are much less susceptible.

Causes and symptoms

Seizures can vary in severity, from a mild episode of acting spacey to a severe episode in which a cat falls on her side, gnashes her teeth, salivates, paddles all four limbs, and loses bowel and bladder control.

The term primary epilepsy implies that the seizures are due to a primary brain disorder. Trying to prove that a cat has primary epilepsy can be difficult. Epileptics appear normal on physical examination and on neurological examination, and diagnostic tests, including advanced imaging tests like CT or MRI, show no abnormalities. This, in fact, is how the diagnosis of primary epilepsy is achieved: by exclusion of other causes of seizures.

Secondary epilepsy suggests that the seizures are associated with an underlying structural disorder, such as inflammatory disease, trauma, or cancer. This is seen more commonly in cats than in dogs. Metabolic diseases and toxicities can lead to seizures in cats. Infectious causes that should be considered in cats with seizure disorders include feline infectious peritonitis (FIP), feline leukemia virus (FeLV), feline immunodeficiency virus (FIV), Cryptococcus (a fungal infection), and rabies (extremely rare). Toxoplasmosis is an uncommon cause of seizures in cats. Up to 20 percent of cats presenting with acute onset of seizure activity may have cerebral ischemic encephalopathy, a condition in which the brain is damaged due to decreased blood flow to a part of the brain (similar to a stroke). In most cases of cerebral ischemic encephalopathy, the cause is never determined. Cancer is a possible cause of seizures in cats, with the most common brain tumor being a meningioma, a tumor arising from the membranes covering the brain. Another possible cause of acute seizure activity in cats is the larva of the parasite Cuterebra migrating through the brain.

Diagnosis and treatment

If your cat has a seizure, don't panic. Take note of the time the seizure begins. It may seem like forever but, in fact, most seizures last from thirty seconds to two minutes. Clear away any objects that the cat might hit during the seizure, such as furniture, and protect her from stairs or water. Do not attempt to hold the cat's mouth open or closed; airway obstruction by the tongue rarely occurs. Provide gentle restraint during the seizure by holding a light blanket or towel over the cat. Afterward, confine the cat and monitor breathing and pulse. Do not be alarmed if your cat vocalizes or stumbles after the seizure ends; this is common.

Cats who have experienced a single, short seizure should be evaluated by a veterinarian as soon as practical. If, however, the seizure lasts longer than three or four minutes, or if more than one seizure has occurred in a twenty-four-hour period, or if a new seizure begins before the cat has fully recovered from the first seizure, the cat should be taken to an emergency clinic for immediate evaluation. A thorough history and a comprehensive physical and neurologic exam, including an eye exam that evaluates the retinas, should be done in all cats with a history of seizures. A complete blood count, serum biochemistry panel, urinalysis, and evaluation of infectious disease status (FeLV, FIV, FIP, Toxoplasma, Cryptococcus) should be performed or considered. If neurologic abnormalities are detected on physical examination, further testing is advised. This may include doing a "spinal tap" and obtaining a sample of the cerebrospinal fluid (the fluid that bathes the brain and spinal cord), as well as advanced imaging tests such as a CT scan or MRI. Cats with seizures may require anticonvulsant medication. Unfortunately, the number of drugs that have been developed or recommended for seizure control in cats is limited. Phenobarbital remains the first choice of anticonvulsants in cats. For cats who do not tolerate phenobarbital, diazepam (Valium) is usually the second choice of most veterinarians. Recently, the drug levetiracetam (Keppra) has shown promise in controlling seizures in cats who do not respond well to phenobarbital. Once cat starts taking anticonvulsant medication, it needs to be continued for the remainder of the cat's life.

Burmese Craniofacial Defect

Burmese Craniofacial Defect

Burmese breeders in North America bred their cats toward a different physical conformation than breeders in Europe and much of the rest of the world. While European breeders maintained the semi-foreign conformation and a wide range of colours (which preserved a wide gene pool), North American breeders selected for a cobbier Burmese with a more domed head and stuck to the four original colours. This meant a small number of stud cats, with the desired domed head shape, were much in demand, and their genes became widespread in the American Burmese gene pool. In later generations, when carriers were bred together, deformed kittens appeared. As a result of the craniofacial defect, British cat registries banned the use of imported American Burmese as outcrosses for the European Burmese.

Affected kittens have a normal lower jaw and tongue, but the upper jaw, the upper part of the muzzle, and the roof of mouth are duplicated. The area above the muzzle is incomplete; the ears and eyes are malformed and the skull doesn't close completely, leaving part of the brain covered with skin only. Affected kittens are usually stillborn or die soon after birth. Those that survive must be euthanized due to the devastating nature of this deformity. Responsible breeders have identified and neutered carriers of the defect, and the deformity is encountered less often. It is not possible to completely eliminate recessive mutations without genetic screening. Some lines of American Shorthair are affected by a similar syndrome, also due to breeders wanting to create a more domed head shape.

Spinal Trauma

Spinal Trauma

Trauma to the spinal cord is an uncommon occurrence in cats, but when it does happen, the effects can be devastating.

Causes and symptoms

The most common cause is vehicular trauma, although gunshots and falling from a height are other possibilities. Signs of spinal cord injury often reflect on the cat's ability to walk. Affected cats will show varying degrees of lameness, from a mild limp to incoordination to complete paralysis.

Diagnosis and treatment

Cats with suspected spinal injuries should be evaluated by a veterinarian immediately. To prevent further injury, immobilize the cat before transporting her. Lay her on a board and immobilize her with straps, cords, or tape, paying special attention to the head and neck. Alternatively, wrap the cat in a blanket or a coat to immobilize her. Gently lower the immobilized cat into a large box or secure container for transport to a veterinarian. Diagnosis is based on a history of recent injury, physical examination, and other diagnostic tests, such as x-rays, a CT scan, or an MRI. Treatment depends on the type and severity of injury. Treatment can be medical, surgical, or both. Medical therapy involves giving anti-inflammatory drugs to prevent swelling and inflammation of the spinal cord. Surgery may be necessary in cases of fracture or dislocation or in cases in which the neurologic signs are getting worse despite medical therapy. Severe fractures or dislocations may not be treatable with surgery or medical therapy, and euthanasia should be considered in these cases.

Spinal Tumors

Spinal Tumors

Tumors of the spinal cord are uncommon in cats. Of the tumors that do occur, the most common one affecting the feline spinal cord is lymphoma.

Causes and symptoms

Most affected cats are young (average age is twenty-four months), and most of these cats are concurrently infected with FeLV. In fact, the virus is believed to be the cause of the lymphoma. Spinal lymphoma tends to grow slowly, progressing over several weeks or months. The clinical signs of spinal lymphoma vary depending on where in the spinal cord the tumor is located and how rapidly the tumor is growing. Tumors that involve the meninges (the membranes covering the spinal cord), the spinal nerves, or the nerve roots may cause varying degrees of pain, from mild discomfort to extreme sensitivity. Lameness, progressing to partial or total paralysis, is commonly seen.

Diagnosis and treatment

Diagnosis can be challenging and often requires advanced imaging techniques, such as a CT, an MRI, or a myelogram. As noted earlier, a myelogram is a procedure in which a dye is injected into the spinal canal to allow better visualization of the spinal cord. This procedure often reveals the location of the spinal tumor. Other tests, such as a complete blood count, a FeLV test, and a bone marrow analysis, may yield information supportive of the diagnosis. Treatment depends on the location and severity of the tumor. Surgery may be warranted to relieve pressure on the spinal cord. Some tumors, such as a meningioma (a tumor arising from the membranes covering the spinal cord) may be treatable by surgical removal. However, the most common tumor-lymphoma-is usually not amenable to surgery. Currently, the recommended treatment for cats with spinal lymphoma is radiation and chemotherapy. Although cats may initially respond to treatment, the prognosis in general is poor, with most cats succumbing to their illness a few weeks or months after treatment.

From The Cat Bible, Copyright by Sandy Robins, licensed through ContentOro, Inc and used by arrangement with I-5 Press

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