International Journal of Current Medical And Applied Sciences, 2015, December, 9(1),44-47. ORIGINAL RESEARCH ARTICLE INCA- Inter-Parietal Bones in Neurocranium of Human Adult Dry Skulls K. Arumugam 1 & A. Arunkumar 2 1Assistant Professor, Department of Anatomy, Tirunelveli Medical College, Tirunelveli.Tamil Nadu, India. 2Tutor, Andamon Nicobar Island of Institute of Medical Sciences, Andaman. India. ---------------------------------------------------------------------------------------------------------------------------------------------------- Abstract: Skull means the skeleton of the head including mandible and calvaria means skull after the bones of the face have been removed. In this the word skull is frequently used instead of cranium as a matter of convenience and common usage Objectives: To determine the incidence and type of INCA variants in human adult dry skull. Materials and Methods In this study, 100 human dried skulls were analyzed. All the skulls were taken from the Institute of Anatomy, Madras Medical College, Chennai. Results: Gross incidence of INCA was found to be 2%. The INCA occurred in single. Conclusion: This study gives idea of INCA regarding gross incidence, number and type. This knowledge is useful for neurosurgeons, anthropologists and radiologists. Key words: Neurocranium, INCA bone, Sutural bones. Introduction: According to the catalogues of craniological collections, fontanelle and paired posterior-lateral fontanelle. skull means the skeleton of the head including These fontanelles allows the expansion of the foetal mandible and calvaria means skull after the bones of head to accommodate the rapid enlargement of brain the face have been removed. In this the word skull is which take place during postnatal life. During frequently used instead of cranium as a matter of parturition the fontanelles also help in moulding of the convenience and common usage [2]. foetal head by overlapping the skull bones without any Skull consists of two parts namely neurocranium and compression to the brain. All the fontanelles except splenchnocranium (Viscerocranium). Nerucranium anterior fontanelles are closed within 3 or 4 months covers and protects the brain. This is developed from after birth. The anterior fontanelle is usually closed at the mesenchymal condensation around the brain. The 18 months after birth. bones forming the vault and the side wall of the skull Inter parietal bones are due to the failure of fusion of are ossified directly from the membrane. So they are primary and secondary ossification centre’s of occipital called as membranous or dermal bones. This consists of bone. These INCA bones may give a false appearance of frontal bone including orbital cavity, the parietal, fracture on X-rays. Such bones produce complication squamous part of temporal bone and interparietal part during burrhole surgeries. The presence of INCA may of occipital bone. At birth unossified membranous gaps be used as evidence for familial identity in medico legal found at the angles of the parietal bones. These cases. Due to clinical implications, information of unossified membranes known as fontanelles. These are presence of INCA bones, their incidence is essential to six in number. They are unpaired anterior fontanelle, clinicians. unpaired posterior fontanelle, paired anterolateral Address for correspondence: Dr. K. Arumugam, Access this Article Online Assistant Professor, Department of Anatomy, Website: Tirunelveli Medical College, Tirunelveli, Tamil Nadu, India. www.ijcmaas.com Email: [email protected] How to cite this article: Subject: K. Arumugam & A. Arunkumar ; INCA- Inter-Parietal Bones in Medical Sciences Neurocranium of Human Adult Dry Skulls . International Journal of current Medical and Applied sciences; 2015, 9(1), 44--47. Quick Response Code . IJCMAAS,E-ISSN:2321-9335,P-ISSN:2321-9327. Page | 44 K. Arumugam & A. Arunkumar Materials & Methods: • Very old skulls with obliterated suture The present study was conducted in the Institute of The skulls were observed with naked eye and took Anatomy, Madras Medical College, Chennai. photographs for further analysis. Hundred human adult dry skulls of unknown sex In the present study we followed Hauser & De Stefano without any gross pathology or abnormality were (1989) [7] and Kadanoff & Mutafov (1986) [4] for used for the study. All the skulls included in the study criteria and nomenclatures of the variants of the Inca were adults as evidenced by the eruption of third bones. molar teeth. According to Kandanoff & Mutafov (1968)[4] the INCA Inclusion criteria : bones are classified as • Adult human dry skull irrespective of sex. 1 Single INCA • Calvarias intact. 2 Biparite • Third molar tooth erupted. 3 Tirparite • Sutures well defined. 4 Multiparite (Fig 1-4). Exclusion criteria: • Damaged skulls. • Newborn, infants and children skulls. Fig 1 Single INCA bone Fig 2: Biparite INCA bone Fig 3: Tirparite INCA bone Fig 4: Multiparite INCA bone Fig; 5 Types of INCA Fig; 6: single INCA bone Fig; 7 : single INCA bone Hauser & De Stefano (1989) [7] described the various patterns of the OS INCA bones. They classified as Type I to V. Fig 5 depicts schematic presentation of various patterns of the Inca bones. Results: Out of total 100 skulls, it was noted that only two skulls had INCA ossicles. So gross incidence reported as 2% in this study (table 1) . Table 1: Number of INCA ossicles observed in this study INCA ossicles Number of skulls Percentage Present 2 2% Absent 98 98% Out of two skulls which had INCA ossicles, all were single median type. No other types were observed in this study (Table 2). Logic Publications @ 2015, IJCMAAS, E-ISSN: 2321-9335,P-ISSN:2321-9327. Logic Publications @ 2015, IJCMAAS, E-ISSN: 2321-9335,P-ISSN:2321-9327. Table 2: Type of INCA ossicles observed in this study Type No out of 100 skulls % Single median 2 2 Biparite 0 0 Triparite 0 0 Multiparite 0 0 Discussion: In the present study Inca ossicles were reported as 2%.Avery high incidence about 27.7% reported in pre Hispanic skulls dated between 300-1200AC. Table 4: Different study’s findings of Skulls, Inca & Incidence. Name of the study Total no skulls No of Inca Incidence Berry et al(1967) [3] - - 2.9 -4.6% Srivastavo et al (1977) [5] 620 3 0.8% Yucel et al (1998) [9] 544 15 2.8% Saxena et al (1988) [6] 40 1 2.5% Marathe et al (2010) [12] 380 5 1.315 Vivek nirmale et al (2012) 148 6 4.054% [13] Present study 100 2 2% Berry et al [3] reported 2.9 to 4.6% incidence in American population of south west coast. Tsunchiko et al [10] study showed the low incidence of Inca ossicles in Ascians as compared to new world population. Srivastavo HC [5] in a study of 620 skulls found complete separate inter parietal bone in 3 skulls with an incidence of 0.8%. Yucel et al [9] in a study of 544 skulls found the incidence of Inca in 2.8%. Keith [1] stated that an occurrence of separate inter parietal bone in man is as extremely rare anomaly. He observed that phylogenitacally the inter parietal bones fuses with parietals in marsupials while in rodents, they fuses with the both the occipital and parietal bones. But sometimes inter parietal bone seen as separate bone as a variant in man. Saxena et al [6] in a study of 40 Nigerian skulls found the presence of inter parietal bone in only one skull with an incidence 2.5%.Marathe et al [12] found the presence of Inca bone in 5 out of 380 skulls from central India with an incidence of 1.31%. Vivek Nirmale et al reported that out of 148 skulls 6 skulls had Inca bone with the incidence of 4.05%. Table 5: Type of Inca Different studies: Type of Inca Kandanoff & Mutafov et al Vivek Nirmale et al Present study (1968) [4] study (2012) [13] study Median 1.74% 0.675% 2% Biparite 0.82% 0.675% - Triparite 0.14% - - Multiparite 0.14% 0.675 - Partial - 2.0270% - Type of the Inca Based on the Kandanoff & Mutafov [4[ method, present study found 2% of single median Inca ossicle. But Vivek Nirmale et al (2012) [13] reported varies types of Inca as follows Median – 1.74%, Bi parite 0.82%, Triparite 0.14%, Multiparite – 0.14% Table 6 : Type of Inca in Different studies: Type of Inca Vivek Nirmale et al (2012) [13] Present study Type I 0.675% 2% Type II 0.675% - Type III 0.675% - TypeIV 1.351% - Type V 0.675% - According to Hauser & De Stefano [7] method, present study only Type I was reported as 2%. Vivek Nirmale et al (2012) [13] reported varies types as follows. Type I – 0.675%, Type II – 0.675%, Type III- 0.675%, Type IV- 1.351% & Type V- 0.675% (Table 6). International Journal of Current Medical And Applied Sciences [IJCMAAS], Volume : 9, Issue: 1 . Page | 46 K. Arumugam & A. Arunkumar Conclusion knochen fortsatze des Hirnschadels be in Thus from this study it can be concluded that the Menschen,Anthropologischer Anzeiger, 1968 31: pg 28-39 incidence of Inca bone is variable in different 5. Srivastavo HC Development of ossification centres in populations. These indicate that there may be natural the squamous portion of the occipital bone in man evolutionary, embryological and genetically changes. J.Anat 1977; 124: pg 834-839 The knowledge of the incidence, number and types of 6. Saxena SK, Chowdhary DS,Jain SP. Inter parietal Inca ossicles in human skulls may be useful to bone in Nigerian skulls J.Anatomy 1988;144:pg 235- neurosurgeons, orthopedicians, radiologists and 237 forensic experts. 7. Hauser G, DeStefano GF Epigenetic Varients Of The Human Skull.stuttgant: E schweizarbatt 1989. th Acknowledgements: 8. Gray’s Anatomy 38 ed London Churchill Livingstone 1995 The Skulls pg 583-606 I wish to express exquisite thankfulness and gratitude 9. Yucel F, Egllmez H, Akgma Z A study of the inter to my most respected teacher and guide Dr.