RITE imaging

MSA

• hot cross bun sign

• hyperintensities of cerebellar peduncles

eye of the tiger sign

• globus pallidus T2 hypointensity with central hyperintensity

• PKAN

• iron deposition disorder

PSP imaging findings

• micky mouse & hummingbird signs from midbrain atrophy

• cerebellar atrophy, particularly in vermis

panda sign

• symmetric hyperintensities of putamen > caudate, thalamus, brainstem; red nuclei are eyes

• wilson’s disease

• from copper deposition

bilateral MCP sign

• fragile X-associated tremor/ataxia syndrome (FXTAS)

developmental venous anomaly

• network of dilated veins

• caput medusae sign

• typically asymptomatic, rarely cause hemorrhage

capillary telangiectasia

• dilated capillaries

• most common in pons

• typically asymptomatic, rarely cause hemorrhage

• slightly bright on T2, subtle enhancement

cavernoma

• dilated vascular cavity lined by vascular endothelium

• typically supratentorial

• popcorn appearance on MRI, core can be hyperintense, dark rim on T2

• can cause seizures, can bleed

cerebral AVM

• tangle of connected arteries & veins

• can cause bleed, seizures, headaches, ischemic stroke (steal phenomenon)

• bag of worms appearance on MRI

• requires angiography for diagnosis

• resection can be curative

fibromuscular dysplasia

• string of beads

• commonly affects ICAs and verts

• more common in females

• slight incr risk TIA/stroke and dissection but often asymptomatic

moyamoya

• stenosis & occlusion of distal ICA and proximal MCA with prominent collateralization over time

• treated with antiplatelets, EC-IC bypass

• “puff of smoke” appearance on angio due to collateralization

CADASIL/CARASIL

• cerebral autosomal dominant/recessive arteriopathy with subcortical infarcts and leukoencephalopathy

• NOTCH3 mutations

• causes progressive cognitive decline, recurrent ischemic strokes (often lacunar), migraines

  • MRI features symmetric WM hyperintensities, including in anterior temporal poles

… are bright on CT

• acute blood (hyperacute can be isodense, old is hypodense)

• bone

• choroid plexus

• minerals

• calcification

… are dark on CT

• old blood

• CSF

• air

what structures are dark & bright on T1 MRI

bright: fat (lipoma), mineral deposition, cortical necrosis, melanin, proteinacous stuff

• My Best Friend is Pretty Cool (melanin, blood - subacute, fat, protein, cholesterol/calcium)

dark: CSF, edema, bone, most pathology (incr water content)

white matter brighter than grey matter

what structures are dark & bright on T2 MRI

bright: fat, CSF, edema, most pathology

dark: fat, bone

gray matter brighter than white matter

how to age blood on MRI

T1 generally goes from iso > bright > dark

T2 more complicated

hyperacute: isodense on both

acute: isodense on T1, dark on T2

early subacute (1 week): bright on T1, dark on T2

late subacute (>1w, <1mo): bright on both

chronic: dark on both

FLAIR same as T2

alternative way to remember: I Be IdDy BiDy BaBy Doo Doo

differential for FLAIR non-suppression

CSF spaces still bright

• hyperoxygenation

• SAH

• meningitis

differential for diffusion restriction

• acute-subacute infarct (arterial or venous)

• abscess (core)

• tumors (rim)

• PRES

• CJD (cortical)

• diffuse anoxic injury

• lymphoma

• ODS

• carbon monoxide toxicity

• acute demyelination

• hypoglycemia (cortical)

what structures enhance on T1-post contrast MRI

• blood vessels

• venous sinuses

• choroid plexus

• pineal gland

• sinuses (the nose knows)

• tumors, abscess, infections, subacute stroke, active demyelination, inflammation

… are dark on GRE

• blood

• iron, calcium, manganese

possibilities for bright lesion on DWI

dark on ADC > restricted diffusion

iso on ADC > T2 shine through

bright on ADC > facilitated diffusion

imaging findings in intracranial hypotension

• sagging brainstem

• downward displacement of cerebellar tonsils

• slit ventricles

• diffuse pachymeningeal (dural) enhancement

• subdurals, can be bilateral

imaging findings in IIH

• partially empty sella

• optic nerve tortuosity, dilated optic nerve sheaths, visible protrusion of optic head into eyeballs

• stenosis of transverse sinus

differential for pituitary mass

• pituitary adenoma: homogeneously enhancing

• craniopharyngiomas: cystic/calcified

• rathke cleft cyst: non-enhancing

craniopharyngioma

• suprasellar

• cystic/calcified

pituitary apoplexy

• ischemia/hemorrhage of pituitary gland

• higher risk if existing macroadenoma

• often postpartum

• p/w HA, CN deficits, panhypopituitarism

colloid cyst

benign but can cause acute hydrocephalus

EOM enlargement

can be caused by thyroid eye disease, ocular myositis, orbital pseudotumor

ODS

• central pons

• hypodense on CT

• can be diffusion restricting

• hyperintense on T2/FLAIR

pulvinar sign - bilateral FLAIR hyperintensities of pulvinar thalamic nuclei

can be seen in CJD, Fabry, status, ADEM

hockey stick sign

bilateral hyperintensity of pulvinar nuclei and medial thalamus

can be seen in CJD or Wernicke’s

Dandy Walker malformation

• agenesis/hypoplasia of cerebellar vermis resulting in cystic enlargement of 4th ventricle

• can exist with or without hydrocephalus

• can be hypotonic & ataxic

methanol toxicity

• bilateral putaminal hemorrhages/necrosis

• can also see damage to optic nerves

lissencephaly

• pachy or agyria (smooth brain)

• enlarged ventricles

porencephaly

“pore” lined with white matter, not communicating with ventricles

schizencephaly

• fluid-filled cleft that communicates with lateral ventricles

• lined with gray matter

arachnoid cyst

• often congenital

• extra-axial

• same as CSF signal

aqueductal stenosis

• can be congenital or acquired

• narrowing/obstruction of cerebral aqueduct between 3rd & 4th ventricles

• marked enlargement of 3rd and lateral

• effacement of cortical sulci

gray matter heterotopia

• disorder of neuronal migration

• nodules/bands of gray matter in abnormal locations, can be periventricular, subcortical or lobar

• isodense on T1/T2/FLAIR

• cause seizures

• includes subependymal nodules (seen in tuberous sclerosis)

temporal lobe encephalocele

outpouching through skull defect

associated with epilepsy

septo-optic dysplasia

• hypoplastic or absent septum pellucidum

• hypoplastic corpus callosum

• hypoplastic optic nerves

molar tooth sign

associated with Joubert syndrome (cerebellar vermis hypoplasia)

superior cerebellar peduncles horizontal & thick

Alexander disease, type of genetic demyelinating leukodystrophy with bifrontal predominance

imaging findings in CJD

• pulvinar & hockey stick signs (bilateral FLAIR hyperintensities in pulvinar & medial thalamus)

• cortical diffusion restriction

imaging findings in Alzheimer’s

atrophy, particularly of temporal lobes

PET hypometabolism in parietal & temporal lobes

Huntington’s disease

• atrophy of caudate head causes enlargement of frontal horns

Neuroacanthocytosis

• also cause BG degeneration

Fahr disease

disorder of calcium deposition and cell loss

primarily in BG and cortex

DESH (disproportionally enlarged subarachnoid space hydrocephalus)

associated with NPH

abscess with double rim sign

• outer rim hypointense

• inner rim hyperintense

• can diffusion restrict in core

• can have surrounding vasogenic edema

differentiate from glioma which also has hypodense rim but more heterogenous enhancement and peripheral diffusion restriction

glioblastoma

• multicystic

• heterogeneously enhancing

• vasogenic edema

ventriculitis

enhancement lining ventricles

can occur with EVD, bacterial meningitis, ruptured brain abscess, skull infection

neurocysticercosis

• hyperdense/calcified on CTH

• hypointense core on MRI with edema, can rim-enhance

toxoplasmosis

• tend to be in BG but can be anywhere

• rim or nodular enhancement

• often with surrounding edema

HSV encephalitis

• affects temporal lobes & limbic structures

• swollen, hyperintense, can be diffusion restricting or hemorrhagic

• can see leptomeningeal enhancement

differential includes autoimmune (NMDAr) and paraneoplastic (LGI1) encephalitis which also favor temporal lobes

congenital CMV

• ventriculomegaly/hydrocephalus

• periventricular calcifications

• microcephaly

rhombencephalitis

infection/inflammation of brainstem & cerebellum

most common infectious cause is listeria, also enterovirus 71 and HSV. can also be autoimmune (Behcet’s, SLE) or paraneoplastic

bickerstaff brainstem encephalitis

• AMS, ataxia, ophthalmoplegia

• post-infectious

• +GQ1b antibodies

progressive multifocal leukencephalopathy (PML)

hypointense on T1, hyperintense on T2, can see peripheral patchy diffusion restriction, typically non-enhancing

ADEM

• large multifocal demyelinating lesions, can have tumefactive appearance

• often involving cortex, subcortical grey matter, thalamus, brainstem

• presents acutely in child with viral illness, typically monophasic

bilateral thalamic infarct

artery of percheron stroke or straight sinus thrombosis

core vs penumbra on perfusion imaging

rCBG < 30% = core = infarcted tissue

Tmax >6s = penumbra = tissue at risk

subarachnoid hemorrhage

best seen on CTH

anoxic brain injury post-arrest

• loss of gray-white differentiation

• swollen sulci, small ventricles

• pseudo-SAH from proteinacous leakage into subarach space

air embolism

• punctate or curvilinear hypodensities

• air darker than CSF

vein of Galen malformation

presents in babies with high output heart failure

hypothalamic hamartoma

benign malformation/tumor

p/w refractory gelastic seizures, precocious puberty

spinal imaging

T1: CSF dark, pathology often dark

T2: CSF bright, pathology often bright

STIR (short tau inversion recovery): T2 with suppression of fat

diffuse idiopathic skeletal hyperostosis

• calcification and ossification of anterior longitudinal ligament

• can accelerate spondylosis

klippel fiel syndrome

• incomplete segmentation of C-spine

• congenital

• limited mobility of neck and upper spine

epidural lipomatosis

• accumulation of excess fat in spinal epidural space resulting in spinal cord compression

• associated with long-term steroid use

chordoma

• slow growing

• thought to arise from cellular remnants of notocord

• can cause cord compression

• can grow along cord or in brain adjacent to sphenoid bone

rheumatoid pannus

inflammatory synovial tissue commonly growing in cervical spine around C1-2, can cause neck pain/instability and cord compression

spinal epidural abscess

• non-enhancing core w rim of enhancement

• can be diffusion restricting in core

spinal epidural hematoma

• heterogeneous appearance but mostly hyperintense on T1/2

multiple myeloma vertebral lesions

spinal meningioma

• well circumscribed

• dural attachment (dural tail sign)

• homogeneous enhancement

spinal schwannoma

• arise from spinal nerve roots

• homogeneous enhancement

• differentiated from spinal meningioma by lack of dural tail

spinal arachnoid cyst

• CSF-filled cyst within arachnoid space

• can be congenital or from trauma (most commonly T spine)

arachnoid web

• scalpel sign

• thickened band of arachnoid over dorsal cord

spinal ependymoma

• central cord (arise from central canal)

• enhancing

• often cystic looking

• often associated syrinx

spinal astrocytoma

• intramedullary

• often eccentric (arise from cord parenchyma)

• poorly defined margins

• most enhance

spinal hemangioblastoma

• intramedullary

• nodular appearance

• may see vascular flow voids

• vividly enhancing

features of different causes of LETM

NMO - central often involving gray & white matter, bright & spotty, patchy enhancement, can see prominent swelling

MOG - central, sometimes restricted to gray (H sign), often non-enhancing, can involve conus

sarcoid - central, “trident” sign

paraneoplastic - tract-specific (often dorsal/lateral columns)

H sign of grey matter restricted myelitis

associated with MOGAD

trident sign

associated with neurosarcoid

spinal dural AVF

• present with gradual but progressive pain, leg weakness/numbness, bladder/bowel changes

• flow voids on T2

• can see intramedullary hyperintensity due to edema, often involving conus

• confirmed with DSA

owl eye sign

• spinal cord infarct

• anterior horn cells

• can also be seen in ALS, polio

subacute combined degeneration

• demyelination of dorsal columns

• B12 deficiency, syphilis, copper deficiency, methotrexate toxicity

syringomyelia

• collection of CSF in central cord around central canal

chiari malformation

I: downward displacement of cerebellar tonsils, often associated with syringomyelia

II: downward displacement of medulla, 4th ventricle and cerebellum through foramen magnum, often associated with myelomeningocele

tethered cord

• progressive stretching from lengthening of spinal column

• conus terminates at low position

• can see other imaging findings of spinal dysraphism

• can be associated with terminal lipoma (lipmeningocele)