252 Neuroanatomy: Draw It to Know It
Lobes, Zones, & Modules
Here, we will use a fl attened perspective of the cerebel-
lum to learn the cerebellar anatomic lobes, zones, and
functional modules. To understand how unfolding the
cerebellum aff ects our perspective of it, draw a sagittal
section of the folded cerebellum and then show that we
peel back the anterior cerebellum so that the anterior
lobe ends up at the top of the diagram and the fl occu-
lonodular lobe ends up at the bottom.
Now, draw the corpus cerebelli, which comprises the
anterior and posterior cerebellar lobes and constitutes
the bulk of the cerebellum. On the right, we will draw
the cerebellar lobes, and on the left , we will draw the cer-
ebellar zones.
Begin with the lobes: show that the primary fi ssure
separates the corpus cerebelli such that the anterior one-
third of the corpus cerebelli forms the anterior lobe and
the posterior two-thirds forms the posterior lobe. Next,
below the corpus cerebelli, draw the propeller-shaped
fl occulonodular lobe: label its nodule in midline and
fl occulus out laterally. Show that the posterolateral fi s-
sure separates the corpus cerebelli from the fl occulonod-
ular lobe.
Now, let’s draw the cerebellar zones. Indicate that the
midline cerebellum is the vermis (which means worm-
like); then, lateral to it, denote the paravermis (aka the
intermediate zone); and lateral to it, label the hemisphere
(aka the lateral zone).
Next, let’s address the functional modules; show that
we will specifi cally address the module name, its anatomy
and function, and the exam defi cit observed when the
module is injured.
Indicate that the fl occulonodular lobe combines with
the anterior tip of the vermis (the lingula) to form the
vestibulocerebellum. Th e vestibulocerebellum receives
its name because of its midline vestibulo- and olivocere-
bellar fi bers, which project to the deep, medial-lying cer-
ebellar fastigial nuclei. Show that this functional module
is important for equilibrium and eye movements.
Next, show that the anterior lobe combines with
the majority of the vermian and paravermian posterior
lobe to form the spinocerebellum. Th e spinocerebellum
receives its name from its major input fi bers: the spinoc-
erebellar tracts. Show that this functional module plays a
major role in postural stability.
Now, indicate that the remainder of the posterior
lobe forms the pontocerebellum, which receives its name
because it acts through the corticopontocerebellar path-
way. Show that this functional module is geared towards
goal-directed, fi ne motor movements.
In acute alcohol intoxication, the entire cerebellum is
aff ected: show that in this setting, nystagmus occurs
from toxicity to the vestibulocerebellum, truncal ataxia
occurs from toxicity to the spinocerebellum, and incoor-
dination occurs from toxicity to the pontocerebellum. In
contrast, in alcoholic cerebellar degeneration, the pathol-
og y is predominantly restricted to the anterior superior
cerebellar vermis; therefore, truncal ataxia is sometimes
the sole defi cit. We may miss this exam fi nding, if we fail
to ask our patients to stand during the exam.
As a fi nal note on nomenclature, indicate that each
functional module is synonymously named based on
its stage of phylogenic development. Th e vestibulocere-
bellum is phylogenetically the oldest portion of the cer-
ebellum and is referred to as the archicerebellum; the
spinocerebellum is phylogenetically the next oldest and
is referred to as the paleocerebellum; and the pontocer-
ebellum is phylogenetically the newest portion of the
cerebellum and is referred to as the neocerebellum.^1 – 11