David Solsberg, MD, PC

Dr Dave

Health Images at Cherry Hills
3601 South Pearl Street
Englewood, CO 80113
ph: 3037620060
fax: 3037621131

Sleep Apnea Imaging

 

Imaging of Obstructive Sleep Apnea  Copyright David Solsberg, MD, PC.2007 All rights reserved.

 

MD Solsberg, MD,FRCPC email dr dave

Obstructive sleep apnea affects at least 5 % of Americans. The incidence of this hidden killer is increasing and OSA frequently goes undiagnosed for years. OSA is defined as sleep disordered breathing associated with daytime symptoms. Common symptoms include headache, daytime sleepiness difficulty concentrating and waking up soaked with sweat.  Also patients present frequently with heartburn.  One of the commonest presentations is that a sleeping partner notes that their snoring spouse stops breathing and becomes pale at night. 

OSA patients experience multiple episodes of airway collapse during sleep resulting in apnea (complete obstruction of the airway) or hypopnea (incomplete obstruction with decreased ventilation).   Some patients may experience 40 or more episodes of apnea and/or hypopnea per hour.  This results in a tortured fragmented sleep cycle with episodes obstruction and choking during REM sleep resulting in hypoxemia followed by arousal with gasping respiration. I refer to this as the “Choke and Gasp cycle”  

 

 OSA patients also often complain of night sweats and sore muscles.  Gastroesophageal reflux symptoms are common due to the negative intrathoracic pressure during attempted inspiration during upper airway obstruction. Typically, patients awake exhausted and are sleepy and irritable during the day from REM deprivation. 

        These repeated episodes of hypoxia also result in multiple metabolic and central nervous system abnormalities.  Sleep apnea patients experience 1.5 to 4 times increased risk of stroke.  Also sleep apnea patients have a substantially increased risk of hypertension, cardiac ischemia, arrhythmia and sudden death.  OSA patients also are much more likely to suffer from type II diabetes, even corrected for body mass, likely due to insulin resistance.

      OSA is diagnosed with polysomnography (sleep test).  These overnight tests correlate oxygen saturation, EEG, abnormal sleep associated movements with apnea and hypopnea episodes. 

      Continuous positive airway pressure (CPAP) therapy is currently the most effective treatment for OSA.  A nasal or full face mask is used to pressurize the airway to help stent the airway open during sleep.  CPAP is very effective in reducing day-time symptoms and also  reduces blood pressure, arrhythmias, insulin requirements, stroke and heart disease.

  

 Indications for Imaging

    

     Airway obstruction occurs typically during REM sleep. However an abnormal airway is present in OSA patients even when awake.  Findings may be subtle however and advanced image processing is used to facilitate diagnosis. Imaging is used primarily for treatment planning of patients with OSA and not for primary diagnosis. Polysomnography  is the gold standard for the diagnosis of OSA .

        Unfortunately only 60% of patients tolerate CPAP therapy and it has been reported that less than 1 in 5 patients follow their sleep consultant’s prescriptions for sleep therapy.  The primary indication for OSA imaging is to determine treatable causes of airway instability and obstruction for patients not tolerating medical therapy and to improve CPAP compliance. The commonest causes of CPAP intolerance are claustrophobia, nasal obstruction and retroglossal narrowing.  Imaging is specifically helpful in determining which patients may respond to nasal medical therapy, mandibular advancement devices, septoplasty and potentially palatoplasty.

    Another indication for imaging includes the evaluation of the OSA patient with unexpected sleep apnea. Most patients with OSA are obese.  Obesity may directly result in airway obstruction because of fat deposition around the airway or more commonly from thickening of the pharyngeal musculature and supporting tissues.  OSA patients with normal BMI (body mass index) frequently have facial and mandibular abnormalities that predispose to upper airway obstruction. Less common causes of OSA such as tracheal stenosis, severe head injury and other CNS abnormalities are best evaluated with a combination of imaging with CT and MRI imaging.  

     Imaging may also be used to evaluate response to dental and medical therapy.

Technique

      Axial imaging techniques with CT and MRI have supplanted the traditional cephalometric techniques.  Fast MRI imaging techniques with spoiled gradient recall (SPGR) and fast spin echo imaging may be used. MRI imaging is generally more expensive and less available than CT and at our institution low dose helical CT is used.  Also many larger patients are uncomfortable in the relatively small bore of MR scanners.  Low dose techniques are used to reduce x-ray dose and is the study of choice in the evaluation of the airway.  IV contrast is not routinely required.  The airway is image from the paranasal sinuses to the carina with a 3D dataset.  The images are acquired with the patient quietly breathing through the nose and the study including processing is completed typically within 15 minutes. The images are then processed and interpreted on an independent workstation with measurement of the retropalatal and retroglossal dimensions. Also volume rendering techniques are used to evaluate the facial skeleton and airway.  Bony abnormalities such as micrognathia and macrognathia are common in OSA patients especially in patients with a normal body habitus and are often difficult to specifically characterize clinically or on routine imaging. 3D volume rendering (VR) techniques are essential in the diagnosis of facial bone abnormalities.

      The same axial data set used for reformatting and bone VR can be rendered to display only the air containing structures (ACS). ACS technique is a 3D technique and therefore images can be rotated in any plane in three dimensions on the workstation. This allows the interpreting physician and sleep consultants to better understand the pattern of airway obstruction compared to routine imaging techniques.  Normal anatomy of ACS images is shown below

 

 

NORMAL AIRWAY

Volume rendered air containing structure (ACS) image and right is a standard reformat image.  The retropalatal (short vertical arrow) and retroglossal (long vertical arrow) airway region are separated at the tip of the palate (P). The vallecula (V) is located anterior to the epiglottis (E).

 

 


 

Frontal view

The retropalatal (RP) and retroglossal (RG) airway region are separated at the tip of the palate (P). The vallecula (V) is located anterior to the epiglottis (E) at the entrance to the larynx and trachea (T). The maxillary sinus (M) is also shown

 

Airway Compromise in OSA

Airway obstruction in OSA is usually multifactorial. The airway may be obstructed at the level of the nasal cavity, nasopharynx, retropalatal and/or retroglossal airway (oropharynx) or less commonly within the larynx or trachea. 

Nasal Obstruction

Nasal airway narrowing frequently results in CPAP intolerance.  High nasal CPAP settings are required to keep the airway open resulting in difficulties with nasal mask fit and resultant mouth breathing and oral venting.    Common causes of nasal obstruction include septal deviation and enlargement of the nasal turbinates (associated with chronic allergic or vasomotor rhinitis. Pneumatized middle turbinates (concha bullosa) may also contribute to nasal obstruction.  Benign nasal obstruction usually responds to nasal steroids and antihistamines and septoplasty and treatment of enlarged turbinates are used to improve CPAP tolerance. Less common causes of nasal obstruction include polyposis, neoplastic disorders and enlarged adenoidal tissues. 

Mouth Breathing  VR ACS Image

 

 

Patients are instructed to breath through the nose during the OSA CT exam. This patient (above) has nasal obstruction and not tolerating nasal CPAP. The patient is mouth breathing air is seen superior to the tongue. Note the narrowed posterior nasal cavity (arrows) obstructed by enlarged turbinates. A very long thickened palate (P) is present corresponding to a clinical Mallampati IV grade.

 

Retropalatal Airway Obstruction

Thickening and elongation of the soft palate and uvula predispose to snoring and sleep apnea ( Imaging findings highly correlate with the Mallampati grading system of palatal morphology. Typically in OSA patients with retropalatal narrowing the palate measures over 10 mm in thickness.   The retropalatal airway area is also frequently narrowed. The normal cross sectional area of the retropalatal airway is typically greater than 100 mm2.   A cross sectional airway of less than 50 mm2 is strongly associated with severe OSA.   

 

Axial images through Retropalatal (RP) airway.

 

 

 

 

A: Severe RP airway narrowing measuring less than 30 mm2 posterior to palate (P). Patient has severe OSA diagnosed by polysomnography.

B: Normal RP airway for comparison.

 

VR-ACS Frontal View: Retropalatal Obstruction.

 


A: This patient has severe OSA with retropalatal and retroglossal narrowing. Note the narrowing of the transverse dimension (double ended arrow) of the retropalatal airway (RP). The location of the tip of the palate (P) and mildly narrowed  retroglossal airway (RG) is shown. The vallecula (V) is located at the anterior aspect of the hypopharynx and the piriform (P) sinuses are located posterolaterally.

B: Normal view for comparison.

 

 

Retroglossal and Pharyngeal Obstruction

 

In obese patient the retroglossal airway is narrowed by thickening of the soft tissues and muscles around the airway and by enlargement of the tongue (The parapharyngeal soft tissues may also be enlarged contributing to airway narrowing. The vallecula and piriform recesses are frequently effaced. 

Axial images: Retroglossal (RG) narrowing with normal comparison.

 


A:  The soft tissues around the retroglossal airway are circumferentially thickened with resultant narrowing in this obese patient with OSA. The airway is round rather than than the normal oval or rectangular shape

B: Normal for comparison. The airway is more oval with patent lateral recesses.

Sagittal Images of a patient with retroglossal narrowing and severe OSA.


A: Sagittal reformat view shows the posterior displacement of the enlarged tongue. The palate (P) is also long and thickened contributing to narrowing of the airway.

B: VR-ACS view shows the marked narrowing of the retroglossal airway even while the patient was awake. Patient was referred for dental evaluation for a mandibular advancement device.

 

Facial and Dental Associated Abnormalities

Facial bony abnormalities are a common cause of airway narrowing in non-obese patients and often result in narrowing of the retropalatal and retroglossal airway.  These abnormalities are best evaluated with volume rendered 3D images as these disorders are difficult to diagnose clinically and on routine axial imaging. Mandibular hypoplasia  results in a small recessed chin with resultant posterior displacement of the tongue narrowing the airway. Maxillary retrognathia

may also narrow the airway. These disorders should be suspected in patients with facial deformity and with history of childhood dental extraction for crowding.

The retroglossal airway is widened by forward movement of the mandible and the attached tongue.  This is similar to the well known jaw thrust maneuver used to improve the airway in sedated or stuporous patients.   There are multiple dental devices used to achieve mandibular advancement.  Typically a dental device is snuggly fitted on the upper and lower dentition gently positioning the mandible forward thus widening the retroglossal airway. During REM sleep, the facial muscles are atonic. These dental devices help prevent the tongue and mandible from falling back during REM sleep reducing both snoring and OSA. Dramatic improvement in the retroglossal airway can be achieved with mandibular advancement devices and images can be obtained with and without mandibular advancement to assess the efficacy of dental devices.  The tongue and soft palate are attached by the tonsillar pillars. Therefore the retropalatal airway may be widened with mandibular advancement devices and procedures further reducing airway resistance.Mandibular and maxillary advancement surgery is used to improve the upper airway and imaging may also be used for operative planning.

 

Images of patient will small mandible with normal comparison.


A: Normal Bone 3D VR image on left with axial image through the RG airway on left. Note that the mandibular size is proportionate to the maxilla and orbits.

B: This woman had a thin body habitus but has severe OSA.  Note the recessed and small (hypoplastic mandible (arrow) and marked narrowed RG airway on the axial image

Maxillary and Mandibular Retrognathia with RG and RP narrowing.


A: Normal VR 3D Bone side view. The maxilla and mandible are proportionate to the upper face and skull

B: Thin male with severe OSA. The maxilla and mandible are recessed (arrows) .

C: Sagittal reformat: Both the RG and RP airways are narrow. The tongue is too large for the mouth and narrows the airway.  Note the short hard palate.  CPAP tolerance was significantly improved with a mandibular advancement device.

 

Axial images obtained through RG airway with and without mandibular advancement device.  This patient has mandibular hypoplasia and severe OSA. (Also see images just below)


A:  This image was obtained without the dental device. The RG airway is narrowed with a cross sectional area of 112 mm2 with narrowing of the lateral recesses.

B:  This image was obtained with the mandibular advancement device in place. When the mandible is advanced movingthe tongue and tonsils forward opening the airway. The airway now measures 295 mm2 and looks normal.

 

Sagittal views through RG airway with and without mandibular advancement device.  This patient has mandibular hypoplasia and severe OSA.


A:  This image was obtained without the dental device: The RP and RG (double ended arrows) airways are narrowed.

B:  This image was obtained with the mandibular advancement device in place. The RG and the RP airways are widened.

 

 

Tracheal stenosis

Tracheal stenosis may be congenital but may occur after prolonged intubation or tracheostomy and is an unusual cause of OSA.

OSA due to Tracheal stenosis (arrow) of intrathoracic trachea.

 


A: Sagittal reformat      B: VR-ACS      C: Axial View

 

Bruxism and Clenching

Enlargement of the muscles of mastication (Figure 15) is common in patients with OSA.  This presents clinically with bilateral palpable enlarged masseter muscles that may appear mass-like. This is termed benign masseteric hypertrophy. Patients present with symptoms of teeth grinding and clenching such as temporomandibular or dental pain and abnormal dental wear. Enlargement of the masseter, pterygoid and anterior belly of the digastric muscles are commonly seen and are associated with symptoms of clenching and bruxism. Symptoms of bruxism may also be significantly improved with dental advancement and splints.

 

Axial Image of Enlarged muscles of Mastication.


Image shows enlarged masseter (M) muscle presenting clinically as benign masseteric hypertrophy associated with sleep apnea. The lateral and medial pterygoid muscles (LP) were also enlarged. RP narrowing is also seen. The patient was noted to have bruxism during polysomnography.

 

Conclusion

Treatment reduces the health consequences of OSA.  Imaging is valuable in determining sites of potential airway obstruction to direct treatment of the specific causes of obstruction to improve CPAP tolerance and assist in dental and nasal treatment planning.   VR imaging is important in the diagnosis of maxillary and mandibular abnormalities and helps the radiologist understand the 3D anatomy of the airway.

     Sleep apnea imaging is a new and valuable tool in the fight to turn the deadly “Choke and Gasp” cycle into a good night’s sleep for patients and their loved ones.

 

MD Solsberg,MD FRCPC

References

Axial CT Measurements of the Cross-sectional Area of the Oropharynx in Adults with Obstructive Sleep Apnea Syndrome

Elieser Avrahami, Alexander Solomonovich, and Moshe Englender

AJNR Am J Neuroradiol 17:1107–1111, June 1996

 

Obstructive Sleep Apnea

Sean M. Caples, DO; Apoor S. Gami, MD; and Virend K. Somers, MD, PhD Ann Intern Med. 2005;142:187-197.

 

Obstructive sleep apnea, Diagnosis, medical management and dentalimplications

KELLY R. MAGLIOCCA, D.D.S.JOSEPH I. HELMAN, D.M.D JADA, Vol. 136 www.ada.org/goto/jada August 2005

 

Parameters Optimization of the Procedure by Combining Clinical and Oximetric

Mandibular Advancement Titration for Obstructive Sleep Apnea:

Nathalie Pelletier Fleury, Bernard Meyer and Bernard Lebeau

Bernard Fleury, Dominique Rakotonanahary, Boris Petelle, Gérard Vincent,

Chest 2004;125;1761-1767

 

The Nose and Sleep-Disordered Breathing: What We Know and What We Do

Not Know

Maria Rappai, Nancy Collop, Stephen Kemp and Richard deShazo

Chest 2003;124;2309-2323

 

Recent advances in understanding the pathogenesis of obstructive sleep apnea

Amy S. Jordan, David P. White and Robert B. Fogel Curr Opin Pulm Med 9:459–464. © 2003 Lippincott Williams & Wilkins.

 

Association of Systematic Head and Neck Physical Examination With Severity of

Obstructive Sleep Apnea–Hypopnea Syndrome

Adriane I. Zonato, MD, PhD; Lia Rita Bittencourt, MD, PhD; Fernanda Louise Martinho, MD;Joa˜o Ferreira Santos Ju´ nior, DDS; Luiz Carlos Grego´rio, MD, PhD; Sergio Tufik, MD, PhD Laryngoscope, 113:973–980, 2003

 

QUICK FACTS

  • Snoring isn't funny: Snoring can be associated with sleep apnea
  • Sleep apnea is common and is associated with hypertension, diabetes, gastroesophageal reflux, heart arrythmias, sudden death, stroke , seizures, ADHD disorder and increased risk of road trauma.
  • 70 % of people with a stroke have sleep apnea
  • 60 % of patients with pacemakers have sleep apnea
  • Sleep apnea imaging studies are used to help improve CPAP tolerance and to direct treatment of airway obstruction. 
  • Talk to your doctor to  get a referral to a sleep medicine specialist if you or spouse are:

Sleepy during the day

Snore loud enough to be heard in an adjacent room or choke and gasp or night or Wake up soaked with sweat

Suffer from morning or night time heartburn

 

 

 

Copyright David Solsberg, MD, PC. All rights reserved.

Hosted by Yahoo!

 

 

 

Health Images at Cherry Hills
3601 South Pearl Street
Englewood, CO 80113
ph: 3037620060
fax: 3037621131