What tract goes through the cerebral peduncle?

Tracts Through the Cerebral Peduncle

The corticospinal tract is the primary tract that passes through the cerebral peduncle, along with other important tracts including corticopontine, corticobulbar, and corticorubral tracts.

Anatomy of the Cerebral Peduncle

The cerebral peduncles are paired structures forming the ventral portion of the midbrain that connect the cerebrum with the pons. They contain several important white matter tracts:

Major Tracts in the Cerebral Peduncle

1. Corticospinal Tract

   • Primary motor pathway controlling voluntary movement
   • Located in the middle portion of the cerebral peduncle
   • The most clinically significant tract 1
   • Travels from the motor cortex through the posterior limb of the internal capsule, then through the cerebral peduncle before continuing to the spinal cord 2

2. Corticopontine Tracts

   • Divided into:
     • Frontopontine fibers (anterior portion)
     • Parietotemporopontine fibers (posterior portion)
   • Connect cerebral cortex to pontine nuclei 3

3. Corticobulbar Tract

   • Controls voluntary movements of cranial nerves
   • Located medial to the corticospinal tract

4. Corticorubral Tract

   • Projects to the red nucleus
   • Involved in motor coordination

Somatotopic Organization

The tracts within the cerebral peduncle follow a specific organization:

• In the cerebral peduncle, the corticospinal tract shows a transverse orientation
• Hand fibers are typically located medial to foot fibers in the cerebral peduncle 2
• This differs from the organization in the internal capsule, where tracts are organized along the long axis with hand fibers anterior to foot fibers 2

Clinical Significance

Lesions affecting the cerebral peduncle can result in various neurological deficits:

• The most common MRI finding in ALS is abnormal signal on T2/FLAIR or proton density-weighted images in the corticospinal tracts, frequently seen in the cerebral peduncles 1
• Pontine lesions can cause various syndromes including Millard-Gubler syndrome, Foville syndrome, locked-in syndrome, and facial colliculus syndrome 4
• Damage to the cerebral peduncle can cause contralateral hemiplegia or hemiparesis 1
• Lesions involving the cerebral peduncle can also affect the adjacent third nerve, resulting in ipsilateral oculomotor palsy 1

Imaging Considerations

• MRI is the preferred modality for evaluating the cerebral peduncle and associated tracts 1
• Diffusion tensor imaging (DTI) and tractography are particularly useful for visualizing the course and integrity of tracts through the cerebral peduncle 5, 2
• T2*-weighted imaging or susceptibility-weighted imaging can detect abnormal hypointensity in motor areas, which is highly sensitive and specific for ALS 1

Differential Diagnosis of Peduncular Lesions

• Multiple sclerosis: Lesions typically located at the periphery of the pons and cerebral peduncles 1
• Central pontine myelinolysis: Typically involves the central pontine white matter symmetrically 4
• Ischemic lesions: Usually involve the central pons along the transverse pontine fibers 1
• Tumors: Can affect the cerebral peduncle directly or through compression 3, 6
• Traumatic brain injury: Can cause injuries to the cerebellar peduncles resulting in poor coordination and balance problems 5

Understanding the anatomy and function of tracts passing through the cerebral peduncle is essential for accurate diagnosis and management of various neurological conditions affecting this critical region of the brain.