Clefts of the lip, palate, or both have been described for several species, including dogs,1–3 cats,4 cattle,4,5 horses,6 and people.7,8 These congenital malformations are important because of the degree of dysfunction involved,9 the associated morbidity,10 the complexity of surgical repair,11,12 and their frequency (1.5 to 3.2 cases/1,000 live human births; 1.1 cases/1,000 live Beagle births).9 Although the etiology is complex and not completely understood,7 the embryological events involved appear to be well conserved among mammalian species.13
An important aspect of CLs, CPs, and CLPs is defect morphology.7,8,14–18 From a clinical standpoint, defect morphology is important for surgical planning and may influence the outcome.17 From a scientific perspective, the systematic documentation and classification of defect morphology is important for the conduction of genetic, embryological, or clinical research.7 Defect morphology with respect to CLs, CPs, and CLPs can be complex and can vary among affected individuals. In people, > 150 defect configurations have been estimated as possible on the basis of the anatomic structures involved.19
Many classification systems for oral cleft defects have been proposed over the past few decades in human medicine, but none have been adopted universally.16,20–23 Some are based on the embryological point of defect formation; namely, the primary palate (ie, lip and alveolus) forms before the secondary palate (ie, hard and soft palate). Others are based on the anatomic structures involved (ie, lip, alveolus, hard palate, and soft palate).
Because of their simplicity, embryological systems are commonly used for epidemiological research and clinical coding purposes.24 The simplest approach is to classify defects as CL, CP, or CLP (when both develop simultaneously). However, for surgical applications and phenotype documentation when conducting genetic research, more detailed (and more complex) anatomic documentation is required.
One limitation of many classification systems is the lack of severity indicators. In general, clefts of the lip, alveolus, and hard palate can develop unilaterally or bilaterally.25 Moreover, clefts can develop as total or subtotal in any given anatomic structure and as a microform (ie, mucosal defect with intact underlying functional layer).25 Furthermore, defect morphology and maxillofacial growth and appearance are not always symmetric or harmonious, and the vomer and septum may be deviated or malformed.25,26 Although some classification systems have been developed with an attempt to incorporate these features, no system has been established that is sufficiently versatile yet simple enough for reproducible application in clinical practice and research.
A widely used classification system in use since 1985 is known as LAHSHAL.25,27 In this system, each letter represents an anatomic location (ie, L represents the lip, A represents the alveolus, H represents the hard palate, and S represents the soft palate). The palindromic nature of this term allows recording the affected side (ie, letters to the left of the S represent defects on the right side and vice versa). Because soft palate defects only occur at the midline, a single middle letter is assigned to record this anatomic area. In regard to extent, upper- or lowercase letters are used to represent complete or incomplete defects, respectively. Finally, an asterisk can be added to lowercase letters whenever a microform defect is present. The anatomic form of a defect is thus reflected by the sequence, order, and type of characters recorded for each individual. One of the disadvantages of this system is that it fails to account for shape or relative width of the defects, any abnormalities of the vomer, or asymmetry of facial structures.
Historically, detailed documentation of oral cleft defect morphology was achieved by means of radiography, casts, or both in live patients26 or by histologic examination of cadaveric specimens.25 Current approaches involve the use of CT, CBCT, and other advanced imaging modalities for both medical and scientific purposes.9,28
Defect morphology of CLs, CPs, and CLPs in people has been extensively described. Conversely, in dogs, most reports2,4 involve embryological classification or provide minimal detail regarding the defects. Understanding defect morphology in dogs would help to enhance the quality of care and the conduction of canine or translational research into oral cleft defects. The purpose of the study reported here was to systematically document the morphology of congenitally acquired CLs, CPs, and CLPs in dogs. We hypothesized that defect morphology would vary among affected dogs and that the morphological variations would resemble those reported in human medicine.
The authors declare that there were no conflicts of interest. The authors thank Nicholas Roman for his assistance in formatting the tables.
Cleft lip and palate
Aquilion LB, Toshiba American Medical Systems, Tustin, Calif.
GE Lightspeed16, GE Medical Systems, Cleveland, Ohio.
NewTom 5G, NewTom, Verona, Italy.
Picture Archiving Communications System, Carestream, Rochester, NY.
Invivo5, Anatomage, San Jose, Calif.
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