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Topic

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Amygdala

he amygdala is an almond-shaped cluster of nuclei located deep within the temporal lobes of the brain, forming an essential part of the limbic system. It plays a crucial role in processing emotions, behavior, and memory, particularly those related to fear and pleasure. Its central position and extensive connections allow it to influence both autonomic responses and higher cognitive processes.

Synonyms

  • Amygdaloid body

  • Amygdaloid nucleus

Arterial Supply

  • Primarily supplied by the anterior choroidal artery (branch of the internal carotid artery).

  • Additional supply from the middle cerebral artery (especially the temporal branches).

  • Minor contributions from the posterior cerebral artery (via anterior temporal branches).

Venous Drainage

  • Drains mainly into the inferior ventricular vein and the basal vein of Rosenthal.

  • Additional drainage into the deep middle cerebral vein.

Function

  • Emotion processing: Central in mediating emotional responses, especially fear, aggression, and pleasure.

  • Memory: Key role in encoding and storing emotional memories.

  • Autonomic control: Influences autonomic and endocrine responses to emotional stimuli.

  • Social interaction: Involved in recognition of emotions in others and modulation of social behavior.

MRI Appearance

T1-weighted images:

  • Normal amygdala: Intermediate gray signal, slightly darker than cortical gray matter

  • White matter: Brighter than amygdala

  • CSF: Dark (low signal)

  • Pathology:

    • Sclerosis or atrophy: Volume loss and low signal intensity

    • Tumor or inflammation: Hypointense to isointense mass with distortion of adjacent hippocampus

    • Hemorrhage (subacute): Focal high signal due to methemoglobin deposition

T2-weighted images:

  • Normal amygdala: Intermediate-to-bright signal, distinguishable from darker surrounding white matter

  • CSF: Bright

  • Pathology:

    • Edema or gliosis: Hyperintense signal

    • Tumor: Heterogeneous hyperintensity with mass effect

    • Sclerosis: Subtle increased signal intensity with reduced size

FLAIR (Fluid-Attenuated Inversion Recovery):

  • Normal: Intermediate gray signal

  • CSF: Dark

  • Pathology:

    • Gliosis or edema: Bright hyperintense signal

    • Low-grade glioma or cortical dysplasia: Subtle cortical thickening and hyperintensity

    • Infectious or autoimmune limbic encephalitis: Bilateral asymmetric hyperintensity in amygdala and hippocampus

DWI (Diffusion-Weighted Imaging):

  • Normal: Isointense to gray matter

  • Acute infarct: Restricted diffusion with bright DWI and low ADC

  • Tumor or inflammation: Variable diffusion restriction depending on cellularity

  • Herpes simplex encephalitis: Marked restricted diffusion and swelling of amygdala and medial temporal lobe

T1 Fat-Sat Post-Contrast:

  • Normal: No significant enhancement

  • Pathology:

    • Tumors: Focal or heterogeneous enhancement (especially in high-grade gliomas or metastases)

    • Limbic encephalitis: Mild to moderate enhancement of amygdala and adjacent hippocampal structures

    • Infection or granulomatous disease: Irregular or nodular enhancement

    • Postictal state: May show transient enhancement with cortical swelling

CT Appearance

Non-Contrast CT:

  • Normal amygdala: Poorly differentiated from adjacent gray matter; appears as part of medial temporal density

  • Gray matter: Slightly denser than surrounding white matter

  • Pathology:

    • Acute hemorrhage: Hyperdense region in anteromedial temporal lobe

    • Mass lesion: Hypodense or isodense area with effacement of adjacent sulci

    • Calcification: May occur in tumors (oligodendroglioma, ganglioglioma)

    • Atrophy: Enlarged temporal horn and loss of medial temporal bulk

Post-Contrast CT:

  • Normal amygdala: Minimal enhancement

  • Pathology:

    • Neoplasm: Variable contrast enhancement—homogeneous in low-grade, heterogeneous in high-grade lesions

    • Infective lesions (herpes, abscess): Peripheral or patchy enhancement

    • Inflammation or limbic encephalitis: Mild gyral enhancement and adjacent cortical swelling

    • Metastasis: Ring or nodular enhancement with vasogenic edema

MRI images

Amygdala mri 3t coronal image

MRI images

Amygdalohippocampal area mri 3t coronal image

MRI images

Amygdaloid body MRI sagittal cross sectional anatomy radiology image

CT image

Amygdaloid body CT axial cross sectional anatomy radiology image