HAMILTON & DISTRICT BUDGERIGAR SOCIETY INC.

THE NERVOUS SYSTEM

A distinction must be drawn between diseases specifically affecting the nervous system, and those which affect the whole metabolism, and produce nervous signs.

Many paralysis problems can be caused by birds flying into walls, windows or falling off furniture or its cage to the floor when wings are clipped too severely. This can cause brain, spinal and/or nerve damage or blood clots which can cause instant paralysis or slowly paralyse the bird. Read the guide for wing clipping before you attempt it to prevent the bird injuring itself.

Clinical Signs:
Nervous signs indicating involvement of the functions of the nerve tissue, are extremely common in cage and aviary birds. At times they are so spectacular as to obscure the real reason for their appearance; the important lesions may often be in organs remote from the main centres of the nerves. Signs of nerve involvement can be divided into three main groups; those where normal function is lost or impaired, e.g., paralysis, blindness; those where activity is increased, such as excitement and twitching; and those where function is obviously deranged or abnormal, such as convulsions, throwing back the head, and asymmetrical leg or wing movements. The paradox of such a grouping is that all three types can be outward manifestations of the same disorder. The causes of nervous clinical signs can be listed as follows:

1. Pressure on the brain, spinal cord or a nerve-for example, by a tumor, inflamed tissue, blood clot or depressed fracture.
2. Inflammation or destruction of a portion of nerve tissue resulting from injury, infection or poison.
3. Tile loss of full nerve function involving brain and/or spinal cord and nerves. This can result from circulatory or respiratory disorders resulting in a lack of the oxygen vital to the health of nerve tissue, or from infectious diseases which cause a high body temperature or pyrexia and thus interfere with brain metabolism.
4. Abnormal development or functioning of nerve tissue due to a deficiency of vitamins or other nutriments.
5. Pain which causes reluctance to use a part of the body such as a limb or the neck, and is manifested as a type of paralysis.
6. Scarring or fibrosis and contraction around nerve tissue, resulting in the stretching or strangulating of a nerve.
7. Immobilization of a joint by fibrous tissue or bone proliferation, leading to degeneration of muscle then nerves, and finally nerve atrophy.
8. Abnormal levels of calcium or magnesium due to disorders of the parathyroid glands producing twitchings, or coma and death.

Other endocrine disorders may also be involved, but are mostly unproven: thyroid deficiencies and excess have been shown to cause changes in nervous, as well as chemical activity. Nervous signs can be divided into generalized and local; this is a practical approach, but by no means always a reliable distinction. When a leg is partially or completely paralyzed the cause generally lies somewhere between the spinal cord and the affected part. Convulsions and incoordination however, are generalized signs and suggest brain involvement, although paralysis may also be produced by quite a small lesion in the brain or brain stem.

Paralysis of The Legs And Feet:
This type of paralysis includes that of the toes and foot; "sliptoe"; clenched feet; "cage paralysis" and flaccid and spastic paralysis or paresis of the whole or part of a leg. A painstaking examination is necessary, not only of the limb but also of the entire bird, before the causes of most of these clinical signs can be elucidated. On many occasions the cause cannot be found during life, and even a detailed necropsy using laboratory aids seldom provides the reason for the symptoms. Nevertheless these disorders are extremely common in cage birds. Firstly, such external factors as cold, draughty or wet quarters, predisposing chills or inflammation of nerves, muscles or joints (neuritis, myositis or arthritis) must be ruled out. A viral infection, such as Newcastle disease or Marek's disease, or a dietary imbalance may sometimes be implicated. It must be realized that quite often a diet which contains the bare minimum of vitamins or amino acids, just adequate for the growth of young stock, can be made deficient in vitamins by adding a high protein food supplement. Conversely, adding high-energy foods such as oil-rich seeds, can adversely affect the enzyme systems of the body and increase the deficit of amino acids and vitamins in the diet. Some of these induced deficiencies may be recognizable in chicks and growing stock; but they are also believed to occur in adults, although little critical experimental work has been carried out on mature birds. Deficiencies are most likely to appear in growing chicks, breeding females and ailing or aging birds.

Specific lesions involving the spinal cord or nerves to the legs are difficult to pinpoint unless they are very large, and therefore they can usually only be suspected on circumstantial evidence. They include tumors of these structures (rare even in budgerigars); bony protuberances of the vertebrae which pinch the spinal cord, sciatic or other large nerves as they emerge from the spaces between the vertebrae; Marek's disease; injury; local infections and other inflammations of the nerve trunks or spinal cord.

In addition, there are conditions which appear at first sight to be paralysis of some kind, when in fact the lameness is due to interference with the functioning of bones, muscles, joints, ligaments or tendons. In this category can be included fractures, bony or other growths involving the muscles or the tendons passing over bones or joints, arthritis, sprains, perosis, cut or torn tendons or muscles, scar contractions, "bumble foot" and severe "scaly leg". In order to try and diagnose these disorders it is necessary to examine the posture, general health and mode of walking and flying. The hand should also be passed gently over the entire bird, particularly the loins and hip region. In the case of so-called "cage paralysis", "clubbed foot" and "sliptoe", which are sometimes different degrees of the same processes, nothing may be found by such examinations. The next step is to supply a vitamin supplement, either as an elixir or preferably by injection. It should contain riboflavin, nicotinic acid, thiamin, biotin, choline, vitamin B12, vitamin E and the amino acids, lysine, cysteine and methionine. If the cause of the paralysis is a dietary deficiency or imbalance, the bird will generally recover in from one to three weeks or sometimes in a few days after such treatment.

If in spite of combined medical treatment and supporting dressings the use of the limb does not return, it is likely that the paralysis has not only worsened, but that there is a spinal swelling or other deformity present, such as a tumor or bony masses (exostoses), causing pressure. With disuse, muscles will atrophy and they may even be partly replaced by scar tissue, so that the tendons will contract causing the limb to hang in a flexed position. A useful indication of true nerve involvement is when only one group of muscles, such as the flexors or the extensors of the knee, hock or toe joints is affected. Usually the muscles supplied by the damaged nerves are soft and flaccid, but sometimes they are tense, contracted fully or spastic. In complete, flaccid paralysis the leg will stay more or less in whatever position it is placed. In the spastic type, on bending or flexing the joint or limb and releasing it, the leg springs back to the straight or extended position. With a knowledge of anatomy of the nervous system, it is possible to determine which bundles of spinal nerves are involved and sometimes pinpoint the trouble. Unfortunately however, this does not indicate the type of treatment required, although it does tend to limit the cause to a local lesion rather than a dietary deficiency or other generalized disorder. Paralysis of both legs is serious, since birds are unable to take off without the use of their legs. However, unless the condition also involves the wings, a bird with paralyzed legs can fly quite strongly once launched.

Paralysis Of The Wing:
The procedure for diagnosing the causes of paralysis of the wings is similar to that for the legs, but wing paralysis is much less common. Frequently one wing tip or wrist joint is seen to be held higher than the other, and the wing tips are often crossed. When the bird is held by its legs in an upright position and lowered sharply, the weaker wing spreads less fully and may beat at a slower rate than the normal wing. This may be due to nervous incoordination or ataxia of the wing, but it may also be because of muscle injury, pain, fracture, sprain or dislocation of the shoulder or elbow joints, bone tumors or arthritis. Paralysis or weakness of both wings, strongly denotes a spinal or hind-brain lesion, or occasionally viral infections such as New-castle and Marek's diseases. Damage to one side only of the brain or spinal cord, will produce effects in only one wing. Most unilateral wing disabilities are due to lesions of the wing, and in budgerigars the various types of tumor associated with the elbow region come high on the list. In most other species, bone and joint injuries are the commonest causes.

In true paralysis involving some nerve tissue damage, medical treatment is generally useless. Provided the limb is rested, injuries will often heal without treatment. Tumors involving the brain or spinal cord are untreatable. When the brain lesion is a hemorrhage from cranial damage, or a disorder of the cardiovascular system, some arrest of the process may be possible through changes in diet, exercise or management. Usually, however, it is only a matter of time before the trouble is seen to be incurable and sudden death may follow at any time after the onset of signs. If breeding stock is involved, it is probably best to destroy affected birds unless the cause is dietary.

Paralysis Of The Neck:
Some signs of this are when the bird is constantly looking up or down or its neck is twisted sideways or even upside down. This is relatively uncommon in birds but does happen. The so-called "limber-neck" of some birds and waterfowl due to botulism, and the type of neck paralysis seen in turkeys due to deficiency of folic acid are rarely if ever met with in cage and aviary birds. Most cases are due to severe injury to the head or neck; concussion or hind-brain damage, general weakness or brain tumors. When brain tumors are present, however, twisting or torticollis "star-gazing" or other grotesque attitudes are more common than a lowering of the head. Generally treatment is useless. This can also be a result of a seizure or stroke where it has lost use of those muscles to straighten up properly.

Tremors, Shivering And Twitching:
These signs may indicate a highly nervous temperament, chilling, low blood magnesium as the result of parathyroid disease, other metabolic disorders or deficiencies in the diet. They may also occur in the early stages of infectious diseases; as the result of heat stroke, certain poisonings, particularly by insecticides containing phosphorus; carbolic acid poisoning, overdoses of some drugs an8 also when there is loss of body fluids caused by hemorrhage, exudations, diarrhea or vomiting. In order to ascertain the possible cause of these signs it is necessary to investigate all aspects of management, especially in relation to other birds kept on the same diet or with the sufferer. When there is a flock problem which has arisen over a short period, poisoning or dietary deficiencies such as calcium and/or magnesium, should be suspected. Slow rhythmic twitches of a part of the body, such as a wing are rare, but occasionally met with in parrots and budgerigars. The cause is unknown and treatment usually ineffective, although vitamin supplements and sedatives will sometimes produce some relief from the violent twitchings.

Fits, Convulsions And Epilepsy:
Convulsions of various types are quite common in cage birds and are sometimes a prelude to death. Birds may have short-lived but recurrent attacks, which subside after a week or two but recur months later. Some birds completely recover either with or without treatment. Usually, however, the convulsions become progressively more severe or frequent and the bird eventually dies. Epilepsy, or epilepsy-like convulsions are named after the well known but still incompletely understood disease of human beings. In cage birds only some of the characteristics of epilepsy occur. The bird may be sitting quietly on its perch when it suddenly cocks its head as if looking or listening for something: the eyes remain open and the muscles become rigid. This is followed by rapid vibration of the wings, these being raised a little from the body. In some cases the feathers are erected, the whole body becomes involved in the violent movements, the legs stretch out and the bird thrown off its perch, to lie unconscious and still convulsing. After several seconds the vibrations lessen, the wings slowly return to the closed position, the bird moves its head, and then struggles with difficulty to its feet. It usually sits on its breast some-what dazed for a matter of hours before returning to its former activity and alertness. Additional signs which are sometimes seen, include throwing back of the head (so-called "star-gazing"), deviation of the tail sharply upward or to one side, a croaking sound as if the thoracic muscles are forcing air out of the partially closed throat and temporary paralysis. Involuntary excretion of faeces or urine is uncommon; the salivation which occurs in man is unknown in avian "epilepsy".

Fits or convulsions of this kind can be caused in several ways. In young stock, deficiencies of riboflavin, thiamin, nicotinic acid, other vitamins and amino acids may be responsible. In older birds, hormonal imbalances may be at least contributory causes, or more rarely, tumors or other lesions of the pituitary gland. When birds of all ages and especially several species are affected, toxic seed dressings such as organophosphorus pesticide poisoning should be suspected. If a more limited number of birds appear sick and die after a series of convulsions, then an acute bacterial infection may be suspected. Toxemia from massive liver or kidney destruction--whether by infectious, metabolic or poisonous agents--is also a relatively frequent cause of convulsions prior to death. In the isolated bird, fed on a reasonably satisfactory diet, changes in the circulation, or more probably brain disorders resulting from an inefficient blood supply to the brain, are more likely causes. Inactive, middle-aged and obese birds, especially if pampered and fed on unnatural tit-bits, are most prone to convulsions. Even moderate exertion, such as a panicky flight around the cage brought about by the presence of a cat or strangers, may be sufficient to start a series of fits. Sometimes, however, they start spontaneously or when the bird is handled and can be immediately fatal. The cause may be oxygen starvation to the brain or even rupture of its blood vessels due to a sudden increase of blood pressure.

Convulsions may result from poor nutrition, poor oxygenation or local pressure on nerve cells. It is probable that, in addition to a weakened heart or blood vessel walls due to fatty infiltration, the adrenal cortical tissues of affected birds are incapable of adequate hormone production. Convulsions and other evidence of brain or nerve damage may sometimes be due to concussion. Flying into an object, or even tight wire netting, can cause severe hemorrhage inside the cranium and produce nervous signs, often only a short while before death.

In all cases, a full clinical examination is necessary before the cause of any type of fit can be found and treated. It is essential to provide affected birds with complete quiet, a dim light and a concentrated, balanced and easily digested diet. An adequate supply of fruit, green stuffs, yeast, egg, liver, and wheat germ is advisable, with meat or gentles in some cases. Perches should be placed across the floor of the cage. The temperature should be kept constant between 60 and 70F (15 and 21C). If recurrences of the fits are expected a mild sedative such as metoserpate hydrochloride or metomidate hydrochloride, an anticonvulsant drug or a tranquilizer, such as acetyl promazine or chlorpromazine, may be used under the supervision of a veterinarian. When an infectious disease or other organic disease is suspected antibiotic or other treatment may be necessary. In most cases, except those of dietary origin or as the result of a minor injury, the prognosis is poor.

Fainting And Vertigo:
Loss of consciousness without convulsions, is not infrequent. It may follow staggering or other types of incoordination, such as circling or rolling. It probably arises from causes similar to those which produce the epileptic type of convulsions. Vascular or cardiac diseases causing anemia or anoxia of the brain cells are among the reasons. Overdosing with certain drugs and affections of the balancing mechanism in the middle ear are occasionally responsible, hence the name "labyrinthine vertigo". Signs of dizziness or fainting should always be considered potentially dangerous. Although hereditary tendency to these conditions has been noted in canaries and some other birds, this has not yet been fully studied and the composition of the diet and general health should always be checked first.

Hysteria And Excessive nervousness:
Some individuals as well as certain species are notorious for their excessive excitability in response even to quite normal sounds or visual stimuli. Hyperexcitability is liable to be hereditary in nature, although a placid bird can be rendered excitable by subjecting it to irregular hours of artificial light, incorrect handling or frightening situations. Hyperexcitability is often associated with gasping and panting respiration's and many birds affected in this way are incurable. Others slowly recover after a period of repeated sedation or tranquilization. Hysteria is essentially a functional disorder and post-mortem examinations often fail to reveal the cause.

EMAIL

E-Mail: berniehansen@sympatico.ca

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Hamilton & District Budgerigar Society Inc.