Lytic lesions of the skull can have many potential etiologies ranging from normal variants to neoplastic lesions. Imaging plays an important role in the evaluation and diagnosis of lytic skull lesions. CT and MRI are often used to characterize the lesions and assess bone and soft tissue involvement. The differential diagnosis depends on factors like the patient's age, lesion characteristics such as appearance, location and whether it is solitary or multiple. Common etiologies include metastases, multiple myeloma, epidermoid cysts, hemangioma and fibrous dysplasia among others. A thorough clinical history and imaging findings are needed to establish the correct diagnosis.

1. LYTIC LESIONS OF THE SKULL

2. • Lytic lesions of the skull have a wide range of different
etiologies, ranging from normal variants to congenital,
traumatic, inflammatory and neoplastic lesions, benign
ones being more frequent than primary malignancies.
• Some of them are incidental findings in imaging studies,
while many others manifest as palpable masses, with or
without associated pain.
• Their true etiology may be puzzling considering their
imaging features alone. Therefore, clinical information
including the age of the patient, main diseases and
previous physical trauma, including surgeries, is essential
for the Radiologist to narrow the differential diagnosis.

3. • Imaging approach frequently begins with
radiographic and ultrasound studies, quite
limited in most cases, CT and MR being
complementary and the methods of choice,
for the assessment of bone and associated
soft tissue masses, respectively. MR is also
able to depict bone marrow involvement,
especially helpful at early stages. Conventional
angiography may be useful for both, diagnosis
and treatment.

5. Approach
1. Detection
2. Solitary or multiple
3. Age- elderly/older adult or child/younger
adult
4. Well defined or ill defined
5. Specific characteristics

6. 1. Detection
• X ray: including skeletal survey in some cases:
evaluated as lytic or sclerotic
• CT: NECT/CECT: confirm nature of lesion (i.e.,
lytic or sclerotic), destruction in inner or outer
table, calcification, sclerotic margins, and
density
• MRI: For further characterisation of lesion.
• Bone scan

7. 2. Solitary or Multiple
Solitary common Soiitary rare Multiple common Multiple rare
Normal variant Osteoporosis
circumscripta
Normal variant Hyperparathyroidism
Surgical defect Epidermoid Surgical defect Myeloma
Trauma Cephalocele Metastasis Osteomyelitis
Dermoid Intradiploic
arachnoid cyst
Osteoporosis
Eosinophilic
granuloma
Intradiploic
meningioma
Metastasis Leptomeningeal cyst
Hemangioma

8. Older adult/ elderly
• Metastasis/malignancy- breast, lung,
melanoma, thyroid, RCC
• Multiple myeloma
• epidermoid/dermoid
• Haemangioma
• Intraosseous meningioma
• Hemangiopericytoma
• GCT
• Brown tumour
• Paget disease
• Osteomyelitis
• normal variants:
• arachnoid granulation
• venous lake
• emissary vein
• parietal thinning
• surgical defect e.g. burr-hole
Child/ young adult
• Eosinophilic granuloma/histiocytosis
• Epidermoid/dermoid
• Fibrous dysplasia
• Hemangioma
• Metastasis
• Neuroblastoma
• Medulloblastoma
• Leukemia
• Growing skull fracture
• Meningocele
• Osteomyelitis
• normal variants:
• arachnoid granulation
• venous lake
• emissary vein
• Fontanelle
• Prominent convolutional markings
• surgical defect
3. Age

9. • Metabolic

10. • In general population, seven diagnosis include
85% of all causes - by decreasing order,
dermo/epidermic cysts, hemangioma, metastasis,
multiple myeloma, Langherans histiocytosis,
Paget disease of bone and fibrous dysplasia.
• In adults, tumoral causes are predominant -
metastasis and myeloma , whereas in children,
besides congenital defects, dermoid cysts and
eosinophilic granuloma are the most frequent
diagnosis.

11. Normal Variants
• Osteolytic skull lesions may have many
different causes, anatomical variations being
responsible for up to 60% of cases.

12. Transcalvarial Venous Channels and
Venous Lakes
• Consist of apertures in the skull through which
emissary veins pass, connecting the venous sinuses of
the dura mater with veins external to the skull.
• Look like serpiginous or linear lucencies with sclerotic
borders through the skull, and are, therefore,
occasionally mistaken for sutures or fractures.
• Enlarged veins within the diploic space are known as
venous lakes, corresponding to round or oval lucent
foci, frequently along the inner table of the skull.
• These normal structures show an intense enhancement
after intravenous contrast administration on both, CT
and MR.

13. Fig: Typical transcalvarial venous channels and venous lakes appearing on
nonenhanced CT (a) as linear lucencies through the skull with sclerotic edge and
round/ oval radiolucent foci with integrity of the outer calvarial table, respectively.
These structures intensely enhance after gadolinium administration, as
demonstrated on this T1-weighted MR image (b), which also shows a large falx
meningioma.

14. Arachnoid Granulations
• also known as Pacchionian granulations.
• are normal anatomical structures visible in approximately
1% of patients corresponding to enlarged arachnoid villi
that are involved in the filtration of CSF from the
subarachnoid space to the venous system.
• Hypertrophic arachnoid granulations as a result of high
CSF pressure may be responsible for lytic skull lesions.
• Most are located close to the superior sagittal sinus.
• Appear as rounded and sharply circumscribed lucencies
with sclerotic border, seen on MR as projections within the
sinus of signal intensity similar to that of CSF and on MR
angiography as filling defects

15. Fig: Arachnoid granulation incidentally found in these non-enhanced CT
scan (a) and T2-weighted MR (b) image, as a parasagital sharply
circumscribed osteolytic lesion, remodelling inner calvarial table,
isointense to CSF, which remained stable over time.

16. Enlarged Parietal Foramina
• autosomal dominant inherited condition.
• represent a benign variant of incomplete ossification of
parietal bones, which are supposed to close during fetal
development, by the fifth month of pregnancy.
• imaging appearance consists of circular and symmetrical
openings on both sides of the sagittal suture with
variable size, up to several centimetres wide.
• Although not usually associated with any medical
problems, local pressure is painful and these patients being
at higher risk of brain damage by local trauma.
• to avoid misinterpretation as pathological entities, it should
always be reported.

17. Fig: Enlarged parietal foramina. Note the bilateral and almost
symmetric rounded parietal calvarial defect, with smooth and sharp
margins and without any associated soft tissue or vascular
malformation. The 3D reconstruction (b) provides a particularly
clear visualization of this variant.

18. • Prominent
Convolutional Markings
– Related to pulsation of
brain
– Inner table, frequent in
children
– Become prominent in
craniosynostosis, chronic
raised intracranial
pressure

19. Treatment related

20. Congenital

21. Cephalocele
• Skull defect with herniated intracranial contents.
• Meningocele CSF lined by meninges
• Gliocele CSF lined by glial tissue
• Meningoencephalocele CSF and brain
• Meningoencephalocystocele CSF, brain and
ventricles
• Atretic cephalocele Small nodule of fibrous-
fatty tissue, dura and dysplastic brain tissue.

22. • Encephaloceles, occasionally misdiagnosed as dermoid
cysts.
• protrusion of cerebral and/or meningeal tissue through a
congenital defect of the skull and dura, usually located at or
near the midline with an associated palpable mass.
• In some cases, the skin and dura overlying the
malformation is incompletely formed resulting in direct
exposure of the arachnoid layer.
• Diagnosis is usually made antenatally by means of
ultrasound, MR providing assessment of the contents of the
herniated sac and subsequent risk of infection.
• The round cranial defect with sclerotic margins may be well
demonstrated on radiographs and CT.

23. Fig: Encephalocele. T2-weighted sagittal MR images of a child presenting a
small fluctuating mass over the posterior sagittal suture since birth, clearly
depicts the herniation of the meninges and the brain tissue through a small
bone defect.

25. Sinus Pericranii
• Abnormal communication between the intracranial and
extracranial venous drainages, usually congenital.
• manifesting as a fluctuating mass in the scalp, which varies
in size according to intracranial pressure changes.
• Ultrasound evaluation provides an accurate diagnosis .
However, contrast-enhanced CT is a more popular method,
showing an enhancing epicranial mass composed of
serpiginous vessels.
• Although complication by thrombosis has been described,
treatment has basically been recommended for aesthetic
reasons.
• Preoperative endovascular embolization is a promising
technique on preventing haemorrhage.

26. Fig: Sinus pericranii. Contrast-enhanced CT
scan showed an epicranian lesion
grossly in the midline, composed of multiple
serpiginous venous structures.
Sinus pericranii. (a) Lateral X ray: diffuse & more
discrete areas of cortical thinning.

27. Fig. 8: The T1-weighted MR sagittal image (a) and the MR
angiography (b) of the same patient clearly demonstrate the
intracranial communication between the scalp venous
malformation and the superior sagittal sinus, consistent with
sinus pericranii.

28. Dermoid cyst

29. Epidermoid cyst
• 20–50 years
• Mostly in parietal and temporal
bones
• Intradiploic
• Well-defined with dense sclerotic
margins
• Typically round or lobulated
• Contains cholesterol and keratin;
d/t lipid content hypoattenuating

30. Fibrous dysplasia
• Congenital disorder expanding lesions with
mixture of fibrous tissue and woven bone
• Defect in osteoblastic differentiation and
maturation
• Monostotic (70%), polyostotic (25%),
craniofacial (CFD) and syndromic
 Plain films: blistering/bubbling cystic skull
vault lesion, commonly crosses suture,
sclerotic skull base, obliteration of the
paranasal sinuses.
 Radiolucent expansile area in diploe with
thinning of the adjacent tables, mainly outer
 margins sharply defined and can be sclerotic-
difficult to differentiate from epidermoid
 "Ground-glass" matrix in a bone lesion on CT
Bone expansion,
“Ground glass”

31. • If cystic may have thick sclerotic
"rind”
• TlWI: low SI
• T2WI: low signal (if solid) or high SI (if
"cystic")
• High SI if increase in clinical-
pathologic activity
• Tl C+: Variable enhancement
depends on lesion pattern (rim,
diffuse, or none)
• CT or MRI to define local extent
• Bone scan to search for additional
lesions & stage
lucent cavity (arrow) and a thick
sclerotic rind surrounded by a thin
lucent rim
"Ground glass" appearance on PF or CT and
homogeneously decreased signal on T2WI characteristic

32. TRAUMATIC

33. Posttraumatic defect
• Skull defects may be posttraumatic, either
surgical or as a result of high-energy trauma.
• Accurately evaluated by CT, usually require
surgical repair.

34. Fig: Posttraumatic frontal bone defect as a result of severe trauma in a
young woman CT scan (a). 3D reconstruction (b) provides an exquisite
anatomic detail of the bone defect.

35. Leptomeningeal Cyst
• A late posttraumatic complication of 1% of skull
fractures occurring under 3 years old, usually in
parietal region.
• Late complication of skull fracture with dural laceration
• Exposure of the inner table of the skull to the CSF and
arachnoid pulsations subsequent to a dural tear, result
in herniation of CSF or brain parenchyma into the
subcutaneous tissue.
• seen on both CT and MRI as a smoothly marginated
skull defect with an associated cystic lesion.
• Lucent skull lesion with rounded scalloped margin and
bevelled edges is typical.

37. Fig. 10: Leptomeningeal cyst. CT scan (a) of a 26 year-old man presenting with
seizures, showed a small defect with bevelled edges in the right parietal bone
with resultant mild deformity in the overlying scalp. MRI (b) demonstrated a
cystic lesion insinuating into the eroded inner table, corresponding to the dilated
overlying subarachnoid space.

38. • 2 different forms: growing fractures &
intradiploic arachnoid cysts
• Dural tear & herniation of CSF or brain
parenchyma into sc tissue
• Growing fracture: widening of fracture
line >4 mm; involves both inner &
outer tables
• Intradiploic arachnoid cysts: erode
inner table rather than outer table.
• Diagnosis of a leptomeningeal cyst:
history of trauma, bone defect,
presence of gliosis in neighboring
parenchyma, and the presence of
cystic lesions having a CSF
characteristic
63-year-old male; history of trauma
in childhood; erosion of inner table
of left parietal bone;
bone defect into which herniation of
brain parenchyma & CSF.

39. Others

40. Eosinophilic Granuloma
• A localized form of Langerhans cell histiocytosis.
• A systemic disease of unknown etiology, in which abnormal
proliferation of histiocytes occurs, forming focal or diffuse clusters.
• Almost exclusively affects children and young adults, who present
with a palpable mass, in the parietal area in most cases.
• characterized by a well-defined lytic lesion without marginal
sclerosis, invading the inner and outer tables, sometimes with a
central residual bone density within it, known as "button
sequestrum“.
• Its MRI signal intensity is equivalent to that of skeletal muscle, with
marked enhancement after intravenous paramagnetic contrast
medium administration

41. • X RAY:
• Best diagnostic clue:
Sharply marginated
lytic skull defect with
beveled margins, lack
of marginal sclerosis ±
Button sequestra or
sclerotic margins when
healing

42. button sequestrum:
 Lytic lesion with intact central nidus of bone
 Bone replaced by erosive accumulation of
histiocytes lucent; central opacity
represents an island of dead bone
peripheral sclerosis: not seen unless the lesion
is in the healing period; also may be seen in:
• metastatic carcinoma
• necrosis following radiotherapy
• epidermoid cysts
• calvarial tuberculosis
Classification:
• multiple organ systems, multiple sites:
Letterer-Siwe ds (10%)
• single-organ system, multiple sites: Hand-
Schuller-Christian dis (20%)
• single lesion: eosinophilic granuloma (70%)

43. Calvaria: mostly frontal,
parietal, then temporal
mastoid
• Mastoid: Geographic
destruction, often bilateral
middle ear bone deafness
• Mandible: “floating tooth”
• Greater wing of
sphenoidOrbital wall
involveproptosis

44. Fig. 11: Eosinophilic granuloma. CT scan of a 31 year-old
woman presenting with a painful swelling in the midline scalp,
revealed a sharply marginated lytic bone defect with bevelled
margins.

45. Fig: Within the bone defect depicted in the patient of figure above, there was a
soft tissue mass, which was better evaluated by means of MR, appearing
heterogeneously hyperintense on T2 (a) and gadolinium-enhancing on T1-
weighted images (b). Note the mild mass effect on the adjacent dura and gyri,
without invasion.

46. Hemangioma
• Hemangioma is the main cause of primary bone tumours at the
skull.
• Accounts for 10% of cases, middle-aged women being the most
affected.
• Sharply marginated expansile skull lesion.
• Most are single, but may be multiple in 15% of cases.
• Although frequently asymptomatic, may manifest as a palpable
mass.
• Diploic space; more often frontal & temporal.
X ray:
• Sharply marginated expansile lesion
• May have thin peripheral sclerotic rim
• Honeycomb/ sunburst/ spoke wheel/ reticulated appearance

47. • CT typically shows a well-defined lucent lesion with sclerotic
margins and a reticulated internal structure radiating from the
center to the periphery described as "sunburst" or "spoke-wheel"
pattern.
• MRI better depicts the extension of the lesion and its relationship
to the adjacent neurovascular structures.
MRI: d/o fatty or vascular nature of hemangioma
T1: low (vascular)/high (fatty)
T2: high (vascular)/intermediate (fatty)
T1C+: enhancement
• It is a strongly enhancing lesion on both, CT and MRI, after
intravenous contrast medium administration.

48. Fig. 13: Hemangioma of the skull. The slow-growing left parietal
scalp swelling of a 31 year-old woman consists of an expansile lytic
lesion on radiograph (a), well circumscribed, with sclerotic margins
and with the typical "sunburst" pattern of bony striations on non-
enhanced CT scan (b).

49. Fig. 14: MRI of the same patient as in figure above provided good
visualization of the compression of the brain by the bone lesion, which
showed heterogeneous T2 (a) hyperintensity and intense enhancement
after gadolinium administration on T1- weighted images (b). There is no
surrounding edema.

50. fig. circular radiolucent defect present primarily within the temporal bone, with minimal
extension into the frontal bone. There is an intense, radiating spiculation of bone from the
central portion of the lytic defect, creating the sunburst or spoked-wheel appearance of an
intraosseous hemangioma

51. NECT:
• excellent characterization of trabecular
& cortical detail
• Sharply marginated expansile lesion
• Thin peripheral sclerotic rim in 1/3
• Intact inner & outer table
• Outer table often more expanded than
inner table
• May deform overlying soft tissues
• "Spoke-wheel", "reticulated", or
"weblike" pattern
• Intradiploic trabecular thickening
• "Soap bubble" & "honeycomb"
appearance
CECT:
• Enhances
Fig. Surgical specimen X ray: sharply
marginated expansile hemangioma
with "soap bubble" appearance

52. Fig: Another calvarial hemangioma in young women
presenting with frontal scalp swelling

53. Hemangiopericytoma
• Intracranial hemangiopericytoma, arise in pericytes that originate
in the meninges.
• account for 1% of all central nervous system tumours.
• With a location similar to that of meningioma, usually occurs at an
earlier age, are more aggressive, tend to recur and may metastize
extracranially.
• Imaging studies demonstrate bone erosion and a narrow dural
attachment in most of these heterogeneously enhancing lesions.
• unlike meningioma, is not associated with calcifications.
• Prominent internal flow voids on T2-weighted MR images is a
typical feature.
• Preoperative embolization is recommended in order to reduce
intraoperative haemorrhage.

54. Fig: Hemangiopericytoma. Coronal bone window (a) of a 4 year-old girl
presenting with a marked focal scalp swelling in the midline of the parietal region, showed a soft
tissue mass with bone destruction without peripheral sclerosis. Note the lobulated contour, the
typical narrow base of dural attachment and the heterogeneous intense enhancement on T1-
weighted MR images after gadolinium administration, which in association with the invasion of
the skull, helped distinguish from a meningioma.

55. Fig. 18: The hypervascularization of the same hemangiopericytoma is
also evident by the numerous intratumoral flow voids on T2-weighted
MR images (a) and on the MR angiography (b).

56. Fig: The same lesion as in figures above evident on conventional angiogram by
the tumor blush, supplied by the left superficial temporal, median meningeal and
occipital arteries. Successful preoperative embolization verified on the control
angiogram (b).

57. Meningioma:
Osteolytic but usu sclerotic
margins
Predominantly after 30 yrs
age
Can result in:
 compression of adjacent
brain parenchyma
 encasement of arteries
 compression of dural
venous sinuses

58. Aneurysmal Bone Cyst
• Aneurysmal bone cysts may occur in any bone, but rarely in
the skull, accounting for only 3-6% of all cases.
• Most are benign but may be locally aggressive.
• Present as painless, progressively rapidly-growing lesion
in childhood and young adulthood
• Characteristic imaging appearance consists of an expanding
osteolytic lesion containing blood-filled spaces of variable
size, frequently with multiple small fluid-fluid levels
representing sedimentation of red blood cells.
• Total excision is the treatment of choice, preoperative
endovascular embolization significantly decreasing
intraoperative bleeding.

59. Fig. 20: Aneurysmatic bone cyst in a 54 year-old women presenting with
long-standing headache. Non-enhanced CT scan (a) demonstrated a large
destructive mass in the left parietal bone, grossly lenticular with expansion of
both, but predominantly the inner table of skull, with local mass effect. T2-
weighted MR images (b) showed hyperintensity, consistent with its cystic
nature, as well as some septations.

60. Fig.: T1 (a) hyperintensity of the same lesion . After
gadolinium administration (b) the typical peripheral
enhancement and the "soap-bubble" pattern, corresponding
to multiple cystic cavities, are evident.

61. Fig: Effective preoperative embolization of the
aneurysmatic bone cyst described above.

62. Multiple Myeloma
• A malignant bone marrow disorder characterized by
monoclonal proliferation of plasma cells.
• Responsible for most primary bone lesions in advanced
ages.
• The solitary form is designated by plasmacytoma.
• Typically appear as well-defined multiple, discrete, small,
punched out lytic lesions without marginal sclerosis
‘rain-drop’ lesions coalesce to form larger lesions lytic
lesions, resembling punch holes.
• “pepper pot skull”
• Rarely sclerotic except following therapy

63. • Enhance after intravenous
contrast media
administration, hypointense
and hyperintense,
respectively on T1 and T2-
weighted MR images.
NECT:
• Punched out lytic lesion;
cortex is eroded from within
sharply defined margins
Best imaging tool:
• Radiography (skeletal survey better than
bone scan: osteolysis without bony
reaction)
• CT > MRI for evaluation of specific
lesion extent
• MRI best for rare meningeal &
"intracranial"

65. Fig: Uncountable lytic "punched out" lesions on the lateral
skull radiograph, typical of multiple myeloma.

66. Fig: Myeloma lytic skull lesions on non-enhanced CT scan (a) of the same
patient . MRI accurately depicts myelomatous infiltration with replacement of
normal bone marrow as demonstrated in this T1-weighted images after
gadolinium administration, showing anomalous enhancement with multiple
lesions, which had a permeative pattern and T2 hyperintensity.

67. Multiple myeloma metastasis
Sclerotic margins Very rare (2%) common
Mandible involvement May be seen Rare
Soft tissue extension Advanced cases Rare
Pedicles and posterior elements are involved less frequently
and at later stage than in mets

68. Metastasis to skull:
 15-25% cancer pts
 Best diagnostic clue: Enhancing lesion(s) with
skull/meningeal destruction/infiltration
 Usu. multiple and osteolytic
 Lack sclerotic borders
 adults: lung, breast, prostate, melanoma,
follicular thyroid
 children: neuroblastomas and sarcomas
 prostate ca: usu. sclerotic or mixed type,
lateral orbital wall a favourite site
 thyroid & renal cell cancer: sclerotic and
solitary
 In the presence of a known primary tumor,
associated parenchymal metastases, and
multiple lytic lesions, calvarium metastases
be considered
 Most instances, skeletal metastases represent
advanced disease with poor prognosis.
Metastatic neuroblastoma showing
generalized moth-eaten destruction
of calvarium, producing somewhat of
a salt and pepper appearance.

69. X ray:
• Focal lytic or blastic lesions lacking "benign"
sclerotic border
CT:
• Enhancing mass centered in bone with osseous
destruction, lacking 'benign" sclerotic border
MR:
• T1WI low, T2WI high
• T1C+: Lesion may enhance to "normal" T1
marrow signal ~ Fat saturation necessary to
distinguish enhancement from normal
hyperintense marrow & scalp fat

70. Fig. 26: Skull metastasis. Multiple expansile osteolytic lesions in a patient
with long-standing rectal carcinoma. MRI features are usually similar to
those of multiple myeloma lesions, namely the T2 hyperintensity (a) and
the heterogeneous enhancement on T1-weighted images after
gadolinium administration (b).

71. Paget’s disease
Chronic, excessive bone remodeling
 Lytic Phase:
 early phase
 osteolysis, unopposed osteoclastic activity
 well-defined, often large areas of
radiolucency
 most commonly frontal and occipital
bones
 osteoporosis circumscripta
 both tables
 notable absence of peripheral sclerosis
surrounding the calvarial osteolysis
secondary to the lack of significant
osteoblastic activity.
 Mixed Phase: osteoblastic + clastic
 vast majority , active stage
 “mosaic pattern”
 Sclerotic/ blastic/ Burn-out Phase:
 dense pagetic bone
Lytic phase of Paget disease of the skull with
osteoporosis circumscripta. (a) Lateral
radiograph of a 50-year-old man shows a well-
defined area of lysis in the frontal and
occipital regions (arrowheads).

72. • X ray: Large, round, lucent area in the left parietal bone
• CT: lytic abnormality involving the left parietal bone that was well differentiated from normal-appearing
calvarial bone
• Bone scan: marked uptake in the calvaria
Osteoporosis circumscripta
87F with raised
Alkaline
phosphatase
- Kirsten M. Leu,
NEJM 2002

73. Fig. multiple lucent lesions of the skull
representing brown tumors, as well as
generalized "salt and pepper"
demineralization of the calvarium; patchy
area of sclerotic repair bone in the frontal
region.
Hyperparathyroidism:
• osteitis fibrosa cystica: classic
skeletal manifestation of advanced
hyperparathyroidism
• osteoclastic resorption of bone,
osteoblastic bone formation, and
fibrous replacement of marrow
• most common radiologic is
osteopenia,
• Subperiosteal bone resorption is
early and virtually pathognomonic
sign
• areas of decreased radiopacity are
intermingled with sclerotic
radiopaque areas classic
appearance “salt-and-pepper”
skull

74. Hyperparathyroidism with "salt and pepper" appearance of the calvarium from generalized
spotty demineralization. Multiple well-defined lytic lesions represent brown tumors

75. Leukemia with widespread lytic lesions of the calvarium
Leukemia

76. Sarcoidosis:
May be multiple or solitary
With or without bone expansion
Erosion or areas of destruction of inner and/or outer
tables
Extension intracranially or into extracranial soft tissues
Can have circumscribed and/or indistinct margins
Differential considerations :
• Hemangioma
• eosinophilic granuloma
• metastases
• other tumors as well as chronic infection

77. Osteomyelitis
•Usually complication of trauma,
sinusitis, mastoiditis
•Frontal > temporal bone
•Mixed lytic/proliferative lesion
•Moth-eaten/permeative medullary
& cortical destruction- patchy bone
destruction
•"Pott puffy tumor" = frontal soft
tissue swelling
•Often associated: Epidural abscess!
•i.e. bone destruction, soft tissue
swelling & abscess
Osteomyelitis in sickle cell disease. Several foci
of osteomyelitis, with somewhat serpiginous
radiolucent areas of destruction surrounded by
minimal sclerotic borders, are noted in the
frontal and parietal bones of this child.

78. Lipoma:
 expansile lytic lesions with well-defined margins
 may have sclerotic borders
 may show central calcification due to fatty necrosis
 Fat density in CT
 Fat SI in MR
T1 & T2: hyper
intense appearing
lipoma with both
intra and extra
cranial parts &
defect in parietal
bone

79. Discussion
• Considering such a wide range of differential
diagnosis, firstly, it might be helpful to keep the
mnemonic “HELP ME”.
• H= Hemangioma
• E = Epidermoid/dermoid
• L= Leptomeningeal cyst, Leukemia/Lymphoma
• P= Paget's disease, Postsurgical
• M= Metastases, Multiple Myeloma
• E= Eosinophilic granuloma, Encephalocele

80. • Secondly, a careful evaluation of the margins
of the lesion in conjunction with other
imaging features, such as the number and the
location, usually allows the Radiologist at least
to state whether the lesion has benign or
aggressive characteristics.

81. • Benign lesions tend to have well-defined
borders with sclerotic margins, a quite
predictable location, mostly near the midline,
and are usually solitary.
• On the other hand, those with a permeative
appearance, multiple and randomly
distributed, are probably aggressive.

82. • After having ruled out typical normal variants, the
benign versus aggressive imaging pattern should be
consistent with the specific clinical indicators, the age
of the patient being the first one to be taken into
account.
• For instance, in adults and elderly patients, metastases
are by far responsible for the majority of lytic skull
lesions.
• children and young adults present more frequently one
of the congenital, inflammatory, traumatic or benign
neoplastic conditions mentioned above.

84. QUESTIONS….
• Approach to lytic lesions in skull
• Name few solitary & multiple lytic lesions
• Name few lytic lesions considering different age groups
• Imaging findings of dermoid cyst
• Imaging findings of fibrous dysplasia
• Imaging findings in calvarial osteomyelitis.
• Imaging findings in Multiple myeloma
• Suggestive features to differentiate multiple myeloma vs metastasis
• Importance of involvement of mastoid, mandible & sphenoid by LCH
• Common primaries of calvarial metastasis & importance of fat saturation
in MR
• Meningioma vs hemangiopericytoma.
• Imaging findings in different phases of Pagets disease
• Normal variants of skull which present as lytic lesion
• Name bony defects that present as lytic lesion