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Topic

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Precentral gyrus

The precentral gyrus is a prominent convolution of the frontal lobe of the brain, located immediately anterior to the central sulcus. It serves as the primary motor cortex, responsible for voluntary motor control of the contralateral side of the body. The precentral gyrus plays a crucial role in executing finely controlled movements and is somatotopically organized, forming the motor homunculus. Its clinical and radiological identification is essential in both neurological assessment and pre-surgical planning.

Synonyms

  • Primary motor cortex

  • Brodmann area 4

  • Motor strip

  • Gyrus precentralis (Latin)

  • Precentral convolution

Arterial Supply

  • Supplied predominantly by branches of the middle cerebral artery (MCA)

  • The medial portion (paracentral lobule) receives blood from the anterior cerebral artery (ACA)

Venous Drainage

  • Drains mainly into the superior sagittal sinus via cortical veins

  • Some drainage may occur through the superior anastomotic vein (vein of Trolard)

  • Additional drainage via the inferior anastomotic vein (vein of Labbé), depending on the individual venous anatomy

Function

  • Primary area for voluntary movement initiation

  • Controls contralateral skeletal muscles via corticospinal tract fibers

  • Responsible for fine motor skills, especially of the face, hands, and limbs

  • Organized somatotopically (motor homunculus: face laterally, legs medially)

  • Critical in motor planning and execution

MRI Appearance

T1-weighted images:

  • Cortex: thin ribbon of intermediate signal (gray matter)

  • White matter: brighter signal deep to cortex

  • CSF in sulci: dark

T2-weighted images:

  • Cortex: thin ribbon of intermediate to slightly hyperintense signal compared to white matter

  • CSF in central sulcus: bright

  • Pathology (edema, gliosis): hyperintense

FLAIR:

  • Normal cortex: intermediate signal

  • CSF suppressed (dark), allowing clearer delineation of cortex and sulci

  • Pathology: bright lesions in demyelination, gliosis, or tumor infiltration

CT Appearance

Non-Contrast CT:

  • Cortex: slightly denser than white matter

  • Central sulcus: appears as a hypodense groove posterior to precentral gyrus

  • Acute ischemia: loss of gray-white matter differentiation in motor strip

Post-Contrast CT:

  • Normal cortex: does not enhance significantly

  • Tumors, infection, or inflammatory lesions: heterogeneous or focal enhancement

  • Cortical veins in central sulcus enhance normally and may serve as landmarks

MRI images

Precentral gyrus MRI 3T axial IMAGE

MRI images

Precentral gyrus MRI 3T SAGITTAL IMAGE

CT image

Precentral gyrus CT sagittal anatomy image -img-00001-00001