The central sulcus (of Rolando) is a very important landmark in both anatomical and functional neuroanatomy.
The central sulcus separates the frontal lobe from the parietal lobe, and more specifically separates the primary motor cortex anteriorly from the primary somatosensory cortex posteriorly .
A number of landmarks and signs have been identified as being variably useful in identifying the central sulcus on cross-sectional imaging . Although various individuals and publications expound the virtues of one or more of these signs, not all signs are present in any given patient. In practice, one should use as many of them as possible to identify the central sulcus, which is possible to do with certainty in the vast majority of cases, unless there are serious congenital sulcation anomalies, prior surgery, or distorting masses. The most well-known signs include the following:
- midline sulcus sign: the central sulcus is the longest sulcus in a roughly coronal plane intersecting the interhemispheric fissure
- upper T sign: the superior frontal sulcus intersects the precentral sulcus in a "T" junction. The central sulcus is the next posterior sulcus.
- L sign: the superior frontal gyrus intersects precentral gyrus in an "L" junction. The central sulcus is immediately posterior.
- lower T sign: the inferior frontal sulcus terminates posteriorly in the precentral sulcus in a "T" junction. The central sulcus is the next posterior sulcus.
- M sign: the inferior frontal gyrus has a characteristic "M" configuration and terminates posteriorly in the precentral gyrus. The central sulcus is immediately posterior.
- bracket sign: the marginal sulcus is visible immediately posterior to the central sulcus, and is easily identifiable of sagittal paramedian images as the continuation of the cingulate sulcus
- thin postcentral gyrus sign: the postcentral gyrus is thinner than the precentral gyrus
- sigmoidal hook (handknob, omega) sign: the precentral gyrus bulges posteriorly at the hand motor area
- bifid postcentral gyrus sign: the postcentral gyrus is split medially by the pars marginalis of the cingulate sulcus
- U sign: the most inferolateral extent of the central sulcus is capped by a U-shaped gyrus – the subcentral gyrus – which abuts the lateral fissure
Several central sulcus localizing signs are specific to MRI signal characteristics:
- T1: white gray sign: gray-white contrast around the central sulcus is reduced compared to precentral and postcentral sulci
- T2: single or multiple bands of low intensity in the primary motor cortex, depending on pulse sequence and magnet strength
- FLAIR: low signal intensity of perirolandic cortex
- DWI: invisible cortex sign: just above the subcentral gyrus, the cortex deep to the inferolateral central sulcus appears isointense to adjacent white matter
In cases where anatomy is uncertain, or it is of critical importance to confirm the anatomy, then functional MRI can be performed, particularly aimed at identifying the hand motor cortex.
History and etymology
The Rolandic sulcus (as it once was) was named after the Italian anatomist, Luigi Rolando (1773-1831) .