Role of CBCT in sleep apnea – A review

Introduction

Sleep apnoea may be described as a potentially life threatening disorder in which periods of cessation of breathing occur in the presence of inspiratory effort i.e; the chest wall is active, but no air reaches the lungs.^[1] Sleep apnea can be associated with lack of energy, fatigue during daytime, memory impairment and may lead to number of diseases, including hypertension, stroke and coronary heart disease. The prevalence of sleep apnoea worldwide in the adult population is about 2% in women and 4% in men, based on minimal diagnostic criteria (AHI ≥5 and excessive daytime sleepiness). Increased prevalence of sleep apnoea is seen in older aged group of 65 years and above. Subjective reports from epidemiological study in the US conducted including large population have found that the prevalence of reported apnoeas in women and men was 4% and 13% respectively. While the prevalence of reported snoring was 19% for women and 33% for men.^[2] Sleep apnea is further classified into 3 types: Obstructive sleep apnea (OSA), Central sleep apnea (CSA), and Mixed apnea (MSA).^[3]

Assessment of Sleep Apnea

The pathophysiologic mechanisms predisposing to SA are complex and overlapping. Thus, neither history nor physical examination is sufficiently accurate to exclude the diagnosis of SA. Various clinical prediction rules can assist in identifying patients with a high pretest probability for SA.^[10] Because of the high prevalence of OSA and patients often not reporting sleep problems to clinicians, the review of systems should include asking about history of snoring, pause in breathing during night, and excessive fatigue or sleepiness during the day. Many Questionnaires available for preoperative screening of which the first and foremost include thorough history taking.^[11]

Cone Beam Computed Tomography in Airway Imaging

As OSA may be ascertained through loud snoring, excessive sleepiness during daytime, fatigue and arousal from sleep due to oxygen desaturation.^[19] However, due to the insufficient awareness of the above condition, almost 80% of individuals with OSA suffer from the disease unnecessarily despite of the modern investigations, medical facilities and dental treatments that are available on hand.^[20] Early diagnosis of OSA is usually strenuous, as insufficient results and data have been published for the numerous tools that have been proposed, hence disqualifying them as evidence-based screening tools. Many questionnaires have been developed to help diagnose OSA as early and straightforwardly as possible.^[20] With the increased incidence of this condition, there may be many patients with undiagnosed OSA who report to dental clinics for routine dental checkup. Dentists should have a high index of clinical suspicion and an appropriate high understanding of this condition to perform the in home basic screening to recognise patients suspected of having OSA during routine dental procedure. ^[21] Any technology that would enhance clinicians ability to visualize where in the airway obstruction occurs would help identify those subsets of patients who may or may not benefit from a choice of treatment modalities.^[22] However, approximately 25-50% of patients with OSA will either refuse the offer of PAP therapy, or will not tolerate it.

The best way to non invasively assess the airway changes is by using imaging modalities. Airway volume has been measured with various imaging techniques, including computed tomography (CT), cone-beam computed tomography (CBCT), cephalometry, fluoroscopy, nasopharyngoscopy, and magnetic resonance imaging (MRI).^[23] Many of the previous studies had limitations in evaluating the upper airway volume based on patients’ lateral cephalograms.^[24] With the advent of newer 3D imaging such as CBCT we have overcome the limitations. Cone-beam computed tomography (CBCT) is an 3D imaging modality commonly used in the dentistry to capture accurate 3-dimensional images.^[22] As enlarged soft tissues around the airway are also a important predisposing factor for OSA, With the increasing use of CBCT in dental clinics in recent years, dentists could use CBCT as a screening modality by assessing the upper pharyngeal airway to rule out the maxillofacial anatomy predisposing to obstructive sleep apnea.^[22]

The parameters such as A-P distance and the width of the minimum surface area of the oropharynx are more commonly used to evaluate the upper airway. A recent systematic review revealed that the most common measurements of the airway used to evaluate OSA subjects with CBCT included total volume and minimum cross-sectional area, followed by area and lateral and anterior-posterior linear measurements.^[25] Other methods of assessing upper airway includes measuring the total length of upper way, total airway volume of oropharyngeal region, the average airway volume of the oropharyngeal region, and the smallest width and anteroposterior (AP) measurements.^[22]

Conclusion

Although PSG is the most commonly used technique for the identification of the degree of airway obstruction, the use of 3D modality such as CBCT is fast becoming an integral part. CBCT is useful in 3D volumetric assessment of the retropalatal and retroglossal area and thus, is an important aid in the diagnosing of conditions affecting the airway resulting in debilitating conditions like OSA. CBCT is a less time-consuming, cheaper and more convenient alternative for the patient when compared to PSG and can serve as a useful adjuvant tool in the diagnosis of OSA. Increasing levels of expertise in CBCT and the availability of reliable questionnaires have enabled routine screening of dental patients for OSA, so as to potentially diagnose patients and can be referred to a sleep specialist, medical clinic for further evaluation, investigation and proper treatment, if needed, as well as receiving any necessary dental interventions.

Source of Funding

None.

Conflict of Interest

None.