History of neurology

The study of neurology dates back to prehistoric times, but the academic discipline did not begin until the 16th century. From an observational science it developed a systematic way of approaching the nervous system and possible interventions in neurological disease.

Early history


An ancient Egyptian treatise concerning trauma surgery, the Edwin Smith papyrus, contains descriptions and suggests treatments for various injuries, including some of neurological nature. Specifically, there are descriptions of the meninges, the external surface of the brain, the cerebrospinal fluid and the intracranial pulsations. Not only are these neurological features mentioned, but it is also noticed that some bodily functions can be impaired by brain injuries or injuries to the cervical spine.

There are many other examples of observations of neurological phenomena throughout history. The Sumerians illustrated paraplegia caused by physical trauma in a bas relief of a lion with an arrow in its back. Neurological disorders not caused by physical disorder were also investigated. For example in the medicine of the Vedic period of ancient India, the Ayurvedic text Charaka Samhita discusses epilepsy, with a discussion of both symptoms and of possible treatments. Slightly later, the ancient Greek physician Hippocrates was convinced that epilepsy has a natural cause, not a sacred one.

The ancient Greeks also dissected the nervous system. For example, Aristotle (although he misunderstood the function of the brain) describes the meninges and also distinguishes between the cerebrum and the cerebellum. Slightly later, in Rome, Galen performed many dissections of the nervous system in a variety of species, including the ape. One particular discovery he made was of the importance of the recurrent laryngeal nerves. Originally, he cut through them accidentally while performing an experiment on the nerves that control breathing by vivisection of a strapped-down, squealing pig. The pig immediately stopped squealing, but continued struggling. Galen then performed the same experiment on a variety of animals, including dogs, goats, bears, lions, cows and monkeys, finding similar results each time. Finally, to publicise this new result, Galen demonstrated the experiment on a pair of pigs to a large audience in Rome, telling them: "there is a hairlike pair [of nerves] in the muscles of the larynx on both left and right, which if ligated or cut render the animal speechless without damaging either its life or functional activity"

Anatomy and physiology
Along with most other sciences, the first real advances in neurology after the Greeks occur in the Renaissance. The invention of the printing press allowed the publication of anatomical textbooks, allowing the dissemination of knowledge. An early example is Johann Peyligk's Compendium philosophiae naturalis, published in Leipzig, Germany in 1499. This work contained 11 woodcuts, depicting the dura mater and pia mater as well as the ventricles.

A revolution took place in both neurology in particular and in anatomy in general when Andreas Vesalius published his De humani corporis fabrica in 1543. It includes detailed images depicting the ventricles, cranial nerves, pituitary gland, meninges, structures of the eye, the vascular supply to the brain and spinal cord, and an image of the peripheral nerves. Vesalius also exposed the non-existence structures that had been believed to be in the brain since Galen's (revered) work, such as the rete mirabile. Galen's dissections were all on animals – in particular, the rete mirabile is only well developed in ungulates. Vesalius, unlike many of his contemporaries, did not subscribe to the then common belief that the ventricles were responsible for brain function, arguing that many animals have similar systems of ventricles to those of humans, but had no true intelligence. It appears that he rarely removed the brain from the skull before cutting it, most of his diagrams showing the brain sitting inside a severed head.

Thomas Willis in 1664, published his Anatomy of the Brain, followed by Cerebral Pathology in 1676. He removed the brain from the cranium, and was able to describe it more clearly, setting forth the circle of Willis – the circle of vessels that enables arterial supply of the brain. He had some notions as to brain function, including a vague idea as to localization and reflexes, and described epilepsy, apoplexy and paralysis. As already mentioned, he used the word neurology.

A beginning of the understanding of disease came with the first morbid anatomists, morbid anatomical illustration, and the development of effective colour printing. Matthew Baillie (1761–1823) and Jean Cruveilher (1791–1874) illustrated the lesions in stroke, in 1799 and 1829 respectively.

Microscopy
Only when cells were identified microscopically was it possible to progress beyond the crudest anatomical notion. J.E. Purkinje (1787–1869) in 1837 gave the first description of neurones, indeed a very early description of cells of any kind. Later Golgi and Cajal stained the ramifying branches of nerve cells; these could only touch, or synapse. The brain now had demonstrated form, without localised function. The famous philosopher René Descartes (1596–1650) speculated that every activity of an animal was a necessary reaction to some external stimulus; the connection between the stimulus and the response was made through a definite nervous path. Luigi Galvani (1737–1798) demonstrated that electrical stimulation of nerve produced muscle contraction, and the competing work of Charles Bell (1774–1842) and Francois Magendie (1783–1855 ) led to the view that the ventral horns of the spinal cord were motor and the dorsal horns sensory. A hemiplegic patient who could not speak led Paul Broca (1824–1880) to the view that functions in the cerebral cortex were anatomically localised. Ivan Pavlov (1849–1936) realised as his dogs dribbled that a simple reflex could be modified by higher brain functions. These neurological ideas were coordinated and integrated by the neurophysiologist Charles Scott Sherrington (1857–1952).

Diagnostics
Physicians could use the ideas of neurology in practice only if they developed proper tools and procedures for clinical investigation. This happened step by step in the 19th century – tendon hammer, ophthalmoscope, pin and tuning fork, syringe and lumbar puncture. X rays, the electro-encephalography, angiography, and CAT scans were to follow. The clinical neurologists correlated their findings after death with those of the neuropathologist. The best known was W.R. Gowers (1845–1915) who owned a major text in two volumes, of a cerebrospinal tract. By the end of the nineteenth century, the connection was established between stroke and hemiplegia, between trauma and paraplegia, between the spirochaete and the paralysed demency people who filled the mental hospitals. The first chemotherapeutic cure of a serious infection was salvarsan for syphilis, followed by the induction of fever in neurosyphilis. The treatment of neurosyphilis became highly effective when antibiotics were introduced.

Neurosurgery
In 1878, William McEwen (1848–1924) removed a meningioma, and the patient survived for many years. Nine years later, Victor Horsley (1857–1916) was the first physician to remove a spinal tumour. Americans surgeon Harvey Cushing (1869–1939) successfully removed a pituitary adenoma from an acromegalic in 1909. Treating endocrine hyperfunction by neurosurgery was a major neurological landmark.

Egas Moniz (1874–1955) in Portugal developed a procedure of leucotomy (now mostly known as lobotomy) to treat severe psychiatric disorders. Though it is often said that the development of lobotomy was inspired by the case of Phineas Gage, a railroad worker who had an iron bar driven through his left frontal lobe in 1848, the evidence is against this.