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Calcarine spur

The calcarine spur is a prominent anatomical projection or bulge seen along the medial wall of the occipital horn of the lateral ventricle, caused by the deep indentation of the calcarine sulcus into the ventricular cavity. It is an important neuroanatomical landmark within the occipital lobe, closely associated with the primary visual cortex (Brodmann area 17). This structure is best appreciated on neuroimaging, particularly MRI and CT, and is relevant both for neuroanatomy and clinical radiology.

Synonyms

  • Calcar avis

  • Calcarine prominence

Arterial Supply

  • Primarily supplied by branches of the posterior cerebral artery (PCA), especially the calcarine branch.

  • Additional minor contributions may come from the parieto-occipital artery, another PCA branch.

Venous Drainage

  • Mainly drained by the calcarine vein.

  • Drains into the superior sagittal sinus and straight sinus via the internal cerebral veins.

Function

  • The calcarine spur itself is an anatomical landmark rather than a functional structure.

  • Closely related to the primary visual cortex (striate cortex), so its position is important in visual processing.

  • Used as a reference point in neuroimaging for localizing the visual cortex.

MRI Appearance

  • T2-weighted:

    • The calcarine spur appears as a well-defined protrusion into the occipital horn of the lateral ventricle, bordered by high-signal CSF.

    • The adjacent cortex (visual cortex) may be seen as a thin, slightly hyperintense ribbon compared to surrounding white matter.

  • T1-weighted:

    • The spur presents as a subtle indentation with hypointense CSF in the ventricle and intermediate signal cortex.

    • The surrounding white matter appears hyperintense compared to CSF.

  • FLAIR:

    • The calcarine spur appears similar to T2, but CSF is suppressed, so the indentation is less conspicuous.

    • Adjacent cortex and white matter maintain their respective signal intensities.

MRI images

Calcarine spur mri 3t sagittal image