MRI Brain Pathology

vocabulary flashcards covering brain pathologies and related MRI appearance including neuro-oncology, vascular lesions, inner ear/orbit conditions, infectious/inflammatory diseases, and congenital brain malformations

Optic Neuritis (Devic’s Disease)

Inflammation of the optic nerve

SYMPTOMS: blurred vision, loss of vision, eye pain, photopsia (flashes of light)

MR APPEARANCE:

• Unilateral nerve swelling

• T2: hyper

• Flair: hyper

• T1 + Gad: hyper enhancing region

Optic Nerve Glioma

low-grade, slow-growing tumor of the optic nerve

common in peds

frequently associated with Neurofibromatosis type 1 (NF1).

Acoustic Neuroma (Vestibular Schwannoma)

Benign tumor on 8th cranial nerve within the vestibule

SYMPTOMS: balance issues, sensorineural hearing loss, tinnitus, facial numbness when large

more common in adults in their 30’s

MR APPEARANCE:

• T1: hypo to brain (63%), iso to brain (37%)

• T2:

  • Heterogenously hyper to brain

  • may have associated peritumoral arachnoid cysts

• T1 + GAD: intense enhancement

• SWI: some show blooming due to presence of intratumoral microhemorrhages

Cholesteatoma

Abnormal collection of skin cells deep within the ear

• benign but can cause mass-like effects

  • hearing loss, dizziness, bleeding

MR APPEARANCE:

• T1: hypo

• T2: hyper ( > CSF)

• T1+ GAD: no enhancement

  • may see thin, linear enhancement of margins

• DWI: restricted diffusion

Meniere's Disease (Endolymphatic Hydrops)

Inner ear disorder characterized by episodic bouts of vertigo, fluctuating sensorineural hearing loss, tinnitus, and ear fullness.

MR APPEARANCE:

• FLAIR + GAD: 4 or 24hr delay shows IAC enhancement

• T2 3D: eval of saccule, endolymphatic duct, choclear aqueduct

Pituitary Adenoma

Benign pituitary gland tumor

• Microadenoma:

  • 10mm or less

• Macroadenoma:

  • 10mm+

  • 2x more common than micro

MR APPEARANCE:

• T1: iso

• T2: hyper

• T1 + GAD: hypo to iso

Dynamic sequences beneficial for micro studies (mass will have delayed (90-120 sec) enhancement vs. normal pituitary tissue (60-80 sec))

Empty Sella

pituitary gland is shrunken or absent from the sella → filled with CSF

commonly correlated with idiopathic intracranial hypertension

Craniopharyngioma

Grade I tumor arising from squamous epithelium cells in the sella region

• Adamantinomatous

  • most common

  • predominantly children

• Papillary

  • predominantly adults

SYMPTOMS:

• Headache, increased ICPs, visual disturbance, hormonal issues

MR APPEARANCE:

• SOLID:

  • T1: iso - hypo to brain

  • T1 + GAD: vivid enhancement

  • T2: variable

• CYSTS:

  • T1: iso - hyper to grey matter

  • T2: variable

    • ~80% hyper

Pilocytic (juvenile) Astrocytoma

• Grade I, slow-growing brain tumor

• most common primary brain tumor in children

LOCATION: cerebellum and optic pathways

SYMPTOMS: increased ICP, hydrocephalus, headache, vision changes

MR APPEARANCE:

• T1:

  • SOLID: iso - hypo to brain

  • CYSTIC: hypo unless hemorrhagic

• T1 + GAD: vivid enhancement

  • cyst wall enhances in ~50% of cases

• T2:

  • SOLID: hyper to brain

  • CYSTIC: hyper

• T2*/GRE/SWI: signal loss if calcification or hemorrhage present

Ependymoma

Broad group of tumors that involve the lining of the ventricles

• ~10% of ped tumors

• 1/3 of tumors in kids 3 or younger

• Grade II or III (Anaplastic Ependymoma)

• Most located in posterior fossa

• poor prognosis

MR APPEARANCE:

• T1: solid parts iso to hypo to white matter

• T2: hyper to white matter

• SWI: foci of blooming from hemorrhage or calcification

• T1 + GAD: heterogenous enhancement

• DWI: solid parts may show restricted diffusion (esp. in anaplastic tumor)

Medulloblastoma

Aggressive Grade IV tumor originating in posterior fossa

• 30-40% of peds post fossa tumors

• Very fast-growing

• Obstructive hydrocephalus common

• Associated with Li-Fraumeni Syndrome

MR APPEARANCE:

• T1: hypo to grey matter

• T1 + GAD: 90% of tumors show heterogenous enhancement

• T2/FLAIR:

  • iso - hyper to grey matter

  • hetero due to calcification, necrosis, and cyst formation

  • surrounding edema common

• DWI: restricted diffusion due to hypercellularity

Chiari Malformation (Arnold Chiar)

Cerebellum and/or brainstem migration out of the cranial cavity

• Cerebellar Tonsils most inferior portion of cerebellum

• 6 Variations

  • describe different degrees of brain tissue displacement or underdevelopment at the base of the skull

  • Type 1 most comon

• Can be associated with Syrinx in cord due to increased ICP

• Best demonstrated on SAG image

Dandy-Walker Malformation

Rare congenital brain defect that affects the cerebellum and the fluid-filled spaces around it.

• Most common posterior fossa malformation

• Key features:

  • hypoplasia of the cerebellar vermis (missing/underdeveloped)

  • cystic dilatation of the fourth ventricle

  • enlarged posterior fossa (pushes brain structures upward)

  • Hydrocephalus (excess CSF → macrocephaly)

• Symptoms:

  • motor delays, balance/coordination issues, increased ICP → headache, vomiting, irritability, seizures

Meningocele

Skull or spinal defect resulting in the protrusion of the meninges filled with CSF

congenital, iatrogenic, or spontaneous.

Ischemic Stroke

rapid-onset neuro deficit from reduced/blocked blood supply to brain tissue

caused by thrombus, embolization, or systemic hypoperfusion.

2nd leading cause of death worldwide (MI is #1)

Symptoms of POSTERIOR CIRCULATION Infarct

Dizziness/vertigo, dysphagia, unilat limb weakness, ataxia, diplopia

Symptoms of ANTERIOR/MIDDLE CIRCULATION Infarct

unilateral weakness of face, arm, and/or leg, visual disturbances, dysphagia

Hemorrhagic Stroke

Bleeding directly into-

brain tissue (intracerebral) or

subarachnoid space around the brain tissue

caused by weakened vessels, aneurysms, AVMs, tumors

neurological emergency; $20\%$ of all strokes (less common than ischemic)

Symptoms of HEMORRHAGIC Stroke

sudden neuro deficits and/or decreased level or consciousness, headache, possible seizure

Stroke Risk Factors

Atherosclerosis, age, family hx, smoking, HTN, high cholesterol, diabetes

DWI for Stroke Eval

• ACUTE:

  • DWI signal - high

  • ADC appearance - low

• EARLY/LATE SUBACUTE:

  • DWI Signal

    • Early - Low

    • Late - High

  • ADC appearance - low (both)

• CHRONIC

  • DWI signal - Low

  • ADC Appearance - high

Subdural Hematoma

A/traumatic blood accumulation b/w Dura and Arachnoid space

MRI appearance depnds on acuity/stability

Subarachnoid Hemorrhage (SAH)

Bleeding inside the subarachnoid space

sudden, severe "thunderclap" headache

appearance: hyperintense on T2 FLAIR in the first 12 hours, SWI/GRE dark blood pooling post bleed

Epidural Hematoma

• Traumatic arterial bleeding between the skull and the dura (endosteal layer)

• can cause mass effect, midline shift

• Most occur in temporal*, parietal, and frontal regions

MR appearance:

• Displaced dura dark on T1/T2

• T1:

  • Acute-iso

  • chronic-hyper

• T2:

  • Acute-hypo

  • chronic-hyper

Aging Blood Mnemonic

Oxyhemoglobin

• Makes up most arterial blood (95%), venous 75%

• weakly diamagnetic form of oxygen-bound hemoglobin

• predominant in hyperacute hemorrhage (<12 hrs)

MR Appearance:

• T1- iso

• T2- hyper

Deoxyhemoglobin

• No oxygen bound to hemoglobin

• paramagnetic hemoglobin

• predominant during acute phase (1-3 Days)

MR Appearance:

• T1 iso

• T2 dark

Methemoglobin

• oxidized form of hemoglobin containing 5 unpaired electrons

• paramagnetic

MR Appearance:

• T1 Hyper during early and late subacute

Hemosiderin

• insoluble iron-storage complex

• superparamagnetic properties (10³-10⁶ unpaired electrons)

MR Appearance:

• T1- iso

• Flair- hyper

• SWI- blooming (chronic)

• DWI- hypo

Glial Cell Tumor: Diffuse Glioma

High grade glioma (III & IV)

• very poor prognosis

• Further broken into:

  • Diffuse Hemispheric Glioma

  • Pediatric type high grade Glioma

  • Diffuse Midline Glioma

MR APPEARANCE:

• T1: hypo - iso

• T2: hyper

• T1 + GAD: non-enhancing

• DWI: facilitated diffusion, some areas of restricted diffusion in higher grades

• T2*/SWI: areas of marked hypo/blooming (intralesional hemorrhage)

• DTI: disruption of white matter tracts indicates diffuse midline glioma > focal brain stem gliomas

Glial Cell Tumor: Oligodendroglioma

• Primary brain tumor originating from fat-producing oligodendrocytes

• low-grade (Grade II or III)

  • Grade II: slow growing, better prognosis

  • Grade III:

    • Anaplastic, more aggressive

• Treatment includes surgery, chemo, radiation

MRI Apperance:

• T1: typically, hypointense 

• T2: typically, hyperintense

• GRE/SWI: calcium can be seen as areas of "blooming"

• T1 C+ (Gd): heterogenous enhancement common (~50%)

  • not a reliable indicator of tumor grade

• DWI: usually no diffusion restriction

• SWI: frequently contain calcs that bloom

Glial Cell Tumor: Astrocytoma

• Primary brain tumor originating from star-shaped neuron support cells called astrocytes

• Symptoms:

  • headache, dizziness, motor disfunction, cognitive decline, vision/speech changes

• Prognosis depends on grade, size, location, and pt condition

• GRADE I: Pilocytic Astrocytoma

• GRADE II: Low Grade (diffuse) Astrocytoma

• GRADE III: Anaplastic Astrocytoma

• GRADE IV: Glioblastoma Multiforme (GBM)

Glial Cell Tumor: Glioblastoma Multiforme

• Most common and aggressive adult primary glioma tumor that typically develop from astrocytes

• Grade IV astrocytoma

  • rapid expansion into adjacent tissues

  • associated w/ swelling around mass, nectrotic cavity

• Symptoms:

  • headache, seizure, vision changes, LOC, slurred speech, cognitive decline, decreased motor function

• Poor prognosis

  • Median survival 12-18 months

MRI Appearance:

• T1:

  • hypo - iso

  • central heterogeneous signal

• T1 C+ (Gd): variable, almost always peripheral that surrounds necrosis

• T2/FLAIR:

  • hyperintense

  • surrounded by vasogenic edema

  • lacks T2/FLAIR "mismatch" sign

• GRE/SWI:

  • susceptibility artifact from blood products

• DWI/ADC

  • solid component

  • elevated signal common on DWI in the solid/enhancing component

Meningioma

• Slow-growing tumors that arise from the meninges

• Usually benign, incidental finding

• Symptoms:

  • headache, seizure, vision/hearing changes, weakness

• Treatment:

  • Monitoring, resection, chemo/radiation (Grade III)

MR Appearance

• Smooth, round, solid

• Bright post contrast enhancement

GRADE I: Benign, slow growing, low recurrence

GRADE II: Atypical Meningioma: higher rate of recurrence

GRADE III: Anaplastic/malignant Meningioma: rare, rapid growth, high rate of recurrence

Central Nervous System Lymphoma

• Non-Hodgkin malignancy of lymphatic cells within the CNS of immunocompromised/AIDS patients

• Symptoms:

  • N/V, weakness, headache, AMS, hearing/vision loss, dysphagia

• Treatment depends on med hx:

  • AIDS: HIV meds, steroids, radiation/chemo

  • Non-AIDS: chemo and monoclonal antibodies w/ radiation, stem cell transplant, or radiation only

Pineal Gland Tumors

• Pineal parenchymal tumors

• Often incidental finding

  • cystic lesions most common

GRADE I: Pineocytoma

GRADE II/III: Papillary Pineal Tumor

GRADE IV: malignant Pineoblastoma

Germinoma

• most common malignant germ cell tumor in the CNS

• 80-90% of all germinomas are located in the pineal region

Metastatic Brain Cancer

• Secondary CNS neoplasms spreading via blood or lymph from distant primary sites

  • lung (20%)*

  • Breast

  • melanoma

  • colon

  • kidney

  • thyroid

• typically found at gray-white matter junctions

MR Appearance

• varies widely, difficult to diagnose

• T1: iso - hypo

  • hemorrhagic = high signal

  • non hemorrhagic melanoma = high signal due to paramagnetic properties of melanin

• T1+gad: can be intense uniform, punctate, or ring-enhancing

• T2: hyperintense (can depend on hemorrhage/melanin)

  • mucinous mets - LOW

• FLAIR: hyperintense (including edema)

• DWI/ADC: edema is dark on DWI, bright on ADC. tumor is opposite

Autoimmune: Multiple Sclerosis

CNS inflammation that results in damage to the myelin sheath around the axons with the brain and spinal cord

• most common in females (2:1 female:male)

• Diagnosed during adolescence up to age 50

• Symptoms:

  • Optic Neuritis (optic nerve lesion)

  • Ataxia (cerebellar lesion)

  • Parasthesia (cerebral lesion)

• characteristically produce oval, periventricular white matter plaques

• on FLAIR MRI (gold standard sequence)

• Post contrast evals acuity of plaques (acute, subacute, or chronic)

Autoimmune: Neurosarcoidosis

A CNS manifestation of systemic sarcoidosis where non-caseating granulomas form in brain tissue or meninges (~20% of sarcoidosis cases/1-% symptomatic)

• Sarcoidosis: condition where immune system overreacts, creates granulomas (mass of granulation tissue)

Symptoms:

• optic or facial palsies, hormone disorders (pituitary granulomas), seizure, weakness, AMS, dysphagia

MR Appearance:

• T1: iso or hypo to gray matter

• T2: hyper to surrounding tissue

• T1+GAD: homogenous, parenchymal (top left) or leptomeningeal (bottom rt) enhancement

Autoimmune: Neurovasculitis

Inflammatory process affecting the lining of blood vessels in the brain and meninges. more common in males.

• Primary: confined to CNS only

• Secondary: inflammatory process or infection*

  • Further characteriation of Secondary Vasculitis determined by affected vessels

MR Appearance:

• T2/FLAIR: high signal in white matter

• GRE/SWI: detects microbleeds

• MRA: vascular narrowing

• 3D T1: vessel wall imaging

Infection: Meningitis

Inflammation of the protective meningeal coverings of the brain and spinal cord. Can be viral, bacterial (pyogenic)*, or fungal. DX by LP

Symptoms:

• Headache, fever, photophobia, stiff neck, N/V

  • left untreated can lead to abscess, hydrocephalus, cerebritis, thrombosis, infarcts, ventriculitis, empyema

Best evaluated on T1 post-contrast by observing leptomeningeal enhancement

Infection: Cerebral Abscess

Necrotic area of brain tissue surrounded by an inflamed vascular capsule resulting from cerebritis

Risk Factors: IVDU, CHD, lung infections, Sinus infections, dental abscesses, meningitis, sepsis

MR Appearance:

• T1:

  • central/peripheral - low intensity (hyper to CSF)

  • ring enhancement post contrast

• T2/FLAIR:

  • central/peripheral - high intensity (hypo to CSF, no FLAIR attenuation)

  • abscess capsule may be visible as thin rim of intermideiate - low signal

• DWI: central high signal

• SWI: low intensity rim

4 Stages of Brain Infection

1. Early Cerebritis (infections w/o capsule or pus)

2. Late Cerebritis

3. Early Abscess (encapsulation 10 days post onset)

4. Late Abscess (14 days or longer after encapsulation)

Neurocysticercosis

Parasitic CNS infection from ingesting tapeworm eggs from undercooked pork, leading to cyst formation in the brain parenchyma

• Common in central/south american countries

• Can take years for eggs to manifest in the brain tissue

MR Appearance:

• T1: hyperintense

• T2/FLAIR: hyperintense

• T1+GAD: cyst wall enhancement

Leukodystrophies

A group of inherited genetic disorders causing abnormal glial cell function and defective myelin sheath development, causing abnormal white matter growth

• all genetic but can originate from autoimmune, infectious, or metabolic conditions

• effects newborns to adults

Symptoms:

• abnormal movement, difficulty walking, dysphagia, learning/behavioral changes, hearing/vision changes

MR Appearance:

• symmetric T2/FLAIR white matter hyperintensities

Optic Meningioma

Nerve sheath tumors

• Rare

• slow growing

• benign

Choroidal Melanoma

Most common primary malignant intraocular tumor…tho still rare

Originate from melanin cells within the orbit

Aggressive, 50% met