344 Neuroanatomy: Draw It to Know It
The Diencephalon
Here, we will draw the anatomy of the diencephalon.
First, list the major groups of diencephalic structures:
the thalamus, metathalamus, subthalamus, hypothala-
mus, and epithalamus. Now, include the major structures
categorized within these groups. Indicate that the thala-
mus contains numerous thalamic nuclei and related fi ber
tracts; the metathalamus comprises the medial and lat-
eral geniculate nuclei; the subthalamus comprises the
subthalamic nucleus, zona incerta, and the nuclei of the
fi elds of Forel; then, show that the hypothalamus con-
tains numerous hypothalamic nuclei and related fi ber
tracts, and also contains the mammillary bodies, and
neurohypophysis, which is the posterior lobe of the pitu-
itary body and which subdivides into a neural lobe and
infundibulum; then, show that the epithalamus com-
prises the habenula, pineal gland, and the pretectal struc-
tures, which include the pretectal area, pretectal nuclei,
posterior commissure, and subcommissural organ.
Finally, let’s list some of the major white matter bundles
that pass through the diencephalon: the column of the
fornix, stria medullaris thalami, and the anterior, poste-
rior, and habenular commissures.
Now, let’s draw the diencephalon in sagittal view.
First, label the central portion of the diagram as the
hypothalamus and then defi ne its borders. Draw the
lamina terminalis as the anterior border of the hypothal-
amus; it separates the hypothalamus from the subcallosal
region of the limbic lobe and it is variably considered
either a diencephalic or telencephalic structure. Indicate
that the lamina terminalis spans from the anterior com-
missure, superiorly, to the optic chiasm, inferiorly.^1 – 3
Next, draw the tuber cinereum as the inferior border of
the hypothalamus. Show that it ends, posteriorly, at the
mammillary bodies.
Next, antero-inferiorly, draw the funnel-shaped dip in
the tuber cinereum called the median eminence; attach
to it the infundibulum (the pituitary stalk); and attach
to the infundibulum, the pituitary gland. Label the
posterior part of the pituitary gland as the neural lobe;
it is neurally connected to the hypothalamus via the
hypothalamohypophysial tract. Th en, label the anterior
lobe of the pituitary gland as the adenohypophysis; it
forms from Rathke’s pouch — an outgrowth of the roof
of the mouth, and therefore, it is not a diencephalic
structure. Th e adenohypophysis is linked to the hypo-
thalamus via the hypothalamohypophysial venous portal
system.^4 , 5
Now, for anatomic reference, include the midbrain
and its superior and inferior colliculi. Th en, draw the
epithalamic structures: fi rst, above the colliculi, draw the
pineal gland; anterior to it, draw the pretectal structures;
and then above them, draw the habenula and habenular
commissure. Next, anterior to the epithalamus, draw the
egg-shaped thalamus. Th en, indicate that the stria med-
ullaris thalami passes from the habenula along the dorso-
medial thalamus to the septal nuclei, which lie above the
anterior commissure (they are part of the limbic system).
Finally, show that the column of the fornix descends
through the hypothalamus and connects with the mam-
millary bodies.
Next, we will draw the central diencephalon in coro-
nal view. For anatomic reference, superiorly, include the
corpus callosum, body of the fornix, body of the lateral
ventricle; then, laterally, include the internal capsule,
which becomes the cerebral peduncle as it descends
through the brainstem; next, inferiorly, draw the pons;
in midline, lying medial to the cerebral peduncle, draw
the interpeduncular cistern; and above it, draw the third
ventricle. Now let’s draw the major diencephalic struc-
tures visible in this section: superiorly, draw the thala-
mus; ventrolateral to it, draw the subthalamus; and
ventromedial to it, along the lateral wall of the third ven-
tricle, draw the hypothalamus and include its infero-lying
mammillary bodies. Finally, show that the supramam-
millary commissure stretches across midline above the
mammillary bodies.^6 – 8