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Paracentral lobule

The paracentral lobule is a cortical region located on the medial surface of the cerebral hemisphere, forming the continuation of the precentral and postcentral gyri around the upper end of the central sulcus. It contains the cortical representations for motor and sensory functions of the contralateral lower limb and plays a crucial role in voluntary movement, sensation, and sphincter control.

It is of major clinical importance in cerebrovascular disease, neurodegenerative disorders, epilepsy, and functional neuroimaging.

Synonyms

  • Medial continuation of precentral and postcentral gyri

  • Lower limb sensorimotor cortex (medial surface)

Location

  • Located on the medial surface of the cerebral hemisphere

  • Surrounds the medial end of the central sulcus

  • Anterior half lies in the frontal lobe

  • Posterior half lies in the parietal lobe

  • Superior to the cingulate sulcus

  • Inferior to the superomedial border of the hemisphere

  • Forms part of the medial sensorimotor cortex

Anatomical components

  • Anterior portion:

    • Medial continuation of the precentral gyrus

    • Primary motor cortex (lower limb area)

  • Posterior portion:

    • Medial continuation of the postcentral gyrus

    • Primary somatosensory cortex (lower limb area)

  • Cortical layers:

    • Well-developed pyramidal layer anteriorly

    • Prominent granular layer posteriorly

Relations

Superiorly:

  • Superomedial border of the cerebral hemisphere

Inferiorly:

  • Cingulate sulcus

  • Cingulate gyrus

Anteriorly:

  • Medial frontal gyrus

Posteriorly:

  • Precuneus

Laterally:

  • Blends with the precentral and postcentral gyri on the superolateral surface

Functional representation

  • Primary motor cortex (anterior paracentral lobule):

    • Voluntary motor control of the contralateral lower limb

  • Primary somatosensory cortex (posterior paracentral lobule):

    • Sensory perception from the contralateral lower limb

  • Pelvic floor and sphincter control:

    • Cortical regulation of bladder and bowel function

Function

  • Motor control: Initiation and execution of voluntary movements of the contralateral leg and foot

  • Sensory processing: Perception of touch, pain, temperature, and proprioception from the contralateral lower limb

  • Autonomic integration: Involvement in voluntary control of micturition and defecation

  • Postural regulation: Contributes to balance and gait coordination

MRI appearance

T1-weighted images:

  • Normal cortex: Intermediate gray-matter signal with clear gray–white differentiation

  • Central sulcus landmark: Clearly visualized at the medial surface

T2-weighted images:

  • Normal cortex: Intermediate-to-slightly hyperintense gray matter

  • White matter: Relatively hypointense

FLAIR:

  • Normal: Uniform cortical signal with suppressed CSF in adjacent sulci

  • Pathology: Hyperintense cortical or subcortical lesions in ischemia or demyelination

Diffusion-weighted imaging (DWI):

  • Normal: No diffusion restriction

Post-contrast T1-weighted images:

  • Normal: No significant enhancement

CT appearance

Non-contrast CT:

  • Normal: Gray–white matter differentiation preserved

Post-contrast CT:

  • Normal: Minimal enhancement

MRI image

MRI Paracentral gyrus sagittal anatomy image -img-00000-00000