Max's House
Disorders of The Nervous System
The nervous system involves a complex interaction between special elements designed to originate or to carry unique electrochemical charges to and from the various organs within the body. Like its endocrine counterpart, the nervous system initiates and regulates body functions and assures its owner of an awareness to its surrounding environment.
Paralysis can be defined as a disruption of the nervous system leading to an impairment of motor function and/or feeling to a particular region or regions of the body. This impairment can be in the form of a spasticity of the muscles in the involved region, or these muscles might become completely limp. In either case, the muscles involved are unable to function in the manner in which they were intended.
Paralysis involving the sensory portion of the nervous system can result in either an increased sensitivity to or a complete absence of pain. Paralysis resulting in the inefficient function of certain internal organs can occur as well if the nerves supplying these structures are disrupted in any way. If the bladder or colon is involved, this can lead to elimination disorders.
Trauma to the vertebral column and spinal cord is one of the most common sources of paralysis seen in cats. Fractured vertebrae resulting from encounters with moving automobiles, fractious dogs, or other sources can result in a partially or completely torn spinal cord in the region of the fracture(s). Neoplasia and infectious or parasitic agents can also cause inflammation and tissue damage in the spinal cord of cats, leading to functional deficits. Lymphosarcoma is probably the most prevalent tumor seen affecting this structure, and classically causes hind-end paralysis. Feline infectious peritonitis is a viral disease that can settle into the spinal cord of cats and cause clinical signs of disease, as is rabies. In addition, the toxoplasmosis and cryptococcosis organisms can attack the spinal cord as well as the brain and eyes, creating a myriad of nervous symptoms.
Diagnosis of the source of the paralysis can be made using clinical signs, physical examination findings, blood profiles (if infectious disease is suspected), laboratory analysis of the cerebrospinal fluid (CSF), and radiographs of the vertebral column. To pinpoint the exact sites of spinal cord involvement, special radiographs called myelograms, which entail the injection of a special dye into the spinal canal, may be employed as well.
Treatment of paralysis depends on the cause. Anti-inflammatory agents combined with drugs designed to draw fluid out of the central nervous system can help reverse signs of paralysis, yet their usefulness is dependent on the extent of the nervous injury and how quickly therapy is instituted. In some instances, surgery may be required to repair a vertebral fracture, excise an offending tumor, or remove a diseased intervertebral disk.
Cats that have sensory paralysis in a limb might require limb amputation to prevent self-mutilation to the leg. In instances where an irreversible paralysis involves more than one limb, or involves the malfunction of internal organs, pet owners must seriously consider not only their cat's quality of life as a paralytic but their own as well, before prolonged therapeutic or rehabilitative measures are undertaken.
Owners who have a cat that suffers from seizures know first-hand how frightening these episodes can be. A seizure is defined as uncontrollable behavior or muscle activity caused by an abnormal increase in the brain's nervous activities. Epilepsy is the term used to describe recurring seizures.
What causes seizures in cats? The following are some potential sources:
Extracranial Causes
Metabolic severe hypoglycemia, polycythemia, and advanced hepatic encephalopathy
Toxicity-- many intoxications in advanced stages of disease
Intracranial Causes
Functional (idiopathic and genetic) epilepsy --poorly documented in cats
Structural brain diseases--by far the most common in cats. The structural abnormality may be an active or inactive lesion leading to secondary epilepsy:
Active--meningoencephalitis of unknown but suspected viral or perhaps immune-mediated origin, feline ischemic encephalopathy, and brain tumors (e.g., meningioma) are the most common causes. Infectious encephalitides (e.g., FIP, toxoplasmosis, bacterial and fungal infection, and cuterebral myiasis) are much less common.
Inactive-- postencephalitic lesion, postinfarction (feline ischemic encephalopathy), and postanoxia or ischemia (e.g., birth related), and post-traumatic epilepsy.
Because the causes are so numerous, a thorough examination and blood workup by a veterinarian is warranted whenever a cat exhibits seizures. In some cases, managing or eliminating an underlying cause will eliminate the seizures. In others, such as with idiopathic epilepsy, there is no known cause, yet by ruling out the other potential causes and establishing a pattern of occurrence, one can effectively manage most cases with anticonvulsant medications.
With idiopathic epilepsy, seizures can begin at any stage in life but usually begin around
1 to 3 years of age. As mentioned before, the cause of idiopathic epilepsy is unknown; however, if it occurs in young animals, it was probably inherited. In contrast, if it occurs in older cats, some traumatic cause, such as a stroke, should be considered.Most seizures themselves are rarely life-threatening, unless some physical harm comes to the cat as a result of the fit. The typical seizure or epileptic fit has three stages, or phases. The first of these, the preictal phase, is marked by anxiety and restlessness on the part of the pet. The actual period of the seizure activity, ictus, follows next. Its duration might range from a few seconds to several minutes. Certainly the longer the seizure lasts, the more dangerous it is to the health of the pet. The postictal phase following the seizure is characterized by an overall depression or confusion. Postictal cats can appear to be blind, running into walls and objects, or they might only sleep a lot. This phase can last for a few hours or for days, with the cat returning to its normal state after conclusion of the phase.
There is one seizure presentation called status epilepticus that can prove fatal. It is characterized by a cluster of seizure events occurring in quick succession. Unless appropriate emergency medication is administered intravenously to stop the seizures, these cats can lapse into a coma and die. As a result, prompt recognition and action on the part of the pet owner is essential.For cases other than idiopathic epilepsy, treatment is geared toward correcting or managing the underlying problem, such as kidney failure, poisoning, or low blood sugar. In instances in which idiopathic epilepsy is suspect, anticonvulsant medications can be used to control or even eliminate the seizure activity.
Cats suffering from idiopathic epilepsy do not necessarily need to be on any medication unless the seizures last for more than 2 minutes at a time or occur more often than every 2 months. Determining the exact dosages of any of these medications for a pet might require frequent adjustments at the start in order to accommodate its individual needs. Pets taking anticonvulsant medication should undergo liver function tests at least annually, since some of these drugs can adversely affect the liver over the long term. TREATMENT Prompt and aggressive anticonvulsant therapy if the cat has (1) more than 1 single seizure every 6 to 8 weeks, (2) cluster seizures (> 1 seizure/24 hours), or (3) status epilepticus, whether convulsive or nonconvulsive. The goal of treatment is < 1 single seizure every 6-8 weeks. Cats having severe cluster seizures or status epilepticus should be hospitalized until control is achieved. Since seizures in cats are usually the result of a structural disease, the owner should be encouraged to permit a diagnostic work-up so a specific treatment can be applied if needed. In cats with active structural disease, the antiepileptic medication is only a symptomatic treatment.The vestibular system is a specialized portion of the nervous system found within the inner ear, brain, and spinal cord. Its duty is to maintain a state of equilibrium and balance. By communicating with the nerves supplying the eyes, limbs, and trunk, the body is able to coordinate the position and activity of these regions with movements of the head.
Peripheral vestibular dysfunction (PVD) is a disease that affects the nerves of the vestibular apparatus in the ears of cats. PVD is characterized by a sudden onset of incoordination and loss of balance, which is often accompanied by a head tilt, involuntary twitching of the eyeballs, and, in many cases, vomiting. The causes of this disorder can include trauma to the ears, skull infections, and tumors involving the middle or inner ear. Diagnosis of PVD is achieved using clinical signs and various laboratory tests to rule out other potential causes of the symptoms. Radiographs of the skull may be helpful in the detection of any masses or infections that may involve the inner portions of the ears. Treatment, of course, depends on the underlying cause and usually includes high doses of corticosteroid medications designed to reduce inflammation involving the vestibular apparatus.Vestibular ataxia syndrome is seen in kittens born of queens stricken with feline parvovirus during pregnancy. Owners often are alerted to a problem when these kittens seem to have trouble in attempting to walk. The condition will not improve as these kittens mature, nor will it usually worsen.
Congenital vestibular syndrome is seen in Siamese and Burmese cats, with signs appearing anywhere from 2 to
4 weeks of age. Many of the Siamese cats affected are deaf as well.The prognosis for Siamese cats with congenital vestibular syndrome
is good, with clinical signs usually abating by the, time the cat is 6 months of age. In Burmese cats, however, the prognosis is not as good, and the poor quality of life for most of these individuals will usually warrant euthanasia.
Feline
hyperesthesia syndrome ("twitchy skin syndrome") is a condition characterized by some unique clinical signs. Affected cats exhibit a rippling of the skin on their backs, especially when petted in the lower back region. They might chew or lick at their tail incessantly, and appear to be "spaced out," spontaneously darting throughout a room or house and attacking objects and owners without provocation.The exact cause of this condition remains unknown. Some researchers feel that it is a form of epilepsy. Because "emotional" breeds such as Siamese, Persians, and Himalayans seem most often affected, other researchers believe that it is actually a behavioral disorder brought about by an upsetting experience or circumstance. Even food preservatives used in cat foods have been accused of causing feline hyperesthesia syndrome.
Medical therapy for this disorder consists of the use of antianxiety medications or sedatives in an attempt to modify the cat's behavior. Identifying and correcting any environmental upsets (including any dietary changes) that might have a possible link to the problem are needed as well.
Feline Ischemic Encephalopathy
Feline ischemic encephalopathy (FIE) is a neurological condition that has been known to strike cats. FIE is caused by a sudden disruption of blood supply to the brain, similar to a stroke in humans. Although a definitive cause has yet to be determined, cardiomyopathy, neoplasia metastasis, and even feline heartworms are suspect. Affected cats exhibit marked depression, incoordination, circling behavior, and/or seizure activity. The pupils of the eyes may become dilated, and blindness may be apparent. Acute clinical signs usually resolve within 7 to 10 days; however, residual neurologic deficits of varying degrees often remain indefinitely.
Diagnosis of feline ischemic encephalopathy is based on history and clinical signs seen, as well as ruling out other causes of similar symptoms, such as vestibular disease, feline leukemia, and poisonings. Treatment of this neurologic disorder involves the administration of high doses of anti-inflammatory medications. In addition, medications designed to dilate the brain's blood vessels and thin the blood may be employed in an effort to improve overall circulation to the affected regions of the brain.
The prognosis for survival in cats with FIE is guarded during the first 48 hours following onset of clinical signs. After 48 hours, the prognosis for survival is good, since FIE is a nonprogressive disorder.