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74 Cards in this Set
- Front
- Back
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When looking at pediatric brain structure what is the recommended technique
(4 steps) |
midline structures (sagital) in T1
White Matter (Axial) T1 and T2 Cortex (Axial) T1 and T2) Deep grey nuclei (Axial) T1 and T2) |
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What structures should be analyszed when looking at the midline sagital image
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corpus callosum (agenesis)
hypothalamus (hamartoma) brain stem vermis |
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Why is important to know the conceptional age when analyzing a neonate
What is the white matter in T1 and T2 relative to the grey matter (cortex) in a normal myelinated brain |
the brains are judged based of this date not the age since birth
T1 white matter is white T2 white matter is dark |
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When does myelination begin
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before birth
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What is the direction of myelination of the brain
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caudal to cephalad
dorsal to ventral |
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What pathways does myelination occur first
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more primitive pathways such as sensory and motor pathways
(before higher pathways like association) |
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What part of the brain does myelination occur last
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frontal lobe (ventral/cephalad) this is the part of the brain where association and cognitive function take place
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When do changes 2ndary to myelination take place first; t1 or T2
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T1 (by 8 months) therefore T1 is more sensitive early on
T2 (by 2y) |
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What is the appearance of a 28wk premature brain on MR
How stages of sulci development are there? |
primary sulci are present, white matter is unmyelinated (no grey white differentiation)
3; primary, secondary and tertiary (adult) sulci |
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What are primary sulci
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these occur prior to secondary and tertiary (adult) sulci and are broad sulci without many wrinkles
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What does the white matter compared to the cortex look like on a T2 image in an unmyelinated brain
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bright compared to darker cortex (WM is unmyelinated)
NOTE: a mature myelinated brain will have white matter which is darker than the grey matter in T2 MR, however, prior to myelination this is opposite (White matter is white) |
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What becomes myelinated the white or grey matter
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white
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What does the WM look like compared to the cortex on a T1 image prior to myelination
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dark relative the brighter cortex
NOTE: a mature myelinated brain will have brighter WM than the Grey matter (cortex) in a T1 image |
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What happens to white matter in both T1 and T2 images compared to cortex when it is unmyelinated
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white matter is darker on T1
white matter is brighter on T2 |
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What happens to the white matter when it becomes myelinated on T1 images
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it will become brighter
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Does a neonate have a bright or darker corpus callosum compared to grey matter on T1 (after myelination)
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it will be brighter bc it has myelinated
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What happens to the WM tracts on T2 images
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it will cause them to become darker
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When a T1 images shows evidence of myelination (corpus callosum becoming brighter) do you expect to see corresponding increase in darkness in a T2 image
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It depends on the age. But generally no. It takes longer for this occur (up to 2 years). There will be a time when the T1 and T2 are both bright
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What is the last part of the brain to show myelination of the white matter tracts
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anterior frontal
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What are findings of agenesis of the corpus callosum on mid-sagital images?
5 What findings of the lateral ventricles |
absence of the corpus callosum, gyri which radiate to a high riding 3rd ventricle, absent cingulate gyrus, prominent occipital horns
Colpocephaly: is a descriptive term where there is disproportionate prominence of the occipital horns of the lateral ventricles |
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How does the cingulate gyrus look during ACC?
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everted (normally inverted..whatever that means)
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Why do children wih ACC have increased size of the lateral ventricles
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because of decrease volume of the white matter
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What are clinical SS of hydrocephalus
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bulging fontanelle, increased head size
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Do children with agenesis of corpus callosum usually have hydrocephalus
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technically no, they have decreased volume of the WM and this is not the same as hydro (but look for clinical SS to r/o)
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What is the direction of development of the corpus callosum
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front to back
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Is it possible to hypogenesis of the corpus callosum
What part of the corpus callosum is usually absent? |
yes
since the anterior part of the corpus callosum develops first this is usuallly abscence of the posterior portion |
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Where are the midline locations of lipomas
5 |
interehemispheric fissure
supracerebellar cistern quadrigeminal plate cerebellopontine angle sylvian cistern |
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How do you determine if a mass is a lipoma
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if it is fat suppressed
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Where is the most common location of an lipoma
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interhemispheric fissure
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Are lipomas in the interhemispheric fissure associated with callosal hypogenesis or callosal agenesis
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yes
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Is the quadrigeminal cistern anterior or posterior to the brainstem
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posterior (superior to the cerebellum)
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What other pathology can a lipoma be mistaken for
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a dermoid
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How is a dermoid differntiated from a lipoma
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a lipoma will have complete suppression on fat saturated images while dermoid fat saturation is only partial
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Are lipomas hyperintense on T1 weighted images
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yes
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What is the signal intensity of a hypothalamic hamartoma
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isointense to gray matter
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Does a hypothalamic hamartoma enhance
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no
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What are two clinical associations to hypothalamic hamartomas
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precocious puberty and sz
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What are 3 midline sagital abnomalities that can be found in children
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lipoma
agenesis of corpus callosum hypothalamic hamartoma |
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Where do neurons originate from
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the germinal matrix
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Where is the germinal matrix located
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lines the ventricles
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What are the 3 steps of neuron development for the cortical brain
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generation (germinal matrix)
migration organization or cortex |
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What is lissencephaly
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when there is agyria/ or pachygria (if incomplete lissencephaly), with band surrounding the periphery of the brain which is dark on T2 (arrested migration of neurons), and a more distal band which is bright on T2 (cell sparse zone).
It a subset of disorders of cortical formation , which results in a smooth cortical surface lacking the normal gyral convolutions. |
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What is agyria
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lack of formation of sulci and gyri (occurs during lissencephaly)
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What is the area of bright T2 signal that is periperal to the band of arrested neurons in a lissencephally brain
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this is the cell sparse zone (bright on T2
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What is the signal intensity of the arrested band of neurons and the cell sparse area
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band of arrested cells is dark on T2
cell sparse area is bright on T2 |
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What does incomplete classical lissencephaly look like
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pachygyria (broad and too few gyri, thickened cortex)
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What is pachygyria
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broad and too few gyri, thickened cortex
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What is band heterotopia
What is another name for band heterotopia |
band of neurons located in white matter and seperated from the cortex by myelinated white matter
double cortex |
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What is the signal characteristic of the band in band heterotopia
What causes band heterotopia |
gray matter signal characteristics
It results from arrested migration of neurons, such that they form a grey matter layer within the centrum semiovale or subcortical white matter. |
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What is more sensitive for myelination before 1 years of age
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T1 weighted images is the most sensitive in children less than 1 year of age
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What is more sensitive for myelination for pt 1- 2 years
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T2 weighted images is the most sensitive in children between the age of 1 and 2 demonstrating gradual shift from hyer- to hypo-intense relative to grey matter. The only area to remain hyperintense after the age of 2 years, and often for quite some time, is the peritrigonal region
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What is the normal white matter signal in adult on T2
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hypointense (dark) to grey matter
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What is the abnormal band in band heterotopia on T2
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gray matter characteristics ( bright compared to whithe matter) on T2
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Is the band in band heterotopia have grey matter characteristics
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yes, bright to wm in T2 and dark to wm on T1 images
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Once cells migrate to the cortex what has to happen
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they must organize to form the six layer neocortex
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What is polymicrogyria
What are the findings in polymicrogyria |
is one of many malformations of cortical development, and along with grey matter heterotopias, falls under a bewildering group of conditions characterised by abnormalities both in migration of neurons to the cortex and abnormal cortical organization.
this is a deep sylvian fissure with thickened gyrus |
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Where do you check for polymicrogyria
What causes polymicrogyria to occur |
the sagittal images (look in for a thickened limb of the slyvian/perisylvian fissure)
genetic, sporadic, after congenital CMV infection |
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What are two causes of abnormalities of the layers of cortesx
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complete disorganization
abscence of a layer |
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What does polymicrogyria look like
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thick cortex ( signal characteristics similar to normal grey matter) around the sylvian fissure
NOTE: this is not thickened cortex it is simply multiple small gyri |
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What are 3 clinical signs and symptoms of polymicrogyria
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sz, focal deficit, developmental delay
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Can polymicrogyria be unilateral
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yes, unilateral or bilateral (60%)
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What happens to the sylvian fissure in polymicrogyria
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it becomes abnormally deep
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What is the measurement of a thick cortex surrounding the sylvian fissure in a polymicrogyria
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5mm
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What is the abnormality in polymicrogyria
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The numerous small gyri that lend their name to the condition are very small and only seen on thin section high resolution MRI, and even then may be difficult to distinguish from pachygyria, as both as associated with broad enlarged and often thickened gyri.
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If you see calcification in the brain e with thickened sylvian fissure gyri what should you suspect
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Congenital CMV with polymicorgyria
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What congenital infection is polymicrogyria associated with
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cmv
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Can CMV cause white matter disease also
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yes, look for areas of abnormal signal in T1 and T2
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What is periventricular nodular heterotopia
What is another name for periventricular nodular heterotopia |
the migration problem that results in periventricular nodules. Small nodules of grey matter are seen immediately deep to the ependymal layer, elevating it and distorting the outlines of the ventricles.
Subependymal heteropic grey matter |
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What are the MR characteristics of periventricular nodules heterotopia
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isointense to cortex in T1 and T2, nonenhancing, smooth.
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Do the nodules of periventricular nodule heterotopia enhance
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no
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Can the nodules of periventricular hetertopia project into the lateral ventricles
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yes
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Where is the location of periventricular nodular heterotopia
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parallel to ventricles or protruding into the ventricles
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What is the symptoms of periventricular nodular heterotopia
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asymptomatic or sz/ developmental delay
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What is schizencephaly
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a rare cortical malformation that manifests as a grey matter-lined cleft extending from the ependyma to the pia mater.
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