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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
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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.
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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.
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