• CBF - cooler = worse
  • CBF < 30% criteria
• MTT - hotter = worse
  • Tmax > 6.0 seconds
• Report:
  • Mismatch volume
  • Mismatch ratio

• Start with TTP and delay images to spot abnormality
• MTT & CBF
• Then CBV to determine core vs penumbra

• Sample
  • Acute R MCA territory infarct with MCA/PCA penumbra.
  • CBF < 30% of 17 mL, Tmax > 6 sec of 155 mL, and mismatch volume of 127 mL (ratio 8.5).

• AIF = Arterial In-flow
• VOF = Venous Out-flow
• CBF = Cerebral Blood Flow (core infarct/overestimates infarct)
• CBV = Cerebral Blood Volume (core infarct/good for visual estimate)
• Tmax = Arterial in-flow to capillary time (ischemia)
• MTT = Mean Transit Time = Capillary transit time (ischemia/least sensitive)
• TTP = Time to Peak = Arterial in-flow to capillary time AND capillary transit time (ischemia)

• <5 - tPA safe
• >5 - safety unknown

• Recurrent artery of Heubner (aka medial lenticulostriate)
  • branch of ACA
  • caudate head, ant limb of internal capsule, septum pellucidum
• Lateral lenticulostriate
  • branch of MCA
  • lentiform nucleus, caudate capsule, internal capsule
• Thalamic and midbrain perforators
  • branch of PCA
• SCA
  • superior cerebellum
• AICA
  • inferolateral pons
  • middle cerebellar peduncle
  • anterior cerebellum
• PICA
  • medulla
  • posterior and inferior cerebellum

• Areas with hemorrhage count as abnormal in aspects scoring.
• Dense MCA does not count.

• Part one is from the origin to the point at which it enters the transverse foramina of either the fifth or sixth cervical vertebra.
• The second part courses within the intervertebral foramina
• The third part exits behind the atlas and heads towards the foramen magnum.
• The fourth part (intracranial) begins as it pierces thedura and arachnoid mater at the base of the skull, and ends as it meets its opposite vertebral artery to form the midline basilar artery at the level of the medullopontine junction.

• 1 gad enh or 9 T2 hyper lesions
• 1+ infratentorial lesions
• 1+ juxtacortical
• 3+ periventricular

• Devic's dz - transverse myelitis & B optic neuritis
  • severe
• Balo's dz - MS lesion w/ concentric demyelination & nl brain
• Schilder's dz - acute, rapid, B symmetric demyelination
  • large, well-circ involving centrum & occ lobes
• Marburg variant - repeated relapses w/ rapidly accumulating disability

• Lyme
• vasculidities
• HTN & ischemic wm lesions
• virchow-robin spaces
• migraine
• trauma (DAI)
• UBO's

• Causes - measles, varicella, mumps, rubella, EBV, CMV, M. pneumoniae
• multiple, large high T2 lesions which may enhance in a nodular or ring pattern
• usually affects cerebrum but may enlarge cord
• fulminant type is acute hemorrhagic leukoencephalitis (Hurst's dz)
• diffuse multifocal perivascular demylelination & hemmorhage in cerebral WM w/ sparing of U-fibers

• JC virus
• assoc w/ immunocompromise
• asymmetric parietal & frontal involvement, but can be anywhere
• low T1, high T2
• no enhancement, no mass effect

• symmetric supratentorial demyelination
• does not extend to GW junction
• no mass effect
• atrophy

• sequela of measles infection
• patchy WM demyelination sparing U-fibers
• asymmetric gray & white matter involvement in parietooccipital region

• older men & women
• assoc w/ HTN & lacunar infarction
• broad high signal areas w/i FPO WM
• U-fibers spared

• inherited arterial dz
• recurrent TIA, stroke, dementia, depression, pseudobulbar palsy, hemi/quadriplegia
• F/T/insula w/ subcortical U-fiber involvement
• High T2 in WM (periventricular, deep WM, BG, brain stem)

• occurs after anoxic episode severe enough to produce coma
• recovery after 24-48 hrs, then precipitous decline in 2-wk period to death
• high T2 throughout WM particularly involving corpus callosum, subcortical U-fibers, int/ext capsules
• diffusion positive

• high T2 in PO cortex & SCWM
• can extend to other regions
• enhancement variable
• does not restrict
• assoc w/
  1. malignant HTN
  2. toxemia of pregnancy
  3. renal dz
  4. immunosuppressive drugs (cyclosporine, FK-501)
  5. antiphospholipid ab syndrome
  6. porphyria

• alcoholic, debilitated, malnourished pt's w/ rapid correction of hyponatremia
• may involve extrapontine stx (thalamus, caudate, putamen, internal external & extreme capsules, claustrum, amygdala, cerebellum, deep gray matter)
• high T2 in pons w/ peripheral sparing and sparing of CST

• Biconvex shape (lentiform)
• Usually in the temporoparietal regions but can be in the occipital region
• Usually accompanied with a skull fracture and tear of a branch of the middle meningeal artery
• Does NOT cross suture lines, but can cross midline
• Usually has more mass effect, but not always, depending on size

• Subdural is crescent shaped typically along the temporoparietal regions as well, and is associated with tearing of the bridging veins
• DO cross sutures lines, but DO NOT cross midline
• Fracture less commonly associated
• Can be bilateral and also interhemispheric, and along the tentorium.

• Subarachnoid you look for blood in the fissures, the basilar cisterns, interhemispheric, or in the interpeduncular fossa
• Blood in/around the circle of willis = star of texaco sign
• Blood along the posterior falx around the sinuses, you can get the delta sign

• Approach to intraparenchymal hemorrhage
  • If Ca²⁺ near hemorrhage think AVM
  • Perform MR immediately (before blood products become bright on T1)
  • If negative, f/u to resolution
• Approach to subarachnoid hemorrhage
  • Obtain CTA while pt is on the table
• Non-aneurysmal SAH = Venous hemorrhage
  • Perimesencephalic Cisterns
  • Small amount of blood
  • Asymptomatic

• Common Locations
  • AComm (33%)
  • PComm (33%)
  • MCA Bifurcation (20%)
  • Basilar Tip

• > 2.5 cm
• Common location is cavernous carotid

• Type 1
  • dural AV fistula
  • acquired lesion
  • most common spinal AVM
  • 1A - single feeding artery
  • 1B - multiple feeding arteries
  • nidus w/i or on dura of proximal nerve root sleeve in neural foramen
  • progressive myelopathy & (rarely) SAH
  • tx is surgical excision of nidus or endovascular glue
• Type 2
  • glomus AVM
  • intramedullary location
  • compact nidus
  • high-flow, produce flow-voids
  • drainage into coronal venous plexus
  • engorgement of post and/or anterior median vein
  • perimedullary flow voids
  • cord scalloping
  • serpentine enhancement
  • may cause enhancement in distant locations in cord
• Type 3
  • Juvenile-type AVM
  • more diffuse
  • less prone to hemorrhage
  • adolescents & young adults
  • poorer prognosis, not amenable to surg excision
  • typically cervical region
  • can involve extramedullary, extradural, and extraspinal structures
  • multiple arterial feeders, often from several different levels
• Type 4
  • Perimedullary (conus/cauda equina) fistulas
  • vary in severity
  • 4A - slow flow, mod enlg veins, single feeding art
    • tx surgically
  • 4C - high flow, markedly dil veins, multiple feeders
    • tx endovascularly
  • progressive myelopathy, SAH (50%), acute paraplegia

• Based on:
  • Size
  • Eloquence
  • Drainage (deep vs superficial)

• Tonsilar invagination through the foramen magnum into the spinal canal with variable degrees of tonsilar ectopia
• There is normal position of the 4th ventricle
• Syringohydromyelia is an associated finding
• Two components are necessary for the diagnosis - tonsilar herniation and syringohydromyelia
• May have associated basilar invagination, assimilation of C1 to the occiput, and Klippel-Feil

• Dysgenesis of the hindbrain with caudally displaced 4th ventricle and caudal elongation of the medulla and vermis
• Concurrent anomalies include: myelomeningocele, mesencephalic beaking (tectal beaking), enlarged massa intermedia, accessory anterior commissure, absence of the corpus callosum (which manifests as elevated third ventricle), partial absence of the falx, and cervicomedullary kinking
• Abnormalities of the bony vault include Luckenshadel (or lacunar) skull (appears as soap bubble lucencies in the upper calvaria)
• A dysplasia of bone and underlying dura
• Can be seen with any cause of meningocele and myelomeningocele

* A rare lesion that consists of herniation of cerebellum into a high cervical or occipital encephalocele

* Consists of extreme cerebellar hypoplasia without associated displacement

• Hyperacute (0-6 hrs)
  • iso T1/T2
  • high DWI/low ADC
    • DWI may be positive within 2 hours
• Acute (6 hrs-4 days)
  • low T1/high T2
  • mass effect
  • high DWI/low ADC
• Subacute (4-14 days)
  • low T1/high T2
  • resolving mass effect
  • T2 shine through on diffusion
  • pseudonormalization of ADC
• Chronic
  • encephalomalacia
  • high T2
  • T2 shine through on diffusion
  • high ADC

• IV w/i 3 hrs
• catheter directed w/i 6hrs

• Lateral medullary infarct
• affects CN 9,10
• causes hoarsness and dysphagia

• Cisternal segment
  • The nerve emerges immediately beneath the pons, lateral to the abducens nerve and medial to the vestibulocochlear nerve, and is joined by the nervus intermedius which has emerged lateral to the main trunk. Together the two travel through the cerebellopontine angle to the internal acoustic meatus.
• Meatal (internal auditory canal) segment
  • Having been joined by the nervus intermedius they are located in the superior upper quadrant, above the falciform crest and anterior to Bill's bar.
• Labyrinthine segment
  • As the facial nerve and nervus intermedius pass through the anterior superior quadrant of the internal acoustic meatus it enters the Fallopian canal, passing anterolaterally between and superior to the cochlea (anterior) and vestibule (posterior), and then runs back posteriorly at the geniculate ganglion (where the nervus intermedius joins the facial nerve, and where fibers for taste synapse - see below). It is here that three branches originate: the greater superfical petrosal nerve, the lesser petrosal nerve and the external petrosal nerve. The labyrinthine segment is the shortest only measuring 3 to 4 mm. It is also the narrowest and the most susceptible to vascular compromise (see below).
• Geniculate ganglion
• Tympanic segment
  • As the nerve passes posteriorly from the geniculate ganglion it becomes the tympanic segment (8-11 mm in length), and is immediately beneath the lateral semicircular canal in the medial wall of the middle ear cavity. The bone of the Fallopian canal is often dehiscent in the area of the oval window in 25-55% of postmortem specimens, having mucosa in direct contact with the nerve. The nerve pass posterior to the cochleariform process, tensor tympani and oval window. Just distal to the pyramidal eminence the nerve makes a second turn (second genu) passing vertically downwards as the mastoid segment. The tympanic segment has no branches.
• Mastoid segment
  • The mastoid segment, measuring 8 to 14mm in length, extends from the second genu to the stylomastoid foramen, through what is confusingly referred to as the fallopian canal. It gives off three branches:
    • nerve to stapedius
    • chorda tympani - terminal branch of the nervus intermedius carrying both secretomotor fibres to the submandibular gland and sublingual gland and taste to the anterior two thirds of the tongue.
    • nerve from the auricular branch of the vagus nerve (CN X) - pain fibers to the posterior part of the external acoustic meatus hitchhike from the jugular foramen.

Typically enhancement is seen:

• anterior genu (geniculate ganglion)
• posterior genu (between tympanic and mastoid segments)
• some enhancement can also be seen in the labarynthine, tympanic and mastoid segments.
• proximal greater superfical petrosal nerve

No enhancement should be seen in:

• cisternal segment (that in the cerebellopontine angle)
• meatal segment (that in the internal acoustic meatus)
• extracranial segment (beyond the stylomastoid foramen)

• If shown a lateral C-spine film, think of three things
  1. trauma (fx)
  2. abscess
  3. mass
• Terminal Ventricle
  • cavity at the level of the conus medullaris
  • normal variant
  • seen almost exclusively in children <5 yrs old
  • if persistent, may be associated with tethered cord

• astrocytoma
  • infiltrating
  • most common in C-spine
• ependymoma
  • central, well-defined, cystic changes, hemorrhage, patchy enhancement
  • most common at conus
• hemangioblastoma
  • feeding vessel (flow voids)
  • cystic component
  • most common in C-spine

• schwannoma
• neurofibroma
• meningioma
• drop mets
• arachnoid cyst - usually thoracic spine, posterior
• epidermoid cyst

• disk
• meningioma
• schwannoma
• neurofibroma
• mets/myeloma/lymphoma
• epidural abscess
• epidural hematoma
• synovial cyst
• leptomeningeal enhancement
• sarcoid

• Parainfectious (occurring at the time of and in association with an acute infection or an episode of infection).
  • Viral: herpes simplex, herpes zoster, cytomegalovirus, Epstein-Barr virus, enteroviruses (poliomyelitis, Coxsackie virus, echovirus), human T-cell, leukemia virus, human immunodeficiency virus, influenza, rabies
  • Bacterial: Mycoplasma pneumoniae, Lyme borreliosis, syphilis, tuberculosis
• Postvaccinal (rabies, cowpox)
• Systemic autoimmune disease
  • Systemic lupus erythematosis
  • Sjogren's syndrome
  • Sarcoidosis
• Multiple Sclerosis
• Paraneoplastic syndrome
• Vascular
  • Thrombosis of spinal arteries
  • Vasculitis secondary to heroin abuse
  • Spinal arterio-venous malformation

• drop mets
• sarcoid
• leukemia, lymphoma
• CMV
• Guillan-Barre
• CIDP (also enlarged)
• meningitis

• Snake eyes appearance on axial imaging
• Anterior spinal artery infarct
• Increased T2 in central gray matter

• normal variant
• anemia
• chronic disease
• neoplastic processes such as lymphoma, metastatic disease, or myelodysplastic syndromes.

• Lymphoma
• Extramedullary Hematopoesis
• Myelofibrosis
• (XRT will increase fatty marrow)

• B12 deficiency
• Syphillis

• Cushing's Dz
• Steroids
• Congenitalß

• Giant Cell
• Osteoblastoma/Osteoid Osteoma
• ABC
• Plasmacytoma
• EG

• Chordoma
• ABC
• Leukemia
• Lymphoma
• Hemangioma
• Met/Myeloma
• EG

• Increased Intraspinal Pressure
  • Tumor
  • Syrinx
  • Communicating HCP
• Dural Ectasia
  • NF-1
  • Marfan
  • Ehlers-Danlos
• Congenital
  • Achondroplasia
  • Mucopolysaccharidoses → Hunter/Hurler/Morquio's (look for beaking
  • Osteogenesis Imperfecta Tarda
• Bone Resorption
  • Acromegaly

• VACTERL
• NF-1
• Chiari II
• Anterior Meningocele

• Malignancy tends to involve the pedicles, whereas benign does not
• Look for other levels of involvement - if you see noncompressed vertebral bodies at other levels which also have abnormal signal, then you can assume malignant
• Cortical destruction is a feature of malignancy
• Malignant frxs tend to show abnormal T1 signal involving >80% of the v.b., benign has less

• cavernous hemangioma (capillary in children)
• schwannoma
• lymphangioma
• varix
• optic n tumor (meningioma, glioma)
• pseudotumor - pain, opthalmoplegia, proptosis, unilateral, enlarged lacrymal gland
  • Tolosa-Hunt involves orbital apex and cavernous sinus
• thyroid opthalmopathy - spares tendon insertions, often bilateral, does not enhance
• lymphoma

• lacrymal gland
  • lymphoma, pseudotumor
• sinus disease
  • mucocele, invasive infections, neoplasm
• orbital bone disease
  • fibrous dysplasia, osteomyelitis, subperiosteal abscess, tumors, trauma
• nasal disease
  • infection, neoplasm
• dermoid
• rhabdomyosarcoma
  • common in children
• mets

• mets
• inflammation
• thyroid eye disease
  • bilateral
  • sparing of muscle tendons
• pseudotumor
• lymphoma

• lymphoma
• sarcoid
• inflammatory
  • Sjogren's
  • Miukulicz's
• epithelial tumors
  • pleomorphic adenoma
  • adenoid cystic
  • mucoepidermoid
• mets

• use term 'optic nerve sheath complex'
• Optic Neuritis → hyperintense, enlarged
• Glioma → enlarged nerve, do not enhance
• Meningioma → crescentic
• Sarcoid → enhances
• Lymphoma/leukemia
• Pseudotumor
• Graves

• Retinoblastoma
  • intraocular mass
  • high density (Ca²⁺, hemorrhage)
  • 30% bilateral
• Melanoma
  • thickening of choroid, usually posterior
  • usually unilateral
  • high T1, low T2 with enhancement
• Persistent Hyperplastic Primary Vitreous
  • unilateral small globe
  • no calcification
• Coats' Disease
  • unilateral dense vitreous w/ focal mass or Ca²⁺
• Drusen
  • focal Ca²⁺ in optic nerve head
  • usually bilateral and asymptomatic
  • may be mistaken for papilledema

• aberrant ICA
• glomus tumor (tympanicum)
• cholesteatoma

Maxillary sinus lesion extending to base of tooth? → Think dentigerous cyst
Esthesioneuroblastoma has a bimodal age distribution → children (11-20) and older adults (51-60)

• Expansion of sinus
• Complete filling of sinus
• Order of prevalence = FEMS (frontal>ethmoid>maxillary>sphenoid)

• typically arises from the lateral nasal wall and extends into the ipsilateral ethmoid or maxillary sinus
• worry about coexisting SCC (common)

• benign polyp arising in antrum and extending into the nasal cavity
• no sinus expansion

Sjogren's can look like fatty replaced salivary glands

* Probably should add lymphoma to all of these, especially in HIV pts

• Child
  • PNET/Medulloblastoma
    • usually 4th ventricle, but can be in lateral vents
  • Choroid Plexus Papilloma/Carcinoma
    • lateral ventricles
    • always have hydrocephalus
  • Ependymoma
  • Teratoma
  • Astrocytoma
• Adult
  • Meningioma
  • Central Neurocytoma
  • Gliomas → Subependymoma, Astrocytoma

• Meningioma
• Hemangiopericytoma
• Schwannoma
• Metastases
• Lymphoma
• Dermoid
• Epidermoid
• Arachnoid cyst
• Bone neoplasm or infection
• Leukemia
• Sarcoidosis

• GBM
• Lymphoma
• Tumefactive MS (horseshoe enhancement)

Subependymal Spread Pattern → think of pineal germinoma

• high T2 signal in medial temporal lobes
• may have associated atrophy
• may enhance
• associated with small cell lung CA

• temporal lobe involvement
• may or may not enhance
• restricted diffusion

• T2 hyperintense areas in cortex and basal ganglia which restrict
• no enhancement

• Skull fractures that are accompanied by dural tears can result in the formation of a leptomeningeal cyst = “Growing Fracture”

• responsible for coma and poor outcome in the majority of patients with significant closed head injury
• specific anatomic structures involved
• body and splenuim (most common location) of the corpus callosum
• septum pellucidum
• dorso-lateral quadrant of the rostral part of the brainstem
• adjacent to the superior cerebellar peduncle
• diffuse damage to other axons including the int. capsule may also be present
• punctate subcortical hemorrhage and hemorrhage in WM adjacent to the 3rd vent also occur

Mets are very unlikely in the brainstem

• low signal intensity in periphery of midbrain, particularly posterior

• rare malformation with vermian aplasia or hypoplasia with fusion of the cerbellar hemispheres
• no 4th ventricle midline defect
• associated with fusion of the thalami and/or inferior colliculi
• associated with septo-optic dysplasia

• cerebellar hamartoma
• courdoroy appearance w/ calcification
• related to Cowden syndrome

• increased signal within the periaqueductal region of the midbrain, medial thalamic regions along the lateral walls of the third ventricle, and mammilary bodies
• triad of opthalmoplegia, ataxia, and altered mental status
• related to alcohol abuse

• The wisdom teeth are the 3rd molars (not pictured).

• PRES
  • Mostly FLAIR abnormality
  • Vasogenic edema
  • Thalamus usually spared
• Basilar territory infarct
  • Restricted diffusion
  • Matched DWI/FLAIR abnormality
  • Vascular territory

• Amyloid angiopathy
• Hypertensive microbleeds
• Cavernomas (familial)
• DAI
• Calcifications
• Hemorrhagic mets

• Metastasis
  • Multiple lesions with rim enhancement
  • No restricted diffusion
• Glioblastoma
  • Shaggy enhancement
• Lymphoma
  • Increased diffusion due to cellularity
  • NOT lightbulb bright on DWI
• Abscess
  • Restricted diffusion
  • Lightbulb bright on DWI

• Hypertensive (75%)
• AVM
• Dural AVF
• DVA
• Cavernous malformation
• Capillary telangiectasia
• Aneurysm
• Amyloid angiopathy
• Vasculitis
• Infarct
• Dural venous thrombosis

• Senescent
• Hypoparathyroidism
• Pseudo and Pseudo-pseudohypoparathyroidism
• Hyperparathyroidism
• TORCH
• AIDS
• TB
• Lead
• CO
• XRT/Chemo
• Mitochondrial diseases
• Fahr syndrome

• Prior Infection
• Hypoparathyroidism
• Lead Exposure
• Leukemia
• Prior XRT

• TPN (Manganese)
• Hepatic failure
• NF-1

• Dystrophic calcifications

• Tumor
  • Lymphoma
• Ischemia
  • Hypoxic encephalopathy/Near drowning
  • Venous infarction
• Neurodegenerative
  • Huntington's
  • Wilson's disease - bright T2 peripherally, dark centrally
  • Hallevorden-Spatz - bright T2 centrally, dark peripherally
  • Leigh - uniformly bright T2, involves pons, does not involve caudate
  • Kearns-Sayre
• Toxin
  • CO, CN poisoning
  • hypoglycemia
  • methanol

• Old age
• Chronic degenerative disease
  • Parkinson's
  • MS
• Childhood hypoxia

• GBM - will see edema
• Lyphoma - homogeneously enhancing
• XRT
• MS
• Marchiafava-Bignami

• Basically STL → Sarcoid, TB, Lymphoma
• Infection
  • TB
  • Fungal
  • Pyogenic
  • Cysticercosis
• Tumor
  • Leukemia/Lymphoma
  • Carcinomatosis
• Inflammatory
  • Sarcoid
  • Rheumatoid
  • Whipple's Disease

• Chiari I/II
• Intracranial Hypotension
• Mass Effect

• MS
• Sinus Thrombosis
• Olivopontocerebellar Atrophy
  • It's all in the name → ataxia/dementia syndrome w/ cerebellar and brainstem atrophy

• Leptomeningeal Carcinomatosis
• Meningitis
• Sarcoid, TB, Lymphoma

• Blood
• Pus (Ventriculitis)

• Hemorrhagic Infarct
• Trauma (usually anterior → Duret hemorrhage)
• AVM
• DAI

• Aqueductal Stenosis
• “Pencil” Glioma → surrounding the aqueduct

• Rathke Cleft Cyst
  • Simple, uniloculated
• craniopharyngioma (calcification)
• JPA

• Paraganglioma - aggressive appearance
• Schwannoma
• Meningioma

• Thyroglossal Duct Cyst
• Delphian Lymph Node
• Lymphangioma

• Lymphoepithelial
• Branchial Cleft
• Lymphangioma
• Abscess
• Cystic Tumors

• Warthin's Tumor
• Sjogren's
• Lymphoepithelial Cysts
• Lymph Nodes → Lymphoma, Skin Cancers
• Sarcoid

• ICA Dissection
• Tumor along course of ICA
• Pancoast Tumor

• Anemias → ß-thal
• Osteopetrosis
• Paget's

• Meningioma
• Fibrous Dysplasia

• Epidermoid
• Fibrous Dysplasia

• EG
• Metastatic Neuroblastoma

• Rheumatoid Arthritis
• Achondroplasia
• Down Syndrome

• Small foci of increased signal in the basal ganglia
• Causes:
  • lacunar infarctions
  • gliosis
  • dilated perivascular spaces
  • demyelination
  • nonspecific protein depositions
  • cysts
  • ventricular diverticuli