Neuro Flashcards
1
Q
Diagnosis?
What is this condition?
Associated abnormalities?
A
Chiari 1. Caudal extension of the cerebellar tonsils 5 mm below the foramen magnum. Syringomyelia seen in 50%.
Associated with: shortening of the clivus, basilar invagination, C1 assimilation, and fused cervical vertebrae (Klipper-Feil syndrome).
2
Q
What is a Chiari II malformation?
A
Congenital malformation of the spine and posterior fossa characterised by lumbosacral spina bifida aperta / myelomeningocoele (90%) and a small posterior fossa with descent of the brain stem. Numerous associated abnormalities are also frequently encountered
Skull: lacunar skull, concave clivus, low-riding torcula, wide foramen magnum and upper cervical canal.
Dura: fenestrated falx causing interdigitating sulci, heart-shaped incisura, hypoplastic cerebellar tentorium.
Posterior fossa: towering cerebellum, downward vermian displacement, slitlike 4th ventricle, tectal beaking, wrapping of cerebellum around brainstem, medullary kink.
Also: Dysgenesis of the corpus callosum (85%), hydrocephalus (75%), syringomyelia (50%), aqueductal stenosis (50%), holoprosencephaly, tethered cord.
3
Q
Difference between Chiari II and III?
A
II- myelomeningocele
III- encephalocele
4
Q
What is the Dandy-Walker continuum?
How is it different than mega cisterna magna?
And arachnoid cyst?
A
Hish insertion of the tentorium and cystic dilation of the 4th ventricle (fills nearly entire posterior fossa), enlarged posterior fossa, varying degrees of cerebellar vermis agenesis or hypogenesis.
Mega cisterna magna- enlargement of the cisterna magna and posterior fossa without abnormality in the 4th ventricle or vermis.
Arachnoid cyst- 4th ventricle and vermis are normal but displaced by the cyst.
5
Q
What is cerebellar hypoplasia?
A
Hypogenesis of the cerebellar vermis and cystic dilation of the 4th ventricle without posterior fossa enlargement… formerly known as Dandy-Walker variant.
6
Q
Abnormalities associated with Dandy-Walker?
A
Agenesis of the corpus callosum, migration anomalies, cephalocele (outward herniation of CNS through cranial defect), holoprosencephaly (result of incomplete separation of the two hemispheres), hydrocephalus, porencephaly.
(Dandy-Walker- cystic dilation 4th ventricle, enlarged posterior fossa, high position of the tentorium, cerebellar agenesis/hypogenesis).
7
Q
Diagnosis?
Imaging findings?
A
Dysgenesis of the corpus callosum- partial or complete absence of the corpus callosum.
High-riding 3rd ventricle, Bundles of Probst (tracks of white matter that run parallel to the ventricle as an alternative to the CC- thats why the lateral ventricles are farther apart), “bullhorn” appearance of the frontal horns, absent cingulate sulcus, absence of the septum pellucidum or severe widening of the cavum septum pellucidum, enlarged occipital horns (colpocephaly).
Associated with otehr CNS anomalies.
8
Q
Diagnosis?
Imaging findings on CT and MR?
A
Canavan disease.
CT: diffuse low attenuation in cerebral and cerebellar white matter.
MRI: High T2 and low T1 in the white matter. Predominantly affects the sub-cortical U fibers, worst in the occipital lobes, then frontal/parietal. Thalami and basal ganglia affected in severe cases. Relative sparing of the internal capsule. MRS: may have increased NAA peak.
9
Q
Population affected by Canavan disease?
Cause?
Symptoms?
A
Autosomal-recessive condition, most common in Ashkenazi Jews.
Deficiency of aspartoacylase.
Hypotonia, macrocephaly, and seizures as a newborn. Progresses to spasticity, optic atrophy, and intellectual failure. Death by 2.
10
Q
Canavan disease vs Krabbe disease and metachromatic leukodystrophy?
A
Canavan disease- affects peripheral white matter first.
Krabbe/metachromatic leukodystrophy- involve deep white matter early, peripheral white matter as the disease progresses.
11
Q
Diagnosis?
A
Chiari III.
12
Q
Diagnosis?
A
Chiari II.
Findings on antenatal ultrasound: banana cerebellum sign, lemon sign.
13
Q
Diagnosis?
A
Dandy-Walker.
14
Q
Brain MRI- differential diagnosis for high T1 lesions?
A
Hemorrhage (early subacute, late subacute), lesions with a high protein content, melanin, lipids (fat/lipoma), minerals (manganesium), slow flow.
15
Q
Intracranial lipoma - imaging characteristics?
Locations?
Associated lesions?
A
Signal like fat, saturate out with fat sat. No contrast enhancement. Can calcify. Frequently associated with abnormal development of adjacent structures.
Locations- intrahemispheric (aka pericallosal, most common, 50% associated with disgenesis of corpus callosum), suprasellar, quadrigeminal cistern, CPA.
Pericallosal lesions divided into tubulonodular (bulky) and curvilinear (ribbon-like).
Lipomas are also associated with cephaloceles.
16
Q
Diagnosis?
A
Cerebellopontine angle lipoma. The facial and vestibulocochlear nerve often course through lipomas in this location.
Other locations: pericallosal, suprasellar, quadrigeminal plate.
17
Q
Diagnosis?
A
Lissencephaly type 1.
18
Q
Lissencephaly type 1 (classic):
Imaging features?
Presentation?
Syndrome association?
A
Imaging- brain has few shallow sulci and shallow Sylvian fissures, “hour glass” appearance. Smooth, thickened cortex (4 layers, normal is 6), may have subcortical band heterotopia.
Presentation- Marked hypotonia and paucity of movements, difficulty feeding. Develop microcephaly (normal at birth). Seizures.
May be isolated or part of a syndrome, most commonly Miller-Dieker syndrome.
19
Q
How long can the cortex of the brain appear smooth in normal fetuses?
A
Until 26 weeks.
20
Q
Diagnosis?
A
Supependymal (periventricular) grey matter heterotopia.
21
Q
What are the three types of grey matter heterotopia?
A
1) Subependymal. Along the ventricles. Normal development.
2) Focal subcortical. Causes motor and intellectual distrubance.
3) Band (laminar). Considered a mild form of classic lissencephaly, between cortex and lat ventricles, separated from both by layer of white matter. Variable developmental delay, more common in females.
All associated with seizures. Due to arrest of the radial migration of neurons. Masses that are isointense to grey matter on all sequences.
22
Q
Imaging features of subcortical grey matter heterotopia?
A
Continuous with the overlying cortex or underlying ventricle.
Are associated with severe abnormalities of the involved hemisphere: diffuse reduction in size of the hemisphere, distorted ventricles, diminished and abnormal white matter, thinned overlying cortex with shallow sulci, distorted basal ganglia.
23
Q
What is schizencephaly? What are the types?
A
An anomaly of neuronal migration in which a CSF-filled cleft is lined by gray matter. It extends from the ventricular surface to the periphery (pial surface) of the brain.
Type 1- Closed lip schizencephaly. Cleft walls in apposition, with a ventricular dimple.
Type 2- open lip schizencephaly. Cleft walls separated (more common).
24
Q
Diagnosis?
A
Open-lip (type 2) schizencephaly. This is the more common type.
25
Diagnosis?
Closed lip (type 1) schizencephaly.
26
Anomalies associated with schizencephaly?
(CSF cleft, lined by gray matter)
Polymicrogyria outside the cleft, white matter volume loss, septal and optic anomalies, callosal anomalies, and hippocampal anomalies.
Can see sub-ependymal heterotopia at the cleft.
27
Diagnosis?
Imaging findings?
**Alobar holoprosencephaly.** This is the most severe form of holoprosencephaly, is a congenital malformation of the forebrain- defect in dorsoventral patterning and cleavage.
Imaging findings: **absent corpus callosum and falx**, dorsal cyst with hydrocephalus (monoventricle), macrocephaly, anterior brain compressed anteriorly (variable amounts of residual cortex), **fused thalami**. Can see azygous anterior cerebral artery.
**Associated facial features**: cleft lip/palate, hypotelorism, arhinencephaly (congenital absence of olfactory bulbs), cyclopia.
28
What is hydranencephaly?
How is it different than alobar holoprosencephaly?
Hydranencephaly: intrauterine destruction of the cerebral hemispheres secondary to occlusion of the internal carotid arteries.
In hydranencephaly, the thalami are not fused and the cerebral falx is intact.
29
Diagnosis?
Hydranencephaly (not alobar holoprosencephaly because the falx is present).
30
What is lobar holoprosencephaly?
Imaging features?
Congenital brain malformation, failure of complete separation of the two hemispheres and failure of transverse cleavage into diencephalon and telencephalon.
Imaging findings: **cerebral hemispheres are present** (unlike in alobar and semilobar), fusion of the frontal horns of the lateral ventricles w/ wide communication with the 3rd ventricle, fusion of the fornices, **absence of the septum pellucidum**, agenesis or hypoplasia of the corpus callosum, falx is present, interhemispheric fissure fully formed, **thalami not fused**.
31
Diagnosis?
Lobar holoprosencephaly.
32
Imaging findings of semi-lobar holoprosencephaly?
The **basic structure of the cerebral lobes are present**, **but are fused** most commonly anteriorly and at the thalami. There is partial diverticulation of brain (dorsal cyst).
Absence of septum pellucidum, **monoventricle with partially developed occipital and temporal horns,** rudimentary falx cerebri (absent anteriorly), **incompletely formed interhemispheric fissure,** partial or complete fusion of the thalami, absent olfactory tracts and bulbs, agenesis or hypoplasia of the corpus callosum, incomplete hippocampal formation.
Associated with mild degree of facial abnormality such as hypotelorismand cleft lip.
33
Diagnosis?
Semi-lobar holoprosencephaly.
34
What is septo-optic dysplasia?
Imaging findings?
The mildest form of holoprosencephaly, caused by **dysgenesis of the septum pellucidum**.
**Look for:** Optic nerve hypoplasia, hypothalamic and pituitary dysfunction, scizencephaly (50%), thin corpus callosum, square frontal horns. Rarely see midline defects.
Main differentiating factor between septo-optic dysplasia and lobar holoprosencephaly is the 2 separate horns of the anterior fonix in SOD (fused in lobar).
35
What is neurofibromatosis type 1 (aka von Recklinghausen disease)?
Clinical presentation/findings?
The most common phakomatosis- AD or spontaneous mutation (50/50). Chromosome 17.
Associated with dural ectasia and lateral meningoceles.
Skin findings (**cafe au lait spots**), 2 or more **neurofibromas** (benign peripheral nerve sheath tumor) or **1** **plexiform neurofibroma** (infiltrative pattern, "bag of worms," often subQ), **optic nerve glioma** (30%), osseous dysplasias (scoliosis, posterior scalloping of vertebral bodies), sphenoid wing dysplasia, iris hamartomas (Lisch nodules).
Increased risk of malignancies- pheochromocytoma, malignant peripheral nerve sheath tumor, Wilms, renal AML, +.
36
CT and MRI features of neurofibromas? Plexiform neurofibromas?
What other findings can you see in the brain with NF1 patients?
CT- well defined hypodense mass. Minimal enhancement.
MRI- T1 hypointense, T2 hyper. "Target sign" may be seen- hyperintense rim and central low signal. Heterogenous enhancement.
Plexiform neurofibromas appear on CT and MRI as large multilobulated and conglomerated masses extending along nerves and nerve branches
In NF1- can get "focal areas of signal intensity" (FASI) in the basal ganglia, thalami, cerebellum, and subcortical white matter. T1 and T2 bright, no mass effect or enhancement. Optic nerve gliomas.
37
Diagnosis?
Differential?
Dural ectasia- ballooning or widening of the dural sac, associated with herniation of nerve root sleeves. Increased incidence of anterior sacral meningoceles.
Differential- Marfan syndrome (in 60 - 90% of patients), neurofibromatosis type 1, Ehlers-Danlos syndrome, ankylosing spondylitis, osteogenesis imperfecta, trauma, post surgery, tumors, scoliosis
38
What are the areas of involvement in neurofibromatosis type 2?
Intracranial: **Bilateral vestibular schwannomas; multiple meningiomas;** calcifications of the choroid plexus, cerebellar cortex, and occasionally cerebral cortex.
Spinal: cord **ependymomas**, multiple **schwannomas** of exiting nerve roots, meningiomas.
Cutaneous manifestations less common than in NF1.
Note: both 1&2 have masses in the spine, but in 1 they are neurofibromas and in 2 they are schwannomas. No neurofibromas in 2.
Autosomal dominant- chromosome 22q11 defect.
39
Diagnosis?
Probably neurofibromatosis type 2 (bilateral vestibular schwannomas).
Look for: multiple meningiomas, spinal cord ependymomas, schwannomas.
40
What is tuberous sclerosis complex?
What intracranial abnormalities are seen?
A phakomatosis, characterized by multiple benign tumors in the embryonal ectoderm. Majority spontaneous mutations, but can be AD.
**Cortical and subcortical tubers-** dystrophic neurons. Areas of high signal on T2/flair images, rarely enhance. 90% cerebral, usually frontal lobe. PET can identify epileptogenic tubers (very hypometabolic).
**Subependymal nodules**- (hamartomas) seen in the walls of the lateral ventricles. Can calcify, may enhance. Malignant degeneration to subependymal **giant cell astrocytoma** in 10-15% (enhancing mass in lateral ventricle).
**Radial bands.**
41
What non-neuro abnormalities are seen with tuberous sclerosis?
Seizures, mental retardation (50%).
Adenoma sebaceum (angiofibromas- red papules on face).
Thorax: Rhabdomyoma of the heart (regress spontaneously), lymphangiomyomatosis.
Abdominal: renal AMLs (50%+), renal cysts (gene affected next to ADPKD1 gene), RCC & oncocytoma, retroperitoneal LAM.
42
Diagnosis?
Tuberous sclerosis (multiple subependymal nodules and cortical/subcortical tubers seen). Watch out for giant cell astrocytoma.
43
What is Sturge-Weber syndrome?
Characteristic features?
A spontaneous phakomatosis.
**Port wine stain** (cutaneous hemangioma, usually V1 distribution of trigeminal nerve and ipsilateral to intracranial abnormality, 95%).
**Leptomeningeal hemangioma-** results in a vascular steal affecting the subjacent cortex and white matter producing localized ischemia. See: leptomeningeal enhancement, abnormal (dilated) deep venous drainage, enlarged ipsilateral choroid plexus (due to recruitment of veins for drainage). Get atrophy of affected hemisphere and tram-track cortical calcifications due to chronic ischemia. Thickened calvarium.
44
Diagnosis?
Presenting symptoms?
Sturge-Weber.
Seizures, developmental delay, and hemispheric symptoms (hemiplegia, hemiparesis, and/or hemianopsia).
45
What is Von Hippel-Lindau?
What are the associated abnormalities?
Characterized by the development of numerous benign and malignant tumors. Autosomal dominant, inactivation of a tumor suppressor gene on chromosome 3. AKA hemangioblastomatosis.
**CNS Hemangioblastomas**: cerebellar (75%), spinal cord, brainstem, retina. Frequently appear _cystic with a mural enhancing nodule, no surrounding edema_, flow voids from feeding arteries but no AV shunting.
Choroid plexus papilloma.
**RCC** (usually _clear cell_ type, occur younger). Renal AMLs.
**Pheochromocytoma(s).**
Pancreatic cysts, **pancreatic islet cell tumours**, microcystic adenoma(s) of pancreas, pancreatic adenocarcinoma (rare).
Liver cysts.
**Papillary cystadenoma(s) of the epididymis.**
46
Diagnosis?
**Hemangioblastoma:** cystic with a mural nodule, no surrounding edema. When intracranial, 95% in posterior fossa- can also be seen in kidneys, liver, pancreas.
Tumor of vascular origin; can be sporadic or in a patient with Von Hippel-Lindau.Dense tumor blush on angio.
47
What is a ventriculus terminalis?
An anatomical variant: a small, ependymal-lined, oval, cystic structure positioned at the transition from the tip of the conus medullaris to the origin of the filum terminale. Regresses in size during the first weeks after birth.
Seen as a cystic structure at the tip of the conus medullaris, extending over 8 - 10 mm and with a transverse diameter of 2 - 4 mm. (don't confuse with syringohydromyelia)
48
Diagnosis?
Types?
Associated abnormalities?
**Diastematomyelia** (split cord malformation).
**Type 1** - (25%) with a bony septum, resulting in separate dural tubes, each containing a hemicord. **Type 2** - (75%) no bony septum (may be fibrous), one thecal sac contains both hemicords.
**Intersegmental laminar fusion** is pathognomonic. **Congenital scoliosis** (80%), **tethered cord** (75%), cutaneous birthmarks overlie defect (50%).
49
Diagnosis?
Associated abnormality?
**Lipomyelocele** (vs lipomyelomeningocele, where the placode-lipoma interface is outside the spinal canal, not in).
Tethered cord in 100% (if dorsal myelomeningocele is associated with a tethered cord, look for a lipoma). Also see sacral dysraphism.
50
Imaging features of an oligodendroglioma?
Differential diagnosis?
**CT:** hypo to isodense mass, in the cortex or subcortical white matter. 90% supratentorial. Vasogenic edema uncommon. Often have coarse calcifications (most common intracranial tumor to have calcifications, calcs more common in higher grade "anaplastic").
**MRI:** heterogeneous signal. T1 hypointense, T2 hyperintense. No or subtle enhancement. Typically no diffusion restriction.
Differential includes low-grade astrocytoma (cortex rarely involved, calcification infrequent), DNET ("bubbly" appearance, temporal lobe, \<20).
51
Diagnosis?
Demographic?
**Oligodendroglioma**- a primary intracranial neoplasm, accounts for 5-25% of all gliomas.
Most frequently presents in 4th-5th decade. Most frequently present with seizures due to cortical involvement. More aggressive tumors tend to have 1p/19q deletions, but better response to chemo.
52
What is a DNET?
Imaging features?
Dysmembryoplastic neuroepithelial tumor. A benign mixed neural/glial tumor, presenting as partial seizures in patients _\< 20_.
Cortical lesions, most often in the temporal \> frontal lobes. **Small, cystic, "bubbly" appearance.**
**CT**- hypodense. 20% have calcifications. Inner scalloping of the skull adjacent to the lesion.
**MRI-** T1 hypointense, T2 hyperintense. _Bright rim on FLAIR images_. No surrounding vasogenic edema. No/faint enhancement.
53
Which 2 tumors are mixed neuronal-glial cell tumors, and how to they look different?
DNET (bubbly cystic) and
Ganglioglioma (cystic, not multilobulated, presents as a mural enhancing nodule, but other features similar).
54
Diagnosis?
DNET.
Age \<20 only.
55
Imaging appearance of a dermoid cyst?
Vs epidermoid cyst?
Most frequent in the midline, supratentorial (sellar, parasellar, frontonasal).
**CT-** round, lobulated low attenuation mass. Capsule can calcify. Can remodel adjacent skull.
**MRI-** T1 hyperintense, T2 heterogenous, do not enhance. Displaces vessels. Broad lipid peak on MR spectroscopy (-0.9 - -1.3). _If ruptured:_ fat-fluid levels in the frontal horns, diffuse hyperintense droplets on T1, extensive pial enhancement.
Epidermoid cyst- contains only squamous epithelium (not glandular too), signals like dirty CSF. Encases vessels. Most frequent locations- CPA, ventricles (not midline). More common overall, but less common in peds.
56
Diagnosis?
Etiology?
Population?
Ruptured dermoid cyst.
Ectodermal inclusion cyst that contains squamous and glandular tissue (middle of the spectrum from epidermoid cyst to teratoma).
Typically present in the first 3 decades of life.
57
Imaging appearance of an epidermoid cyst?
Location typically away from the midline: CPA most common, followed by 4th ventricle.
**CT:** resemble CSF, rarely calcify.
**MRI:** isointense to CSF on T1, slightly hyperintense to CSF on T2 and FLAIR. _Bright on diffusion due to T2 shine through_.
Encases arteries without compromising the lumen.
58
Diagnosis?
2nd most common location?
Epidermoid cyst.
4th ventricle (CPA most common).
59
4th ventricular tumors- which one arises from the floor, which from the roof?
How can you tell them apart on CT?
Floor: Ependymoma.
Roof: Medulloblastoma.
On CT, ependymoma is isodense and medulloblastoma is usually hyperdense.
60
What is an ependymoma?
Imaging appearance?
Glial tumor from differentiated ependymal cells. 3rd most common tumor of the posterior fossa in children. No gender predilection.
Most common location - arising from floor of the 4th ventricle, can extend through the foramen of Luschka into the subarachnoid space. Can also be supratentorial (usually extraventricular), better survival rate.
**CT:** isodense. Punctate or coarse calcifications in 40-80%.
**MRI:** T1 isointense, T2 slightly hyperintense in pseudocystic areas. Moderate enhancement except for cyst like regions. Hydrocephalus and hemorrhage common.
61
Diagnosis?
Ependymoma.
62
What is a medulloblastoma?
Imaging features?
Grade IV primitive neuroectodermal tumor. Fast growing. Most common posterior fossa tumor in children (can also be seen in adults, less aggressive).
Majority arise from the cerebellar vermis, protrude into the 4th ventricle from the roof. Causes hydrocephalus.
CT: High density, homogeneous enhancement, cyst formation (50%). Surrounding vasogenic edema. Rarely calcify.
MRI: T1 hypointense. T2 heterogeneous. High choline peak on MRS.
Scan entire neuroaxis for spinal lesions.
63
What is basal nevus syndrome?
The association of dural calcifications, kratocysts of the jaw, and medulloblastoma.
64
Diagnosis?
Medulloblastoma.
65
What is a choroid plexus papilloma?
Location?
Imaging appearance?
A rare benign neuroectodermal tumor (but immaging cannot differentiate from the less common choroid plexus carcinoma).
Peds- atria. Adults- 4th ventricle (may extend through foramen of Luschka to subarachnoid space). Seeding can occur- image whole neuraxis.
**Small, cauliflower-like masses with peripheral lobulations. **
CT: high attenuation, calcifications in 25%, heterogeneous enhancement.
MRI: T1 hypointense, T2/flair hyperintense. Avid enhancement.
Use lobulated appearance to differentiate CPP from ependymoma.
66
Diagnosis?
Choroid plexus papilloma.
67
What is the most common primary posterior fossa tumor in adults?
Cerebellar hemangioblastoma.
(the most common mass in general is mets)
68
Diagnosis for a cystic posterior fossa mass with an enhancing mural nodule?
Cerebellar hemangioblastoma in an adult, pilocytic astrocytoma if \< 20.
69
Imaging appearance of a cerebellar hemangioblastoma?
Association, other things to look for?
Intra-axial cystic mass with an enhancing mural nodule. Can be solid.
4-20% associated with Von Hippel-Lindau. In patients with VHL, look for multiple brain hemangioblastomas, retinal hemangioblastomas (50%), renal cysts (70%), pancreatic cysts (50%), RCC (30%), pheochromocytoma (12%), pancreatic islet cell tumor (10%).
70
Young patient with hydrocephalus and a prominent midbrain?
Tectal glioma.
71
What is a tectal glioma?
Appearance?
Association?
Focal or infiltrative brainstem gliomas arising in the tectum (dorsal part of midbrain). Often low grade astrocytoma, good prognosis. Seen in children, usually 4-10 years of age.
CT: calcifications, hydrocephalus.
MRI: T1 isointense, T2/flair hyperintense. Variable enhancement, may be none.
Associated with neurofibromatosis type 1 (better prognosis).
72
9 year old with new headaches and hydrocephalus... diagnosis?
Tectal glioma.
73
What is the most common pediatric brain tumor? What are it's imaging features?
Associations?
**Pilocytic astrocytoma.** A low grade astrocytoma. Typically arises from midline structures, most common location is cerebellum. Cystic mass with mural nodule.
CT: Hypodense cyst, isodense nodule. 20% calcify.
MRI: cyst is T1 hypo, T2 hyperintense. Enhancement of the nodule, possible ring enhancement of cyst.
Associated with NF1. Typical location in NF1 patients is the optic nerves/chiasm.
Note- appearance is similar to cerebellar hemangioblastoma, but that is in adults and pylocytic astrocytoma is in kids.
74
What is the differential diagnosis for CPA angle masses and how can you tell them apart?
#1) Vestibular schwannoma. Start in the IAC. Diffuse enhancement, no dural tail. Microhemorrhage on T2.
#2) Meningioma. Starts in CPA, rarely extends through IAC. Avidly enhancing with dural tail. No microhemorrhage.
#3) Epidermoid cyst. Engulfs vessels and nerves. Follow CSF on T1/2, but bright on FLAIR. High signal on diffusion because of T2 shine through. No enhancement.
75
Diagnosis?
Imaging features?
Association?
Vestibular (accoustic) schwannoma.
CT: enlarged ICA with mass isodense to brain, no calcs.
MRI: T1 isointense, T2 may show microhemorrhage, avid enhancement. Low signal on diffusion. Rarely can present with mural cyst.
If bilateral, think NF2, esp if meningiomas.
76
Imaging appearance of GBM?
A grade 4 astrocytic tumor- the most common primary intracranial neoplasm.
Large, irregular heterogeneous mass with central necrosis and thick peripheral enhancement (typically thicker than with abscess). Typically supratentorial, involves the corpus callosum, and causes extensive vasogenic edema and mass effect. Calcs rare. MRS- reversal of Hunter angle (low NAA, elevated choline). No diffusion restriction.
Increased incidence in NF1.
77
What is Turcot syndrome?
GBM, medulloblastoma, and colonic adenomatous polyposis.
78
Diagnosis?
Differential?
Presentation?
Imaging appearance?
**Germinoma.** Most common pineal region mass (germinomas most common in suprasellar region, 2nd pineal region, rarely thalamic/basal ganglia). Malignant.
**Differential:** germinoma, teratoma, pineoblastoma.
**Presentation:** 2nd-3rd decade. Often with DI. More common in males.
**Imaging:** Hyperdense on CT. Iso to slightly hyperdense on T1 and T2. Diffuse enhancement. Frequently invades posterior 3rd ventricle.
_Pineal calcifications in a child is highly suspicious for germ cell tumor_ (germinoma engulfs the central calcified gland, vs pineoblastomas which arise from the gland and displace the calcs superiorly).
CSF study with elevated aFP, B-hCG, placental alk phos indicates the presence of a germ cell tumor (any type).
79
Imaging features of meningioma?
WHO grade?
**CT:** hyperdense, 25% calcify, may have adjacent cortical thickening or inner table invasion.
**MRI:** T1 isointense, T2 variable. May be peripheral edema. Diffuse contrast enhancement with dural tail.
**Angiogram:**"mother-in-law" sign- arrives early, stays late.
Less frequently have cystic degeneration, necrosis, or hemorrhage.
Most common in females aged 40-60. Typical meningioma- WHO grade I, atypical meningioma- WHO grade 2, malignant meningioma- WHO grade 3.
80
Differential diagnosis for a suprasellar mass?
"SATCHMOE"
## Footnote
S - sellar tumour (pituitary adenoma), sarcoid
A - aneurysm
T - teratoma or tuberculosis (and other granulomatous diseases)
C - craniopharyngioma, cleft cyst (Rathke), chordoma
H - hypothalamic glioma, hamartoma of tuber cinereum
M - meningioma, metastasis
O - optic nerve glioma
E - eosinophilic granuloma, epidermoid/dermoid
81
Imaging features of pituitary macroadenoma?
Mean age at presentation?
How different from craniopharyngioma?
Meningioma?
CT: expansion of sella, no calcifications. May see hemorrhage
MRI: T1 isointense, T2 heterogenous & may have cystic areas, diffuse enhancement.
Mean age 20-40 years. Benign, 75% have hormonal activity, usually prolactin.
VS. craniopharyngioma: mostly suprasellar (only 25% intrasellar), calcifications typical. Mixed solid/cystic, solid component has reticulated pattern of enhancement. Bimodal age distribution (childhood, older adults).
VS. meningioma: rarely affect the sella, more often suprasellar.
82
What are the two most common intramedullary tumors in adults, and how do they look on imaging?
**#1- intramedullary ependymoma**, presents slightly older (mean age 39 y). Well-defined intraspinal mass, cervical location most common. "Cap sign" due to hemosiderin in the cephalic or caudal margin. Enhance intensely. Central location in the cord.
**#2- intramedullary astrocytoma**. Infiltrating, thoracic spine more common. Rare bleeding (no cap sign). T1 iso, T2 bright, moderate enhancement. Eccentric location in the cord. Often associated with a syrinx. Mean age at presentation 29 years. This is the most common intramedullary tumor in children.
Could also consider intramedullary hemangioblastoma, in Von Hippel-Lindau, posterior aspect of the cord. Enhancing mass, adjacent to subpial cysts (syrinx less likely), may have flow voids.
83
Most common tumors to cause leptomeningeal carcinomatosis?
Imaging findings?
How to differentiate mets from infection?
Lung, breast, lymphoma.
Nodular enhancement of the nerve roots, meningeal enhancement.
Both can have meningeal enhancement and bright signal in the sulci on FLAIR. Hematogenous parenchymal abscesses will be bright on diffusion, which can help differentiate them from mets.
84
Diagnosis?
MR appearance?
Colloidal cyst. Benign cyst (epithelial lining with mucous goblet cells) attached to the roof of the 3rd ventricle. Originate from the endoderm.
MR T1/2 variable appearance (often bright on T1). Usually no enhancement (rarely rim enhancement due to adjacent veins). No calcifications.
85
What are the most common intradural extramedullary masses, and what are key imaging features?
#1) Spinal **schwannoma**. Typically located anterior and laterally in the spinal canal, often compress the cord. Extend to neural foramen and enlarge it (can have dumbell appearance). Typically solitary (unless NF2). CT- iso to cord, T1 low, T2 bright, intense enhancement (may have target sign). Can have fatty or cystic degeneration, hemorrhage. No calcs, no bony erosion.
#2) **Meningioma**. Typically located in the posterior and lateral aspect of the spinal canal. Intense enhancement, do not extend into neural foramen. Calcs rare.
Also consider neurofibroma. If solitary, cannot differentiate from schwannoma. If multiple (NF1), multiple masses exiting the neural foramina, enhance intensely.
86
Diagnosis?
Spinal schwannoma.
87
Diagnosis?
Etiology?
Types?
Differential?
Craniopharyngioma.
Epithelial neoplasm arising from the squamous epithelial rests of the Rathke pouch. Present with visual distrubance, endocrine dysfunction, increased intracranial pressure. Bimodal age distribution (5-14, 65-74).
Can be divided into adamantinomatous (more common in children, greater cystic component, calcs almost always) and papillary (adult, more solid component, calcs less common) types.
Differential includes Rathke cleft cyst (benign epithelium-lined cyst, remnant of Rathke pouch, cystic lesion with smooth margins, high T1 signal with thin rim/no enhancement) and pituitary adenoma (isointense to gray matter, homogeneous intense enhancement, can have necrosis, cystic degeneration, hemorrhage).
88
What is diffuse axonal injury?
Imaging features?
Multiple small hemorrhages in the deep white matter, due to traumatic deceleration impact producing rotational forces- injure the areas where density difference is the greatest.
Petechial hemorrhages- gray-white matter junction, corpus callosum, dorsolateral rostral brainstem, caudate, thalamus, tegmentum, internal capsule. Areas of axonal injury bright on diffusion. MR spectroscopy may show diffusely elevated lactate levels- this correlates with poor clinical outcome. Normal CT at presentation in 50-80%.
89
What is a subdural hygroma?
A CSF collection that develops 6-30 days after a traumatic arachnoid tear. On CT, subdural hygromas have the same density as CSF. Blood vessels crossing through the collection help differentiate subdural hygromas from chronic subdurals.
90
The integrity of which spinal column is most crucial to spinal stability?
Middle (posterior vertebral bodies, posterior longitudinal ligaments, and posterior annulus fibrosus).
91
What is the appearance of blood on MRI over time?
1) Hyperacute (intracellular oxyhemoglobin, \< 1 day): T1 ISO / T2 iso-BRIGHT.
2) Acute (1 to 2 days, intracellular deoxyhemoglobin): T1 ISO / T2 DARK.
3) Early subacute (2 to 7 days, intracellular methemoglobin): T1 BRIGHT / T2 DARK.
4) Late subacute (7 to 14-28 days, extracellular methemoglobin): T1 BRIGHT / T2 BRIGHT.
5) Chronic ( \>14-28 days, intracellular haemosiderin): T1 DARK / T2 DARK.
(note- flair is same as T2)
92
What is a Duret hemorrhage?
Differential?
Brainstem hemorrhages that develop as a consequence of rapid downward trans-tentorial herniation. Due to shearing of stretched perforating branches of the basilar artery.
Differential - diffuse axonal injury (usually multifocal, tends to be dorsal midbrain), hypertensive brainstem hemorrhage (usually larger, no herniation).
93
What is this structure?
What is in it?
AKA lateral sellar compartment. It is one of the dural venous sinuses. It is located on either side of the pituitary fossa and body of the sphenoid bone between the endosteal and visceral layers of the dura.
Contents: The cavernous sinus transmits multiple cranial nerves to the superior orbital fissure (all but V2) and foramen rotundum (V2). These are: (in the lateral wall from superior to inferior) **oculomotor nerve (CN III)**, **trochlear nerve (CN IV)**, **trigeminal nerve (CN V)** ophthalmic (1) and maxillary (2) divisions. Traversing the sinus lateral to the ICA: **abducents nerve (CN VI)**. Also contains the **cavernous ICA** (C4).
94
What is Meckel's cave?
What lesions can occur here?
Meckel's cave (trigeminal cave) is a CSF-containing arachnoidal pouch protruding from the posterior cranial fossa which houses the trigeminal ganglion. Situated at the posterolateral aspect of the cavernous sinus on either side of the sphenoid bone.
Lesions of Meckel's cave: trigeminal schwannoma (most common), meningioma, epidermoid cyst, lipoma, metastases (including retrograde spread of head and neck tumours), pituitary macroadenoma, base of skull tumours, ICA aneurysms/vascular malformation.
95
Which level is most commonly affected in spondylolysis?
Degenerative spondylolisthesis?
L5-S1.
L4-L5.
96
What are the complications of cerebral aneurysm?
1) Rupture- SAH, parenchymal hematoma, hydrocephalus.
2) Vasospasm- 4-5 days after rupture, secondary infarctions, leading cause of death.
3) Mass effect- cranial nerve palsies, headache.
4) Rebleeding- 50% within 6 months, 50% mortality.
(multiple in 20%)
97
Which conditions are associated with increased risk of cerebral aneurysms?
ADPKD, aortic coarctation, FMD, Marfan, Ehlers-Danlos, NF1, a1-antitrypsin deficiency.
98
Diagnosis?
Imaging findings?
Moyamoya disease.
Progressive occlusion of branches of the circle of Willis. Occlusive changes in the distal ICAs or proximal ACA/MCAs. Hypertrophy of the leptomeningeal collaterals results in "puff of smoke" appearance on angiogram.
99
Moyamoya syndrome/disease- what is the difference?
Age affected?
Associated conditions?
Disease- idiopathic. Syndrome- underlying condition known.
Children in 1st decade of life or adults in 3rd-4th decade.
Sickle cell, Down syndrome, Fanconi anemia, NF 1. Also- radiation therapy, familial.
100
Diagnosis?
Cause?
Central pontine myelinolysis / Osmotic demyelination.
Symmetric, noninflammatory demyelination within the white matter tracts of the central pons (occasionally demyelination can also be seen in extrapontine regions such as midbrain, thalami/basal ganglia, cerebellum), complication of rapid correction of hyponatremia.
101
Typical branches and supply of the posterior circulation?
Vertebral arteries give off **posterior inferior cerebellar artery** (PICA), which supplies the inferior cerebellum.
Verts join to form the basilar (a hypoplastic vert may terminate in PICA). Basilar gives off:
**Anterior inferior cerebellar artery**, which supplies the lateral aspects of the medulla and pons. Then:
**Superior cerebellar artery**, which supplies the superior cerebellum including the superior cerebellar peduncle and upper dorsolateral pons and midbrain.
Basilar artery branches (perforators) supply the paramedian and anterolateral brainstem. The proximal posterior cerebral artery (P1) supplies regions of the midbrain, mammillary body, and optic tract.
102
What are Virchow-Robin spaces?
"Prominent perivascular spaces..." extensions of the subarachnoid space surrounding the blood vessels.
103
What is CADASIL?
Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy.
An autosomal dominant vascular dementia, linked to a gene on **chromosome 19**, that presents with **multiple lacunar and subcortical white matter infarctions**. There is disproportionate cortical hypometabolism. Presenile dementia and migraines develop in the third to fourth decades of life. **Cerebral microhemorrhages common.**
104
What is MELAS?
**Mitochondrial encephalopathy with lactic acidosis and stroke-like episodes**- a mitochondrial disorder (inherited only from the mother).
Characterised by 'stroke-like' episodes, typically in childhood or early adulthood (90% present before 40 years of age), encephalopathy, seizures, dementia, lactic acidosis, muscle weakness, deafness. Relapsing remitting course.
Imaging- multiple infarcts involving multiple vascular territories.
105
Imaging findings in cereral amyloid angiopathy?
Cause?
Presentation?
Spontaneous cortical-subcortical intracranial hemorrhage in the normotensive elderly. Leukoaraiosis. May see encephalomalacia from prior bleeding. GRE sequences to evaluate for microhemorrhages.
Deposition of B-amyloid protein in the media and adventitia of small and medium-sized vessels.
May present as stroke, TIA, or dementia.
106
Diagnosis?
Other things to look for?
Treatment options?
Venous sinus thrombosis. (presentation includes- HA, focal neurologic defects, seizures)
Infarctions in a nonarterial distribution in the white matter and/or cortical-white matter junction. Parenchymal hemorrhage in 1/3- typically cortical with subcortical extension (may have simultaneous extra-axial hemorrhage). On MRI, signal intensity of the thrombus will vary with time so be careful not to confuse it for flow.
Treatment options- anticoagulation with heparin or endovascular recanalization.
107
What is the Spetzler-Martin grading scale for AVMs?
Helps predict the likelihoot of a good outcome if surgical resection is attempted. Depends on size of the nidus, eloquence of the adjacent brain parenchyma, and deep vs superficial venous drainage.
Conventional cerebral angiography is the gold standard for characterizing the lesion and planning treatment.
108
DIagnosis?
Cause?
Vein of Galen aneurysmal malformation.
Rare congenital vascular malformation, characterized by shunting of arterial flow into an enlarged cerebral vein dorsal to the tectum. Secondary to a cerebral AV fistula of the median prosencephalic vein (MPV) (a precursor of the vein of Galen), occurring at 6-11 weeks gestation. The MPV fails to regress and becomes aneurysmal.
Can present with hydrocephalus, but usually do not shunt until VGAM obliterated because it can worsen cerebral perfusion.
109
What are the differences between spinal dural AVF and spinal AVM?
Spinal dural AVF: acquired. Fed by radiculomeningeal arteries, shunt located in the dura. Venous congestion and intramedullary edema lead to chronic hypoxic myelopathy. Treated with surgical ligation or glue embolization.
Spinal AVM: congenital. Fed by radiculomedullary (cord) arteries, intra- or perimedullary shunt. Venous congestion, hemorrhage, steal phenomenon.
110
Imaging findings of infectious meningitis (viral/bacterial)?
vs TB meningitis?
**Smooth, diffuse leptomeningeal enhancement.** Typically thicker in bacterial than viral. _Effacement of the sulci._
**TB** causes granulomatous meningitis. Usually focal, predominantly in the cisterns around the skull base and suprasellar region (sarcoid can do this too). Thickened, nodular enhancement and posssibly parenchymal extension (tuberculomas). Complications- infarcts.
111
Diagnosis?
Differential and differentiating features?
**Pott disease** (tuberculus osteomyelitis): large thin walled perivertebral abscesses, \>2 nonadjacent vertebral bodies due to subligamentous spread, starts in anterior vertebral body (can see gibbous deformity), endplate destruction, spares disk (until very late).
vs:
**Spondylodiskitis** (diskitis/osteomyelitis): abnormal signal in two adjacent vertebral bodies and the disk, enhancement of the affected bodies/disk, endplate destruction, soft tissue enhancement, abscess late (thick walled). Staph aureus most common pathogen.
112
Acute onset. Diagnosis?
Mortality?
Diagnosis if chronic?
**Herpes encephalitis**- the most common cause of infectious limbic encephalitis. **CT**- normal early, hypodense medial temporal lobes late. **MRI**- increased T2/flair signal in the medial temporal lobes involving the cortex, loss of gray-white, restricted diffusion, can show patchy enhancement. Late can affect other limbic structures (insula, cingulate gyrus, inferior frontal lobe). More common in immunocompromised.
Mortality 50-70%.
Autoimmune limbic encephalitis. Can be paraneoplastic (lung, thymus, breast, testicular cancer) or nonparaneoplastic (rare, associated with K channel antibody).
113
5 year old child with pituitary stalk enlargement... think of what?
Histiocytosis.
114
HIV+ patient. Differential and differentiating features?
**Toxoplasmosis:** the most common in CNS infection in patients with AIDS. Multiple lesions with ring enhancement at the corticomedullary junction and in the basal ganglia. Does not extend to the ependymal surface. Eccentric target sign- ring and central enhancement- highly suggestive. Vasogenic edema in acute lesions. Occasional hemorrhage. MRS: choline low. Decreased uptake on thallium 201.
**Primary CNS lymphoma:** Enhancing lesions in the basal ganglia and periventricular regions. Frequently affects the corpus callosum, _can extend to the ependymal surface_. Vasogenic edema less frequent. No hemorrhage. MRS: choline high. Increased uptake on thallium 201.
Also could consider mets with grey-white junction ring enhancing lesions. Mets uncommon in basal ganglia.
115
HIV (or transplant) patient. Diagnosis and imaging findings?
Cause?
Differential?
**Progressive multifocal leukoencephalopathy** (PML). Diffuse, patchy, asymmetric white matter lesions, mainly in the subcortical and periventricular white matter, thalamus. CT: bilateral asymmetric areas of low attenuation. MRI: hypointense on T1, bright on T2/flair. No enhancement or mass effect. Cortical atrophy, ventricular dilation common. MRS: high choline.
A fulminating opportunistic infection with JC polyomavirus.
VS **HIV encephalitis** (see pic below): diffuse, _symmetric_ periventricular white matter T2 hyperintensities (hypodense on CT). _Subcortical white matter spared_. No enhancement or mass effect. Cortical atrophy and ventricular dilation.
**CMV infection:** encephalitis with periventricular white matter hyperintensities and ventriculitis with _periventricular enhancement_.
116
Septic emboli...
Differentiating feature from mets?
From aseptic emboli?
Indicated study in IV drug abusers with intracranial hemorrhage?
Septic emboli have restricted diffusion, mets don't.
Septic emboli have surrounding vasogenic edema, aseptic don't.
Study the intracranial vasculature to exclude mycotic aneurysm.
Note- hemorrhage in septic emboli common.
117
Diagnosis?
Most common cause?
Other imaging findings?
Ventriculitis.
Ruptured abscess, ventricular catheter infection.
Hydrocephalus, ventricular debris, periventricular signal abnormality, enhancement of the ventricular walls, restricted diffusion.
118
What is ADEM?
Who is affected?
**Acute disseminated encephalomyelitis**- a monophasic demyelinating disease that presents with numberous hyperintense white and gray matter lesions on T2. Follows an infectious episode or vaccination.
Most common in young and adolescent children. Symptoms variable- include seizures, coma, behavioral disturbances, fever, H/A, vomiting. Good prognosis.
119
Child with AMS following a viral illness... diagnosis?
Imaging features?
Acute disseminated encephalomyelitis.
CT often normal. MRI: T2 - multiple asymmetric ill-defined high signal areas typically situated in subcortical locations; the thalami, brainstem, and spinal cord can also be involved. Variable enhancement, may see ring or arc enhancement (open ring sign) along the leading edge of inflammation. DWI - there can be peripheral resctricted diffusion.
Differential: MS, viral encephalitis, Susac syndrome (rare microangiopathy affecting brain, retina, and cochlea).
120
Rapidly progressive dementia. Diagnosis?
Differential for the imaging findings?
**Creutzfeldt-Jakob disease.** Symmetric areas of restricted diffusion and T2 hyperintensity involving the basal ganglia (can precede typical clinical findings). No mass effect or enhancement. Decreased CBF in areas with restricted diffusion. Prion infectious disease, predominantly affecting gray matter structures.
Differential... *hypoxic ischemic injury* (acute AMS following cerebral hypoperfusion, restricted diffusion and T2 signal changes in basal ganglia and cerebral cortex, predilection for the globus pallidus) and *carbon monoxide poisoning* (acute or delayed, low T1/high T2 in globus pallidus and other basal ganglia due to necrosis, may also involve white matter and cortex).
121
Typical differentiating features between MS in the cord and transverse myelitis?
_MS_: T2 hyperintense lesions, typically peripheral, less than 2 vertebral segments in length and occupy \<1/2 the cross-sectional area of the cord. May enhance.
_Transverse myelitis_ (clinical syndrome of bilateral motor, sensory, and autonomic disturbances): T2 hyperintense lesions, typically central, length of \>3-4 vertebral body segments, usually occupy \>2/3 of the cross-sectional area of the cord. Enhancement infrequent.
Another consideration for T2 hyperintense lesions in the cord would be _Devic Syndrome (neuromyelitis optica)_- bilateral visual disturbance and transverse myelopathy. Confluent T2 hyperintense lesions extending across 5+ vertebral segments. Cord swelling and enhancement may be present.
122
Diagnosis? Cause?
Imaging features?
Symptoms?
Central pontine myelinolysis (osmotic demyelination). Acute demyelination of the white matter tracts of the pons, usually secondary to rapid correction of hyponatremia.
Symmetric T2/flair bright signal in the central pons. Spares the corticospinal tracts. May be T2 shine through on diffusion. Can also affect cerebellum, thalamus, globus pallidus, putamen.
Initially encephalopathy due to the hyponatremia, then spastic quadriparesis and pseudobulbar palsy 2-3 days later as a consequence of the myelinolysis.
123
Patient with sensorineural hearing loss and cerebellar dysfunction. Diagnosis and cause?
Best sequence for diagnosis?
**Superficial siderosis.**
Deposits of hemosiderin along the leptomeninges, often due to recurrent hemorrhage. Leads to reactive gliosis and demyelination of the cerebellum and cranial nerves 1-8.
Thin rim of low intensity on the surface of the CNS, best seen on T2 GRE sequences.
(An increased amount of leptomeningeal melanin can be a normal variant in patients with heavier skin pigmentation, see T2 hypointense rim on the surface of the medulla, but this will not be dark on GRE sequences)
124
What is McCune-Albright syndrome?
Polyostotic fibrous dysplasia with cutaneous (cafe au lait spots) and endocrine abnormalities (precocious puberty).
(MRI of fibrous dysplasia- usually intermediate signal on T1 and low signal on T2).
125
What is the difference between communicating and noncommunicating hydrocephalus?
Communicating: the CSF flow blockage is outside the ventricular system (basal cisterns or parasagittal arachnoid villi). Causes include meningitis, subarachnoid hemorrhage, meningeal carcinomatosis, and abnormal skull base.
Noncommunicating: intraventricular obstruction with dilation proximal to that point.
126
What is PRES?
What are some causes?
Posterior reversible encephalopathy syndrome. The result of neurotoxicity-induced vasogenic edema. Symmetric regions of CT hypodenisty, T2 hyperintenisty, most commonly in the parietal and occipital lobes.
Causes include: pregnancy (preeclampsia/eclampsia), post transplant, immunosuppression, sepsis, autoimmune diseases, chemotherapy, dialysis.
127
Appearance of a colloid cyst?
Etiology?
Differential?
Well-defined round mass in the vicinity of the foramen of Monro. Often hyperdense on CT. Variable on MRI, usually no enhancement (but rarely see thin rim of enhancement).
Remnant of Rathke cleft. Most common presentation- positional headache.
Differential includes central neurocytoma- a benign tumor arising from neuronal precursor elements. Well-defined, lobulated intraventruclar mass near the foramen of Monro or septum pellucidum. Mild-mod enhancement. Calcs and cystic changes are common. Usually young adults, symptoms of obstruction.
128
What is the risk of developing MS after an episode of optic neuritis?
Other causes of optic neuritis?
40% after 10 years and 50% after 20 years. (Inflammatory optic neuropathy- imaging features = T2 hyperintensity and contrast enhancement involving segments or the entire length of the optic nerve). There amy be clinically silent white matter lesions in the brain at the time of presentation.
Optic neuritis can also be idiopathic or secondary to sarcoid, viral infection, vasculitis, ischemia, or radiation.
129
What imaging findings can be seen with hepatic encephalopathy?
Acutely, can see diffuse brain edema and blurring of the gray-white junction. Chronically, see T1 hyperintensities in the globus pallidus due to manganese deposits (can also see this in TPN). Can see T2/flair white matter abnormalities as well due to increased ammonia in the CNS. These findings are reversible.
130
Diagnosis?
Causes?
**Superficial siderosis**.
Causes include: spinal dural defects, trauma,
post-op, intracranial neoplasms (ependymoma,
oligodendroglioma,
astrocytoma), vascular abnormalities (AVM,
aneurysm
), cerebral amyloid angiopathy, idiopathic
131
What drug is used to assess cerebrovascular reserve in neuro angio?
**Acetazolamide** penetrates the blood-brain barrier slowly and inhibits carbonic anhydrase and causes vasodilation and an increase in cerebral blood flow. It is _used to assess cerebrovascular reserve in patients with stroke or transient ischemic attacks for possible revascularization_.
132
What are the most common causes of temporal lobe epilepsy?
**Mesial temporal sclerosis** : 70%.
Temporal lobe tumours : 10% (**ganglioglioma** most common, followed by **pleomorphic xanthoastrocytoma**).
Cortical dysplasia(s) : 5 - 10%.
Vascular malformations : 5%.
Also trauma, infection.
133
Young patient with seizures. Diagnosis?
Appearance?
Differential?
**Pleomorphic xanthoastrocytoma**. Rare low grade astrocytoma, can cause temporal lobe epilepsy. Most common in children and young adults.
Usually well-circumscribed, often have a cystic component, cortically based, often in the temporal lobe, little surrounding edema. CT: hypo-isodense. No calcs. MRI: T1 hypo, T2 hyper. Solid component enhances. Can have a reactive dural tail.
Differential includes ganglioglioma, oligodendroglioma, JPA (usually in posterior fossa), DNET (bubbly, usually little or no enhancement).
134
18 M with seizures. Diagnosis?
Typical appearance?
**Ganglioglioma**. Low grade tumor, most common site is temporal lobes but can be anywhere. Common cause of temporal lobe epilepsy. Seen in children and young adults.
Variable appearance (~50% enhance, in solid component). CT: iso-hypodense, _calcifications common_. MRI: T1 iso-hypo, T2 hyper solid component. Variable enhancement. May be partially cystic, cystic component can have variable signal depending on proteinaceous material/blood products.
