Morphological variability of the subcallosal area of man

Knowledge of morphology of human anterior cingulate and medial frontal cortex related to the knee of corpus callosum is important in the diagnostics and neurosurgical treatment. Neuroimaging studies did not provide a clear picture of this region, what is also caused by terminological inconsistencies. It is not always clear what is actually defined under the terms subcallosal area, subcallosal cingulate gyrus, subcallosal gyrus, subcallosal region, or subgenual prefrontal gyrus. Our study of subcallosal area provides morphological data useful for recent imaging studies.

Digital photographs (42 formaline fixed brains: 26 males, 16 females) were used in morphometry (surfaces and lengths) of subcallosal area. We defined all its boundaries: superoanterior, anterior, posterior, and inferior one. If anterior subcallosal sulcus, as anterior delineation of subcallosal area was absent, we used intercommissural line system.

Anterior subcallosal sulcus we found in 86.9% of cases. Its variations were classified into four types: Type 1-vertical or slightly oblique sulcus (most often type on right hemispheres-30.1%), Type 2-in form of letter C or inverted letter C (most often type on left hemispheres-42.9%), Type 3-sulcus in form of letter S or inverted letter S, and Type 4-sulcus not belonging to any previous type. Mean surface of subcallosal area was in males 2.65 cm(2) (right hemispheres), and on left 2.70 cm(2). In females on right it was 2.56 cm(2), and on left 2.55 cm(2). All measured values were not significantly different (left/right; males/females).

Accurate neuroanatomical localization requires exact determination of boundaries of subcallosal area. Therefore, standardized criteria were proposed for definition of subcallosal area.