17 Primary craniospinal anomalies Flashcards

1
Q

What proportion of Chiari 1 malformations are associated with a syrinx?

A

30-70%

Guinto G et al. 2004 Part 1 Contemp Neurosurgery

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2
Q

What proportion of patient with Chiari 1 and syrinx have hydrocephalus?

A

7-9%

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3
Q

What proportion of patients with Chiari 1 are asymptomatic?

A

15-30%

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4
Q

What abnormalities of the C-spine are associated with Chiari 1?

A

anterior indentation at FM e.g. Basilar invagination
Klippel-Feil
occipitalisation of atlas
hypermobility of craniocervical junction

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5
Q

What is the commonest presenting symptom in Chiari 1 malformation?

A

Pain (69%)

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6
Q

What is the most characteristic finding on eye examination in Chiari?

A

Downbeat nystagmus

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7
Q

What are the 3 main patterns of signs?

A

foramen magnum compression syndrome (22%): ataxia, corticospinal and sensory deficits, cerebellar signs, lower cranial nerve palsies. 37% have severe H/A

central cord syndrome (65%): dissociated sensory loss (loss of pain & temperature sensation with preserved touch & JPS), occasional segmental weakness, and long tract signs (syringomyelic syndrome). 11% have lower cranial nerve palsies

cerebellar syndrome (11%): truncal and limb ataxia, nystagmus, dysarthria

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8
Q

How much herniation is most often cited to diagnose chiari 1?

A

5mm. Although this is not diagnostic nor essential.

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9
Q

What is meant by Chiari zero malformation?

A

Patients with syringohydromyelia without hindbrain herniation that responded to p-fossa decompression

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10
Q

Which patients are most likely to benefit from surgical intervention in Chiari 1?

A

Cerebellar syndrome responds well, as do headaches.

Symptoms lasting less than 2 years also do better than those that are >2 years

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11
Q

What features are associated with Type 2 (Arnold)-Chiari malformation?

A
Myelomeningocoele (almost always)
hydrocephalus
Beaking of tectum
enlarged interthalamic adhesion (massa intemedia)
low attachment of tent
syringomyelia
bony abnormalities 
    - platybasia
   - Klippel-Feil
   - assimilation of atlas
 microgyria
hypoplasia of falx
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12
Q

What are the recommended indications for post fossa decompression in Chiari 2?

A

Neurogenic dysphagia
Stridor
Apneic spells

Always make sure patient has a working shunt first!

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13
Q

What is the commonest cause of mortality in Chiari 2?

A

Respiratory arrest.

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14
Q

What is the Lemire Classification?

A

Proposed classification system for neural tube defects - splitting them into neurulation (open) and post neurulation (closed)

neurulation defects = non closure of neural tube e.g. craniorachischisis, anencephaly or myelomeningocoele in the spine.

post neurulation (migration disorders) e.g. microcephaly, hydranencephaly, lissencephaly, porencephaly, diastematomyelia, diplomyelia, syringomyelia, DWM

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15
Q

What are the different forms of lissencephaly?

A

agyria: completely smooth surface
pachygyria: few broad & flat gyri with shallow sulci
polymicrogyria: small gyri with shallow sulci. May be difficult to diagnose by CT/MRI, and may be confused with pachygyria

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16
Q

What are the different forms of migration defect?

A

Lissencephaly
Heterotopia
Cortical dysplasia
Schizencephaly

17
Q

What are the 2 different forms of schizencephaly?

A

can be open lipped or closed lipped.

18
Q

How do you differentiate between schizencephaly and a porencephalic cyst?

A

in Schizencephaly wall of the cyst is lined with cortical grey matter (usually abnormal, may have polymicrogyria)

19
Q

What classically causes hydranencephaly?

A

Bilateral ICA infarcts

20
Q

How can you differentiated between hydranencphaly and hydrocephalus?

A

EEG - No cortical activity in hydranencephaly
MRI/CT/US
Angiography

21
Q

What causes cyclopsia

A

severe holoprosencephaly

22
Q

What is holoprosencephaly associated with?

A

80% association with a trisomy (predominantly 13 and to a lesser extent trisomy 18)

23
Q

What happens embryologically in holoprosencephaly?

A

Telencephalic vesicle fails to fully cleave into 2 hemispheres.

24
Q

What is MCAP?

A

megalencephaly-capillary malformation syndrome (MCAP): an overgrowth syndrome with megalencephaly (often with hydrocephalus, Chiari malformation, polymicrogyria and seizures) and capillary malformations in the skin (usually on the face)

25
Q

What are the risk factors for development of NTD?

A

folate deficiency, Cocaine, heat in 1st trimester, obesity, valproic acid

26
Q

What is a neuroenteric cyst?

A

CNS cyst lined by epithelium resembling that of the GI, or less often, respiratory tract.

27
Q

Where in the CNS are you most likely to have a neuroenteric cyst?

A

Lower cervical/upper thoracic spine

28
Q

What is the mechanism of forming a neuroenteric cyst?

A

occurs as a result of persistence of the neuroenteric canal (temporary duct between the notochord and the primitive gut (amniotic and yolk sacs) formed during week 3 of embryogenesis by breakdown of the floor of the notochordal canal).

29
Q

Where are intracranial neuroenteric cysts likely to be found?

A

P-fossa (CPA, Midline anterior to brainstem or cisterna magna)

30
Q

supratentorial NEC, colloid cysts and Rathke’s may all arise from what?

A

remnants of Seesel’s pouch - a transient endodermally derived diverticulum of the cranial end of the embryonic foregut