Dynamic Response of the Skull with Sinuses under Blunt Frontal Impact: A Three-Dimensional Computational Study

Resonance Effect of the Frontal Sinus on Ocular Vestibular-Evoked Myogenic Potential Recordings

OBJECTIVE

This study performed ocular vestibular-evoked myogenic potential (oVEMP) test via Fpz bone vibration (termed Fpz-oVEMP) and Fz bone vibration (termed Fz-oVEMP) using a minishaker. The aim of this study was to evaluate the resonance effect of the frontal sinus on the oVEMP recordings, so as to establish an optimal clinical protocol for eliciting oVEMPs by bone vibration.

DESIGN

Thirty healthy volunteers (15 children and 15 adults) and 15 adults with frontal sinusitis were enrolled in this study. All subjects underwent oVEMP test via Fpz and Fz bone vibration stimuli, and volume of the frontal sinus was measured by CT scan.

RESULTS

Because healthy adults (3.20 ± 1.08 mL) had significantly larger frontal sinus volume than healthy children (2.04±1.87 mL), the former (100%) showed higher response rates of Fpz-oVEMP than the latter (30%), but not Fz-oVEMP. When the frontal sinus volume is >1.91 mL (approximately at the age of 14 years), Fpz-oVEMP displayed larger reflex amplitude than Fz-oVEMP did. In contrast, Fpz-oVEMP (30%) displayed lower response rate than Fz-oVEMP (73%) in patients with frontal sinusitis.

CONCLUSIONS

Both developmental (frontal sinus volume) and pathological (frontal sinus inflammation) factors may affect the oVEMP responses via altering resonance function. For the developmental factor, frontal sinus volume >1.91 mL may initiate the resonance effect on oVEMPs, as evidenced by higher response rate with larger reflex amplitude of Fpz-oVEMP than Fz-oVEMP. For the pathological factor, frontal sinusitis may hamper the resonance effect on oVEMPs, as shown by the lower response rate of Fpz-oVEMP than Fz-oVEMP. Hence, oVEMP test may be performed via Fpz bone vibration first in healthy adults, while via Fz bone vibration first in children aged under 14 years or subjects with frontal sinusitis.

Prevalence of Frontal Sinus Aplasia in Jordanian Individuals

Our paper aims to investigate the prevalence of frontal sinus aplasia among Jordanian individuals and compare it with values from different populations. Retrospectively, the study was done for 167 of the paranasal sinuses coronal tomography (CT) for patients who attended the clinic from January 2019 to August 2019 in King Abdullah University Hospital Irbid, Jordan. The authors analyzed the multiplanar CT scans to perform our work. The authors excluded the following images from our study: patients younger than 18 years old, patients with history of skull base trauma that impaired visualization of the frontal sinus, and images with fibro-osseous lesions that impaired the visualization of the frontal sinus. The prevalence of bilateral frontal sinus aplasia is 4.2% among Jordanian individuals and 6.6% is the prevalence of unilateral frontal sinus aplasia. Both values are consistent with average values among different populations. Moreover, we noticed the higher prevalence in both the bilateral and unilateral frontal sinus aplasia in males compared to females. The prevalence of frontal sinus aplasia among Jordanian individuals is almost within the same values among different populations. These numbers regarding the bilateral and unilateral frontal sinus aplasia is crucial to push the surgeon to evaluate CT of the paranasal sinuses preoperatively and focus on the presence of frontal sinuses on CT images to prevent unwanted complications during sinus surgeries.

Biomechanical analysis of skull trauma and opportunity in neuroradiology interpretation to explain the post-concussion syndrome: literature review and case studies presentation

Traumatic head injuries are one of the leading causes of emergency worldwide due to their frequency and associated morbidity. The circumstances of their onset are often sports activities or road accidents. Numerous studies analysed post-concussion syndrome from a psychiatric and metabolic point of view after a mild head trauma. The aim was to help understand how the skull can suffer a mechanical deformation during a mild cranial trauma, and if it can explain the occurrence of some post-concussion symptoms. A multi-step electronic search was performed, using the following keywords: biomechanics properties of the skull, three-dimensional computed tomography of head injuries, statistics on skull injuries, and normative studies of the skull base. We analysed studies related to the observation of the skull after mild head trauma. The analysis of 23 studies showed that the cranial sutures could be deformed even during a mild head trauma. The skull base is a major site of bone shuffle. Three-dimensional computed tomography can help to understand some post-concussion symptoms. Four case studies showed stenosis of jugular foramen and petrous bone asymmetries who can correlate with concussion symptomatology. In conclusion, the skull is a heterogeneous structure that can be deformed even during a mild head trauma.

Trauma of the Frontal Region Is Influenced by the Volume of Frontal Sinuses. A Finite Element Study

Anatomy of frontal sinuses varies individually, from differences in volume and shape to a rare case when the sinuses are absent. However, there are scarce data related to influence of these variations on impact generated fracture pattern. Therefore, the aim of this study was to analyse the influence of frontal sinus volume on the stress distribution and fracture pattern in the frontal region. The study included four representative Finite Element models of the skull. Reference model was built on the basis of computed tomography scans of a human head with normally developed frontal sinuses. By modifying the reference model, three additional models were generated: a model without sinuses, with hypoplasic, and with hyperplasic sinuses. A 7.7 kN force was applied perpendicularly to the forehead of each model, in order to simulate a frontal impact. The results demonstrated that the distribution of impact stress in frontal region depends on the frontal sinus volume. The anterior sinus wall showed the highest fragility in case with hyperplasic sinuses, whereas posterior wall/inner plate showed more fragility in cases with hypoplasic and undeveloped sinuses. Well-developed frontal sinuses might, through absorption of the impact energy by anterior wall, protect the posterior wall and intracranial contents.