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Central Nervous System (Brain Tumors (Routine Imaging (Ventricular tumors,…
Central Nervous System
Brain Tumors
- primary brain tumor is the most common benign tumor of children.
- In adults the commonest tumors are gliomas, metastases and meningiomas. Most of these lie in the supratentorial compartment, which comprises the anterior and middle fossa.
- In children, medulloblatomas and cerebellar astrocytomas predominate, which lie in the posterior fossa.
Tools
- CT and MRI:
MRI is superior to CT
– No ionising radiation
– Better display of anatomical relations
– Higher sensitivity for pathology
– Easy multiplanar imaging without repositioning of the patient
– Less contrastmedia reactions and toxicity
Goals
WHO classification
- pimary and metastatic neoplasms.
- Primary neoplasms are subdivided into:
neuroepithelial tissue, peripheral nerves, meninges, Lymphomas and Hemopoetic neoplasms, Germ cell tumors, sellar region
Routine Imaging
- CT-attenuation (“density”)
- T1- , T2- and FLAIR aspect: Homogeneity, Necrosis, Edema, Hemorrhage
- Contrast enhancement
Astrocytic tumors
- divided into non- infiltrating and infiltrating
- Noninfiltrting include pilocytic astrocytomas
- infiltrating are well- differentiated, moderately-differentiated and anaplastic astrocytomas
- Brain stem gliomas have poor prognosis.
- A benign infiltrating astrocytoma is homogeneous, with minimal edema and absent contrast enhancement
- Anaplastic transformation is characterised by necrosis, edema, hemorrhage and contrast enhancement
- Differential diagnosis: low-grade glioma, ischemia, herpes encephalitis, GBM
- Most common clinical presentation: epilepsy, focal neurologic deficit, headache, vomiting, increased intracranial pressure, personality or behavior changes
Gliomas
- Glioblastoma multiforme (GBM) – grade IV astrocytoma, (malignant astrocytoma), most common of all primary intracranial neoplasms in adults. Cerebral hemispher (WM) > brainstem > cerebellum.
- GBM – CT and MRI: poorly marginated, infiltrating necrotic hemispheris mass: tumor typically crosses white matter tracts to involve contralateral hemispher by corpus callosum (butterfly glioma)
The ringenhancing lesion
Necrotic Glioma, Necrotic Metastasis, Abscess, Multiple sclerosis
Multiple lesions
Multifocal glioblastoma, Metastasis, Lymphoma, Infectious, Inflammatory
Advanced MR-Techniques
- Diffusion-Weighted Imaging (DWI) (differentiate necrotic glioma from abscess: restricted diffusion in abscess due to cellular debris and pus)
- Perfusion-Weighted Imaging (PWI) (Distinguishing of primary cerebral lymphoma from high- grade glioma)
- MR-Spectroscopy
Optic Nerve Gliomas
- found on the optic nerve and are common in neurofibromatosis.
- Typical Chiasmatic gliomas are mainly related to NF-1
Oligodendroglioma
- slowly growing tumors that usually in young adults
- They cause seizures. contain deposit of calcium (bone) and can bleed
- only surgery
Ventricular tumors
Ependymoma
- arise from the ependymal cells that line the ventricles and the center of the spinal cord.
- in children common location of intracranial ependymoma is the fourth ventricle, while in adults it is spinal.
Choroid plexus papiloma
- Radiological diagnosis is based on location, mainly lateral ventricles.
- MRI shows a thin rim of cerebral spinal fluid around the tumor and strongly enhancing lobulated intraventricular mass
- hydrcephalus is noted
Meningioma
- common in Female
- Attached to dura.
- Common sites: parasagittal (falx), sphenoid ridge, olfactory groove
- Changes in cranium (hyperostosis)
- CT, MRI – dural tail, deposit of calcium, strong enhancement, isointense in T1 and T2
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Metastasis
- Solid organ metastasis: Breast, Kidney, Lung, Prostate.
- Hematologic metastasis: Melanoma, Lymphoma
Childhood Brain Tumors
- tumor histology and location are different in adult and children.
- Meduloblastomas are the most common CNS histology in children.
- 50% of brain tumors are infratentorial.
- Common infratentorial tumors: Meduloblastomas, Cerebellar astrocytomas, Ependymomas, Brain stem gliomas, Atypical teratoid tumors
Medulloblastoma
- Origin: primitive neuroectodermal cells
- Site: vermis of cerebellum
- May cause hydrocephalus
- Subarachnoid dissemination
Intracranial Hemorrhage
- Sites and Causes:
Trauma (1. Epidural. 2. Subdural),
Vascular (and trauma) (3. Intracerebral. 4. Subarachnoid. 5. Mixed cerebral - subarachnoid)
- Risk Factors: Hypertension, Alcohol use, Smoking, Cholesterol, genetic
- Location: Putamen, Thalamus, Cerebellum, Pons, Lobar
- Lobar hemorrhages: Cerebral amyloid angiopathy
Vascular Malformations
- Cavernous angioma
- Venous angioma
- Capillary telangiectasis
- Arteriovenous malformation (AVM):
Collection of abnormal arteries and veins that lack intervening capillary bed
– Fed by enlarged arteries Arteriovenous shunting drained by prominent veins
– Easily detectable on angiogram and usually MRI
ages 20-40 common
Symptoms: Hemorrhages, seizures, progressive neuro deficits
Rx
oGamma knife oSurgical Resection oEmbolization
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Phakomatosis
- lentil mole or freckle.
- Neurologic abnormalities combined with defects of skin or retina.
- Involvement of visceral organs
Neurofibromatosis
- Dominant inheritance
- Multiple neurofibromas
- Increased incidence of: meningioma, glioma, schwannoma - bilateral VIII N.
- Cafe-au-lait (melanosis) in skin
- Elephantiasis: increased connective tissue
Edema
- important factor leading to morbidity and mortality associated with brain tumors.
- When steroid was introduced, post- operative mortality for brain tumor decreased 10 fold.
- brain edema is an increase in brain volume resulting from increased sodium and water content.
- three main types: Vasogenic, cytotoxic, hydrocephalic or interstitial
tumor-associated edema
- On CT: an area of low density, in MRI: hyperintense in T2- weighted sequence.
Hydrocephalus
- an increase in the cerebrospinal fluid, results from either Increased production (rare) or Impaired absorption (common)
- Classification:
Obstructive: obstruction within the ventricular system
Communicating: the obstruction is in the subarachnoid space or venous sinuses or there is increased CSF production as in a choroids plexus papilloma.
- The pattern of ventricular enlargement can help find the cause:
Lateral & 3rd ventricle dilatation
→ normal 4th ventricle: suggests aqueduct stenosis
→ deviated or absent 4th ventricle: suggests posterior fossa tumor
Generalized dilatation: suggests a communicating hydrocephalus.
Cerebrovascular diseases
Stroke
- Types:
Ischemic Stroke (85%): Other/Unknown (35%), Lacunar (Small Vessel) (25%), Atherosclerotic Disease(20%), Cardioembolism (20%)
Primary Hemorrhage (15%): Intracerebral, Subarachnoid
- Symptoms: Sudden onset, Hemiparesis, Hemisensory loss, Speech “impairment”, Visual change
- Early signs in CT: Dense MCA, Loss of Gray/white, Hypodense/hyperdense region
- Vascular distributions: Thalamus, Caudate head, Watersheds
- Non contrast CT is the primary imaging modality in patients with acute stroke
- Hyperdense on CT.
- Proximal hyperdense MCA sign is associated with poor prognosis, intravenous thrombolysis is ineffective
- CTA is essential for evaluating of intra- and extracranial vessels, intravascular thrombi, and thrombolytic therapy guiding
- MRI including DWI is more specific and sensitive than CT for detection of cerebral ischemia during the 1st few hours of stroke.
MULTIPLE SCLEROSIS
- High intensity lesions on T2-weighted images, observed in the periventricular region, cerebellum, brain stem, the callosal- septal interface, spinal cord
- Different types of MRI scans can reveal different types of damage (lesions) to brain tissue.
A gadolinium (Gd)-enhanced T1 MRI shows areas of inflammation in the brain.
A T2 MRI makes visible various lesions that represent the cumulative burden of disease.
A T1 hypointense MRI shows “black holes,” which represent areas of serious brain injury, such as axonal (nerve) loss.
Epilepsy
- chronic disorder which features a tendency to have seizures, a minimum of 2 seizures have occurred
- common chronic conditions in children and approximately 1% of the total population
- etiologies: Idiopathic or cryptogenic, Vascular, Congenital, Trauma, Neoplastic, Degenerative, Infection
- Electroencephalography: Primary diagnostic tool
- Neuroimaging: Anatomic (MRI, CT), Functional (PET, SPECT, MRI)
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SPINE
- Intraspinal Intramedullary Tumors:
Ependymomas 63%, Astrocytomas (grades 1-2) 24.5%, Glioblastomas 7.5% (Astrocytomas grades 3-4), Oligodendrogliomas 3.0%
- Extramedullary Tumors: meningioma
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Degenerative Spondylosis
Loss of disc height, Osteophyte formation, Facet osteoarthritis, Loss of lordosis, Spinal stenosis, Hypertrophic ligamentum flavum
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VERTEBRAL METASTASES
- requiring surgical treatment.
- Most of the metastases are located in the thoracic spine, less frequently in the lumbar , rarely in the cervical spine
- MRI is positive in the 15% of the patients with negative bone scans, whereas MRI reveals 20% more lesions in patients with positive bone scan
- The cortical involvement is necessary to have positive scintigraphy, on the contrary intratrabecular lesions are undetected by bone scans.
MRI in the screening
CT is not a screening for the use of ionizing radiations, but it is useful in evaluating lesions detected by scintigraphy, but not confirmed by x-rays standard exam. It reveals the trabecular and cortical bone lysis, the invasion of the soft paraspinal tissues, the growth ratio of the tumor identifying the sclerotic peritumoral reaction.
- osteolytic metastasis:
T1 w.i. the tumoral infiltration of the still hemopoietic bone marrow shows hypointense signal related to isointense signal of the bone, whereas in T2 w.i. has hyperintense signal, more brilliant in STIR and SPIR sequences.
contrast enhancement of the lesion is massive and marked
- osteosclerotic metastasis:
not produced by tumoral cells.
– low signal in T1 and T2 w.i.
– enhancement is heterogeneous and peripherally.
Modality Based
- CT: Cognitive decline, Decreased level of consciousness, Fish bone/other swallowed foreign body, Neck infection, Orbital infection, Rule out bleed, Seizure, Sinusitis, Stroke, Trauma, Weakness
- MRI: Cord compression, Low back pain, radiculopathy, Multiple sclerosis, Stroke.
- Rule out aneurysm = CTA, MRA
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