Epidemiological and clinical evaluation of patients with a cleft in lower saxony Germany: a mono-center analysis

Cleft lip and/or palate (CL/P) are not only among the most common orofacial deformities but are also among the most common congenital malformations [1, 2]. The prevalence of CL/P varies from 1 in 500 to 1 in 2500 births depending on sex, socioeconomic status, and geographic location [3, 4]. In European countries, a prevalence of 1:1000 is assumed [2]. However, no data for individual regions, especially Germany, exist. Furthermore, diverse phenotypes of CL/P occur at different frequencies, and complete CLP is found in 40–50% of patients, while CL±A and CP account for 20–25% and 30–35%, respectively. In the case of a unilateral cleft, the left side is more often affected than the right side [5]. Girls are generally less affected than boys by cleft lip with or without cleft palate [1, 6], while some authors assume that they are at higher risk of cleft palate only [7].

Cleft formation is proposed to be multifactorial, involving genetic and environmental factors, and a positive family history of CL/P increases the risk of cleft manifestation with different degrees of recurrence based on the severity and type of cleft [8, 9]. In addition to heredity, maternal exposure to drugs, infections, or poor nutrition affect the occurrence of CL/P and may contribute to one-third of CL/P cases [4, 10]. For example, a well-known exogenous factor that increases the risk for CL/P is maternal smoking, which leads to a 1.5 times higher likelihood of having offspring with CL/P. Further external factors include vitamin deficiencies (folic acid and vitamin B), oxygen deficiency, hypervitaminosis (vitamin A), viral infections, medications (e.g.: cortisone, anticonvulsants, and cytostatics), smoking, drugs, ionizing radiation, chemicals, alcohol, and stress [11‐15].

Approximately 30% of CL/P cases are associated with congenital malformations and syndromes. Frequent birth defects accompanying CL/P include musculoskeletal, cardiovascular, and central nervous system defects [2, 16].

These numbers illustrate the complex epidemiological and clinical profiles of CL/P and emphasize the need for good interdisciplinary cooperation and the importance of specialized cleft centers [17, 18]. Thus, at the University Medical Center Goettingen, the cleft team consists of experts in the fields of cranio-maxillofacial surgery, orthodontics, otolaryngology, speech therapy, human genetics, prosthodontics, and conservative dentistry. In some cases, corrective surgery, i.e., lip revision, fistula closure, palate re-repair, and pharyngeal surgery, becomes necessary. However, corrective surgery is regarded as a burden on the patients and their families and should be avoided whenever possible. The likelihood of performing corrective surgery varies widely among different cleft centers, and the occurrence of lip revision ranges from 5% to 60% [19]. This could be due to different thresholds for corrective surgery but may also be based on the applied concepts in primary cleft care. In total, there are 201 cleft centers in Europe with 194 different treatment concepts[20, 21], and information on the rate of corrective surgeries by single centers is missing.

To date, there are few studies on the epidemiological and clinical profiles of individual regions in Europe, especially Germany. Therefore, the aim of the present study was to provide a comprehensive epidemiological and postoperative clinical overview of cleft care in the geographic area of Southern Lower Saxony. As the characterization of patients with clefts is essential for professionals involved in cleft care and for health services, we analyzed the patient collective of a single center with regard to their sex, clinical manifestation of the cleft, family and pregnancy history, comorbidities, and need for corrective surgery.

This observational study was approved by the Ethics Committee of the University Medical Center Goettingen (21/4/20) in accordance with the Declaration of Helsinki. In a retrospective evaluation from 2001 to 2019, the records of all patients with a cleft who received surgery at the University Medical Center Goettingen were analyzed. Each patient was treated according to a consistent protocol (for details, see Table 1) and was seen once a year for follow-up. In this appointment, the current treatment needs were assessed and discussed with the patients and their parents. This cleft consultation was held once a month with the interdisciplinary team.

A total of 466 patients visited the cleft consultation center within the study period. The inclusion criteria were all patients with an orafacial cleft formation; the exclusion criterion was the absence of such a malformation. After record screening, many patients presented at the consultation with the suspicion of a cleft, which was not confirmed and was therefore not included in the analysis. After record screening, 404 patients were included as real patients with orofacial clefts in the analysis.

Written file documentation was evaluated by one person and spot-checked by a second person. The written records were systematically evaluated, and their sex (male, female), cleft type (CL, CLA, CLP, CP, facial cleft), sidedness (left, right), laterality (unilateral, bilateral), family and pregnancy history, comorbidities, the presence of a syndrome, and the number of surgeries, including corrective surgeries, were documented in a database using MS Access (Microsoft, Washington, USA). The determination of the cleft localization occurred at the time of the initial clinical presentation and documentation. The clarification of the syndrome was determined according to the documentation of the case, where all physician’s reports or treatment reports of the records were reviewed. The abnormalities during pregnancy and the term premature birth were determined by interviewing the parents or accompanying relatives.

Secondary surgeries were interventions on previously operated cleft regions. Here, a distinction must be made between interventions planned as part of the overall surgical concept (e.g., nasal Columella lengthening in patients with previously operated bilateral cleft lips and palates and secondary bone grafting) and corrective operations to improve the aesthetic and functional results in the case of unsatisfactory results of primary surgery.

The present study provides the epidemiological and clinical data of patients with CL/P of a single center in lower saxony Germany investigated between 2001 and 2019. In total, the side could not be determined in 7 patients; however, these patients were still taken into account because they are meaningfully concerning the evaluation of the clinical profile apart from cleft side manifestation. With a prevalence of 1 patient with a CL/P in every 890 live births, the observed prevalence was slightly higher than the expected prevalence of 1 in every 1000 births for European countries. However, the data on prevalence differ widely and show geographic variations [2, 15]. In addition to the calculation of prevalence used here, there are other studies that provide extensive registry data, for example, in the Scandinavian countries. These are superior to the present survey but do not represent the same specific geographic area [22, 23].

The global trend of higher CL/P occurrence in boys was confirmed in the present study sample. Subgroup analysis revealed that this effect was caused by CLP, while CL, CLA, and CP were distributed equally between the sexes. In accordance with the existing literature, in unilateral cases, the left side was more often affected than the right side, and unilateral CL/P was more frequently observed than bilateral CL/P [10, 24‐29].

In the study population, CLP occurred most frequently, followed by CP, CL, and CLA. This result is equal to the previously reported prevalence [10] but may also be affected by local factors, as exogenous and endogenous influences may vary for different geographic locations. In contrast, a Colombian study found CL to be the most common type of cleft [30]. Furthermore, genetic factors play a crucial role in CL/P occurrence, and a positive family history increases the risk of cleft manifestation [8, 31‐34]. Compared to the international literature, the percentage of patients with a positive family history in the present study sample was rather low. However, a hereditary component in the development of cleft formation is undeniable even though the exact genetic mechanism is not yet fully understood, and more than 50 genes have been described to be associated with non-syndromic patients with a CL/P [35]. For instance, T-box and MSX genes are believed to play a major role in palatogenesis[36‐38]. Interestingly, these gene families are also involved in heart development [39‐42]. Therefore, genetics might explain the high co-occurrence of CL/P and heart disease observed in the presented sample. However, further contributing factors must be assumed. For example, stressful life events during pregnancy may be associated with higher risk of CL/P and congenital heart diseases [43‐45]. The maternal stress activates the hypothalamus-pituitary-adrenal axis, increases glucocorticoid production, and might cause gene-environment interactions. Mostaka et al. identified the stress-related genes SLC6A4, TPH2, and SERPINA6 to increase the risk of having a child with orofacial cleft [46].

We observed inheritance primarily from the maternal side, which could lead to the assumption that clefts are caused by the maternal genotype working through the prenatal environment. However, this has been disproved, and there is some evidence that the fetal genes themselves make the major genetic contribution to CL/P [47]. Moreover, other epidemiological studies showed no difference in family recurrence between affected mothers and fathers [48] or a pronounced hereditary component from the paternal side [33, 49, 50].

Furthermore, blood relationship between parents is seen as a risk factor for the development of CL/P. Kin marriages, which are practiced in some cultures, underline the correlation of cultural and genetic influences on CL/P prevalence [51]. However, as genetics, genomics, and epigenetics contribute to cleft formation, the etiology of CL/P is too complex to be explained by inheritance only. Epigenetic-wide association studies provided evidence that DNA methylation, histone modifications, and non-coding RNA might explain the missing heritability For multifactorial inheritance, it is assumed that the risk of transmission to subsequent generations decreases as the degree of relatedness decreases [52]. The distribution of the degrees of relatedness in our patient cohort supports this hypothesis.

Preterm birth was the most common abnormality during pregnancy in our study population, and a higher prevalence of preterm births in mothers of patients with a cleft was observed previously [8, 10]. Shehan et al. (2021) reported a 1.9 times higher likelihood of being born with CL/P for preterm infants than for full-term infants [53]. This correlation is not surprising, as there are several risk factors that contribute to both CL/P and prematurity, such as maternal smoking or substance abuse. However, an interactive pathogenesis behind this correlation has not been described [53]. Therefore, prematurity and CL/P are probably caused independently from each other.

A similar approach applies for the association of CL/P and syndromes or. This is reflected by the fact that the percentage of abnormalities during pregnancy in syndromic patients with CL/P was twice that in patients with non-syndromic clefts.

In the present study population, syndromic CL/P accounted for 10.4% of all orofacial clefts and thus falls into the wide range of reported percentages of syndromic cleft formation in the literature, which varies from 4.8% to almost 30% [10, 54, 55].

At least 487 syndromes may be associated with cleft formation [56]. In Goettingen, 15 different syndromes and syndrome-like complexes were observed during the study period.

The Robin sequence was found most frequently, in accordance with the literature [56‐58].

One-third of our patients displayed at least one comorbidity with a higher probability when the palate was also affected by the cleft. The most common comorbidities were heart diseases followed by respiratory tract diseases and language development disorders. These findings were similar to other epidemiological studies [8, 10, 54, 59] and support the need for the comprehensive pediatric assessment of infants with a CL/P, especially with regard to congenital heart diseases, which occur in 3.9 to 23.9% of all patients with a CL/P. It must be mentioned here that no distinction was made between syndromic and non-syndromic Robin sequences and a direct conclusion from the sequence to an expected comorbidity, which could be explained by a syndrome is difficult. The observation that patients with palate involvement are at higher risk for other organ abnormalities and comorbidities suggests that a relationship between the timing of cleft appearance and genes responsible for organ development requires further exploration to better understand the development of clefts [60].

In addition to the treatment strategy, the skills and experience of the surgeon is essential for a satisfactory rehabilitation of patients with CL/P. There are 194 different concepts at 201 cleft centers in Europe, which underscores the importance of tradition at the respective center [21]. Consequently, several surgical techniques for lip and palatal closure have been postulated. In our center, surgical closure of the lip is performed using the Tennison and Randall technique supplemented by simultaneous plastic surgery according to Axhausen in the case of ridge involvement [61].

For palate closure, our center differentiates between isolated CP and CLP. In the case of CP only, the cleft palate is repaired in one-step with a pedicle flap plasty according to Veau [62]. In the case of CLP, palate closure is a two-step process after lip repair. First, Pichler plasty is performed to close the hard palate [63]. After 3 months, analogous to CP only, the soft palate is closed using the pedicle flap-plasty according to Veau.

The rate of corrective surgery in the present study was 10.6%, and regarding the subcollective of patients who received primary surgery according to the University Medical Center Goettingen treatment protocol, the rate was 2.2% and therefore lower compared to other studies, which reported corrective surgeries in 33%, 56.9%, and 69.3% of all treated cases [64‐66].This low rate can reflect the center’s restrictive approach regarding corrective surgery and might provide an argument for a stringent treatment protocol. However, surgical and clinical experience plays a major role in cleft surgery, not only the capacity of the surgeon itself but of the whole team can improve the outcome [67, 68].

There are some limitations to this study, including that the data were acquired retrospectively. The analysis includes all patients presented to our center since the introduction of the treatment concept. Consequently, all age groups were represented in the patient collective. Due to the concept, the primary operations of the cleft for complete closure were all completed within the first 15 months of life. Certainly, this is a patient population in flux, as patients who presented as newborns in 2019 had not completed 18 years of life by the time data collection was completed, and further surgical interventions were pending in accordance with the treatment plan. Thus, interdisciplinary care continues through the consultation for all patients who are not yet adults. Furthermore, medical records can contain errors and be incomplete. Even though most of the documentation was accomplished by the same surgeon, some records were completed by his representative. Moreover, the results are very specific for the area of Lower Saxony in Germany and may not be generalizable to other populations. However, this focus was chosen on purpose because data for this geographic area were missing.

In summary, the epidemiological and clinical characteristics of patients with cleft in Lower Saxony Germany are consistent with the literature. The large number of comorbidities calls for an interdisciplinary approach with special attention to the potential presence of cardiovascular disease in non-syndromic patients with a CL/P. A stringent treatment protocol and multidisciplinary approach is essential in oro-facial cleft care.