Sciatic nerve

“ To give you an idea of what real things nerve-trunks are, this sciatic nerve is as large as a small clothes-line, or, more accurately, as a carpenter's lead pencil, and so strong that when the surgeon cuts down upon it and stretches it to cure a very bad case of sciatica, he can lift the lower half of the body clear of the table by it. This strength, of course, is not due to the nerve-fibres and cells themselves but to the tough, fibrous sheath, or covering, with which all the nerves that run outside of the brain and spinal cord are covered and coated. ”

“ Here, again, we are confronted with the fact that the peroneal element of the great sciatic nerve is the more prone to idiopathic inflammations or toxic influences, and hence we can only assume it to possess a special vulnerability. ”

“ When the sciatic nerve has been cut or torn away, the greater portion of the leg is paralyzed as to motion and sensation, which is natural enough, because the muscles can no longer obey the mandates of the will, being deprived of the nerves which carry them, and also the centres no longer receive impressions which formerly came from those muscles and the skin covering them, because the nerves which carry the impressions have been destroyed. ”

“ Symptomatology.—When consideration is given the number of muscles that are supplied by the sciatic nerve and the function of these muscular structures, it is obvious that the leg cannot be used in sciatic paralysis. However, the limb is capable of sustaining weight when it is fixed in position, but this is done without exertion of muscular fibers which are supplied by the great sciatic nerve. Trotting is impossible and flexion of the affected member is also likewise precluded. The foot is dragged when the subject is caused to advance. ”

“ As you will see by the picture, the spinal nerves, which are given off from the cord in the lower part of the neck and between the shoulder blades, are gathered together into a great loose bundle to form the long nerve-wires needed to supply the shoulders and arms. Those given off from the small of the back just above the hips also run together to form, first a network and then a big single nerve-cord, called the sciatic nerve, which many of you have probably heard of from the frightfully painful disease due to an inflammation of it, called sciatica. ”

“ It affects the great sciatic nerve which emerges from the pelvis and runs down the leg to the foot. It is in most instances traceable to exposure to cold or damp, to overuse of the limbs in walking, &c. Any source of pressure upon the nerve within the pelvis, such as may be produced by a tumour or even by constipation of the bowels, may excite an attack of sciatica. It is often connected with a rheumatic or gouty constitution. In general the nerve of one side only is affected. ”

“ Great sciatic nerve.—Wounded at Modder River. Entry, in left loin; exit, at lower margin of buttock. The wound was followed immediately by complete peroneal paralysis, both motor and sensory. Fourteen days later hyperæsthesia developed in the area of distribution of the internal popliteal nerve, the superficial pain being greatest in the sole; the muscles of the [Pg 366] calf were also very tender on manipulation. The pain increased, and at the end of twenty-four days the patient's sufferings were so great that Mr. Thornton cut down upon and exposed the nerve. ”

“ The true reason I believe to be, that what would have been a slight and trivial neuralgia elsewhere, becomes a serious affection in the instance of the sciatic nerve, by reason of the strong muscular pressure end dragging which are always going on in the thigh in locomotion. ”

“ This argument appears, to me, to do away all support, which the hypothesis may seem to derive from the experiment, before quoted, of applying the metals equally to 40 both sciatic nerves, after one of them had been divided; I may however remark, that the pain necessarily excited by arming a nerve, whose communication with the brain was not interrupted, would fully account for the more rapid exhaustion of the muscles, to which it belonged, compared with such as had not been acted upon by so strong an additional stimulus. ”

“ A hood of black cloth, carefully arranged so as to exclude light from the eyes without obstructing respiration, entirely prevented a dark frog from becoming pale in bright sunlight. I was naturally desirous of ascertaining through what efferent channels the nervous impulse that caused concentration of the pigment on exposure to light was conveyed from the brain to the foot. Division of the sciatic nerve had no effect whatever upon the colour of the limb. I then tried cutting through all the structures in the thigh except the bone, the femoral artery and vein and the sciatic nerve. ”

“ Eulenburg states that neuralgia caused by cold more frequently attacks the sciatic nerve than any other, and thinks that the tendency to sciatica is characteristic of the relations of rheumatism to sensory nerves. For my own part, I see no reason to call in the rheumatic diathesis as a deus ex machina to explain the frequency with which sciatica follows comparatively trifling peripheral impressions like that of cold. ”

“ The posterior half of the first vertebra was then removed and the spinal marrow laid bare, at the same time a considerable incision was made in the great glutæus muscle, in order to expose the sciatic nerve. A slight incision was made in the heel; no blood escaped from any part. A wire which communicated with one extremity of the battery was put in contact with the spinal marrow, whilst the other was applied to the sciatic nerve. All the muscles of the body were in an instant agitated with convulsive motions which resembled a violent shuddering. ”

“ The wounds giving rise to these were of the most diverse character; some crossed the buttock in a vertical, transverse, or oblique direction; others travelled through the thigh in corresponding directions, while a third series involved both buttock and thigh.
The size of the great sciatic nerve renders complete laceration by a bullet of small calibre a matter almost of impossibility; hence complete division may almost be left out of consideration in the case of this nerve. On the other hand, partial division, perforation, and severe contusion are each and all favoured by the same factor. ”

“ This nerve is frequently small or absent in the Platana.
[In the Frog, the seventh, eighth, and ninth nerves unite to form the sciatic plexus which gives rise to the large sciatic nerve extending along the thigh, and dividing above the knee into the tibial and peroneal nerves to the leg and the foot. The tenth nerve is present.]
2. The Sympathetic Nervous System.
This system consists of a cord on each side closely following the course of the systemic arches and the dorsal aorta. It has on it six ganglionic swellings, and there are connections between the ganglia and all the spinal nerves. ”

“ John Rogers to his friend and patient, Benis Hamilton Spence.
DEAR Idiot: I knew you would get it—and you got it. Perhaps after this you will learn to treat your sciatic nerve with proper respect. But there is a worse complaint than sciatica. It lasts longer. Certain symptoms of it are indicated in the things which your letter leaves unsaid. Beans, old thing, you alarm me.
Now here is a sporting offer. If you'll drop it and come home at once I'll promise never to tell Aunt Caroline. Come the moment you can put foot to the ground. ”

“ Another had made pathological studies, learning up the few conjectural symptoms of maladies that show no outward trace; as science advanced to the point of recording detectively the true state of the heart he had deftly changed ground, relinquished rheumatism of that organ and done some work of research into pains in the head; much faith did he put, too, in the sciatic nerve. When a couple of these savants slept in one tent they would argue after Lights Out—was sciatica safest, or shell-shock, or general debility? ”

“ It is a still more interesting fact—‘that the sciatic nerve in the congenitally toeless animal has inherited the power of passing through all the different morbid states which have occurred in one of its parents from the time of division till after its reunion with the peripheric end. ”

“ The fits become simple convulsions, then mere twitchings, and lastly the animal can no longer be distinguished from another healthy one but by the fact that it has only one toe at one of its hind-legs, when the operation has been performed on the sciatic nerve; and nothing whatever remains when the origin of the disease was a prick in the spinal cord. ”

“ Headaches or neuralgic pains, due to local irritations, as uterine disease, stricture, neurotic or nerve tumors, pressure of trusses, eye strain from weakened eye muscles, or lenses that need the help of proper spectacles, require for a permanent cure the removal of the cause. Sciatic neuralgia, one of the most common and painful forms of nerve irritation, is particularly amenable to treatment by the modern means of cure used in our practice at the Invalids' Hotel. ”

“ Fig. 6. Semidiagrammatic dorsolateral view of the sciatic nerve of Pedioecetes phasianellus jamesi 3R, showing the distribution of the branches. × 21⁄2. 1, M. gluteus profundus; 2, M. piriformis; 3, M. extensor iliotibialis lateralis; 4-7, M. extensor iliofibularis; 8, M. flexor cruris medialis; 9, cutaneous; 10, to pudendal plexus; 11, M. flexor cruris lateralis; 12, M. caudofemoralis pars caudifemoralis; 13-15, M. caudofemoralis pars iliofemoralis; 16,17, M. flexor ischiofemoralis; 18,19, M. femorocruralis (branch of tibial nerve) ”

“ By simply keeping a sciatic patient in the prone posture, shielded from cold and from pressure on the nerve, we have it in our power to remove nearly all peripheral sources of irritation; but in trigeminal neuralgia there are many influences, particularly psychical ones, which cannot be shut out, and which will continue to act with disastrous effect in many cases. ”

“ The nerve is sensitive to pressure, the most tender points being its emergence from the greater sciatic foramen, the hollow between the trochanter and the ischial tuberosity, and where the common peroneal nerve winds round the neck of the fibula. The muscles of the thigh are often wasted and are liable to twitch. ”

“ A careful examination will discover not only the great rigidity of the spine, and as it were fusion en masse of its joints, but in these persons the bony outgrowths may be felt. Occasionally the alteration in the vertebræ by compressing the cord or its membranes, or the spinal nerves and ganglia, may produce neuralgic pains in the cervical, dorsal, lumbar, or sciatic nerves, wasting of the muscles, more or less paralysis, and even vasomotor disturbances. ”

“ It is not only at their exit that the spinal nerves thus communicate. The different cords of which each nerve is formed have precisely the same arrangement, as may be easily seen in the great trunks, as in the median, the cubital, the radial and especially the sciatic. By separating the different cords of these nerves, we see that they are not only in apposition longitudinally, but that179 they send numerous filaments to each other. These communications do not resemble those of the arteries, in which there is always continuity between the communicating branches. ”

“ If, after having divided at the pelvis a frog recently killed, the sciatic nerves be freed from cellular membrane up to their origin from the spine, and all the parts below 99 this, except themselves, be cut away, the muscles on each side of the spine, for some little way up, may be brought into contraction by touching the nerves alone with the two metals in contact. This experiment has not always succeeded with me, and never unless the frog had been recently killed. So long as the hind legs remain undivided from the nerves, it never succeeded; the only contractions produced being in the legs. ”

“ It is therefore connected with the lower lumbar and sacrum and with the second lumbar. The latter connection seems oftenest involved in knee joint inflammations.
Foot: Fourth and fifth lumbar and sacral nerves through the great sciatic and its branches.
Sensor Areas of Lower Extremity: In general, any given cutaneous area receives sensor branches from the nerve which supplies the subjacent muscle area. For accurate diagnostic purposes a good chart of sensor distribution may be consulted. ”

“ It is another matter when we are asked to believe that the mere varying pressure of intestines, in different states of fullness, or plexuses of pelvic veins liable to temporary congestions, can so affect the sciatic nerves as to set up neuralgia. ”

“ Brown-Séquard found that when the spinal cord of a Guinea-pig is pricked, or a portion of it is destroyed, or one of the sciatic nerves—that is, one of the largest nerves of the hind-leg—is either sectioned or torn off from the spinal cord, the animal in the course of a few weeks develops the epileptic malady. ”

“ This completely tallies with my own experience, and appears to afford some support to a suspicion I have formed, that the chief exciting cause of sciatica is the pressure exercised on the nerve in locomotion, and that this cause exercises its maximum influence when the period of bodily degeneration commences. It is further remarkable that, in elderly persons [45] (whose habits of locomotion are of course more limited) , the proportion of fresh cases rapidly diminishes; and also that above the age of thirty the number of male patients greatly exceeds that of female patients attacked. ”

“ The second variety of sciatica occurs for the most part in middle-aged or old persons who have long been subject to excessive muscular exertion, or have been much exposed to damp and cold, or who have been subject to the combined influence of both these kinds of evil influence. One must also include, I think, in this group a considerable number of cases where the age is not so advanced, but the patient has been obliged, by the nature of his business, to maintain the sitting posture daily, for hours together, exercising pressure on the nerve ”