A significant step forward in the field occurred in 1764, when Domenico Cotugno (1736–1822) (Fig. 2.2), anatomist and professor of surgery in Naples, published De ischiade nervosa commentarius (“Remarks on nervous ischialgia”) (Fig. 2.3), which defined sciatica as a clinical entity and related the pain in the leg to disease of the sciatic nerve. He distinguished pain of the lower limb of “arthritic” origin, or “arthritic sciatica,” identified as hip pain, from pain of “nervous” origin or “nervous sciatica,” which was classified as “postica” (posterior) or “antica” (anterior). He accurately differentiated sciatic nerve pain from arthritis of the hip with a precise description of the clinical status and by indicating the relationship of pain to the sciatic nerve [1]:

If the pain indicated by the patient’s finger runs from the foot to the sacrum, as competent anatomists we must evaluate this patient by tracing the precise course of the sciatic nerve. The patient’s pain is felt in this nerve, and we should look for the cause of their limping in this nerve, and for the origin of paresis and impairment in this disease.

It is thus how the eponym “Cotugno’s syndrome” found its way into medical vernacular to indicate a unilateral sciatic neuralgia. Cotugno attributed these symptoms to the accumulation of an acrid matter within the sheath of the sciatic nerve that had derived from the vessels irrigating the sheaths of the nerve or from the brain itself. In order to prove the existence of free circulation between the cranial and spinal dura, he propped cadavers upright on their feet and then decapitated them so as to observe the flow of cerebrospinal fluid. Twenty headless cadavers stood in for the cause which established the existence of this free circulation of the “Liquor Cottunnii,” the first known reference to cerebrospinal fluid.

His description of this “Liquor Cottunnii,” or cerebrospinal fluid as we know it today, included a precise indication as to its formation and absorption from the vessels. From this, Cotugno postulated its relationship with sciatica [1]:

The cerebrospinal liquor is in perenni statu renovationis, through exudation by minimal arteries and reabsorption through minimal veins. It penetrates into the dural sleeves of the nerve roots; hence, it is apt to accumulate in the sheaths of the sciatic nerve and as so promote pain along its course. The sciatic pain, weakness and limping may be cured, if necessary, by the use of vesicants and caustics in order to leech out the hydrops.

Within the folds of the history of sciatica, there were intermittent parallel investigations into the intervertebral disk; however, such findings were not correlated with sciatica. Nearly a hundred years after Cotugno’s landmark work, Rudolf Virchow (1821–1902) (Fig. 2.4) described the first case of traumatic rupture of the intervertebral disk. This rupture, known as “Virchow’s tumor,” was discovered during the necropsy of a trauma victim [2].

In 1896 Swiss surgeon Kocher documented the first case of a disk displacement leading to paraplegia; however, its clinical correlation to sciatica remained moot [3]. The patient developed paraplegia after a fall and subsequently succumbed to injury to the internal organs. During necropsy, Kocher identified dorsally displaced disk at L1–L2. Sciatica and the lumbar region would remain dissociated until the beginning of the twentieth century. Until the late nineteenth century, sciatica was interpreted as a sciatic nerve pain, a neuralgia, or neuritis. The cause remained unknown, and the authors were limited to describing symptoms.

French neurologist, Lasègue (1816–1883) (Fig. 2.5) called attention to a pain provoked by lifting the leg in patients with sciatica. He later demonstrated that this phenomenon was due to the stretching of the sciatic nerve roots (1864) [4]. Although his medical writings do not mention this sign, it was his former pupil, Forst, who published the findings of his master and illustrated the “Lasègue maneuver” for the first time (Fig. 2.6) [6].

Concurrently, another French physician, François Valleix (1807–1855), identified specific sensitive points within the course of the sciatic nerve. These anatomic points, known today as Valleix’s points, are points at which pain is experienced upon pressure in cases of neuralgia. Valleix’s points are in fact segments of the sciatic nerve that are accessible to palpation in patients with sciatic pain. Along the sciatic nerve these segments lie in the buttocks, thigh, leg, and foot [7].

It were Charcot and Brissaud who in 1888 described “sciatica scoliosis,” abnormal postures that were in fact caused by severe sciatica. They accurately distinguished crossed and ipsilateral scoliosis. In crossed scoliosis, the trunk is inclined laterally toward the side not affected by sciatica. In direct or ipsilateral scoliosis, the lateral inflection of the spine always tilts toward the side affected by sciatica [7].

For sciatica, the early twentieth century opened to the phenomena of “sensorimotor radiculitis.” Dejerine demonstrated that sciatica is a root condition and not a truncal condition. He noted that some cases of sciatica are accompanied by areas of hypesthesia or cutaneous anesthesia, and the distribution of the insensitive areas did not correspond to the areas of the sciatic nerve branches but rather to the areas of the nerve roots. These cases of cutaneous anesthesia corresponded more precisely to the areas of the fifth lumbar nerve root and first sacral nerve root. He defined the phenomenon as a sensorimotor radiculitis caused by “partial lumbar meningitis,” following the then-current interpretation of the impairment of the nerves and roots by inflammation caused by syphilis [7].

At the transition between the height of inductive reasoning and the dawn of evidence-based medicine, the French medical establishment reigned supreme. Continuing in that fine tradition, Jean-Anselme Sicard (1872–1929), a neurologist, presented sciatica in 1918, as a condition caused by spinal conditions. He advanced the hypothesis that compromise of the roots that form the sciatic nerve does not occur within the dural sac but outside the dura mater, at its exit of the intervertebral foramen. Furthermore, he postulated that the cause of this impairment in the roots could be due to bony and ligamentous elements surrounding the root within the intervertebral foramen. He was of course inferring to the fact that the thick sciatic nerve roots, especially the L5 root, pass within a particularly narrow osteoligamentous canal [7].

So it seems that by the start of the twentieth century, the road map into the scientific understanding had been laid. Social circumstances of the new century such as the progression of modern thought with its exchange of ideas and technology, particularly the invention of anesthesia conspired to favor the advancement of surgical technique and subsequently to what was once all-encompassing sciatica, would now become the consequence of lumbar intervertebral disk degeneration.

First of these advancements was the hypothesis that sciatica might be associated with herniated lumbar disk. There was then a small but growing body of surgical reports of uncommon benign tumors, chondromas on patients undergoing surgical treatment for sciatica. Mixter and Barr were at the vanguard of these advancements demonstrating that such lesions corresponded to a herniated disk.

Victor Horsley, in 1887, is credited to be the first surgeon to remove such a tumor; however, the association to sciatica was not recognized. In fact, the first successful removal of a herniated disk took place in 1901 via laminectomy under the hands of Fedor Krause (1857–1937) (Fig. 2.7) and Hermann Oppenheim. They removed what they had thought was an “enchondroma” [8].