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Proceedings SNO “LXI Congresso Nazionale SNO”

brana tenuis” (thin and fine), hence designated as of the central nervous system. HEROPHILUS OF
“leptomeninx”, that included the arachnoid and pia CHALCEDON (ca. 325-280 B.C.) performed systemic
mater, without distinguishing between the two. dissection and these examinations contributed to a
It was not until the 17th century that anatomists dis- huge amount of medical knowledge. The first ac-
covered a layer separating the pia mater from the du- count of the detailed topography of the meninges was
ra mater and named this cobweb-like layer the given by Herophilus, whose work is unknown save
“arachnoid”, so named because of its spider web-like through its survival in Galen. Herophilus was the first
appearance. The Greek term “arakhnoeides” is de- to described the choroid plexus, so named by him for
rived from “arachne”, which means “spider”, or its resemblance to the vascular membrane of the fe-
“spider’s web”, and “eidos”, which means “shape”. tus. He described the ventricles and its linings, which
The term arachnoid has an interesting etymology that he named “choroid meninx”.
can be traced to the ancient Greek myth of Arachne, CLAUDIUS GALEN (ca. 129-201) has been considered as
a young girl who challenged the goddess Pallas one of the earliest authors mentioning the meninges of
Athena in a weaving contest. After she lost, and as re- the brain in his dissections performed only in animals
ward for her boldness; she was transformed into a and differentiated between the dura mater and pia
spider, so she could exercise her weaving skills. mater. His anatomical work was based on studies per-
formed in monkeys and these observations were then
arbitrarily adapted to humans. Galen discovered a soft
HISTORY layer closely adjacent to the brain itself. He noticed
that the dura mater is closely attached to the inside of
Whereas the dura mater and pia mater have been de-
the skull, leaving room beneath for the brain.
scribed since the time of the Egyptians some 3,000
During the late Middle Ages GUIDO DA VIGEVANO
years ago, the arachnoid was not clearly distinguished
(1280-1349) was the first to use images to illustrate
as a separate layer. Ancient anatomists seem to have
anatomical descriptions in the texts, a trend devel-
overlooked the arachnoid membrane, they have identi-
oped in the Renaissance. In his treatise, Anathomia
fied and dissected the dura mater and the pia mater, the
arachnoid membrane was left undescribed. Designata per Figures published in 1345, he shows
an innovation at the time: the presence of anatomical
The dura mater was already known to the Egyptians.
illustrations. These illustrations, although schematic
In the Edwin Smith Surgical Papyrus, which is most
and rudimentary, can be considered as the first neu-
probably a copy made in I700 BC of a manuscript
ro-anatomical drawings in history of neuroscience.
composed about 3000 BC, there appears a reference to
The drawings imply an approach based on personal
the first description of a brain with meninges as cover-
experience through the dissections on hanging
ings of the brain. However, the description in this pa-
pyrus is limited to what is believed to be the dura corpses, thus demonstrating human anatomy by
mater. HIPPOCRATES (ca. 480-390 B.C.) makes refer- means of schematic plates, “... demonstrabo anatho-
miam corporis humani patenter et aperte, per figuras
ence to the meninges, stating that one is thick whereas
the other is thin, and explains that the brain is divided depinctas recte...”, considered an important mile-
stone for the development of subsequent anatomical
in two halves separated by a membrane. ARISTOTLE
(ca. 384-322 B.C.) described the two layers of sciences in the Renaissance. There are six plates de-
meninges. He mentioned the membranes enveloping picting for the first time the structures of the central
the brain that may be seen in animal dissections, both nervous system. Plate XIV shows the removed cra-
outer and inner membranes; the outer meninx lying nial vault, on which it is possible to recognized the
next to the bone, and thick and strong in texture; the external (“illa pellicular que vocatur dura mater”)
inner consisting of a fine network of minute blood ves- and internal (“vocatur pia mater, cerebrum coope-
sels, lying in close contact with the brain itself. riens”) meningeal layers, the dura and pia mater. He
No evidence in the Western medicine supports the shows also the surface of the brain, a “naked” brain
use of illustrations in medical texts before the ancient (“cerebrum purum et discoopertum”) without the
Greeks. The oldest illustrations available are from meninges, where it is possible to recognize a vague
Alexandria and date to about 300 B.C. ERASISTRATUS patterning on the surface with some sulci and gyri. It
OF CHIO (ca. 310-250 B.B.) was the first to use the seems to be the earliest portrayal of cerebral convo-
term “meninges” to describe a membranous covering lutions (Figure 1).

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