neuroradiology Flashcards
- brain imaging techniques
o Plain film: trauma, calcification, sella (enlarged due to tumor)
o CT: brain (stroke, trauma, tumors, CTA for stenosis, occlusion, aneurism and AVM), spine (degenerative disease and trauma).
o CT protocols: With or without contrast, CT Brain, CT brain with posterior fossa images, CT angiogram/venogram, CT perfusion, CT of sinuses, CT of orbit, CT of temporal bones, CT of mastoid bones, CT of skull, CT of face
o CT variables: Plain or contrast enhanced, slice positioning, slice thickness, slice orientation, slice spacing and overlap, timing of imaging and contrast administration, reconstruction algorhithm, radiation dosimetry
o CT terminology: Attenuation (hyperdense, hypodense or isodense) – measured in Hounsfield units. The brain is grey, white matter is usually dark grey, grey matter is usually light grey, CSF is black, bright = bone, calcifications, contrast, hemorrhage acute, hypercellular masses, metallic foreign bodies
o CT terminology: Voxel = volume element (3D), pixel (picture element, 2D). Window width (number of Hounsfield units from black to white), Level or Center (Hounsfield unit approx. mid-grey)
o MRI: Indicated in (white matter disease, MS, tumors, vascular malformation, epilepsy, stroke) Different T1 and T2 on hemorrhage (Oxy-hb is hypo on T1 and Hyper on T2, deoxy is hypo on both)
o US
o Interventional: angiography, myelography, biopsy
o Nuclear medicine
- traumatic head and brain injury (except facial trauma
o Head accidents : imaging include x-ray, CT, MRI and USG
o Intracranial hemorrhage: can be imaged with ultrasound (fontanells are not closed in children, so can be used, CT and MRI
o CT: hyperacute: isodense ACUTE/EARYLY SUBACUTE: increased density with hypodense rim LATE SUBACUTE: decreased density/isodense (RBC lysis, proteolysis of hb) CHRONIC progressive hypodensity (phagocytized hematoma, fluild filled brain defect)
o Various types of intracranial hemorrhage
o Epidural: Hemorrhage between skull and dura mater, usually due to head trauma, arterial (90%) MMA, venous (10%) dural sinus tear and is more frequent in children, Biconvex shape, Does not cross sutures, midline shift, not diluted by CSF, lucid In action
o Subdural: between dura mater and arachnoidea, traumatic and non-traumatic (atrophy), usually venous origin (bridging veins), enlarge slowly with initially minimal neurologic symptoms, crescent shape spreading over hemisphere, cross sutures, displaces brain, may mix with CSF due to arachnoideal tear, chronic SDH in elderly
o Subarachnoid: between arachnoidea and pia mater, traumatic and non-traumatic (aneurisma), traumatic rupture of cortical veins or arteries, cortical laceration, life´s worst headache (CT PRIMARY IMAGE METHOD), in MRI CSF dilution reduces visibility of SAH, flair helpful due to CSF-suppression
o Intraventrucular hemorrhage: May result from SAH or parenchymal hemorrhage extending into ventricles, may result from hemorrhage within tumor or AVM
o Intracerebral hemorrhage: Traumatic and spontaneous, arterial hypertension, hemorrhagic stroke, coagulation disorders, aneurysm, vacular malformations, tumors, amyloid angiopathy, angitis, TRAUMA (contusion, laceration contre coup)
o Diffuse axonal injury: high speed injury with stretching or shearing of brain tussie. Petechial hemorrhages in white matter tracts, associated with immediate deep coma, cerebral edema and ICP elevation is common, mortality 30-40%, good outcome 20-30%
- ischemic stroke :
- causes
- CT and MRI characteristics
- evolution in time
o An ischemic stroke happens when the supply of blood to the brain is suddenly interrupted
o A transient ischemic attack (TIA) is a ´mini stroke´. Symptoms are like stroke, but go away within 24 hours. TIA still require emergency treatment
o Stroke kills more women than breast cancer
o Almost 1/5 people who experience a stroke are under 55 years
o Stroke is preventable (think F.A.S.T, act fast!)
o Stroke is a medical emergency (F-ACE, drop of mouth, A-rms, can they lift both arms, S peach, T-ime, is critical
o Cause and mechanism:
1. Thrombotic (occlusive processes in situ), large extra-cranial artery, large intra-cranial artery, small penetrating artery
2. Embolic (particle from somewhere else), cardiac origin or intra-arterial
3. Hypoperfusion (failure of the heart to pump)
o Characteristics: Stroke is marked by rapid development of the clinical symptoms of focal or global loss of brain function.
The symptoms persists for longer than 24. Hours. Images can detect the cause within 15 minutes. Ischemic stroke is characterized by none or minimal tissue damage in the first few hours.
o Time: The acute phase (0-6 hours) is usually marked by symptomatic ischemia turning into infarct as duration increases. MRI and CT will show no leasion if infarction is not present. Non-contrast CT may show a thrombus 🡪 cytotoxic edema 🡪 extracellular edema
o Time: non-contrasted CT permits initiation of intravenous lysis within 3-4.5 hours!
o MRI and CT can determine the extent of hypoperfusion. And MRI register the whole brain in contrast to CT
o Raw image data obtained from CT angiography improve diagnostic investigation of cytotoxic edema to some extent, but diffusion-weightet MRI is the fastest and most reliable method for this condition because it permits investigation of the entire brain in just a few seconds
- Hemorrhagic stroke
Hemorrhagic stroke
o In hemorrhage stroke, bleeding occurs directly into the brain parenchyma. The usual mechanism is thought to be leakage from small intracerebral arteries damaged by chronic hypertension
o The terms intracerebral hemorrhage and hemorrhagic stroke are used interchangeably
o We can classify intracerebral haemorrhage into: location (basal ganglia, thalamic, pontine, cerebellar, lobar hemorrhage) or according etiology (hemorrhagic venous infarct, hypertensive hemorrhage, hemorrhagic transformation of an ischemic infarct)
o Non-contrast CT or MRI is the golden standard in acute hemorrhagic stroke
o It only accounts for about 15 %
o Intracerebral hemorrhage is an subclassification of intracranial
o Se earlier tasks, maybe also subarachnoid hemorrhage
- Tumors of brain and meninges
what do you remember of the others ( not all of these are described in this card)
- meningioma
- Astrocytoma
- Pituitary adenoma
- Acoustic neurinoma
- lipoma
- glioblastoma multiforme (most aggressive primary brain tumour ) probably should mention this one :)
o Introduction: The development of radio imaging techniques for evaluation of brain tumors has progressed significantly in recent years. Two modalities play crucial role: CT and MRI
o X-ray of skull may also detect changes that can lead to suspicion of a tumor in the intracranial space and subsequent examination using CT or MRI
o CT = screening method, MRI = method of choice, DSA = motsly used for determination of blood supply and embolism of hypervascular tumors,
US = intraoperative navigation,
o Detection: is there a mass-lesion?
o Differential diagnosis: is it tumor, abscess, cavernoma, MS-plaque? What kind of tumor?
o Grading
o Preoperative set-up: extension of the lesion?
o Follow-up: is there residual or relapsing tumor?
o Origin: Any systemic cancer can metastasise to the brain, but most common is: Lung, brest, melanoma, colorectal, urogenital cancer
o Primary or metastatic pulmonary cancer – in 90% of patients with brain metastasis
o MR-spectroscopy is the most useful parameter in the diagnosis and differential diagnosis of brain tumors with MRs are the ratio: Cho/Cr, Cho/NAA, NAA/Cr (look at earlier questions for info about MRS)
o Contrast: No enhancement – low grade astrocytoma, diffuse homogenous – meningioma, ring enhancement – metastasis
o Lung adenocarcinoma, Lipoma (hyperintense signal), Glioblastoma (irregular peripheral enhancement), Glioblastoma multiforme, meningioma, paraganglioma, hemangioblastoma, Glomus tumor
o Role of radiology imaging: Detection, Characterization (localization, size, margins, extension, midline shift, compression, contrast enhancement, vascularity, supplying vessels), Differention: benign vs malignant, Staging, Tumor embolization, Surgical planning.. Also intraoperative (surgical navigation, monitoring the effect or treatment)
Most common types: Gliomas (75% astrocytoma) Meningioma Pituitary adenoma Acusticus neurinoma
ASTROCYTOMA Derived from astrocytes – glial cells Divided into diffuse in growth (higher grade) or localized (lower grade) Grading: I: pilcytic astrocytoma II: low-grade astrocytoma III: anaplastic astrocytoma IV: Glioblastoma (multiforme) 🡪 Q 102 most aggressive primary brain tu - diffusely invasive and grows into surrounding regions.
MENINGIOMA
Form from meninges – show growing
“Mother in law sign”: angiography
Enhancement of tu in very early arterial phase and remains well after the venous phase.
The joke is that a mother in law comes early and stays late.
“Dural tail sign”:
result of thickening and enhancement of the dura most often adjacent to a meningioma.
DSA: pre-operative embolization
MRI: isointense to grey matter on T1W, T2W
MRI-CE (Gd): intense and homogenous enhancement (T1W)
- inflammatory diseases of brain and meninges
- meningitis (leptomeningeal enhancement on MRI T1 gd+)
- subdural empyema
- cerebral abscess :(pathogens growing in brain parenchyma, could be hematogenous spread)
- Herpes encephalitis
- MS
MRI is the best for miscellaneous infections ( fungal, bacterial…)
o Bacterial meningitis –
intense leptomeningeal enhancement in cortical sulci. When meningitis is suspected on clinical investigation, the method of choice is cerebrospinal fluid puncture.
-The significance of imaging procedures is that they are used :
- to detect complications like hydrocephalus or encephalitis. In case of acute meningitis, in the early stages one may occasionally observe a significant degree of meningeal absorption of contrast medium on MRI. - post contrast enhancement
A CT investigation is usually negative
o Cerebral abscess –
Smooth thin-walled ring, increased SI on DWI, reduved ADC, MRS: no Cho elevation, but elevated amino acids and lactate in cystic component. In cases of clinically suspected pyemic disease, evidene of cerebral abscess or empyema can be obtained with
MRI or CT. A correlate of cerebral disease in the early stage is cerebritis. MRI is the method of choice with T2-weightet sequences, and with T1 contrast medium.
o Herpes encephalitis:
Mainly affect the limbic system and the temporal region. MRI is golden standard because it sences even small edematous changes in cortex and cerebral medulla.
- T2 Flair : hyperintense
o Subdural abscess:
Rare, inflammatory changes between arachnoidea and dura mater.
- CT izo/hypodense mass with enhancement after contrast.
- MRI – T1W izo, T2W hyper, after contrast variable enhancement
o Epidural empyema:
Extradural inflammation process, on CT mass which enhance and narrow the spinal canal, also vertebral destruction (visible also on x-ray). MRI – at first – T1W hypo/iso, T2W hyper, after contrast diffuse variable enhance. MRI later – it looks like abscess with enhancement of walls
o MS –
involves an immune-mediated process in which an abnormal response of the body´s immune system is directed against the CNS, which is made up of the brain, spinal cord and
optic nerves. Sagittal T2 shows “dawson fingers”. Cause is not clear. Multiple lesions. Diagnosis is established by combo of: T2-weightet MRI (focal changes in cerebral medulla, lesion absorbs contrast medium in T1, involvement of corpus callosum), CSF, clinical.
- degenerative and demyelinating brain diseases
o Cerebral atrophy, parkison´s, Alzheimer´s, Huntington´s
o Cerebral atrophy: cerebral atrophy refers to the progressive loss of brain cells over time
o In these diseases, neuroradiological investigation may be too unspecific in early stages because many diseases such as dementia (e.g alzheimers), parkisons or huntingtons show typical changes only in markedly advanced stages.
Diagnosis imaging procedures are initially important for excluding certain entities (such as a vascular cause).
o Imaging procedures:
The examinations should be bases on MRI, a high-resolution T1- weighted sequence is necessary for this type of data processing. Differentiation from vascular causes – in cases of suspected neurodegenerative diseases – is achieved by T2- weighted imaging, possibly with additional perfusion MRI or MR angiography
o A number of promising new sequences have been developed to detect pathological deposits of specific degradation products in the presence of these diseases (susceptibility-weighted MRI).
o DTI permits in vivo investigation of the nerve fiber network
o Alzheimer´s disease: the cortex is somewhat faded and narrowed in this patient with the neuropsychological diagnosis of Alzheimer
o Also see MS on previous question
- vascular diseases of brain, brain AVMs
o See previous questions about hemorrhage, stroke
o Aneurysms: Cerebral aneurysms develop in the cource of one´s life and are therefore extremely rare in children. 3% of population has aneurysms. A typical manifestation of a bleeding aneurysm is subarachnoid hemorrhage. The risk of a bleeding a. increased in proportion to the size. A fundus diameter < 7 mm in the anterior circulation is considered worthy of treatment only under certain conditions (the risk of hemorrhage per year is markedly below 3%). Mortality rate is 50% after hemorrhage.
o Aneurysms continue: The gold standard is intraarterial DSA, but also MR angiography or CT angiography. MRA and CTA are suitable for screening with proven aneurysm. Localization is typically at the branching sites of vessels, and most commonly found in the anterior communication artery
o AVM: Is a short circuit between the arterial and venous leg of the vascular system, circumventing the capillary bed. It is a rare congenital abnormality and is found in only 0,14 – 1 % of any investigated population. The risk of hemorrhage is low, and intra-parenchymatous or subarachnoid hemorrhage may occur. MRI is golden standard, but CTA or MRA may be additionally used. Managed by intraarterial DSA (interventional treatment), which is also a golden standard still for detection of AVM.
T2-weighted (vessels with low signal intensity
because of rapid transport of stimulated protons).
CT contrast – vessels absorbing the CM 🡪 visualized
o Venous hemangioma (cavernoma): About 4% of investigation populations have a venous malformation, which is a formation of sinusoid vascular spaces or so-called cavernoma. Frequently occurs in number. Are commonly found in cortical aspect of the cerebrum and the pons. May trigger epilepsy and intraparenchymatous bleeding may occur.
imaging:
MRI is golden, and calcifications within the lesion are clearly seen on CT. T2-weighted (may be black and devoid of signals because of inward bleeding and hemosiderin deposits. BUT venous blood signal may be of high signal intensity, and margins black because of hemosiderin deposit)
- Spine and spinal cord imaging techniques
o Introduction:
- The basic investigation is non-contrasted X-rays of individual sections of the spine (posteroanterior and lateral)
- also MRI, CT, scintigraphy and PET serve as additional diagnostic procedures
o X-ray – indications: acute/chronic pain syndromes, post-traumatic and degenerative changes, congenital disorders, MTS, inflammatory diseases
o CT – indications: structural and degenerative changes, congenital disorders, MTS, inflammatory diseases, SPINE
o MRI – indications: Discopathy, degenerative changes, tumor, trauma of soft tissues, inflammatory diseases,
SPINAL CORD
o Generally: MRI is the method of choice for nearly all diseases of the spinal cord. However, CT still is the primary method used to detect and demonstrates with high accuracy pathological changes of bones
- spine and spinal cord
- congenital disorders and varieties
- variant ( deviation) scoliosis ( lateral deviation)
- malformations
- tethered spinal cord syndrome
- spina bifida
o Variant (spine): - This is any deviation from the normal shape, with unimpaired function, and of no pathological significance
o Dysplasia: (spine)
- Congential inferiority of one portion of the skeleton (spondylosis – gap in vertebral arch), (spondylolisthesis – ventral displacement of the vertebra with or without formation of gap)
o Malformations: (spine) Spina bifida occulta (wide vertebral gap covered with connective tissue) and Spina bifida cystica (protrusion of the skin in the region of the sacrum which is caused by lipoma or meninges containing CSF) and spina bifida aperta (large bone defect and displacement of bone marrow, with no covering layer of skin)
o Scoliosis: (spine) may be congenital, lateral distortion of the vertebral column that cannot be compensated structurally
o Hydrosyringomyelia: Limited intramedullary cavity, CSF signal. Typically localized in cervical or thoracical apartment. T2W hypersignal, T1W hyposignal. After contrast doesn´t enhance. On CT just longitudinal cavity
o Tethered spinal cord syndrome: Filum terminale is short and wide, spinal cone ends too low, lipoma in 80%
o Meningocele: Leather covered spinal dysrafizmus – USG, CT, MRI. Composed of CSF and meninges
o Meningomyelocele: Composed of CSF, meninges and nerve tissue
o Lipomyelomeningocele: Composed of CSF, meninges, nerve tissue and fat
o Other: congenital block, hemivertebra, spina bifida oculta, lumbalization of S1
- spine and spinal cord
- traumatic injury
o Introduction: SCI can manifest as a wide varity of clinical syndromes resulting from damage to the spinal cord or its surrounding structures. It can result from minor injury if the spine is weakend from disease such as ankylosing spondylitis or if there is spre-existing spinal stenosis. It may require surgery and it is an emergency
o Pathology: Spinal cord swelling, contusion, edema, intramedullary hemorrhage, transection, extrinsic compression
o Radiology: MRI (T1 and T2 routine axial and saggital imaging, additional T2 gradient echo or DWI wich are more sensitive for hemorrhage)
o Neurological syndromes: Anterior cord syndrome, Brown-Sequard syndrome, cauda equine syndrome, central cord syndrome, conus medullaris syndrome, spinal cord transection
o Evaluation of trauma: Fracture (plain film/CT), Dislocation (plain film/CT), Ligamentous injury (MRI), Cord injury (MRI), Nerve root avulsion (MRI)
o Plain film finding may be very subtle or absent!
o Denis 3 – column classification:
- Anterial column – lig.longitudinale anterior, ventral 2/3 of corpus vertebrae and disc.
- Middle column – posterior 1/3 of corpus vertebrae and disc, lig.longitudinale posterius.
- Posterior column – vertebral arch, articular extenzions, ligamentum flava, interspinous ligament
o Mechanism of spinal injury: Flexion injury, distraction injury, rotation injury
o X-ray – minor surgery
o CT – number 1 for polytrauma
o MRI – suspect spinal cord injury, ligg, epidural hematoma
o Compressive fractures: the most common fractures of corpus vertebrae, wedge-shaped deformation of the body, luxation (loose almost full position)
o Hangman fracture: traumatic spondylolisthesis of the axis, involves the pars interarticularis of C2 on both sides. It is a result of hyperextension and distraction
o Spondylolisthesis means that vertebrae slides anteriorly over the bone underneath
o Jefferson fracture: burst fracture of C1, four-part fracture with double fractures through the anterior and posterior arches
- spine and spinal cord
- tumors
o Introduction:
- MRI!
- Intramedullary = T2W hypersignal, T1W iso/hyposignal, enchanced contrast
- Intradural = T1W, T2W signal like spinal cord, homogenous enhancement also on CT - Extradural = T2W hyper/isosignal, T1W Hyposignal
o Classificitaion of spinal lesions:
- Extradural = outside the thecal sac (including vertebral bone lesion)
- Intradural = within thecal sac, but outside cord
- intramedullary = within cord
o Common extradural lesions:
- Herniated disc
- Benign – osteoblastoma and osteoid osteoma
- Vertebral hemangioma
- Vertebral metastasis (breast, prostate, lung, multiple myeloma)
- Epidural abcess or hematoma
- Synovial cyst
- Nerve sheath tumor (also intradural/extramedullary) – neurofibroma & schwannoma
o Common intradural lesions:
- Nerve sheath tumor (neurofibroma and schwannoma)
- Meningioma
- Drop metastasis
o Common intramedullary lesions:
- Astrocytoma
- Ependymoma
- Hemangioblastoma
- Cavernoma
- Syrinx
- Demyelinated lesion (MS)
- Myelitis
o Vertebral metastasis vs. hemangiomas:
- Hemangiomas = Benign, usually asymptomatic, commonly incidental (bright on T1 and T2 but dark with fat suppression. Enhancement variable)
- Metastases = Dark on T1, Bright on T2 (even with fat suppression. Enchancement) o Extradural: vertebral metastases:
- Diffusely T1-hypotense marrow signal may represent widespread vertebral metastases - This can also be seen in the setting of anemia, myeloproliferative disease, and various other chronic disease states
- spine and spinal cord
- degenerative diseases
- spondylosis deformans
- spondyloarthrosis (intervertebral disc joints)
- osteochondrosis
- discopathy ( bulging, protrusion, hernia)
o X-ray, CT, MRI
o Spondylosis deformans:
- There are osteophytes on the margin of vertebral body
- Clearly on all modalities
o Spondyloarthrosis:
- Degenerative disease of intervertebral joints
- Narrow articular gap and osteophytes on its margins
o Osteochondrosis:
- Reduction and protrusion of the disc
- Osteophytes on margins of vertebral body
- Sclerosis of intervertebral parts of vertebral body and chronical changes in bone marrow
o Discopathy:
- Pathological change of disc
- Water loss, reduction of disc, vacuum phenomenon, fissure in annulus fibrosus and protrusion
- BULGING = circular protrusion
- PROTRUSION = promotion of nucleus pulposus into the annulus fibrosus
- HERNIA = limited protrusion, medial, paramedial, into the formen, out of foramen
- SEKVESTER – separated part of herniated disc
- SCHMORL NODE – intraspongoius hernia
o Spondylolisthesis:
- Non-traumatic shift of vertebral body in saggital plane
- Ventral shift of cranial vertebra
o Retrolisthesis:
- Non-traumatic shift of vertebral body in sagittal plane
- Dorsal shift of cranial vertebrae
- spine and spinal cord
- inflammatory diseases
- ankylosing spondylitis (Bechterew´s disease)
- transverse myelitis
- MS
- Osteomyelitis
- Spondylodiscitis
- acute myelitis
- Epidural empyema
- subdural abscess
o Bechterew´s disease:
- most common inflammatory rheumatic disease of spine
- Causes painful kyphosis and atrophy of sacroiliac joint
- Radiographic signs: kyphosis, syndesmophytes (ossification of intervertebral disc and outer fibers of annulus fibrosus), ankyloses of vertebra, bamboo stick o Pyogenic spondylitis / diskitis with epidural abcess
o Spinal TB (Pott´s disease)
- Prominent bone destruction
- More indolent onset than pyogenic
- Gibbus deformity (form os structural kyphosis, where one or more vertebrae become wedged)
- Involvement of several VB´s
o Transverse myelitis
- Inflames cord of uncertain cause
- Viral infections
- Immune reactions
- Idiopathic
- Myelopathic progressing over hours to weeks
- DDX: MS, glioma, infarction
o Multiple sclerosis:
- Inflammatory demyelination eventually leading to gliosis and axonal loss
- T2-hyperintense lesions in cord parenchyma
- Typicall no cord expansion (vs. tumor); chronic lesion may show atrophy
o Cord edema:
- As in the brain, may be secondary to ischemia (e.g. embolus to spinal artery) or venous hypertension (e.g. AV fistula)
o Osteomyelitis:
- Inflammatory disease of the bone marrow
- X-ray (soft tissue edema, at first irregular bight in spongiosis and then unlimited osteolytic process, periosteal reaction in the acute form. Sekvester, reduction of marrow cavity and sclerosis in the chronal form)
- MRI (edema of bone marrow – T2W hyper)
o Spondylodiscitis:
- Inflammatory dieases of corpus vertebra and disc
- Destruction of the disc and its reduction, uneven surface of vertebral body - Inflammation spreads to soft tissues and to the bone marrow
- MRI – disc and vertebral body edema – T2W, STIR – hyper, reduction of disc and changes in soft tissues. After contrast, it enhances
- X-ray – changes are visible after some weeks and they are not specific
- We can use also CT, but MRI is the best modality
o Acute Myelitis:
- The most common in thoracic apartment
- MRI (T2W – hyper, T1 – iso/hypo)
- After contrast variable enhancement
- Spinal cord could be extended with irregular edges
- If inflammation spreads to meninges- they enhance after contrast
o Epidural empyema:
- Extradural inflammatory process
- CT – enhanced, narrow spinal canal, vertebral destruction
- X – ray – visible vertebral destruction
- MRI – T1W Hypo/iso, T2W hyper (acute) with diffuse variable enhancement - MRI later – it looks like abscess with enhancement of walls
o Subdural abscess:
- Rare
- Inflammatory changes between arachnoidea and dura mater
- On CT (iso/hypodense mass with enhancement after contrast)
- MRI – T1W iso, T2W hyper, after contrast variable enhancement
