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52. Seet E, Chung F. Management of sleep apnea in adults - functional algorithms for the
perioperative period: continuing professional development. Can J Anaesth J Can Anesth.
2010;57:849–64. https://doi.org/10.1007/s12630- 010- 9344- y.
53. Ebert TJ, Perez F, Uhrich TD, Deshur MA. Desurane-mediated sympathetic activation
occurs in humans despite preventing hypotension and baroreceptor unloading. Anesthesiology.
1998;88:1227–32. https://doi.org/10.1097/00000542- 199805000- 00013.
54. Singh M, Liao P, Kobah S, etal. Proportion of surgical patients with undiagnosed obstructive
sleep apnoea. Br J Anaesth. 2013;110:629–36. https://doi.org/10.1093/bja/aes465.
55. Florea D, Matei AF.Riesgos anestésicos en los pacientes con apnea obstructiva del sueño. Rev
Chil Anest. 2019;48:13–9.
56. Gupta RM, Parvizi J, Hanssen AD, Gay PC. Postoperative complications in patients with
obstructive sleep apnea syndrome undergoing hip or knee replacement: a case-control study.
Mayo Clin Proc. 2001;76:897–905. https://doi.org/10.4065/76.9.897.
57. Secretaría de Salud Norma Ocial Mexicana NOM-026-SSA3–2012, Para la Practica De La
Cirugia Mayor Ambulatoria Prefacio.
58. Joshi GP, Ankichetty SP, Gan TJ, Chung F. Society for ambulatory anesthesia consensus
statement on preoperative selection of adult patients with obstructive sleep apnea scheduled for ambulatory surgery. Anesth Analg. 2012;115:1060–8. https://doi.org/10.1213/
ANE.0b013e318269cfd7.
A. A. Valadez et al.
Radiological Diagnosis inOSA
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21
VijayaKrishnanParamasivan, SrinivasKishore,
VikasAgrawal, andMohanKameswaran
21.1 Introduction
Obstructive sleep apnea (OSA) is characterized by recurrent partial or complete
upper airway obstruction occurring at the level of the pharynx during sleep [1].
OSA is diagnosed by polysomnography, and the level of obstruction is identied by
radiological imaging and sleep endoscopy. Both the investigations are essential in
evaluating and managing patients with OSAS.
Multiple soft-tissue structures surround the pharynx, and these are encased by
the maxillofacial skeleton and the cervical spine. An increase in bulk of the soft tissues and decrease in size of the maxillofacial skeleton are the anatomical causes of
constriction of the upper airway which can be evaluated radiologically.
Lateral cephalometry and sleep MRI are investigations to diagnose the level and
pattern of obstruction that are commonly done. Lateral cephalometry and computed
tomography of the airway are static airway evaluations, whereas Cine MRI will give
pathophysiological changes that happen to the airway during sleep. However, ultrasonogram of the airway is still not a commonly used method as it is a little difcult
to assess during sleep. Both CT and MRI can provide an excellent evaluation of the
V. K. Paramasivan (*)
Department of Snoring and Sleep Disorders, Madras ENT Research Foundation,
Chennai, Tamil Nadu, India
S. Kishore
AIG Hospitals, Hyderabad, Telangana, India
V. Agrawal
Speciality ENT hospital, Mumbai, Maharashtra, India
e-mail: doctor@enthospital.com
M. Kameswaran
Madras ENT Research Foundation, Chennai, Tamil Nadu, India
© The Author(s), under exclusive license to Springer Nature
Switzerland AG 2023
P. M. Baptista et al. (eds.), Obstructive Sleep Apnea,
https://doi.org/10.1007/978-3-031-35225-6_21
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V. K. Paramasivan et al.
various anatomical planes of the site of obstruction, which helps better clinical
assessment and better planning for a possible surgical approach.
These procedures have established themselves as an essential supporting assessment tools in the clinical diagnosis, preoperative evaluation, and posttreatment follow- up of patients who do not respond well to initial therapy. However, each
technique has limitations, and no gold-standard method has been established until
now. Therefore, a validated investigation capable of identifying the obstruction site
accurately during sleep enables appropriate patient selection for surgery and other
treatment modalities with an improvement in treatment outcomes.
21.2 X-ray Nasopharynx
X-ray nasopharynx or lateral radiograph of the neck is a basic commonly done
investigation to evaluate adenoidal enlargement in children. It gives a measure of
the absolute size of the adenoids and an assessment of its relation to the size of the
airway. The size of the adenoids is graded according to the palatal airway measured
from the most convex point of the adenoid tissue (A1) to the soft palate (A2)
(Fig.21.1). The narrowest distance between the nasopharyngeal soft tissues and the
soft palate was taken [2].
In Fig.21.1, we have marked the skull base as a line connecting b1 and b2. The
line connecting A and A1 is the most convex point of adenoidal tissue. The distance
between A1 and A2 is the posterior airway space. Accordingly, it has been graded
from 1 to 3. Grade 1: >6mm, Grade 2: 4–6mm, Grade 3: 0–3mm (Fig.21.2). Grade
0 is considered as post adenoidectomy. Lateral skull radiograph is a noninvasive
procedure that is well tolerated by children, unlike a exible beroptic scope. It is
still a useful tool in practice.
Fig. 21.1 X-ray
nasopharynx showing the
distance between A1 and
A2, which is the posterior
airway space between
adenoid and soft palate
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Fig. 21.2 X-ray nasopharynx showing 0–3 grades of adenoidal hypertrophy causing airway
obstruction
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21.3 Lateral Cephalometry
The standard method of assessment of the skeletal relationship is dened from measurements derived from a lateral cephalometric radiograph. Similar information is
given by a midline reconstruction from cone-beam computed tomography (CBCT)
or Multi-Detector Computed Tomography (MDCT). A small maxilla and mandible
are associated with oropharyngeal crowding and predisposition to OSA, as is a high
arched palate. Skeletal factors are a more signicant factor in children and nonobese adults.
Lateral cephalography helps analyze skeletal and soft-tissue characteristics of
patients with OSA and is available in most dental clinics, easy to perform, and less
expensive [3, 4]. Moreover, a tendency toward a shorter dimension of the cranial
base and maxillary length, maxillomandibular retrognathia, and increased anterior
lower facial height and mandibular plane angle have been reported [5–7]. Figure21.3
shows various bony landmarks and measurements.
The position of the hyoid bone with reference to the inferior mandibular border
(mandibular plane: MP) can be obtained from the same radiograph or reconstruction; multiple studies have conrmed that an inferiorly situated hyoid bone correlates closely with an increased length of the oropharynx and both measurements are
proportional to the severity of OSA [8, 9].
It provides information for anteroposterior but not lateral pharyngeal structures
implicated in the pharyngeal narrowing which is considered one of the major disadvantages. It doesn’t show the dynamic airway collapse during sleep.
Lateral cephalometry serves as an important tool in the clinical diagnosis of OSA
patients demonstrating distinct craniofacial morphological changes. Thereby gives
a clue to the site of obstruction, based on specic skeletal and soft-tissue components and helping in skeletal framework surgical planning.
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Fig. 21.3 Lateral cephalometry
21.4 Cone-Beam CT Analysis
V. K. Paramasivan et al.
Cone-beam computed tomography (CBCT) is a commonly used three-dimensional
imaging technique introduced to dentistry in 1998 [10]. The most signicant advantage is that CBCT can acquire quality images at a radiation dose equivalent to
approximately one-half of the dose associated with conventional two-dimensional
imaging.
Although 2-dimensional imaging is of great value, the complex shape of the
airway is not evaluated except with 3-dimensional (3D) imaging techniques [11].
Computerized tomography (CT) and magnetic resonance imaging are powerful
3D imaging tools. However, radiation is an issue with CT scans and the limitations
with MRI in terms of availability and compliance dictate the search for more
alternatives.
Cone-beam CT ts this gap perfectly due to its advantage in short scanning
time (10–70s), and there is a relatively low dose of radiation compared with conventional CT [12]. When utilizing a large eld of view (FOV) protocol, the upper
airway is visible within the CBCT volume and, thus, CBCT is a useful diagnostic
tool for the evaluation of the airway. Using CBCT, Enciso and colleagues, found
that the presence and severity of OSA are associated with a narrow lateral dimension of the airway [13]. Mayer and colleagues reported a decrease in the transverse width of the oropharynx in OSA subjects [14]. Despite the low soft-tissue
resolution, CBCT shows high contrast between bone, empty spaces, and soft tissues, allowing the airway to be visualized ideally in relation to the hard-tissue
structures of the skull.
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373
21.5 Radiographic Analysis
The CBCT images were exported as DICOM (.dcm) les and then imported into the
software program for analyzing. The upper airway affected by OSA is frequently
dened as the soft-tissue region bounded by the nasopharynx superiorly and the
epiglottis inferiorly. Therefore, the images of the oropharynx from the hard palate
to epiglottis were isolated from the data for analysis by using manual segmentation
of each axial slice from the surrounding soft tissue with thresholding or setting the
upper and lower gray level values of the area of interest (upper airway). Once the
airway was isolated, the software computed the area (mm2) and volume (mm3) of
each axial slice for the entire isolated portion of the airway (Fig.21.4). These area
and volume measurements were used to identify the smallest axial slice, and width
and anterior–posterior (A–P) dimension measurements were then carried out on the
smallest axial slice in each CBCT study. The average of multiple measurements was
recorded as the value representing the width and AP dimension. All linear measurements were acquired by the same individual. The total number of axial slices segmented from the hard palate to the epiglottis was used to calculate the airway length.
The A–P distance and the width of the minimum surface area of the oropharynx are
commonly used to evaluate the upper airway [15].
The volumetric analysis of the airway can also be done while asking the patient
to perform Muller’s maneuver (Fig.21.5). 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 [16]. A study conducted by
Camacho and colleagues was the rst to compare airway morphology between
upright and supine patient positions using CBCT.They found that the minimum
Fig. 21.4 CT airway volumetric analysis from nasal cavity to hypopharynx
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Fig. 21.5 CT airway volumetric analysis during Muller’s maneuver
cross-sectional area decreased from 124±29 to 30±5mm2 when the patient was
scanned in the supine position [17]. Finally, the average area and volume assessment of the total mean airway volume is made.
V. K. Paramasivan et al.
21.6 Role ofCBCT inSurgical Planning
Specic software analyzed raw DICOM data from CBCT scanning including linear
and volume and the smallest cross-sectional area where assessments are made.
CBCT was performed at both ends of expiration and inspiration, which helped in
the accurate determination of the level of collapse. Subsequently, this could change
the surgical decision, especially in retroglossal collapse patients. CBCT is considered a low dose, a highly efcient diagnostic tool essential in conjunction with a
clinical assessment to evaluate OSA, especially in severe cases properly [18].
21.6.1 Dynamic MRI
Magnetic resonance imaging of the upper airway during sleep is also termed sleep
MRI, Cine MRI, or Dynamic MRI. It can detect the level, degree, and cause of
obstruction in the upper airway, which helps the clinical diagnosis and treatment.
This noninvasive imaging is used to identify the site of upper airway obstruction for
the prediction of treatment outcomes and monitoring and follow-up of patients with
OSAS after therapy. In addition, MRI of the airway with cine sequence is
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considered an excellent alternative method to examine dynamic upper airway conditions during sleep [19–21]. MRI sleep studies are noninvasive and allow dynamic
abnormalities of the entire airway to be assessed at once.
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21.6.2 Anatomical Subdivision ofUpper Airway
The upper airway is divided into nasopharynx, velopharynx, oropharynx, and hypopharynx. The nasopharynx is the region between the skull base, and the horizontal
imaginary line from the tip of the post nasal spine of the hard palate. Velopharynx is
the region between the postnasal spine and the tip of the soft palate. The oropharynx
is the region between the tip of the soft palate and the tip of the epiglottis.
Hypopharynx is the region between the tip of the epiglottis and the level of the
glottis.
21.6.3 Dynamic Sleep MRI Technique
In this dynamic sleep MRI, midsagittal and axial sequential T1-weighted (repetition
time, 650 milliseconds; echo time, 14 milliseconds) and T2-weighted (repetition
time, 6000 milliseconds; echo time, 90 milliseconds) images with 3-mm slice thickness will be taken. The sagittal planes are obtained from the midline laterally, and
the axial planes are obtained from the skull base to the larynx. Patients will be in a
supine position with the neck in a neutral position and they are instructed to refrain
from swallowing during scanning and to breathe through their nose with their mouth
closed. Then the patient will be asked to sleep and then the images will be acquired
once the patient starts snoring and apnea happens. The image analysis is done on a
workstation with the determination of the level and cause of obstruction. Twodimensional distances and diameters of the upper airway or its related structures are
measured. We can evaluate the volumes of the soft-tissue structures such as the
tongue, the soft palate, or the pharyngeal walls or the remaining compromised or
noncompromised airway spaces. We can also obtain 3-dimensional data, volumes
based on cross-sectional areas, and slice thickness by various computerized models
[22, 23].
Dynamic MR imaging can obtain rapid images (1 image per second) that are
temporally spaced a short time apart. It can show the dynamic motion of the upper
airway, thereby allowing visualization of the changing shape and conguration of
the airway during respiration and evaluation of the relationship between the soft
tissue of the upper airway such as adenoid, palatine tonsils, and soft palate and the
degree of airway collapse [24, 25].
Dynamic MR obtained during a normal sleeping state shows the patent nasopharynx and retroglossal airway with minimal airway motion. The degree of movement of the retroglossal airway is less than 5mm. Dynamic MR in OSAS patients
shows complete airway collapse at the level of the soft palate and base of the tongue
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during apneic events. Sedation is usually not recommended in these studies, especially in adults as it carries the risk of prolonged airway obstruction. It can be used
in children to simulate natural sleep.
Recently, a real-time MR imaging platform for synchronous, multiplanar visualization of upper airway collapse in OSAS at 3 Tesla can be performed to promote
natural sleep, with an emphasis on lateral pharyngeal wall visualization [26].
V. K. Paramasivan et al.
21.6.4 Dynamic Sleep MRI inDiagnosing OSAS
Current theories on OSAS pathogenesis involve a combination of abnormal anatomy of the pharynx and the physiology of the upper airway dilator muscles.
Anatomical changes in OSAS include decreased anteroposterior, lateral, crosssectional, and volumetric measurements at different pharyngeal levels. In addition,
dynamic sleep MRI helps to identify the level, pattern, degree, and cause of upper
airway obstruction.
21.6.5 Level ofAirway Obstruction
Retropalatal and retroglossal level of obstruction is the most typical site of upper
airway obstruction. Identifying the level of obstruction is crucial in deciding treatment planning and single or multilevel surgery.
21.6.6 Degree ofAirway Obstruction
Measuring the anteroposterior and transverse diameters and cross-sectional area
and volumetric assessment of the airway and soft-tissue structures can help determine of the degree of airway obstruction in patients with OSAS.The measured soft
tissues are adenoid tonsils, lingual tonsils, palatine tonsils, soft palate, tongue, lateral pharyngeal wall, and fat pad area. The measurement is usually done at the largest section of the soft tissue and the most narrowed section of the airway. The
cross-sectional area of the soft tissues and the airway at different levels is calculated. Measurement of the upper airway revealed enlarged soft-tissue structures and
narrowed pharyngeal airway in patients with OSA.The values are calculated and
compared when the patient is awake and while sleeping and snoring.
21.6.7 Advantage andLimitations
Magnetic resonance imaging provides an image with excellent contrast of the softtissue structures in patients with OSA.A fast MR imaging can show the anatomical
obstruction dynamically during apnea. Magnetic resonance imaging does not
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377
Fig. 21.6 Dynamic MRI
sagittal view of OSAS
patient showing different
pattern of palate, (a) tunnel
shaped soft palate, (b)
funnel shaped soft palate,
(c) long hard palate with
very short soft palate
a
b
c
expose patients to ionizing radiation, and allowing imaging in multiple planes. The
major limitations of MR imaging are as follows: long examination time, noisy scanning, claustrophobic effects experienced by many people while in the gantry tube,
and high cost. The lack of a comfortable sleep environment also limits the ability to
use MR imaging during sleep [27, 28].
The major advantages of dynamic MRI compared to drug-induced sleep endoscopy are easy differentiation of primary from secondary soft palate collapse and
identication of various patterns of soft palate such as tunnel or funnel-shaped soft
palate and also the length of the hard and soft palate (Fig.21.6). If the soft palate is
very short, any soft-tissue surgery may not improve the surgical outcome. For a long
hard palate, bony framework surgery like transpalatal advancement pharyngoplasty
can be planned.
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