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Miscellaneous lesions

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					INTRACRANIAL ARACHNOID CYST
Developmental cysts that occur in the cerebrospinal axis in relation to the arachnoid membrane First described by Brigat in 1831 Starkman et al in 1958 concluded that arachnoid cysts evolve from a developmental aberration characterized by splitting and duplication of arachnoid membrane and are truly intra- arachnoid in location

EMBRYOLOGY Minor aberrations in flow of CSF in the primordial stage of development of subarachnoid pathways resulting in sequestration of enclosed chamber of deverticulum within the premedullary mesh.

DISTRIBUTION
SYLVIAN FISSURE C.P ANGLESUPRACOLLICULAR VERMIAN AREA INTERHEMISPHERIC 50% 11% 10% 9% 5%

CEREBRAL CONVEXITY 4%
CLIVAL 3%

IMAGING NCCT SCAN Low density, smooth bordered lesion having attenuation values similar to CSF.Have well defined margins and does not enhance with contrast MRI Preferred modality

Extraaxial cysts with no internal architecture. Cyst wall does not enhance with contrast and cyst content have same intensity as CSF on all imaging

Proton density images used for differentiation

D/D of low attenuation lesion on CT
Hemorrhagic/non hemorrhagic cyst associated with tumour

Hyperintense to CSF with perilesional edema
Ependymal cysts Dermoid or epidermoid cyst - isointense or slightly hyperintense to CSF on proton density images Cystic astrocytoma Lipoma - Hypointense to CSF on T2

Diffusion weighted sequences may further help to differentiate.

CLINICAL ASPECTS
SYLVIAN FISSURE Most common site for intracranial arachnoid cyst Peak age- infants, adolescents Boys seven times more affected than girls Left hemisphere twice as commonly affected as right

Headache most common symptom
Seizure next common symptom Focal bulge in temporal region

Mild exophthalmos - forward protrusion of greater with of sphenoid
Papilloedema,Contralateral papilloedema

CLASSIFICATION BY GALASSI et al
TYPE - I Cyst involves proximal most part of sylvian fissure

No mass effect
No expansion of middle cranial fossa Free communication between cyst and subarachnoid space

TYPE - II
Proximal and intermediate portion of sylvian fissure Mild expansion of middle cranial fossa

Mild mass effect
Partial communication of cyst with subarachnoid space

TYPE III Involves entire sylvian fissure Prominent expansion of middle cranial fossa Severe mass effect No communication between cyst and subarachnoid space MANAGEMENT Adults with asymptomatic cyst - conservative All arachnoid cyst that causes a mass effect or neurological symptoms should be operated FENESTRATION , CYST PERITONEAL SHUNT

SELLA TURCICA
SUPRASELLAR
INTRASELLAR SUPRASELLAR Occurs in children Boys twice than girls Three major clinical manifestation Hydrocephalus, Visual impairment, Endocrine dysfunction Gait ataxia common manifestation Bobble head doll syndrome CT - Head of bunny appearance Management - Endoscopic ventriculocystostomy

INTRASELLAR Never observed in infancy; mean age - 42yrs Extradural Not associated with subarachnoid cistern Pinhole communication present Cardinal manifestation is headache Endocrinopathy - Hypothyroidism, Adrenal hypofunction Decreased visual acuity, Bitemporal hemianopia Management - Transsphenoidal cyst decompression

INTERHEMISPHERIC FISSURE
Uncommon site Associated with partial/complete agenesis of corpus callosum Two types Interhemispheric - Usually associated with corpus callosum agenesis. Occurs in midline,extends equally on either sides Batwing appearance of lateral horns Parasaggital cysts- Not associated with corpus callosum agenesis

Unilateral
Limited by falx, wedge shaped

CEREBRAL CONVEXITY
INFANTS- Progressive enlargement of head ADULTS- Focal/ Grand mal seizures, Headache.Papilloedema, contralateral hemiparesis.

QUADRIGEMINAL CISTERN
Behave like pineal masses Most common presenting symptom is obstructive hydrocephalus Children - Increased head size AdultsRaised intracranial pressure

CLIVAL REGION
Most uncommon site Clinical feature - Weakness/ Spasticity of limbs Obstructive ventriculomegaly Cranial nerve paresis Symptoms may show fluctuation

CP ANGLE
Mimic closely aoustic schwannoma

POSTERIOR FOSSA
•Midline near IV th ventricle or cisterna magna •Paramedian area opposite cerebellar hemisphere

Clinical feature of midline lesion -

Obstructive hydrocephalus
Raised ICP Subtle focal signs of vermis

MIDLINE DIFFERENTIAL DIAGNOSIS
MEGA CISTERNA MAGNA DANDY WALKER SYNDROME EPIDERMOID CYST CYSTIC ASTROCYTOMA, HEMANGIOBLATOMA

VENTRICLE
PRIMARY - Arises in lateral or IVth ventricle, rare SECONDARY - Originate extraaxially and extend into intraventricular system ( suprasellar arachnoid cyst )

Lateral ventricular cyst are treated by endoscopic fenestration IVth ventricle treated by excision through midline vermian approach.

Dermoid and Epidermoid Tumours

• Represent nests of cutaneous tissues misplaced during embryogenesis and are found along lines of ontogenic neurocutaneous differentiation. • Rare, benign,slow growing tumours. • Epidermoids - 0.5-1.5% of brain tumors • Dermoids - 0.3% of brain tumours • Epidermoid often become symptomatic in 20-40 yrs of age and can be lateral in location • Dermoid most commonly diagnosed in pediatric age group , occur in midline.

Histology
• Gross- Smooth,glistening pearly wall • Epidermoid - Cyst lining is composed of a capsule of stratified squamous epithelium. • Dermoid - Cyst lining contains in addition to epithelium, dermal elements as hair and sebaceous glands.

Pathogenesis
• Congenital
– Originate along the „posterior closure line‟ of the neuraxis and of the vertebral canal from displaced cellular elements with cutaneous commitments. – Heterogenous cutaneous cell rest in the cranium.

• Iatrogenic

Imaging
• Scalp - Soft tissue masses that may erode the outer table of skull, Intracranial extension may be seen. • Skull- appear as lucent defects within the bone . Almost always have sclerotic borders. They may expand the diploic space and can extend intracranially. Calcification may be seen.

• D/D
– Leptomeningeal cyst: erode inner table, skull fractures – Hemangioma: Spoke like trabeculations – Eosinophilic granuloma:Well defined borders but edges rarely sclerotic – Metastases: Ill defined margins, Lack sclerotic borders – Osteomyelitis : Periosteal reaction or sequestrum – Paget‟s Disease: Lack sclerotic margin

Imaging contd
• Intracranial lesions • Epidermoid:
– NCCT: homogenous, isodense to CSF – CECT: Rim enhancement or peripheral calcification. Takes the shape of the location, rarely cause hydrocephalus, edema is unusual.

– MRI:
• T1- Isointense to CSF,hypointense to brain. • T2- Heterogenous signal hyperintense to brain and slightly hyperintense to CSF • Contrast - Rim enhancement • Proton density- Heterogenous cyst content hyperintense to CSF and brain parenchyma. • Diffusion- diffusion coefficient similar to brain parenchyma ( arachnoid cyst - hypointense ) • T2 with steady state free procession imaging (SSPF)- epidermoids show hypointensity, arachnoid cyst remain hyperintense.

• Dermoid
– CT:Calcification and fat fluid levels more common in dermoid than epidermoid. – MRI:
• T1- Hyperintense • Rest same as epidermoids.

Differentials
• CP angle and petrous apex mass
– – – – Arachnoid cyst: no calcification. Acoustic schwannoma: enhance on contrast Meningioma : enhance Trigeminal schwannoma: enhance

• Suprasellar mass :
– Craniopharyngioma: more commonly calcified and some contrast enhancement present. – Arachnoid cyst – Pilocytic astrocytoma : contrast enhancement – Cystic pituitary tumour: contrast enhancement

• Fourth ventricular and Cerebellar tumours
– – – – Arachnoid cyst Hemangioblastomas: hyperintense to CSF Astrocytomas: hyperintense to CSF Ependymomas: Hyperintense to CSF
• Obstructive hydrocephalus and enhancing nodules more common in these tumours.

• Lateral ventricular tumours
– Choroid plexus papillomas – Meningioma – Ependymomas
• Greater attenuation than CSF and contrast enhancement

Clinical Features
• Due to :
– Location – Interference with CSF flow – Rupture into the subarachoid space or ventricular system: releases keratin and cholesterol breakdown products - may cause chemical meningitis or ventriculitis

• Scalp cyst : Painless, mobile rubbery mass • Diploe: Painless masses
– Petrous: VIIth nerve paresis – Orbit : displacement of eye

• Basal Cisterns:
– – – – Suprasellar;chiasmatic Parasellar; sylvian fissure Retrosellar; cerebellopontine angle Basilar; posterior fossa

• Suprasellar :
– Symptoms due to optic apparatus.
• Visual impairment • Optic atrophy • Bitemporal hemianopia

– Pituitary dysfunction - Diabetes insipidus

• Parasellar :
– Seizure disorder due to proximity to temporal lobe – Hemiparesis or trigeminal nerve deficits due to extension into internal capsule, thalamus and post ganglionic trigeminal nerve

• Retrosellar :
– Trigeminal neuralgia: due to tendency to envelop adjacent neural structures the symptoms are irritative as compared to compressive in nature – Multiple cranial nerve deficits: V, VII,VIII – Cerebellar ataxia,Nystagmus, Hemiparesis

• Basilar :
– Lower cranial nerve involvement – cerebellar deficits – Pyramidal tract abnormalities

• Intraventricular - variety of symptoms
– Obstructive hydrocephalus – Waxing and waning of varied symptoms as in demyelinating disease: headache, dementia, Psyhiatric problems, local compressive events,cranial nerve, ataxia,hemiparesis.

Management
• Surgical excision - Treatment of choice
• Complications :
– Damage to nerves, blood vessels, brain or cord – Aseptic meningitis - 40% of cases – Postoperative hydrocephalus

CNS XANTHOMA

Introduction
• • • • Rare disease Benign Space Occupying lesion Little symptomatology Xanthomatous tumors of the central nervous system are occasionally associated with diseases such as Hand-Schuler-Christian disease, malignant fibrous histiocytoma, hyperlipidemia, and a complication of metabolic or storage disorders.

Pathogenesis
• Xanthomas means yellow tumour (misnomer as they are often white) • It is a mass predominantly consisting of macrophages containing small lipid droplets also known as foam cells (Histiocytes of foamy appearance containing triglycerides and cholesterol). • Also known as cholestomata because of high cholesterol content.

Pathogenesis
• Association of xanthoma and hypercholesterolemia was first suggested by Quinquaud(1878) • Two types:
– Primary Xanthoma- True neoplasm of skin and other organs – Secondary Xanthomas- Jaundice or Diabetes leading to infiltration caused by changes in plasma cholesterol levels

Formation of Xanthoma
• Factors playing role in the formation : Infection Trauma Cellular Vascular permeability • Some tissues as granulation tissue and hemangiomata have increased tendency for xanthoma formation

• Xanthoma formation is determined by plasma lipids and lipoprotein abnormalities in which non polar lipid moeitis form unstable emulsions. Large number of droplets are pinocytosed by cells of reticulo endothelial system which are transformed into xanthoma cells

CNS Xanthogranuloma
• Xanthogranuloma is a disorder of histiocytes characterized by solitary of multiple yellow - red nodules on skin • Predominantly a disease of infancy or childhood • Various organs can be affected • CNS is occasionally involved in systemic xanthogranulomatosis

• Isolated lesions limited to the intracranial compartment commonly appears in the ventricular system ( intraventricular type).These lesions arise from choroid plexus and sometimes cause signs of raised ICP due to obstructive hydrocephalus. • Solitary nonsystemic xanthogranuloma located in another intracranial location is extremely rare.

• Only six-seven cases have been reported including xanthogranuloma in middle fossa, sellar region ,CP angle, Meckle‟s cave, intraparenchymal temporal lobes, and Cavernous Sinus. • Origin seems to be in the adventitial cells of blood vessels where a perivascular histiocytic focus grows and later becomes a granulomatous mass.

• Xanthogranuloma is essentially a benign , self healing disorder. • Represents an accumulation of histiocytes that lack birbeck granules • Currently categorized as histiocytosis class II which is defines as histiocytosis of mononuclear phagocytes other than langerhans cells.

• Whereas they are classified as normolipidemic histiocytosis, association with familial hyperlipoprotemia II a is reported • Further divided into two categories: AXG JXG • AXG- giant cells are more pronounced • JXG - Lack giant cells and have lower inflammatory cell infiltration

• Divided into three broad categories on the basis of there primary location: • Choroid plexus • Dura • Brain or spinal cord parenchyma

Suprasellar Xanthogranuloma
• D/D of craniopharyngiomas • Xanthogranulomatous change in craniopharyngioma is well known • However xanthogranuloma of sellar region is clinically and pathologically distinct • Adolescents and young adults, predominant intrasellar, small tumour size, longer preoperative history, lower frequency of calcification and visual symptoms,better resectability and favourable outcome

Lesions associated with Xanthomatous changes
• Choroid plexus : Highly vascular tissue active in filtration therefore has increased tendency for xanthomatous changes. • Found in 1-2% of brain autopsies • Incidence -30% in 3rd decade and 70% in 7th decade. • Multiple, vary in size. • Most common in occipital horns of lateral ventricles

• Can have hemorrhage and necrosis - calco siderotic nodules ( gamma gandi bodies)

• The hypothalamic dysfunction caused by a massive hematoma in the lesion of the third ventricle may cause sudden deterioration and death, whether the obstructive hydrocephalus exists. The risk of hemorrhage and hydrocephalus still remains after aspiration alone because of the presence of the cyst wall. Radical extirpation should be the choice of treatment for xanthogranulomas of the third ventricle.

• Xanthomatous changes can occur in Meningioma ( Angioblastic type) and Neurinoma ( Antoni Type B) • Hypercholesterolemia: Mostly xanthomatous process involves areas outside the blood brain barrier eg. Hypothalamus or if BBB is damaged.

• Xanthomatous changes in HistiocytosisX : Also Known as Hand Schuller Christian syndrome. Xanthomatous canges occur in nervous tissues. Lesions found mainly in cranial dura and basal ganglia • Xanthoma in Systemic Reticulosis: Hodgkin‟s disease and Multiple Myeloma. Meninges are involved most commonly.

Xanthoma Disseminatum
• • • • Rare dermatologic disorder. First described by Von Graefe. Also known as Xanthelasma Multiplex Histiocytic disorder of non langerhans cell origin characterized by xanthomatus deposits affecting skin and mucosa in absence of hyperlipidemia • CNS involvement is usually extraaxial • Chiari first reported intraparenchymal CNS disease.

• Most common initial presentation of CNS involvement is Diabetes Insipidus due to involvement of sella turcica and infundibulum. • Prognosis is good. Spontaneous remission occurs occasionally. Progressive course particularly true of CNS disease causing morbidity and mortality.

Cerebro Tendinous Xanthomatosis
• Cerebrotendinous xanthomatosis (CTX) is a rare inherited disorder due to a systemic defective activity of the mitochondrial enzyme sterol 27-hydroxylase.
• This enzyme plays an important role in the metabolic pathway of cholesterol by catalysing the oxidation of sterol intermediates.

• Consequently, patients with sterol 27hydroxylase deficiency have defective bile acid synthesis (with increases in cholic acid and decreases in chenodeoxycholic acid) and abnormally high levels of cholestanol in plasma, urine, faeces and various tissues. • The abnormal metabolism of cholestanol is considered responsible for the clinical manifestations of CTX.

Clinical features
• Clinical symptoms may be evident in different organ systems but are usually dominated by the classical triad of the disease: juvenile cataracts, tendon xanthomas and progressive neurological impairment

• The onset of symptoms and signs in patients with CTX usually occurs in childhood, with a combination of bilateral cataracts and diarrhea followed by the development of neurologic abnormalities and tendon xanthomas. Neurologic symptoms and signs include cerebellar and pyramidal dysfunction, dementia, epilepsy, and polyneuropathy.

• Additional symptoms are premature atherosclerosis and osteoporosis.
• The main disease process in patients with CTX is found in select areas within the central nervous system. • At macroscopic examination, atrophy is often found, especially in the cerebellum. At light microscopy, the most severe lesions are found in the dentate nucleus and adjacent white matter. In addition, there are often lesions in the basal ganglia, internal capsule, brain stem, and spinal cord.

• Tendon Xanthomas seldom develop before the age of 20 but more typically start to develop in the 4th decade of life, frequently in the Achilles tendons, either symmetrically or asymmetrically (7). Additional xanthomas can be found at the extensor surface of the metacarpophalangeal and interphalangeal joints, olecranon, and knees.

• Other conditions in which tendon xanthomas can be found are familial hypercholesterolemia and cholestatic liver diseases . However, in patients with these conditions, other types of xanthomas beside tendon xanthomas can occur, such as those in the skin and the palm of the hand (eg, eruptive xanthomas) and periorbital xanthomas (xanthelasmata)

• The diagnosis of CTX can be made biochemically [detected by the increased serum level of cholestanol] and genetically [detected by molecular defects in the sterol 27-hydroxylase gene].

Radiology
• MRI- Abnormalities in the dentate nuclei can be revealed by FLAIR sequences with great sensitivity. • Bilateral hyperintensity of the dentate nuclei (79%) and surrounding white matter can be considered a neuradiological feature suggestive of CTX.

• Globus pallidus, substantia nigra,inferior olive and adjacent white matter are also involved as disease progresses.

Pathological correlation
• In these locations, lipid crystal clefts and perivascular macrophages, neuronal loss, demyelination, fibrosis, and reactive astrocytosis were found at microscopic examination.

Radiology
• The decrease in NAA and increase in Lactate seen by MRS in the brains of patients with CTX indicate the presence of widespread axonal damage and mitochondrial dysfunction.
• MRS could be useful in longitudinal studies monitoring response to therapy in CTX patients.

• Spinal cord MR imaging revealed increased signal intensity in the lateral and dorsal columns on T2-weighted images. Achilles tendon xanthomas displayed intermediate signal intensity on T1- and T2-weighted images.

Treatment
• Early diagnosis is imperative in patients with CTX, as the pharmacological treatment with chenodeoxycholic acid (or with a combination of chenodeoxycholic acid and HMG-CoA reductase inhibitors) has been shown to slow or even reverse the progression of the disease.

Histiocytosis

Introduction
• Three clinical entities considered as subtypes :
– Hand Schuller- Christian disease(1893): triad of calvarial defects, exophthalmos and diabetes mellitus. – Letterer- Siwe disease (1924): fulminant proleferative disease of infancy – Eosinophilic granuloma (1940) : solitary osteolytic lesion of bone.

• Lichenstein introduced the term Histiocytosis X in 1953.

Langerhan’s cell
• Involves the proliferation of a clone of Langerhans cells. • Langerhans cell is a distinct member of mononuclear phagocytic system that includes tissue histiocytes and macrophages. • Derived from bone marrow and is found normally at skin, buccal lining and lymph nodes.

• Functions as antigen presenting cell to lymphocytes. • Expresses CD1 and CD4 surface antigens, • High ATPase activity. • Has affinity for peanut agglutinin. • Contains high cytoplasmic content of S-100 protein • Possesses a characteristic cytoplasmic membranous structure known as the Birbeck or Langerhans cell granule.

Histopathology of Langerhans Cell Histiocytosis
• Polymorphous cellular infiltrate • High cytoplasmic content of S-100 detected by immunoperoxidases. • Electron microscopy: Langerhans cell nuclei have characteristic shape- contorted and deeply indented contour • Cytoplasm contains birbeck granules- rod shaped.

Establishing a diagnosis
• Three tier system:
– Presumptive diagnosis: typical light microscopy findings – Diagnosis: S-100 immunolocalization, cytoplasmic ATPase demonstration, peanut agglutinin studies, CD 4 surface markers – Definintive diagnosis : CD 1 surface markers, documentation of birbeck granules.

Involvement of CNS
• Mildest form of Langerhans cell histiocytosis is a single osteolytic lesion of bone known as eosinophilic granuloma. • Can occur in almost any bone but preferred sites are the calvaria, the vertebral bodies, the ribs and long bones of the limbs.

• Hand Schuller Christian triad - chronic progressive form, remitting and relapsing course, may be associated with cutaneous and pulmonary lesions. • Letterer -Siwe disease is characterized by acutely progressive course, fever, pancytopenia, hepatomegaly, diffuse pulmonary infiltrates and cutaneous eruptions

Types of LCH
• Monostotic eosinophilic granuloma: most common form. • Occurs predominantly in children; 75% occur before 20 yrs of age. • Common sites of involvement - skull, rib, femur,jaw,humerus and vertebral body. • Slight male dominance, rarely progresses to disseminated form.

Polyostotic eosinophilic granuloma
• Similar age group, • Slightly worse prognosis • Greater prediliction for the skull; multiple skull lesions are often discovered.

Disseminated LCH
• Most frequently involved sites are: Bone>Skin>Liver> Spleen>Lymph nodes> Bone marrow > Lungs. • Can be acute or chronic • Occurs in infants and young children; 30% of cases occuring below 2yrs of age.

Unifocal Extraskeletal LCH
• Uncommon • Many sites - lung, skin • CNS- Hypothalamus also k/a Gagel‟s granuloma and Ayala‟s disease.

Clinical Features
• Monostotic - Local tenderness or small mass lesion, pathological fracture of long bone, vertebral fracture -back ache. • Polyostotic- pain or mass lesions of scalp or local effects at base of skull as Diabetes insipidus, proptosis recurrent otitis media

• Disseminated:
– Indolent : multiple skin macules and papules with osteolytic bone lesions, reticulonodular pulmonary infiltrates or hepatomegaly. – Aggressive : Fever, pancytopenia, lymphadenopathy, hepatosplenomegaly.

• Isolated cerebral form- mass lesion and localizing symptoms

Radiologic features
• X- ray: “Punched out lesion”- Osteolytic with complete absence of bony trabeculae and without a sclerotic rim. • D/D : Metastatic carcinoma, metastatic neuroblastoma and primary Ewing‟s sarcoma • CT - Intracerebral : Low density lesion with moderate enhancement.Beveled edges. • MRI : Prolonged T1 and T2 values with

Differentials
• Congenital : Dermoid, Intradiploic arachnoid cysts, NF I • Acquired :
– Hemangiomas- solitary, well circumscribed margins with spoked wheel or reticulated pattern. – Epidermoids: Involve both outer and inner tables, well defined, lack central trabeculae , have sclerotic margins. – Lytic phase of Paget‟s disease

• Primary calvarial neoplasms
– Plasmacytomas – Sarcomas

• Metastases: Reactive sclerosis is absent
– Lung, breast

Management
• Solitary eosinophilic granuloma/ monostotic disease :
– May resolve spontaneously – curettage, resection or intralesional injection of methylprednisolone. – Radiation : For patients with clear progression, lesions at critical areas as vertebrae, symptomatic lesion. 450-1000 rads in 200rads daily fraction

• Polyostotic disease:
– Adult with single symptomatic lesion - surgery + radiotherapy. – Chiildren - chemotherapy as they have higher risk of developing a disseminated process.

• Disseminated : Chemotherapy chlorambucil, vincristine, vinblastine, cyclophosphamide, methotrexate with or without prednisolone. ( 30-65% response). Interferon, etoposide , bone marrow transplantation - newer options

• Unifocal lesion of brain or spinal cord surgical resection with subsequent radiotherapy or chemotherapy.

Prognosis
• • • • Age < 2 years Pulmonary involvement Hepatic involvement Bone marrow dysfuction

• Lahey‟s score: 8 features ,1 point for each
– – – – – – – – Skin involvement hepatic dysfunction Splenomegaly Respiratory symptoms Bone involvement Pituitary involvement Anemia/ leokopenia/ thrombocytopenia Purpura

• Score -7,8 - 2 year mortalily approaches 100%.

• Good risk : > 2 yrs without organ damage . 5 year survival -90% • Intermediate : < 2 yrs without organ damage. 5 year survival -66% • Poor risk : Organ damage regardless of age. 5 year survival 47%

Aneurysmal Bone Cyst

Introduction
• The aneurysmal bone cyst (ABC) is an expansile cystic lesion • Affects persons during their second decade of life.

• The ABC may occur in any bone in the body.
• Although benign, the ABC can be locally aggressive and cause extensive weakening of the bony structure and impinge on surrounding tissues

• In 1942, Jaffe and Lichtenstein first described ABC as a distinct entity when they discovered "a peculiar bloodcontaining cyst of large size

Definition
• World Health Organization, the ABC is a benign tumorlike lesion. It is described as "an expanding osteolytic lesion consisting of blood-filled spaces of variable size separated by connective tissue septa containing trabeculae or osteoid tissue and osteoclast giant cells."

Incidence
• Rare, accounting for only 1-6% of all primary bony tumors. • A group from Austria reported an annual incidence of 0.14 ABCs per 100,000 people.

• Slightly increased incidence in women.
• 50-70%, occur in the second decade of life, with 70-86% occurring in patients younger than 20 years. • The mean patient age at onset is 13-17.7 years.

• 6% of tumours of bone • Rarely found in skull- 6% • Less than 100 cases involving the skull have been reported in the literature, most of them localised in the cranial vault.
• Frontal, Occipital and temporal bone

ETIOLOGY
• Reaction secondary to another bony lesionSecondary ABCs This theory has been proposed because of the high incidence of accompanying tumors in 23-32% of ABCs. Giant cell tumors are most commonly present. • ABCs may arise de novo - primary ABCs.
• ABCs may arise in an area of prior trauma.

Pathophysiology
• The true pathophysiology is unknown
• The vascular lesions cause increased pressure, expansion, erosion, and resorption of surrounding bone. The malformation is also believed to cause local hemorrhage that initiates the formation of reactive osteolytic tissue.

Clinical
• Pain, a mass, swelling, a pathologic fracture, or a combination of these symptoms in the affected area. • Symptoms are usually present for several weeks to months before the diagnosis is made. • The mass may also have a history of rapid enlargement.

Location
• ABCs most commonly affect long tubular bones, followed by the spine and flat bones. • 80% of all ABCs. • When present in long tubular bones, ABCs tend to be eccentrically located in the metaphysis • Least commonly, the ABC is in a subperiosteal location where it may form a predominant soft tissue mass.

• In a published review of 897 cases of ABC, the following rates of occurrence were reported:
 Tibia - 17.5%
 Femur - 15.9%  Vertebra - 11.2%  Pelvis - 11.6%  Humerus - 9.1%  Fibula - 7.3%  Foot - 6.3%

Distribution of lesion

 Hand - 4.7%
 Ulna - 3.8%  Radius - 3.1%  Other - 9.2%

Co existence
• • • • • • Chondroblastoma Giant cell tumour Osteocarcinoma fibroma Hemangioma Fibrous dysplasia

Imaging
• Aneurysmal bone cysts are well-demarcated lesions that arise from the diploe and expand both the inner and outer tables of the skull.
• On CT scanning they are multiloculated expansile bone lesions with characteristic fluid levels.

• T1- low-to-intermediate signal intensity with or without fluid levels. Acute hemorrhage into the cyst may have high signal intensity.

MRI

• T2-low-to-intermediate signal intensity or some areas of heterogeneous high signal intensity, depending on the contents of the cyst. A rim of low signal intensity with internal septa may produce a multicystic appearance.

• MRI images of aggressive lesions show tumor enhancement with gadolinium enhancement, especially when they are associated with other tumors.

Stages
 Initial or incipient
 Small and usually eccentric lesion  No gross expansion

 Little erosion or saucerlike appearance of the cortex

• Growth
 Rapid destructive growth pattern  Massive bone lysis and cortical destruction

 Growth so rapid that periosteal bone cannot keep up
 Little or no bony circumscription

 Blown-out appearance

• Stable
 Classic ABC appearance  Expanded and distorted bone with distinct bony shell  Bony shell surrounds numerous internal trabeculations

• Healing
 Progressive ossification of trabeculae  Forms irregular and coarse trabeculated mass

Staging by Enneking
• Latent or inactive
 Asymptomatic  Usually incidental finding

 May grow slowly, but almost always reaches a steady state where it no longer grows

• Active
 Mildly symptomatic  Discovered because of discomfort or pathologic fracture or mechanical dysfunction  Grow steadily, continues to enlarge during observation

• Aggressive
 Despite being benign, may act more like a lowgrade malignancy  Often symptomatic  Discovered because of discomfort, a growing mass, pathologic fracture  If palpable, often are larger and tender; may feel rapid enlargement on serial examinations; may feel more fixed  Little contact inhibition

 Penetrate or permeate the natural barriers to tumor growth, which are cortical bone, fascial septae, articular cartilage and dura

Treatment
• Medical therapy:
– Selective arterial embolization
 Certain diagnosis of ABC

 Technical feasibility and safety
 Stability, no evidence of pathologic fracture or impeding fracture  No neurologic involvement

• Intralesional injection:
– surgical access is difficult – other modalities are contraindicated.

• Calcitonin and methylprednisolone

Surgical
• Curettage • Subtotal resection • En block resection

Recurrence
• • • • Can be upto 50% recurrence rate 50%- subtotal resection 20-30% - curettage Enblock resection involving the calvaria curative

Radiation
• For local control • Recurrent or unresectable lesion

Differential Diagnosis
• Common - Primary Brain tumours( GBM) Metastatic Brain tumours Abscess Granuloma- Tubercular NCC Resolving hematoma Infarct

Differentials
• Less common Thrombosed vascular malformations Demyelinating disease( M S) • Uncommon Thrombosed aneurysm Other primary brain tumours( Primary CNS lymphoma in AIDS) Radiation Necrosis

Glioblastoma Multiforme
• • • • Most common of all primary CNS tumours Age - 50 yrs Location - Deep cerebral white matter NCCT - Marked tumour heterogenesity Central low density - Necrosis Hemorrhages of different ages • CECT and MRI - Inhomogenous enhancement, Thick irregular rim

• Most common CNS neoplasm • M.C primary sites - Lung >breast> Malignant melanoma> GI and genitourinary • Location - Corticomedullary junction • NCCT - Iso/ Hyperdense lesion • CECT- Strong solid/ ring enhancement • MRI T1- Hypointense to brain except melanoma ( hyperintense) T2 - Hyperintense, Multifocal Post Contrast- Enhance strongly Smooth walled, homogenous ring

Metastasis

Pyogenic Abscess
• • • • • Hematogenous spread Direct spread - sinus and mastoids Location - Corticomedullary junction History of fever, ear discharge Four stages - Early cerebritis(3-5 days) Late cerebritis(4-5 days) Early capsule ( 2weeks) Late capsule (weeks/months)

CT
• Cerebritis - Normal or poorly marginated subcortical hypodense lesion • Capsular stage- Thin, well delineated capsule, enhances strongly,uniformly and continuously . Moderate vasogenic edema In contrast to tumour- Rim is typically thickest near the cortex. • Late capsular stage - Size shrink,edema subsides but rim enhancement persist for months after clinical resolution.

MRI Brain
• Cerebritis - Ill defined,subcortical lesion hyperintense on T2. • Capsular - Well defined thin walled capsule. T1- Iso/hyper intense ring T2 - Ring becomes hypointense Post contrast - Homogenous rim enhancement

CNS Tuberculosis
• • • • Tubercular menigitis Tuberculoma Result from hematogenous spread Sites - Cerebral hemispheres(Adults) Cerebellum ( Children) Cortical and subcortical lesions are typical. • Usually solitary, Multiple lesions in 10-35%

Tuberculoma
• CT- Mature tuberculomas are well delineated round or oval, ring enhancing leison
• MRI T1 - Isointense T2- Central hyperintense region with hypointense rim Contrast- Marked enhancement

Parasitic
• Toxoplasmosis
• Neurocysticercosis

Neurocysticercosis
• Most common CNS parasitic infection • Site- Coticomedullary junciton most common. Can be intraventricular • Four stages Vesicular Viable larva Colloidal vesicular Larva dies Granular nodular Nodular calcified • Imaging varies with stage of disease

Imaging
• Vesicular - Edema and contrast enhancement rare. • Colloidal vesicular - Edema and cyst wall ring like enhancement present • Granular nodular - edema,enhancement + • Nodular calcified - Small calcified nodule without mass effect/enhancement

CEREBRAL METASTASIS
EPIDEMIOLOGY:

25% of the patients dying of cancer have intracranial metastases.
Two -third of such patients are symptomatic during life.

PATHOGENESIS
DIRECT SPREAD- From Malignant tumours of cranial bone.

HEMATOGENOUS SPREAD- Ready access of tumour emboli to the arterial circulation of brain accounts for high incidence of metastasis from lungs and those tumours that metastasize to lungs - Tendency to invade the blood vessel and grow within it - Consistency of neoplasm - Ability to survive within various organs

DURAL METASTASES

Most common in patients with carcinoma of breast, prostrate, neuroblastoma and lymphoma.
Autopsy incidence - 9%

Most frequently involve the outer layers of dura, usually contiguous with skull lesions.
LEPTOMENINGEAL METASTASES:

Invasion of leptomeninges by hematogenous or direct
Spread throughout the subarachnoid space and ventricular system by CSF leading to neoplastic meningitis. 8% of patients dying of systemic disease Breast carcinoma,NHL, Leukemia,Ca Lung, Melanoma

BRAIN PARENCHYMAL METASTASIS
20% of patients dying of cancer. Represent growth of tumour emboli trapped at a site of acute arterial narrowing, most often at the cortical - white matter junction. 50% from solid neoplasm are single. 80% are equally divided between two cerebral hemispheres

16-18% are located in cerebellum
2-3% are found within the brainstem Carcinoma Lung is the most common site of primary-50%(small cell and adeno carcinoma) Other common primary sites are Breast, Colon,Kidney,Melanoma

Source of cerebral metastases in adults
Lung CABreast 44% 10%

Kidney - 7% GI 6%

Melanoma- 3%
Undetermined 10%

In paediatrics- Neuroblastoma, Rhabdomyosarcoma,Wilms tumour.

Metastasis from colon and kidneys tend to be single where as from breast tend to be multiple Primary Gastrointestinal tumours and pelvic tumours (Uterus,Prostate) have propensity to spread to cerebellum. Metastases are the commonest posterior fossa tumour in adults.Spread is via spinal epidural venous plexus and the vertebral veins. The interval between diagnosis of the primary tumour and brain metastases is less than 1 year in 50% of cases.

Brain metastases presenting as primary pathology are seen in upto-15% of cases.

CLINICAL FEATURE
• Due to raised intracranial pressure - Headache MC- 50% •Focal deficits- compression of brain parenchyma by mass /edema Hemiparesis/ monoparesis m.c. sign -due to compression of cranial nerve •Seizures - 15% •Mental state changes •Symptoms suggestive of TIA( Tumour TIA)Occlusion of vessels by tumour cells. Hemorrhage into tumour

Choriocarcinoma Melanoma Renal cell carcinoma

RADIOLOGICAL EVALUATION
CECT- Discreet, roughly spherical, peripherally located mass with extensive edema. Most are hypodense or isodense and 90% show enhancement on contrast.

Cystic and calcified metastases - 1-6%

MRI- Isointense on -T1

Hyperintense on -T2
Enhances strongly on contrast.

MANAGEMENT
MEDICAL ANTICONVULSANTS

STEROIDS
RADIATION THERAPY •Responsive neoplasms as Lymphoma,Germ cell,Oat cell tumours

•Moderately sensitive tumours as Carcinoma Breast, Non small cell carcinoma lung - not fit for surgery , life expectancy < 3 months
Post operative Radiotherapy : Whole Brain - especially in small cell lung carcinoma where micrometastases are common .

SURGICAL MANAGEMENT
ADVANTAGES:
• Eliminates immediate cause of cerebral edema •Rapid decompression of the brain in patients with large tumours

•Radioresistant tumours
•Establishing histopathological diagnosis.

SOLITARY LESION
Surgery indicated whenPrimary disease is quiescent

Lesion accessible
Lesion is symptomatic or life threatening Diagnosis unknown

MULTIPLE LESIONS
Usually treated with irradiation without surgery Indications of surgery : One particular accessible lesion is clearly symptomatic and/or life threatening Multiple lesions that can be assessed through single exposure

STERIOTACTIC BIOPSY
For deep seated lesions , poor surgical candidates, multiple small lesions

OUTCOME:
PROGNOSTIC FACTORS • Presence of extracranial disease, stage and treatment.

•Early onset of brain metastases following diagnosis of primary tumour.
•Neurological Grade Grade IGrade IIGrade III Minimal /no neurological deficit Karnofsky performance scale >80 Moderate deficit, KPS- 50-70 Severe neurological deficit, KPS <50

RECOMMENDATIONS
Operative treatment is the treatment of choice in all patients with single operatively accessible lesion,who do not have any other evidence of cancer or whose life expectancy is atleast 1 year. Postoperative Radiation therapyFocal external beam radiation directed at tumour bed

Interstitial radiation
To be given in patients with radiosensitive primary tumours. No added advantage in patients with radioresistant tumours as Melanoma , Colon, Renal cell carcinoma


				
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