256 Neuroanatomy: Draw It to Know It
Peduncles, Midline Structures, Arteries
I. Cerebellar Peduncles
Here, we will draw the cerebellar peduncles, the fl occu-
lonodular lobe and paired tonsils, and the cerebellar
arterial supply.
Begin with one of the saddle-shaped cerebellar hemi-
spheres. Next, add the cerebellar peduncles: superior,
middle, and inferior. To illustrate the fl ow through these
pathways, redraw the cerebellar peduncles adjacent to
the rest of our diagram.
First, show that the middle cerebellar peduncle is
an aff erent pathway into the cerebellum; it is reserved
for fi bers that originate in pontine nuclei. Next, indi-
cate that the inferior cerebellar peduncle is also an
aff erent pathway into the cerebellum; it receives fi bers
from throughout the brainstem and spinal cord. Now,
show that the cerebellum sends eff erent fi bers out
through the superior cerebellar peduncle. Th us, the main
infl ow pathways into the cerebellum are the middle
and inferior cerebellar peduncles and the main outfl ow
peduncle from the cerebellum is the superior cerebellar
peduncle.
Next, let’s list the main exceptions to this rule.
Indicate that the anterior spinocerebellar tract enters
the cerebellum through the superior cerebellar peduncle,
which defi es this peduncle’s role as an outfl ow pathway.
Th en, indicate that select midline cerebellar tracts exit
the cerebellum through the inferior cerebellar peduncle,
which defi es this peduncle’s role as an infl ow pathway.
Specifi cally, these midline pathways are the fastigiobul-
bar fi bers, the fi bers from the fl occulonodular lobe to
the brainstem vestibular nucleus, and certain monosyn-
aptic cerebello-spinal connections.
Now, let’s expound upon the major pathways that do
follow the general infl ow/outfl ow rule. Show that the
middle cerebellar peduncle comprises corticopontocer-
ebellar fi bers (see Drawing 15-7 ), which are critical for
the modulation of movement. Th en, indicate that three
of the four spinocerebellar pathways enter the cerebel-
lum through the inferior cerebellar peduncle: the poste-
rior spinocerebellar tract, cuneocerebellar tract, and
rostral spinocerebellar tract. As mentioned, the fourth
spinocerebellar tract, the anterior spinocerebellar tract,
defi es the general organization of cerebellar infl ow and
enters the cerebellum through the superior cerebellar
peduncle. Next, show that the brainstem pathways that
enter the cerebellum through the inferior cerebellar
peduncle are the reticulo- and trigeminocerebellar fi bers,
the olivocerebellar fi bers (known as climbing fi bers), and
fi bers from the vestibular nucleus and nerve, itself.
Now, indicate that the pathways that exit the cerebel-
lum through superior cerebellar peduncle are the denta-
torubal and dentatothalamic tracts, which project
rostrally; the dentatoreticular tract, which projects cau-
dally; and fi bers from the globose and emboliform nuclei,
which reach the region of the red nucleus responsible for
the rubrospinal tract.