118 Neuroanatomy: Draw It to Know It
Spinocerebellar Pathways (Advanced)
Here we will draw the spinocerebellar pathways, which
carry proprioceptive sensory information to the cerebel-
lum for the coordination of movement and the mainte-
nance of posture. Th e spinocerebellar pathways comprise
the posterior, anterior, and rostral spinocerebellar tracts,
and the cuneocerebellar tract. Except for the cuneocere-
bellar tract, all of the spinocerebellar tracts synapse
within the spinal cord (generally within the intermedi-
ate zone of the gray matter) prior to reaching the cerebel-
lum. Th e posterior and anterior spinocerebellar pathways
are the best understood of these pathways; we will draw
them fi rst.
Draw an axial cross-section through the spinal cord.
In the corner of the diagram, write the words “tract” and
“origin.” We will list the origin of each spinocerebellar
pathway as we complete our diagram. First, indicate that
the posterior spinocerebellar tract originates from aff er-
ents of the lower trunk and lower limb. Now, to draw the
posterior spinocerebellar tract course, draw a peripheral
nerve and show its central process synapse in the inter-
mediate zone of the spinal cord from T1 to L2 in a region
called the dorsal nucleus of Clarke. Th e majority of the
posterior spinocerebellar tract aff erent fi bers arise from
below the L2 spinal level, ascend in the posterior funicu-
lus, and then make their synapse in the dorsal nucleus of
Clarke. Now, show that the dorsal nucleus of Clarke
projects via the ipsilateral inferior cerebellar peduncle to
enter the cerebellum.
Next, let’s draw the anterior spinocerebellar tract.
Indicate that it originates from aff erents of the lower
limb. Th en, to draw the anterior spinocerebellar tract
course, show the central process of a peripheral nerve
fi ber synapse at the L3 to L5 levels of the spinal cord.
Th e course of the anterior spinocerebellar tract is quite
long and involves a double decussation. Indicate that the
anterior spinocerebellar tract projects from L3 to L5
across midline within the ventral commissure, ascends
the spinal cord and brainstem within the anterior spi-
nocerebellar tract, enters the cerebellum within the supe-
rior cerebellar peduncle, and then decussates again within
the cerebellum to terminate on its side of origin (although
a small portion of fi bers terminate in the contralateral
cerebellum and do not make this last decussation). Th us,
through this double decussation, the anterior spinocere-
bellar tract remains ipsilateral to its side of origin. Note
that, generally, the inferior and middle cerebellar pedun-
cles are the infl ow pathways into the cerebellum and the
superior cerebellar peduncle is the outfl ow pathway for
fi bers from the cerebellum — the anterior spinocerebellar
pathway is an important exception to this rule.
Now, let’s draw the cuneocerebellar tract. Indicate
that the cuneocerebellar tract originates in the upper
limb and upper trunk. Th en, just beneath the inferior
cerebellar peduncle, label the lateral cuneate nucleus
(aka accessory cuneate nucleus) — the fi rst synapse of the
cuneocerebellar tract. Next, to draw the cuneocerebellar
tract course, show the central process of a peripheral
nerve fi ber enter the posterior column and directly
ascend the spinal cord to the lateral cuneate nucleus.
Th en, indicate that the cuneocerebellar fi bers project
from the lateral cuneate nucleus through the ipsilateral
inferior cerebellar peduncle to enter the cerebellum.
Finally, let’s draw our last pathway, the rostral spinoc-
erebellar tract. Indicate that it originates in the upper
limb. Th en, to draw the rostral spinocerebellar tract
course, show the central process of a peripheral nerve
synapse at the C4 to C8 spinal levels. Indicate that along
a poorly described course, fi bers project from the C4 to
C8 spinal levels to the cerebellum via the ipsilateral infe-
rior cerebellar peduncle.^2 , 4 – 12