Mammillary bodies are paired, small, round structures on the inferior surface of the hypothalamus, part of the limbic system.

• Situated just posterior to the infundibulum (pituitary stalk) and anterior to the midbrain.
• They are gray matter nuclei and form a key relay station in memory circuits.

Connections

Circuit of Papez:

• Thus, mammillary bodies are central to the Papez circuit, involved in episodic memory and emotional processing.

Physiology / Function

• Role in learning and memory, especially recollective memory.
• Lesions here disrupt the hippocampal–diencephalic memory pathway, leading to amnesia.

Pathology

| Wernicke’s encephalopathy (acute thiamine deficiency) | • Symmetrical swelling and T2/FLAIR hyperintensity of mammillary bodies, medial thalami, periaqueductal gray. • Clinical triad: ophthalmoplegia, ataxia, confusion. | | --- | --- | | Korsakoff syndrome (chronic thiamine deficiency) | • Mammillary body atrophy on MRI. • Severe anterograde and retrograde amnesia, confabulation. | | Tumors / lesions | Hypothalamic gliomas, craniopharyngiomas, germinomas may involve mammillary region. | | Neurodegenerative diseases | Alzheimer’s disease – mammillary body volume reduction correlates with memory impairment. |

Hypoxemic ischmic injury:

![Mammillary body scoring on the sagittal plane of T1 weighted images: Normal (a), equivocal (b), and abnormal (c). Left and right Mammillothalamic tract (MTT) (d) and fornix (e) shown. Right MTT had increased radial diffusivity in children cooled for HIE (cases) with abnormal mammillary bodies than cases with normal or equivocal mammillary bodies and higher than controls. Left fornix had lower fractional anisotropy in cases with abnormal mammillary bodies than controls.

Spencer, A. P. C. et al. Mammillary body abnormalities and cognitive outcomes in children cooled for neonatal encephalopathy. Dev. Med. Child Neurol. 65, 792–802 (2023). Chakkarapani, E., de Vries, L.S., Ferriero, D.M. et al. Neonatal encephalopathy and hypoxic-ischemic encephalopathy: the state of the art. Pediatr Res (2025). https://doi.org/10.1038/s41390-025-03986-2

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Mammillary body scoring on the sagittal plane of T1 weighted images: Normal (a), equivocal (b), and abnormal (c). Left and right Mammillothalamic tract (MTT) (d) and fornix (e) shown. Right MTT had increased radial diffusivity in children cooled for HIE (cases) with abnormal mammillary bodies than cases with normal or equivocal mammillary bodies and higher than controls. Left fornix had lower fractional anisotropy in cases with abnormal mammillary bodies than controls.

Spencer, A. P. C. et al. Mammillary body abnormalities and cognitive outcomes in children cooled for neonatal encephalopathy. Dev. Med. Child Neurol. 65, 792–802 (2023). Chakkarapani, E., de Vries, L.S., Ferriero, D.M. et al. Neonatal encephalopathy and hypoxic-ischemic encephalopathy: the state of the art. Pediatr Res (2025). https://doi.org/10.1038/s41390-025-03986-2

Radiological Features

• Normal MRI: Small paired round structures posterior to pituitary stalk; isointense to gray matter.