Neuroimaging Flashcards by Emily Liu

Diffusion restricting lesions

In the brain: cytotoxic edema/excitotoxic injury
– Infarct, hypoxic-ischemic encephalopathy
– Cerebritis, herpes encephalitis, CJD, PML
– Acute demyelination, Wallerian degeneration
– Diffuse axonal injury, shaken baby syndrome
– Status epilepticus, osmotic myelinolysis

In a cavity or cyst: pus or ?protein
– Abscess: distinguish from necrotic tumor
– Epidermoid cyst: distinguish from arachnoid cyst

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MRI perfusion

MRI: Perfusion(PWI), ±contrast
– CBV: Cerebral blood volume (ml/100g)
– CBF: Cerebral blood flow (ml/min/100g)
– MTT: Mean transit time (sec)
•Acute stroke: ↑MTT ↓CBF ↓CBV
– ?Determine ischemic penumbra, “tissue at risk”
– Jury still out (DIAS, DEDAS, DEFUSE, EPITHET)
Tumor: ↑CBF ↑CBV in high-grade tumors
– Pre-operatively predict tumor grade
– Distinguish recurrent tumor v radiation necrosis

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MRI spectroscopy

Metabolites resonate at specific frequencies
• 2.0 ppm: N-Acetyl Aspartate
– “NAA”, neuronal integrity
• 3.0 ppm: Creatine + PCr
– “Cr”, energy metabolite
• 3.2 ppm: Choline + PC
– “Cho”, membrane turnover
• ~1.3 ppm: Lipid/lactate
– “Lip/lac”, necrosis
• “Tumor signature”: ↑Cho, ↓NAA
• Canavan’s disease: ↑NAA due to enzyme deficiency (aspartoacylase)

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Intra-axial brain tumors - imaging

Metastasis
Glioma
Astrocytoma, oligodendroglioma, ependymoma, CPP
Lymphoma

Abscess vs High grade Glioma
Double Rim sign w/abscess: On T2F & GRE: outer rim hypo-intense while inner rim hyper-intense (GBM both rims hypo-intense)
Homogenous enhancement (GBM heterogeneous enhancement)
Time course quicker onset of symptoms and growth rate for abscess

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Extra-axial brain tumors - imaging

Meningioma
– Hemangiopericytoma
Nerve sheath tumor
Metastasis
– Lymphoma, sarcoid
Aneurysm

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Cerebellopontine angle brain tumors

Schwannoma (75%)
Meningioma (10%)
Epidermoid (5%)

(Aneurysm)

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CPP angle - schwannoma vs meningioma vs epidermoid cyst

Internal auditory canal - IAC

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Suprasellar/sellar brain tumors

“SATCHMOE”:
– Sarcoid, suprasellar extension of adenoma
– Aneurysm, arachnoid cyst
– Teratoma/germinoma
– Craniopharyngioma, chordoma
– Hypothalamic glioma, hamartoma
– Metastatic disease, meningioma, mucocele – Optic nerve glioma
– Epidermoid/dermoid, Eosinophilic granuloma

Anterior to third ventricle

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Pineal region tumors

Germ cell tumors
- Germinoma
- Teratoma
- Choriocarcinoma
- Yolk sac tumor
- Embryonal cell cancer

Pineal origin tumors
- Pineocytoma
- Pineoblastoma

“Other” tumors
- Meningioma
- Tectal glioma
- PNET

Posterior to third ventricle

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Intramedullary spine tumors - imaging

Ependymoma
Astrocytoma
1st two comprise 90-95% of intramedullary tumors
Hemangioblastoma
Metastases

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Intradural/extramedullary spine tumors - imaging

Nerve sheath tumor
Drop metastasis
Meningioma
90-95% of intradural tumors
Myxopapillary ependymoma at conus/filum

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Drop/CSF metastases

Gliomas (esp. GBM, ependymoma)
Germ cell tumors
PNET
Lung, breast, melanoma, lymphoma, leukemia

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Extradural, extra medullary spinal cord tumors

Vertebral/discogenic origin

Metastasis
Myeloma, lymphoma, leukemia
Other vertebral tumors

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Posterior fossa tumors - children

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Posterior fossa tumors - adults

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Other intraventricular tumors

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Calcified brain tumors

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Hemorrhagic brain tumors

Hemorrhagic metastases
– Lung, breast, renal, thyroid, melanoma, choriocarcinoma
Gliomas, esp high-grades III and IV (GBM)
PNET, Rhabdoid tumor
Pituitary adenoma

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Purely cystic brain tumors

Differential diagnosis: (purely) cystic brain tumors
- Arachnoid cyst
- Epidermoid cyst
- Dermoid cyst
- Colloid cyst
- Rathke cleft cyst
- Pineal cyst
- Choroid plexus cyst

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Differential diagnosis - cystic/solid brain tumors

Metastasis (esp lung)
Glioma, esp oligo, JPA
Craniopharyngioma
Ganglion cell tumor
– ganglioglioma, gangliocytoma
Hemangioblastoma
Pleomorphic xanthoastrocytoma
Schwannoma > meningioma
Pituitary adenoma (post-radiation change)

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Differential diagnosis - T1 hyperintense brain tumors

Hemorrhagic tumors
Craniopharyngioma
Lipoma
Epidermoid cyst
Melanoma

(Vascular lesions): cavernoma, aneurysm

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Differential diagnosis: Hyperdense (CT) brain tumors

(Often, also T2- and/or ADC-hypointense)
Hemorrhagic, calcific, vascular lesions/tumors
Cellular tumors
– Lymphoma/leukemia
– Meningioma (depending on type)
– GBM, PNET, Rhabdoid, germ cell tumor

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Ependymoma - spine

Intramedullary
Multisegmental expansion, may be centrally located
May hemorrhage – look at T2/T2* weighted images

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Astrocytoma - spine

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Hemangioblastoma - spine

Pial-based “cyst/mural nodule” May be visible on angiography Association with Von-Hippel Lindau

Intramedullary metastasis

Lung, breast, renal, gastric, melanoma Lymphoma/leukemia

Aneurysm rupture

Aneurysm rupture ~85% of nontraumatic SAH, 30% also have parenchymal hemorrhage Dx: CT→ (±LP) → angiogram (or CTA?) – CT 95% sensitive to detect SAH in 12-24 hrs – ISAT compared coils/clips (Lancet. 2002: 360: 1267-74)

Perimesencephalic nonaneurysmal hemorrhage

~10% of nontraumatic SAH Localized to cisterns around midbrain, pons • ?bleeding from venous source Clinically benign course – Angiogram to exclude aneurysm, dissection – Repeat angio?/Cervical spine MRI?/neck MRA?

AVM

Intracranial hemorrhage – esp parenchymal, intraventricular, subarachnoid – High hemorrhage risk (~2-4%/yr) Arteriovenous shunting with nidus (on angio) – Enlarged arteries and veins Treatments: surgery, radiation, embolization

dAVF

Enlarged dural arteries/veins near sinus – Likely acquired, traumatic? prior thrombosis? – AV shunting but no nidus – SDH/SAH/IPH hemorrhage Sxs: tinnitus, intracranial hypertension, sz, ocular sx

Moya-moya