17 Primary craniospinal anomalies Flashcards
What proportion of Chiari 1 malformations are associated with a syrinx?
30-70%
Guinto G et al. 2004 Part 1 Contemp Neurosurgery
What proportion of patient with Chiari 1 and syrinx have hydrocephalus?
7-9%
What proportion of patients with Chiari 1 are asymptomatic?
15-30%
What abnormalities of the C-spine are associated with Chiari 1?
anterior indentation at FM e.g. Basilar invagination
Klippel-Feil
occipitalisation of atlas
hypermobility of craniocervical junction
What is the commonest presenting symptom in Chiari 1 malformation?
Pain (69%)
What is the most characteristic finding on eye examination in Chiari?
Downbeat nystagmus
What are the 3 main patterns of signs?
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
How much herniation is most often cited to diagnose chiari 1?
5mm. Although this is not diagnostic nor essential.
What is meant by Chiari zero malformation?
Patients with syringohydromyelia without hindbrain herniation that responded to p-fossa decompression
Which patients are most likely to benefit from surgical intervention in Chiari 1?
Cerebellar syndrome responds well, as do headaches.
Symptoms lasting less than 2 years also do better than those that are >2 years
What features are associated with Type 2 (Arnold)-Chiari malformation?
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
What are the recommended indications for post fossa decompression in Chiari 2?
Neurogenic dysphagia
Stridor
Apneic spells
Always make sure patient has a working shunt first!
What is the commonest cause of mortality in Chiari 2?
Respiratory arrest.
What is the Lemire Classification?
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
What are the different forms of lissencephaly?
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