Calcar avis
Citation, DOI, disclosures and article data
At the time the article was created Pradeep J. Gamage had no recorded disclosures.
View Pradeep J. Gamage's current disclosuresAt the time the article was last revised Frank Gaillard had the following disclosures:
- Biogen Australia Pty Ltd, Investigator-Initiated Research Grant for CAD software in multiple sclerosis: finished Oct 2021 (past)
These were assessed during peer review and were determined to not be relevant to the changes that were made.
View Frank Gaillard's current disclosures- Hippocampus minor
Calcar avis is an elevation of white matter projecting from the medial wall of the occipital horn of the lateral ventricle. It is variably conspicuous, depending on how deep the calcarine sulcus is.
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Gross anatomy
The calcar avis is located on the medial wall of the occipital horn, near the junction with the trigone of the lateral ventricles. It is formed by white matter separating the ventricle from the calcarine sulcus and, thus, is more prominent if the sulcus is deep 1-3. It is located below the bulb of the occipital horn, formed by forceps major, and above the collateral eminence, formed by white matter separating the ventricle from the collateral sulcus 2.
Radiographic features
Ultrasound
In a coronal plane of the neonatal brain, the calcar avis can mimic an intraventricular hemorrhage. Continuation of it as an echogenic fissure as the calcarine fissure and normal vascularity aids in differentiating the calcar avis from a blood clot 1.
CT
On axial reconstructions, the calcar avis may mimic intraventricular hemorrhage in the occipital horns. This structure can also mimic grey matter heterotopia and schizencephaly ref.
History and etymology
The calcar avis was previously known as the hippocampus minor (in contrast to hippocampus major, now simply the hippocampus) 1.
References
- 1. Owen C, Howard A, Binder D. Hippocampus Minor, Calcar Avis, and the Huxley-Owen Debate. Neurosurgery. 2009;65(6):1098-105. doi:10.1227/01.neu.0000359535.84445.0b - Pubmed
- 2. Flores L. Occipital Lobe Morphological Anatomy: Anatomical and Surgical Aspects. Arq Neuro-Psiquiatr. 2002;60(3A):566-71. doi:10.1590/s0004-282x2002000400010
- 3. Savas R & Sener R. Deep Calcarine Sulcus and Prominent Calcar Avis. J Neuroradiol. 1998;25(2):144-6. - Pubmed
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