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The Nasal Septum
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Thorough examination and visual inspection of the patient who complains of nasal airway obstruction are essential for diagnosis and treatment planning. Visual assessment of the external appearance of the nose is of utmost importance. This examination initially focuses on the size, shape, symmetry, and straightness of the nose; one should document the size of nostril openings, the thickness of the alae, and the width of the columella. Columellar widening may be seen with caudal septal cartilage deviation, splaying of the medial crura, or excess soft tissue. Septoplasty will correct airflow only if air can get into the nose. A previously fractured nose can hold the dorsal septum off of the midline, and no septoplasty alone can correct this problem (Figure 44-4, A and B). Such situations require sharply freeing up the septum from the upper lateral cartilages and performing medial osteotomies and a septoplasty with release of the septum from the maxillary crest for correction. Deformity of the nasal vault can narrow the diameter of the nasal passage.
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Figure 44-4. A, Deviated nose prior to septoplasty. B, The significant correction of the deviated nose with septoplasty alone makes it incumbent on surgeons to always straighten the deviated septum prior to any lateral or medial osteotomies. To view this image in color, please go to www.ototext.com or the Electronic Image Collection CD, bound into your copy of Cummings Otolaryngology—Head and Neck Surgery, 4th edition.
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The patient with a crooked or C-shaped nose often has a severely deviated septum as well. Before examining the nose internally, one must observe the patient’s nose during normal and exaggerated nasal breathing, watching the side walls for evidence of internal or external collapse (Figure 44-5, A and B). Care must be taken when assessing the chronic sniffer or “nasal neurotic,” however, who will show collapse as a result of an overly aggressive inspiratory force being generated, regardless of the competency of the valve. Surgery for the chronic sniffer will generally lead to poor outcomes despite adequate anatomic support and deflection correction, and it will often include frequent postoperative phone calls and second opinions obtained with regard to his or her problem, which is still perceived as uncorrected.
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Figure 44-5. A, Patient breathing through the nose at rest. B, Collapse of the nasal sidewall inclusive of nasal valve with forced inspiration To view this image in color, please go to www.oto-text.com or the Electronic Image Collection CD, bound into your copy of Cummings Otolaryngology—Head and Neck Surgery, 4th edition.
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Anterior rhinoscopy allows for visualization of the septum, the turbinates, and the nasal valve—the most narrow area of the airway bordered by the septum, the upper lateral cartilage, and the anterior aspect of the inferior turbinate. Examination of the patient should be performed before and after decongestion to fully evaluate the contributing factors to nasal obstruction and to allow for a complete nasal examination. A large swollen turbinate can often obscure a posterior nasal spur. There should be no surprises at the time of surgery as a result of inadequate preoperative problem recognition. Nasal endoscopy with a rigid endoscope of the sinonasal region can be carried out to fully evaluate intranasal structures and assess for polyps, masses, and adenoidal size. The 4-mm 30-degree endoscope provides an excellent view.
External evaluation of the patient’s nose should include performance of the Cottle maneuver, in which lateral distraction of the nasal valve is performed (Figure 44-6). This maneuver may improve the sensation of nasal obstruction in cases of nasal valve collapse or anterior septal deviation. A positive Cottle maneuver may suggest nasal valve compromise,34 but it is not always a reliable indicator, with many false positives seen. Lateralizing the upper lateral cartilage (ULC) and then assessing for improvement in the obstruction sensation may provide a more accurate assessment of the nasal valve. Lateralizing the ULC with a cotton-tipped applicator or the use of a cerumen curette or similar instrument increases the nasal valve angle and, in those with a narrow angle, will provide improvement in airflow. The surgeon must also evaluate the nasal tip to see if tip ptosis is contributing to decreased airflow (Figure 44-7).
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Figure 44-6. Cottle Maneuver assessing for nasal valve component to nasal obstruction. To view this image in color, please go to www.ototext.com or the Electronic Image Collection CD, bound into your copy of Cummings Otolaryngology—Head and Neck Surgery, 4th edition.
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Figure 44-7. Patient with tip ptosis. Note the acute nasolabial angle. To view this image in color, please go to www.ototext.com or the Electronic Image Collection CD, bound into your copy of Cummings Otolaryngology—Head and Neck Surgery, 4th edition.
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Deviated Nasal Septum
Deviation of the nasal septum is a common cause of unilateral nasal airway obstruction and may follow nasal and midfacial trauma. Trauma during birth, including forceps placement or passage through a narrow pelvic canal, can cause injury that may lead to early septal deviation or to deviation that is not evident until the more active growth phase of puberty. Minor trauma sustained early in life can be easily overlooked and frequently causes microfractures of the septal cartilage; healing of these microfractures leads to bending of the cartilage away from the side of injury. When this occurs early in life, it may lead to asymmetric growth of the entire nasal structure as a result of chondrocyte growth interruption. Patients with unilateral septal deviation most often complain of nasal obstruction on the contralateral side, a phenomenon called “paradoxic nasal obstruction.”2 Patients are confused when the physician explains that the nasal passage through which the patient feels airflow moves most freely is actually the smaller of the two sides. Decongesting the nose and then testing airflow through each nostril separately or showing the patient an endoscopic photograph of each passage can help the patient to accept the explanation and understand the true problem.
Nasal Valve Angle and Nasal Valve Area
The internal nasal valve, as described above, is the narrowest portion of the nasal cavity and, therefore, any compromise of the components of the valve creates symptoms of nasal obstruction. The angle is bound medially by the septum and laterally by the inferior edge of the upper lateral cartilages and the anterior aspect of the inferior turbinate; this junction forms a trapezoidal configuration (Figure 44-8). This angle widens and narrows with nasal muscular contraction and relaxation on inspiration and expiration. The nasal valve is normally 10 to 15 degrees in Caucasian patients and wider in non-Caucasian and Asian patients.11,44 Deformities of the adjacent nasal septum or loss of anatomic support structures can predispose the valve to collapse or narrowing, thereby causing nasal airway obstruction. The upper lateral cartilage at its junction with the septum may be thickened, twisted, or concave as a result of weakness or trauma or even absent if there was prior surgery. Webs of scarred mucosa may form between the septal mucosa and the lateral nasal wall or turbinates and may narrow the valve through scar contracture (Figure 44-9). Adhesions that result in valve narrowing can create a fixed obstruction with a false-negative Cottle maneuver.
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Figure 44-8. Schematic depicting (a) the external nasal valve area and angle and (b) internal nasal valve. |
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Figure 44-9. Intra-operative photo showing scar band from the septum to the lateral nasal side wall. To view this image in color, please go to www.ototext.com or the Electronic Image Collection CD, bound into your copy of Cummings Otolaryngology—Head and Neck Surgery, 4th edition.
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The external valve is a laterally based space boxed by the pyriform aperture, the ULC and lower lateral cartilage (LLC) attachments, and the caudal septum. Obstruction as a result of external valve compromise may be a postrhinoplasty phenomenon, a result of the aging process,83 or a result of caudal septal dislocation or trauma.
Nasal Physiology (Resistance and Airflow)
On inspiration, the airstream funnels through the vestibule of the nose, squeezes through the narrow valve, and disperses in the nasal cavity.
Cadaver studies indicate that flow through the nasal valve of an adult at rest is accelerated to a linear velocity of 16 m/s. As the airstream leaves the valve and enters the nasal cavity, its velocity decelerates by a factor of four; this deceleration promotes disruption of the air by allowing it to mix in the nasal cavity.24 This is essential for the effective conditioning of inspiratory air and may aid in the ability to smell. Conditioning consists of humidification, the removal of antigenic particles, and warming.
Resistance to airflow refers to forces that impede the flow of air through a conduit. Nasal resistance is evaluated by simultaneously measuring nasal airflow and the resultant pressure gradient in the nasopharynx. Ohm’s formula integrates these measurements to calculate nasal resistance in centimeters of H2O/L/sec (or Pascals/cc/sec).
The single most important variable in nasal airflow is the diameter of the nasal passage. Dimensions and shape of the airway lumen and airflow velocity determine the magnitude of resistance to airflow. Resistance varies inversely and exponentially with lumen cross-sectional area and, because the nasal valve has the smallest lumen dimension, nasal valve resistance is very sensitive to structural or vascular displacements. In healthy noses, resistance to airflow is reduced by a third after topical decongestion, and resistance of the decongested nose is reduced by two thirds with wide alar retraction.10
Nasal resistance is modified and controlled physiologically by the erectile tissues of the nasal mucosa. The parasympathetic system controls the congestion and increased nasal secretions by vasodilatation of the sinusoids and capillaries in the mucosa, whereas the sympathetic system provides a steady vasoconstrictor tone. Nasal obstruction can be felt not only as an actual decrease in the nasal diameter but also as a feeling of obstruction even when no anatomic obstruction exists. Eliciting a medical history is clearly important, because certain medicines (e.g., exogenous hormones, oral contraceptives) can alter the neural input to the mucosa and result in mucosal hypertrophy and nasal obstruction. Turbulent airflow creates a perception of increased resistance and prevents proper clearance of air volume. In patients with severe nasal septal deviation or with septal perforations, airflow is turbulent. The nose interprets turbulent flow as low flow and thus creates a sensation of stuffiness for the patient.
The Nasal Cycle and Paradoxic Nasal Obstruction
The nasal cycle was first observed in 1927 by Heetderks,33 who described alternating turgescence of the inferior turbinates in 80% of a normal population. The turbinates in one fossa filled up while the opposite turbinates decongested. This cycle, which is controlled by the autonomic nervous system as described above, had a mean duration of two and a half hours. He further observed and documented that the turbinates in the dependent nasal fossa filled when the patient was in the lateral decubitus position. Some postulate that this alternating positional obstruction has the purpose of causing a person to turn from one side to the other while sleeping. The nasal cycle is an alternating one, with the total resistance in the nose remaining constant. In patients with a fixed septal deviation and intermittent nasal obstruction, the interplay of the nasal cycle becomes evident; the sensation of obstruction frequently mirrors the congestion phase.
Some patients with a severely deviated septum learn to subconsciously eliminate the increased resistance sensation of the obstructed side. The opposite or normal side has a variable resistance as a result of the continued fluctuations of the nasal cycle. Nasal obstruction will be perceived on the open side during the turgescent phase; this phenomenon is known as paradoxic nasal obstruction.2,45 Knowledge of this phenomenon is essential to avoid misinterpretation of the significance of unilateral enlargement of one inferior turbinate, which is often present in normal noses. Surgical correction must address the deviated septum, but it must also address the etiology of the patient’s subjective complaint of increased resistance on the side on which clinical evaluation shows a more open nasal passage. The dynamic portions of the nose (including the nostrils, vestibules, and lumen) can be narrowed due to the Venturi effect (see Figure 44-5). Identification of collapsible nasal structures is important and should be addressed during preoperative review. Surgery can then be planned to widen the angle between the upper lateral cartilages and the septum with spreader grafts or to stiffen the nasal side wall with batten or umbrella graft placement.
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Figure 44-5. A, Patient breathing through the nose at rest. B, Collapse of the nasal sidewall inclusive of nasal valve with forced inspiration To view this image in color, please go to www.oto-text.com or the Electronic Image Collection CD, bound into your copy of Cummings Otolaryngology—Head and Neck Surgery, 4th edition.
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Septal vs Turbinate Obstruction
Hypertrophy of the nasal turbinate can be *CLASSified as either mucosal or bony. Etiologies for mucosal turbinate hypertrophy include both allergic and non-allergic (vasomotor) rhinitis. The hypertrophy is generally seen bilaterally, and the sense of obstruction is relieved with topical decongestants. Surgery usually makes little difference in these patients unless mucosal redundancy is such that the nasal airway is persistently obstructed. Primary treatment would include antihistamine and decongestant use as well as topical steroid management. Surgery may be reserved for those who still complain of nasal obstruction.
Patients who smoke or who are exposed to chronic nasal irritants will frequently complain of nasal obstruction and chronic nasal drainage. Medical treatment for these patients is usually ineffective. However, these patients should not be considered primary surgical candidates until they have stopped smoking or have taken measures to avoid nasal irritants.
When mucosal decongestion does not elicit intranasal airway changes or symptomatic improvement, bony turbinate hypertrophy, along with deviation to the septum and nasal valve compromise, should be considered. This obstruction is generally constant. One theory of bony turbinate hypertrophy is that it is based on a lack of structural resistance created by the midline nasal septum during development. The bony conchal and mucosal hypertrophy is considered compensatory and can be found in the patient with a septum that is significantly deviated away from the enlarged turbinate.89 The turbinate mucosa and underlying bone enlarge into the more open nasal passage in pursuit of normalizing nasal airway resist-ance.40 Correction of the deviated septum and trimming of the enlarged turbinate are performed together to relieve obstructive complaints. Straightening only the septum without modifying the hypertrophic turbinate will result in obstruction as a result of the large turbinate on the side on which obstruction was not perceived before.
Turbinate size—along with maxillary crest and septal floor deviations—can impair overall flow patterns. Physiologic models of airflow have shown that 50% of inspired air passes along the nasal floor.40 Addressing each problem improves overall flow and decreases the obstructive sensation. Although the longevity of turbinate therapy varies,39,89 conservative turbinate surgery is a useful adjunct to include with septal surgery.
Measurement of Obstruction
The ability to objectively assess for nasal obstruction allows for appropriate treatment planning, provides a tool for outcomes analysis, and creates documentation for insurance justification or medicolegal rea-sons.12 It is astonishing for most surgeons to note the varied subjective pre- and postoperative patient complaints, which sometimes do not correlate with physical findings and objective measurements. A minor correction in some patients can elicit great improvement in the sensation of nasal obstruction and, conversely, a large structural improvement in septal anatomy may not be appreciated at all.
Acoustic rhinometry, which is an easy test for patients to tolerate and for staff to perform, provides a minimally invasive, convenient, accurate, and expeditious method of measuring dimensions of the nasal air-10,13,77,86 Acoustic rhinometry was initially used in 1977 for area measurements of the lower airway (e.g., trachea, bronchi) and was subsequently expanded to assess nasal geometry.38 The equipment delivers sound waves to the nasal cavity and then measures their reflection (Figure 44-10); the resulting wave is called a rhinogram. The nasal valve causes the first dip in the rhinogram, and the second is caused by the anterior tips of the inferior and middle turbinates (Figure 44-11). Topical vasoconstriction is applied to differentiate anatomic from physiologic causes of obstruction. With the acoustic rhinometer, the minimal cross-sectional area of the nose and the nasal airway resistance can be calculated. Acoustic rhinometric assessment of the valve can be used to determine whether valve surgery may be helpful for the correction of the patients’ complaint of nasal airway obstruction. During the assessment and treatment of nasal obstruction, which is a highly subjective sensation, it is possible to determine whether this obstructive sensation is caused by structural or dynamic nasal components. Objective postoperative improvement in nasal function can be documented by the appearance of the rhinogram. Disadvantages of this tool include the variability associated with the nostril opening and the fit of the acoustic measurement tip used for echo calculation. Furthermore, the acoustic rhinometer overlooks the contribution that narrow nostrils, a wide columella, a caudal septal deflection, or tip ptosis makes to the sensation of nasal obstruction.
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Figure 44-10. The Acoustic Rhinometer used to assess for intranasal cross sectional area. (Photo provided courtesy of Hood Laboratories.) To view this image in color, please go to www.ototext.com or the Electronic Image Collection CD, bound into your copy of Cummings Otolaryngology—Head and Neck Surgery, 4th edition. |
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Figure 44-11. Rhinogram generated by the Acoustic Rhinometer. |
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Airflow rhinomanometry, a second assessment tool, is a dynamic test of resistance to nasal airflow both before and after vasoconstriction.86 Reproducible data can be obtained to evaluate anatomic abnormalities and document surgical or medical management out.10
Although rhinomanometry is very sensitive, there does exist some margin of error that is based in test administration. Rhinomanometry provides a numeric value that indicates how hard it is to breathe through the nose. Breathing resistance of the combined cavities of the adult nose at rest greater than 3 cm H2O/L/s indicates obstruction.10 Decongestion of the nasal cavities and alar retraction enable the physician to determine the sites of mucovascular and structural components of resistance. Airflow resistance created by the adenoidal pad can also be measured in children. A complete test requires at least 20 to 30 minutes. Standard rhinometer measurements also fail to assess for nostril opening or to take into account the effect of tip ptosis on airflow.
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