REVIEW ARTICLE

ACTA RADIOLOGICA

Calvarial Lesions: A Radiological Approach to Diagnosis I. LLORET1, A. SERVER2 & I. TAKSDAL1 1 Department of Radiology, Oslo University Hospital/The Norwegian Radium Hospital, Oslo, Norway; 2Department of Radiology, Oslo University Hospital, Ulleva˚l, Oslo, Norway

Lloret I, Server A, Taksdal I. Calvarial lesions: a radiological approach to diagnosis. Acta Radiol 2009;50:531
542. Calvarial lesions are frequently identified in radiological studies. A wide variety of neoplasms and non-neoplastic lesions can involve the calvarium, and their imaging appearances vary according to their pathologic features. These lesions are usually asymptomatic but may manifest as a lump with or without associated pain. Clinical information, including the age of patient, is an important factor in the diagnostic process. In this paper, we illustrate the value of cross-sectional imaging techniques by computed tomography (CT) and magnetic resonance imaging (MRI) in evaluating these lesions. We also review the literature and discuss the specific imaging characteristics of the most common calvarial lesions in order to provide information that can guide radiological diagnosis or limit differential diagnosis. Key words: Calvarium; CT; lesions; MRI; neoplasm Isabel Lloret, Section of Oncology, Department of Radiology, Oslo University Hospital/ Norwegian Radium Hospital, Oslo, Norway (fax. 47 22935943, e-mail. isabel.lloret@ radiumhospitalet.no) Accepted for publication January 23, 2009

Calvarial lesions are often asymptomatic and incidentally discovered on radiological images obtained for other reasons. Clinical suspicion is based on localized pain or the finding of a visible or palpable mass or defect. Primary neoplasms of the calvarium account for 0.8% of all bone tumors. Benign lesions are more common than primary malignancies, but the precise prevalence of each has not been defined because biopsy is not performed on many benign lesions (1). Radiological evaluation of a patient who presents with a calvarial lesion often requires cross-sectional imaging by computed tomography (CT) and magnetic resonance imaging (MRI). Multidetector CT (MDCT), with multiplanar reformatted images, is the most accurate method for evaluating bone destruction, the involvement of the skull tables and diploe¨, and mineralized tumor matrix. CT is also useful in guiding biopsy to diagnose these lesions. MRI is the best imaging modality for identification of lesions in the fat-containing diploic marrow, for evaluation of intracranial and extracranial soft-tissue extension, and for characterization of the matrix of the lesion. CT and MRI can evaluate contrast enhancement of the lesion, but the enhancement pattern is best evaluated on fat-

saturated T1-weighted MR images. Plain radiography plays a lesser role but can sometimes localize a palpable mass or defect. Bone scans can be performed when multiple lesions with increased radionuclide uptake are suspected. Cerebral angiography, or MR venography and angiography occasionally are used to evaluate lesions that appear vascular or that may invade major sinuses (1
3). In many cases, biopsy is warranted in order to diagnose, but some bioptic material may not be histologically representative of the whole lesion, thus clinical-radiological-pathologic correlation is essential in order to make a more accurate diagnosis (1
6). In this paper, we reviewed the records of 61 patients with calvarial lesions referred to the National Resource Center for Sarcomas at the Norwegian Radium Hospital during the period of 1997 to 2007. The majority of primary radiological studies were done in other hospitals and in most of cases using MR and CT imaging. Core or fineneedle aspiration cytology (FNAC) was performed in 46% of cases, and benign lesions without biopsy had follow-up for at least 1 year. The most common lesions encountered were osteoma (26%), eosinophilic granuloma (18%), fibrous dysplasia (20%),

DOI 10.1080/02841850902795274 # 2009 Informa UK Ltd. (Informa Healthcare, Taylor & Francis AS)

532

I. Lloret et al.

osseous hemangioma (13%), epidermoid cyst (7%), miscellaneous benign lesions (8%), and osteosarcoma (8%) (Fig. 1). Note that the most frequent calvarial tumors*multiple metastases and multiple myeloma*were not referred to our resource center. This article illustrates the value of cross-sectional imaging techniques by CT and MRI in evaluating a calvarial lesion. We also review the literature and describe the characteristic imaging appearances of the most common calvarial lesions, in order to provide information that can lead to a specific radiological diagnosis or to limit the differential diagnosis.

Table 1. Radiological features for evaluation of a calvarial lesion Site of origin

Scalp, outer table, diploe¨, inner table, extra- or intraaxial space Size Small, large Number Single or multiple Pattern of bone destruction Geographic, ‘‘moth-eaten,’’ or permeated Margins Well-defined border, sclerotic rim, ill-defined margin, narrow or wide transitional zone Periosteal reaction Uninterrupted or interrupted pattern Soft-tissue component and Intra- or extracranial extension local extension Type of matrix Bone forming, cartilage forming, connective tissue and vascular tumors, fatty, cystic, or hemorrhagic contents

Clinical and radiological features for evaluation of a calvarial lesion Patient age, symptoms, clinical history, and laboratory findings are important clinical factors in making radiological diagnosis. The imaging appearance of calvarial lesions can indicate the lesion growth rate, and sometimes suggest a specific diagnosis or limit the differential diagnosis. Systematic analysis of certain radiological features can be used for imaging evaluation of a calvarial lesion (3, 6, 7), as summarized in Table 1. Anatomic site of origin Calvarial lesions can originate within the calvarium (primary lesions), or invade the calvarium from the scalp or meninges. The calvarium is composed of a cortical outer table, marrow space (diploe¨), and a cortical inner table. The calvarium comprises mainly the frontal bone, parietal bone, occipital bone, and temporal bone, and parts of the zygoma and the greater wing of the sphenoid bone, separated by sutures. The scalp consists of the skin,

connective tissue (subcutaneous), galea aponeurotica, and loose connective tissue (subgaleal). The outer table is covered by periosteum. The dura mater is the outer membrane of the meninges. The arachnoid is a delicate avascular membrane beneath the dura, and the pia mater is a thin connective tissue membrane that covers the brain surface. The extraaxial compartment comprises epidural space, subdural space, and subarachnoid space. The site of origin of calvarial lesions can be characteristic of a specific entity. For example, a compact mature bone tumor arising from the outer table is highly suggestive of osteoma. Size and number of lesions The number of lesions, either single or multiple, can suggest a specific diagnosis. For example, in patients over 50 years of age, multiple osteolytic lesions with variable size are highly suggestive of multiple metastases. Pattern of bone destruction and margins (transitional zone) Benign tumors usually exhibit geographic/sharp bone destruction and a clear narrow transitional zone between normal and abnormal bone. Sclerotic margin may be present. Aggressive tumors often have poorly defined, moth-eaten or permeated bone destruction and a wide zone of transition.

Fig. 1. Distribution of calvarial lesions referred to the National Resource Center for Sarcomas at the Norwegian Radium Hospital from 1997 to 2007. Acta Radiol 2009 (5)

Periosteal reaction A unilamellated uninterrupted pattern is usually associated with slow-growing lesions, and an interrupted periosteal reaction signifies an aggressive lesion.

Diagnosis of Calvarial Lesions

Soft-tissue component and local extension Malignant tumors often have a soft-tissue component that can extend to the scalp or to extraaxial spaces and/or the cerebral cortex. Type of matrix and internal characteristics The type of tumor matrix or other internal characteristics can suggest a specific diagnosis. Chondroid- and osteoid-producing tumors are usually easily detected on CT. Bone-forming tumors most often display amorphous or cloud-like mineralization, but the amount and degree of matrix mineralization are widely variable. Cartilage-forming tumors typically exhibit punctuate, comma-like, ring, or popcorn-like mineralization. Non-mineralized chondroid matrix, vascular tissue, fibrous matrix, and fatty, cystic, hemorrhagic contents within the lesions are more easily detected on MRI. Classification of calvarial lesions A wide variety of abnormalities can involve the calvarium. Calvarial lesions can be categorized into true neoplasms (benign and malignant bone neoplasms) and non-neoplastic lesions, which represent congenital, traumatic, metabolic, hematologic, infectious, and idiopathic conditions (1, 3, 6). The most important lesions of the calvarium are listed in Tables 2 and 3. Cephalocele The term cephalocele refers to a defect in the skull and dura, with extracranial extension of intracranial structures (7). Cephaloceles are divided into four Table 2. Non-neoplastic lesions of calvarium Congenital anomalies and normal variants

Trauma

Hematologic disease Idiopathic disorders

Metabolic disease Infection * Also included in neoplasms.

533

Table 3. Neoplasms of calvarium Benign Osteoma Osseous hemangioma Fibrous dysplasia Mengioma Ossifying fibroma Aneurysmal bone cyst Giant cell tumor Osteoid osteoma Osteoblastoma Osteochondroma Chondroma Desmoplastic fibroma Chondroblastoma Chondromyxoid fibroma Lipoma Hemangioendothelioma Lymphangioma Neurilemmoma Myofibroma Malignant Metastases Multiple myeloma/plasmocytoma Osteosarcoma Angiosarcoma Chondrosarcoma Ewing sarcoma Fibrosarcoma Rhabdomyosarcoma Lymphoma

types: meningoencephaloceles are herniations of the cerebrospinal fluid (CSF), brain tissue, and meninges through the skull defect; meningocele refers to herniation of the meninges and CFS only; glioceles consist of a glial-lined cyst containing CSF; and atretic cephalocele consists of dura, fibrous tissue, and degenerated brain tissue (7, 8). There are often significant associated intracranial anomalies (8, 9).

Epidermoid, dermoid cyst Cephalocele Sinus pericranii Fibrous dysplasia* Parietal foramina Pacchionian granulations Venous lakes Surgical burr holes Leptomeningeal cyst Cephalohematoma Chronic severe anemias Langerhans cell histiocytosis (histiocytosis X) Osteitis deformans (Paget disease of bone)

Imaging appearance. MRI is superior to CT in the evaluation of cephaloceles, because MRI directly shows the extension of brain tissue through the bone defect, and defines the contents of cephalocele prior to surgery (9). CT may be used to display bone anatomy. Atretic cephaloceles (Fig. 2) are typically parietal in location (9), and certain characteristic findings on MR images and CT scans can provide clues to the diagnosis of atretic cephaloceles (10). Epidermoids and dermoids Epidermoids and dermoids are ectodermal inclusion cysts lined by epithelium. Epidermoids only have a squamous epithelium. Dermoids contain hair, Acta Radiol 2009 (5)

534

I. Lloret et al.

Fig. 2. Atretic parietal cephalocele in a 2-week-old girl. A. Sagittal T2-weighted MR image shows a hyperintense subcutaneous mass. Note that the brain tissue is not entering the cephalocele. B. MR venogram demonstrates a vertically persistent falcine sinus (white arrow).

sebaceous and sweat glands, and squamous epithelium. They commonly occur in the calvarium, orbit, and intracranially (the posterior and middle fossae). The majority of epidermoid and dermoid cysts are congenital, and are rarely due to traumatic or iatrogenic implantation (11). Clinically, they usually manifest as non-tender, slowly expanding masses, enlarging over years or decades (3). Most of these lesions present in the first four decades of life. Dermoid cysts of the posterior fossa may be noted earlier in infants. Epidermoids are typically lateral in location, and dermoids are usually found in the midline (11). Imaging appearance. Dermoids and epidermoids typically appear as encapsulated, unilocular cystic lesions, and the appearance of the cyst contents

varies depending on its composition (12). On CT, epidermoids appear as intradiploic, expansile, osteolytic lesions with smooth sclerotic margins. These lesions often expand, remodel, and can erode the outer and inner tables (Fig. 3). Rarely, epidermoids have increased attenuation due to formation of calcium soaps (3). Dermoids appear as expansile, osteolytic midline lesions with a soft-tissue component extending to overlying skin and intracranial (Fig. 4). MRI is superior to CT in showing the extension of the soft-tissue component. Most dermoids, in contrast to epidermoids, have the attenuation and signal intensity characteristics of lipid material because of their sebaceous secretions (12). Unlike epidermoids, dermoids usually have a thick wall that enhances with intravenous contrast media (11).

Fig. 3. Epidermoid cyst in a 56-year-old woman. A. Axial CT scan shows a well-defined, osteolytic lesion centered within the diploe¨ in the frontal bone. The margins are smooth and sclerotic, and there is expansion and remodeling of the outer table and erosion of the inner table. B. Axial T2-weighted MRI shows a heterogeneous hyperintense lesion. C. Coronal contrast-enhanced T1-weighted MR image demonstrates the cystic component of the lesion. Acta Radiol 2009 (5)

Diagnosis of Calvarial Lesions

535

Fig. 4. Dermoid cyst in a 1-year-old boy. A. Axial CT scan shows a midline lesion with unilocular cystic soft-tissue component extending to overlying skin. B. Axial T2-weighted image demonstrates the homogeneous cystic component of the lesion.

Calcified cephalohematoma Cephalohematoma is a subperiosteal hemorrhage confined by the cranial sutures. The majority of cephalohematomas spontaneously resorb by 1 month of age (13) and overlie the parietal bone (3). In cases where the hematomas fail to resorb, progressive subpericranial osteogenesis results in a calcified cephalohematoma. The incidence of calcification of cephalohematomas has been reported to occur in 3
5% of all cephalohematomas (13). Imaging appearance. CT is the definitive standard for assessment of calcified cephalohematomas. CT features include a uniformly homogeneous, hypodense, non-enhancing core encased by bone (13). In cases that present late (3
6 months), the cephalohematoma feels hard (13), and both plain radiography and CT (3) show a uniform, densely calcified mass that is located immediately adjacent to the outer table and is contained within the periostium. The diploic space and inner table remain intact; unless the lesion is so large that it buckles the calvarium inward (3). Leptomeningeal cyst Linear or non-linear skull fractures in children that enlarge with time are termed growing skull fractures (14, 15). These lesions occur mostly in children under 3 years of age (90%) as a rare complication of head injury (15, 16). They are characterized by the association of a skull fracture with an underlying dural tear that inhibits healing of the fracture because the torn meninges are interposed between

the fractured fragments. They tend to enlarge with time due to the relentless effect of CSF pulsation paralleling the growth of the skull and brain. Progressive enlargement may be associated with herniation of meninges and brain tissue (14, 17). Early diagnosis is crucial, since brain damage is progressive in the absence of surgical treatment (14). Imaging appearance. CT detects both the skull defect and the cyst, whose density parallels that of CSF. On MRI (Fig. 5), the cyst is isointense with CSF on all MRI sequences and communicates with the subarachnoid spaces (14). Herniation of brain tissue may occur, resulting in acquired internal cephalocele. Encephalomalacia of the underlying brain tissue appears as low density on CT and as T1 and T2 prolongation on MRI (18). Langerhans cell histiocytosis Langerhans cell histiocytosis (LCH), formerly known as histiocytosis X, is a disorder characterized by idiopathic proliferation of Langerhans cells, an immature dendritic cell of bone marrow origin (12). LCH may occur at any age, but is most frequent in children or young adults (19). Langerhans cell histiocytosis comprises three clinical syndromes: eosinophilic granuloma, the least aggressive form, limited to bone or lung and often monostotic; Hand-Schuller-Christian disease, characterized by calvarial lesions, exophthalmos, and diabetes insipidus; and Letterer-Siwe disease, the acute disseminated form that affects multiple visceral organs, Acta Radiol 2009 (5)

536

I. Lloret et al.

Fig. 5. Leptomeningeal cyst in a 2-year-old boy. A. Axial CT scan demonstrates a left parietal diastatic fracture. One year later, axial FLAIR and T2-weighted images (B, C) show a cystic mass filled with cerebrospinal fluid at the enlarging fracture site (leptomeningeal cyst), lined by damaged and gliotic brain.

often with fatal consequences (12, 19). Up to 80% of LCH is eosinophilic granuloma. Up to 90% occur in bone, and the calvarium is the most frequently involved (12, 19). Clinical presentation and course vary with the extent of the disease and the specific organs involved. Patients may present local pain and palpable tender enlarging calvarial masses that can progress, coalesce, or regress (20). Imaging appearance. The radiographic appearance depends on the form and phase of the disease (19). Early in the disease, lesions appear rapidly and are aggressive-looking. On CT, eosinophilic granuloma appears as an intradiploic, sharply demarcated or punched-out osteolytic lesion without sclerotic rim or periosteal reaction. Its edges may be beveled, due to usually asymmetric involvement of the outer and

inner tables. A ‘‘button sequestrum,’’ a central residual bone density within the osteolytic lesion, may be present (Fig. 6). Lytic lesions may be multiple and may coalesce, giving the characteristic ‘‘geographic’’ appearance (19
21). MR imaging is a highly sensitive modality in detecting bone marrow involvement and the soft-tissue component that may extend subgaleally or epidurally. Eosinophilic granuloma shows marked contrast enhancement and often reactive dural and galeal enhancement. Later, healing lesions become well demarcated and progressively sclerotic, with resolution of the softtissue component (19). Osteoma Osteoma is the most frequent benign bone tumor of the adult skull (1). Osteoma is a juxtacortical tumor

Fig. 6. Eosinophilic granuloma in a 27-year-old woman. Coronal (A) and sagittal (B) CT images show a well-defined ‘‘punched out’’ osteolytic lesion in the left parietal bone. There is an asymmetric involvement of the inner and outer tables, and a ‘‘button sequestrum’’ is present within the eosinophilic granuloma. C. Coronal fat-saturated T1-weighted image after contrast administration shows marked enhancement of the lesion and reactive dural and subgaleal enhancement. Acta Radiol 2009 (5)

Diagnosis of Calvarial Lesions

characterized by proliferation of compact and/or cancellous bone. Osteomas usually arise from the outer table and only rarely from the inner table (21). When arising from the inner table, they can be misdiagnosed as calcified meningiomas (22). Osteoma may manifest as a solitary painless mass. Multiple lesions suggest the diagnosis of Gardner syndrome, a disorder characterized by multiple osteomas, colonic polyposis, and various benign tumors, such as lipomas, fibromas, and sebaceous cysts (1, 4, 21). Imaging appearance. On CT, osteoma typically shows a juxtacortical, well-defined sclerotic lesion with preservation of diploe¨ (1) (Fig. 7). On MRI, these lesions are hypointense on T1-weighted images. On T2-weighted imaging, the signal intensities vary with the amount of compact and cancellous bone. These tumors show no contrast enhancement and no soft-tissue component on CT and MRI (21, 22). Osseous hemangioma Vascular lesions of bone and soft tissue are common musculoskeletal tumors. The two most common anatomic sites of involvement are the vertebra and the calvarium. Hemangiomas may be

Fig. 7. Osteoma in a 53-year-old woman. Axial CT shows an ovoid, dense sclerotic lesion related to the outer table of the left parietal bone.

537

found in patients of all ages but are usually discovered in the middle decades of life (23, 24). Most osseous hemangiomas are small and asymptomatic, but lesions may grow slowly, causing pain and visible or palpable deformity of bone. They may affect any location in the calvarium, but they are most often seen in the frontal or parietal bones. Histopathologically, most of the calvarial hemangiomas are of the cavernous type (21, 23
25). Imaging appearance. At plain radiography and CT, a calvarial hemangioma commonly appears as a well-defined osteolytic lesion with a characteristic ‘‘sunburst’’ or ‘‘honeycomb’’ trabecular pattern, representing thickened trabeculae adjacent to the angiomatous channels. These lesions arise in the diploic space and cause expansion of the outer table with relative sparing of the inner table (Fig. 8). Periosteal reaction is rare (23). MRI can easily recognize the serpentine vascular channels, suggestive of a vascular lesion, and can clearly define the extent of the lesion and its relationship to adjacent neurovascular structures (21). Hemangiomas enhance diffusely and heterogeneously after contrast medium administration (25). Occasionally, a hemangioma may become aggressive, with an intra- or extracranial soft-tissue component that may simulate a malignant neoplasm (24, 25). Fibrous dysplasia Fibrous dysplasia is a common skeletal lesion in adolescents and young adults that may affect the calvarium (26). Fibrous dysplasia is usually regarded as a non-neoplastic development disorder of bone characterized by replacement of normal bone marrow by fibro-osseous tissue. More recent studies regard it as a benign non-encapsulated neoplasm (27). Fibrous dysplasia can present in a monostotic or polyostotic form, and the monostotic form occurs in 70
80% of cases (12). Calvarial fibrous dysplasia commonly crosses bony sutures, and, as such, monostotic lesions may involve multiple calvarial bones. Most small calvarial lesions are asymptomatic and are identified incidentally. More expansile lesions usually grow outward and present with firm swelling (27). Rarely, polyostotic fibrous dysplasia may be associated with McCune-Albright syndrome and Mazabraud syndrome. Malignant transformation of fibrous dysplasia occurs very infrequently, with reported prevalence ranging from 0.4% to 4% (26). Acta Radiol 2009 (5)

538

I. Lloret et al.

Fig. 8. Osseous hemangioma in a 36-year-old man. A. Axial CT reveals a well-defined, intradiploic, osteolytic lesion containing radiating prominent trabeculae in the left frontal bone. The lesion is slightly expansive with involvement of the outer table to a greater extent than the inner table. B. Axial T2-weighted MRI shows a heterogeneous hyperintense lesion. There is no surrounding edema, and no soft-tissue components are evident.

Imaging appearance. CT scanning is the best technique for demonstrating the radiological characteristics of fibrous dysplasia (26). CT typically shows an intradiploic, expansile lesion with a characteristic ‘‘ground glass’’ density (Fig. 9). The outer table is usually more prominently affected, compared with the inner table (4, 12). On CT, three patterns of craniofacial fibrous dysplasia can be observed: a mixed pattern with lytic and sclerotic regions; a homogeneously sclerotic and predominantly cystic or lytic pattern; but, in most cases, at least some component of the typical ground-glass bone pattern is seen (27). Fibrous dysplasia has differing MRI appearances, reflecting the variable tissue components of this entity. Enhancement after contrast media is variable,

with homogeneous, central, or peripheral patterns described (27). Meningioma Meningiomas are the most common primary nonglial intracranial tumors in middle-aged and elderly patients (28). One of the best-known findings of meningioma is hyperostosis of the adjacent calvarium (29). The appearance of the hyperostosis may be simple eburnation without bone thickening or may include marked bone thickening with irregularity that can even produce outward growth of the outer table of the skull in advanced cases (29). A specific type of meningioma causing significant hyperostosis is plaque meningioma. This type of meningioma consists of a relatively thin layer of neoplasm of the

Fig. 9. Fibrous dysplasia in a 20-year-old man. A. Axial CT image shows an expansive intradiploic frontal lesion with a typical ‘‘ground glass’’ appearance. B. Axial T2-weighted image shows low to intermediate signal intensity with scattered areas of high signal intensities. C. Axial fat-saturated, contrast-enhanced T1-weighted image shows areas with and without contrast enhancement. Acta Radiol 2009 (5)

Diagnosis of Calvarial Lesions

539

Fig. 10. Meningioma in a 48-year-old woman. A. Axial CT shows an expanded hyperostosis of the left sphenoid bone. B. Axial T2-weighted MRI demonstrates the extraaxial tumor adjacent to the left sphenoid bone and the soft-tissue component extending into the orbit. C. Axial contrast-enhanced T1-weighted image demonstrates the intense and homogeneous contrast enhancement of meningioma.

adjacent inner table (29). Extradural meningioma arises in locations other than the dura mater, and comprises 1
2% of all meningiomas (30). Primary intraosseous meningioma is a term used to describe a subset of extradural meningiomas that arise in bone (30). Imaging appearance. The hyperostosis associated with a meningioma is typically smooth and conforms to the normal curve of the inner table of the skull (29). The radiographic appearance of intraosseous meningioma is either of the osteoblastic or the osteolytic subtype, although mixed versions have been reported (30). Osteoblastic intraosseous meningiomas may induce hyperostosis (30, 31), which may mimic fibrous dysplasia (32). The tumor is usually hyperdense on a non-enhanced CT scan and enhances densely after contrast administration (Fig.

10). Primary intraosseous meningioma may produce an osteolytic skull lesion that causes thinning, expansion, and interruption of the inner and outer cortical layers of the skull (33). MRI findings for both osteolytic and osteoblastic subtypes of intraosseous meningiomas are similar to those of intradural lesions and allow better delineation of tumors that have extracalvarial soft-tissue extension. Prominent homogeneous enhancement after contrast administration is typical (30). Metastases Metastases are the most common malignant bone tumors in adults after the fifth decade of life. Patients presenting with skull metastases are often in an advanced stage of cancer, but most metastatic skull lesions are asymptomatic (34) or cause local swelling that is usually painless. Nearly all types of

Fig. 11. Metastases in a 21-year-old woman with Ewing sarcoma. A. Axial CT shows massive destruction of the right parietal bone and a large soft-tissue mass. B. Axial T2-weighted image demonstrates intermediate signal intensity in the large extraaxial and subgaleal soft-tissue mass. C. Coronal contrast-enhanced T1-weighted image reveals homogeneous enhancement. Acta Radiol 2009 (5)

540

I. Lloret et al.

Fig. 12. Multiple myeloma in a 69-year-old man following chemotherapy. A. Axial T2-weighted image shows multiple well-defined hyperintense lesions in the diploic marrow of the skull. Axial (B) and coronal (C) contrast-enhanced T1-weighted images reveal rim-like enhancement of the lesions.

malignant tumors can cause calvarial metastases, but breast cancer is associated with the highest rate of metastatic calvarial lesions in adults (34). In children, the malignant tumor that most commonly involves the calvarium is neuroblastoma (1, 12, 21). Imaging appearance. Plain radiographs and CT scans typically demonstrate multiple lesions of variable size with poorly defined margins. Metastases may have an osteolytic, sclerotic, or mixed pattern. CT is the best modality in determining the extent of bone destruction (34). MRI, especially fatsuppressed images, more clearly shows small lesions and the intradiploic and intracranial extent of the lesion. Metastases usually enhance markedly on CT and on MRI (21, 34) (Fig. 11).

Multiple myeloma Multiple myeloma is the most common primary malignant neoplasm in adults after the fourth decade of life. Multiple myeloma is a malignant bone marrow disorder, characterized by uncontrolled excessive proliferation of atypical plasma cell clones and consecutive destruction of the bony architecture. The skeletal, and hence calvarial, involvement can be diffuse or multifocal. Plasmocytoma represents the focal solitary form of this neoplasm. Bone marrow biopsy or aspirate is essential for diagnosis (35, 36). Imaging appearance. Plain film radiography and cross-sectional imaging play an important role in staging, monitoring treatment response, detecting relapse, and assessing complications in multiple

Fig. 13. Osteosarcoma in a 38-year-old man. A. Axial CT depicts a large parietal osteolytic lesion with spiculated periosteal reaction. B. Coronal contrast-enhanced T1-weighted image demonstrates intense enhancement of the large mass. Acta Radiol 2009 (5)

Diagnosis of Calvarial Lesions

541

Fig. 14. Angiosarcoma in an 84-year-old woman. A. Coronal CT depicts poorly defined destruction of parietal bone. B. Coronal contrastenhanced T1-weighted image reveals an expansile calvarial mass with intense heterogeneous enhancement, extending into the scalp and intracranial cavity.

myeloma. CT enables more precise analysis of bone destruction and assessment of the presence and extent of soft-tissue involvement than plain radiographs. CT findings in multiple myeloma include sharp, lytic foci of small and relatively homogeneous size with no sclerotic rim, diffuse faint osteolysis, an angioma-like appearance, and expansile deposits (35). MRI is superior to radiography for detecting focal or diffuse bone marrow involvement. Five different infiltration patterns can be differentiated in MRI: normal appearance of bone marrow despite minor microscopic plasma cell infiltration, focal involvement (Fig. 12), homogeneous diffuse infiltration, combined diffuse and focal infiltration, and a ‘‘salt and pepper’’ pattern with inhomogeneous bone marrow with interposition of fat islands (36). Bone sarcomas Bone sarcomas arising from the skull are rare, with most articles reporting single cases (Table 2). Osteosarcoma is a malignant mesenchymal neoplasm in which the tumor cells directly produce osteoid or immature bone. Many lesions also contain other elements, particularly fibrous or chondroid components. Numerous histological types of osteosarcoma have been described (37
39). As elsewhere in the body, calvarial osteosarcomas may arise either de novo (primary) or secondary to other disorders, mainly Paget disease and post radiation therapy. Unlike osteosarcomas of the extremities, calvarial osteosarcomas occur mainly in the third and fourth decades of life (37
40). The imaging appearance of osteosarcoma varies according specific histological types. On CT, osteosarcomas com-

monly have an osteolytic appearance with a variable amount of osteoid and/or chondroid mineralization and ill-defined border. MRI is the modality of choice for preoperative evaluation and staging of osteosarcoma (38, 39) (Fig. 13). Angiosarcoma is a high-grade form of hemangioendothelioma, with a very aggressive nature. Calvarial angiosarcoma often appears as a large expansile osteolytic lesion with large soft-tissue masses extending both extra- and intracranially. These tumors usually show marked heterogeneous enhancement after contrast media administration (41) (Fig. 14). Conclusion In conclusion, a wide spectrum of neoplasms and non-neoplastic lesions can involve the calvarium, and the pathologic features of these lesions influence their radiologic appearance. The recognition of the radiologic appearances of calvarial lesions usually allows a prospective diagnosis, which can guide optimal clinical management and therapy. Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

References 1. Shah MV, Haines SJ. Pediatric skull, skull base, and meningeal tumors. Neurosurg Clin N Am 1992;3:893
924. Acta Radiol 2009 (5)

542

I. Lloret et al.

2. Resnick D. Tumors and tumor-like lesions of bone. In: Resnick D, editor. Diagnosis of bone and joint disorders. Philadelphia, PA: Saunders; 2002. p. 3745
66. 3. Ortiz O, Schochet S, Bastug D. Imaging evaluation and clinicopathologic correlation of mass lesions involving the calvaria. Part I: congenital and traumatic lesions. Int J Neuroradiol 1999;5:96
108. 4. Arana E, Marti-Bonmati L. CT and MR imaging of focal calvarial lesions. Am J Roentgenol 1999;172: 1683
8. 5. Priolo F, Cerase A. The current role of radiography in the assessment of skeletal tumors and tumor-like lesions. Eur J Radiol 1998;27(Suppl 11):77
85. 6. Miller TT. Bone tumors and tumorlike conditions: analysis with conventional radiography. Radiology 2008;246:662
74. 7. Barkovich AJ. Congenital malformations of the brain and the skull. In: Barkovich AJ, editor. Pediatric neuroimaging. Philadelphia, PA: Lippincott Williams & Wilkins; 2005. p. 291. 8. Naidich TP, Altman NR, Braffman BH, McLone DG, Zimmerman RA. Cephaloceles and related malformations. Am J Neuroradiol 1992;13:655
90. 9. Moro`n FE, Morriss MC, Jones JJ, Hunter JV. Lumps and bumps on the head in children: use of CT and MR imaging in solving the clinical diagnostic dilemma. Radiographics 2004;24:1655
74. 10. Patterson RJ, Egelhoff JC, Crone KR, Ball WS. Atretic parietal cephaloceles revisited: an enlarging clinical and imaging spectrum? Am J Neuroradiol 1998;19:791
5. 11. Smirniotopuolos JG, Chiechi MV. Teratomas, dermoides and epidermoides of head and neck. Radiographics 1995;15:1437
55. 12. Chung EM, Murphey MD, Specht CS, Cube R, Smirniotopoulos JG. Pediatric orbit tumors and tumorlike lesions: osseous lesions of the orbit. Radiographics 2008;28:1193
214. 13. Wong CH, Foo CL, Seow WT. Calcified cephalohematoma: classification, indications for surgery and techniques. J Craniofac Surg 2006;17:970
9. 14. Tortori-Donati P, Rossi A, Biancheri R. Accidental head trauma. In: Tortori-Donati P, editor. Pediatric neuroradiology. Berlin: Springer; 2005. p. 893. 15. Naim-Ur-Rahman, Jamgoon Z, Jamgoon A, Murshid WR. Growing skull fractures: classification and management. Br J Neurosurg 1994;8:667
79. 16. Muhonen MG, Piper JG, Menezes AH. Pathogenesis and treatment of growing skull fractures. Surg Neurol 1995;43:367
72. 17. Kutlay M, Demircan N, Akin ON, Basekim C. Untreated growing cranial fractures detected in late stage. Neurosurgery 1998;43:72
6. 18. Barkovich AJ. Brain and spine injuries in infancy and childhood. In: Barkovich AJ, editor. Pediatric neuroimaging. Philadelphia, PA: Lippincot Williams & Wilkins; 2005. p. 254. 19. Azouz EM, Saigal G, Rodriguez MM, Podda A. Langerhans’ cell histiocytosis: pathology, imaging and treatment of skeletal involvement. Pediatr Radiol 2005; 35:103
15. 20. Okamoto K, Ito J, Furusawa T, Sakai K, Tokiguchi S. Imaging of calvarial eosinophil granuloma. Neuroradiology 1999;41:723
8. 21. Ortiz O, Schochet S, Bastug D. Imaging evaluation and clinicopathotolic correlation of mass lesions involving /

/

/

/

/

/

26.

/

27.

29.

30. 31.

Acta Radiol 2009 (5)

/

/

/

33.

/

/

34.

/

/

/

35. 36.

/

37.

/

/

/

/

38.

/

39.

/

/

/

/

/

/

/

32.

40.

/

/

41.

/

/

/

28.

/

/

/

/

/

/

/

/

/

25.

/

/

/

/

24.

/

/

/

/

23.

/

/

/

/

/

/

/

22.

/

/

the calvaria. Part II: tumoral and inflammatory lesions. Int J Neuroradiol 1999;5:151
65. Avrahami E, Even I. Osteoma of the inner table of the skull*CT diagnosis. Clin Radiol 2000;55:435
8. Murphey MD, Fairbairn KJ, Parman LM, Baxter KG, Parsa MB, Smith WS. Musculoskeletal angiomatous lesions: radiologic-pathologic correlation. Radiographics 1995;15:893
917. Koulouris G, Rao P. Multiple congenital cranial hemangiomas. Skeletal Radiol 2005;34:485
9. Politi M, Romeike BFM, Papanagiotou P, Nabhan A, Struffert T, Feiden W, et al. Intraosseous hemangioma of the skull with dural tail sign: radiologic features with pathologic correlation. Am J Neuroradiol 2005;26: 2045
52. DiCaprio MR, Enneking WF. Fibrous dysplasia. Pathophysiology, evaluation and treatment. J Bone Joint Surg Am 2005;87:1848
64. Lisle DA, Monsour PA, Maskiell CD. Imaging of craniofacial fibrous dysplasia. J Med Imaging Radiat Oncol 2008;52:325
32. Atlas SW, Lavi E, Goldberg HI. Extraaxial brain tumors. In: Atlas SW, editor. Magnetic resonance imaging of the brain and spine. Philadelphia, PA: Lippincot Williams & Wilkins; 2002. p. 701. Sanders WP, Chandi VV. Extra-axial tumors including pituitary and parasellar. In: Orrison WW, editor. Neuroimaging. Philadelphia, PA: Saunders; 2000. p. 613. Elder JB, Atkinson R, Zee Ch-S, Chen TC. Primary intraosseous meningioma. Neurosurg Focus 2007;23:1
9. Crawford TS, Kleinschmidt-Masters BK, Lillehei HO. Primary intraosseous meningiomas. Case report. J Neurosurg 1995;83:912
5. Daffner RH, Yakulis R, Maroon JC. Intraosseous meningioma. Skeletal Radiol 1998;27:108
11. Aguawal V, Ludwig N, Aguawal A, Bulsara KR. Intraosseous intracranial meningioma. Am J Neuroradiol 2007;28:314
5. Stark AM, Eichmann T, Mehdorn HM. Skull metastases: clinical features, differential diagnosis, and review of the literature. Surg Neurol 2003;60:219
26. Collins CD. Multiple myeloma. In: Husband JE, Reznek RH, editors. Imaging in oncology. London: Taylor & Francis; 2004. p. 875
89. Baur-Melnyk A, Buhmann S, Durr HR, Reiser M. Role of MRI for the diagnosis and prognosis of multiple myeloma. Eur J Radiol 2005;55:56
63. Klein MJ, Siegal GP. Osteosarcoma: anatomic and histologic variants. Am J Clin Pathol 2006;125:555
81. Murphey MD, Robbin MR, McRae GA, Flemming DJ, Temple HT, Kransdorf MJ. The many faces of osteosarcoma. Radiographics 1997;17:1205
31. Mascarenhas L, Peteiro A, Ribeiro CA, Magalhaes Z, Romao H, Magalhaes F, et al. Skull osteosarcoma: illustrated review. Acta Neurochir (Wien) 2004;146: 1235
9. Salvati M, Ciappeta P, Raco A. Osteosarcomas of the skull. Clinical remarks on 19 cases. Cancer 1993;71: 2210
6. Thananopavarn P, Smith JK, Castillo M. MRI of angiosarcoma of the calvaria. Am J Roentgenol 2003; 181:1432
3. /

/

/