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Value of preoperative imaging in the diagnostics of isolated metopic suture synostosis: A risk–benefit analysis
Journal of Plastic, Reconstructive & Aesthetic Surgery (2012) 65, 1246e1251
Value of preoperative imaging in the diagnostics of isolated metopic suture synostosis: A riskebenefit analysis Michael Engel*, Gregor Castrillon-Oberndorfer, Juergen Hoffmann, Christian Freudlsperger Department of Oral and Maxillofacial Surgery, University Hospital Heidelberg, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany Received 7 November 2011; accepted 26 March 2012
KEYWORDS Craniosynostosis; Metopic suture; Trigonocephaly; Computed tomographic; MRI
Summary Radiographic evaluation including plain radiographies and computed tomographic (CT) scans are considered as a necessary tool for diagnosis of craniosynostosis. As recently concerns about harmful effects of ionising radiation in children have been raised, some authors have suggested the use of magnetic resonance imaging (MRI) as a helpful alternative in preoperative imaging of patients with isolated metopic synostosis. Besides confirming the diagnosis of trigonocephaly, MRI is the superior technique for the evaluation of underlying brain anomalies. However, if the benefit of preoperative imaging justifies possible side effects is still discussed controversially. Hence, this study investigated the value of preoperative imaging for the diagnosis of isolated synostosis of the metopic suture compared to a sole clinical examination. In a series of 63 cases with isolated metopic craniosynostosis operated at the Department of Oral and Maxillofacial Surgery, 48 (76.2%) patients received additional radiography or MRI investigation, while in 15 (23.8%) patients the diagnosis was based on clinical examinations only. In all patients, diagnosis was confirmed intra-operatively by a fused metopic suture. CT scans with three-dimensional reconstruction (12.5%) or plain radiographs (39.6%) did not provide any additional benefit for the diagnosis or the surgical treatment. In 23 patients (47.9%), MRI showed the typical soft-tissue alterations like triangular brain deformation in the frontal area. Besides these findings, no brain or other underlying anomalies were diagnosed which had required any additional treatment. The incidence of underlying brain abnormalities in isolated metopic synostosis seemed not to be different from that of the general population.
* Corresponding author. Tel.: þ49 6221 5638811; fax: þ49 6221 564222. E-mail address: [email protected] (M. Engel). 1748-6815/$ - see front matter ª 2012 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.bjps.2012.03.038
Preoperative imaging in isolated metopic suture synostosis
1247
As the characteristic clinical manifestations were sufficient for an accurate diagnosis of isolated metopic synostosis, and with respect to the biological effects of ionising radiation and risks of sedation especially in infants, preoperative imaging should be reduced to a minimum. ª 2012 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.
Single-suture synostosis is the most common form of craniosynostosis, with a prevalence of approximately one in 2500 live births.1 Among the isolated synostoses, fusions of the sagittal, coronal and metopic sutures are the most frequent; however, the exact incidence of isolated metopic synostosis is discussed controversially with an estimated incidence of 0.3e6 per 1000 to 15 000 live births.2e5 Premature closure of the metopic suture results in a triangular head shape, called ‘trigonocephaly’, which features the clinical hallmarks of a keel-shaped forehead, hypotelorism, epicanthus and temporal narrowing with an associated abnormality of the supraorbital rim. Besides that, trigonocephaly can also be presented with only mild clinical manifestations including slight prominence of the metopic ridge.4,6e8 Although these characteristic clinical appearances should point the way to the right diagnosis, plain radiographs of the skull, computed tomographic (CT) scans and three-dimensional (3D) reconstructions of CT scans are still recommended as necessary tools for both the diagnosis of trigonocephaly, and the preoperative planning.8e10 In the majority of patients, standard skull radiography provides all essential preoperative information, including ossification of the metopic suture and the anterior fontanel, hypotelorism and a broadening of occipital region.11 In addition, CT scans and, in particular, 3D CT reconstructions demonstrate detailed information about the cranial bony anatomy, especially the basal sutures and synchondroses. Furthermore, some authors demand CT diagnostic for the detection of associated brain abnormalities.12 However, the diagnostic benefit of radiographic examinations should be carefully weighed out against the biological effects of ionising radiation especially in infants.8,9,13e17 To avoid radiographic examination in childhood, MRI diagnostic can be a helpful tool in preoperative imaging of patients with isolated sagittal synostosis. Besides confirming the diagnosis of trigonocephaly, MRI is the superior technique for the evaluation of underlying brain anomalies. Hence, the value of preoperative imaging as a diagnostic tool in isolated metopic synostosis is still under discussion. The aim of this study was to evaluate if clinical examination without additional imaging is sufficient for the diagnosis of single metopic synostosis and if the diagnostic surplus justifies possible side effects of ionising radiation or sedation in infants.
Material and methods For this retrospective non-blinded case review study, the study population consisted of all patients with an isolated metopic craniosynostosis who underwent surgery between January 1998 and December 2010 in the Department of Oral
and Maxillofacial Surgery at the University Hospital Heidelberg. All review procedures were in strict accordance with general guidelines and an approved application on file at our institutional review board. Patients were selected on the basis of their final, not the initial, diagnosis. Only children with primary non-syndromic metopic craniosynostosis were considered eligible for this study. Children with syndromal or secondary metopic craniosynostosis were excluded. Medical records of all patients were reviewed in their entirety. The following information was retrospectively collected and reviewed from the database: patient’s demographic details, the diagnosis following clinical examination by experienced craniofacial surgeons, results of the radiologic evaluation if conducted, details of the operative procedure as noted by the surgeon and alteration of the diagnosis following the radiologic examination or the operative procedure. All patients received their clinical examinations exclusively by one of our three craniofacial surgeons, who ranged in experience from 4 to 15 years. Radiological examinations were evaluated by both one craniofacial surgeon and one experienced neuroradiologist from the Department of Neuroradiology at the University Hospital Heidelberg. Furthermore, patients who received CT scan or MRI were investigated for intracranial abnormalities.
Results From January 1998 to December 2010, a total of 85 children were identified from the medical records with the diagnosis of an isolated metopic synostosis. Twenty-two patients were treated conservatively, because clinical characteristics were less pronounced or surgery was declined by the parents. Hence, a total of 63 patients included 48 (76.2%) boys and 15 (23.8%) girls, underwent a surgical procedure for isolated non-syndromatic metopic craniosynostosis at our Department of Oral and Maxillofacial Surgery. The median age at referral was 5 months (range 1e12 months). At the first physical examination, all patients showed characteristic manifestations of trigonocephaly including significant deformity of the supraorbital ridges and temporal regions, with hypotelorism (Figure 1). Surgery was performed at a median age of 11.2 months (5e14 months). All these children underwent craniofacial reconstruction, according to the standardised fronto-orbital advancement especially applied to trigonocephaly. In all cases, the suspected synostosis of the metopic suture was confirmed by the surgeons. Preoperative imaging has been performed in 48 (76.2%) children (Figure 2). Standard skull radiographs were obtained in 19 (39.6%) patients; in a majority of these cases radiography had been performed by the referring physician. The diagnostic accuracy of plain radiograph studies was 100%. Six children (12.5%) had a CT scan of the head in the preoperative period; all had been performed by
1248
M. Engel et al.
Figure 1 Six month old boy with typical aspect of trigonocephaly (pre-operatively). Clinical hallmarks of metopic synostosis including the keel-shaped forehead, hypotelorism and epicanthus frontal (A), profile (B). Corresponding three-dimensional reconstructions of computed tomographic scans showing complete fusion of the metopic suture (C).
the referring physician prior to craniofacial consultation. CT was confirmatory of the diagnosis in all six patients. In none of the patients who received CT scans, intracranial abnormalities were found, which could have influenced surgical planning. In 23 patients (47.9%), MRI was conducted. The accuracy in defining bony abnormalities of MRI was inferior compared to CT, but was sufficient to confirm the diagnosis of trigonocephaly, as all patients in our study showed the typical soft-tissue alterations like the triangular brain deformation in the frontal area. Besides that, no malformations of the cerebrum, such as, midline anomalies, lesions of the parenchyma, intracranial herniation, hydrocephalus or
changes in intracranial morphology were found in our series (Figure 3). In addition, no alterations were made to the clinical decisions regarding the timing of surgery. Fifteen (23.8%) children with the typical clinical hallmarks of trigonocephaly had no preoperative imaging. In all of these cases, the diagnosis of metopic synostosis was confirmed intra-operatively (Figure 4).
Discussion The characteristic clinical features of single-sutural craniosynostosis permit a confidential clinical diagnosis.
Figure 2 Structure of study population. In 15 patients, diagnosis of metopic synostosis was made by clinical examination with a 100% accuracy as proofed by intraoperative findings. In 48 patients diagnosis was confirmed by Standard skull radiographs or computed tomographic (CT) scans. No intracranial abnormalities have been detected in 29 patients who received a pre-operative CT scan or MRI, which could have influenced the surgical procedure.
Preoperative imaging in isolated metopic suture synostosis
Figure 3 Representative MRI (axially-sliced) of a patient with trigonocephaly. MRI shows the soft-tissue alterations, such as triangular brain deformation in the front. No pathological findings could be detected.
However, many authors consider CT scans as the current standard of care being a powerful tool for the quantification of the skull deformity and the accurate planning of surgical treatment. As various studies have evaluated the risks of ionising radiation in children, including the potential of tumour induction and developmental delays, this study was conducted to evaluate the diagnostic accuracy of clinical examination in the diagnosis of single metopic craniosynostosis, without any additional imaging. Many authors have already questioned the general use of radiography in the diagnosis of single-suture craniosynostosis.17,18 Both CT scan and plain radiography result in exposure of patients to X-ray radiation, with inevitable biologic effects, especially in rapid growing children. Even a single CT scan of the head in a 1-year-old raises the
1249 lifetime cancer mortality risk to one in 1500.15 Therefore, exposure to radiation should be reduced to a minimum and, if performed, should have a clinical benefit for the patient. Besides the biological effects of radiation, sedation or anaesthesia, which is routinely used in many centres for infants undergoing CT scans, is accompanied with the additional risk for the patient. The benefit of radiography in the diagnosis of singlesuture synostosis is widely under discussion.19 Especially radiographic diagnosis of a metopic synostosis can be challenging, as the metopic suture can close prematurely without causing trigoncephaly. Vu et al. have demonstrated that fusion of the metopic suture may normally occur as early as 3 months of age, and that complete fusion occurred by 9 months of age in all patients of their series.20 Therefore, 3D CT scans showing complete closure of the metopic suture at an early age (3e9 months) cannot be considered as evidence of metopic synostosis and, thus, should not be the decisive factor for early surgical intervention. In fact, indication for surgical treatment is dependent on the degree of deviation from normal, which is identified by clinical examination. In our study, for all patients with a suspected metopic sutural craniosynostosis, who did not receive any further imaging, the diagnosis was confirmed during the surgical procedure. In addition, in none of our patients with presumed metopic synostosis, plain radiographs or CT scans have indicated a misdiagnosis or have altered the surgical planning. Our results are in line with other authors. In a prospective multicentre study, 67 patients were diagnosed with a single-sutural craniosynostosis based on physical examination.8 Only in one of these patients, subsequential CT scan could not confirm the preliminary diagnosis of craniosynostosis, showing a posterior positional plagiocephaly which was initially misdiagnosed as lamboid synostosis. In all patients with single metopic synostosis (n Z 21, 31%), clinical findings have led to the accurate diagnosis. In addition, three of four craniofacial surgeons agreed that the patient’s treatment would not have been compromised, if a CT scan had not been conducted. However, one surgeon considered CT scans as slightly helpful at surgery. Some authors’ argument is that an additional benefit of CT scans is providing valuable information about the brain parenchyma and ventricular size to accurately plan surgical
Figure 4 Intraoperativ aspects of the fused metopic suture. Coronal approach showing the typical keel-shaped forehead and the closed metopic suture (A). Resected fronto-orbital segment with a complete ossified metopic suture (B).
1250 treatment.8 Underlying brain abnormalities, if present, could have a considerable influence on the treatment in some cases. To detect brain anomalies and avoid potential risks of radiation, an alternative method could be the use of MRI.21 However, in our opinion, MRI seems to be the more suitable imaging technique to evaluate intracranial findings, as MRI is an excellent technique for the diagnosis of associated diseases of the cerebrum, such as, lesions of the parenchyma, midline anomalies, intracranial herniation and hydrocephalus without using ionising radiation.12 As mostly only syndromic and complex craniosynostosis show related intracranial findings, the incidence of underlying brain abnormalities in isolated metopic synostosis in the absence of any clinical symptoms seems not to be different from the general population. Although some reports indicate accompanying intracranial malformations in 15e25% of patients with single metopic synostosis22 in our study, imaging including CT scans (six patients) and MRI (23 patients) have not revealed any intracranial findings, which could have affected additional therapy or a different surgical approach. Although CT scans with 3D reconstruction are an excellent tool for planning surgical correction, we are in line with others, that CT scanning in simple craniosynostosis, such as isolated metopic synostosis, does not provide any additional clinical benefit for surgical planning and should be reserved for patients with complex osseous anomalies.9,11,12 In addition, we believe that MRI should not be used routinely in evaluation of children with isolated sagittal synostosis without any clinical symptoms of intracranial abnormalities. Our preferred diagnostic approach in diagnosis of isolated metopic suture synostosis includes physical examination by an experienced craniofacial surgeon followed by eye examination to rule out the risk of increased intracranial pressure. We use ultrasound and plain skull radiography only in cases with a suspect clinical diagnosis of isolated metopic suture synostosis to ensure that the suture is closed. Although isolated synostoses are not commonly associated with any intracranial malformations, we prefer MRI rather than CT scan if there are any suspects. In patients with complex osseous anomalies or patients with re-operations, we use 3D CT for planning the surgical treatment. Considering potential side effects from ionising radiation, costs and the risks of sedation, surgeons may wish to reserve cranial CT or MRI for those cases in which the physical examination does not provide a clear diagnosis, or in the case of more complex craniofacial anomalies.8e10,23
Conclusion Our study supports the thesis that physical examination by an experienced craniofacial surgeon is a very reliable tool in the diagnosis of isolated metopic synostosis without requiring any additional imaging. Furthermore, no additional benefit from imaging including plain radiographs, CT scans and MRI was found during the surgical procedure, as single isolated synostoses are not commonly associated with any intracranial malformations. To clarify the
M. Engel et al. definitive role of preoperative imaging in isolated metopic craniosynostosis, further studies are warranted, however, considering the biologic effects of ionizing radiation or the possible risks of sedation required for MRI, especially in infants, imaging should be reduced to a minimum.
Conflict of interest The authors declare that they have no conflict of interest or received funding.
References 1. Ruiz-Correa S, Starr JR, Lin HJ, et al. New severity indices for quantifying single-suture metopic craniosynostosis. Neurosurgery 2008;63:318e24. discussion 24e5. 2. Sadove AM, Kalsbeck JE, Eppley BL, Javed T. Modifications in the surgical correction of trigonocephaly. Plast Reconstr Surg 1990;85:853e8. 3. Genitori L, Cavalheiro S, Lena G, Dollo C, Choux M. Skull base in trigonocephaly. Pediatr Neurosurg 1991;17:175e81. 4. Collmann H, So ¨rensen N, Krauss J. Consensus: trigonocephaly. Childs Nerv Syst 1996;12:664e8. 5. Bottero L, Lajeunie E, Arnaud E, Marchac D, Renier D. Functional outcome after surgery for trigonocephaly. Plast Reconstr Surg 1998;102:952e8. discussion 9e60. 6. Shimoji T, Shimabukuro S, Sugama S, Ochiai Y. Mild trigonocephaly with clinical symptoms: analysis of surgical results in 65 patients. Childs Nerv Syst 2002;18:215e24. 7. Aryan HE, Jandial R, Ozgur BM, et al. Surgical correction of metopic synostosis. Childs Nerv Syst 2005;21:392e8. 8. Fearon JA, Singh DJ, Beals SP, Yu JC. The diagnosis and treatment of single-sutural synostoses: are computed tomographic scans necessary? Plast Reconstr Surg 2007;120: 1327e31. 9. Agrawal D, Steinbok P, Cochrane DD. Diagnosis of isolated sagittal synostosis: are radiographic studies necessary? Childs Nerv Syst 2006;22:375e8. 10. Furuya Y, Edwards MS, Alpers CE, Tress BM, Norman D, Ousterhout DK. Computerized tomography of cranial sutures. Part 2: abnormalities of sutures and skull deformity in craniosynostosis. J Neurosurg 1984;61:59e70. 11. Gellad FE, Haney PJ, Sun JC, Robinson WL, Rao KC, Johnston GS. Imaging modalities of craniosynostosis with surgical and pathological correlation. Pediatr Radiol 1985;15: 285e90. 12. Kotrikova B, Krempien R, Freier K, Mu ¨hling J. Diagnostic imaging in the management of craniosynostoses. Eur Radiol 2007;17:1968e78. 13. Anderson VA, Godber T, Smibert E, Weiskop S, Ekert H. Cognitive and academic outcome following cranial irradiation and chemotherapy in children: A longitudinal study. Br J Cancer 2000;82:255e62. 14. Baldwin RT, Preston-Martin S. Epidemiology of brain tumors in childhoodea review. Toxicol Appl Pharmacol 2004;199: 118e31. 15. Brenner D, Elliston C, Hall E, Berdon W. Estimated risks of radiation-induced fatal cancer from pediatric CT. AJR Am J Roentgenol 2001;176:289e96. 16. Gamache GL, Levinson DM, Reeves DL, Bidyuk PI, Brantley KK. Longitudinal neurocognitive assessments of Ukrainians exposed to ionizing radiation after the Chernobyl nuclear accident. Arch Clin Neuropsychol 2005;20:81e93. 17. Hall P, Adami HO, Trichopoulos D, et al. Effect of low doses of ionising radiation in infancy on cognitive function in
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adulthood: Swedish population based cohort study. BMJ 2004; 328:19. 18. Ron E, Modan B, Boice JD, et al. Tumors of the brain and nervous system after radiotherapy in childhood. N Engl J Med 1988;319:1033e9. 19. Cerovac S, Neil-Dwyer JG, Rich P, Jones BM, Hayward RD. Are routine preoperative CT scans necessary in the management of single suture craniosynostosis? Br J Neurosurg 2002;16:348e54. 20. Vu HL, Panchal J, Parker EE, Levine NS, Francel P. The timing of physiologic closure of the metopic suture: A review of 159
patients using reconstructed 3D CT scans of the craniofacial region. J Craniofac Surg 2001;12:527e32. 21. da Silva Freitas R, de Freitas Azzolini T, Shin JH, Persing JA. Associated (parallel) tomographic findings in patients with single-sutural synostosis. J Craniofac Surg 2010;21:411e3. 22. Shillito J, Matson DD. Craniosynostosis: A review of 519 surgical patients. Pediatrics 1968;41:829e53. 23. Lupescu I, Hermier M, Georgescu SA, Froment JC. [Spiral CT evaluation of the craniosynostoses]. J Neuroradiol 2000;27: 128e39.
Value of preoperative imaging in the diagnostics of isolated metopic suture synostosis: A riskebenefit analysis Michael Engel*, Gregor Castrillon-Oberndorfer, Juergen Hoffmann, Christian Freudlsperger Department of Oral and Maxillofacial Surgery, University Hospital Heidelberg, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany Received 7 November 2011; accepted 26 March 2012
KEYWORDS Craniosynostosis; Metopic suture; Trigonocephaly; Computed tomographic; MRI
Summary Radiographic evaluation including plain radiographies and computed tomographic (CT) scans are considered as a necessary tool for diagnosis of craniosynostosis. As recently concerns about harmful effects of ionising radiation in children have been raised, some authors have suggested the use of magnetic resonance imaging (MRI) as a helpful alternative in preoperative imaging of patients with isolated metopic synostosis. Besides confirming the diagnosis of trigonocephaly, MRI is the superior technique for the evaluation of underlying brain anomalies. However, if the benefit of preoperative imaging justifies possible side effects is still discussed controversially. Hence, this study investigated the value of preoperative imaging for the diagnosis of isolated synostosis of the metopic suture compared to a sole clinical examination. In a series of 63 cases with isolated metopic craniosynostosis operated at the Department of Oral and Maxillofacial Surgery, 48 (76.2%) patients received additional radiography or MRI investigation, while in 15 (23.8%) patients the diagnosis was based on clinical examinations only. In all patients, diagnosis was confirmed intra-operatively by a fused metopic suture. CT scans with three-dimensional reconstruction (12.5%) or plain radiographs (39.6%) did not provide any additional benefit for the diagnosis or the surgical treatment. In 23 patients (47.9%), MRI showed the typical soft-tissue alterations like triangular brain deformation in the frontal area. Besides these findings, no brain or other underlying anomalies were diagnosed which had required any additional treatment. The incidence of underlying brain abnormalities in isolated metopic synostosis seemed not to be different from that of the general population.
* Corresponding author. Tel.: þ49 6221 5638811; fax: þ49 6221 564222. E-mail address: [email protected] (M. Engel). 1748-6815/$ - see front matter ª 2012 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.bjps.2012.03.038
Preoperative imaging in isolated metopic suture synostosis
1247
As the characteristic clinical manifestations were sufficient for an accurate diagnosis of isolated metopic synostosis, and with respect to the biological effects of ionising radiation and risks of sedation especially in infants, preoperative imaging should be reduced to a minimum. ª 2012 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.
Single-suture synostosis is the most common form of craniosynostosis, with a prevalence of approximately one in 2500 live births.1 Among the isolated synostoses, fusions of the sagittal, coronal and metopic sutures are the most frequent; however, the exact incidence of isolated metopic synostosis is discussed controversially with an estimated incidence of 0.3e6 per 1000 to 15 000 live births.2e5 Premature closure of the metopic suture results in a triangular head shape, called ‘trigonocephaly’, which features the clinical hallmarks of a keel-shaped forehead, hypotelorism, epicanthus and temporal narrowing with an associated abnormality of the supraorbital rim. Besides that, trigonocephaly can also be presented with only mild clinical manifestations including slight prominence of the metopic ridge.4,6e8 Although these characteristic clinical appearances should point the way to the right diagnosis, plain radiographs of the skull, computed tomographic (CT) scans and three-dimensional (3D) reconstructions of CT scans are still recommended as necessary tools for both the diagnosis of trigonocephaly, and the preoperative planning.8e10 In the majority of patients, standard skull radiography provides all essential preoperative information, including ossification of the metopic suture and the anterior fontanel, hypotelorism and a broadening of occipital region.11 In addition, CT scans and, in particular, 3D CT reconstructions demonstrate detailed information about the cranial bony anatomy, especially the basal sutures and synchondroses. Furthermore, some authors demand CT diagnostic for the detection of associated brain abnormalities.12 However, the diagnostic benefit of radiographic examinations should be carefully weighed out against the biological effects of ionising radiation especially in infants.8,9,13e17 To avoid radiographic examination in childhood, MRI diagnostic can be a helpful tool in preoperative imaging of patients with isolated sagittal synostosis. Besides confirming the diagnosis of trigonocephaly, MRI is the superior technique for the evaluation of underlying brain anomalies. Hence, the value of preoperative imaging as a diagnostic tool in isolated metopic synostosis is still under discussion. The aim of this study was to evaluate if clinical examination without additional imaging is sufficient for the diagnosis of single metopic synostosis and if the diagnostic surplus justifies possible side effects of ionising radiation or sedation in infants.
Material and methods For this retrospective non-blinded case review study, the study population consisted of all patients with an isolated metopic craniosynostosis who underwent surgery between January 1998 and December 2010 in the Department of Oral
and Maxillofacial Surgery at the University Hospital Heidelberg. All review procedures were in strict accordance with general guidelines and an approved application on file at our institutional review board. Patients were selected on the basis of their final, not the initial, diagnosis. Only children with primary non-syndromic metopic craniosynostosis were considered eligible for this study. Children with syndromal or secondary metopic craniosynostosis were excluded. Medical records of all patients were reviewed in their entirety. The following information was retrospectively collected and reviewed from the database: patient’s demographic details, the diagnosis following clinical examination by experienced craniofacial surgeons, results of the radiologic evaluation if conducted, details of the operative procedure as noted by the surgeon and alteration of the diagnosis following the radiologic examination or the operative procedure. All patients received their clinical examinations exclusively by one of our three craniofacial surgeons, who ranged in experience from 4 to 15 years. Radiological examinations were evaluated by both one craniofacial surgeon and one experienced neuroradiologist from the Department of Neuroradiology at the University Hospital Heidelberg. Furthermore, patients who received CT scan or MRI were investigated for intracranial abnormalities.
Results From January 1998 to December 2010, a total of 85 children were identified from the medical records with the diagnosis of an isolated metopic synostosis. Twenty-two patients were treated conservatively, because clinical characteristics were less pronounced or surgery was declined by the parents. Hence, a total of 63 patients included 48 (76.2%) boys and 15 (23.8%) girls, underwent a surgical procedure for isolated non-syndromatic metopic craniosynostosis at our Department of Oral and Maxillofacial Surgery. The median age at referral was 5 months (range 1e12 months). At the first physical examination, all patients showed characteristic manifestations of trigonocephaly including significant deformity of the supraorbital ridges and temporal regions, with hypotelorism (Figure 1). Surgery was performed at a median age of 11.2 months (5e14 months). All these children underwent craniofacial reconstruction, according to the standardised fronto-orbital advancement especially applied to trigonocephaly. In all cases, the suspected synostosis of the metopic suture was confirmed by the surgeons. Preoperative imaging has been performed in 48 (76.2%) children (Figure 2). Standard skull radiographs were obtained in 19 (39.6%) patients; in a majority of these cases radiography had been performed by the referring physician. The diagnostic accuracy of plain radiograph studies was 100%. Six children (12.5%) had a CT scan of the head in the preoperative period; all had been performed by
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M. Engel et al.
Figure 1 Six month old boy with typical aspect of trigonocephaly (pre-operatively). Clinical hallmarks of metopic synostosis including the keel-shaped forehead, hypotelorism and epicanthus frontal (A), profile (B). Corresponding three-dimensional reconstructions of computed tomographic scans showing complete fusion of the metopic suture (C).
the referring physician prior to craniofacial consultation. CT was confirmatory of the diagnosis in all six patients. In none of the patients who received CT scans, intracranial abnormalities were found, which could have influenced surgical planning. In 23 patients (47.9%), MRI was conducted. The accuracy in defining bony abnormalities of MRI was inferior compared to CT, but was sufficient to confirm the diagnosis of trigonocephaly, as all patients in our study showed the typical soft-tissue alterations like the triangular brain deformation in the frontal area. Besides that, no malformations of the cerebrum, such as, midline anomalies, lesions of the parenchyma, intracranial herniation, hydrocephalus or
changes in intracranial morphology were found in our series (Figure 3). In addition, no alterations were made to the clinical decisions regarding the timing of surgery. Fifteen (23.8%) children with the typical clinical hallmarks of trigonocephaly had no preoperative imaging. In all of these cases, the diagnosis of metopic synostosis was confirmed intra-operatively (Figure 4).
Discussion The characteristic clinical features of single-sutural craniosynostosis permit a confidential clinical diagnosis.
Figure 2 Structure of study population. In 15 patients, diagnosis of metopic synostosis was made by clinical examination with a 100% accuracy as proofed by intraoperative findings. In 48 patients diagnosis was confirmed by Standard skull radiographs or computed tomographic (CT) scans. No intracranial abnormalities have been detected in 29 patients who received a pre-operative CT scan or MRI, which could have influenced the surgical procedure.
Preoperative imaging in isolated metopic suture synostosis
Figure 3 Representative MRI (axially-sliced) of a patient with trigonocephaly. MRI shows the soft-tissue alterations, such as triangular brain deformation in the front. No pathological findings could be detected.
However, many authors consider CT scans as the current standard of care being a powerful tool for the quantification of the skull deformity and the accurate planning of surgical treatment. As various studies have evaluated the risks of ionising radiation in children, including the potential of tumour induction and developmental delays, this study was conducted to evaluate the diagnostic accuracy of clinical examination in the diagnosis of single metopic craniosynostosis, without any additional imaging. Many authors have already questioned the general use of radiography in the diagnosis of single-suture craniosynostosis.17,18 Both CT scan and plain radiography result in exposure of patients to X-ray radiation, with inevitable biologic effects, especially in rapid growing children. Even a single CT scan of the head in a 1-year-old raises the
1249 lifetime cancer mortality risk to one in 1500.15 Therefore, exposure to radiation should be reduced to a minimum and, if performed, should have a clinical benefit for the patient. Besides the biological effects of radiation, sedation or anaesthesia, which is routinely used in many centres for infants undergoing CT scans, is accompanied with the additional risk for the patient. The benefit of radiography in the diagnosis of singlesuture synostosis is widely under discussion.19 Especially radiographic diagnosis of a metopic synostosis can be challenging, as the metopic suture can close prematurely without causing trigoncephaly. Vu et al. have demonstrated that fusion of the metopic suture may normally occur as early as 3 months of age, and that complete fusion occurred by 9 months of age in all patients of their series.20 Therefore, 3D CT scans showing complete closure of the metopic suture at an early age (3e9 months) cannot be considered as evidence of metopic synostosis and, thus, should not be the decisive factor for early surgical intervention. In fact, indication for surgical treatment is dependent on the degree of deviation from normal, which is identified by clinical examination. In our study, for all patients with a suspected metopic sutural craniosynostosis, who did not receive any further imaging, the diagnosis was confirmed during the surgical procedure. In addition, in none of our patients with presumed metopic synostosis, plain radiographs or CT scans have indicated a misdiagnosis or have altered the surgical planning. Our results are in line with other authors. In a prospective multicentre study, 67 patients were diagnosed with a single-sutural craniosynostosis based on physical examination.8 Only in one of these patients, subsequential CT scan could not confirm the preliminary diagnosis of craniosynostosis, showing a posterior positional plagiocephaly which was initially misdiagnosed as lamboid synostosis. In all patients with single metopic synostosis (n Z 21, 31%), clinical findings have led to the accurate diagnosis. In addition, three of four craniofacial surgeons agreed that the patient’s treatment would not have been compromised, if a CT scan had not been conducted. However, one surgeon considered CT scans as slightly helpful at surgery. Some authors’ argument is that an additional benefit of CT scans is providing valuable information about the brain parenchyma and ventricular size to accurately plan surgical
Figure 4 Intraoperativ aspects of the fused metopic suture. Coronal approach showing the typical keel-shaped forehead and the closed metopic suture (A). Resected fronto-orbital segment with a complete ossified metopic suture (B).
1250 treatment.8 Underlying brain abnormalities, if present, could have a considerable influence on the treatment in some cases. To detect brain anomalies and avoid potential risks of radiation, an alternative method could be the use of MRI.21 However, in our opinion, MRI seems to be the more suitable imaging technique to evaluate intracranial findings, as MRI is an excellent technique for the diagnosis of associated diseases of the cerebrum, such as, lesions of the parenchyma, midline anomalies, intracranial herniation and hydrocephalus without using ionising radiation.12 As mostly only syndromic and complex craniosynostosis show related intracranial findings, the incidence of underlying brain abnormalities in isolated metopic synostosis in the absence of any clinical symptoms seems not to be different from the general population. Although some reports indicate accompanying intracranial malformations in 15e25% of patients with single metopic synostosis22 in our study, imaging including CT scans (six patients) and MRI (23 patients) have not revealed any intracranial findings, which could have affected additional therapy or a different surgical approach. Although CT scans with 3D reconstruction are an excellent tool for planning surgical correction, we are in line with others, that CT scanning in simple craniosynostosis, such as isolated metopic synostosis, does not provide any additional clinical benefit for surgical planning and should be reserved for patients with complex osseous anomalies.9,11,12 In addition, we believe that MRI should not be used routinely in evaluation of children with isolated sagittal synostosis without any clinical symptoms of intracranial abnormalities. Our preferred diagnostic approach in diagnosis of isolated metopic suture synostosis includes physical examination by an experienced craniofacial surgeon followed by eye examination to rule out the risk of increased intracranial pressure. We use ultrasound and plain skull radiography only in cases with a suspect clinical diagnosis of isolated metopic suture synostosis to ensure that the suture is closed. Although isolated synostoses are not commonly associated with any intracranial malformations, we prefer MRI rather than CT scan if there are any suspects. In patients with complex osseous anomalies or patients with re-operations, we use 3D CT for planning the surgical treatment. Considering potential side effects from ionising radiation, costs and the risks of sedation, surgeons may wish to reserve cranial CT or MRI for those cases in which the physical examination does not provide a clear diagnosis, or in the case of more complex craniofacial anomalies.8e10,23
Conclusion Our study supports the thesis that physical examination by an experienced craniofacial surgeon is a very reliable tool in the diagnosis of isolated metopic synostosis without requiring any additional imaging. Furthermore, no additional benefit from imaging including plain radiographs, CT scans and MRI was found during the surgical procedure, as single isolated synostoses are not commonly associated with any intracranial malformations. To clarify the
M. Engel et al. definitive role of preoperative imaging in isolated metopic craniosynostosis, further studies are warranted, however, considering the biologic effects of ionizing radiation or the possible risks of sedation required for MRI, especially in infants, imaging should be reduced to a minimum.
Conflict of interest The authors declare that they have no conflict of interest or received funding.
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