The Noggin Doctor: Afterthoughts from my ASMS Visiting Professor Lecture at the University of Chicago

I was nominated by the American Society of Maxillofacial Surgeons to be one of three visiting professors this year. It is a great honor and one that I gladly accepted. My first stop was to the Division of Plastic Surgery at the University of Chicago. It was a wonderful opportunity to speak on craniosynostosis, a topic about which I have authored no less than 80 peer-reviewed publications in my career. I was inspired by the enthusiasm of the residents and the insightful questions they and the faculty offered in response to the lecture. The lecture was called Craniosynostosis: Past, Present, and Future and it started with the history, worked into present day diagnosis and management, and broached some of the cutting edge diagnostic and treatment methods that are now being developed in places like our own craniofacial imaging center at the Sheik Zayed Institute for Pediatric Surgical Innovation at Children’s National Hospital. I also discussed some of the controversial topics in craniofacial surgery including the over-diagnosis of metopic craniosynostosis. This is a topic about which I and others have lamented, largely in response to various craniofacial centers reporting a mysterious rise in this diagnosis since the mid-1990’s.

Kweldam CF, et al. The incidence of craniosynostosis in the Netherlands, 1997-2007. J Plast Reconstr Aesthet Surg.2011 May;64(5):583-8.

Lee HQ, et al. Changing epidemiology of nonsyndromic craniosynostosis and revisiting the risk factors. J Craniofac Surg. 2012 Sep;23(5):1245-51.

van der Meulen J, et al The increase of metopic synostosis: a pan-European observation. J Craniofac Surg. 2009 Mar;20(2):283-6.

Selber J, et al. The changing epidemiologic spectrum of single-suture synostoses. Plast Reconstr Surg. 2008 Aug;122(2):527-33.

To summarize these reports, selective centers in the US and Europe have observed a rise in the incidence of metopic craniosynstosis over the last two decades and the etiology of this increase is unclear. The problem is, this phenomenon has not been reported everywhere and many centers, including ours, have seen no increase in metopic over the last two decades. How is this possible? Is there something in the water in Philadelphia, Michigan, or in parts of Europe? Is there some difference in the genetic pool in these locations compared to the rest of the planet such that they are fusing their sutures too early? No, I think a more rational explanation lies in how these centers define metopic craniosynostosis. Remember, this is the ONLY CRANIAL SUTURE TO FUSE NORMALLY IN INFANCY. Thus, the presence of a fused suture cannot be relied upon to make the diagnosis, Instead, the shape of the head, specifically the forehead, is what determines whether the child’s appearance warrants a diagnosis of metopic craniosynostosis. Unfortunately, most clinicians rely on their subjective impression to make the diagnosis and once the diagnostic threshold is crossed, most centers reflexively recommend surgery. Think about this- someone, usually a pediatrician, thinks your child’s head shape looks suspicious and sends you to a surgeon, who is supposed to be an “expert”. He looks at the shape of your child’s head and, without any real measurement or metric on which he can rely, decrees that your child’s head shape is either normal or abnormal. It is analogous to asking someone if you look overweight- in extreme situations the answer is clear, but for most cases it is a judgement call based on the impressions of the observer. If the surgeon thinks, based on his subjective impression, that the forehead shape is too narrow, he will usually make a strong suggestion that your child undergo surgery to prevent problems with his or her brain, neurocognitive development, and their social interactions later in life. This must sound familiar to those parents who have undergone such an evaluation. And the procedure they are suggesting is usually not a small one- it involves making a large open scalp incision, removing most of the cranium and remodeling it on the back table, and then replacing it in a new position. Sound scary? Well, I do these procedures on average about once per week and although we have a great team and excellent outcomes, it is a big operation for an infant and their family to endure without a more grounded explanation than ‘Your child’s head looks too narrow to me”. What is even more confusing is that the external appearance of the forehead does not always correlate well with the curvature or contour of the cranium on the endocortical surface (i.e,., the “brain side”) of a CT scan. To add even more ambiguity to the equation, there are conflicting reports about whether the forehead or general head shape in this condition is correlated with global or local (frontal) intracranial pressure elevations. Moreover, there is no data to support the idea that the surgery actually improves cognitive or developmental outcomes in metopic craniosynostosis. What does this all mean? Given this degree of ambiguity, it is my opinion that before any parent signs their infant child up for this type of surgery they should demand a more objective assessment of frontal shape than what the surgeon “thinks”. There are, in fact, objective metrics that provide an accurate assessment of forehead shape based on CT imaging:

Plast Reconstr Surg. 2016 May;137(5):1548-55. Objective Assessment of the Interfrontal Angle for Severity Grading and Operative Decision-Making in Metopic Synostosis. Anolik RA(1), Allori AC, Pourtaheri N, Rogers GF, Marcus JR. Author information: (1)Durham, N.C.; Cleveland, Ohio; and Washington, D.C. From the Division of Plastic, Maxillofacial and Oral Surgery, Duke University Hospital; Duke Cleft and Craniofacial Center; Duke Children's Hospital and Health Center; the Department of Plastic Surgery; University Hospitals Case Medical Center; and the Division of Plastic and Reconstructive Surgery, Children's National Medical Center. BACKGROUND: The purpose of this study was to evaluate the utility of a previously validated interfrontal angle for classification of severity of metopic synostosis and as an aid to operative decision-making. METHODS: An expert panel was asked to study 30 cases ranging from minor to severe metopic synostosis. Based on computed tomographic images of the skull and clinical photographs, they classified the severity of trigonocephaly (1 = normal, 2 = mild, 3 = moderate, and 4 = severe) and management (0 = nonoperative and 1 = operative). The severity scores and management reported by experts were then pooled and matched with the interfrontal angle computed from each respective computed tomographic scan. A threshold was identified at which most experts agree on operative management. RESULTS: Expert severity scores were higher for more acute interfrontal angles. There was a high concordance at the extremes of classifications, severe (4) and normal (1) (p < 0.0001); however, between interfrontal angles of 114.3 and 136.1 degrees, there exists a "gray zone," with severe discordance in expert rankings. An operative threshold of 118.2 degrees was identified, with the interfrontal angle able to predict the expert panel's decision to proceed with surgery 87.6 percent of the time. CONCLUSIONS: The interfrontal angle has been previously validated as a simple, accurate, and reproducible means for diagnosing trigonocephaly, but must be obtained from computed tomographic data. In this article, the authors demonstrate that the interfrontal angle can be used to further characterize the severity of trigonocephaly. It also correlated with expert decision-making for operative versus nonoperative management. This tool may be used as an adjunct to clinical decision-making when the decision to proceed with surgery may not be straightforward.

Plast Reconstr Surg. 2016 Jan;137(1):205-13. What's in a Name? Accurately Diagnosing Metopic Craniosynostosis Using a Computational Approach. Wood BC(1), Mendoza CS, Oh AK, Myers E, Safdar N, Linguraru MG, Rogers GF. Author information: (1)Washington, D.C. From the Division of Plastic and Reconstructive Surgery, Children's National Health System; the Division of Plastic Surgery, George Washington University School of Medicine and Health Sciences; Sheikh Zayed Institute for Pediatric Surgical Innovation, Children's National Health System; and the Departments of Radiology and Pediatrics, School of Medicine and Health Sciences, George Washington University. BACKGROUND: The metopic suture is unlike other cranial sutures in that it normally closes in infancy. Consequently, the diagnosis of metopic synostosis depends primarily on a subjective assessment of cranial shape. The purpose of this study was to create a simple, reproducible radiographic method to quantify forehead shape and distinguish trigonocephaly from normal cranial shape variation. METHODS: Computed tomography scans were acquired for 92 control patients (mean age, 4.2 ± 3.3 months) and 18 patients (mean age, 6.2 ± 3.3 months) with a diagnosis of metopic synostosis. A statistical model of the normal cranial shape was constructed, and deformation fields were calculated for patients with metopic synostosis. Optimal and divergence (simplified) interfrontal angles (IFA) were defined based on the three points of maximum average deformation on the frontal bones and metopic suture, respectively. Statistical analysis was performed to assess the accuracy and reliability of the diagnostic procedure. RESULTS: The optimal interfrontal angle was found to be significantly different between the synostosis (116.5 ± 5.8 degrees; minimum, 106.8 degrees; maximum, 126.6 degrees) and control (136.7 ± 6.2 degrees; minimum, 123.8 degrees; maximum, 169.3 degrees) groups (p < 0.001). Divergence interfrontal angles were also significantly different between groups. Accuracy, in terms of available clinical diagnosis, for the optimal and divergent angles, was 0.981 and 0.954, respectively. CONCLUSIONS: Cranial shape analysis provides an objective and extremely accurate measure by which to diagnose abnormal interfrontal narrowing, the hallmark of metopic synostosis. The simple planar angle measurement proposed is reproducible and accurate, and can eliminate diagnostic subjectivity in this disorder.

Automated interfrontal divergence angle. is the most accurate measure of forehead shape and contour reported.

The manual interferential divergence angle can be performed on a standard CT image and accurately determines if the forehead shape is overly acute (trigonocephalic) or not.

While no measurement is perfect, these measurement are easy to perform and certainly beat letting the surgeon decide based on an “eyeball” assessment of your child’s head shape. Such subjectively makes it all to easy to simply slap a table of “metopic craniosynostosis” on a child and subsequently conclude that the child “needs surgery to prevent brain damage or blindness”. Over the years I have recommended against surgery for many patients with very mild forehead narrowing that does not meet any objective diagnostic criteria for trigonocephaly (the phenotype of metopic synostosis) but who were told by an “expert” that they “needed” surgery. They did not. In most instances, the surgeon was either misinformed, unethical, or both. Some clinicians are so misinformed that they have recommended surgery on a patient with a fused metopic suture (a normal finding in infants after 8-9 months) but an otherwise normal forehead shape. This type of diagnostic ambiguity has undoubtedly resulted in many children undergoing unnecessary surgery. Nearly 25 years ago a similar diagnostic debacle let to over-diagnosis of a different type of craniosynostosis- lambdoid. Shortly after the AAP Back to Sleep Campaign in 1993, certain craniofacial centers began reporting a massive rise in the incidence of lambdoid synostosis (the sutures in the back of the cranium). This is the most rare forms of craniosynostosis and other centers were not seeing this rise. Sound familiar? After an investigation by the CDC, it was determined that the posterior flattening some centers were diagnosing and treating as lambdoid fusion was actually merely deformational plagiocephaly! This led to major interventions and the practice stopped. What is shocking is that the CDC has failed to do the same type of investigation with metopic. One difference is that the lambdoid suture fuses late in life and in the cases that were questioned, the suture was clearly open by CT exam. Thus, the presence or absence of a suture fusion is the only diagnostic criteria that needs to be considered. If it was open, it is NOT lambdoid craniosynosotis. The diagnostic decision is binary and not really open to subjectivity. Contrast this with the metopic suture, which closes normally in infancy and will be fused or fusion in ALL children before a year of age. The fusion cannot be the fulcrum of a diagnosis of “metopic cranisynostosis” and the diagnosis rests on the phenotype or appearance of the patient in the eyes of the surgeon. There are several studies in the literature that have surveyed craniofacial surgeons and found that while authorities were consistent in the extreme cases (normal or very narrow forehead) they were extremely inconsistent for intermediate cases.

Plast Reconstr Surg. 2016 May;137(5):1548-55. Objective Assessmentof the Interfrontal Angle for Severity Grading and Operative Decision-Making in Metopic Synostosis. Anolik RA(1), Allori AC, Pourtaheri N, Rogers GF, Marcus JR. Author information: (1)Durham, N.C.; Cleveland, Ohio; and Washington, D.C. From the Division of Plastic, Maxillofacial and Oral Surgery, Duke University Hospital; Duke Cleft and Craniofacial Center; Duke Children's Hospital and Health Center; the Department of Plastic Surgery; University Hospitals Case Medical Center; and the Division of Plastic and Reconstructive Surgery, Children's National Medical Center. BACKGROUND: The purpose of this study was to evaluate the utility of a previously validated interfrontal angle for classification of severity of metopic synostosis and as an aid to operative decision-making. METHODS: An expert panel was asked to study 30 cases ranging from minor to severe metopic synostosis. Based on computed tomographic images of the skull and clinical photographs, they classified the severity of trigonocephaly (1 = normal, 2 = mild, 3 = moderate, and 4 = severe) and management (0 = nonoperative and 1 = operative). The severity scores and management reported by experts were then pooled and matched with the interfrontal angle computed from each respective computed tomographic scan. A threshold was identified at which most experts agree on operative management. RESULTS: Expert severity scores were higher for more acute interfrontal angles. There was a high concordance at the extremes of classifications, severe (4) and normal (1) (p < 0.0001); however, between interfrontal angles of 114.3 and 136.1 degrees, there exists a "gray zone," with severe discordance in expert rankings. An operative threshold of 118.2 degrees was identified, with the interfrontal angle able to predict the expert panel's decision to proceed with surgery 87.6 percent of the time. CONCLUSIONS: The interfrontal angle has been previously validated as a simple, accurate, and reproducible means for diagnosing trigonocephaly, but must be obtained from computed tomographic data. In this article, the authors demonstrate that the interfrontal angle can be used to further characterize the severity of trigonocephaly. It also correlated with expert decision-making for operative versus nonoperative management. This tool may be used as an adjunct to clinical decision-making when the decision to proceed with surgery may not be straightforward.

Plast Reconstr Surg Glob Open. 2019 Mar 14;7(3):e1944. Practical Computed Tomography Scan Findings for Distinguishing Metopic Craniosynostosis from Metopic Ridging.Birgfeld CB(1), Heike CL(2), Al-Mufarrej F(3), Oppenheimer A(4), Kamps SE(5),Adidharma W(6), Siebold B(7).Author information: (1)Department of Surgery, Division of Plastic Surgery, University of Washington, Seattle Children's Hospital, Seattle, Wash. (2)Department of Pediatrics, Division of Craniofacial Medicine, Seattle Children's Hospital, Seattle, Wash. (3)Department of Surgery, Division of Plastic Surgery, Wayne State University, Detroit, Mich. (4)Oppenhemier Plastic Surgery, Orlando, Fla. (5)Department of Radiology, Seattle Children's Hospital, Seattle, Wash. (6)University of Washington, Seattle, Wash. (7)Seattle Children's Hospital, Seattle Wash. Background: Premature fusion of the metopic suture (ie, metopic craniosynostosis) can be difficult to discriminate from physiological closure of the metopic suture with ridging (MR). Yet, MCS is treated surgically, whereas MR is treated nonsurgically. Often, the diagnosis can be made by physical examination alone, but in difficult cases, a computed tomography (CT) scan can add additional diagnostic information. Methods: We de-identified, randomized, and analyzed the CT scans of patients with MCS (n = 52), MR (n = 20) and age-matched normative controls (n = 52) to identify specific findings helpful in distinguishing between MCS and MR. Four expert clinicians were blinded to the clinical diagnosis and assessed each CT for features of the orbits, frontal bones, and inner table of calvaria. Results: Although no single feature was diagnostic of MCS, we identified several signs that were correlated with MCS, MR, or controls. Features such as "posteriorly displaced frontal bone" and "frontal bone tangent to mid-orbit or medial" demonstrated higher correlation with MCS than MR and the addition of other features improves the accuracy of diagnosis as did inclusion of the interfrontal divergence angle. Conclusion: The presence of a closed metopic suture in addition to other CT scan findings may improve the accuracy of diagnosing MCS, MR, and normocephaly.

Given the diagnostic inconsistency, I am quite certain that the “rise” in metopic craniosynostosis observed by some authors is a not real, but is instead the result of vague diagnostic criteria about what constitutes trigonocephaly (the appearance of premature metopic fusion, with a narrow forehead, a midline ridge, possible closely-set eyes, and wider posterior cranium) combined with the effects of posterior deformational flattening following the 1993 Back to Sleep Campaign. As we have noted previously, that program led to major increase in posterior deformational flattening that can widen the back of the head and, in a child with a slightly or mildly narrow forehead shape, will make the forehead appear even more narrow and the head more triangular in overall shape. It is important to understand that the presence or absence of posterior flattening does not alter the forehead contour and, consequently, the risk of frontal lobe restriction. While such changes may make the head look more abnormal, there is no evidence that there are consequent developmental effects from the addition of deformational posterior flattening. In my opinion, the only way to accurately assess forehead contour and angularity, and to give a child the diagnosis of “metopic craniosynosotsis”, is by using a validated, objective CT or 3D photogrammetry metric and comparing the shape to a normative database of healthy kids. Demand this from your surgeon. It is the only way to know if shape is really abnormal or just a variation of normal, or whether you have encountered the all-too-common over-zealous surgeon.