NEURO 3 Flashcards
Order of myelination
- inferior to superior
- posterior to anterior
- central to peripheral
- sensory then motor
last structures to myelinate
subcortical white matter (occipital at 12 months, frontal at 18 months)
structures that are myelinated at birth
- posterior limb of internal capsule
- brainstem
order of sinus formation
maxillary –> ethmoid –> sphenoid –> Frontal
what structures are in the superior orbital fissure
CN 3, CN4 ,CN V1, CN6
what structures are in the inferior orbital fissure
V2
Segments of the ICA
C1: cervical
C2: petrous:
C3: Lacerum
C4: cavernous
C5: clinoid - aneurysm can compress CN2
C6: Supraclinoid (Ophthalmic) - common site for aneurysm; originats at dural ring
C7: communicating/terminal - aneurysm can compress CN3
What structure can get compressed with a subfalcine herniation
The cingulate gyrus is herniated under the falx, and if progression occurs, other areas of the frontal lobe are involved
Complications
hydrocephalus due to obstruction of the foramen of Monro
anterior cerebral artery (ACA) territory infarct due to compression of ACA branches, specifically the pericallosal artery
focal necrosis of the cingulate gyrus due to direct compression against the falx cerebri
ACA infarction occurs as the cingulate sulcus extends under the falx dragging the ipsilateral anterior cerebral artery with it. If this becomes compressed against the falx, distal anterior cerebral artery infarction can occur, the most common clinical manifestation being contralateral leg weakness.
In subfalcine herniation, the degree of midline shift correlates with the prognosis; less than 5 mm deviation has a good prognosis, whereas a shift of more than 15 mm is related to a poor outcome 4.
What are signs of an uncal herniation
aka descending transtentorial
- ipsilateral hemiparesis (Kernohan’s notch phenomenon)
- ipsilateral pupillary dilation and ptosis from CN3 compression
Marchiafava Bignami
- alcoholics
- edema and T2 bright in corpus callosum (beginning in body, then genu, then splenium); affects central fibers and spares the dorsal and ventral fibers (sandwich sign)
disseminated necrotizing leukoencephalopathy
- seen in leukemia patients getting radiation and chemo
- severe white matter changes, with ring enhancement
- can be fatal
Subcortical Arteriosclerotic Encephalopathy
- aka Binswanger disease
- multi-infarct dementia that only involves white matter
- favors white matter of centrum semiovale
- spares subcortical U fibers
- strong association with HTN
- older patients 55+
CADASIL
Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy
- 40 year old with migraines
- severe white matter disease involving multiple vascular territories in frontal and temporal lobes
- occipital lobes are usually spared
Primary brain tumors that can be multifocal
- lymphoma
- GBM - can be multicentric or can be multiple from seeding
- gliomatosis cerebri
- Medulloblastoma (from seeding)
- ependymoma (From seeding)
- Oligodendroglioma (From seeding
Cortically based tumors
PDOG
- pleomorphic Xanthoastrocytoma
- Dysembryoplastic Neuroepithelial tumor (DNET)
- Oligodendrogliomas
- Gangliogliomas
Pleomorphic Xanthroastrocytoma (PXA)
- ALWAYS supratentorial
- usually involves temporal lobe
- often a cyst with a nodule
- tumor frequently invades leptomeninges
- looks similar to DIG but does not occur in an infant
- occurs at age 10-20
- enhances
https://radiopaedia.org/articles/pleomorphic-xanthoastrocytoma
DNET (Dysembroplastic Neuroepitheilal Tumor)
- kid (<20 yrs) with drug-resistant seizures
- temporal lobe
- focal cortical dysplasia seen in 80%
- little surrrounding edema
- Bubbly lesion; high T2 signal
- does NOT enhance
Oligodendroglioma
- most common in frontal lobe
- calcifies 90%
- expands the cortex
- 1p/19 q deletion - better outcome
- seen in adults (40-50s)
Ganglioglioma
- low grade; can enhance
- can occur at any age
- usually temporal lobe
- cystic and solid mass with focal calcification
Intraventricular tumors - arising from ventricular wall and septum
- ependymoma (kids)
- Medulloblastoma (in kids)
- Subependymal giant cell astrocytoma
- subependymoma (in adults)
- central neurocytoma
intraventricular tumors - arising from choroid plexus
- choroid plexus papilloma
- choroid plexus carcinoma
- xanthogranuloma
What syndromes are associated with medulloblastomas?
- Basal cell nevus
- Turcot’s syndrome
- Gorlin syndrome
Gorlin syndrome
- medulloblastoma
- dural calcification
- basal skin cancer after radiation
- odontogenic cysts
most common intraventricular mass in an adult 20-40 years old
central neurocystoma
Cerebellopontine angle masses
schwannoma (75%)
menignioma
epidermoid
Infratentorial tumors
- AT/RT
- medulloblastoma
- ependymoma
- JPA
- Hemangioblastoma
- ganglioglioma
- Diffuse Pontine glioma
Supratentorial tumors
- Mets
- Astrocytoma
- Gliomatosis cerebri
- oligodendroglioma
- primary CNS lymphoma
hemangiopericytoma
soft tissue sarcoma that can mimic an aggressive meningioma because both enhance homogeneously
- will not calcify or cause hyperostosis
- will invade the skull
signal of blood on MRI
- hyperacute (<24 hours): T1 iso, T2 bright
- acute (1-3 days): T1 iso, T2 dark
- early subacute (3-7 days): T1 bright, T2 dark)
- late subacute (7-14 days): T1 bright, T2 bright)
- chronic (> 14 days): T1 dark, T2 dark)
most sensitive sequence for subarachnoid hemorrhage
FLAIR
brachycephaly + wormian bones + absent clavicles
Abstract
Cleidocranial dysplasia:
- AD skeletal dysplasia
- abnormal clavicles,
- patent sutures and fontanelles,
- supernumerary teeth,
- short stature,
- and a variety of other skeletal changes.
- The disease gene has been mapped to chromosome 6p21 within a region containing CBFA1, a member of the runt family of transcription factors.
Typical clinical and radiological findings in CCD. (A) Facial appearance in a 6 month old boy. Note large, brachycephalic skull, frontal and parietal bossing with large anterior fonanelle, and the appearance of a small face. Other characteristic features include widely spaced eyes, low nasal bridge, reduced nasal length, but increased nasal width and protrusion. (B) Chest radiograph showing cone shaped thorax and left clavicular hypoplasia and aplasia on the right side. (C) Pelvic abnormalities in a 4 year old girl. Note hypoplasia of the iliac wings, broad femoral necks with large epiphyses, and unossified symphysis pubis. (D) Hand radiograph of a 2½ year old female showing hypoplastic distal phalanges, accessory epiphyses of the second metacarpal, and long second metacarpal. (E) Pantomographic view of the permanent dentition of a 16 year old female. Note multiple, unerupted, supernumerary teeth.
https://jmg.bmj.com/content/36/3/177
MELAS
mitochondrial encephalomyopathy, lactic acidosis, and stroke like episodes
on MR spectroscopy: increased lactate; decreased NAA
- CT
- multiple infarcts
- involving multiple vascular territories
- may be either symmetrical or asymmetrical
- parieto-occipital and parieto-temporal involvement is most common
- basal ganglia calcification 1,2
- more prominent feature in older patients
- atrophy 2
- multiple infarcts
- MRI
- acute infarcts
- swollen gyri with increased T2 signal
- may enhance
- subcortical white matter involved
- increased signal on DWI (T2 shine through) with little if any change on ADC: thought to represent vasogenic rather than cytotoxic oedema 3
- chronic infarcts
- involving multiple vascular territories
- may be either symmetrical or asymmetrical
- parieto-occipital and parieto-temporal most common
- MR spectroscopy:
- may demonstrate elevated lactate in otherwise normal appearing brain parenchyma or in CSF 3,4.
- acute infarcts
- Case courtesy of Dr Mustafa Takesh, Radiopaedia.org, rID: 78355
most common leukodystrophy? what does it look like?
- *Metachromatic
- diffuse white matter involvement with tigroid apperance**
Metachromatic leukodystrophy (MLD) is the most common hereditary (autosomal recessive) leukodystrophy and is one of the lysosomal storage disorders. It has characteristic imaging features including peri-atrial and to a lesser extent frontal horns leukodystrophy as well as periventricular perivenular sparing results in “tigroid pattern” on fluid-sensitive MRI sequences.
Epidemiology
Metachromatic leukodystrophy has an estimated prevalence of ~1:100,000 and typically manifests between 12 to 18 months of age. The disease can sometimes be classified according to the time of onset:
late infantile: most common ~65% (range 50-80%)
juvenile (onset between 3-10 years)
adult (after age 16)
https://radiopaedia.org/articles/metachromatic-leukodystrophy
High NAA peak
Canavan’s disease
Canavan disease is rare genetic neurological disorder characterized by the spongy degeneration of the white matter in the brain. Affected infants may appear normal at birth, but usually develop symptoms between 3-6 months of age.
Canavan disease, also known as spongiform degeneration of white matter (not to be confused with Creutzfeldt-Jakob Disease) or aspartoacylase deficiency, is a leukodystrophy clinically characterised by megalencephaly, severe mental and neurological deficits, and blindness.
Epidemiology
Canavan disease is particularly common in the Ashkenazi Jewish community 1. The carrier frequency among the Ashkenazi ranges from 1:37 to 1:57, with a corresponding prevalence of 1 in 6000-14000 in this high risk group1. In the general population the prevalence is 1 in 100000 11.
Clinical features
There are a wide range of clinical features, but generally there is a progression from lethargy and hypotonia, to macrocephaly (due to underlying megalencephaly) and spasticity, to blindness and seizures, to decerebrate posturing and eventual death 2. In the vast majority of patients, clinical onset is in infancy with death before 5 years of age, and often before 18 months, but juvenile-onset forms of the disease have also been reported 2. Juvenile-onset forms may have speech difficulty, mild intellectual impairment and suffer neurological regression 11.
Pathology
It is an autosomal recessive disorder due to a gene mutation on the short arm of chromosome 17 leading to deficiency of N-acetylaspartoacylase, a key enzyme in myelin synthesis, with resultant accumulation of N-acetylaspartate (NAA) in the brain, cerebrospinal fluid, plasma, and urine 3,4. Although its effects are widespread, it has a predilection for subcortical U-fibres and Alzheimer type II astrocytes in the gray matter 3,5.
Markers
Increased levels of NAA in the urine may be detected 11.
Radiographic features
In Canavan disease the neuroimaging findings are diagnostic of the condition 11.
CT
The oedematous sponginess of the white matter causes a characteristically low radiographic attenuation on CT so that it stands out from the relatively unaffected gray matter 4. Megalencephaly may also be also noted depending on the clinical stage 4.
MRI
MRI confirms the megalencephalic appearance and provides more detail of the white matter disease, which is typically diffuse, bilateral, and involving the subcortical U-fibres 4-8,11:
T1: areas of low signal
mainly within subcortical white matter
generally with sparing of the corpus callosum, caudate nucleus, putamen and internal capsule
as the condition progresses atrophy of the periventricular white matter may be seen with associated ventriculomegaly
globi pallidi and thalami are usually affected as well
T2/FLAIR: findings as above except for areas of high signal in the affected white matter
DWI: restricted diffusion within the diseased white matter
MR spectroscopy: markedly elevated NAA and NAA:creatine ratio are pathognomonic for the condition 11.
this can be remembered using the mnemonic CaNAAvan
There is no enhancement of affected regions on either CT or MRI 5-8.
Treatment and prognosis
The condition is fatal with death resulting at 2-5 years and treatment is generally supportive 4. No effective treatment is yet available 4. However, genetic therapies are being trialled and seem to reduce the level of NAA within the brain 11.
Circumferential vessle wall enhancement with surrounding micro hemorrhages.
https://www.asnr.org/education/neurocurriculum-live/
Leptomeningeal enhancement within the central sulcus on post contrast flare and post contrast T1W imaging.
SWI shows evidence of prior lobar hx in the right frontal libe and superficial siderosis and peripheral micro hx
https://www.asnr.org/education/neurocurriculum-live/
What is the most common Dementia syndrome?
- Alzheimers’ Dementia
- Amyloid + Tau disorder
- Amyloid alone is insufficient to cause significant neuronal damage
- Tau deposition is likely the culprit for neuronal loss
https://www.asnr.org/education/neurocurriculum-live/
Discuss the progression of the disease of Alzheimers re Amyloid, tau, FDG and MRI correlating with symptoms
- Cog impairment increases over time
- Amyloid deposition proceeds CI by many years, and in many may be asymptomatic
- Tau deposition occurs
- around the same time FDG hypometabolism occurs
- MRI positive findings of atrophy then occur
https://www.asnr.org/education/neurocurriculum-live/
What does this show?
TOP LEFT: diffuse/generalised Amyloid deposition
TOP RIGHT and BOTTOM LEFT: more regional deposition of Tau, temporal/parietal
BOTTOM RIGHT: temporal lobe and parietal lobe atrophy on MRI
https://www.asnr.org/education/neurocurriculum-live/
What are the typical imaging features of Alzeihmers on MRI?
- T1W sequences
- Coronal:
- profound mesial temporal lobe volume loss
- hippocampus
- entorhinal cortex
- Asymmetry of the left sylvian fissure
- profound mesial temporal lobe volume loss
- Parasagittal
- Pre-cuneus atrophy disproportionate to the rest of the brain
- Coronal:
Whats the dx?
- Marked atrophy over two years with a striking posterior predominance. ? AD vs DLB.
- FDG PET
- Asymmetric primary posterior hypo metabolism
- Amyloid PET (FLORBETPIR)
- Showed amyloid deposition
- Ioflupane scan done
- Reduced striatal binding
- OVERALL:
- This patient has dementia with Lewy bodies
- DLB is often amyloid positive
- So the amyloid scan may not be very useful
https://www.asnr.org/education/neurocurriculum-live/
Posterior cortical atrophy (PCA), also called Benson’s syndrome, is a rare, visual variant of Alzheimer’s disease. It affects areas in the back of the brain responsible for spatial perception, complex visual processing, spelling and calculation.
Persons with logopenic variant primary progressive aphasia (lvPPA) have increasing trouble thinking of the words they want to say. As time goes on, people with lvPPA have more trouble getting the words out, and they eventually begin to speak slower and slower.
What Causes lvPPA?
The cause of lvPPA is unknown. Scientists know that in lvPPA there is a large build-up of proteins called amyloid and tau within brain cells, which are the same proteins that build up in Alzheimer’s disease. These proteins occur normally, but we do not yet understand why they build up in large amounts. As more and more proteins form in brain cells, the cells lose their ability to function and eventually die. This causes the affected parts of the brain, most often the left posterior temporal cortex and inferior parietal lobe, to shrink.
https: //memory.ucsf.edu/dementia/primary-progressive-aphasia/logopenic-variant-primary-progressive-aphasia
https: //www.asnr.org/education/neurocurriculum-live/
What is Dementia. with Lewy Bodies?
- Possibly the second most common form of dementia
- may be difficult to distinguish from AD in early disease
- Autopsy study:
- 50% of patients with living dx of DLB had AD on Autropsy
- Autopsy study:
- A-synucleinopahty
- majority also show amyloid deposition
https://www.asnr.org/education/neurocurriculum-live/
Signs of DLB on FDG PET?
- Cingulate Island
- posterior hypometabolism with sparing of the cingulate cortex.
- Occipital Tunnel
- sparing of the calcarine cortex
- DatScan
- reduced striatal binding
- Primary progressive aphasia
- Heterogenous group of neurodegenerative disorders characterised by progressive language deficit
- Subtypes
- Non-fluent or agrammatic (navPPA)
- Semantic (svPPA)
- Logopenic (lvPPA)
- Although grouped together, the clinical symptoms, imaging and pathology are very different.
What are the different types of Primary Progressive Aphasia and their MRI Signs
Nonfluent navPPA
Logopenic Lv PPA
Semantic Sv PPA
Label which Primary progressive aphasia types these are:
- navPPA
- nonfluent variant
- Dominant hemisphete frontal lobe hypometabolism and atrophy which frequently extends to involve the temporal lobe later in the course of the disease
- SvPPA
- Asymmetric dominant lobe atrophy and hypometabolism in the temporal pole
- LvPPA
- dominate hemisphere hypometabolism temporal lobe/ posterior para sylvian and temporal lobe distribution
- Patient 3
- Profound hippocampal volume loss
- Relative Preservation of the entorhinal cortex
- Frontal lobe atrophy slightly more prominent than that of the paramedic parietal lobe
- Patient cognitively intact despite profound volume loss
- Amyloid pet scan (left picture)
- Showed normal white matter binding
- Right picture shows abnormal cortical binding
- LATE:
- Profound hippocampus damage (CA1) as well as in the subiculum, entorhinal cortex and amygdala
- ? Sunomymous with hippocampal sclerosis of aging.
- Hipoocampal sclerosis unilateral in 40-50%
- Hippocampal atrophy usually greater than those with Pure AD. Often asymmetric
- Combo of AD and LATE had greater hippocampal atrophy than those with only AD.
- Also atrophy in the frontal anterior temporal and insular cortices.
- Corresponds with the distribution of TDP-Proteinopathy on autopsy
- Typically >75 years
- profound mesial temporal atrophy, even greater with coexistent AD pathology.
- May have little cognitive impairment, MCI or severe demented (typically with +AD)
- Often asymmetric MTL atrophy (L>R in my experience)
https://www.asnr.org/
