The Venetian physician Nicolò Massa noted in his 1536 publication Anatomiae Libri Introductorius that there appeared to be fluid within cerebral ventricles. More than one hundred years later, Humphrey Ridley published the first English-language manuscript about brain anatomy, which also made note of the presence of cerebrospinal fluid within the ventricles. The anatomist Antonio Maria Valsalva, whose name we know from his eponymous maneuver, and whose primary interest was the workings of the human ear, in 1692 described cerebrospinal fluid as existing within the subarachnoid space around the spinal cord.
In Italy in the 1700s, Domenico Cotugno literally turned on its head the then-traditional method of performing autopsies (severing the head from the rest of the body before dissecting the brain), by instead keeping the bodies intact and positioning them upside down. This allowed him to observe fluid beneath the dura mater, the tough covering surrounding the brain and spinal cord, and within the ventricles of the brain. For a time, due to his discovery, cerebrospinal fluid was called “liquor Cotunnii,” or Cotugno’s liquid. Still, it wasn’t until 1842 that the French physician François Magendie coined the term “cerebrospinal fluid” and discovered a means of measuring its pressure, laying the foundation for the development of cerebrospinal fluid dynamic research. And yet even then Magendie’s contemporaries, including neurologists Albert von Haller and Moritz Romberg, argued that the brain’s networked series of cavities—the ventricles—were filled with some kind of humid gas instead of fluid.
Working in isolation, somewhat outside of the medical profession, was a Swedish engineer turned anatomist turned theologian named Emanuel Swedenborg, who between 1741 and 1744 came up with a visionary description of cerebrospinal fluid that wasn’t widely recognized until his work on the subject was published posthumously in 1887. His insights into cerebrospinal fluid and the cerebral cortex coincided with a time in his life when he experienced a spiritual awakening that led him to believe he had been appointed by Jesus Christ to reform Christianity, starting a religious movement that continues to this day. Somehow, along the way, he managed to investigate the mysteries of CSF, referring to it as “spiritous lymph” and “highly gifted juice.” In a kind of fluid-filled echo of the ancient conclusions Galen held about the gaseous animal spirits of human consciousness residing in the pockets of the brain, Swedenborg believed the cerebrospinal fluid to be where the soul resides. Swedenborg also greatly influenced Andrew Taylor Still, the founder of osteopathy (a branch of medicine concerned with managing health through the manipulation of bones, joints, and muscles). Both Still and Swedenborg believed in the idea of cerebrospinal fluid as the location of the soul, and vital to overall health. As Still put it: “The cerebrospinal fluid is the highest known element in the human body. He who is able to reason will see that this great river of life must be tapped and the withering field irrigated at once or the harvest of health is forever lost.” Other osteopaths, such as Randolph Stone, who went on to found something he called polarity therapy—a kind of holistic energy healing practice—also characterized CSF as a spiritual “liquid medium for . . . life energy radiation, expansion, and contraction.” Stone said, “Where this is present, there is life and healing with normal function. Where this primary and essential life force is not acting in the body, there is obstruction, spasm, or stagnation and pain, like gears which clash instead of meshing in their operation.” Even modern-day naturopaths such as New Mexico doctor Robert Stevens subscribe to this view of cerebrospinal fluid as something spiritual and holy: “On the physical level, cerebrospinal fluid becomes the physical carrier of the wisdom of the Soul. This fluid conveys the sound and light energies of the Soul throughout the physical body. CSF expresses this highest vibratory rate and intelligence to the whole physical body.”
Outside of the community of visionaries and spiritual osteopaths, for hundreds of years the consensus was, among most physicians, that the primary function of cerebrospinal fluid was to protect and cushion the brain. It took until the early twentieth century for cerebrospinal fluid to be recognized as playing a crucial role in the function of the entire central nervous system. Harvey Cushing, the father of neurosurgery, called this the “third circulation” in a 1925 paper that established CSF physiology as a crucial aspect of neuroscience. He saw the flow of cerebrospinal fluid as a circulatory system similar to vascular and lymphatic circulation, and introduced the idea of cerebrospinal fluid and its circulation as a kind of lymphatic system for the brain, clearing out waste. He suggested that cerebrospinal fluid flows through the ventricles, cisterns, and subarachnoid space, and is reabsorbed into the blood at the arachnoid villi—from arachne, meaning spider, and villus, shaggy hair, these are spidery, hair-like projections of fibrous tissue protruding from the arachnoid membrane.
There are three membranes surrounding the brain and spinal cord, collectively known as the meninges, and the dura mater is the outermost of the three. These membranes—the pia mater (tender mother, attached to the surface of the brain and spinal cord), the arachnoid mater (spider-like mother, the middle layer, named for its spiderweb appearance), and the dura mater (tough mother, named for its durability and strength)—protect the central nervous system. The dura is, true to its name, normally a quite dense and fibrous connective tissue, which functions somewhat like a sac encapsulating the brain and spinal cord, extending to the sacrum, beyond the base of the spinal cord.
It’s the dura that keeps the cerebrospinal fluid contained. The fluid moves within it, pulsing from the inner recesses of the brain, and traveling along the length of the spinal cord, coating the entire central nervous system. When the dura mater is pierced or torn from trauma or injury or medical procedures gone wrong, cerebrospinal
