Transverse Temporal Sulcus

The Transverse Temporal Sulcus (TTS) is the posterior limit of the transverse gyrus of Heschel. It is hidden on the superior surface of the superior temporal gyrus covered by the fronto-parietal operculum. It cannot be seen unless the frontal and parietal lobes are removed to expose the superior surface of the temporal lobe. Even when stripping the hemispheric surface to the midcortical level, or even to the gray/white junction, it is difficult to see this region clearly. However, it is an important sulcus given that it constitutes the boundary of the primary auditory cortex. It has a course from postero-mesial to antero-lateral.

The best approach to tracing the TTS is to start with a coronal slice, at the level of poterior thalamus and identify, in the temporal lobe, a mesial hump (1), which is also clearly seen in a parasagital slice (2). Drop here the beginning of the curve and see where it falls in the surface view (3, detail in 4). Move laterally and drop the terminal point (5, detail in 6). The sulcus ends most of the time on the superior surface of the temporal lobe, but, occasionally it may reach the lateral surface (7 and 8). Once again, because of consistency among curves for the purpose of alignment, it should always be ended at the edge of the superior surface (9 and 10).

Looking at the marked sulcus on the gray/white junction surface (11) permits a better overall view. The coronal (12), parasagital (13), and axial (14) slices continue to show the sulcus very clearly.

The TTS can be a double sulcus. In that case trace the most anterior sulcus.

USC Biomedical Imaging Research Lab © 2009, designed by Dimitrios Pantazis