Abstract
Objectives
To describe middle ear ventilation route blockage, relieved during middle ear endoscopic surgery, and to analyze its association with mastoid hypopneumatization/sclerotization.
Study design
Prospective case series with intraoperative analyses, and with a case-control computed tomographic scan comparison.
Methods
Intraoperative findings during endoscopic middle ear surgery are described. Patients with middle ear ventilation route blockage were included in the study group (22 patients), while patients without middle ear ventilation route blockage were included in the control group (16 patients). An intra-patient and inter-group comparison of evaluated mastoid pneumatization was performed from the preoperative computed tomographic scans.
Results
Middle ear ventilation route blockage was classified into three types (A, B, C) according to intraoperative findings. Intrapatient and intergroup comparisons showed that the presence of blockages of middle ear ventilation trajectories is associated with a statistically significantly higher prevalence of hypopneumatization/sclerotization of the mastoid in the study group, a typical sign of middle ear dysventilation pathologies.
Conclusions
Intraoperative evaluation of the middle ear anatomy during endoscopic surgery for inflammatory pathology allows us to clearly visualize the presence of anatomic blockages of the middle ear ventilation trajectories. These blockages might provoke a sectorial dysventilation of the middle ear, with consequent reduction of pneumatization of the mastoid. Further studies will be able to clarify to what extent selective dysventilation phenomena could be a principal factor in influencing middle ear pressure homeostasis.
1
Introduction
The study of tympanic compartments and their aeration pattern began more than one century ago with Prussak’s original work on the anatomy and aeration of Prussak’s space published in 1867 .
Then, in 1897, Sibenmann included observations of the epitympanum and tympanic folds in his book of human anatomy, according to the knowledge at the end of the 19th century . A further important study regarding the actual principles of tympanic compartments and folds is an histological study by Hammar in 1902, who described the embryological development of the middle ear pouch and folds . Many other authors have described the anatomy and development of tympanic compartments and folds because this knowledge is crucial in the understanding and treatment of middle ear disease. For the first time, Chatellier and Lemoine introduced the concept of the “epitympanic diaphragm” in 1945, upon which the modern theories of tympanic ventilation have been developed. The epitympanic diaphragm was described as the floor of the epitympanum and consisted of the incus, malleus and their folds. Those authors thought that attic and mastoid aeration would occur through a tympanic isthmus located between the anterior crus of the stapes and the tensor tympani tendon. Later on, Proctor described a posterior isthmus medially to what he called the medial incudal fold .
More recently, tympanic isthmus and middle ear ventilation patterns have been described by Palva and colleagues in several articles . They described a tympanic isthmus that arises from the tensor tympani tendon to the pyramidal process as the major pathway for mastoid cell and epitympanic ventilation . Palva and colleagues stated that the posterior isthmus described by Proctor is inconsistent because “the medial incudal fold” is in reality the incus intercrural fold, which was found to be atrophic at birth by Hammar and found only once in 37 temporal bones by Palva and Ramsay. They also suggested that the posterior tympanic isthmus is located behind the tip of the short process of the incus and that it is often small and closed by the posterior incudal fold. When open, it can have a role in the aeration of the epitympanum and the mastoid through the incudal fossa, especially when the anterior tympanic isthmus is blocked by inflammatory material. Palva and colleagues also revised Chatellier’s concept of the epitympanic diaphragm to include two other important folds: the tensor fold and the lateral incudomalleal fold . The role of these 2 folds in the physiopathology of middle ear disease is now well-known, and this knowledge is crucial in the treatment of chronic otitis, as stated by Palva et al in 2000. Fig. 1 summarizes the anatomy of middle ear folds and the 2 main ventilation routes. The same authors underlined the importance of tensor fold evaluation during middle ear surgery for chronic disease . Although exploration of the tensor fold region during middle ear surgery for chronic disease has already been established in the international literature, it is not easy to reach this region in otomicroscopy. Several approaches have been described in the international literature, but we suggest an endoscopic approach to the tensor fold in patients with attic disease, which could be exclusive or combined with the traditional microscopic approach .
In the case of an isthmus blockage caused by chronic inflammatory disease or a tympanic membrane retraction pocket and a complete tensor fold, this condition leads to inadequate ventilation of the mastoid cells and epitympanic recess. Middle ear pressure seems related not only to a functioning Eustachian tube but also to transmucosal gas exchange through the mastoid mucosa. The mucosal gas exchange is related to the degree of mastoid pneumatization , which begins on the 33rd gestational week, continuing up to 8–9 years of age . Because of these 2 gas pressure regulation systems, even if the Eustachian tube is functioning, an isthmus blockage could impair ventilation of the mastoid cells causing sclerotization of the mastoid. It is not clear whether chronic middle ear disease leads to inadequate mastoid pneumatization or conversely a sclerotic mastoid leads to chronic middle ear disease .
The aim of this study is to describe the possible kinds of anatomic blockage of the middle ear ventilation trajectories identified during endoscopic surgery procedures and to understand if those alterations could be associated with anomalous mastoid pneumatization, a classic sign of middle ear dysventilation problems.
2
Materials and methods
From March 2007 to February 2008, 57 patients affected by cholesteatoma underwent a surgical procedure at our Otolaryngology Department. The setting was a tertiary referral university hospital. All patients underwent tympanomastoid surgery with intraoperative use of the endoscope, and all procedures were recorded and stored digitally. The anatomic condition of the middle ear, with possible blockages and the integrity of the folds were accurately described in the operative report, and noted in a database soon afterward the operations. We also described the condition of the attical mucosa and the condition of the mucosa of the mesotympanic and protympanic spaces. In the case of missing data, the surgical procedures were reviewed using the recorded files stored digitally.
2.1
Surgical instrumentation and surgical procedure
The instrumentation consisted of 3-mm-diameter, wide-angle (20-cm length), 0° and 45° sinuscopes (Karl Storz, Tuttlingen, Germany). The video equipment consisted of a 3-chip video camera (Karl Storz) and 20-in high-definition monitor; all procedures were recorded digitally on a hard disk (Karl Storz). During the surgical approach to the middle ear, we introduced the endoscope into the middle ear and examined the tympanic isthmus and the tensor fold area to understand the epitympanic diaphragm of the upper unit of all our patients. This transcanal lateral approach permitted a good exposure of the tympanic isthmus. Endoscopic examination of the tympanic isthmus was possible using the 3-mm 0° and 45° endoscopes inserted into the tympanic cavity; we could explore all of the large tympanic isthmus between the medial part of the posterior incudal ligament posteriorly and the tensor tendon anteriorly. The 0° endoscope allowed us to magnify the space between the incudostapedial joint and cochleariform process with the tensor tendon (Proctor’s anterior isthmus), whereas, after posterior atticotomy, the 45° endoscope permitted us to magnify the space between the pyramidal process and the short process of the incus (Proctor’s posterior isthmus). When mastoidectomy was required, we used the 45° endoscope through the mastoid cavity to obtain a posterior view of the tympanic isthmus. Endoscopic examination of the tensor fold area was possible by two kinds of approach using a 3-mm 45° endoscope as follows:
- •
Inferior approach: the endoscope was inserted into the protympanic region; we identified the Eustachian tube and supratubal recess; this position allowed us to obtain a good view of the inferior edge of the tensor fold;
- •
Superior approach: we performed an anterior atticotomy exposing the anterior epitympanic space; this procedure allowed us to obtain a good view of the superior edge of the tensor fold.
The study and control groups were selected prospectively as follows.
2.2
Study group
Patients affected by an anatomic blockage of the middle ear ventilation trajectories, visible at the endoscopic evaluation during the surgical approach, were included in the study group. On the other hand , patients affected by a disease involving the protympanic, the mesotympanic, and the retrotympanic regions, or patients who had already undergone middle ear surgery and with bilateral pathology of the middle ear, were excluded from the study group. Twenty-two patients of 57 were finally included in the study group.
2.3
Control group
Subjects affected by middle ear disease who underwent a surgical procedure, with the absence of anatomic blockage of the middle ear ventilation trajectories visible at the endoscopic evaluation during surgery, were included in the control group; patients who had already undergone middle ear surgery in the past and patients with bilateral pathology of the middle ear were excluded from the control group. Sixteen patients of 57 operated for middle ear disease were finally included in the control group.
All 38 patients recruited in our study had a preoperative high-resolution computed tomographic scan of the temporal bone with axial projections obtained with sequential 1.0-mm slices performed from the arcuate eminence to the jugular fossa. The radiological mastoid pneumatization degree was reviewed in all 38 patients, and classified into 3 types, according to a modified CT scan classification by Görür et al :
Type 1 (normal pneumatization): the mastoid pneumatization reaches the mastoid tip, zygomatic, perisigmoid and periantral regions; aditus ad antrum is open/present;
Type 2 (hypopneumatization): the mastoid pneumatization is present only in antral, and periantral regions; aditus ad antrum is present/open;
Type 3 (sclerotic): the mastoid pneumatization is totally absent; aditus ad antrum is present/open.
This classification has been applied to both ears (the pathologic and the healthy ear), both in the study group and the control group to assess possible differences intra-patients and intergroups.
Mastoid pneumatization data were compared using Fisher exact test ( χ 2 analyses was not applicable because of insufficient data). P < .05 was considered statistically significant.
2
Materials and methods
From March 2007 to February 2008, 57 patients affected by cholesteatoma underwent a surgical procedure at our Otolaryngology Department. The setting was a tertiary referral university hospital. All patients underwent tympanomastoid surgery with intraoperative use of the endoscope, and all procedures were recorded and stored digitally. The anatomic condition of the middle ear, with possible blockages and the integrity of the folds were accurately described in the operative report, and noted in a database soon afterward the operations. We also described the condition of the attical mucosa and the condition of the mucosa of the mesotympanic and protympanic spaces. In the case of missing data, the surgical procedures were reviewed using the recorded files stored digitally.
2.1
Surgical instrumentation and surgical procedure
The instrumentation consisted of 3-mm-diameter, wide-angle (20-cm length), 0° and 45° sinuscopes (Karl Storz, Tuttlingen, Germany). The video equipment consisted of a 3-chip video camera (Karl Storz) and 20-in high-definition monitor; all procedures were recorded digitally on a hard disk (Karl Storz). During the surgical approach to the middle ear, we introduced the endoscope into the middle ear and examined the tympanic isthmus and the tensor fold area to understand the epitympanic diaphragm of the upper unit of all our patients. This transcanal lateral approach permitted a good exposure of the tympanic isthmus. Endoscopic examination of the tympanic isthmus was possible using the 3-mm 0° and 45° endoscopes inserted into the tympanic cavity; we could explore all of the large tympanic isthmus between the medial part of the posterior incudal ligament posteriorly and the tensor tendon anteriorly. The 0° endoscope allowed us to magnify the space between the incudostapedial joint and cochleariform process with the tensor tendon (Proctor’s anterior isthmus), whereas, after posterior atticotomy, the 45° endoscope permitted us to magnify the space between the pyramidal process and the short process of the incus (Proctor’s posterior isthmus). When mastoidectomy was required, we used the 45° endoscope through the mastoid cavity to obtain a posterior view of the tympanic isthmus. Endoscopic examination of the tensor fold area was possible by two kinds of approach using a 3-mm 45° endoscope as follows:
- •
Inferior approach: the endoscope was inserted into the protympanic region; we identified the Eustachian tube and supratubal recess; this position allowed us to obtain a good view of the inferior edge of the tensor fold;
- •
Superior approach: we performed an anterior atticotomy exposing the anterior epitympanic space; this procedure allowed us to obtain a good view of the superior edge of the tensor fold.
The study and control groups were selected prospectively as follows.
2.2
Study group
Patients affected by an anatomic blockage of the middle ear ventilation trajectories, visible at the endoscopic evaluation during the surgical approach, were included in the study group. On the other hand , patients affected by a disease involving the protympanic, the mesotympanic, and the retrotympanic regions, or patients who had already undergone middle ear surgery and with bilateral pathology of the middle ear, were excluded from the study group. Twenty-two patients of 57 were finally included in the study group.
2.3
Control group
Subjects affected by middle ear disease who underwent a surgical procedure, with the absence of anatomic blockage of the middle ear ventilation trajectories visible at the endoscopic evaluation during surgery, were included in the control group; patients who had already undergone middle ear surgery in the past and patients with bilateral pathology of the middle ear were excluded from the control group. Sixteen patients of 57 operated for middle ear disease were finally included in the control group.
All 38 patients recruited in our study had a preoperative high-resolution computed tomographic scan of the temporal bone with axial projections obtained with sequential 1.0-mm slices performed from the arcuate eminence to the jugular fossa. The radiological mastoid pneumatization degree was reviewed in all 38 patients, and classified into 3 types, according to a modified CT scan classification by Görür et al :
Type 1 (normal pneumatization): the mastoid pneumatization reaches the mastoid tip, zygomatic, perisigmoid and periantral regions; aditus ad antrum is open/present;
Type 2 (hypopneumatization): the mastoid pneumatization is present only in antral, and periantral regions; aditus ad antrum is present/open;
Type 3 (sclerotic): the mastoid pneumatization is totally absent; aditus ad antrum is present/open.
This classification has been applied to both ears (the pathologic and the healthy ear), both in the study group and the control group to assess possible differences intra-patients and intergroups.
Mastoid pneumatization data were compared using Fisher exact test ( χ 2 analyses was not applicable because of insufficient data). P < .05 was considered statistically significant.
3
Results
3.1
Study group
The study group consisted of 22 patients of which 6 patients were female and 16 were male; the mean age of the group was 37 (+/− 14.2 SD).
3.1.1
Pathology and symptoms
In 22 patients affected by isthmus block, we found the following pathology:
- •
9/22 subjects were affected by attic cholesteatoma; in all these patients, the cholesteatoma sac was present in the attical-antral area without mesotympanic, protympanic and hypotympanic involvement;
- •
8/22 subjects were affected by retraction pocket of the pars flaccida; in these patients, 6 presented an epitympanic compartment without disease while in 2 patients, we found a cholesterol granuloma in the anterior epitympanic space;
- •
5/22 subjects were affected by chronic inflammation of the epitympanic compartment; these patients presented granulation tissue in the attical space with or without involvement of the incudomallear joint; in 2 patients, this inflammatory tissue was associated with attical-mastoid mucocele.
In all 22 subjects, the protympanic, mesotympanic and hypotympanic mucosa was normal, and the endotympanic lumen of the Eustachian tube was without disease, as the selection criteria required. Eighteen of the 22 patients presented chronic otorrhea before surgery.
3.1.2
Intraoperative endoscopic findings
Analyzing the anatomical structure that separates the epitympanic space from the mesotympanum (tympanic isthmus and tensor fold area), in all 22 subjects, a tree-type epitympanic diaphragm or attical aeration pattern was found:
- •
Type A ( Figs. 2 and 3 ): 14/22 patients had a blockage of the isthmus associated with a complete tensor fold. This kind of blockage was present in 6 patients who showed selective retraction pockets without pathologic tissue in the epitympanic space, 3 patients presented epitympanic inflammatory tissue in the attic area, and 5 patients presented a limited attic cholesteatoma sac.
