Keywords
cranium - foramen - parietal bone - forensic
Introduction
Enlarged parietal foramina (EPFs) are variable intramembranous ossification defects
of the parietal bones, first described in 1707, and which have received little attention
until the 1940s.[1]
[2] In normal fetuses, the frontal, parietal, and squamous parts of the temporal bones
undergo intramembranous ossification, a direct ossification of the vascularized membrane.
Broca, in 1875,[3]
[4] had already pointed out an unusual enlargement of the parietal foramina due to a
failure in the development of the parietal bones.[5] This neurocranial abnormality was recently reported in China for a Pleistocene human
fossil, Xujiayao 11, which constitutes the oldest evidence in human evolution of this
very rare condition.[6] This defect is known by various names, such as parietal foramina, symmetric parietal
foramina, giant foramina parietalia permagna, cranium bifidum occultum and hereditary
cranium bifidum.
Enlarged parietal foramina are located in the upper posterior angle of the parietal
bone, close to the intersection of the sagittal and lambdoid sutures between the posterior
third and the middle third of the sagittal suture ,[7] and appear as symmetric, paired radiolucencies on skull radiographs. Enlarged parietal
foramina develop as single ossification defects involving both parietal bones followed
by a variable reduction in the size of the foramina with the somatic growth during
early childhood.[8]
Enlarged parietal foramina may appear without any associated abnormality[9] or along with associated congenital bone defects,[10]
[11] soft tissue pathologies,[12] an underlying neural deficit,[13] or as part of a metabolic syndrome.[14] It may be a variant of cranium bifidum. The condition undoubtedly results from familial
inheritance due to the homeobox gene ALX4.[15] Individuals with EPF have experienced symptoms of violent headaches, vomiting and
intense pain on application of mild pressure to the unprotected cerebral cortex.[2]
[16]
Materials and Method
The present study was performed with bones from the Human Bone Collection department
of Universidade Federal do Pernambuco, state of Pernambuco, Brazil. A total of 75
skulls were examined, of which 40 were male and 35 female. We identified 2 female
skulls, 81 and 96 years old, that exhibited signs of EPF. The parameters analyzed
were the sagittal and coronal diameters of the EPFs and the distances between the
extremities of the foramina and the sagittal, coronal and lambdoid sutures. The measurements
were taken with a manual pachymeter with an accuracy of 150 mm. All the procedures
for data collection were authorized by the Ethics Committee of the of the Center of
Health Sciences of Universidade Federal de Pernambuco (CCS/UFPE, in the Portuguese
acronym), under the CAAE number 43228015.0.0000.5208.
Results
The 2 identified skulls correspond to 2.66% of the total skulls in the collection.
On the CAV90 ([Fig. 1]), the right foramen was oval with regular edges, having a 5.34 cm sagittal diameter,
and a 2.99 cm coronal diameter. It was 3.22 cm from the sagittal suture, 1.74 cm from
the coronal suture, and 5.25 cm from the lambdoid suture. The left foramen was oval,
having a 5.61 cm sagittal diameter, and 3.27 cm coronal diameter. It was 2.50 cm from
the sagittal suture, 1.87 cm from the coronal suture, and 4.65 cm from the lambdoid
suture ([Table 1]).
Table 1
Measurements (cm) of the enlarged parietal foramina
|
Cranium
|
Laterality
|
Sagittal length
|
Coronal width
|
Distance from the sagittal suture
|
Distance from the coronal suture
|
Distance from the lambdoid Suture
|
|
CAV90
|
Right
|
5.34
|
2.99
|
3.22
|
174
|
5.25
|
|
Left
|
5.61
|
3.27
|
2.5
|
1.87
|
465
|
|
Average
|
5.5
|
3.1
|
2.9
|
1.8
|
5.0
|
|
CAV16
|
Right
|
5.79
|
3.76
|
2.04
|
4.44
|
2.36
|
|
Left
|
4.18
|
2.95
|
2.46
|
4.79
|
3.73
|
|
Average
|
5.0
|
3.4
|
2.3
|
4.6
|
3.0
|
Fig. 1 Female skull, 96 years old, with enlarged parietal foramen.
On the other skull, CAV16 ([Fig. 2]), the right foramen was oval with regular edges, having a 5.79 cm sagittal diameter,
and a 3.76 cm coronal diameter. It was 2.04 cm from the sagittal suture, 4.44 cm from
the coronal suture, and 2.36 cm from the lambdoid suture. The left foramen was oval,
having a 4.18 cm sagittal diameter, and a 2.95 cm coronal diameter. It was 2.46 cm
from the sagittal suture, 4.79 cm from the coronal suture, and 3.73 cm from the lambdoid
suture ([Table 1]).
Fig. 2 Female skull, 81 years old, with enlarged parietal foramen.
Discussion
Enlarged parietal foramina are uncommon structures. However, they are well reported
in the literature.[17] The prevalence of EPF is 1:15,000 or 1:25,000.[18] Usually, these parts ossify in the fifth month of gestation. When there is insufficient
ossification around the parietal notch, they end up as large permanent foramina.[16] On cranium CAV16, the EPFs were translucent and of different sizes. At the level
of the obelion,[19] at 2.46 cm from the lambda, there were two parietal emissary foramina, one on each
side of the sagittal suture, the right measuring 0.29 cm, and the left 0. 20 cm. Individuals
with EPF have a high probability of mutation in the MSX2 or in the ALX4 genes.[15] The analyzed craniums make it impossible to know the family origin for a possible
comparison between them and other members of the family. Most people with EPF have
a positive family history, since the condition is inherited in an autosomal dominant
fashion with high but incomplete penetrance.[16] Because it is autosomal dominant, it can help forensic identification once the relatives
of the victims are aware of its existence.[20]
On the second cranium, CAV90, the EPFs were not translucent and had different sizes.
The average length was 5.0 cm, and the average width was 3.4 cm. Reddy et al[13] reported that foramen can be considered enlarged when > 5 mm. Circular, oval, or
slit-like EPF measuring several centimeters in diameter or length are rare in the
literature.[21]
[22] At the level of the obelion, there were 2 parietal emissary foramina, the nearest
to the medium sagittal suture with 0.21 cm and the most lateral with 0.13 cm, both
on the left side. The EPF represents a parietal bone ossification anomaly independent
of the coexistence of other small parietal foramina on the bone.[23] The genetic mutation that determines the appearance of EPF occurs due to a defect
in the membranous ossification of the cranium, which is directly related to the development
of the cranium, face, hair follicles and genitals.[24] In the two analyzed cases, the EPFs were closed as a result of the growth of the
cranium with advancing age. The presence of the EPFs can be associated with other
osseous variations and malformations.
Conclusion
We believe that the description of cases referring to the presence of EPFs in collections
of bones can contribute to the forensic research in order to assist in kinship identification,
since an EPF is an inherited autosomal dominant congenital malformation. Forensic
experts and other researchers need to be aware of these anatomical variations. This
type of investigation corroborates the statistics in identifying the frequency with
which these foramina currently appear.
