Neuroimaging in Epilepsy

Question 1

MRI Epilepsy Protocol includes

Answer 1

multiplanar diffuse
T2 weight
FLAIR
GRE
Susceptibility weighted imagings

3D volumetric T1 weighted acquision and oblique corolonal plane FLAIR and T2 weighted images through the long axis of temporal lobes

Question 2

Epilepsy Surgical Options

Answer 2

Lesionectomy
Corticectomy
Topectomy
corpus callosotomy
hemispherectomy

Question 3

MRI features of Temporal Lobe Epilepsy

Answer 3

MTS

Incomplete hippocampal inversion (best on oblique coronal plane)

Question 4

Best sequences to diagnosis MTS

Answer 4

Oblique coronal temporal high resolution T2 weighted

FLAIR

Question 5

MRI Findings of MTS

Answer 5

PRIMARY FINDINGS

1. Hippocampal atrophy
2. Increased T2 signal
3. Abnormal morphology or loss of internal architecture of hippocampus

SECONDARY FINDINGS:

1. Dilatation of temporal horn of lateral ventricle
2. Loss of gray-white matter
3. Differentiation in the temporal lobe or decreased white matter in adjacent temporal lobe
4. Atrophy of ipsilateral fornix and mammillary body

Question 6

How much % of cases of MTS are bilateral?

Answer 6

10%

Question 7

What sequence is best for performing volumetric analysis?

Answer 7

3D T1WI

Question 8

Neuronal migrational disorders on MRI

Answer 8

High resolution 3D T1 weighted volumetric imaging

Provides superior gray white contrast
Able to see subtle cortical malformations

Question 9

Types of heterotopias

Answer 9

focal
nodular
multifocal (as in TS)
Preferentially involving one hemisphere

Question 10

Subcortical bad heterotopias (SBH)

Answer 10

Periventricular
Bilateral nodular collections of gray matter with smooth margins
*Gives appearance of double cortex

Question 11

Pachygyria

Answer 11

Abnormal tissues in the right location
-Abnormal sulcation and gyration mantel
>8mm thick

Question 12

Polymicrogyria

Answer 12

Two or four layered clortex
<5-7mm
*Commonly associated with HIE, prenatal CMV

Question 13

focal cortical dysplasia

Three categories:

Answer 13

Type I
Type IIa
Type IIb
Type III

Question 14

Type 1 FCD

Answer 14

Subtle blurring of GW junction
Normla cortical thickness
Moderately increased hyperintensities T2/Flair
Decreased signal intensities on T1WI

Question 15

Type IIA

Answer 15

Cortical dysplasias are characterized by:
-blurring of GW junction on T1 or T2/FLAIR
(due to hypomyelination/dysmyelination)
Transmantle sign = increase WM signal changes on T2, WI, FLAIR towards the ventricles
–> Signals radial glial neuronal bands
–> This is what distinguishes FCD and low grade tumors

*More commonly seen in extratemporal, esp in frontal regions

Question 16

Type III FCD

Answer 16

Dual pathology

Associated with hippocamp sclerosis, tumor, vascular malformation

Question 17

Lissencephaly

Answer 17

Smooth brain, abnormal gyration

IF posterior > LIS1 gene
IF anterior > subcortical band heterotopias (XLIS/DCX))

Question 18

Schizencephaly

Answer 18

transcortical cleft extends from ventricles +/- open or fused lip (with polymicrogyria)

Question 19

Hemimegalencephaly

Answer 19

Unilateral hamartomatous excessive growth of all or part of one cerebral hemisphere at different places of embryonic development

Question 20

MRI findings in hemimeg

Answer 20

Enlarged hemisphere 
Increased white matter volume
cortical thickening
Agyria/pachygyria/Polymicrogyria/or lissencephaly
Blurring of GW junction 
Ipsilateral irregular shaped ventricle

Question 21

Brain tumors and incidence with seizures

Answer 21

20-40% with primary brain tumors (adults) experience seizure prior to onset
Another 20-45% will have seizures during course of illness

Question 22

Seizures more common in which tumors?

Answer 22

Slow growing tumors:
Meningiomas, gangliogliomas, DNETs, diffuse low grade tumors (Grade II astrocytomas, oligodendrogliomas, oligoastrocytomas)

Question 23

Most common location for tumors:

Answer 23

temporal >parietal >frontal >occipital

Question 24

Gangliogliomas

1. Where?
2. Path?
3. MRI features

Answer 24

1. Temporal
2. Path: contain mature neural ganglion cells, small mature neoplastic neurons
3. MRI: tumors may show cystic changes or calcifications

Question 25

DNETS | Where?

Answer 25

1. Usually cortical based, benign

Question 26

Meningioma

Answer 26

*Most common extra-axial tumors of CNS | Nonglial neoplasms that originate from arachnoid cap cells of meninges

Question 27

Meningioma | Radiologic features

Answer 27

Isointense on T1 and T2; homogenous enhancement with gad, extra-axial dural tail CSF cleft sign

Question 28

Ganglioglioma | Radiologic features

Answer 28

Cyst with enhancing mural nodule/solid | Calcifications in 50%

Question 29

DNET | Radiologic features

Answer 29

Bubbly cystic appearanc with small cysts within tumor Hyperintense on T2WI Wedge shaped mass which expands the affected gyri and point toward the ventricle Swollen gyrus May be associated with cortical dysplasia

Question 30

Pleiomorphic Xanthoastrocytoma (PXA)

Answer 30

Supratentorial cyst with enhancing mural nodule which abuts the peripheral meninges, peritumoral edema, mild meningeal enhancement

Question 31

Oligodendroglioma

Answer 31

Hypointense on T1, hyperintense on T2, calcification seen as areas of blooming 50% enhance heterogeneously Minimal peritumoral edema

Question 32

Hypothalamic hamartoma

Answer 32

Non-enhancing non-neoplastic congenital gray matter heterotopia in the region of the tuber cinerum of the hypothalamus, which can be sessile or pedunculated

Question 33

Subependymal Giant Cell Astrocytoma (SEGA)

Answer 33

Heterogeneous mass near the foramen of monroe, usually >1 cm; hypo or isointense on T1 and hyperintense on T2 +marked enhancement Other findings of TS: cortical tubers, Subependymal nodules, transmantle sign, nodular ill-defined cystic and band-like lesions seen in the white matter and radial bands

Question 34

Glioblastoma Multiforme

Answer 34

Hypo or isointense on T1, hyperintense on T2, vasogenic edema, susceptibility artifact on T2 from infratumoral lesions due to hemorrhage or rarely calcification "butterfly glioma" when bilateral and cross the corpus callosum -/+ necrosis Peripheral or irregular nodular enhancement No DWI restriction but lower ADC than low grade tumors

Question 35

Metastases

Answer 35

Hypointense on T1 (except melanomas can be hyperintense) Hyperintense on T2 and FLAIR Intense enhancement (ring enhancing, punctate or uniform) Often multiple lesions at diagnosis Vasogenic edema out of proportion to size of lesion, hemorrhage, and necrosis

Question 36

Gangliocytomas and Ganglineurocytoma

Answer 36

``` Gangliocytomas = Mature neural ganglion cells Ganglioneurocytomas = small mature neoplastic neurons MRI = show cystic changes or calcifications ```

Question 37

High flow vascular malformations

Answer 37

AVM

Question 38

Low flow vascular malformation

Answer 38

cerebral cavernous malformations (CCM) Developmental venous anomaly (DVA) Mixed vascular malformation

Question 39

Imaging of cavernous malformations

Answer 39

MRI: Popcorn appearance with hemorrages of different ages*, area of hyperintensity representing methemoglobin surrounded by a hypointense ring of hemosiderin on T2W MRI, GRE helpful CT = bright due to blood pooling within cavernoma

Question 40

Imaging of AVM

Answer 40

MRI > CT Better to appreciate fast flow on T2WI Can see enlarged draining veins MRA to subtract acute hemorrhage components from AVM CTA = demonstrates feeding arteries, nidus, and draining veins *Digital subtraction Angiography for delineating location of vessels

Question 41

MEG Mechanism

Answer 41

MEG sensors are sensitive to magnetic fields that are orthogonal to head surface -Electrical fields that are parallel to the scalp surfaces (specifically generated from sulcal banks) vs EEG with is sensitive to radially oriented electrical fields at crests of gyri.

Question 42

MEG Uses

Answer 42

Identifying spontaneous epileptic activity Localize functional corticies using evoked responses to simple stimuli - Use language tasks: word listening task or reading task -Patient performs simple motor task

Question 43

Objective of magnetic source modeling

Answer 43

Accounts for topography of the magnetic fields measured at a given point in time in the MEG sensors

Question 44

Situations where MEG is helpful

Answer 44

Localizing epileptic pathology in refractory epilepsy or surgical work up Especially in normal MR imaging, large or cystic lesions, or multifocal lesions or rapidly propagated spikes

Question 45

Limitations of MEG

Answer 45

Localizes "irritative zones" not seizure onset zones 20% of patients , no spikes observed in recording Not helpful for looking at networks Not validated for mapping for language networks in anterior temporal or frontal neocortices to guid surgical boundaries.

Question 46

MRI diffuse abnormalities during ICTAL phase of seizure

Answer 46

Primarily found on gray matter Immediately --> increased electrical activity, leading to cellular metabolism and subsquent hyperperfusion No apparent change in microarchitecture. Then as seizure progressied --> vasogenic edema (ADC peak changes) then cytotoxic edema (decrease ADC)