CENTRAL NERVOUS SYSTEM

ByDr. Nisreen Abdel Tawab

Assistant professor- Pathology

Bacterial infections

Meningitis: 1. Acute Purulent (septic) meningitis:-meningitis: inflammation of arachnoid matter and

cerebrospinal fluid (CSF).- leptomeningitis: Inflammation of arachnoid + CSF +

pia matter.- pachymeningitis: inflammation of dura matter. - meningo-encephalitis: inflammation of meninges +

brain.

Aetiology

Responsible organisms vary with the age of the patient:

-E.coli: neonates. -Haemophilus influenza: infants & children. -Neisseria meningitides: adolescents &

young adults. -Pneumococcus: very young & old.

Pathogenesis:

In the first 24 hours, purulent exudate appears on the surface of the brain.

-Usually the superficial cortex is also infiltrated by polymorphs (ie. Meningo-encephalitis).

-Involvement of CSF pathways, leading to a ventriculitis and choroid plexitis (with neonatal infection).

In the second 24 hours leptomeningeal fibroblastic proliferation start with formation of fibrous adhesions between the meninges and brain, leading to occlusion of the exit foramina of the 4th ventricle and causes hydrocephalus.

Complications

1- Arterial thrombosis →→ Cerebral infarction.

2-Thrombophlebitis →→ Pyemia. 3- Adrenal haemorrhage du to septicemia.4- Fibrosis (gliosis).

Brain tumors

Epidemiology

Incidence: 8-25/ 100.000

Primary tumors: ½: ¾ of all tumors

Metastasis : ¼ of all tumors

Etiology

Genetical predisposition Hereditary factors

Viral infections: Epstein-Barr virus

Environmental factors: pesticides, chemicals

Secondary brain tumors I - MTS

1. Carcinomas: Lung, breast, kidney and gastrointestinal tract carcinomas are the commonest.

2. Sarcomas. 3. Other malignancies include melanoma,

lymphoma, and leukemia. These tumors cells reach the brain via the

blood-stream MTS – to brain tissue, meninges, malignant

cells in CSF

Tumors of childhood

20% of all tumors – tumors of childhood

More frequently malignant than in adults

The most frequent localisation - infratentorial (brain stem, cerebellum)

Benign vs malignant?

According histological structure biopsy - (cell atypia, mitotic activity,

abnormal mitosis)

Localisation !!! Benign tumors in brain stem or deep

structures – bad prognosis

Brain tumors classificationTumor designationCell of Origin

Gliomas:-Astrocytoma -Oligodendroglioma-Ependymoma

Glial cells

-Choroid plexus papillomaChoroid plexus-Neuroblastoma -Ganglioneuroblastoma-Ganglioneuroma

Neurons

- GangliogliomaNeurons &Glial cells-Medulloblastoma -GlioblastomaEmbryonic/Primitive cells- MeningiomaMeningothelial cells

-Neurofibroma -Schwannoma-Malignant nerve sheath tumor

Nerve sheath

-HaemangioblastomaBlood vessels-Lymphoma -Craniopharyngioma-Pituitary tumors -Pineoblastoma-Metastatic tumors

Miscellaneous

Clinical feature

1. General symptoms- Intracranial hypertension syndrome

Headache, vomiting, dizziness, blurred vision Papilledema Dilatation of the pupile on the side of the lesion

- New onset of epilepsy - Altered state of consciousness

Somnolence, coma - Psychological changes (behavioral problems)2. Focal signs Depends on the localisation of tumor

Compression with benign, reversibleDestruction with malignant, irreversible

Gliomas 1. Astrocytomas - Gliomas composed of astrocytes. - The most common primary tumours of CNS. - There are 4 histological grades of malignancy. WHO types: (I, II benign)- Grade I: Pilocytic astrocytoma- Grade II: well differentiated “diffuse ” astrocytoma- Grade III: Anaplastic astrocytoma- Grade IV: Glioblastoma multiforme

Astrocytoma & Glioblastoma M

MRI T1 weighted T2 weighted flair

Age: childhood and adolescence.Site: involve midline structures: (a) The optic chiasma & hypothalamus.(b) The cerebellum.Gross picture:- well circumscribed often cystic mass with solid mural nodule.Microscopic picture:- They are consisting of elongated hair-like (pilo) cells with elongated bipolar processes and contain Rosenthal fibers, which are dense, oesinophilic fibers within cytoplasmic processes of astrocytes. - The nuclei are bland, oval to elongate.

Pilocytic Astrocytoma (WHO Grade I)

Astrocytoma

Anaplastic astrocytoma

pilocytic astrocytoma

Well differentiated “diffuse astrocytoma” (WHO Grade II):

Age: - 4th to 6th decade of life (adulthood). Site: -Commonly in cerebral hemisphere. Gross picture: -They appear as an ill –defined infiltrative growth. Microscopic features: - elongate or irregular, hyperchromatic nuclei. The

cytoplasm varies from indistinct to apparent as processes. - moderate cellularity, variable nuclear pleomorphism.

Anaplastic astrocytoma (WHO Grade III):

Age & Site: -in the cerebral hemispheres of adults. Gross picture: They appear as an infiltrative growth. Microscopic picture: Anaplastic astrocytoma has the following features, when

compared to well differentiated type: 1. More cellular. 2. Greater nuclear pleomrophism. 3. Presence of mitotic activity.

Gliobastoma multiforme

The most malignant tumor of CNS Rapid progression, death within 1 year 50 to 60 years , men more Deep part of hemispheres Grossly: well circumscribed mass with much

necrosis and haemorrhage. Microscopically: extremely pleomorphic, foci of

necrosis and glomeruloid vascular proliferation. Spreading by CSF, MTS also outside of CNS

4. Tumors of the meninges

Meningioma 15% of brain tumors mostly benign, arise from meningothelial cells of the

arachnoid. curable if adequately excised. rare malignant (meningeal sarcoma) Age: 30-60 years. More in females Site:hemisphers convexity, spinal canal. Grossly: firm, lobulated mass , indents the brain

without invading it.

Microscopic picture:

- Characteristic finding: whorls of proliferated menengiothelial cells (oval cells with pale cytoplasm and regular round nuclei).

-Some show central hyalinosis and calcification. The laminated calcified bodies, called psammoma

bodies. -The intervening stroma: richly vascularized or

fibroblastic -Types : psammomatous, fibroblastic, angioblastic,

secretory and clear cell menengioma.

Meningioma

MRI Gross

Meningioma

Histology

Peripheral nerve sheath tumours

1. Schwannoma benign, curable, adults, arising from Schwann cells of cranial (8th) and spinal

nerves. - Slow growing with tendency to adhere to adjacent

tissues; and difficulties of surgical exposure make total resection impossible.

Grossly: - firm, grayish, capsulated mass at one side of the

nerve.

Microscopic picture: - one or both of these types: - Antoni type A: the schwann cells are spindle

shaped with elongated nuclei. The cells are arranges in parallel bundles, thus nuclei show a palisade pattern (Verrocay bodies).

- Antoni type B: The cells are larger, ovoid and haphazardly arranged. The stroma shows microcystic and myxomatous changes.

Antoni A (compact) Antoni B (loose)

2. Neurofibroma

Types: - Superficial tumour: small soft pedunculated

nodules protruding from the skin. - Deep tumour; larger, resulting in diffuse tortuous

enlargement of peripheral nerves. Site: orbit,neck,back, inginal region. Grossly: - not capsulated, rubbery expansion of the affected

nerve.

Microscopic picture: - composed of fibrous tissue intermingled with

Schwann cells and nerve fibrils. - risk of transformation to malignant peripheral

nerve sheath tumours (MPNST).

Gross Microscopic

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