Cerebral peduncle

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Cerebral peduncles (pedunculus cerebri)

The cerebral peduncles are two bundles located at the front of the midbrain that connect the cerebrum to the brainstem. They arise from the ventral part of the brainstem and carry major motor and sensory pathways between the cerebrum and other brain regions. They are also called the basis pedunculi, and the large front bundle is known as the cerebral crus (crus cerebri).

What they include
- The peduncles contain key brain pathways, including the corticospinal, corticopontine, and corticobulbar tracts.
- Descending motor fibers from the internal capsule pass through the midbrain as part of the peduncles.
- The midbrain region that forms the peduncles includes the tegmentum, crus cerebri, and pretectum.

Organization and connections
- The corticopontine fibers are found in the outer and inner thirds of the peduncle and carry input from the cortex to the pontine nuclei.
- The corticobulbar and corticospinal fibers are mainly in the middle third of the peduncle.
- The peduncles are located on either side of the midline and are the frontmost part of the midbrain, connecting the midbrain to the thalamic nuclei and the cerebrum.

Cranial nerves
- The oculomotor nerve (CN III) appears ventrally between the two peduncles in the interpeduncular fossa.
- The trochlear nerve (CN IV) winds around the lowest part of the cerebral peduncle.

Functions and effects of damage
- These pathways help refine voluntary movements, support the learning of new motor skills, and convert proprioceptive information into balance and posture.
- Damage to the cerebral peduncles can lead to uncoordinated movements, imbalance, and impaired proprioception.