| Summary: | Faculty of Sciences
School of Anatomical Sciences
0202721m
slyviakamanzi@yahoo.com === This study primarily seeks to confirm two systems of classifying the sulci of the frontal
operculum1 (F3): the radiologically derived system of Ebeling et al (1989) involving four
Types of Sulcal Connections, and the anatomical classification of the anterior rami of the
lateral fissure, involving three patterns. Sulcal- and intersulcal- lengths are also considered.
The sample consisted of 220 cadaveric hemispheres; 65 of which were whole brains
(control category); and 90 consisting of equal numbers of separate right- and lefthemispheres
(case category). Specimens were orientated by examining relevant features of:
the lateral fissure; the postcentral sulcus; and the central fissure. Features of the remaining
boundary sulci (precentral sulcus / sulci, and inferior frontal sulcus) of F3 were also
considered. The focus was on examining the: frequency of occurrence, shape, and
connections of the sulci of the F3. The sulci of F3 were designated as: major sulci [anterior
ascending (AAR)- and anterior horizontal (AHR)- rami, and stem of the anterior rami when
present); and accessory sulci (sulci of the –pars opercularis and –pars triangularis). Sulcal
lengths were measured using thread, with needles as anchors. Intersulcal lengths were
recorded as straight-line distances between parallel pins inserted into the sulci of the
frontoparietal operculum. Specimens fixed outside the cranial cavity were excluded from
measurement. The reliability of the data was monitored, by repeating the observations.
The two systems of classification were broadly confirmed. The criteria for the Types of
Sulcal Connections were modified in view of the findings on double precentral sulci and
the connections of the opercular sulcus (which occurred as either one or as two sulci). A
sulcus of the pars triangularis (which occurred as either one, two, or as three sulci) was
found to be a useful landmark. The Chi-square test was applied to the data in the two
systems of classification. There were no significant interhemispheric differences with
respect to the incidences of: Types 1-4 of Sulcal Connections, or Patterns of the Anterior
Rami (I, Y, and VU). Sulcal lengths were similar to that reported by Ono et al (1990). The
Student t-test was applied to sample sizes 18 and above. No significant interhemispheric
differences, in the lengths of the sulci that were considered, were found. A significant
1 The definition of the frontal operculum as the inferior frontal gyrus only, is used for the purposes of
this study. The frontal operculum may also be abbreviated as F3.
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difference was found in two instances when comparing the case- and control- categories.
Intersulcal distances are reported on in the frontal- and frontoparietal- operculum.
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