254 Neuroanatomy: Draw It to Know It
Somatotopy & Lobules
Here, we will use a fl attened perspective of the cerebellum
to learn the cerebellar somatotopic map and the classifi -
cation of the cerebellar lobules. Once again, to under-
stand 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 occulonodular lobe ends up at the bottom.
To begin our diagram, draw the corpus cerebelli and
show that the primary fi ssure separates the anterior lobe
from the posterior lobe. Next, draw the fl occulonodular
lobe and indicate that the posterolateral fi ssure separates
it from the corpus cerebelli.
First, let’s address the somatotopic map of the cerebel-
lum. In clinical practice, remember the following : (1)
unilateral cerebellar lesions aff ect the ipsilateral side of
the body and (2) the midline cerebellum plays a role in
posture whereas the lateral cerebellum assists in fi ne
motor, goal-oriented skills. For instance, to stand upright,
you need the midline cerebellum, and to play the piano,
you need the lateral cerebellar hemispheres.
Now, show that the somatotopic map in the anterior
lobe looks like someone lying in a bathtub — arms and
legs coming out of the water. Next, show that the hands
extend into the posterior lobe. Th en, draw the mouth
beneath the fi ngers. Now, show that there is duplication
of the arms and legs in the posterior lobe.
As mentioned, the somatotopic map of the cerebel-
lum is in concert with its functional layout: the role of
the spinocerebellar anterior lobe is to provide postural
stability, which requires the limbs and trunk, and the
role of the neocerebellar posterior lobe is to provide
goal-oriented, fi ne motor movements, such as those of
the fi ngers and mouth.
Now, we will draw the classifi cation of the cerebellar
lobules — its numbering system and nomenclature is
quite confusing , so keep track. Th e midline, vermian cer-
ebellum divides into ten diff erent lobules and the hemi-
spheres divide into nine lobules. We’ll draw the vermian
lobules, fi rst, and then the hemispheric lobules.
Indicate that vermian lobule 1 sits above the superior
lip of the fourth ventricle and is named the lingula. Next,
show that lobules 2 and 3, together, form the central
lobule and then that lobules 4 and 5 form the culmen.
Posterior to the primary fi ssure, label lobule 6, which is
the declive. Show that lobule 7A is the folium and that
lobule 7B is the tuber; then, indicate that lobule 8 is the
pyramis and that lobule 9 is the uvula. Lobule 10 is the
nodule of the fl occulonodular lobe.
Now, let’s label the classifi cation of the cerebellar
hemispheric lobules. Show that except for lobule 1,
each vermian lobule has a hemispheric counterpart.
Hemispheric lobules 2 and 3 form the wing (or ala) of
the central lobule; lobules 4 and 5 form the anterior
quadrangular lobule; posterior to the primary fi ssure is
lobule 6, the simple lobule (aka the posterior quadrangu-
lar lobule); lobule 7A is quite large and forms the supe-
rior and inferior semilunar lobules (aka the ansiform
lobule); lobule 7B is the gracile lobule; lobule 8 is the
biventral lobule; lobule 9 is the tonsil. Finally, show
that lobule 10 is the fl occulus of the fl occulonodular
lobe.^1 – 11