Folia Morphol. Vol. 72, No. 1, pp. 10–16 DOI: 10.5603/FM.2013.0002 O R I G I N A L A R T I C L E Copyright © 2013 Via Medica ISSN 0015–5659 www.fm.viamedica.pl Morphology and digitally aided morphometry of the human paracentral lobule G. Spasojević1, S. Malobabić2, O. Pilipović-Spasojević3, N. Djukić Macut4, A. Maliković2 1Department of Anatomy, Faculty of Medicine, University of Banja Luka, Banja Luka, Republic of Srpska, Bosnia and Herzegovina 2Institute of Anatomy “Dr Niko Miljanić”, Faculty of Medicine, University of Belgrade, Belgrade, Serbia 3Department of Physical Medicine and Rehabilitation “Dr Miroslav Zotović”, Banja Luka, Republic of Srpska, Bosnia and Herzegovina 4Department of Anatomy, Faculty of Medicine, University of Kosovska Mitrovica (Priština), Serbia [Received 13 October 2012; Accepted 17 December 2012] The human paracentral lobule, the junction of the precentral and postcentral gyri at the medial hemispheric surface, contains several important functional regions, and its variable morphology requires exact morphological and quantita- tive data. In order to obtain precise data we investigated the morphology of the paracentral lobule and quantified its visible (extrasulcal) surface. This surface cor- responds to commonly used magnetic resonance imaging scout images. We stud- ied 84 hemispheres of adult persons (42 brains; 26 males and 16 females; 20– –65 years) fixed in neutral formalin for at least 4 weeks. The medial hemispheric surface was photographed at standard distance and each digital photo was ca- librated. Using the intercommissural line system (commissura anterior-commis- sura posterior or CA-CP line), we performed standardised measurements of the paracentral lobule. Exact determination of its boundaries and morphological types was followed by digital morphometry of its extrasulcal surface using AutoCAD software. We found two distinct morphological types of the human paracentral lobule: continuous type, which was predominant (95.2%), and rare segmented type (4.8%). In hemispheres with segmented cingulate sulcus we also found the short transitional lobulo-limbic gyrus (13.1%). The mean extrasulcal surface of the left paracentral lobule was significantly larger, both in males (left 6.79 cm2 vs. right 5.76 cm2) and in females (left 6.05 cm2 vs. right 5.16 cm2). However, even larger average surfaces in males were not significantly different than the same in females. Reported morphological and quantitative data will be useful during diagnostics and treatment of pathologies affecting the human paracen- tral lobule, and in further studies of its cytoarchitectonic and functional parcella- tions. (Folia Morphol 2013; 72, 1: 10–16) Key words: paracentral lobule, anatomy, encephalometry, human brain, left-right asymmetry, sex differences INTRODUCTION Terminologia Anatomica the term PCL (lobulus para- The human paracentral lobule (PCL), the convolu- centralis) was used twice and separately in order to tion at the medial hemispheric surface, connects me- indicate the anterior and posterior paracentral gyri [5]. dial portions of the precentral and postcentral gyri. In Morphology and boundaries of the PCL are determined Address for correspondence: Prof. Dr. S. Malobabić, Institute of Anatomy “Dr Niko Miljanić”, Faculty of Medicine, Dr Subotica 4/II, 11 000 Belgrade, Serbia, tel: 381 11 2684 259, fax: 381 11 2684 053, e-mail: [email protected] 10 G. Spasojević et al., Morphology and morphometry of human paracentral lobule by its limiting sulci, while its superior boundary corre- tics and functional studies, and enable the quantifi- sponds to the superior margin of the hemisphere. Cin- cation of genetic or environmental influences to the gulate sulcus is the crucial anatomical landmark that morphology of the human brain [1, 18]. The aims of bounds the PCL, either by its subfrontal segment (se- our study were to standardise the boundaries of the parates PCL and cingulate gyrus) or by its constantly human PCL, to define its morphological variability, present terminal branch (marginal ramus), which se- to quantify and investigate morphological left-right parates the PCL and precuneus. In cases of segment- asymmetries of the visible (exstrasulcal) surface of ed cingulate sulcus there is a short transitional lobulo- the PCL, as well as to estimate the potential mor- limbic gyrus, which may complicate definition of the phological sex differences. PCL boundaries [22]. In a functional MRI study Desi- kan et al. [3] delineated the PCL as the structure locat- MATERIALS AND METHODS ed posterior to the medial (superior) frontal gyrus (or This study included 84 brain hemispheres the precentral gyrus when visible), anterior to the pre- (42 brains) without visible pathological changes or neu- cuneus (or the postcentral gyri when visible), superior ropsychiatric history, from the collection of the Bel- to the cingulate gyrus, and inferior to the superior grade Institute of Anatomy “Dr Niko Miljanić”, which hemispheric border. There is also a report that the PCL were treated in accordance with the Ethical Princi- extends from the ascending and descending paracen- ples for Medical Research Involving Human Subjects tral sulci anteriorly, to the terminal “up-swing” of the [27]. Brains of adult persons of both sexes (26 males cingulate sulcus posteriorly [19]. Anterior to the PCL, and 16 females, aged between 20–65 years) were along the medial frontal gyrus, lies the supplementa- fixed by basilar suspension in neutral formalin for ry motor area (SMA), but its morphological boundary at least 4 weeks. After, midsagittal brain section was not defined in the literature. meninges were carefully removed and the medial The anterior two thirds of the PCL (medial surface hemispheric surface of each investigated brain was of the precentral gyrus or anterior paracentral gyrus) exposed. Medial hemispheric surfaces were photo- belong to Brodmann area 4 (BA4) [2]. The thick and graphed perpendicular to its plane at a standard agranular cortex of BA4 in the PCL is a part of the distance of 50 cm, using a digital camera of high primary motor area representing the muscles of the resolution (8 Mpx). Each digital photo was calibrat- leg and foot [4] and the urinary bladder [9], but the ed in accordance with the marked lines (X and Y) leg area of the primary motor cortex may extend more and further used for the standardised measurements caudal from the central sulcus toward the marginal of the PCL using AutoCAD software (AutoCAD 2009, ramus of cingulate sulcus [10]. The posterior third of version C.56.0, Autodesk Corporation). the PCL (medial surface of the postcentral gyrus or The intercommissural or the CA-CP line (here, the posterior paracentral gyrus) contains BA3, BA2, and X-axis along the sagittal plane, Fig. 1) was defined BA1, and inferior to these is the part of BA5 [2]. In as the line connecting the most prominent superior the PCL, the granular cortex of BA3, BA2, and BA1 point of the anterior commissure (CA) and the most reflects the primary somatosensory representation of prominent inferior point of the posterior commis- the leg and foot [4]. Interestingly, Penfield and Ro- sure (CP) [23], while the vertical line (here, the Y- berts [17] did not show any representation of the axis, Fig. 1) was defined as the perpendicular bisec- genital organs within the PCL in his famous schemes, tor (the line that lies under 90° to the middle point which is shown in numerous anatomical textbooks. of the intercommissural line) (Fig. 1). There is a viewpoint that morphological bound- Definition of the PCL boundaries (Fig. 1) aries of cytoarchitectonic areas do not correspond to brain sulci and gyri [2]. The portion of the sensori- The posterior boundary of the PCL was the con- motor cortex with the most interindividual variability stant marginal ramus of the cingulate sulcus. The is the extension of areas BA4 and BA3 onto the me- Inferior boundary of the PCL was the cingulate sul- sial face of the hemisphere in the PCL [19, 25]. There- cus. In cases of segmented sulcus cinguli, we defined fore, in the studies of the consistency of the PCL cy- this boundary by the horizontal X1 line (parallel to toarchitectonic borders across the brains with differ- the CA-CP line), which connects the main segments ent sulcal patterns, the brain selection must involve of the cingulate sulcus across the region of its miss- related sulcal or gyral morphology [6, 24]. ing part between the PCL and the cingulate gyrus. We investigated the morphology of the human The anterior boundary of the PCL was standardised PCL because morphological data improve diagnos- using the intercommissural or CA-CP line [23] due to 11 Folia Morphol., 2013, Vol. 72, No. 1 Figure 1. Boundaries of the paracentral lobule (PCL) in respect to the intercom- missural or CA-CP line; CA — commis- sura anterior; CP — commissura poste- rior; X — CA-CP line or axis along the sagittal plane; Y — vertical line inter- secting the middle of CA/CP line; Y1 — line that defines the anterior boundary of the PCL (see Methods section); SCe — central sulcus, medial part; SPc — pre- central sulcus; SCi-s — cingulate sul- cus, subfrontal part; SCi-m — cingulate sulcus, marginal part. Left hemisphere. Orientation: A — anterior; P — poste- rior; S — superior; I — inferior. a total absence of clear morphological landmarks (Fig. 1). most of the investigated brains (Fig. 2, Table 1). The Using this means of standardisation, the anterior segmented type of PCL was characterised by the pres- boundary of the PCL was defined as the vertical line ence of the constituent gyri, which were completely (line Y1 parallel to Y), extending from the medial end separated by the sulci (Fig. 3, Table 1). This type we of the precentral sulcus to the cingulate sulcus. The found in only 4.8% of hemispheres. surface located posterior to the Y1 line was referred Additionally, hemispheres with segmented cin- to as the PCL.