Topics

Topic

design image
Transverse temporal gyri

The transverse temporal gyri, also known as Heschl’s gyri, are short oblique convolutions located on the superior surface of the temporal lobe, within the Sylvian (lateral) fissure. These gyri form the primary auditory cortex (Brodmann areas 41 and 42), responsible for the initial cortical processing of sound.

Typically, there is one gyrus per hemisphere, though duplications or triplications are not uncommon. The left transverse temporal gyrus (dominant hemisphere) is more specialized for speech perception and language processing, while the right is associated with music, pitch, and nonverbal auditory interpretation.

Synonyms

  • Heschl’s gyrus

  • Transverse temporal convolution

  • Primary auditory cortex

Location and Structure

  • Anatomical position: On the superior surface of the temporal lobe, hidden within the lateral sulcus (Sylvian fissure).

  • Orientation: Runs obliquely from posterolateral to anteromedial direction across the superior temporal plane.

  • Boundaries:

    • Anteriorly: Transverse temporal sulcus and planum polare

    • Posteriorly: Planum temporale

    • Medially: Insular cortex (deep within lateral fissure)

    • Laterally: Superior temporal gyrus

  • Cortical composition: Brodmann areas 41 and 42, forming the primary and secondary auditory cortex.

Function

  • Auditory perception: Primary site for sound signal processing from both ears via the medial geniculate body.

  • Frequency and tone analysis: Encodes pitch, rhythm, and loudness.

  • Speech recognition: Left Heschl’s gyrus integrates phonetic and linguistic features.

  • Spatial localization: Helps determine the direction and origin of sound.

  • Neurocognitive role: Participates in language comprehension and music perception.

Clinical Significance

  • Lesions: Result in central hearing deficits, not total deafness, due to bilateral cortical representation.

  • Tumors: Low-grade gliomas and metastases may involve this region, leading to auditory processing deficits.

  • Epilepsy: Seizure foci in Heschl’s gyrus cause auditory hallucinations or distortions.

  • Stroke: Infarction in the middle cerebral artery (MCA) territory can impair auditory discrimination and speech comprehension.

  • Neurodegeneration: Atrophy or cortical thinning noted in Alzheimer’s disease and auditory processing disorders.

MRI Appearance

T1-weighted images:

  • Cortex: Intermediate gray signal intensity (gray matter)

  • White matter: Bright relative to cortex

  • CSF in Sylvian fissure: Dark (low signal)

  • Lesions:

    • Tumors or cortical dysplasia: Hypointense with loss of gray-white distinction

    • Hemorrhage (subacute): High signal from methemoglobin

    • Chronic infarction: Cortical thinning and sulcal widening

T2-weighted images:

  • Cortex: Intermediate to mildly bright signal

  • White matter: Slightly darker than cortex

  • CSF: Bright hyperintense

  • Lesions:

    • Edema, gliosis, or encephalomalacia: Bright hyperintense zones

    • Demyelination: Patchy hyperintensity in white matter deep to the gyrus

    • Chronic ischemia: Poor gray-white differentiation and volume loss

FLAIR (Fluid-Attenuated Inversion Recovery):

  • Normal cortex: Intermediate gray signal

  • White matter: Slightly darker

  • CSF: Suppressed (dark)

  • Pathology:

    • Gliosis, low-grade glioma, or cortical dysplasia: Bright hyperintense cortical thickening

    • Infarction or encephalitis: Focal hyperintensity involving auditory cortex

    • Cortical laminar necrosis: Layered hyperintensity along gyral crest

DWI (Diffusion-Weighted Imaging):

  • Normal cortex: Isointense to surrounding gray matter

  • Acute ischemia: Bright restricted diffusion with ADC hypointensity

  • Abscess or necrotic tumor: May show central restricted diffusion

  • Cytotoxic edema: Prominent restricted diffusion in early infarction

T1 Fat-Sat Post-Contrast:

  • Normal cortex: Minimal or no enhancement

  • Enhancing lesions:

    • High-grade glioma or metastasis: Irregular or nodular enhancement with surrounding edema

    • Meningioma: Homogeneous enhancement along superior temporal plane

    • Infection: Rim or patchy enhancement corresponding to FLAIR hyperintensity

    • Cortical dysplasia: May show faint gyral enhancement in active inflammation

CT Appearance

Non-Contrast CT:

  • Cortex: Intermediate attenuation, denser than white matter

  • White matter: Lower density relative to cortex

  • CSF: Hypodense in lateral fissure

  • Lesions:

    • Acute hemorrhage: Hyperdense within superior temporal plane

    • Infarction: Hypodense cortical-subcortical area with loss of gray-white differentiation

    • Calcified lesion (oligodendroglioma): Focal high-density deposit

Post-Contrast CT:

  • Normal cortex: Minimal or no enhancement

  • Enhancing lesions:

    • Meningioma: Strong, homogeneous enhancement along Sylvian fissure

    • Metastasis or glioma: Irregular or ring-like enhancement with perilesional hypodensity

    • Abscess: Peripheral enhancement with central low attenuation

MRI images

Transverse temporal gyri (Heschl) MRI 3T sagittal image

MRI images

Transverse temporal gyrus (Heschl) MRI 3T axial image

CT image

Transverse temporal gyri CT axial cross sectional anatomy radiology image -img-00001-00001