From Volume 9, Issue 3, July 2016 | Pages 110-111
This is a case report of a 16-year-old girl referred to the oral and maxillofacial department for further assessment of a radiolucent area noted at the posterior aspect of the skull vertex on a lateral cephalogram by her orthodontist. Following assessment, these were diagnosed as enlarged parietal foramina and managed conservatively.
A 16-year-old girl was referred to the oral and maxillofacial department by her orthodontist for further assessment of a radiolucent area noted at the posterior aspect of the skull vertex on a lateral cephalogram (Figure 1). The patient was a transfer case, with fixed appliances in place and the radiograph was taken as part of the clinical assessment of her further treatment needs.
The patient was asymptomatic, fit and healthy and had no past medical history of note. The mother reported an uneventful pregnancy, normal labour and vaginal delivery; no instrumentation was used during the second stage of labour.
On palpation, symmetrical depressions could be palpated through the scalp on either side of the sagittal midline just posterior to the skull vertex. Similar depressions could be palpated on the mother. A postero-anterior skull radiograph showed oval symmetrical radiolucent areas on the skull vertex within the parietal bones (Figure 2).
From the history, clinical assessment and radiographic findings, the patient was diagnosed with enlarged parietal foramina. Since the patient was asymptomatic, no further management was necessary. The patient was given the relevant information and discharged from further follow-up.
The lateral cephalogram is a standardized profile radiograph of the skull used routinely in the diagnosis and quantification of dentofacial anomalies that require orthodontic treatment.1
Incidental findings on lateral cephalograms are well reported in the literature. Familiarity with the appearance of skeletal and dental anomalies and normal variants seen in cephalometric radiographs, with the ability to separate those that require follow-up from those that do not, is an important facet of orthodontic practice.2
It has been reported in a study that about 50% of orthodontists are likely to discover a significant, potentially life-affecting pathology on a lateral cephalogram during their career.3
Parietal bone foramina are a normal feature of foetal development which usually close by the fifth month of pregnancy.4 Small foramina less than 1 mm in diameter are common and are reported to occur in 60–70% of adults. Larger defects of up to several centimetres in diameter are less common and may occur as an isolated trait, either sporadically or autosomal dominantly inherited, or in association with meningeal, cortical and vascular malformations which may predispose to epilepsy.4,5,6,7
The prevalence of enlarged parietal foramina is in the range of one in 15,000 to one in 50,000.5,8 Diagnosis of an enlarged parietal foramina is usually incidental on medical imaging. Plain radiographs characteristically show symmetrical, paired radiolucencies of the parietal bones, located close to the intersection of the sagittal and lambdoid sutures. Typically oval or round, they resemble a ‘pair of spectacles’ on postero-anterior skull radiographs. They may be less apparent on lateral skull radiographs because the lucencies are projected obliquely through normal bone. On clinical examination, a flattened region behind the apex of the skull is apparent and the defect is often palpable. Molecular genetic testing for MSX2 and ALX4, the two genes associated with enlarged parietal foramina, may be conducted.9,11 This trait is inherited in an autosomal dominant pattern and most individuals diagnosed with enlarged parietal foramina have an affected parent.
Although surgical closure has been performed,10 enlarged parietal foramina are usually asymptomatic and treatment is generally conservative as the foramina tend to reduce in size with age.11 In a minority of individuals, headaches, vomiting or intense local pain are sometimes associated with the defects, especially on application of mild pressure to the unprotected cerebral cortex. Associated headaches and seizures are treated symptomatically. The risk of penetrating injury to the brain is small and affected individuals should be educated on avoiding risky behaviour such as contact sports.
This case report highlights the importance of careful review of medical imaging for incidental findings, recommends referral of ambiguous findings for further assessment and describes a rarely encountered incidental finding on a lateral cephalogram, unawareness of which may result in undue anxiety.
