The Journey of Discovering Skull Base Anatomy in Ancient Egypt and the Special Influence of Alexandria

Ali M. Elhadi, M.D.; Samuel Kalb, M.D.; Luis Perez-Orribo, M.D.; Andrew S. Little, M.D.; Robert F. Spetzler, M.D.; Mark C. Preul, M.D.

Disclosures

Neurosurg Focus. 2012;33(2):e2 

In This Article

Galen of Pergamon: AD 129–199

Galen, a Greek physician, surgeon, and philosopher, has garnered the greatest reputation of all physicians of ancient times. He came from a wealthy family. His father, an architect, died when Galen was 19 years old, leaving his fortune to his young son. Following the Hippocratic teachings, Galen traveled to Smyrna, Corinth, Crete, Cilicia, Cyprus, and finally to the great medical school of Alexandria to learn medicine.[14,15,32] He stayed in Alexandria until he was 28 years old.

He returned to Pergamon as physician to the gladiators of the High Priest of Asia, who was the wealthiest man in Asia at that time. Galen is said to have acquired this position after he eviscerated an ape in front of the priest and challenged other physicians to repair the damage. The physicians refused. Galen performed the surgery by himself and in so doing won the favor of the High Priest of Asia.

Galen learned most of his anatomical knowledge through dissections of apes and pigs because he studied in Alexandria during the period when human dissections were no longer allowed.[14] This is considered to be one of the reasons why distortions of anatomy are apparent in his writings. Based on the content of his writings, however, it is strongly believed that he participated in human dissections while living in Egypt. His knowledge of human anatomy was probably reinforced through trauma cases he attended to as physician to the gladiators. The basis of the anatomical education that he received in Alexandria certainly served him well in subsequent years.

Galen is responsible for some of the most voluminous medical writings of ancient times. In his work, he presented extensive arguments directed against Aristotle, who claimed that the brain came second to the heart. Aristotle thought that the brain's main function was to cool the heart through phlegm produced by the brain. Galen opposed this concept. He clearly explains that the brain is the primary organ in the body that controls all vital activities,[33] and when it is injured or compressed, individuals lose sensation and movements: "If you press so much upon a cerebral ventricle that you wound it, immediately the living being will be without movement and sensation, without spirit and voice."[14]

Galen's work showcases the extent of neuroanatomical knowledge at that time. He understood that it is impossible to ignore the function of the brain because it had connections to all parts of the body, especially to the sense organs near the brain. Like his contemporaries, he described the meninges and mentions that the inner membrane enclosed many arteries and veins as it followed the sulci of the brain (arachnoid).

Galen also tracked most of the cranial nerves.[14]

But, said Aristotle, all the organs of the senses do not abut on the brain. What is this language? I blush even today to cite this statement. Does not a considerable nerve enter into one and the other ear with the membranes? Does not a part of the brain descend to each side of the nose [olfactory nerves], even more important than that which goes to the ears? Does not each of the eyes receive a soft [sensory] and a hard [motor] nerves, the one inserting at its root, the other on the moving muscles? Do not four of them go to the tongue, two soft ones penetrating by the palate [hypoglossal?, lingual?], two other hard ones descending through the ear [chorda tympani?]? Thus, if one must put faith in one's eyes and touch, all the senses are in relationship with the brain. Shall I announce the other parts that enter into the structure of the brain? Shall I say what use is provided by the meninges, the reticular plexus [rete mirabile], the pineal gland, the pituitary body, the infundibulum, the lyre [fornix], the vermiform eminence [vermis], the multiplicity of the ventricles, the openings by which they communicate with one another and the variety of configurations, the two meninges, the processes that go to the spinal marrow, the roots of the nerves that abut not only on the organs of the senses but also on the pharynx, on the larynx, the oesophagus, the stomach, and all the viscera and all the intestines, and go to all the parts of the face? Aristotle did not attempt to explain the use of any of these parts … but the brain is the source of all the nerves.

Since the Alexandrian anatomists had first mentioned the name rete mirabile (attributed to Herophilus), no description of the blood vessels of the brain was known until the time of Galen. He described the blood supply of the brain as follows:[14]

That plexus called reticular by anatomists, the plexus that embraces the [pituitary] gland itself and extends for a great distance posteriorly, is the most remarkable of the bodies found in this region. Indeed, it extends over almost the whole base of the brain. This network is not simple; one might say [it is] like the many threads of fishermen's nets placed one upon the other. But this naturally occurring net has the special quality that the meshes are so attached to one another that one would find it impossible to remove one of the threads without the other. If one of them is lifted up they are all lifted at the same time because they are all held together and attached to each other. No threads produced by the hand of man can compare with them in delicacy of composition or density of network. Moreover, its formation is no ordinary matter; the largest part of the arteries ascending from the heart to the head [carotid] has been employed by nature for this admirable network. Little branches are given off from these [carotid] arteries to the neck, face, and external parts of the head; all the rest, ascending in a straight line from their source, and mounting towards the head though the thorax and neck, are favorably gathered in that part of the cranium which, pierced with holes [carotid canal], allows them to pass without danger into the interior of the head.

It is impossible for Galen to have described the rete mirabile in such detail without his having repeatedly dissected the base of the brain and floor of the cranium to become intimately familiar with this cranial anatomy.

Galen detailed the course of the carotid artery as it is pierced and divided by the dura mater. He never provided names for these branches but stated the following:[14]

They are first divided into a great number of very small branches in the region between the skull and dura matter then travelling, some to the anterior part of the head, some to the posterior, some to the left side, some to the right, and interweaving, they give the impression that they have forgotten their route in the brain. But that is not all the case. In fact, all these numerous arteries come together again and unite like the roots of a trunk and form another pair of arteries like those that have already given birth to the network these latter arteries then penetrate into the brain by holes in the dura matter.

Galen also explained the venous system in great detail. He mentioned the different sinuses and their anatomical distributions; the great cerebral vein; and the dural folds, including the falx cerebrum, falx cerebellum, and tentorium. That he used fresh brains or even vivisected brains is obvious given that he also described how to dissect the human brain.[14]

It is then desirable to dissect the brain itself, beginning with the membranes dividing the anterior part [falx cerebrum]. When you have dissected or torn away from this the origins of the veins that extend laterally, beginning with the forward termination, raise it up with your fingers until you reach that large vein [great cerebral?] which extends from it and which we have said is carried deeply downwards. Again raising this upwards, give it to someone to hold, and then you yourself loosen it along its length and gently separate it with your fingers.

Galen extensively described the relationships among the brain, spinal cord, and cranial nerves. He believed that there were three kinds of nerves: sensory, motor, and hard nerves (tendons), which travel from bone to bone. He also described the spinal cord and numerous different levels of spinal cord injuries: "After the incision, in all the nerves which lie below the place where transaction has been made, both the two potentialities are lost, I mean the capacity of sensation and the capacity of movements… . Hence from the anatomy of nerves, you can easily infer the derangement."[14] The Alexandrian anatomists regarded the human cerebellum and the fourth ventricle as very important structures, and Galen agreed. He even considered the cerebellum as the source of motor function in association with the spinal cord. He claimed that the vermis acts as a valve to regulate the flow of the animal spirit through the ventricular system. Galen's extensive contributions provide a solid basis for understanding the extent to which skull base anatomy had been investigated in Egypt by the beginning of the 3rd century AD.

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