This document provides an overview of various cystic diseases of the central nervous system from a surgical perspective. It discusses the classification, epidemiology, diagnosis and management of different types of CNS cysts including arachnoid cysts, neurenteric cysts, colloid cysts, epidermoid cysts, pineal cysts, and cystic lesions caused by conditions like neurocysticercosis. The document emphasizes the importance of imaging and histopathology in diagnosing cystic diseases and outlines surgical and medical treatment approaches depending on the specific cyst and whether it is causing symptoms.

1. CYSTIC DISEASE OF CNS: SURGICAL
PERSPECTIVE
By Dr. Mestet Y (Neurosurgery resident)
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2. Outline
• Introduction
• Epidemiology
• Classification
• Specific CNS cysts & their Management
• Summary
• References
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3. Introduction
• CNS cysts are spectrum of lesions that
occupies space in the CNS.
• Clinical presentation depends on the
location & size and mimic tumors.
• The age, site, cyst wall & cyst content
provides an insight to its origin.
• Clinical exam & imaging is important.
• Histopathology is the gold standard to its
dx.
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4. Epidemiology
• 76% are neoplastic while 24% are non
neoplastic.
• Most non neoplastic lesions are cysts.
• Metastasis & arachinoid cysts are the most
common neoplastic & non neoplastic ICSOL
respectively.
• Cysts of CNS are usually benign.
• Intracranial cysts > intra spinal cysts.
• Infectious CNS cysts are more common in
developing countries.
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5. Classification
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6. Arachnoid cysts (leptomeningeal cysts)
• Congenital lesions that arise from splitting of arachnoid
membrane.
• Do not communicate with ventricles or subarachnoid
space.
• Almost all occur in relation to an arachnoid cistern
(exception: intrasellar, the only one that is extradural
• ≈ 1% of intracranial m asses.
• Bilateral arachnoid cysts m ay occur in Hurler
syndrome (a mucopolysaccharidosis).
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7. Location
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8. Clinical features
Most are asymptomatic (incidental finding)
except in the suprasellar region
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9. Diagnosis
• CSF density
Hyperdense, if intracyst hemorrhage (rare)
May expand, thin/remodel bone
• Doesn't enhance
CTA: Posterior displacement of MCA in MCF Acs
• CT: Cisternography may demonstrate
communication with subarachnoid space
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10. Mgt
• For asymptomtic: follow -up imaging every 6–
8 months regardless of their size and location.
• For mass effect or symptomatic : Surgery
Options:
drainage by needle aspiration
Cyst wall fenestration it into basal cisterns
shunting of cyst into peritoneum
cystectomy
percutaneous ventriculo-cystostomy
ventricular drainage is ineffective. why? 1011/26/2020

11. Spinal arachnoid cysts
• Almost always dorsal
• most common in thoracic spine.
• Most are extradural aka arachnoid diverticula
• congenital or may follow infection or trauma.
• Usually asymptomatic, even if large.
Treatment: When symptomatic
1. percutaneous procedures: under MRI1 or CT guidance.
a) needle aspiration
b) needle fenestration
2. open surgical resection or fenestration
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12. Dilated Virchow-Robin(
Giant Perivascular) Spaces
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13. Neurenteric (enterogenous) cyst (NEC)
• a result of Congenital persistence of the
neurenteric canal (temporary duct b/n notochord
& primitive gut).
• lined by endothelium primarily resembling that of
the GI tract, or less often, respiratory tract.
• Intraspinal > intracranial (most common at
thoracic).
• Intradural intramedullary & Ventral in location.
• Spinal NEC may be associated endodermal sinus
cysts: spinal meningitis
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14. Intracranial neurenteric cysts
• Rare, most common in p-fossa.
• Locations:
1. posterior fossa
a) cerebellopontine angle (CPA): usually
intradural, extraaxial
b) in midline anterior to brainstem
c) cisterna magna
2. supratentorial: suprasellar (possible
confusion with Rathke’s cleft cyst).
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15. Diagnosis
• A midline mass in front of the brain stem/
spinal cord that is slightly hyperdense/intense
to CSF is NEC.
• Morphology: Smooth, lobulated, well-
demarcated.
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16. Treatment
Surgery: if symptomatic
Spinal NEC
• surgical removal usually reverses the symptom s.
• Recurrence is uncommon with complete removal.
Intracranial NEC
• complete resection or marsupialization if capsule
adherent to brainstem
Outcome : good but Incomplete removal has
recurrence & requires long-term follow-up.
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17. Rathke’s cleft cyst (Cystic Pituitary
Adenoma) (RCC)
• are nonneoplastic lesions that are thought to
be remnants of Rathke’s pouch.
• primarily intrasellar with /without suprasellar
extension.
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18. Diagnosis
• Rule of thumb: a lesion with a nodule in the
sella is usually a RCC.
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19. Cont’d
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20. Colloid cyst
• slow-growing benign tumor comprising < 1%
of intracranial tumors
• Usual age of diagnosis: 20–50 yrs.
• Cells of origin: unknown
• classically occurs in the anterior 3rd ventricle,
blocking foramina of Monro →obstructive
hydrocephalus involving only the lateral
ventricles (≈ pathognomonic)
• enhances minimally or not at all on CT/MRI
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21. Diagnosis
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22. Natural history
• incidence of being symptomatic
at 5 & 10 yr follow up: 0% & 8% respectively.
• ≈90% unchanged cyst or ventricular size.
• risk of sudden death(due to cardiovascular
instability from hypothalamic compression)
:controversial
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23. Treatment decision
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24. Cont’d
Surgical options
• Shunt vs surgical resection:
• Currently, direct surgical preferred
1. to prevent shunt dependency
2. to reduce the possibility of progression
3. to void sudden neurologic deterioration
• Approach: transcallosal,
transcortical/transventricular
(only if hydrocephalus), ventriculoscopic ,
stereotactic
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25. Epidermoid and dermoid cysts
Etiology
 Developmental : Sequestration of surface
ectoderm at lines of two fusing ectoderm.
 Acquired: trauma, surgery, LP
• Linear growth rate: like skin unlike neoplasm.
• Dermoids are predominantly intraspinal in
contrast to epidermoid cysts.
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26. Location & clinical feature
• intracranial:
a) suprasellar: bitemporal hemianopsia and optic
atrophy, rarely pituitary dysfunction
b) sylvian fissure: seizures
c) CPA: trigeminal neuralgia, especially in young
d) basilar-posterior fossa: lower cranial nerve,
cerebellar, and/or corticospinal tract abnormalities
e) within the ventricular system : more within the
4th ventricle
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27. Cont’d
• within the spinal canal:
a) most from thoracic or upper lumbar spine
b) epidermoids of the lower lumbar spine
may occur iatrogenically following LP
c) dermoids of the spinal canal are usually
associated with a dermal sinus tract: recurrent
spinal meningitis.
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28. 2811/26/2020

29. Diagnosis of epidermoid cyst
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30. Diagnosis of dermoid cyst
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31. Treatment
Goal of surgery:
• Cautious Complete microsurgical excision to px
chemical (Mollaret’s) meningitis & post-op
communicating HCP.
• Peri-operative IV steroids and copious saline
irrigation during surgery.
• leave capsule if adherent to critical structures
(brainstem & vessels).
• Residual capsule: lead to recurrence
• XRT: no role & doesn’t prevent recurrence.
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32. Pineal cyst
• 1-4% prevalence at imaging
• Etiopathogenesis: 3 major theories
 Enlargement of embryonic pineal cavity
 Ischemic glial degeneration +/- hemorrhagic
expansion
 Small pre-existing cysts enlarge with
hormonal influences
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33. Diagnosis
• Sharply-demarcated, smooth cyst behind 3rd
ventricle ,above tectum, below internal
cerebral veins.
• May flatten tectum, occasionally compress
aqueduct.
variable HCP (enlarged 3rd, lateral ventricles;
normal 4th V) with large cysts.
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34. Natural History & Prognosis
• Size generally remains unchanged in males
• Cystic expansion of pineal in some females
begins in adolescence, decreases with aging
• Rare: Sudden expansion, hemorrhage ("pineal
apoplexy")
Treatment
• Usually none
• Atypical/symptomatic lesions may require
stereotactic aspiration or biopsy/resection
• Preferred approach: infra tentorial supra
cerebellar
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35. Neuroglial cyst
Etiology
i. Intraparenchymal
• sequestration of lining embryonic neural tube
(neuroectoderm) within developing WM
ii. Subarachnoid space
• Leptomeningeal neuroglial heterotopia
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36. Diagnosis
• Nonenhancing CSF-like parenchymal
cyst with minimal/no surrounding signal
abnormality.
• Location: anywhere, Frontal lobe most
common site
• Morphology: Smooth, rounded, unilocular
benign-appearing
cyst
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37. Choroid plexus cyst
Etiology
• Lipid from desquamating, degenerating choroid epithelium accumulates
in choroid plexus
• Lipid provokes xanthomatous response
• commonest neuroepithelial cyst
• Prevalence increases with age
• Adult CPC: obstructive HCP (rare)
Diagnosis
• Older patient with "bright" choroid plexi on MRI
Location
• Atria of lateral ventricles most common site
• Attached to or within choroid plexus
• Usually bilateral:cystic mass(es) in choroid plexus glomi
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38. Diagnosis
• Morphology: Cystic or nodular/partially cystic
mass(es) in choroid plexus glomi
• Natural History & Prognosis: Usually
asymptomatic & nonprogressive
• Treatment:none, Shunt for obstructive HCP
(rarely)
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39. Choroid Fissure Neuroepithelial Cysts
Well-demarcated cysts along the choroid
fissure dorsal to the hippocampus.
On axial images, typically seen alongside
midbrain.
 Exhibit CSF signal characteristics.
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40. Hippocampal sulcal remnant cysts
• extremely common and benign findings
• do not indicate hippocampal atrophy or d/se.
• often bilaterally and are located along the
length of the hippocampal body
• not associated with Alzheimer disease
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41. Ependymal cyst
• Arise from sequestration of developing neuroectoderm
• Typically young adults, less than 40 years
• Diagnostic clue: Non-enhancing thin-walled cyst with
CSF density/intensity
Location
• Intraventricular common, typically lateral ventricle
• central WM of temporoparietal and frontal lobes
Morphology: Smooth, thin-walled cyst
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42. Cont’d
Natural History &Treatment
• Conservative management
if asymptomatic
• surgical excision or
decompression If
symptomatic.
• outcome: Rapid resolution
of symptoms after surgery
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43. Hemorrhagic subependymal cysts
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44. Porencephaly
• a cystic lesion lined by gliotic white matter of
cerebral hemisphere that usually communicate
with the ventricles.
Etiology
congenital: In utero vascular events / infection
(CMV)
Acquired: TBI, vascular occlusion, repeated
ventricular punctures or infection .
Location: Usually corresponds to cerebral arteries
territories
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45. Diagnosis
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46. Treatment
• Usually no treatment is required
• Indications for surgery: Mass effect
(hemimacrocephaly, midline displacement),
localized/generalized symptoms, intractable seizures
Options:
• Cystoperitoneal shunt (preferred)
• If no communication with ventricular system:
Fenestration or partial resection of cyst wall
Children with intractable seizures and
porencephaly benefit from uncapping and cyst
fenestration to lateral ventricle
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47. Schizencephaly
• is a neuronal migration anomaly characterized
by a cleft lined by heterotopic gray matter
that extends from the ependyma of the
lateral ventricles to the pial surface of the
cerebral cortex.
• absence of septum pellucidum in 80–90%
• presentation m ay range from seizures to
hemiparesis depending on size and location
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48. Periventricular Leukomalacia
• white matter necrosis.
• most frequently occurs in premature infants of less
than 32 weeks gestation due to the unique anatomic
features of the brain at this age.
• The white matter of these infants is poorly
vascularized and contains oligodendrocyte
progenitors, which are sensitive to the effects of
ischemia and infection .
• The cortex is usually spared.why?
• Bilateral parieto-occipital location and larger than 10
mm are highly predictive of the development of
cerebral palsy.
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49. Good
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50. Neurocysticercosis
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51. 5111/26/2020

52. Diagnosis
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53. Treatment
Medical rx : main stay of rx
• Antiparasitic therapy — Oral albendazole for
14 dys (reduces parasitic burden, seizures)
• Steroids should be used for 28 days.
• Antiseizure drug therapy
Antiparasitic rx C/I in patients with
encephalitic cysticercosis & ICP: use steroid
Surgical:
• obstructive vs communictive HCP: shunt
• intraventricular cysts causing obstruction:
Endoscopic resection
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54. Hydatid cyst
• 2% in CNS (less in spinal cord)
• Parietal lobe commonest; MCA territory
Diagnosis :
• Serology
• CT & mri Findings
 Large unilocular cyst mostly
with +/-detached germinal
membrane & daughter cysts.
 isodense /isotense/ to CSF
 No perilesional edema
 No enhancement
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55. Treatment
• Surgery (cyst excision) remains the main
treatment .
• Albendazole10 to 15 mg/kg/day administered
continuously without interruptions can be
beneficial for inoperable patients & with
multiple cysts.
• optimal dosage and optimal duration of rx:
unknown.
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56. Pyogenic brain abscess
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57. 5711/26/2020

58. Tumors with cystic components
• Craniopharyngioma
• Pilocytic astrocytoma
• Pleomorphic xanthoastrocytoma
• Ganglioglioma
• hemangioblastoma
• Cystic metastasis
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59. Craniopharyngioma (CP)
• Develop from residual cells of rathke’s pouch.
• At anterior superior margin of the pituitary.
• Not malignant but behaves malignant
• Bimodal: 5-15 yr (50%) vs >50 yr.
• Almost all have solid and cystic components.
• Variable fluid in the cysts, cholesterol (usual).
• Calcification: 85% in childhood, 40% in adults.
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60. Cont’d
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61. Diagnosis
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62. Surgical treatment
Preop
• Correct putitary dysfunctions.
Intraop
Post-op
1. steroids:hydrocortisone + dexamethasone taper.
2. diabetes insipidus (DI)
• Radiation
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63. Pilocytic astrocytoma (PCA)
• 5-10% of all gliomas
• Peak incidence: 5-15 years of age (>80%).
• WHO grade I
• causes obstructive hydrocephalus
• Associated with NF l
 15% of NF l patients develop PCAs, mostly in optic
pathway
 PCAs arising in the optic nerve are called optic
gliomas.
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64. Location
• Cerebellum (60%) > optic nerve path
(25-30%) > adjacent to 3rd ventricle>
brainstem
• Size: Larger in cerebellum than optic nerve
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65. Imaging
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66. 6611/26/2020

67. Pleomorphic Xanthoastrocytoma
• < 1% of all astrocytomas
• Important cause of temporal lobe epilepsy
• WHO grade II
• Tumor of children/young adults
• Peripherally located mass, involves cortex and
meninges
• Site: Temporal >frontoparietal> occipital lobes
• 98% supratentorial
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68. Diagnosis
• Supratentorial cortical mass with adjacent
enhancing dural "tail“
• Cyst and enhancing mural nodule typical
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69. Treatment
• Surgical resection is treatment of choice
• Repeat resection for recurrent tumors
• Chemo radiation: show no significant
role.
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70. Ganglioglioma
• Well differentiated, slowly growing neoplasm
of ganglion and glial cells
• Tumor of children, young adults ( 80% in <
30yr)
• occur anywhere in superficial hemispheres,
temporal lobe (commonest).
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71. Morphology
• Three patterns.
Most common: Circumscribed cyst + mural
nodule
Solid tumor (often thickens, expands gyri)
Calcification is common
In younger pts <10 yr, larger & more cystic
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72. Diagnosis
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73. Treatment
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74. Desmoplastic infantile ganglioglioma
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75. Hemangioblstoma
• Benign vascular tumor of unknown origin
• Sporadic HGBL: Peak 40-60 y
• Familial: VHL-associated HGBLs occur at younger
age but are rare < 15Yr
• Location –95% posterior fossa (80% cerebellar
hemispheres)
• WHO grade I (No malignant change)
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76. Imaging
• Best diagnostic clue – adult with intra-axial
posterior fossa cystic mass with enhancing
mural nodule abuttin pia.
• Morphology –60% with cyst + mural nodule.
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77. Natural History
• Usually benign tumor with slow growth pattern
• Symptoms usually associated with cyst expansion
Treatment
• En bloc surgical resection (piecemeal resection
result in catastrophic hemorrhage)
• Surgery curative in cases of sporadic HGB, not in
VHL.
• Pre-operative embolization: reduce vascularity.
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78. Summary of cystic tumors
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79. Cystic metastasis
• Squamous cell ca lung
• Adenocarcinoma lung
• Carcinoma thyroid
• Multiple
• Typically at gray-white matter junction
• Disproportionate edema
• Generally, metastatic lesions show no
restricted diffusion.
• After contrast injection, enhancement is variable in
morphology and frequently ringlike due to the presence of
central necrosis.
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80. Cystic glioblastoma
CT
• well-defined intra-axial cystic lesion with peripheral ring enhancement
• usually presents with mass effect
• mild perifocal edema
• enhancing margin and soft tissue component
• MRI
• T1: homogeneously hypointense
• T1 C+ (Gd): enhancing margin and soft tissue component
• T2: hyperintense
• FLAIR: cystic areas show hyperintensity relative to CSF due to higher
protein contents
DWI/ADC: no restriction for the cystic component; the solid component may
show restriction according to the grade
cerebral glioblastoma containing a large cyst survive longer and have a
longer period before recurrence than those who lack such a cyst 1,2.
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81. left intracerebral hematoma (late
subacute hemorrhage)
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82. Dandy-Walker malformation and
variants
• Best diagnostic clue
Large PF +
big cerebrospinal fluid (CSF) cyst +
normal 4th ventricle (V) absent
Location: Posterior fossa
• Classic" DWM:
 Small hypoplastic vermis - superiorly
rotated by cyst
 torcular arrested in fetal position
(cyst mechanically hinders caudal
migration)
 Ddx:
 persistent Blake’s pouch cyst Mega
Cisterna Magna, archinoid cyst
 Rx: shunt/ETV
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83. Cavum Septum Pellucidum: bordered by the corpus callosum and the column
and body of the fornix
Cavum Vergae:
• Anterior border: posterior to the columns of the fornix.
• lateral borders:crus of the fornix,
• inferior border is the hippocampal commissure,
• roof and posterior wall : posterior body and the splenium of the corpus
callosum, respectively.
 causes downward fornix displacement
Cavum septum interpositum: between the crus of the fornix and the
hippocampal commissure.
 Causes caudal displacement of the internal
cerebral veins and anterior and superior displacement of the fornix
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84. Normal Variants of septum pelucidum
The septum pellucidum consists of two thin
laminae of white matter surrounded by gray matter
with a potential intervening space are separated in
utero but fuse from back to front
as the fetus approaches term or in the first few
weeks after birth.
The septum pellucidum is part of
the limbic system; although its exact function is
not completely understood, it seems to moderate
behaviors such as rage and arousal.

86. Cavum Septi Pellucidum
• The cavum septi pellucidi persists when the
two leaves of septum pellucidum fail to fuse
• It is considered a normal variant due to its frequent
appearance and because a specific clinical syndrome
has not yet been identified with its occurrence.
• Recently, an enlarged cavum septi pellucidi serves as a
significant marker of cerebral dysfunction (4,5) and has
been described in various neuropsychiatric and
posttraumatic conditions (6).
• 5th ventrice? Not b/c no choroidal plexus &
ependymal lining.

87. Cavum Vergae
• a fluid-filled space between the two leaves of septum pellucidum
located posterior to an arbitrary vertical plane formed by the
columns of the fornix
• The cavum septi pellucidi and the cavum vergae usually
communicate with each other and obliterate from posterior to
anterior, the posterior cavum vergae obliterating first and then
usually the anterior cavum septi pellucidi.
• Thus a cavum vergae without a cavum septi pellucidi would be
unexpected.
• The cavum veli interpositi is separated from the cavum vergae by
the crura of the fornices (9).
• 6th ventrice? Not b/c no choroidal plexus & ependymal lining.

88. Cavum Veli Interpositi
• Development of the cavum veli interpositi is
independent of the septum pellucidum, and it is believed
to be the result of abnormal separation of the crura of the
fornices.
• The cavum veli interpositi is an anatomic
variation that may appear as a cyst in the pineal
region.
• It is a potential space above the tela choroidea of the third
ventricle and below the columns of the fornices. The
internal cerebral veins run inferiorly (9).

89. 8911/26/2020