NEURALGIA OF THE SCIATIC NERVE is one of the most severe and common forms. While sharing in the common etiology and history of the other neuralgias, it is peculiarly prone to be due to peripheral causes, which give rise to thickening of interstitial and investing connective tissue of the nerve. The distribution of the pain may be coextensive with the whole distribution of the great and little sciatic nerve, but far oftener the patient indicates certain regions as the seat of his severest suffering; and these are especially the sacral region of one side, the neighborhood of the sciatic notch, the popliteal space, the calf, and the outer side of the foot and ankle. Not infrequently the whole course of the sciatic nerve is traced out by the darts of pain; and in this case it is the nerves which supply the sheath of the sciatic itself which are supposed to be the seat of the neuralgic process.
Sciatica is usually unilateral, but exceptionally bilateral, or attacks the two sides alternately. The tender points most often met with are at the sacro-iliac synchondrosis, the posterior border of the great trochanter, just beneath the head of the peroneal bone, below and behind the external malleolus, but numerous others are likewise noted by Valleix. Sometimes no tender points can be found. Sometimes, also, it is one or more of the collateral branches of the sciatic plexus that are the seat of the neuralgia, and the distribution of the pain and of the tender points varies accordingly.
It is in sciatica pre-eminently—in part, no doubt, because of the frequency of neuritis—that disorders of sensibility of the skin are noticed, as well as muscular paresis or spasm. This anæsthesia has been studied with great care by Hubert-Valleroux and others, and it has been shown that it is often confined to limited spots, a centimeter or so in diameter, within which the loss of sensibility may be nearly absolute. Nevertheless, their functional origin is proved by the fact that under faradization they may rapidly disappear.
The duration of an attack of sciatica varies from a week or two to months or even years, and it shows a marked liability to recur, especially with changes of weather. First attacks occur pre-eminently, though not exclusively, in middle life, and oftener in men than in women, evidently because they are oftener exposed to mechanical injury and, through their occupations, to sudden changes of temperature and the like.
The occasional causes are numerous, and include sudden wrenches and jars, even if not very severe, interpelvic pressure from tumors or impacted feces, etc. Gout, syphilis, and diabetes may act as predisposing and even exciting causes, and, it is said, gonorrhœa likewise. Periarthritic inflammations of the hip-joint and varicose veins frequently excite pains in the various sciatic nerve-branches which simulate true sciatica.
As has been indicated, although sciatica may be a pure neuralgia (see under Pathology), running its course without leading to any appreciable change in the nerve, yet subacute and chronic neuritis is very common, either as a primary condition or a complication, and its presence puts a graver aspect upon the case. The pain of neuritis, when severe, is relatively constant, remittent instead of intermittent, dull rather than lancinating, increased by motion and pressure; whereas the purely neuralgic pains are sometimes relieved by movement. It is, however, doubtful whether an accurate differential diagnosis is possible (see above). It is to this neuritis that the muscular atrophy is due which is often so marked, and it may likewise give rise to various cutaneous lesions of herpetic character. The severe pain that accompanies typical herpes zoster of this region is well known.
The TREATMENT of sciatica must vary with the probable cause of the disease and its stage of progress. Diathetic taints are to be met if present, and the greatest measure of physical health secured that the circumstances possibly admit. It is a good precaution in all cases to secure free evacuation of the bowels and to guard against hemorrhoidal congestions.
As against the neuralgia itself, the proper means vary with the acuteness of the attack and the presence or absence of neuritis. For the acute stage absolute rest is almost always desirable as a prime condition. Quinine, belladonna, aconite, and turpentine in full doses should be thoroughly tried, and special reference had to the periodicity of the seizures.
Frequent and extensive but superficial counter-irritation (actual cautery, blistering, ether, or chloride of methyl) is in place in this stage, and galvanism (constant current) is often of great service. It is probable that for the acute stage the prolonged use of mild currents is the best, whereas in more chronic cases the stronger, even very strong, currents, brought to bear as accurately as possible upon the nerve itself, are sometimes more useful.
Hydropathic treatment is in great repute both for acute and chronic cases, but as success in this way demands care and knowledge, the reader is referred to the special treatises.