growing fractures of thegrowthof both cranial vault andunderlying brain. at this hospital we have...

$: Growing fractures of thegrowthof both cranial vault andunderlying brain. At this hospital we have encountered only 10 cases in the past 10 years. These cases have been extensively$
Journal ofNeurology, Neurosurgery, and Psychiatry, 1978, 41, 312-318

Growing fractures of the skullDEREK KINGSLEY, KENNETH TILL, AND RICHARD HOARE

From The Hospital for Sick Children, Great Ormond Street, London

S U M M ARY Ten cases of growing fractures seen in the last 10 years are presented. Six of thepatients sustained their injury within the first six months of life. The defects formed rapidly,several within two or three months after injury. There was enlargement of the defect in only one

case after the date of discovery. Although the defects involved the parietal bone most commonly,in four out of 10 the lesion crossed either the coronal or the lambdoid suture. The edges of thedefects were usually thickened; in some areas they were saucer-shaped but in two cases therewas erosion of the outer table of the skull at a distance from the margin of the defect, theerosion being related to an extracranial fluid-filled cavity in continuity with a porencephalic cyst.The ipsilateral ventricle was usually dilated and in a number of cases was associated with a

porencephalic cyst. In no case was a "leptomeningeal cyst" found beneath the defect at opera-

tion. A detailed review confirms many of the findings previously descrbed but suggests that thepathology of the condition is still not fully understood. Computed tomography, undertaken in one

case, appears to be the examination of choice. Further light may be thrown on the pathogenesisof this condition by the use of intracystic, intrathecal, and intraventricular water-solublecontrast media.

Growing fractures of the skull are rare and almostunknown after the first few years of life. Theterm "growing fracture" was first used by Pia andTonnis (1953) in a major study published in theGerman literature. Before this publication, thecondition went under a number of different namesof which leptomeningeal cyst was probably thebest known (Dyke, 1938). In the same yearTaveras and Ransohoff (1953), in a study of sevencases treated by surgery, suggested that the singlemost important factor in its pathogenesis was adural tear. This, together with arachnoid adhesionsaided by normal pulsations of brain and perhaps aball valve mechanism, produced the enlargingbony defect.

In 1961 Lende and Erickson first reviewed theworld literature and reported clinical details ofthree cases. They emphasised that there were fouressential features: (1) a skull fracture in infancyor early childhood, (2) a dural tear at the time offracture, (3) brain injury beneath the fracture, and(4) subsequent enlargement of the fracture to forma cranial defect.However, while these features form an essential

part of the "syndrome", they are simply a mani-Address for reprint requests: Dr D. Kingsley, Lysholm RadiologicalDepartment, National Hospital, Queen Square, London WC1N 3BG,England.Accepted 25 October 1977

festation of the severe degree of trauma to theskull and brain occurring at a time of maximumgrowth of both cranial vault and underlying brain.At this hospital we have encountered only 10

cases in the past 10 years. These cases have beenextensively investigated and have enabled us toconfirm most of the previously documentedfeatures, but our observations suggest that lepto-meningeal cysts probably do not exist in this con-dition or, if they do occur, are very rare. Further-more, the changes in intracranial pathophysiologytogether with the dural tear are probably sufficientfor the development of such a defect. Case reportsof only two children are presented, both of whomhad unusual features.

Case reports

CASE 1In February 1975, at the age of 3 years and 5months, the patient fell 5 m from a school window.On admission to hospital she had bilateral peri-orbital haematomas, and skull radiographs re-vealed a left frontoparietal and left temporalfracture.

Six months after this episode she was noted tohave a collection of fluid under the scalp in theright frontal region associated with a palpable

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Growing fractutres of the skull

bony defect. The soft tissue swelling had refilledimmediately after aspiration at another hospital.

Skull radiographs showed a left frontal defectmeasuring 80X15 mm with extensive thinning ofthe outer table extending across the midline andinvolving much of the right frontal bone (Fig. 1).A pneumoencephalogram showed a bilocularporencephalic cyst connecting with a dilatedfrontal horn of the left lateral ventricle. The thirdventricle was displaced to the same side. No airwas seen over either hemisphere.At operation, atrophic brain was seen under-

lying the defect. The dura mater was absent andthe periosteum thickened but adherent to under-lying arachnoid mater. To the right of the defectthere was erosion of the outer table of the frontalbone with a fluid filled space lying deep to thepericranium and continuous with the intracranialcavity (Fig. 2). A rib graft was used to close thedefect and the patient made a satisfactory re-covery. Two and a half years later she remainswell with no neurological deficit.

CASE 2At the age of 3 months the patient was involvedin a road traffic accident. The child had a grosslycomminuted fracture of the left parietal regionextending across the midline with a severe righthemiparesis which, however, showed subsequentimprovement. At 5 months of age a pulsating de-fect was noted in the right parietal region, butthe parents reported that the defect had been en-larging from the time of injury. The child wasfound to have a squint. Skull radiographs showeda large defect in the left parietal region with eleva-

Fig. 2 Operative diagram (case 1) demon.strating theconnection between the subpericranial fluid collection,and porencephalic cyst, and the dilated left lateralventricle.

tion of the neighbouring skull vault. A pneumo-encephalogram showed a dilated left lateralventricle, particularly the trigone. The ventricleswere displaced to the left, and it was thought thata cyst was probably present under the defect. Airdid not reach the sulci on either side.At operation, cerebral cortex was found in the

defect and was firmly adherent to the overlyingperiosteum. An underlying porencephalic cyst waspresent but did not communicate with theventricle, and an opening was, therefore, madebetween the two to promote drainage. Post-operatively, a subcutaneous collection of cere-brospinal fluid developed over the defect, andsubsequent films suggested the development oflocal erosion of the outer table of bone im-mediately beneath the extracranial cyst (Fig. 3).

Fig. 1 (a) Posteroanterior skull radiograph of case 1 showing left frontal bone defect with thinning of theouter table extending across the midline to the righit side. (b) Tangential view of the defect showing erosionof the outer table.

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Derek Kingsley, Kenneth Till, and Richard Hoare

Fig. 3 (a) Postoperative appearances (case 2) demonstrating air in a cavity outside thte vault with overlyingsoft tissue swelling. (b) One month later. The extracranial cyst remains, and there is now erosion of theouter table immediately beneath. There is widening of the sutures due to raised intracranial pressure. (c)Three months later. The soft tissue swelling is smaller, the sutures are now normal, and the erosion of theouter table has become smooth.

Pneumoencephalography showed further dilatationof the left lateral ventricle which connectedthrough the defect with the extracranial cavity. Aventriculoatrial shunt was inserted but requirednumerous revisions over the next eight years. How-ever, for the past two years her condition hasremained stable. She attends a special school andcontinues to develop satisfactorily.

Analysis of cases

A summary of the clinical features is shown inthe Table.

AGE OF CHILD AT TIME OF INJURYTwo cases sustained birth trauma and the oldestpatient in this series was aged 3 years and 5months. Six of the 10 patients sustained theirinjury within the first six months of life, and allbut one within the first 18 months of life.

DEVELOPMENT OF BONE DEFECTThe shortest period between the head injury andthe discovery of the cranial defect was about twomonths. This occurred in the patient who was

savaged by a dog. In one other patient the defecthad developed within three months of injury, al-though in both of these patients the defectappeared to have enlarged gradually throughoutthis period. In two other patients the soft tissueswelling appeared three weeks after the injury.

NATURE OF DEFECTMost of the bone defects were of considerable size,the largest one measuring 100X70 mm. In one

case there were bilateral defects. Six of the defects

were confined to the parietal and one to thefrontal bone. Two were frontoparietal and oneparieto-occipital but did not reach the posteriorfossa. Defects crossed the sutures in four of the10 cases. The defects were normally irregular inshape and, in some cases, parts of the edge wereelevated. There was marked thickening of theedges particularly when the defect was of long-standing.

INTRACRANIAL ABNORMALITYEight of the 10 patients had pneumoencephalo-graphy. In each case there was dilatation of theipsilateral ventricle and in five of these there wasalso displacement of the third ventricle to theaffected side. In seven patients there was anassociated cyst. Six of these cysts were porence-phalic and four communicated with the lateralventricle. Leptomeningeal cysts were not demon-strated in any of the seven cases explored.

In two cases air was present in the sulci of theuninvolved hemisphere, but did not reach theconvexity of the affected side (Fig. 4). In no casedid air in the subarachnoid space fill any cavityin the region of the defect, a finding which wasexplained at surgery, where the meninges andunderlying brain were seen to be adherent to eachother in and around the bone defect.One patient was investigated by computed tom-

ography (CT) alone, and surgery was undertakenwithout any invasive diagnostic procedure. Com-puted tomography demonstrated the bone defectas well as the underlying ventricular dilatation andcystic cavity (Fig. 5). It is impossible to assess thepresence or absence of continuity with theventricle without the use of intraventricular or

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Fig. 4 Pneumoencephalogramndemonstrating many typicalfeatures: dilatation of theipsilateral ventricle towards thedefect; displacement of the thirdventricle to the left; air intcortical sulci on the right butnot on the left; thickenedsclerotic margin of the defectwith irregular bone erosion andexpansion.

Fig. 5 CT scan (case JU). Serial slices demonstrating the bone defect, dilatation of the left lateral ventriclewit/i overlying low attenuation probably due to a cyst, and some left hemisphere enlargement.

intracystic contrast media, and such studies maythrow further light on the pathogenesis of thiscondition. At present, however, CT gives sufficientinformation for the management of the patientand, where available, is the examination of choice.

Discussion

Most of the postnatal growth and differentiationof the brain and skull vault occurs within the firsttwo years of life, and by the end of this time theinner and outer tables, diploic spaces, diploic veins,vascular markings, and grooves on the internal sur-face of the calvaria are all present (Caffey, 1967).

In their review of the world literature up to

1960, Lende and Erickson (1961) reported thatover half of the fractures occurred under the ageof 12 months and that 90% of them occurredunder the age of 3 years. Our series agrees withthese findings, two-thirds of them occurring beforethe age of 1 year, and all but one under the ageof 3 years.The dura mater consists of two layers, the outer

one being in close contact with the bone andperiosteum. In childhood this relationship is evencloser (Schwartz, 1941) which may account forthe rarity of extradural haematomas at this age.It is not surprising, therefore, that major diastaticfractures of the bones of the vault are likely tocause tearing of the dura mater.

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A notable feature of this condition was the lackof neurological symptoms in our patients. Despitethe severe nature of the injury and the very con-siderable amount of underlying brain damagedemonstrated by pneumoencephalography, CTscanning, and at operation, only one patient hadgeneralised convulsions, three had mild hemiplegia,and one had a left convergent squint. Follow-uphas continued on eight of the children up to thepresent, the total period being up to 10 years. Twochildren still have a mild hemiparesis and one isslightly backward but the remainder are normal.

After the initial injury these fractures enlargerapidly, frequently reaching their full size withintwo months. Further absolute enlargement of thebone defect may occur over a longer period, andhas been encountered recently in one untreatedpatient (case 9, Table) radiographed again twoyears after initial diagnosis. The intracranial statehas not been documented up to the present.Although a dural tear with severe underlying

brain damage is necessary for the formation of agrowing fracture, uncertainty remains as to whythe defect should enlarge and, having reached acertain size, why it should cease to grow. In 1967Goldstein et al. published an experimental studyon enlarging skull fractures in young dogs. Theyfound a high incidence of enlarging bone lesionsin those groups where the defect was not limitedto the dura mater alone. However, in the groupwith a dural lesion but without damage to thearachnoid or pia mater, or to the underlying brainthere was no significant incidence of growingfracture. Similar experiments by Lende (1974)suggested, however, that bone defects do not healwhere there is an underlying dural defect, and thatunderlying brain damage does not alter the bonedefects. However, simulation of the naturalpathological state is extremely difficult to achieveand some doubt must remain as to the value ofthese experiments since the degree of intracranialdamage in vivo on both the ipsilateral and contra-lateral sides is likely to be more severe than thatexisting in the experimental state.Hakim (1973) has shown that any increase in

CSF pressure due to partial blockage of the drain-age pathway or overproduction of CSF will tendimmedia ely to compress the veins carrying bloodout of the cranial cavity, and will lead to ven-tricular enlargement. When the ventricles aresmall, quite large changes in CSF pressure arepossible with little change in the stress at the sub-dural level due to the elastic properties of thebrain tissue which reduce the stresses transmittedthrough it. However, when ventricles are large anyincrease in CSF pressure brings about an im-

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mediate and almost equal increase in subduralstress. It can be assumed that, after an injury tothe cranial vault of such magnitude as is requiredto produce a growing fracture, the normalequilibrium of production and absorption of thecerebrospinal fluid is temporarily upset. Fairlyrapidly, however, a new equilibrium is set up de-pendent upon changes in the ventricular size, thedevelopment of a porencephalic cyst, and thehealing processes of the damaged layers, at whichstage no further change is likely to occur in thesize of the defect.The shape of the defect depends on the relation-

ship between the forces tending to enlarge thedefect and those tending to produce healing ofthe skull fracture. Most defects are irregular andscalloped. In some patients areas of rarefactionand expansion coexist with markedly thickenededges. Occasionally a saucer-like appearance isseen with greater erosion of the outer table ofbone; but it must be rare for a large defect tooccur in the outer table as happened in case 1where persistence of a defect in the pseudoduraresulted in the development of a subgaleal cavityin continuity with the intracranial porencephaliccyst. The intracranial pressure was, therefore,transmitted into the subgaleal fluid collection withsubsequent pressure erosion of the outer table.That such erosion of the outer table can occur ata distance from the defect is further reinforced bycase 2. After surgical exploration of the defect, acystic space developed subpericranially in con-tinuity with the porencephalic cyst. Postopera-tively, the patient's course was stormy with evi-dence of raised intracranial pressure, and follow-upfilms suggested local erosions of the outer tablebeneath the cyst. It is likely, therefore, that trans-mission of pressure through a cystic cavity canproduce erosion of the outer table of the skulladjacent to the fracture site in much the sameway as does a pulsatile aortic aneurysm of thedorsal vertebral bodies.Dyke (1938) was the first to use the title "lepto-

meningeal cyst" when he suggested that aftersevere trauma with skull fractures "loculated fluidfilled cysts develop and owing to pulsations of thebrain the overlying bone is absorbed."

Later Taveras and Ransohoff (1953), in theirstudy of seven cases, suggested that such cystsformed between pia and arachnoid membranes,and that there was herniation of arachnoid materthrough the defect. In all their cases they foundcystic structures beneath the defects but the exactposition of these cysts is uncertain. No commentwas made on the relationship of the cysts to thesurrounding brain tissue. Lende and Erickson

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(1961) referred to the term "leptomeningeal cyst"but noted that they had not encountered any suchcyst-like structures in their cases. They suggest,however, that such cysts may sometimes occurafter local injury, but, in a later paper, Lende(1974) considered such cysts to be rare whilePenfield, in a discussion of a paper by Caffey(1954), suggested that there might be brain ratherthan a leptomeningeal cyst between the edges ofthe skull defect. Our experience confirms that ofLende and Erickson and of Penfield. At operationthe pia and arachnoid membranes were mattedtogether and stuck both to the edge of the defectand to the underlying atrophic brain. The edgesof the defect were abnormally thick and the inter-vening area usually filled with fibrous tissue. Inno case was there any evidence of a leptomeningealcyst. Occasionally cysts have been described situ-ated between the fibrous tissue and underlyingcortex, but these are small and rare, and it seemsinconceivable that they can contribute to theenlargement of the defect. It appears, therefore,that "leptomeningeal cysts" are very rare andprobably of little importance, and that almost allthe cysts that are demonstrated are porencephalic,related to the severe brain trauma, whether or notthey communicate with the ventricles.

References

Caffey, J. (1954). Some radiological features oftraumatic lesions in the growing skull. Research

Publications. Association for Research in Nervousand Mental Diseases, 34, 341-350.

Caffey, J. (1967). In Pediatric X-Ray Diagnosis. Fifthedition, pp. 1-20. Yearbook Medical Publishers:Chicago.

Dyke, C. G. (1938). The roentgen ray diagnosis ofdiseases of the skull and intracranial contents. InDiagnostic Roentgenology, Vol. 1, pp. 1-34. Editedby W. Golden. Williams and Wilkins: Baltimore.

Goldstein, F., Sakoda, T., Keped, J. J., Davidson, K.,and Brackett, C. E. (1967). Enlarging skull fractures.An experimental study. Journal of Neurosurgery,27, 541-550.

Hakim, S. (1973). Hydraulic and mechanical mis-matching of valve shunts used in the treatment ofhydrocephalus: the need for a servo valve shunt.Developmental Medicine and Child Neurology, 15,646-653.

Lende, R. A. (1974). Enlarging skull fracture ofchildhood. Neuroradiology, 7, 11 9-124.

Lende, R. A., and Erickson, T. C. (1961). Growingfractures of childhood. Journal of Neurosurgery,18, 479-489.

Pia, H-W., and Tonnis, W. (1953). Die WachsendeSchadelfractur des Kindesalters. Zentralblatt fiurNeurochirurgie, 13, 1-23.

Schwartz, C. W. (1941). Leptomeningeal cysts from aroentgenological viewpoint. A merican Journal ofRoentgenology, 46, 160-165.

Taveras, J. M., and Ransohoff, J. (1953). Lepto-meningeal cysts of the brain following trauma witherosion of the skull. A study of seven cases treatedby surgery. Journal of Neurosurgery, 10, 233-241.

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