Coronal and Axial T1-Weighted MRI Scan Showing Right Hippocampal Sclerosis (Arrow)http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=epi&part=ch3&rendertype=figure&id=ch3.f1
Friday, June 18, 2010
Sagittal and coronal US of a grade 2 hemorrhageBoth lateral ventricles are filled with blood, but there is no ventricular dilatation.
http://www.radiologyassistant.nl/en/440c93be7456f
Anatomic classification :
PVH-IVH can be classified into 4 grades of severity. This classification, which is useful for prognostic reasons when counseling parents and caregivers, is described below. Note that this classification is based on radiological appearance rather than a pathophysiological description of events leading to PVH-IVH.
Grade I - Subependymal region and/or germinal matrix
Grade II - Subependymal hemorrhage with extension into lateral ventricles without ventricular enlargement
Grade III - Subependymal hemorrhage with extension into lateral ventricles with ventricular enlargement
Grade IV - Intraparenchymal hemorrhage
emedicine.medscape.com/article/976654-media
PVH-IVH can be classified into 4 grades of severity. This classification, which is useful for prognostic reasons when counseling parents and caregivers, is described below. Note that this classification is based on radiological appearance rather than a pathophysiological description of events leading to PVH-IVH.
Grade I - Subependymal region and/or germinal matrix
Grade II - Subependymal hemorrhage with extension into lateral ventricles without ventricular enlargement
Grade III - Subependymal hemorrhage with extension into lateral ventricles with ventricular enlargement
Grade IV - Intraparenchymal hemorrhage
emedicine.medscape.com/article/976654-media
Intraventricular hemorrhage (IVH) with periventricular hemorrhagic infarction (PVHI).emedicine.medscape.com/article/976654-media
Severe or grade III hemorrhage (subependymal with significant ventricular enlargement).emedicine.medscape.com/article/976654-media
Sonographic appearance of a normal neonatal brain. Image is from a coronal midline scan.emedicine.medscape.com/article/976654-media
Thursday, June 17, 2010
1-Periventricular leukomalacia (PVL) is the second most common CNS complication in preterm infants, after periventricular hemorrhage.
2-Periventricular leukomalacia is pathologically characterized by the softening of periventricular white matter as a result of vascular ischemia between 26 and 34 weeks of gestation.
Acute stage of periventricular leukomalacia (PVL). Fluid-attenuated inversion recovery (FLAIR) MRI shows bilateral periventricular hyperintensity.
Late-stage periventricular leukomalacia (PVL). Sagittal T1-weighted MRI shows an atrophied, irregular corpus callosum and atrophic brain parenchyma.
2-Periventricular leukomalacia is pathologically characterized by the softening of periventricular white matter as a result of vascular ischemia between 26 and 34 weeks of gestation.
Acute stage of periventricular leukomalacia (PVL). Fluid-attenuated inversion recovery (FLAIR) MRI shows bilateral periventricular hyperintensity.
Late-stage periventricular leukomalacia (PVL). Sagittal T1-weighted MRI shows an atrophied, irregular corpus callosum and atrophic brain parenchyma.Wednesday, June 16, 2010
1. Cingulate gyrus2. Corpus callosum
3. Internal capsule
4. Putamen
5. Anterior thalamic nucleus
6. Amygdala
7. Insula
8. Temporal lobe
9. Caudate nucleus
10. External capsule
11. Claustrum
12. Anterior commissure
13. Medial segment of globus pallidus
14. Infundibulum
15. Column of fornix
16. Optic tract
17. Inferior (temporal) horn of lateral ventricle
18. Lateral ventricle
19. Fornix
http://www.bing.com/search?q=anatomy+of+hippocampus&src=IE-SearchBox&FORM=IE8SRC
Major anatomical boundaries of mesial temporal lobe on coronal MRI. A is the most rostral and H is the most caudal MRI section. Only MRIs displaying critical landmarks are shown. (A) The anterior border of the perirhinal cortex (PC) is located at the level of the limen insulae (LI). (B) The anterior border of the entorhinal cortex (EC) begins on average 2 mm behind the limen insulae. This coincides with the appearance of the temporal stem (TS). (C) Section through the hippocampal head (HH). (D) The posterior border of the EC is located at the posterior limit of the gyrus intralimbicus (GI) and coincides with the anterior border of the hippocampal body (HB). (E) The posterior border of the PC is situated 2 mm caudal to the posterior end of the EC. (F) The rostral border of the posterior parahippocampal cortex (PPC) is situated 1 mm caudal to the posterior end of the PC. (G) The anterior border of the hippocampal tail (HT) coincides with the crus fornix (CF) becoming fully visible. (H) The posterior border of the PPC is situated at the level of the posterior end of the hippocampal tail (HT). AM = amygdala; CS = collateral sulcus; FI = fimbria
hippocampus
It is important for converting short term memory to more permanent memory, and for recalling spatial relationships in the world about us.
The hippocampus consists of the complex interfolded layers of the dentate gyrus (1) and cornu ammonis (2). Their three layered cortex is continuous below with the subiculum (3) which has four, five then six layers as it merges with the parahippocampal gyrus (4).
Diagram of the hippocampal anatomy and adjacent structures in the mesial temporal lobe. The cornu ammonis, a part of the hippocampus, can be divided into four fields: CA1, CA2, CA3, and CA4.http://emedicine.medscape.com/article/342150-overview
hippocampal anatomy
The hippocampus, or intralimbic gyrus, is formed by 2 cortical laminae embedded in each other: the cornu ammonis (CA), also called the hippocampus proper or Ammon horn, and the dentate gyrus. The CA can be divided into regions, or fields, depending on the appearance of pyramidal neurons.
The 4 fields (named by Lorente de No in 1934) are characterized as follows8 :
1-CA1, or the Sommer sector, is the most vulnerable region; it is the most sensitive to hypoxia.
2-CA2 is the most resistant and well-preserved sector.
3-CA3, which enters the concavity of the dentate gyrus, is slightly vulnerable.
4-CA4, sometimes called the endfolium, has intermediate vulnerability to insults.
The following 3 patterns of cell loss are described in the hippocampus:
1-Classic Ammon horn sclerosis - Primary neuronal loss involves CA1 and CA4; occurs less often in C3 and least often in CA2
2-Total Ammon horn sclerosis - Severe neuronal loss in all of the hippocampal zones, CA1 to CA4
3-Endfolium sclerosis - Cell loss restricted to CA4
http://emedicine.medscape.com/article/342150-overview
The 4 fields (named by Lorente de No in 1934) are characterized as follows8 :
1-CA1, or the Sommer sector, is the most vulnerable region; it is the most sensitive to hypoxia.
2-CA2 is the most resistant and well-preserved sector.
3-CA3, which enters the concavity of the dentate gyrus, is slightly vulnerable.
4-CA4, sometimes called the endfolium, has intermediate vulnerability to insults.
The following 3 patterns of cell loss are described in the hippocampus:
1-Classic Ammon horn sclerosis - Primary neuronal loss involves CA1 and CA4; occurs less often in C3 and least often in CA2
2-Total Ammon horn sclerosis - Severe neuronal loss in all of the hippocampal zones, CA1 to CA4
3-Endfolium sclerosis - Cell loss restricted to CA4
http://emedicine.medscape.com/article/342150-overview
Coronal T2-weighted magnetic resonance images demonstrate mesial temporal sclerosis on the right, as well as associated findings of a small right mammillary body and a small right fornix.http://emedicine.medscape.com/article/342150-overview
Mesial Temporal Sclerosis
Fluid-attenuated inversion recovery (FLAIR) magnetic resonance images in a 40-year-old patient with complex partial seizures. The right hippocampus is atrophic and has increased signal intensity that is compatible with mesial temporal sclerosis. Other associated findings of mesial temporal sclerosis are present and are better demonstrated on coronal T2-weighted magnetic resonance images than they are on these images.http://emedicine.medscape.com/article/342150-overview
Temporal Lobe Epilepsy
1-Temporal lobe epilepsy (TLE) was defined in 1985 by the International League Against Epilepsy (ILAE) as a condition characterized by recurrent unprovoked seizures originating from the medial or lateral temporal lobe. The seizures associated with temporal lobe epilepsy consist of simple partial seizures without loss of awareness and complex partial seizures (ie, with loss of awareness). The individual loses awareness during a complex partial seizure because the seizure spreads to involve both temporal lobes, which causes impairment of memory. The partial seizures may secondarily generalize.
2-Although the causes of temporal lobe epilepsy are widely varied, hippocampal sclerosis is the most common pathologic finding. Hippocampal sclerosis involves hippocampal cell loss in the CA1 and CA3 regions and the dentate hilus. The CA2 region is relatively spared. The clinical correlate on neuroimaging on MRI is called mesial temporal lobe sclerosis.
3-The etiologies of temporal lobe epilepsy include the following:
a-Infections, eg, herpes encephalitis, bacterial meningitis, neurocysticercosis
b-Trauma producing contusion or hemorrhage that results in encephalomalacia or cortical scarring; difficult traumatic delivery such as forceps deliveries
c-Malignancies (eg, meningiomas, gliomas, gangliomas)
d-Vascular malformations (ie, arteriovenous malformation, cavernous angioma)
e-Cryptogenic: A cause is presumed but has not been identified.
f-Idiopathic (genetic): This is rare. Familial temporal lobe epilepsy was described by Berkovic and colleagues3 , and partial epilepsy with auditory features was described by Scheffer and colleagues.
4-Hippocampal sclerosis produces a clinical syndrome called mesial temporal lobe epilepsy (MTLE).
http://emedicine.medscape.com/article/1184509-overview
2-Although the causes of temporal lobe epilepsy are widely varied, hippocampal sclerosis is the most common pathologic finding. Hippocampal sclerosis involves hippocampal cell loss in the CA1 and CA3 regions and the dentate hilus. The CA2 region is relatively spared. The clinical correlate on neuroimaging on MRI is called mesial temporal lobe sclerosis.
3-The etiologies of temporal lobe epilepsy include the following:
a-Infections, eg, herpes encephalitis, bacterial meningitis, neurocysticercosis
b-Trauma producing contusion or hemorrhage that results in encephalomalacia or cortical scarring; difficult traumatic delivery such as forceps deliveries
c-Malignancies (eg, meningiomas, gliomas, gangliomas)
d-Vascular malformations (ie, arteriovenous malformation, cavernous angioma)
e-Cryptogenic: A cause is presumed but has not been identified.
f-Idiopathic (genetic): This is rare. Familial temporal lobe epilepsy was described by Berkovic and colleagues3 , and partial epilepsy with auditory features was described by Scheffer and colleagues.
4-Hippocampal sclerosis produces a clinical syndrome called mesial temporal lobe epilepsy (MTLE).
http://emedicine.medscape.com/article/1184509-overview
Tuesday, June 15, 2010
Cavernoma on the left (coronal 3.0 T MRI). (A) IRprep T1 weighted image. (B) T2 weighted FLAIR image. Both acquisitions demonstrate heterogeneous hyperintense signal caused by blood products in different stages of evolution, surrounded by a rim of low signal intensity from haemosiderin. (Click here to magnify the figure)
low grade astrocytoma
Dysembryoplastic neuroepithelial tumour on the left (coronal 3.0 T MRI). (A) T2 weighted FLAIR image. (B) Dual echo late echo image (TE 120). The images show a circumscribed multicystic mass with hyperintense signal in the region of the left amygdala. (Click here to magnify the figure)http://yassermetwally.wordpress.com/epilepsy-and-seizure-disorders/neuroimaging-of-seizure-disorders/
Left hippocampal sclerosis (3.0 T MRI). (A) Inversion recovery prepared (IRprep) T1 weighted acquisition showing an atrophic hippocampus (on right of image: arrow). (B) T2 weighted fluid attenuated inversion recovery (FLAIR) image demonstrating increased T2 weighted signal within the sclerotic hippocampus. (C) Early echo image from dual echo data (TE 30 ms). (D) Later echo image from the same dual echo data (TE 120 ms). Hippocampal T2 relaxation times may be obtained using the data from the dual echo sequence. (Click here to magnify the figure)
Hippocampal sclerosis is characterised by neuronal cell loss and gliosis in CA1, CA3, and dentate hilus subfields of the hippocampus, and can be reliably identified with MRI. The hippocampus is best visualised by acquiring thin slices (1–3 mm) orthogonal to its long axis. The primary MRI features of HS are hippocampal atrophy, demonstrated with coronal T1 weighted images, and increased signal intensity within the hippocampus on T2 weighted images . Additionally, decreased T1 weighted signal intensity and disruption of the internal structure of the hippocampus may be present. Other MRI abnormalities associated with hippocampal damage include atrophy of temporal lobe white matter and cortex, dilatation of the temporal horn, and a blurring of the grey-white border in the temporal neocortex. Atrophy of the amygdala and entorhinal cortex variably accompany hippocampal damage but may also occur in patients with TLE and normal hippocampi. FLAIR images provide an increased contrast between grey and white matter and facilitate differentiation of the amygdala from the hippocampus.
http://yassermetwally.wordpress.com/epilepsy-and-seizure-disorders/neuroimaging-of-seizure-disorders/
http://yassermetwally.wordpress.com/epilepsy-and-seizure-disorders/neuroimaging-of-seizure-disorders/
MRI technique for epilepsy diagnosis:
The sensitivity of MRI for detecting abnormalities depends on the pathological substrate, the MRI techniques applied, and the experience of the interpreting physician. A routine optimal MRI protocol should include T1 and T2 weighted, proton density and fluid attenuated inversion recovery (FLAIR) sequences. These contrasts need to be acquired in at least two orthogonal planes covering the whole brain, using the minimum slice thickness possible. An oblique coronal plane, orientated perpendicular to the long axis of the hippocampus, gives the best definition of medial temporal lobe structures. In general, T1 weighted images give the best definition of the anatomy and differentiate grey and white matter, while T2 weighted images provide high sensitivity for detecting pathology in the brain. A three dimensional T1 weighted volume sequence with a partition size of 1.5 mm or less should be included as these images may be reformatted in any orientation and used for post-acquisition processing such as measuring hippocampal volumes. FLAIR imaging produces heavy T2 weighting and suppresses signal from cerebrospinal fluid (CSF). This provides high lesion contrast in areas close to CSF and enables anatomical detail to be seen with greater conspicuity than with conventional T2 weighted sequences. Gadolinium does not improve the sensitivity of MRI in patients with epilepsy, but may be useful to characterise intracerebral lesions associated with breakdown of the blood–brain barrier.
The sensitivity of MRI for detecting abnormalities depends on the pathological substrate, the MRI techniques applied, and the experience of the interpreting physician. A routine optimal MRI protocol should include T1 and T2 weighted, proton density and fluid attenuated inversion recovery (FLAIR) sequences. These contrasts need to be acquired in at least two orthogonal planes covering the whole brain, using the minimum slice thickness possible. An oblique coronal plane, orientated perpendicular to the long axis of the hippocampus, gives the best definition of medial temporal lobe structures. In general, T1 weighted images give the best definition of the anatomy and differentiate grey and white matter, while T2 weighted images provide high sensitivity for detecting pathology in the brain. A three dimensional T1 weighted volume sequence with a partition size of 1.5 mm or less should be included as these images may be reformatted in any orientation and used for post-acquisition processing such as measuring hippocampal volumes. FLAIR imaging produces heavy T2 weighting and suppresses signal from cerebrospinal fluid (CSF). This provides high lesion contrast in areas close to CSF and enables anatomical detail to be seen with greater conspicuity than with conventional T2 weighted sequences. Gadolinium does not improve the sensitivity of MRI in patients with epilepsy, but may be useful to characterise intracerebral lesions associated with breakdown of the blood–brain barrier.
Monday, June 14, 2010
radiological summary
Magnetic resonance imaging plays a critical role in the diagnosis, management, and follow-up of adult supratentorial neoplasms. However, there is considerable overlap in the imaging findings of these lesions. New imaging methods, such as functional MR imaging, diffusion imaging, and spectroscopy may further improve diagnostic specificity and surgical management. Knowledge of the pathogenesis of these tumors, imaging characteristics, and available novel imaging tools will aid the radiologist in making meaningful contributions in the evaluation and treatment of these lesions.
Intraventricular metastases from lung carcinoma. Axial enhanced Tl-weighted images demonstrate an enhancing mass within the atrium and occipital horn of the right lateral ventricle. Note attachment to the pedicle of the choroid plexus (arrow). (Click to magnify figure)http://yassermetwally.wordpress.com/brain-tumors/adult-brain-tumors/
Metastatic breast carcinoma. A, Axial FLAIR images demonstrate a solitary mass with extensive surrounding edema in the left subinsular region. B, Axial and coronal enhanced Tl -weighted images show ring enhancement. Although the differential for a solitary mass lesion includes primary neoplasms and infectious etiologies, the peripheral location of this lesion, and the disproportionate amount of edema incited by the mass suggest metastatic disease. (Click to magnify figure)http://yassermetwally.wordpress.com/brain-tumors/adult-brain-tumors/
cystic type
Cystic meningioma. A, Axial postcontrast Tl -weighted image reveals a cystic mass lesion involving the left frontal lobe with peripheral enhancement, as well as enhancement around a trapped CSF intensity collection laterally (white arrow). B, Axial postcontrast Tl -weighted image near vertex of the head demonstrates the extra-axial nature of the mass with associated dural attachment (white arrow). (Click to magnify figure)http://yassermetwally.wordpress.com/brain-tumors/adult-brain-tumors/
non glial tumor
Meningioma in a 27-year-old woman who presented with new-onset seizure. A, Axial unenhanced CT image demonstrates a large hyperdense extra-axial mass in the left temporal region with associated central calcification (black arrow) and surrounding edema. B, Axial enhanced CT demonstrates intense homogeneous enhancement. Distinction of intra- versus extra-axial mass by CT can be difficult. C, Axial T2-weighted MR image clearly demonstrates a CSF cleft around the circumference of the tumor (arrowhead) indicating this to be an extra-axial mass. D, Sagittal postcontrast Tl -weighted image demonstrates a dural tail anteriorly and posteriorly along the tentorium (white arrows). (Click to magnify figure)
Lymphoma. A, Axial T2-weighted image shows relatively low signal intensity of the mass indicating high cellularity (black arrow) with surrounding edema high signal intensity B, Postcontrast Tl-weighted image demonstrates marked enhancement of the mass in the right centrum semiovale with surrounding edema. (Click to magnify figure)Secondary CNS lymphoma occurs from spread of systemic disease to the CNS (non- Hodgkin’s more common than Hodgkin’s). Secondary lymphomas typically involve the leptomeninges, and CSF with parenchymal involvement is much less common. MR imaging findings include leptomeningeal/dural enhancement and hydrocephalus.
http://yassermetwally.files.wordpress.com/2008/03/abt11.jpg
(WHO grade IV)
Primitive neuroectodermal tumor (PNET). A, Axial T2-weighted image demonstrates a large hemispheric heterogeneous signal mass with areas of cyst formation (white arrow). Note iso-intense signal of the mass on T2-weighted image reflecting high cellularity. B, Axial Tl -weighted image demonstrates presence of hemorrhage (arrowhead). C, Axial postcontrast Tl -weighted images shows heterogeneous enhancement pattern. (Click to magnify figure)(WHO grade 11)
Oligodendroglioma in an 81-year-old man. A, Axial CT image shows a calcified left frontal lobe mass (white arrowhead). B, Axial T2-weighted image demonstrates heterogeneous T2 signal reflecting the presence of calcifications and some surrounding edema. C, Postcontrast coronal Tl -weighted image shows mild enhancement (long white arrow). Statistically, a calcified mass is still more likely to represent low-grade astrocytoma. (Click to magnify figure)
http://yassermetwally.files.wordpress.com/2008/03/abt9.jpg
Gliomatosis cerebri in a 74-year-old woman. A, Axial T2-weighted, FLAIR, and enhanced Tl -weighted images demonstrate high signal intensity in the right temporal lobe involving white matter and cortex. The acute clinical presentation suggested infarct. B, Diffusion weighted image and TRACE apparent diffusion coefficient (ADC) map demonstrate increased water diffusion in the lesion (slightly higher values on ADC map, outlined by arrowheads), excluding acute infarction. Note that encephalitis may have a similar MR appearance and diffusion characteristics. (Click to magnify figure)
Gliomatosis cerebri. Coronal FLAIR images show diffuse infiltration of the left temporal lobe with gray and white matter involvement (arrowhead). Note the relative lack of mass effect for the degree of infiltration. The white matter infiltration extends across the corpus callosum (white arrow) and involves bilateral deep white matter tracts (double arrow). (Click to magnify figure)http://yassermetwally.wordpress.com/brain-tumors/adult-brain-tumors/
(WHO grade 111)
Anaplastic astrocytoma. Axial T2-weighted, FLAIR, and gradient echo images demonstrate a left frontal opercular mass with a minimal amount of edema. Appearance might suggest low-grade glioma; however, the presence of hemorrhage (white arrow) suggests higher grade. (Click to magnify figure)http://yassermetwally.wordpress.com/brain-tumors/adult-brain-tumors/
Subscribe to:
Comments (Atom)
