Topics

Topic

design image
Supramarginal gyrus

The supramarginal gyrus is a prominent cortical structure located in the inferior parietal lobule of the human brain, wrapping around the posterior end of the lateral sulcus (Sylvian fissure). It plays a key role in language perception, sensory integration, and spatial orientation. The supramarginal gyrus is closely associated with the angular gyrus, forming part of the parietal lobe and is integral in higher cognitive functions such as reading, writing, and emotional processing.

Synonyms

  • SMG

  • Brodmann area 40

  • Parietal operculum (in some contexts)

  • Part of inferior parietal lobule

Arterial Supply

  • Mainly supplied by the middle cerebral artery (MCA), specifically the inferior division branches.

  • Occasionally receives minor contributions from the anterior cerebral artery (ACA) in some individuals.

Venous Drainage

  • Drains primarily via the superior sagittal sinus through superficial cortical veins.

  • Additional drainage may occur through the superficial middle cerebral vein.

Function

  • Language perception and processing: Particularly phonological and reading tasks

  • Sensory integration: Combines tactile, auditory, and visual information

  • Spatial orientation: Helps in body position awareness and perception of space

  • Emotional empathy: Involved in understanding others’ emotions and intentions

  • Motor planning: Assists in coordination of fine motor skills and hand movements

MRI Appearance

T1-weighted images:

  • Cortex: Intermediate gray signal intensity

  • White matter: Bright compared to cortex

  • CSF: Dark (low signal)

  • Pathology:

    • Ischemic lesions: Cortical/subcortical hypointensity

    • Tumors: Low-to-intermediate signal mass with possible cortical expansion

    • Hemorrhage (subacute): Bright signal due to methemoglobin

T2-weighted images:

  • Cortex: Intermediate-to-bright signal

  • White matter: Slightly darker than cortex

  • CSF: Very bright

  • Pathology:

    • Edema, infarct, or gliosis: Hyperintense signal with loss of gray-white contrast

    • Tumors: Hyperintense with surrounding vasogenic edema

    • Chronic infarct: Irregular cortical thinning and gliotic hyperintensity

FLAIR (Fluid-Attenuated Inversion Recovery):

  • Normal cortex: Intermediate gray signal

  • White matter: Slightly darker

  • CSF: Suppressed (dark)

  • Pathology:

    • Cortical/subcortical infarction: Bright hyperintensity along the SMG region

    • Demyelination or gliosis: Patchy or confluent hyperintense areas

    • Low-grade glioma: Cortical thickening with subtle hyperintensity and preserved architecture

    • Encephalomalacia: Mixed bright and dark zones with sulcal prominence

DWI (Diffusion-Weighted Imaging):

  • Normal cortex: Isointense

  • Acute infarct: Bright (restricted diffusion) with corresponding ADC hypointensity

  • Abscess or necrotic tumor: May show variable restriction patterns depending on cellularity

  • Cytotoxic edema: Restricted diffusion in acute ischemia

  • Vasogenic edema: Typically no restriction (bright on T2/FLAIR but normal ADC)

T1 Fat-Sat Post-Contrast:

  • Normal cortex: Minimal to no enhancement

  • Enhancing lesions:

    • High-grade glioma or metastasis: Intense, heterogeneous enhancement with ring-like or nodular margins

    • Meningioma: Dural-based, homogeneous enhancement near the Sylvian fissure

    • Abscess: Peripheral rim enhancement with central non-enhancing core

    • Post-ischemic reperfusion: Gyral enhancement along the SMG cortex

CT Appearance

Non-Contrast CT:

  • Gray matter: Intermediate density, slightly denser than white matter

  • White matter: Lower attenuation

  • CSF: Hypodense

  • Pathology:

    • Acute infarct: Hypodense cortical-subcortical area with effacement of adjacent sulci

    • Hemorrhage: Hyperdense focus within SMG region

    • Calcified lesion: Hyperdense deposits (common in oligodendroglioma or metastasis)

    • Chronic infarct: Cortical atrophy and widening of lateral sulcus

Post-Contrast CT:

  • Normal cortex: No significant enhancement

  • Enhancing pathology:

    • Metastasis or glioma: Irregular or ring enhancement with surrounding hypodense edema

    • Meningioma: Intense, homogeneous enhancement adjacent to the inner skull table

    • Abscess or encephalitis: Peripheral or patchy gyral enhancement

    • Subacute infarct: Mild cortical enhancement due to reperfusion changes

MRI images

Supramarginal gyrus MRI 3t axial image

MRI images

Supramarginal gyrus MRI 3t sagittal image

CT image

Supramarginal gyrus CT sagittal cross sectional anatomy radiology image -img-00001-00001