Congenital 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)
2
Q
What proportion of patient with Chiari 1 and syrinx have hydrocephalus?
A
7-9%
3
Q
What proportion of patients with Chiari 1 are asymptomatic?
A
15-30%
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
5
Q
What is the commonest presenting symptom in Chiari 1 malformation?
A
Occipital headache (69%)
6
Q
What is the most characteristic finding on eye examination in Chiari?
A
Downbeat nystagmus
7
Q
What are the main signs associated with Chiari 1?
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
Hydrocephalus and raised ICP
8
Q
How much herniation is most often cited to diagnose Chiari 1?
A
5mm. Although this is not diagnostic nor essential.
9
Q
What is meant by Chiari zero malformation?
A
Patients with syringohydromyelia without hindbrain herniation that responded to p-fossa decompression
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
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 / torcula
Syringomyelia
Bony abnormalities - platybasia - Klippel-Feil - assimilation of atlas microgyria
Hypoplasia of falx
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!
13
Q
What is the commonest cause of mortality in Chiari 2?
A
Respiratory arrest.
14
Q
What is the Lemire Classification?
A
Proposed classification system for neural tube defects - splitting them into pre neurulation (open) and post neurulation (closed) 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
15
Q
What are the different forms of lissencephaly?
A
Agyria: completely smooth surface
Pachygyria: few broad and flat gyri with shallow sulci
Polymicrogyria: small gyri with shallow sulci. May be difficult to diagnose by MRI and may be confused with pachygyria
16
Q
What are the different forms of migration defect?
A
Lissencephaly
Heterotopia - arrest of radial migration
Cortical dysplasia - a deep cleft that doesn’t communicate with the ventricle
Schizencephaly - cleft that communicates with the ventricle
17
Q
What are the 2 different forms of schizencephaly?
A
Open lipped - communicates with cortical surface
Closed lipped - outpouching from the ependyma that does not communicate with cortical surface
18
Q
How do you differentiate between schizencephaly and a porencephalic cyst?
A
InSchizencephaly the wall of the cyst is lined with cortical grey matter (usually abnormal, may have polymicrogyria), porencephalic cysts are lined by white matter.
19
Q
What classically causes hydranencephaly?
A
Bilateral ICA infarcts (post neurulation defect)
20
Q
How can you differentiated between hydranencphaly and hydrocephalus?
A
EEG - No cortical activity in hydranencephaly
MRI/CT/US - loss of anterior circulation but PCA distribution intact
Angiography - confirms no flow from ICAs bilaterally
21
Q
What causes cyclopsia?
A
severe holoprosencephaly - failure of the telencephalic vesicle to cleave into two hemispheres
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
What are the risk factors for the development of NTDs?
Folate deficiency, Cocaine, Heat in 1st trimester, Obesity, Valproic acid
26
What is a neuroenteric cyst?
CNS cyst lined by epithelium resembling that of the GI, or less often, respiratory tract.
27
Where in the CNS are you most likely to have a neuroenteric cyst?
Lower cervical/upper thoracic spine
28
What is the mechanism of forming a neuroenteric cyst?
As a result of the persistence of the neuroenteric canal, a temporary duct between the notochord and the primitive gut (amniotic and yolk sacs) formed during week 3 of embryogenesis by the breakdown of the floor of the notochordal canal.
29
Where are intracranial neuroenteric cysts likely to be found?
P-fossa (CPA, Midline anterior to brainstem or cisterna magna)
Supratentorial locations are mainly suprasellar
30
Supratentorial neurenteric cysts, colloid cysts and Rathke's may all arise from what?
Remnants of Seesel's pouch - a transient endodermally derived diverticulum of the cranial end of the embryonic foregut
31
How would you investigate a patient with a Chiari 1 malformation?
MRI brain - tonisillar decent, brain stem compression, hydrocephalus, empty sella, associated conditions
MRI C- spine for syrinx and bony abn; CISS sequence for arachnoid web
CT skull base for posterior fossa volume, assimilation and skull base abn (platybasia etc)
Cine MRI - demonstrates CSF flow at FM
(CT myelogram if a contraindication to MRI)
32
What is the most commonly performed condition for Chiari 1?
Posterior fossa decompression through suboccipital craniectomy and C1 laminectomy
Size of craniectomy should be 3cm x 3cm. If too large causes cerebllar ptosis (sagging).
Y-shaped durotomy (note the torcula may be low!)
+/- dural expanstion graft
+/- tonsillar bipolar / adhesiolysis
33
What are craniolacunia?
Rounded defects in the skull associated with sharp borders. Found in Chiari 2. Not associated with hydrocephalus.
34
What is the outcome of p-fossa decompession for Chiari?
70% near resolution of symptoms; 20% no difference
35
What is Chiari 1.5?
Severe case of Chiari 1 with obex below the FM. Associated with platybasia.
36
What is Chiari 3?
Controversial if exists but is cerebellar herniation with occipital encephalocele.
37
What is Chiari 4?
Cerebellar hypoplasia with small p-fossa.
38
How would you perform an FMD?
Informed Consent
GA / Prone / Mayfield pins / head elevated
Midline incision inion to C2
Suboccipital craniectomy 3x3 cm and C1 arch removal
USS for CSF flow.
If no flow then Y-shaped durotomy +/- expansion graft +/- adhesiolysis +/- tonsillar shrinkage
39
What happens if the suboccipital craniectomy is too large following FMD?
Cerebellar ptosis (sagging)
40
What abnormality is commonly associated with a Schizencephaly?
Absent septum pellucidum
41
What the types of holoprocencephaly?
Lobar, semi lobar and alobar
42
What is microcephaly?
Head circumferences \<2 S.D. from the mean
43
What are the causes of microcephaly?
1. Infections (TORCH / Zika etc)
2. Malnutrition
3. Toxins - maternal ETOH / Cocaine
44
What serum marker suggests the presence of a neural tube defect?
AFP. If raised at 20 weeks suggests a 250x risk of NTD.
45
What are the different types of holoprosencephaly?
Alobar - complete failure of separation with a single cerebrum
Semilobar - Frontal and parietal lobes fused but posterior interhemispheric fissure present
Lobar - Only frontal lobes fused
Syntelencephaly - Middle hemipshere fusion only
Arrhinencephaly - Absent olfactory bulbs, olfactory tracts and gyrus rectus
46
In cerebral palsy, which part of the brain is most affected?
The periventricular WM as this is a watershed area in the neonatal period due to the increased metabolic demand of myelinating white matter. Causes periventricular leukomalacia.
47
What genetic syndrome is associated with porencephalic cysts?
COL4A1 mutation. Note porencephalic cysts are lined by WM whilst schizencephaly is lined by GM.
48
What are the most common locations for arachnoid cysts?
Middle fossa (50% in the sylvian fissure), CPA (10%), suprasellar (10%) and posterior fossa (10%).
49
What are the imaging features of an arachnoid cyst?
Follows CSF on call sequences and associated with remodelling of the bone.
50
How do you manage an incidental arachnoid cyst?
MRI+C and single further f/u study in 6 months to rule out increase in size.
51
What is the aetiology of an arachnoid cyst?
Developmental splitting of the arachnoid membrane. Histologically are lined by meningothelial cells and are positive for EMA.
52
What is the incidence of arachnoid cysts?
5 per 1000 at autopsy
53
What condition are bilateral arachnoid cysts associated with?
Hurler's syndrome (mucopolysaccaridosis)
54
What is the main differential diagnosis of an arachnoid cyst?
Epidermoid (shows restricted diffusion) Porencephalic cyst (lined by WM) Schizencephaly (lined by heterotopic GM)
55
How do suprasellar arachnoid cysts present?
Endocrinopathy Developmental delay Hydrocephalus Visual loss Precocious puberty Bobble-head doll syndrome
56
What is the classification for arachnoid cysts?
Galassi classification 1 - temporal pole and communicates with subarachnoid space during cisternography. 2 - anterior 1/2 of sylvian fissure with partial communication with subarachnoid space. 3 - Involves entire sylvian fissure and shows no communication with subarachnoid space.
57
What are the treatment options for arachnoid cysts?
1. needle aspiration / burr hole drainage (high recurrence rate) 2. Craniotomy, excision of cyst wall and fenestration into basal cisterns (higher morbidity and may need a VP shunt) 3. Endoscopic fenestration 4. Cyst shunting into the peritoneum (become shunt dependent)
58
What valve should be used if shunting an arachnoid cyst?
Low pressure
59
What are the surgical approaches for drainage of a suprasellar arachnoid cyst?
Transcallosal transventricular and transcortical transventricular
60
When do the fontanelles close?
Anterior fontanelle 2-3 years Mastoid fontanelle - 1 year Posterior fontanelle 2-3 months Sphenoid fontanelle 6 months
61
When is 90% of adult head size achieved?
1 year. Full size by age 7.
62
When do mastoid air cells form?
6 years
63
What is primary craniosynostosis?
Prenatal deformity caused by suture fusion
64
What is secondary craniosynostosis?
Metabolic (Rickets), Drugs (AEDs), Haemotological (Sickle cell / thalassemia) and structural (microcephaly)
65
What are the surgical indications for multi-suture craniosynostosis?
Impedes brain growth and for raised ICP. Note 10% of single suture craniosynostosis also develop raised ICP.
66
Which craniosynostosis may result in amblyopia?
Coronal
67
What do you feel when palpating a craniosynostosis?
Ridge (except lambdoid which may be a trough)
68
What does metopic synostosis cause?
Trigonocephaly
69
What does single coronal suture synostosis cause?
Anterior plagiocephaly
70
What does bilateral coronal suture synostosis cause?
Brachycephaly
71
What does sagittal suture synostosis cause?
Scaphocephaly
72
How do you differentiate positional plagiocephaly from unilateral lamboid suture synostosis?
Position of the ear is pulled back with unilateral lamboid suture synostosis and the skull forms a trapezoid shape compared to a parallelogram that is seen with positional plagiocephaly
73
What is the most common single suture synostosis?
Scaphocephaly (sagittal suture synostosis) - 80% occur in males
74
How is Scaphocephaly (sagittal suture synostosis) treated?
Strip craniectomy with excision of the sagittal suture
75
How can Crouzon's and Apert's syndromes be distinguished?
Both cause coronal suture synostosis which is more common in females. Crouzon's is associated with midface hypoplasia whilst Apert's is associated with syndactyly.
76
What eye sign is seen with unilateral coronal suture synostosis?
Harlequin eye sign
77
How is coronal suture synostosis treated?
Suturectomy or frontal craniotomy with orbital advancement
78
What chromosome abnormality is associated with metopic synostosis?
Ch19q
79
What investigations may be performed for synostosis?
Xray, CT and Tc bone scans
80
What is the management of positional plagiocephaly?
Repositioning therapies Surgery in 20% of cases that are refractory to repositioning therapies There is no evidence for helmets but some use them
81
What mutation is found with Crouzon's and Apert's?
FGFR (autosomal dominant)
82
What is the cause of a polypoid mass in the nose of an newborn?
Encephaloceole
83
How are encephalocoeles classified?
Suwanwela and Sunwanela classification into: Occipital, cranial vault, frontoethmoidal, basal and posterior fossa.
84
What % of infants with encephaloceles develop normally?
\<5%. The more neural tissue the worse the outcome.
85
What is Dandy Walker malformation?
An enlarged posterior fossa with cerebellar hypoplasia / agenesis and cystic dilatation of the 4th ventricle (also has an enlarged cisterna magna).
86
What is a Dandy Walker variant?
When not all 3 factors for Dandy walker malformation are present e.g. posterior fossa may not be enlarged but there is dilatation of the 4th ventricle and vermian agenesis for example.
87
What is a persistent blake's pouch cyst?
Blake's pouch is a transient protrusion from the 4th ventricle through the foramen of magendie that usually regresses by 4 months gestation. The torcula is in the correct place. If persistent results in an imperforate foramen of magendie.
89
What is the differential for a posterior fossa cyst?
Dandy-walker malformation
Dandy-walker variant
Persistent blake's pouch cyst
Arachnoid cyst
Mega cisterna magna
Joubert's syndrome due to underdevelopment of the vermis
90
How can Dandy Walker malformation be distinguished from other posterior fossa cysts?
DWM has true vermian agenesis. The others just compress the vermis.
Choroid plexus is absent
91
What is PHACES syndrome?
Posterior fossa malformation
Haemangioma (craniofacial)
Arterial anomalies of the head and neck
Coarctation of the aorta / cardiac defects
Eye anomalies
Sternal cleft
92
What syndrome can Dandy walker malformations be associated with?
PHACES
93
What is the treatment for Dandy Walker Malformation?
Treatment of hydrocephalus through shunting of the posterior fossa cyst afte ruling out aqueductal stenosis
(not the lateral ventricles due to risk of upward herniation)
ETV can also be performed
94
What conditions are associated with aqueductal stenosis?
Chiari malformation and neurofibromatosis
95
What visual abnormalities are associated with papilloedema?
Visual obscurations and lack of acuity
Peripheral field cuts
Increased blind spot
96
Why is contrast given when investigating aqueductal stenosis?
To rule out tumour
97
What are the treatments for Aqueductal stenosis?
1. ETV
2. VP shunt
3. Tokildsen shunt (lateral ventricle to cisterna magna)
98
What causes callosal agenesis?
Failure of commissuration of the prosencephalon which occurs ~8 weeks gestation.
99
What is indicated by absence of the anterior CC but presence of the posterior CC?
Holoprosencephaly
100
What is Aicardi syndrome?
Agenesis of the CC
Seizures
Retardation
Retinal pigmentation
101
What conditions are associated with absence of the septum pellucidum?
Holoprosencephaly
Schizencephaly
Agenesis of the CC
CM type 2
Septo-optic dysplasia
Chronic hydrocephalus
102
Where are intracranial lipomas most commonly found?
Corpus callosum (associated with callosal agenesis)
103
What is the differential diagnosis of an intracranial lipoma?
Dermoid cyst, teratoma and germioma
104
What is the difference between a dermoid and a teratoma?
Dermoids are ectodermal in origin (predominantly skin and hair)
Teratomas are mesoderm and endoderm (predominantly fat, muscle and bone).
105
Where do hypothalamic hamartomas arise from?
The tuber cinereum
106
What are sessile hypothalamic hamartomas?
Remain within the hypothalamus (oppose to pedunculated ones which are parahypothalamic)
107
How to Hypothalamic Harmatomas present?
Precocious puberty, gelastic seziures and developmental delay
108
How are Hypothalamic Hamartomas treated?
GnRH analogues for precocious puberty
For pedunculated HH, open approaches through pterional craniotomy or LITT
109
What syndrome is associated with HH?
Pallister-Hall syndrome
110
What are the imaging features of HH?
Iso on T1 and T2 with no contrast enhancement
Lesion arising from the floor of the third ventricle
111
What is the typical location of a spinal arachnoid cyst?
Almost always dorsal. If ventral then think of neurenteric cyst or arachnoiditis
112
What are the treatment options for arachnoid cysts?
Drainage, resection, fenestration and shunting (cysto-peritoneal)
113
What is spina bifida occulta?
Congenital absence of the spinous process +/- other posterior elements with no exposure of the meninges or neural tissue. Incidence = 10%
114
What is a meningocele?
Herniation of the meninges but not neural diffuse through spinal defect
115
What is a myelomeningocele?
Herniation of the meninges and neural tissue through a spinal defect
116
When does the cranial neuropore close?
Day 25
117
When does the caudal neuropore close?
Day 28
118
What is the incidence of spina bifida (myelomeningocele)?
1 in 1,000
119
What lowers the incidence of myelomeningocele?
Folate supplementation
120
What is the incidence of hydrocephalus with myelomeningocele?
80%. Note closure of the defect converts a latent hydrocephalus to a active one as there is no other route for CSF egress
121
What allergy is commonly found in patients with myelomeningocele?
Latex allergy in 75%
122
What does the MOMS trial show?
RCT of post-natal vers Fetal closure of myelomeningocele. Fetal closure reduces the incidence of hydrocephalus from 82% to 40% and type 2 chiari. Improved mental development and motor function at 30 months with fetal repair akin to a neurological level 2 levels lower than would be seen with post-natal repair but higher risk of preterm delivery and uterine dehiscence.
124
How do you manage a fetus with spina bifida?
Measure size of defect If ruptured then start abx Cover with sterile dressing to prevent dessication Lie patient on stomach to prevent pressure on MM Closure within 24 hours
125
Following surgical closure of a myelomeningocele what are good prognostic signs?
Spontaneous movement of the LLs No chiari 2 (if present check for stridor and apnoeas) No HCP (do head USS)
126
Why do patients with sacral myelomeningocele get clawing of the feet?
As the foot intrinsics are supplied by S1-3
127
What other anomalies are associated with myelomeningoceles?
Pulmonary immaturity Bladder dysfunction (need catheterization) Scoliosis Hip and knee deformities
128
What are the key steps of a myelomeningocele repair?
1. Free the placode from the dura to avoid tethering and release the filum terminale 2. Re-approximate the placode by suturing the pia 3. Water-tight dural closure 4. Facia and skin closure
129
What happens if there are any epithelial remnants on the placode?
Dermoid cysts arise
130
What is the cause of a CSF leak after a myelomeningocele repair?
Hydrocephalus
131
What is the most important factor to rule out when a patient with a myelomeningocele deteriorates?
Shunt malfunction
132
What is the benefit of detethering the cord during myelomeningocele repair?
May improve scoliosis
133
What is the main cause of mortality in patients with myelomeningocele?
Complications associated with the Chiari 2 malformation - aspiration / respiratory arrest etc and shunt failure
134
What are the 3 important spinal dysraphisms associated with lipoma?
Intradural lipoma Lipomyelomeningocele Lipoma of the filum terminale These all occur due to early (premature) dysjunction
135
What is the embryological cause of myelomeningoceles?
Non-dysjunction (which is part of primary neurulation)
136
What proportion of myelomeningocele patients become ambulatory?
50-80% with bracing
137
What are the cutaneous stigmata associated with spina bifida?
Fatty pads, port-wine stains, hair tuft, dermal sinus opening or skin appendages
138
What embyrological process causes a dermal sinus?
Failure of dysjunction
139
What types of cysts are associated with dermal sinuses?
Epidermoid or Dermoid depending on the contents
140
What is the difference between an epidermoid and a dermoid?
Epidermoids contain epithelium, Dermoids contain skin and hair.
141
When should dermal sinuses be excised surgically?
When above the lumbosacral region; Coccyx sinuses do not need to be treated unless infections occur.
142
What is the management of dermal sinuses?
Surgical exploration and full excision prior to neurological deficit or infection (as they cause recurrent meningitis)
143
What is Klippel-Feil syndrome?
Congenital fusion of two or more cervical vertebrae
144
What causes Klippel-Feil syndrome?
Failure of the normal segmentation of cervical somites between weeks 3-8.
145
What is the clinical triad of Klippel-Feil syndrome?
1. Low posterior hair line 2. Short neck 3. Limited neck movement (affects rotation more)
146
What is Sprengel's deformity?
Raised scapula due to failure to descend to normal position (assoc with Klippel-Feil)
147
What is tethered cord syndrome?
Abnormally low conus (below L2) - assoc with short thickened filum (\>2 mm) or intradural lipoma
148
What are the causes of worsening symptoms with MM?
Shunt faliure! Consider tethered cord if painful and syringomyelia if painless
149
How do tethered cords present?
May be asymptomatic, pain, foot deformities, scoliosis, leg weakness, urological symptoms and cutaneous stigmata
150
How can the filum be differentiated from a nerve root?
Tortuous vessel on the surface of the filum and white appearance.
151
What are the types of spilt cord malformation?
Type 1 - two hemicords, each with its own central canal, pia and dura. Have a bony septum. Treated by untethering the cord after removing any bony septums and reconstituting a single tube. Type 2 - two hemicords within a single dural tube separated by a fibrous medial septum
152
What is the Cannon's classification for congenital nerve root anomalies?
1 - conjoined roots (2 nerve roots within a common dural sheath) 2 - 2 nerve roots exiting through the same foramen 3 - Adjacent nerve roots are separated by an anastomosis
153
What is Ecchordosis physaliphora?
Notochordal remnant found in 1-2% of autopsies in the retroclival region. Focal gelatinous mass. Indistinguiable from chrodomas.
154
How would you counsel a mother with an antenatal diagnosis of myelomeningocele?
The mother should be informed of the implications of the diagnosis and immediate and long-term consequences. These include:
The mode of delivery (C-section \> vaginal)
Uncertain nature of the deficit
Early closure required within 12-24 hours - risk of CSF leak, meningitis 5%, wound breakdown 10% and dermal inclusion cyst 1%.
The potential need for VP shunt (80%)
Association with Chiari, syrinx, scoliosis, lower limb deformities and bowel/bladder dysfunction
Association with other intracranial abnormalities e.g. callosal agensis
155
How do you nurse a patient with a myelomeningocele?
Take a picture, nurse prone and cover the defect with moist sterile gauze and wrap in cling film
Start IV antibiotics
156
If a child is born with a myelomeningocele, what is the risk for future pregnancies?
The genetic component of the disease accounts for 10% risk for future pregnancies. Folic acid supplementation reduces the subsequent risk.
157
What are the causes of delayed deterioration following myelomeningocele repair?
Hydrocephalus / Shunt malfunction
Tethered cord
Chiari malformation
Syrinx
158
What investigations of bladder function can you perform in children?
Urodynamics (measures flow rate and bladder residual)
Micturating cystourethrogram
Sphincter EMG
159
What does a high arched foot (pes cavus) suggest?
Weakness of the intrinsic muscles of the foot which are supplied by S1/2 roots. Chronic denervation results in pes cavus.
160
What do the combination of pes cavus and sphincter disturbance suggest?
Dysfunction of the sacral nerve roots (S2)
161
What embryological failure results in myelomeningocele?
Failure of dysjunction
162
What is an LDM?
Limited dorsal myeloschisis, characterised by a fibroneural stalk. If the stalk is mainly fibrous then it is a dermal sinus tract. Note myeloschisis means a flat placode that failures to form a tube.
163
What surgery is performed for tethered cord with progressive weakness?
Spinal cord untethering and release of the filum terminale (which connects the conus to the sacral haitus). Tethering symptoms are unlikely to get worse after the person stops growing.
