Neuroradiology Flashcards
Myelination begins at what month of life
5th
Continuous throughout life
In a normal infant, myelination appears complete at what MR Sequence
T1
Myelination appears complete on T2 by what month of age
24
Myelination appears complete on FLAIR at what age
40 months
In term neonate, we should see T1 hyperintense myelin in what 3 parts of the brain
Deep cerebellar WM,
dorsal brainstem,
posterior limbs of internal capsules
Genu and splenium of corpus callosum are myelinated by what month of age
6 months
By what age is the appearance of white matter myelination in T1 similar to that of an adult
1 year
INTERHEMISPHERIC FALX become present with broad Sylvian fissure is seen at what fetal age
18 months
INTERHEMISPHERIC FALX = 19 - 1 = 18
More operculization of the Sylvian fissures and calcarine fissures start to form by what fetal age
22 weeks
The calcarine fissure are well formed at what fetal age
26 weeks
The temporal and frontal sulci are formed or forming by what fetal age
30 weeks
What fetal age does all the primary sulci form
34 weeks
Sylvian fissure becomes visible at what GA
16-18
Parieto-occipital fissure becomes visible at what GA
20-22
Calcarine fissure and callosal sulcus becomes visible at what GA
22-23
Central sulcus and cingular sulcus become visible at what GA
24-25
Precentral sulcus become visible by what GA
26 weeks
Post central sulcus and superior temporal sulcus becomes visible at what GA
27 weeks
Superior and inferior frontal sulci are visible at what GA
29 weeks
Inferior temporal sulcus is visible at what GA
33 weeks
All primary sulci and most secondary sulci are present at what GA
34 weeks
In complete agenesis of corpus callosum, the lateral ventricles have a parallel orientation, with posterior dilatation termed _______
Colpocephaly
What midline development abnormality demonstrates upturned anterior horns of lateral ventricle, absence of cingulate sulcus allowing the interhemispheric sulci to extend all the way to the 3rd ventricular margin with underrotation of the hippocampi—- in coronal images
Complete agenesis of corpus callosum
“Texas longhorn” appearance of lateral ventricles in coronal view can be seen in what midline abnormality
Complete agenesis of corpus callosum
Midline abnormality presenting as truncation of the anterior-posterior dimension, that can be segmental, with the callosum appearing as two separate commisures
Partial agenesis or hypogenesis of the corpus callosum
Midline abnormality that is frequently associated with interhemispheric cysts or lipomas
Partial agenesis or hypogenesis of the corpus callosum
Most common cortical development malformation associated with septo-optic dysplasia
Schizencephaly
Consist of optic nerve hypoplasia and partial or complete agenesis of septum pellucidum, dysgenesis of corpus callosum, anomalies of hypothalamic pituitary axis and malformations of cortical development, most notably schizencephaly
Septo-optic dysplasia
Encompasses a spectrum of malformations caused by abnormalities of differentiation and midline cleavage of prosencephalon during the 5th gestational week
Holoprosencephaly
Hallmarks of holoprosencephaly
- Abnormal communication of gray and/or white matter across midline
- facial dysmorphism (hypotelorism, cyclopia, ethmocephaly, cebocephaly, and midline cleft lip/palate
Complete absence of cleavage with anterior displacement of cerebral tissue into a “pancake” configuration and a large monoventricle that expands posteriorly into a dorsal cyst
Alobar holoprosencephaly
Presence of cleavage where some differentiation of posterior lateral ventricles is evident
Semilobar holoprosencephaly
Type or holoprosencephaly where the anterior falx cerebri can be partially present
Lobar holoprosencephaly
Interhemispheric variant of holoprosencephaly where there is lack of separation of the posterior frontal and parietal regions with cleavage of anterior frontal and occipital lobes
Syntelencephaly
Most commonly encountered chiari malformation
1 and 2
Rare chiari malformation, characterized by a cervico-occipital encephalocele containing posterior fossa contents
Chiari 3
Characterized by cerebellar tonsillar protrusion below the foramen magnum in the absence of an open spinal dysraphism or intracranial mass effect
Chiari 1
Degree of tonsillar descent necessary for the diagnosis of chiari 1 (McRae line)
> /= to 5mm below a line drawn from the basion to opisthion
Important finding in chiari malformation as this is the main cause of neurologic symptoms and deficits
Syringomyelia
Surgical treatment for chiari malformation
Posterior fossa decompression with suboccipital craniectomy and C1 laminectomy alone, or with the addition of duraplasty, cerebellar tonsil cautery and CSF shunting
Other associated symptoms in chiari malformation include (5)
- Abnormal morphollogy of cerebellar tonsils
- Dorsal tilt of dens
- Basilar invagination
- Platybasia
- Effacement of CSF spaces at the foramen magnum
Chiari 1 findings with open spinal dysraphism (myeloneningocele or myelocele). It can be identified on prenatal ultrasound by bifrontal concavity of the calvarium (lemon sign) and a flattened cerebellum wraping around the brainstem (banana sign)
Chiari 2
Post natal imaging findings of chiari 2 malformation (7)
- Small posterior cranial fossa with a downward sloping tentorium and herniation of the cerebellar tissue into the cervical canal
- medullary “kink” dorsal to the upper cervical spinal cord
- tectal beaking
- falx insufficiency (interdigitating hemispheric sulci)
- stenogyria
- subependymal gray matter heterotopia
- hypogenesis of corpus callosum
Chiari 2 malformation prenatal repair
Prenatal repair of myelomeningocele
Groupd of posterior fossa malformations includes a number of abnormalities characterized by varying degrees of vermian hypoplasia and malposition in association with posterior fossa cysts
Dandy walker continuum
Triad of complete or partial agenesis of the vermis, cystic dilation of fourth ventricle and an enlarged posterior fossa with upward displacement of tentorium
Classic dandy-walker malformation
Angiographic key finding to the diagnosis of dandy walker malformation
Torcular -lambdoid inversion
The hypoplastic vermis in dandy walker malformation is often rotated counterclockwise such that the tegmento-vermian angle formed by lines drawn along the brainstem and ventral vermis is ____ degrees
> 18 degrees
3 Structures to be checked in dandy walker continuum
Posterior fossa size
Vermis size
T-V angle
Embryonic structure that perforates in the first trimester to form the foramen of Magendie and foramina of Luschka
Blake pouch
Upward displacement of an otherwise normally formed cerebellar vermis
Blake pouch remnant
Blake pouch remnant is considered normal up to what AOG
20 weeks
Believed to be caused by delayed fenestration of blake pouch
Mega cisterna magna
Heterogeneous group of disorders mostly resulting from mutations of genes encoding ciliary proteins
Joubert Syndrome and related disorders
These patients have episodes of irregular breathing during infancy (panting or laughing respirations) with oculomotor apraxia
Joubert syndrome
Classic neuroimaging findings incluse vermian hypoplasia and “molar tooth sign”, where the thickening and elongation of the superior cerebellar peduncles resemble the root of an extracted molar tooth, hypoplasia or absence of lower brainstem nuclei, polydactyly, colobomas and polycystic kidneys
Joubert syndrome
Incomplete separation of the cerebellar hemispheres in association with partial or complete absence of the vermis
Rhombencephalosynapsis
Up to 65% of patients with rhombencephalosynapsis has coexisting _____
Aqueductal stenosis
MR imaging of this entity shows transversely oriented continuous folia and flattened fastigial recess causes by atleast partial absence of cerebellar vermis
Rhombencephalosynapsis
Three components of cortical development malformations
Disturbances of cellular proliferation, cellular migration and/or cortical organization
Most severe manifestation of decreased cellular proliferation in which there is near-complete absence of the sulci and gyri with marked microcephaly
Microlissencephaly
Milder phenotype of microlissencephaly where the brain is smaller than normal, with a reduced number of simple appearing gyri
Microcephaly with simplified gyral pattern
Hamartomatous overgrowrh of part or all of a cerebral hemisphere
Hemimegalencephaly
Appears as paradoxically enlarged lateral ventricle, thickened and ill-defined cortixal ribbon and mineralization and neuronal heterotopia causing “white matter” to appear prematurely myelinated
Hemimegalencephaly
Treatment of choice for hemimegalencephaly
Functional hemispherotomy (surgical disconnection of the entire affected hemisphere)
Leading cause of medically refractory epilepsy in children
Type 2 focal cortical dysplasia
Appears as focal cortical thickening, blurring of the gray-white matter junction, and a funnel-shaped white matter signal abnormality extending fromt he subcortical region toward the ventricle
Type 2 focal cortical dysplasia
Result from the arrest of the radial migration of neurons from the germinal matrix along the walls of the ventricles to the developing cortex during migrational phase. Appears as nodules of tissue that parallel normal gray matter in signal intensity on all pulse sequences
Gray matter heterotopia
A genetically driven migrational arrest that typically appears as smooth symmetric bands of gray matter found between the ventricular surface and cerebral cortex
Band heterotopia
Disorder in which the overlying cortex is either normal or along the lissencephaly/pachygyria spectrum and nearly all affected patients are females
Band heterotopia
Result of arrested neuronal migration resulting in an abnormally thickened cortex and absence of normal gyral-sulcal pattern
Lissencephaly
Complete absence of gyri/sulci, with an “hour-glass” or “figure of 8” appearance due to broad and shallow Sylvian fissures
In its complete form (“classic lissencephaly type 1”) the brain is smooth or agyric with an hourglass shape due to the mild infolding of the sylvian fissures. - brant
Agyria
The gyri are present but abnormally broad, with shallow sulci. Characteristic feature is the cell-sparse zone, a very thin band of white matter signal separating a thin outer cortical layer from a thick inner cortical layer
Pachygyria
Results from abnormalities of late neuronal migration and cortical organization, causing an increased number of abnormally small gyri
Polymicrogyria
Most commonly, polymicrogyria is seen focally if not diffuse in the
Perisylvian
Reflects prevention of neuronal migration from the germinal matrix outward, resulting in transmantle cleft lined by dysplastic gray matter extending from the ependyma to the pial surface
Schizencephaly
Type of schizencephaly where the cortices of the cleft are immediately apposed
Closed lip schizencephaly
Type of schizencephaly where the csf communicates between the ventricle and overlying subarachnoid space
Open lip
Commonly associated with schizencephaly in unilateral cases
Contralateral polymicrogyria
Schizencephaly is commonly bilateral or unilateral
Bilateral in 50% of cases
Extremely preterm
Less than 28 weeks
Very preterm
28-32 weeks
Moderate to late preterm
32-37 weeks
Majority of malformations happens at what AOG
12-24 weeks
A severe in-utero brain injury generally attributes to bilateral internal carotid artery occlusion
Hydranencephaly
SURVIVING brain in infants with hydranencephaly is supplied by the
Posterior circulation or meningeal branches of the external carotid artery
Distinct pattern of white matter injury that affects the developing brain between 24-34 weeks of gestational age, caused by damage to oligodendrocyte progenitor cells. Damage results from hypoxia and ischemia superimposed upon pre-exisiting inflammatory factors
Periventricular leukomalacia
PVL has strong correlation with what etiologies
Maternal infection and placental inflammation
Represents as watershed zone of cerebral blood flow in the immature brain with poor autoregulation
Periventricular white matter
The ability of the brain to mount a reparative response to injury is markedly limited prior to ___ weeks of gestation; as a result there is little or no gliosis
34 weeks
Appearance of PVL in ultrasound
Abnormally hyperechoic injured white matter
MR imaging of PVL will show
Abnormal hyperintensity in the periventricular white matter on T1
Characteristic angular pattern of ventricular expansion becomes manifest in what entity, after cystic changes and break down of cystic walls
PVL
Study of choice to diagnose ischemic injury in infants
MRI
These 2 receptors are overexposed in the developing brain and are concentrated in the thalamic and subthalamic nuclei.
Glutamate and N-methyl-d-aspartate
Nature of Deep nuclear injury
Excitatory neurotoxicity:
During severe hypoxia/ischemic injury, glutamate and NMDA receptors remain open, causing influx of calcium and subsequent neuronal death
Watershed or boarder zones
Between anterior and middle, middle and posterior artery territories
When infants prior to 18 months of age show early hand preference, what brain injury is present
Diffuse and peripheral injury
Hereditary syndromes that are grouped together because they primarily affect structures of ectodermal origin, that is the nervous system and skin
Phakomatoses
Most common of phakomatoses
NF 1
NF 1 is linked to what chromosomal abnormality which codes for neurofibromin
Chromosome 17
Has numerous functions including tumor suppression, myelination, neuronal and astrocytic development. Also has expression in osteoblasts and vascular endothelium
Neurofibromin
Termed as peripheral neurofibromatosis, witg multiple cutaneous lesions (cafe au lait spots, axillary freckling, cutaneous neurofibromas and Lisch nodules)
NF1
Age at presentation of NF1
Childhood
Age at presentation of NF2
Young adult
Optic gliomas, dural ectasia, brain T2 hyperintensities and neurofibromas can be found in what phakomatosis
NF1
Schwannomas and spinal glial tumors are found in what phakomatosis
NF2
Malignant degenaration of nerve sheath tumor and plexiform neurofibromas are seen in what phakomatosis
NF1
Skeletal findings such as scoliosis, sphenoid dysplasia, thinning bone cortex (ribbon ribs) and vascular dysplasia can be found in what phakomatosis
NF1
Brain T2 hyperintensities in NF1 can be found in what 4 areas of the brain.
Basal ganglia,
thalami,
deep cerebral white matter,
cerebellum
Spongiform changes due to abnormal myelin vacuolization in pathology are seen in what phakomatosis
NF1
3 Distinctive bone lesions in NF1
Sphenoid dysplasia,
long bone cortical thickening,
+/- pseudoarthrosis
Fusiform enlargement of the optic nerves with variable enhancement and extension to optic chiasm, and may also spread dorsally into the optic tracts and adjacent brain
Optic pathway gliomas
Most common form of optic gliomas related to NF1
Pilocytic astrocytoma
Phakomatosis that results from mutation of chromosome 22 which affects the tumor suppressor gene merlin aka schwannomin
NF2
Historically names as central neurofibromatosis, which is essentially a multiple neoplasm syndrome with few cutaneous manifestations
NF2
Neurofibromas of NF1 usually found in what nerve roots
Exiting nerve roots
Schwannomas from NF2 are found in what nerve roots
Dorsal nerve roots
Usually has a dumbbell configuration as they pass through the neural foramina, with their medial component impinging upon the spinal cord
Schwannomas
Mnemonic for NF2 MISME stands for
Multiple, inherited, schwannomas, meningiomas, ependymomas
An autosomal dominant disordwr caused by mutations in the TSCI and/or TSC2 genes, which encode for hamartin and tuberin, respectively
Tuberous sclerosis
Syndrome characterized by dysplastic tumor-like lesions in the brain, lungs, skin, kidneys and heart. Epilepsy is present in up to 90% of cases, 50% are cognitively impaired
Tuberous sclerosis
Cutaneous lesions in tuberous sclerosis include
Angiofibromas and depigmented nevi (aka ash-lead spots)
Cortical-subcortical dysplastic lesion; expanded broad polygonal gyri overlying abnormal subcortical white matter can be seen in what phakomatosis
Tuberous sclerosis
Most characteristic brain lesions in patients with tuberous sclerosis are
Subependymal nodules that protrude inward from the outer walls of the lateral ventricles
Subependymal nodules in TS near the caudothalamic groove may develop proliferation of the balloon cells and become what entity
Subependymal giant cell astrocytomas (SEGA)
Benign gliomas of the retina (giant optic drusen or retinal astrocytoma) and giant aneurysms are seen as less common CNS manifestation of what phakomatosis
Tuberous sclerosis
Unlike the classic phakomatoses, this condition is not inherited, but rather a consequence of failure of development of venous structures draining the cerebral cortex, eye, skin
Sturge-Weber syndrome (encephalotrigeminal angiomatosis)
Cutaneous capillary malformation seen in sturge-weber
Port-wine nevus in the face
Primitive venous drainage of the cerebrum is termed
Pial angioma
Eye lesion seen in sturge-weber which can result in glaucoma and exudative retinal detachment
Choroidal hemangioma
An autosomal dominant disorder consisting of retinal, cerebellar and spinal hemangioblastomas. Other features include renal cell carcinoma, pheochromocytoma, cysts in the kidneys, liver and pancreas
Von Hippel-lindau syndrome (CNS angiomatosis)
Develops in 50% of patient with VHL syndrome and altho considered benign neoplasm, they are common source of symptoms and have high post surgical recurrence rate. They are well-circumscribed cystic lesion with an enhancing mural nodule
Hemangioblastomas
The dorsal aspect of the embryo develops a neural plate made up of neural ectoderm, which is continuous on either side with cutaneous ectoderm at what GA
3rd week
In a process called ______, the neural ectoderm folds inward and forms a tube with the center of the tube becoming the ventricles and the central canal of the spinal cord
Neurulation
The complete process of detachment of the neural ectoderm from the adjacent cutaneous ectoderm and then comes together to completely cover the neural tube toward the head happens between what days of gestaton
24-27 days of gestation
The exposed neural tissue if the infolding neural plate fails to detach from the adjacent cutaneous ectoderm and the central canal of the spinal cord communicates with the amniotic sac is called
Neural placode
If the neural placode projects beyond the plane of the back the malformation is called
Myelomeningocele
If the neural placode lays flat relative to the rest of the back it is called a
Myelocele
2 open spinal dysraphisms/spina bifida aperta
Myelomeningocele and myelocele
If the infolding neural plate successfully detaches from the cutaneous ectoderm but mesodermal tissue becomes trapped between the 2 edges, preventing closure of neural tube. The interspersed mesodermal tissue then prevents the normal development of posterior bony elements and differentiates into fat, which is contiguous with the subcutaneous fat and tethers the cord at the site of malformation. The condition is called
Lipomyelomeningocele
If the placode covered with skin and fat does not project beyond the posterior laminar line
Lipomyelocele
If the mesodermal tissue completely separates from the overlying mesoderm, the posterior elements of the bony canal can close, and the result is a
Intradural lipoma
Rarely, the neural tube will successfully separate from the cutaneous ectoderm and close but a defect in the skin will persist, with a tract that descends into the subcutaneous tissues or spinal canal called a
Dorsal dermal sinus
Dorsal dermal sinus may have an inclusion of skin tissue at the base of the tract, consisting of squamous epithelium alone called ______ or multiple skin elements called _____
Epidermoid and dermoid
Characterized by agenesis of a portion of the caudal spine usually in association with spinal cord, anorectal and /or genitourinary anomalies
Caudal regression syndrome or caudal agenesis
High risk for caudal agenesis infants
Diabetic mothers
What group of caudal agenesis patients have a high (L1 or higher) blunted conus with separation of the anterior and posterior nerve roots in a “double-bundle” configuration
Group 1
Group of caudal agenesis patients that has a low-lying tethered cord and may have an additional closed spinal dysraphism such as intradural lipoma or lipomyelomeningocele
Group 2
Its major abnormality is a focal dilatation of the central canal that causes the cord to protrude thru a defect in the dorsal elements
Myelocystocele
Myelocystocele seen in the lumbar or lumbosacral region
Terminal myelocystocele
Myelocystocele seen in cervical or thoracic spine is called
Nonterminal myelocystocele
A streak of cells situated between the ectoderm and endoderm that causes the development of the neural plate and subsequent infolding to form the neural tube
Notochord
If the notochord is divided, 2 separate neural tubes may form, resulting into to hemicords called
Diastematomyelia or split cord malformation
Two hemicords that have their own dural sac, separated by a bony spur
Type 1 spinal cord malformation
2 hemicords in 1 dural sac
Type 2 spinal cord malformation
Clinical diagnosis based upon the constellation of pain, gait abnormalities, sensory disturbances and/or lower extremity weakness, in association with a structural abnormality of the distal cord that could be a cause of increased tension or restricted mobility of the conus medullaris
Tethered cord syndrome
Term used to describe a cystic cavity within the spinal cord, usually representing the dilated central canal. It is analogous to hydrocephalus in the brain, in that there is enlargement of a space normally occupied by CSF
Syringe, syringomyelia or syrinx
Most syrinxes are the result of congenital hindbrain malformations such as
Chiari 1 and 2
Normal central canal has a diameter of up to
3mm
Scoliosis is most frequently seen in what gender
Female
Scoliosis typically presents with a primary thoracolumbar curve convex to the
Right
Defined as any lateral spinal curvature of >10 degrees
Scoliosis
Common causes of nonidiopathic scoliosis
Vertebral anomalies such as hemivertebrae or neural anomalies such as SCM or syrinx
