Study on persistent metopic sutures in south Indian adult dry skulls

J Jayarani

Abstract          Objective: The present study aims at the presence of persistent metopic sutures in south Indian adult skulls in various forms. The two halves of frontal bones are separated by the persistence of frontal suture in the adult skulls are called Metopism. The fusion of metopic suture starts at around 18 months after birth and is completed by 8-9 years of age. Methods: This study was carried on 120 south Indian adult dry skulls, collected from the museum of anatomy department in Tirunelveli Medical College, Tirunelveli. The skulls were inspected at the normal frontalis for the presence of the metopic suture. The sutures were classified as complete and incomplete. The incomplete ones were classified as linear type, ‘V’ shape and ‘U’ type. Results: 95 out of 120 skulls were found to have no metopic sutures. Complete metopic sutures extending from bregma to glabella was observed in 7 skulls (5.8%) (Figure 1) and the incomplete form was noted in 18 skulls (15%). Among incomplete type 9 skulls (7.5%) were revealed midline linear metopic sutures (Figure 2), 3 skulls (2.5%) showed V shaped metopic sutures. U shaped and inverted U shaped was noted in 2 skulls (1.7%) respectively. Each skull (0.8%) showed the Y shaped & H shaped type respectively. Conclusion: 25 (20.8%) out of 120 skulls showed the persistent metopic sutures in various forms with increase incidence of incomplete type (15%) with predominant linear(7.5%) variety. This work was done to contribute the scientific literature, providing Anatomical data and comparison of results with different authors.
Key words: fontanelle, nasion, bregma, metopism.

INTRODUCTION
Metopic sutures are vertical sutures between the two halves of the frontal bone, in the midline, from the anterior aspect of the anterior fontanelle to the nasion, this is obliterated by 6-8 years Weinzweig1. According to Hamilton2 the metopic suture disappears by the seventh year. In some skulls, there may be a partial or complete failure of this obliteration. When the metopic suture persists as a complete suture extending from the nasion to the anterior angle of the bregma, this condition is known as metopism. If the suture is not present throughout and occupies a small area between these two points, they are considered as incomplete metopic sutures. The obliteration of metopic suture is highly controversial and studied by various researchers. According to Romaneset et al3 the metopic suture closes by the fifth or sixth year. Piersol et al4 concluded that the metopic suture disappears by the end of the fourth year, leaving a faint trace at the lower end but Keith et al5 mentions that the metopic suture disappears at the end of the first year, or in the beginning of the second year of life. Warwick and Williams7 state that the frontal bones are separated by the metopic suture at birth and is usually obliterated by the eighth year. According to Del Soletal8, metopism can be due to abnormal growth of cranial bones, growth retardation, heredity, atavism, hydrocephalus, sexual influence, plagiocephaly, scaphocephaly, mechanical causes and hormonal dysfunction. Henry Gray10 postulated that the median suture usually disappears by about 8 years but may persist as metopic suture. The knowledge of the anatomy of the metopic suture is important because its permanence can be mistaken for a cranial fracture in radiological images, or even for the sagittal suture. It is also important for paleodemography and forensic medicine. In the present study, the objectives were to determine the incidence of persistent metopic sutures and its various forms on 120 south Indian adult dry skulls.
MATERIALS AND METHODS
This study was conducted on 120 south Indian adult dry skulls and inspected for persistence of metopic sutures. A suture which is found completely between the bregma and nasion is termed as the complete metopic suture or metopism. (Romanes GJ et al3 If it extends to a smaller distance either from the bregma or from the nasion, it is termed as incomplete type. The incomplete metopic sutures were sub divided into linear, ‘V’ shaped and ‘U’ shaped types. (Bilodi Ak6, Agarwal Bk et al14 Incomplete metopic suture was further divided into three groups according to their presence, in the lower part, in the upper part, and in the middle part of the frontal bone. (Pankaj R. Wadekar et al24, Nelima Pilli et al25, The incidences of complete and incomplete metopic sutures were calculated. The results were tabulated and compared with earlier authors.

RESULTS
In our study ninety five (79.2%) out of 120 skulls had neither complete nor incomplete metopic sutures. Metopic suture either in the form of complete or incomplete was found to be present in twenty five skulls (20.8%). Complete metopic suture (metopism) was found in seven skulls (5.8%) (Figure 1), and incomplete suture was observed in eighteen (15%) skulls (Table 1). Five different types of incomplete metopic sutures namely linear, 'U' shaped, 'V' shaped, H and Y were identified. Linear incomplete metopic suture was found in nine (7.5%) skulls, V shaped was in 3 (2.5%) skulls, U and inverted U shaped was noted in each 2 ( 1.7%) skulls and 'Y shaped, H shaped was observed in one (0.8%) skull respectively . Linear type of incomplete metopic suture was observed in the lower part of frontal bone in nine (7.5%) ((Figure 2 )skulls, but no suture remnant was found in the upper or middle part of frontal bone (Table 1).

CONCLUSION
The present study has shown the incidence of metopic suture in south Indian adult skulls as 20.8% and of metopism as 5.8%. The most common incomplete metopic suture was linear type which was 7.5% and located most commonly in the lower part of the frontal bone( 7.5%). On comparing with the results of earlier research workers in India, the incidence of metopism was found higher in skulls from south India. Persistence of Metopic suture is a useful guide in the identification of a person in medico legal aspect. Sometimes it may be easily misdiagnosed as fracture of frontal bone or even sagittal suture in radiological images. It is also important for forensic experts, neurosurgeons during frontal craniotomy, orthopedic surgeons, oromaxillofacial surgeons, ophthalmologists, ENT surgeons and others to know about metopism. Santhosh CS et al Metopic Suture.

REFERENCES