AM Kemp

C Chasler

CJ Hobbs

CJ Meservy

Deborah Stewart

EA Franken Jr

JR Sty

K Nakahara

Leonard Swischuk

Matthew Walvick

P Weir

PK Kleinman

S Fernando

Thomas Sanchez

WE Allen 3rd

English

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Skull fracture vs. accessory sutures: how can we tell the difference?

Sanchez, Thomas

Stewart, Deborah

Walvick, Matthew

Swischuk, Leonard

eScholarship - University of California

UC DavisUC Davis Previously Published WorksTitleSkull fracture vs. accessory sutures: how can we tell the difference?Permalinkhttps://escholarship.org/uc/item/7x06b0vhJournalEmergency Radiology: A Journal of Practical Imaging Official Journal of the American Society of Emergency Radiology, 17(5)ISSN1438-1435AuthorsSanchez, ThomasStewart, DeborahWalvick, Matthewet al.Publication Date2010-09-01DOI10.1007/s10140-010-0877-8 Peer reviewedeScholarship.org Powered by the California Digital LibraryUniversity of CaliforniaPICTORIAL ESSAYSkull fracture vs. accessory sutures: how can we tellthe difference?Thomas Sanchez & Deborah Stewart &Matthew Walvick & Leonard SwischukReceived: 23 March 2010 /Accepted: 12 May 2010 /Published online: 23 May 2010# The Author(s) 2010. This article is published with open access at Springerlink.comKeywords Skull fractures . Accessory sutures . CT scanIntroductionPlain film radiography remains the most cost effectivemethod in evaluating skull fractures and can easilydifferentiate major sutures and common vascular groovesfrom fractures. However, in children this can be compli-cated due to the presence of numerous synchondroses andunusual accessory sutures. Plain film evaluation isespecially challenging not only because of variousartifacts that can degrade the study but also the inabilityto visualize intracranial processes, such as contusions andhemorrhage, that can substantiate a calvarial finding.Minimal soft tissue swelling can be difficult to see evenwith oblique views. Superimposition of normal suturelines like the metopic suture can mimic a fracture if one isnot careful to obtain additional views [1]. During the pastdecade, the increasing use of spiral and multidetector CThave lead to the ability of workstations to generate three-dimensional (3D) reconstructions of the skull. Therefore ifcranial CT is deemed clinically necessary in traumapatients, questionable fractures can be confidently differen-tiated from unusual accessory sutures using these additionalworkstation capabilities.Normal ossification centersThe parietal and occipital bones in particular are commonregions for accessory sutures because of their multipleossification centers. The parietal bone ossifies from twocenters while the occipital bone ossifies from six centers [2,3]. An accessory intraparietal or subsagittal suture is rare butcan be seen dividing the parietal bone (Fig. 1). They can beexplained on the basis of incomplete union of the twoseparate ossification centers [4]. These are usually bilateraland fairly symmetrical but can at times be unilateral. Theoccipital bone has a more complex development. Theforamen magnum is surrounded by four ossification centers.On each side are the exoccipitals, ventrally located is thebasoccipital and dorsally, the supraoccipital center containsthe midline occipital fissure which can sometimes persistantenatally (Fig. 2). This pattern of development cantherefore give rise to numerous accessory sutures that couldbe mistaken for fractures especially with plain film evalua-tion alone. CT scan with 3D reconstruction is vital in thefurther characterization of a questionable fracture.From the Departments of Radiology and Pediatrics, University ofCalifornia Davis, Sacramento CA and University of Texas MedicalBranch, Galveston TXT. Sanchez (*)University of California Davis,Sacramento, CA, USAe-mail: thomas.sanchez@ucdmc.ucdavis.eduD. StewartCAARE Diagnostic and Treatment Center,Department of Pediatrics, University of California Davis,Sacramento, CA, USAM. WalvickDepartment of Internal Medicine,University of California San Francisco,Fresno, CA, USAL. SwischukDepartment of Radiology, University of Texas Medical Branch,Galveston, TX, USAEmerg Radiol (2010) 17:413–418DOI 10.1007/s10140-010-0877-8Radiographic differentiation of skull fractureand accessory sutureSimple non-depressed skull fractures are sharp lucencieswith non-sclerotic edges. In contrast, accessory suturesusually will show a zigzag pattern with interdigitations andsclerotic borders similar to major calvarial sutures (Fig. 3).When fractures extend into a major suture, there could bewidening of the fracture line as it approaches the suture orthere is associated diastasis of the adjacent synchodrosis orsuture. (Fig. 4). An accessory suture will usually notproduce this appearance. High impact fractures can crosssuture lines or extend from one major suture to another,whereas accessory sutures join and merge with the majorsuture (Fig. 5). In terms of bilaterality, accessory sutures areoften present on both sides and are fairly symmetricespecially in the parietal bones [2]. Occipital accessorysutures can be complex and multiple but are also frequentlybilateral [5]. However, skull fractures can be also bilateral.When they are, these fractures are almost always associatedwith high impact injuries and thus will often showcomminution, depression, and marked asymmetry. Hence,these complex and high impact fractures are almost neverconfused with developmental variants [6, 7]. Finally, softtissue swelling or hematoma is frequently associated withacute skull fractures. One study has shown that at least4 mm of soft tissue swelling was present on the cranial CTscan in all cases of acute skull fractures that they reviewed[8]. However, absence of subgaleal hematoma or swellingdoes not entirely rule out a fracture especially if the injuryis remote or imaging was performed several days after thetrauma [9]. Its presence though is highly suggestive of anacute traumatic event. (Fig. 6).Knowledge of the normal anatomy, development andtiming of sutural closure are also important in theevaluation of questionable fractures. The occipital andinnominate sutures are no longer apparent by age 4 whileFig. 1 Accessory intraparietal or subsagittal suture (arrow)a bFig. 2 Three-dimensional re-construction of the occipitalbone outlining the six ossifica-tion centers including the rem-nant of the midline occipitalfissure (arrow). Two interparie-tal ossification centers (yellow),single supraoccipital center(red), two exoccipitals (violet),and single basoccipital (green).FM foramen magnum414 Emerg Radiol (2010) 17:413–418the mendosal suture completely fuses by 6 years of age[10]. An example of an accessory suture that can bemisleading is the normal persistent occipital suture. Itextends from the dorsal aspect of the foramen magnumand can appear wide and sharp. However, it shouldextend no more than 2 cm from the edge of theforamen magnum. A longer fissure would be inconsis-tent with its normal embryogenesis and thereforerepresents a fracture [3] (Fig. 7). In some cases wherea lucency is shorter than 2 cm, the age of the patientwould help in deciding if this is a fracture or just asutural remnant. As noted previously, this suture closesby 4 years and a persistent lucency beyond this age isindicative of a fracture.In some cases, definite differentiation between a fractureand accessory suture can still be elusive. This is illustratedby a recent case where a 2-year-old boy came in withmild frontal soft tissue swelling after a fall. Plaina bFig. 3 a This sharp lucency (arrow) with adjacent mild soft tissueswelling represents a fracture. b In contrast, this occipital accessorysuture (arrow) has a sclerotic border with irregular interdigitationssimilar to the adjacent lambdoid sutures (smaller arrows). Note theabsence of soft tissue swellinga bFig. 4 a Notice how the frac-ture line is narrow proximallybut progressively widens as itextends into the sagittal suture.b In a different patient, the leftoccipital bone fracture (arrow)extends into and slightly widensthe posterior intraoccipital syn-chondrosis (small arrow)Fig. 5 High impact injury with a non-depressed fracture lineextending from both lambdoid sutures and crossing over into the leftparietal bone. Accessory sutures will not produce this appearanceEmerg Radiol (2010) 17:413–418 415radiograph showed a sharp lucency in the left occipitalbone that was thought to represent a fracture. CT scanwith 3D reconstruction was performed and showed awell-defined lucency extending into the lambdoid suture.There is no associated diastasis or widening and it doesnot extend into the foramen magnum posteriorly. Softtissue swelling or hematoma was also absent. A bonescan was performed which showed no evidence ofradiotracer uptake. It was therefore felt that this is moreconsistent with an accessory suture. Follow-up studyafter 3 months however showed sclerosis of this lucencyindicating that this was indeed a fracture. (Fig. 8).Clinical experience has consistently demonstrated thatbone scan is much less sensitive in detecting skullfractures. In one study, less than 40% of skull scintigramswere positive in patients with clearly visualized fracturesin skull radiographs [11, 12]. The above case alsodemonstrates that in difficult cases, a follow-up studymight be the only way to differentiate a fracture from anaccessory suture. A fracture usually will show evidence ofhealing or sclerosis in two or three months.ConclusionIn summary, fractures and accessory sutures can bedifferentiated in most cases by observing its characteristicsa bFig. 6 a Sharp lucency repre-senting a fracture in the rightparietal region is accompaniedby a large subgaleal hematoma(arrow). b In a different patient,the right temporal bone fractureis associated with a more subtle3 mm soft tissue swelling(arrow)Fig. 7 This midline occipitalfracture extending into the fora-men magnum is easily differen-tiated from a normal persistentmidline occipital fissure becauseof its length, extending 3 cmfrom the dorsal lip of the fora-men magnum416 Emerg Radiol (2010) 17:413–418such as bilaterality, symmetry, associated diastasis, andpresence of soft tissue swelling (Table 1). Knowledge of thenormal anatomy, development, and timing of suturalclosure are also necessary to decipher the varied andsometimes complex nature of these accessory suturesespecially in the occipital region. However, in difficultcases, it is prudent to request for a follow-up study to lookfor signs of healing.ac dbFig. 8 Occipital fracture thatwas mistaken for an accesorysuture. a Plain radiographshowed a left occipital lucency.b Nuclear medicine study didnot show any abnormal uptakeof radiotracer. c Together withthe CT scan characteristics, itwas felt that this lucency is morecompatible with an accesorysuture. d Follow-up CT scanafter 3 months however showedsclerosis of this lucency indicat-ing healing of the fractureTable 1 Differentiation between skull fracture and accessory sutureSkull fracture Accessory sutureSharp lucency with non-sclerotic edges Zigzag pattern with sclerotic bordersWidens as is approaches a suture No associated diastasisCan cross adjacent suture lines Merges with the adjacent sutureOften unilateral and asymmetric if bilateral Often bilateral and fairly symmetricAssociated with some soft tissue swelling No soft tissue swellingEmerg Radiol (2010) 17:413–418 417Open Access This article is distributed under the terms of theCreative Commons Attribution Noncommercial License which per-mits any noncommercial use, distribution, and reproduction in anymedium, provided the original author(s) and source are credited.References1. Chasler C (1967) The newborn skull: the diagnosis of fracture.Am J Roentgenol Radium Ther Nucl Med 100(1):92–992. Weir P, Suttner NJ, Flynn P, McAuley D (2006) Normal skull suturevariant mimicking intentional injury. BMJ 332(7548):1020–10213. Franken EA Jr (1969) The midline occipital fissure: diagnosis offracture versus anatomic variants. Radiology 93(5):1043–10464. AllenWE 3rd, Kier EL, Rothman SL (1973) Pitfalls in the evaluationof skull trauma. A review. Radiol Clin N Am 11(3):479–5035. Nakahara K, Miyasaka Y, Takagi H, Kan S, Fujii K (2003)Unusual accessory cranial sutures in pediatric head trauma—casereport. Neurol Med Chir 43(2):80–816. Meservy CJ, Towbin R, McLaurin RL, Myers PA, Ball W (1987)Radiographic characteristics of skull fractures resulting from childabuse. Am J Roentgenol 149(1):173–1757. Hobbs CJ (1984) Skull fracture and the diagnosis of abuse. ArchDis Child 59(3):246–2528. Kleinman PK, Spevak MR (1992) Soft tissue swelling and acuteskull fractures. J Pediatr 121(5):737–7399. Fernando S, Obaldo RE, Walsh IR, Lowe LH (2008) Neuro-imaging of nonaccidental head trauma: pitfalls and controversies.Pediatr Radiol 38(8):827–83810. Nakahara K, Utsuki S, Shimizu S, Iida H et al (2006) Agedependence of fusion of primary occipital sutures: a radiographicstudy. Childs Nerv Syst 22(11):1457–145911. Kemp AM, Butler A, Morris S, Mann M et al (2006) Whichradiological investigations should be performed to identifyfractures in suspected child abuse? Clin Radiol 61(9):723–73612. Sty JR, Starshak RJ (1983) The role of bone scintigraphy in theevaluation of the suspected abused child. Radiology 146(2):369–375418 Emerg Radiol (2010) 17:413–418

Age dependence of fusion of primary occipital sutures: a radiographic study.

Neuroimaging of nonaccidental head trauma: pitfalls and controversies.

Normal skull suture variant mimicking intentional injury.

Pitfalls in theevaluation of skull trauma. A review.

Radiographic characteristics of skull fractures resulting from child abuse.

Skull fracture and the diagnosis of abuse.

Soft tissue swelling and acute skull fractures.

The midline occipital fissure: diagnosis of fracture versus anatomic variants.

The newborn skull: the diagnosis of fracture.

The role of bone scintigraphy in the evaluation of the suspected abused child.

Unusual accessory cranial sutures in pediatric head trauma—case report.

Which radiological investigations should be performed to identify fractures in suspected child abuse?

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Skull fracture vs. accessory sutures: how can we tell the difference?

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