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Neuroanatomy > Overview and Embryology > Flashcards

Overview and Embryology Flashcards

1
Q

Efferent neurone columns

A

3

Somatic

Branchial

Visceral

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2
Q

Arrangement of efferent cell columns from M->L

SBV

A

Somatic

Branchial

Visceral

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3
Q

Afferent neurone columns

A

Special visceral

General visceral

Special somatic

General somatic

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4
Q

Arrangement of afferent cell columns from M-> L

VG VS, SG, SS

A

Visceral General

Visceral special (taste)

Somatic general

Somatic special (hearing, vestibular)

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5
Q

To what do the colours correspond

A

Blue- sensory

Orange- intermediant visceral (i.e. autonomic)

Red motor

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6
Q

Pure corticospinal tracts in humans

A

Thought to be exceedingly rare due to close proximity to other corticofugal tracts (corticoreticular, corticopontine, reticulospinal, vestibulospinal).

Thought to result in deficits in delicate fractionate movement and Babinski

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7
Q

Fucntion of ventral rami of spinal nerves

A

Innervates limbs and anterior skin and muscles of trunk

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8
Q

Function of dorsal rami of spinal nerves

A

Postvertebral muscles and skin of back

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9
Q

nAChR

A

Inotropic receptor

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10
Q

mAChR

A

Metabotropic receptor (GPCR)

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11
Q

Formation of the cerebelleum

A

Forms from dorsolateral thickenings of metencephalon which overgrow the root of the fourth ventricle (rhombic lips)

These lips fuse in the midline to form the cerebellar vermis.

Peripheral neuroblasts contribute to cerebellar cortex, central-> deep nuclei

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12
Q

Origin of tectal nuclei

A

Neuroblasts from the alar plates migrate into the tectum to form the superior and inferior colliculi

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13
Q

Origin of central gray matter around aqueduct

A

Neurobalsts of the alar plates

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14
Q

What are the three major commissures beign to develop in the lamina terminalis

A

Anterior commissure

Hippocampal commissure

Corpus callosum

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15
Q

Describe the development of the corpus callosum

A

7th week

The dorsal aspect of the lamina terminalis thickens into the commissural plate which becomes thickened with cellular material that forms a glial bridge across the groove

Develops in rostral to caudal fashion.

The exception is the rostral most portion of the corpus callosum- rostrum and anterior genu which develop last

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16
Q

What might cause violation of the corpus callosal front to back development

A

Secondary destructive processes might damage the corpus callosum after it is already formed

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17
Q

How does the presentation of corpus callosum agenesis occur?

A

Due to front to back development, then developmental arrest will normally result in an intact genu with a partially or completely formed body and small or absent splenium or rostrum.

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18
Q

Small or absent genu but intact splenium and rostrum in corpus callosal agenesis suggests?

A

Secondary destructive process

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19
Q

What is the corpus callosum abnormality which is an exception to the front to back and secondary destructive lesion

A

The callosal abnormality associated with holoprosencephaly in which the corpus callosum demonstrates and intact splenium in the absence of a genu or body.

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20
Q
A

Agenesis of the corpus callosum

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21
Q

Cardinal features of corpus callosum agensis

A

Hypogensis of the corpus typically produces an intact genu and body with absent splenium and rostrum.

Other patterns suggest secondary destructive process

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22
Q

Associated anomalies, corpus callosum agenesis?

A

Dandy-Walker

Disorders of neuronal migration, organisation

Encephaloceles

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23
Q

Symptoms of callosal agenesis

A

Seizures, mental retardation.

Commonly also related to associated brain abnormalities

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24
Q

Aicardi’s syndrome

A

X-linked disorder

Infantile spasms, callosal agenesis or hypogensis, chorioretinopathy

Abnormal EEG

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25
Q

Cranium bifidum

A

Defect of neural tube closure

Cranial defect with herniation of meniniges (meningoceole) or meninges and brain (meningoencephalocoele) or meninges, brain and ventricles (meningohydroencephalocoele)

Varies from no functional impairment to severe motor and mental impairment with seizures

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26
Q

Lissencephaly

A

Absence of cortical gyri

Mental retardation and hypotonia or spasticity

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27
Q
A

Lissencephaly

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28
Q

Polymicrogyria

A

Overabundant, undersized, cortical gyri

Mental retradation and hypotonia

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29
Q

Pathophysiology of intracranial lipomas

A

Mesenchyme gives rise to the leptomeninges

Abnormal differentiation of this mesenchyme may lead to the formation and deposition of fat in subarachnoid space

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30
Q

Location of intracranial lipomas from most to least common

A

Deep interhemispheric fissure

Quadrigeminal plate cistern

Interpeduncular cistern

CPA

Sylvian cistern

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31
Q

Interhemispheric lipomas

A

Also known as lipomas of the corpus callosum, associated with hypogensis or agenesis of the corpus callosum.

May also be evidence of punctate or curvilinear midline calcifications or the presence of other anomalies such as encephaloceles and cutaneous lipomas

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32
Q
A

Interhemispheric lipoma

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33
Q
A

Quadrigeminal plate lipoma

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34
Q
A

Interpeduncular lipoma

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35
Q

Def: Cephalocoele

A

Skull base or calvarial defect assocaited with herniaton of intracranial defects

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36
Q

Aetiology of cephalocoeles

A

Skull base cephalocoeles are defects of enchondral bone- defects in induction of bone or disunion of basilar ossification

Calvarial- defects of membraneous bone either caused by defect of bone induction or mass effect and pressure erosion by an expanding intracranial lesion or failure of neural tube closure.

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37
Q

Most common locations of cepalocoeles

A

Occipital

Frontoemthmoidal

Parietal

Nasopharyngeal

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38
Q

Associations with occipital cephalocoele

A

Callosal anomalies

Anomalies of neuronal migration

Chiari malformation

Dandy-Walker

Poor Px include HCP, microcephaly, meningoencephalocoele

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39
Q

Which type of cephaloceole has least favourable prognosis

A

Occiptal

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40
Q

Frontoethmoidal cephalocole

A

Results from failure in normal regression of dura that extends from cranial cavity to the skin through persistent foramen caecum or fonticulus frontalis

Persistence may give a dermal sinus tract which can give rise to dermoid or epidermoid tumour

Examination reveals superficial skin-covered mass or nasal dimple with hypertelorism

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41
Q
A

Frontoethmoidal cephalocoele

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42
Q

Subtypes of frontoethmoidal cephalocoele

A

Frontnasal ephalocle

Frontoethmoidal cephalocoele

naso-orbital cephalocele

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43
Q

Parietal cephalocel

A

Uncommoon

Poor prognosis as commonly associated with major anomalies including Dandy-Walker, callosal agensis, Chiari II and holoprosencephaly

SSS involvement is common

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44
Q

Atretic cephaloclee

A

Small, hairless, midline masses associated with sharply marginated calvarial defect and high incidence of midline anomalies e.g. porencephalies, interhemispheric cysts and callosal agenesis

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45
Q

Nasopharyngeal cephalocele

A

Very uncommon

Occult, often not presenting until 10y/o where patient presents with nasal sutffiness of excessive mouth breathing

O/E: Nasopharyngeal mass that increases with Valsalva.

Associated with callosal agensis and may include tethering of hypothalmaus and optic chiasm resulting in endocrine and visual dysfunction

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46
Q

Dermal sinus

A

3-5th week

Defect in separation of neuroectodem from surface ectoderm

Sinus commonly contains elements of both dermal and epidermal tissue

Midline found anyway between nasion and coccyx but commonly between the glabella andanion

May have associated cysts along tract

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47
Q
A

Dermal sinus

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48
Q

Clinical presentation of dermal sinus

A

Benign cutaneous cosmetic blemish to serious intracranial infection or tumourlike process due to mass effect from dermoid or epidermoid cyst

May have associated angiomata, abnormalities of pigmentation, hypertrichosis, abnormal hair pattern, subcutaneous lipomata, skin tags

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49
Q

Def: Arachnoid cysts

A

CSF containing lesions covered by membranes that consist of arachnoid cells and collagen fibres that are continuous with the surrounding arachnoid.

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50
Q

Pathophysiology of arachnoid cysts

A

Anomalous splitting and duplication of endomeninx which normally forms a loose extracellular substance in the future subarachnoid space.

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51
Q

Common locations of arachnoid cysts

A

2/3rds supratentorial most commonly Sylvian cistern, others include suprasellar, interhemispheric, intraventricular

1/3rds infraentroial- divdied between CPA, posterior to vermis and superior to quadirgeminal plate

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52
Q

Presentaiton of arachnoid cysts

A
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53
Q

Grading of middle cranial fossa arachnoid cysts

A

Galassi classification

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54
Q

Galassi 1

A

Small,spindle shaped

Limited to the anterior portion of the middle cranial fossa below sphenoid ridge

Free communication with subarachnoid space

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55
Q

Galassi 2

A

Superior extent along sylvian fissure

Displacement of temporal lobe

Slow communication with subarachnoid space

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56
Q

Galassi 3

A

Large

Fills whole middle cranial fossa

Dispalcement of temporal, frontal and parietal lobes

Often results in MLS

Little communication with subarachnoid space

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57
Q

What is the exception to the inside out pattern of neuronal migration

A

The neurones that form the most superficial layer- the molecular layer which seem to migrate first

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58
Q

Anomalies as a result of defect in neuronal migration

A

Tend to cause malformations in which cortical neurones are residing in abnormal locations or patterns.

Lissencephaly

Heterotopia

Polymicrogyria

Schizencephaly

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59
Q

Lissencephaly

A

Associated with severe mental retardation

Defective migration of cerebral neurones results in failure of cortical gyri to develop.

Cerebral hemispheres are smooth with absent cortical sulci and cerebral fissures are shallow.

Microscopically aberrant cortical cell layers

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60
Q

Lissencephaly etymology

A

Derives from greek lissos- “smooth”

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61
Q

Heterotopia

A

Collections of normal cortical neurones that fail to reach the cortex as a defect in radial neuronal migration.

May occur in isolcation or in association with other brain anoamlies.

Subtypes based on location and pattern of organisation

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62
Q

Heterotopia

A

Heter- other

Topia- place

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63
Q

Subtypes of heterotopia

A

Subependymal heterotopia

Focal subcortical heterotopia

Band heterotopia

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64
Q

Normal development, normal motor function.

Onset of seizures in second decade of life

A

Subependymal heterotopia

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65
Q

Dependant on size can present with normal to severely abnormal developmental delay

Motor disturbances in association with seizure disorders

A

Focal subcortical heterotopia

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66
Q

Moderate to severe developmental delay

Medically intractable seizures

A

Band heterotopia (AKA diffuse gray matter heterotopia)

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67
Q

Polymicrogyria

A

Varaible presentation with severe motor and intellectual dysfunction dependent on the extent of cortical involvement.

Abnormal neuronal representation resulting in distribution of neuroens into abnormal multiple small gyri

May affect variable portion of cortex in one or both areas

Most common site- posterior Sylvian fissure

68
Q

With what is this abnormality closesly associated?

A

Polymicrogyria

Congential CMV infection

69
Q

Schizencephaly

A

Seizures, hemiparesis, variable developmental delay determined by location, extent and number of clefts

Abnormal development of gray matter-lined cleft within the cerebral hemisphere that may extend for part of the entir distance from pia of cortex to ependyma of lateral ventricle

Can be classified as open or close lip dependent on extension into the ventricle.

Clefts comprise cortical neurones with abnormal lamination.

Most frequently occur in the region of pre/post-central gyri and can be unilateral or bilateral

Bilateral associated with worse Px

70
Q
A

Open lip schizencephaly

71
Q
A

Closed lip schizencephaly

72
Q

Holoprosencephaly etymology

A

Holo- whole

Prosencelphaly- forebrain

I.e. condition of whole or inappropriately divided forebrain

73
Q

Holoprosencephaly

A

Group of related disorders characterised by common failure of differentiation and cleavage of the prosencephalon

74
Q

Three subtypes of holoprosencephaly

A

Alobar

Semilobar

Lobar

75
Q

Outline differentiation and cleavage of hte prosencephalon

A

D32, germinal matrix cleaves into superior and inferior portions

Superior-> telencephalon

Inferior-> diencephalon

D32-34 lamina terminalis differenitates into the interhemsipheric cerebral commissures with associated evagination and separation of the cerebral hemispheres.

Defect in this cleavage process results in failure of transverse differentaition and cleavage into telencephalon and diencephalon and failure of the lateral differentiation and cleavage of the prosencephalon into two cerebral hemispheres

76
Q

Alobar holoprosencephaly

A

Most severe form

Fused thalami with absent third ventricle

No interhemispheric fissure, falx or corpus callosum

Holoventricle contiugous with large dorsal cyst with only small rim of brain anteriorly

Associated with severe midline facial deformities, hypotelorism manifested in most severe form by cyclopia

77
Q
A

Alobar holoprosencephaly

Fused thalami with absent third

No interhemispheric fissure, falx, corpus callosum

Holoventricle continuous with large dorsal cyst

78
Q

Semilobar holoprosencephaly

A

At least partial separation of thalami

Small third ventricle

Partially formed or absent interhemispheric fissure and falx

In contrast to the normal hypogenetic corpus in which there is a normal genu and body, holoprosencephaly is the one exception which demonstrates an intact splenium but small or absent genu and body

79
Q
A

Semilobar holoprosencephaly

Partial separation of thalami with small third

Partially formed or absent interhemispheric fissure and falx

Intact splenium of corpus calosum (small or absent genu and body)

80
Q

Lobar holoprosencephaly

A

Fully formed third ventricle

Intact corpus callosum

Absent septum pellucidum

Frontal lobe hypoplasia

81
Q
A

Lobar holoprosencephaly

Mildest form

Septum pellucidum absent and frontal lobe hypoplasia

Third ventricle and corpus callosum intact

82
Q

Septo-optic dysplasia

A

Two primary features:

Hypoplasia of optic nerves

Hypoplasia or absence of septum pellicdum

Manifests as visual distrubances including nystagmus, loss of acutity, endocrine abnormalities typically involving GH and TSH

83
Q
A

Septo-optic dysplasia

84
Q

Chiari I

A

Caudal extension of cerebellar tonsils below FM

May be asymptomatic or related to symptoms secondary to syringomyelia e.g. CN palsies, dissociated sensory loss.

Headache, neck and arm pain may develop in the adult

85
Q
A

Chiari I malformation

Herniation of cerebellar tonsils below level of FM

May have associated syringomeyelia

86
Q

Chiari II

A

Complex malformation invartiably associated with myelomeningocoele and multiple other brain anomalies

May be expained by development of a normal sized cerebellum but abnormally sized post fossa with a low tentorial attachment

Infants require repair of myelomenginocoele and shunting of HCP

May have life threatening bulbar symptoms.

Apnoea, bradycardia and nystagmus is a common clinical finding

Progressive spastic weakness and appendicular ataxia may gradually .

87
Q

Cardinal features of Chiari II

A

Inferiorly displced vermis and multiple other anomalies

Associated with lacunar skull

Myelomeningocoele (100%)

Syringomyelia (50-90%)

HCP (90%)

88
Q

Brain anomalies associated with Chiari II

A

Heterotopias

Polymicrogyria

Interdigitated Gyri

Partial callosal agesnesis

Large massa intermedia

Beaked tectum

Towering cerebellum with anterior creep around brainstem

Inferiorly displaced vermis

Medullary kinking

89
Q
A

Chiari 2

90
Q
A

Lacunar skull

Seen in Chiari 2 malformation

There is a ventricular shunt system in place

haracterised by groups of round, oval or finger-shaped pits on the inner surface of the vault (membranous part), separated by ridges of bone. They lie in the thickest part of the frontal, parietal, and upper occipital bones.

Different to copper beaten skull whcih is due to pressure, this is through defective ossificaiton

91
Q
A

Copper beaten skull

HCP

92
Q

Chiari III

A

Herniation of posterior fossa contents through a defect at C1-2 level (low occipital/high cervical (en)cephalocoele)

Syrinx

Rarely compatible with life

93
Q

Who was Chiari?

A

Hans Chiari, Austrian pathologist

94
Q
A

Chiari 3

95
Q

Dandy Walker Malformation

A

Enlarged posterior fossa with eleveated tentorial attachment and high transverse sinus and lamboid/torcula inversion

Superior medullary velum fails to develop with foramen Magendia and Luschke atresia.

hypo or agenesis of the vermis and cystic dilatation of the fouth ventricle

Frequently accompanied by HCP (90%) of patients at time of diagnosis)

Most commonly associated with callosal agensis.

May present with developmental delay, enlarged head circumference, signs and symptoms of HCP

96
Q

DDx for Dandy Walker malformation

A

Dandy-Walker

Mega cisterna magna

Dandy-Walker variant

Post fossa arachnoid cyst

97
Q

Difference between Dandy-Walker Malformation and mega cisterna magna

A

Presence of communication between the fourth and the cisterna magna

98
Q
A

Mega cisterna magna

99
Q

Difference between Dandy-Walker and Dandy Walker variant

A

Dandy walker variant is characterised by hypogenesis of the cerebellar veris and cystic dilatation of the fourth with a normal sized posterior fossa

100
Q
A

Dandy Walker

101
Q
A

Dandy-Walker variant

102
Q

Dandy Walker Variant

A

Cerebellar vermis hypoplasia

Vallecular enlarged- open communication between 4th and cisterna magna

Normal posterior fossa

HCP in 25%

103
Q

Mega cisterna magna

A

Large cisterna magna with CSF accumulation in post fossa

Normal 4th ventricle with no HCP

Fills with intrathecal contrast

104
Q

Post fossa arachnoid cyst

A

Posterior fossa CSF accuulation with normal cerebellum and 4th

May or may not be associated with HCP

Cyst does not fill with intrathecal conrast (unlike mega cisterna magna)

105
Q

Absence of vermis

Enlarged fourth

Fills with intrathecal contrast

HCP in 85%

A

DWM

106
Q

Vermian hypoplasia

Enlarged 4th

FIlls with intrathecal contrast

HCP in 25%

A

DW variant

107
Q

Normal cerebellum

Normal 4th ventricle

Enlarged cisterna magna

Fills with intrathecal contrast

No HCP

A

Mega cisterna magna

108
Q

Normal cerebellum

Enlarged cisterna magna

Normal fourth

Doesn’t fill with intrathecal contrast

+/- HCP

A

Post fossa arachnoid cyst

109
Q

Lhernitte-Duclos Syndrome

A

AKA diffuse hypertrophy of cerebellar cortex/dysplastic cerebellar gangliocytoma

Histologically cortex demonstrates a thick layer of abnormal ganglion cells that occupy the granulary, thick hypermyelinated marginal layer and thin Purkinje layer

Disorder may extend into the vermis or the contralateral hemisphere

Mass effect may produce cerebellar symptoms but many affected individuals are asymptomatic

110
Q
A

Lhermitte-Duclos disease

111
Q

Common defect in phakomatoses

A

Share a common defect in the development of ectodermal structures including nervous, structures, skin, retina.

112
Q

4 major phakomatoses

A

NF

TS

Sturge-Weber

VHL

113
Q

Major intracranial lesions associated with NF1

A

Optic glioma

Cerebral astrocytomas

Sphenoid wing dysplasia

Plexiform neurifbromas

114
Q

Bourneville’s disease

A

Tuberous sclerosis

115
Q

Tuberous Sclerosis

A

Triad of mental retardation, epilepsy and adenoma sebaceum though only present in half of patients

Predominantly consists of hamartomatous lesions involving brain, eye, visceral organs

116
Q

Cutaneous manifestations of tuberous sclerosis

A

ADenoma sebaceum- adenoma involving face

Ash leaf macules- depigmented naevi involving trunk and extrimities

Shagreen patches

117
Q
A

Adenoma sebaceum

?Tuberous sclerosis

118
Q
A

Ashleaf macules ?tuberous sclerosis

119
Q
A

Shagreen patch

120
Q

Cranial lesions associated with tuberosu sclerosis

A

Subependymal hamartomas

Giant cell tumours

Cortical tubers

WM lesions

121
Q

Systemic lesions associated with tuberous sclerosis

A

Hamartomatous lesions involving kidneys- angiomyolipoma

Heart- rhabdomyoma

Lungs- lymphangiomyoma

Eye- retinal hamartoma

122
Q
A

Tuberous sclerosis: T1-weighted FLAIR images reveal cerebral hamartomas as low signal intensity subcortical lesions, subependymal hamartomas casted on the ventricular space and small giant cell astrocytomas adjacent to the foramen of Monro.

123
Q
A

Cortical tubers

124
Q

Most common brain lesion associated with tuberous sclerosis

A

Subepednymal hamartomas

125
Q

How to differentiate between subependymal hamartomas and subependymal giant cell tumours

A

Giant cell tumours tend to have intense contrast enhancement on MR

Are larger

Tend to more frequently occur near the foramen of Monro which can cause non-communicating HCP

126
Q

Cortical tubers

A

Characteristic hamartomas mae of bizarre giant cells, fibrillary gliosis and siorderd myelin sheaths which appear as smooht, slightly raised subcortical nodules

127
Q

Sturge Weber Syndrome

A

ANgiomatosis involving face, choroid of eye and leptomengines

Facial angioma follows the opthalmic division of V.

Localised atrophy and caclification of the cerebral cortex ipsilateral to facial lesion is characteristic.

128
Q
A

Retinal hamartoma

129
Q
A

Sturge Weber Syndrome

130
Q

Clinical presentation of Sturge Weber

A

Seizures

HH

Variable mentral retardation

131
Q

VHL

A

AD characterised by

CNS:

retinal angiomas, cerebellar and spinal cord haemangiobolastomas

Systemic:

RCC, phaeo, angiomas of liver and kidney and pancreatic, kidney, liver, epidiymal cysts

132
Q

Genetic basis for VHL

A

Autosomal dominant on chromosome 3

133
Q
A

Retinal angioma

134
Q

Most common location of spina bifida occulta

A

L5 and S1 vertebral arches

135
Q

Spina bifida oculta

A

Radiological diagnosis without external signs of developmental anomlay

Characterised by absence of one or more spinous process with associated vertebral arch hypogenesis

20-30% incidence in general population

136
Q

Meningocoele

A

Ctystic skin or membrane covered mass consisting of a meningeal sac containing onle CSF that is continuous with the CSF of the spinal canal.

137
Q

Pathophysiology of meningocoele

A

Aetiology unclear, malformation appears to represent a postneurulation defect developing after the normal disjunction of neuroectoderm from cutaneous ectoderm.

Thought to result from defect in mesenchymal and cutaneous ectodermal development.

Myelomenginoceole is a true defect in neurulation

138
Q

Pathophysiology of myelomeningocoele

A

Defect in disjunction where the neuroectoderm and cutaneous ectoderm separatae

Results in neural placode made of cells that would normally form ependymal lining of neural tube.

Because the placode remains attached to the skin, the mesenchymal elements are unable to migrate and fuse leading to several vertebral anomalies.

139
Q

Vertebral anomalies in myelomeningocoele

A

Absence of spinous processes and laminae

Reduction in AP size of vertebral bodes

Increased interpedicular distance

Large laterally extending transverse processes

May contribute to kyphoscoliotic deformities in 1/3rd

140
Q

Sequelae from myelomeningocoele

A

Chiari (100%)

HCP

Tethered SC

141
Q

Myelomenginoceole avove L3

A

Complete paraplegia

Dermatomal para-anaesthesia

Bladder/rectal incontinence

Nonambulatory

142
Q

Myelomeningocoele L4 and below

A

Manifestation as for L3 except preservation of hip flexors, abductors and knee extensors

Ambulatory with aids, bracing and orthopaedic surgery

143
Q

Myelomeningocoele S1 and below

A

As for L4 except with preservation of feet dosriflexors and partial preservation of hip extensors and knee flexors

Ambulatory with minimal aids

144
Q

Myelomeningoceole S3 and below

A

Normal lower extremity motor function

Saddle anaesthesia

Varaible bladder/rectal incontinence

145
Q

Spinal lipoma

A

Skin-covered dorsal masses of fat and connective tissue in continuity with leptomeninges or spinal cord

Result of premature disjunction which results in migration of mesenchymal tissue into the ependymal lined central canal of the neural tube, differenitates into fat due to connection with central canal of neural tube

146
Q

Categories of spinal lipoma

A

Intradural (4%)

Lipomyelomeningocoeles (84%)

Fibrolipomas of filum terminale (12%)

147
Q

Intradural lipomas

A

Commonly occur in thoracic region

PResent with signs and symptoms of cord compression in the adult

148
Q
A

T1 saggital MR thoracic spine

Intradural thoracic lipoma

149
Q

Fibrolipomas of filum terminale

A

Take origin from an abnormality in caudal cell mass during secondary neurulation

Asymptomatic but may present with symptoms of tethered cord

150
Q
A

Fibrolipoma of the filum terminale

151
Q

Lipomyelomeningocoeles

A

Present as subcutaneous, skin covered lumbosacral masses.

Most common form of spinal lipomas

Extend beyond the dorsal surface of the neural placode through spina bifida.

At the level of the lipoma, the dura is deficient in the dorsal midline, allowing free medial edges to attach to the neural placode which is extradural as a consequence

152
Q

Describe the orientation of the neural placode in lipomyelomeningoceoele

A

As the neural placode herniates through the bony spina bifida, it rotates.

This places the dorsal surface of the neura placode laterally or dorsolaterally rather than straight dorsally.

The nerve roots on each side assume asymmetric lengths such that those on superficial side grow longer than those on deep.

The shorter roots may result in inferior tethering of the spinal cord

153
Q

Differnce between myelomenginocoele and lipomyelomeningocoele

A

Lipomyelomengincoele is skin covered, marked by a lipoma attached to the dorsal surface of the placode

154
Q
A

Lipomyelomeningoceoele

155
Q

Common associations with lipomyelomeningoceole

A

Orthopaedic foot deformities

Sacral anomalies

Segmentation anomalies

156
Q

Anatomical definitiion of split cord

A

Fissure separating spinal cord >=1 segements +/- bony spicule/ fibrocartilaginous septum from dorsul VB

Each hemicord contains own set of roots.

May have separate or shared dural sleeve which predicts absence of bony septum

157
Q

Type 1 diastomatomyelia

A

duplicated dural sac

hydromyelia common

midline spur often present (osseous or osteocartilaginous)

vertebral abnormalities: hemivertebrae, butterfly vertebrae, spina bifida, fusion of laminae of adjacent levels

skin pigmentation, haemangioma and hypertrichosis (hair patch) are common

patients are usually symptomatic presenting with scoliosis and tethered cord syndrome

158
Q

Diastematomyelia type:

duplicated dural sac

hydromyelia common

midline spur often present (osseous or osteocartilaginous)

vertebral abnormalities: hemivertebrae, butterfly vertebrae, spina bifida, fusion of laminae of adjacent levels

skin pigmentation, haemangioma and hypertrichosis (hair patch) are common

patients are usually symptomatic presenting with scoliosis and tethered cord syndrome

A

Type 1

159
Q

Type 2 diastomatomyelia

A

single dural sac and no spur/septum

cord divided, sometimes incompletely so

hydromyelia may be present

spina bifida may be present, but other vertebral anomalies are far less common

patients a less symptomatic or may even be asymptomatic

160
Q

Diastomatomyelia type

single dural sac and no spur/septum

cord divided, sometimes incompletely so

hydromyelia may be present

spina bifida may be present, but other vertebral anomalies are far less common

patients a less symptomatic or may even be asymptomatic

A

Type 2

161
Q
A

Diastomatomyelia Type 1

162
Q
A

Diastomatomyelia Type 2

163
Q

Assocoations with diastomatomyelia

A

Cutaneous manifesations- naevia, hypertrichosis, lipomas, dimples, haemangiomas in >50%

Orthopaedic foot problems

Neurological symptoms 2o to cord tethering

164
Q

Caudal agensis

A

Group of caudal malformations demonstrating partial or complete absence of either or both lumbar and sacral vertebra with absence of corresponding neural tube.

Can include hemivertebrae, wedge shaped vertebrae, fused vertebrae, sacralisation of lumbar vertebraie

Distal SC absent and terminus of remaining cord ends in dyspplastic glial nodule.

Motor deficits correspond to level of lesion, sensory defects may be absent due to sparing of neural crest cells.

50% have myelomeningocoeles

165
Q

Associations with caudal agenesis

A

Limb malformations- flattend buttocks, gluteal atrophy, equinvoarous defomities

Visceral malforamtions: Tracheo-oesophageal fistula, Meckel’s diverticulum, cloacal estrophy, omphalocoele, malrotation, renal agenesis, horeshoe kidney, uretral and bladder duplications, anomalies of external genitalia

166
Q
A

Caudal agenesis

Neuroanatomy (18 decks)

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