Metopism: Its Prevalence and Morphometry in Adult Nigerian Dry Skulls

Background: Metopic suture also known as the frontal, interfrontal, or median frontal suture is formed in the midline at the meeting of the two halves of the frontal bone. Normally it gets obliterated by early childhood, but in some cases, it persists and is described as metopism. This study is aimed at investigating metopism prevalence in dry Nigerian skull.  Methods: This study was conducted on ninety-six (65 males and 31 females) adult Nigerian dry skulls from 5 selected Universities in the Southern part of Nigeria. Metopic suture (metopism) was considered to be complete when it continued uninterruptedly from the nasion to the bregma and incomplete when it was not present over its entire length. The incomplete metopic sutures were further classified into shapes. Results: Metopism was observed in 31 skulls (32.3%) of which 22 (21.9%) were males and 9 (9.4%) were females. Complete metopic suture was found in only 1 skull (1.04%) and incomplete metopic suture was seen in 30 skulls (31.25%). Among the incomplete ones, linear shape metopic suture was the most common in 16 skulls (16.67%). 7 (7.29%) were V-shaped metopic suture and another 7 (7.29%) were double-type metopic suture. Prevelence of metopic suture was slightly higher in males than in females. However, there was no statistical level of association with respect to sexual dimorphism. Conclusion: The prevalence and morphometry of metopism in the 96 adult Nigerian skulls studied, revealed complete metopism to be 1.04% with a length of 127.0mm as against incomplete metopism of 31.25% making a total prevalence of 32.29%. The prevalence of metopic suture was slightly higher in males than in females with the linear metopic suture occurring the most. Sexual dimorphism with respect to incomplete metopism types and shapes revealed no association This study is important for radiologists and neurosurgeons in diagnosis of frontal bone fractures and during surgical intervention including frontal craniotomy.