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Multidisciplinary Management of Cleft Lip and Palate: : Anatomy of the Unilateral and B... Page 1 of 3 Anatomy of the Unilateral and Bilateral Cleft Lip and Nose Pathogenesis of the Cleft Lip Nasal Deformity Excerpt from Multidisciplinary Management of Cleft Lip and Palate Janusz Bardach, MD and Court Cutting, MD Peer Review Status: Internally Peer Reviewed Some of the theories of the pathogenesis of the cleft lip nasal deformity involve tissue deficiency (especially skeletal hyoplasia), malposition of the maxillary segments, asymmetry of the skeletal base and its effect on the nasal structures, the effect of muscle imbalance, and the influence of surgical procedures on secondary nasal deformities. It is helpful for the surgeon to consider these etiologic factors, particularly at the time of primary lip and nose repair when severe secondary deformities may be prevented. Careful consideration and assessment of the nasal deformity is important in selecting the appropriate surgical approach for both primary lip repair and secondary nasal reconstruction. The embryogenesis of the cleft lip deformity was originally thought to be due to a failure of fusion of the primary facial processes. This theory was attributed to Dursy1 and His2 who described the lip as having been formed from the fusion of the lateral maxillary processes with the frontonasal process. The cutaneous lip lateral to the philtral columns and the vermilion were derived from the lateral maxillary processes, whereas the central philtrum medial to the columns was due to the contribution of the frontonasal process. These processes were believed to fuse when the segments touched owing to epithelial cell death followed by healing of the processes. This idea was challenged by Veau,3 based on his study of embryos with cleft lip. Veau felt that the theories of Pohlman4 and Fleischmann5 better explained his observations. In Fleischmann's theory, the facial processes were projections of developing mesoderm under a common epithelial layer. As these processes grew closer together, a filmy epithelial bilayer lifted up as a meniscus between the processes. Further development of these mounds caused the mesoderm to penetrate the thin epithelial bilayer, resulting in the joining of what had originally been separate centers of mesodermal development. A structure like a Simonart's band is much easier to explain using this theory. The general acceptance of the theory of failure of mesodermal penetration of the epithelial bilayer compared with the theory of the fusion of the facial processes has important implications for the way in which the surgeon approaches the tissue at the time of operation. If the failure of fusion of processes theory was assumed to be correct, the surgeon might erroneously proceed on the premise that all the tissue was present and that it merely required skillful rearrangement. The Fleischmann-Veau notion, on the other hand, implied a failure of full mesodermal development, which assumes tissue deficiency. The surgeon must realize that there is tissue deficiency in the region of the cleft. This is true for the soft tissue and the facial skeleton. One of the most important defects needing correction in the secondary cleft lip nose deformity is the lack of skeletal support beneath the alar base. Anderl6 addresses the bony file:///S:/Development/Marketing/Online/Medpro%20Site/doc/vh004.htm 11/15/2011 Multidisciplinary Management of Cleft Lip and Palate: : Anatomy of the Unilateral and B... Page 2 of 3 deficiency under the alar base at the time of primary lip repair. Latham7 advocates lateral maxillary advancement on the cleft side using presurgical orthopedic treatment prior to lip repair. In this way, support for the alar base is provided at the time of lip repair. Cutting believes that the salutary effects of presurgical orthopedic treatment have a positive effect on the quality of the primary nasal correction, allowing it to be performed with minimal undermining. Avery8 reported that the nasal cartilages are deficient on the cleft side. In the clinical experience of the authors, who use an external rhinoplasty technique for the correction of severe secondary cleft nasal deformities, it is hard to discern whether or not there is any lower lateral cartilage missing: rather, it seems that it may be displaced. On the other hand, the skeletal deficiency under the alar base is often quite severe. In some patients the alar base is deficient on the cleft side. In addition to mesodermal deficiency, the alar base deficiency appears to be related to the technique of the primary surgery. This will be discussed later in the chapter. An understanding of the mechanisms that produce the malpositioning of the maxillary segments is helpful in developing further ideas that explain the cleft nose deformity. Scott9 originally proposed that the nasal septum was the primary force responsible for the downward and forward growth of the midface. In view of the more recent theories of Enlow10 and Moss,11 this idea appears somewhat simplistic. Enlow and Moss view facial growth as developing in response to the muscle forces on the facial skeleton. Although this is true, it is impossible to deny that some of the facial growth is due to the decoding of inherent genetic information. Latham12,13 described the "septopremaxillary ligament " as the structure that keeps the premaxilla attached to the anterior caudal edge of the septum (Fig. 19-1). When the premaxilla joins with the lateral maxillary segments, both mesodermal development centers are favorably affected. The lateral segments are drawn anteriorly by their attachment to the premaxilla. In a similar manner, the lateral segments draw the premaxilla backward along the caudal edge of the septum. The septopremaxillary ligament stretches as the cartilaginous septum moves forward and the premaxilla is drawn back. The anterior nasal spine is the result of the premaxilla being drawn back in this manner. King et al14 presented a three-dimensional reconstruction from serial sections of a fetus with bilateral cleft lip and palate and compared it with normal development. Figure 19-2 demonstrates the result of the lack of fusion of the premaxilla with the lateral maxillary segments. The unrestrained forward movement of the premaxilla results in excessive secondary bone deposition at the premaxillaryvomerine suture, causing a protruding premaxilla on a long bony stem. The mechanisms that produce the anterior nasal spine are not present. This allows the cartilages of the developing medial crura to be posteriorly positioned above the bone of the premaxilla, contributing to the development of a short columella and very little alar cartilage projection. In the unilateral cleft, it is useful to imagine the same forces acting on one side only. The premaxilla is overprojected on the cleft side, and the lateral maxillary segment is posteriorly positioned. The foot of the medial crus is posteriorly positioned on the cleft side relative to the noncleft side. Stenstrom and Oberg15 reported that most of the deformities of the lower lateral cartilages could be attributed to the underlying malposition of the maxillary segments. They demonstrated this by mimicking these orthopedic effects in adult cadaver noses (Fig. 19-3). By drawing the lateral foot of the lateral cartilage posteriorly and laterally, they were able to demonstrate most of the morphologic changes seen in the secondary deformities of the cleft lip nose. The foot of the medial crus was drawn posteriorly relative to the opposite side. The junction between the medial and lateral crura was pulled laterally, inferiorly, and posteriorly, resulting in the usual flattening of the dome on the cleft side. The cartilage dropped vertically, down into the nasal apex, obliterating the soft triangle. The most anterior part of the medial crus was recruited into the lateral dome where the lateral crus was usually positioned. file:///S:/Development/Marketing/Online/Medpro%20Site/doc/vh004.htm 11/15/2011 Multidisciplinary Management of Cleft Lip and Palate: : Anatomy of the Unilateral and B... Page 3 of 3 These findings will be described in further detail later in this chapter in the section on morphology of the secondary cleft lip nose deformity. Hogan and Converse16 described a similar mechanism for the production of the septal deviation typically seen in the unilateral cleft lip nose (Fig. 19-4). According to their concept, the cartilaginous septum is like the supporting strut in a tent. If the base of that support is pushed anteriorly and toward the noncleft side while the lateral part of the cleft side of the tent is drawn laterally and posteriorly, the typical septal deviation in the unilateral cleft lip nose can be explained. The authors feel that the muscle imbalance on either side of the unilateral cleft lip has great influence on the production of the secondary nasal deformity through a similar mechanism. Fara17 described the abnormal muscle insertions in the unilateral cleft lip. The medial muscle is displaced vertically and upward, inserting at the base of the columella. Contraction of the muscle pulls the base of the septum and columella toward the noncleft side. The lateral muscle is displaced vertically and upward, inserting near the foot of the alar base. Contraction of the muscle draws the ala laterally and posteriorly. The biophysical influences on the shape of the septum and lower lateral cartilages are the same as those described by Hogan and Converse, and Stenstrom and Oberg, respectively. This mechanism explains why infants with clefts of the lip only, without palatal clefts, often present severe deformities typical of the cleft lip nose. Next Page | Previous Page | Section Top | Title Page Virtual Hospital Home | Virtual Children's Hospital Home | UI Health Care Home | Outline | Search | Help | Disclaimer | Comments | E-mail This Page | Support Friends of Virtual Hospital Quick Search: Search View this page at the Virtual Hospital location nearest you: Australia | Iceland | Japan | Korea | Taiwan | United States | Venezuela Virtual Hospital International Locations: Australia | Iceland | Japan | Korea | Taiwan | United States | Venezuela [email protected] All contents copyright © 1992-2002 the Author(s) and The University of Iowa. All rights reserved. http://www.vh.org/Providers/Textbooks/CleftLipandPalate/Pathogenesis.html Modified: Thu Jul 5 09:46:38 2001 Displayed: Wed Jan 9 23:07:05 2002 file:///S:/Development/Marketing/Online/Medpro%20Site/doc/vh004.htm 11/15/2011