STRINGHALT AND PARAPLEGIA Stringhalt.The term"stringhalt"is ap plied to involuntary movements of the hind limbs of the horse during progression, by which the hocks are suddenly flexed with a more or less violent jerk and may also be extended or brought to the ground with more than usual force.
The spasmodic contraction is usually more marked in the case of the flexor muscles of the hock than in that of the extensors, but occasion ally the opposite condition exists and the horse"hammers ' the ground with his hind feet. This action may be so pronounced that con siderable difficulty may be experienced in keep ing the animal shod. One or both limbs may be affected, more commonly both. Stringhalt or an analogous condition is occasionally though rarely observed in the fore limbs. All classes of horse may be affected.
The etiology of stringhalt is still very obscure. At one time or another the seat of the disorder has been traced to practically every part of the horse's limb, but none of the theories pro pounded is very satisfactory. Possibly a number of factors contribute, or the cause may not be the same in every case. Some of the commonest causes enumerated by various observers are, briefly: spavin, contraction of fascia of thigh, of the peroneus, of the fascia below the hock, of the tensor vaginae femoris, of the inner lateral ligament of the patella, chronic arthritis of the hip-joint, of the true hock-joint, foot trouble of various kinds, asym metry of the skull, brain disease, brain tumours, changes in the spinal cord, hyperaemia of the sciatic nerve, changes in the extensor pedis tendon, exposure to cold; and numerous other causes (?). The mere fact that so many varying theories exist is sufficient proof that the actual cause of stringhalt is unknown. All that we can assert with confidence is that it is a nervous disorder; probably in some cases it is due to reflex contraction of groups of muscles stimu lated by irritation of peripheral nerves, and possibly in others it arises, as Dollar suggests, from localized sclerosis of the spinal cord, in a similar manner to chorea.
The symptoms may appear suddenly at any age, particularly at from four to five years, especially when the horse has been rested or laid up in the stable for any length of time from any cause.
As a general rule, however, when stringhalt develops, very slight symptoms appear during the first few years of life, more especially when the animal is first put to work. The affection may then be only exhibited at intervals and may after some time disappear. As a rule, the symptoms become aggravated until they arrive at a certain stage of severity, when they become stationary and may show no inclina tion to become worse even with work and advancing age.
In very slight cases of stringhalt the horse exhibits nothing abnormal whilst at rest in the stable and during a journey. The symptoms may be best observed after the animal has been resting all night or has been standing for some time in one place. Upon moving off, more especially if flicked with the whip, the hocks will be jerked upwards with a peculiar"dan cing"motion quite distinct from the ordinary rapid movements of a sound animal. The symptoms are exaggerated when the horse is backed or turned in short circles.
In slightly pronounced cases the jerking movements of the hocks may be quite distinct during the first half-dozen steps, after which they wear off and may not appear again until after the horse has been brought to a stand still and again moved on. Occasionally the hocks may be jerked up during a few steps every now and then, at other times the gait may be normal. In severe cases flexion of the hocks may be so marked that the front of the hind foot strikes the belly at each step, and upon being again brought to the ground the foot is placed down with a heavy"stamping"action. Nevertheless the animal's usefulness is seldom seriously interfered with excepting in a riding-horse, and apart from the fact that the action is unsightly the horse may pull well in harness and be nearly equal in strength to a sound animal.
Treatment. — Without a proper understand ing of the etiology treatment must be empirical and is usually futile. We have had one success ful result after peroneal tenotomy in a five-year old hunter with very pronounced stringhalt. Recovery was practically complete three months afterwards, and the horse was hunted for several seasons. Whether the good result was due to the operation is, of course, by no means certain.
Peroneal tenotomy is most conveniently per formed with the patient recumbent and under anaesthesia. The limb need not be unhobbled. After preparing the skin at the seat of operation an incision is made at the point indicated in Fig. 165. A grooved director is inserted under the tendon, which is then divided by a probe pointed bistoury passed along the groove. The wound is then closed by one or two sutures and covered by an adhesive protective.
Some operators advise cutting also the fascia which unites this tendon to the extensor pedis tendon. This operation certainly does no harm, and may therefore be tried as a remedy, but other operations advised by some practitioners, such as section of the tensor vaginae femoris, the internal lateral ligament of the patella, and various neurectomies, should be avoided, as they are liable to do more harm than good, and as they have provided consistent failures in the past they may be discarded with wisdom.
Partial Paraplegia in Horses. Partial or in complete paralysis of the hind limbs is not un commonly met with. It may appear quite suddenly or its onset may be gradual. For the purpose of description it is usual to recognize two types of paraplegia, differing in their etiology. (i.) True spinal paralysis, dependent upon lesions existing in the cord or its mem branes. (ii.) False or spurious paralysis, dependent upon causes not associated with disorders of the spinal cord.
Etiology. to the difficulty of making a complete and minute examination of the whole length of the spinal cord in large animals, very few observations have been recorded regarding the actual lesions of spinal paralysis in the horse.
Fractures of the vertebrae usually result in complete paralysis, but fissures sometimes occur, with pressure upon the cord as the result of callus formation within the canal.
Concussion of the spinal cord is a very frequent cause of partial paraplegia. It may occur as the result of falls, particularly upon the hind quarters, as may happen when the hind feet slip beneath the body whilst rearing, or as a sequel to falls from high places, as banks. Galloping into immovable obstacles is also frequently followed by symptoms of spinal concussion. Sudden pulling-up after a gallop may act similarly, particularly when horses are grazed in hilly fields.
Haemorrhage into the spinal canal may be produced by blows or by the same means that operate in producing concussion.
Lightning stroke or other powerful electric shocks may produce either partial or total paralysis according to the severity of the dis charge.
Metastatic abscess formation may occur in the spinal cord as a sequel to strangles infection, whilst pyogenic infection is sometimes seen as a complication of poll-evil and fistulous withers.
Apart from new growths which may form in the bones (osteo-sarcoma) or in the cord, idiopathic inflammation of the cord and its membranes is probably more common than is generally supposed. Cases have been recorded by many experienced observers. Softening and swelling of the lumbar portion of the cord and pachymeningitis are said to be common lesions.
Certain toxins produced as the result of fermentative changes occurring in the stomach or intestines, from the ingestion of certain food stuffs (irritant husks, undecorticated cotton cake, excess of barley, maize, or wheat, etc.),
are liable to produce partial paralysis. Grass at certain stages of growth, notably when flower ing, has been blamed for producing certain symptoms with which paraplegia is frequently included. Horses working in hay-fields and allowed to partake of the freshly cut grass do indeed sometimes exhibit similar symptoms. Spurious paraplegia may also arise from very varying causes. In old horses union of several lumbar vertebrae (anchylosis) may produce an uncertain gait, particularly noticeable when backing a load, whilst similar symptoms, though usually more pronounced, occur after partial luxation of the sacrum or stretching of the sacroiliac and occasionally the ilio-sacral liga ments. The latter condition is more often seen after difficult parturition, though in these cir cumstances paraplegia may result from injury to the pubic symphysis, or to the obturator or other nerve in the pelvic region.
Phlebitis occurring in the utero-ovarian veins may arise from infection and may lead to embolism in the external and internal iliac veins with resulting paralysis. This is more common in cattle.
Strongyles sometimes produce symptoms of partial or complete paraplegia, more especially in young colts and fillies affected with aneurism of the aorta.
Strain and succeeding atrophy of the psoas muscles may at times be responsible, though it is probable that this condition is not so fre quently met with as was at one time supposed. Muscular rheumatism is more often the cause of a spurious type of paralysis and may be in duced by extreme cold. We have observed marked symptoms of paraplegia in an aged cob left tied to a stake throughout a whole night during which several degrees of frost were registered. The symptoms subsided gradually and within a week had entirely disappeared.
Hwmoglobinuria also produces crural paralysis, which may be bilateral, and may persist for a number of months. Fractures of the pelvis, particularly of the inner angle of the ilium and those cases in which the pelvis has been crushed in a lateral direction, may produce symptoms often simulating paralysis.
Exposure to a very hot sun has produced cases of temporary paraplegia, and in our experience is particularly liable to do so in mares during cestrum. Iliac thrombosis may produce intermittent paralysis which is only exhibited after the animal has travelled a vary ing distance. The symptoms may occur in one or both limbs.
Symptoms. — Naturally , with such a wide etiology, considerable variation must exist in the severity and nature of the symptoms exhibited. Chronic cases of partial paraplegia associated with lesions in the spinal canal may remain more or less workable for the whole of their lives, but in cases which develop suddenly there is usually a tendency to become worse and to terminate in complete paralysis. This is particularly true when the condition occurs in mares heavy with foal.
Chronic cases may show no symptoms whilst at rest in the stable, neither may anything abnormal be detected whilst the horse is walked in a straight line, but upon turning or backing lack of co-ordination becomes evident and the animal rolls behind, and when badly affected crosses his hind legs. Well-marked cases show rolling movements whilst being led in a straight line, and frequently the foot is carried forwards farther than is usual and is set down with an uncertain movement.
Very slightly affected horses may even carry a man and gallop apparently sound until required to turn, when a sinking of the quarters results and the animal may come to the ground behind, recover himself, and go on again. The apparent cause of the symptoms in spinal cases is inaccurate"timing"of the various groups of muscles which do not act in harmonious combination.
Little disturbance of sensation can usually be detected; occasionally hypersthesia is present. Muscular atrophy is seldom seen in partial paraplegia.
Spurious paralysis may exhibit a variety of symptoms, according to the actual cause. Strain of the sacro-iliac ligaments more nearly resembles true paralysis, but frequently crepitation can be felt or heard, especially when the animal is pushed from side to side by pressure upon the angle of the haunch. Fractures of the pelvis can usually be detected by rectal examination, as can psoas strain in the majority of instances.
Treatment. This must depend upon the excit ing cause.
Paralysis arising from concussion of the cord often recovers spontaneously after an interval ranging from a few days to months.
Severe cases require slinging; mild cases are better at pasture in summer in a level field or during winter in a large box, with short bedding which will not catch the feet. Spinal paralysis seldom yields to treatment. Externally we may apply blisters with the idea of reducing con gestion; a freshly flayed sheep-skin tied over the loins was formerly much employed, with little benefit, for the same purpose, and it has the disadvantage that it is liable to breed maggots and cause considerable trouble. In ternally salicylate of soda, iodide of potash, and nux vomica may be employed. Iodide of iron combined with strychnine may also be found useful, whilst in many cases we have had satis factory results from the employment of small doses of liq. fern perchlor. combined with liq. strychninw and liq. arsenicalis. Possibly apparent success is frequently attributable to incorrect diagnosis.
For chronic partial paralysis Macqueen recom mends strychnine in gradually increasing dosage. He commences by giving twice daily a ball containing one grain of strychnine and continues until twelve balls have been given. He then gives twelve more balls, each containing two grains, then twelve of three grains, and so on until twelve of five grains have been given. He then recommences with a dose of two grains and continues as before.
This treatment is continued until the horse exhibits superficial twitchings or other early symptoms of strychnine poisoning. Usually whilst feeding the horse is seized quite suddenly with a convulsion; it rears, falls, and struggles round the box lying on its side, moving the limbs as in galloping.
He then administers a drench, previously prepared and kept in readiness, composed of four ounces of roughly teased black Lurgan twist tobacco, infused with a quart of boiling water and strained. The draught is ad ministered without difficulty during the intervals which gradually lengthen between the seizures. There is no danger to the attendant so long as he remains behind the horse's neck. In a few minutes the symptoms abate, and usually with in twenty minutes the horse is again up and feeding as if nothing unusual had happened. This treatment, including the antidote, may have to be repeated several times in order to effect a cure.
Infusion of tobacco appears to be a satis factory antidote to strychnine poisoning, and is the only one which can be relied upon to over come the symptoms.
Spurious paralysis must be treated according to the cause. Sometimes treatment is im possible and frequently useless; at other times rest and nature will often, as far as may be possible, effect recovery. R. H. S.