Colloid cysts are benign tumors located in the anterior third ventricle that can cause hydrocephalus. They arise from ependymal or choroid plexus cells. Common symptoms include headache, nausea, and gait disturbances. On imaging, colloid cysts appear hyperdense on CT and hyperintense on T1-weighted MRI. Treatment options include conservative management, shunting, and surgical resection via transcallosal or transcortical approaches. Endoscopic resection has lower risks but higher recurrence rates compared to microsurgery. Complications of surgery include venous infarction, mutism, and CSF leaks.

1. Dr. Rabail Akbar Qazi
Neurosurgery Resident
COLLOID CYST

2.  Benign tumors of the neuroectodermal origin
constituting 0.5% to 1% of all intracranial neoplasms
 They arise from the anterior aspect of velum
interpositum or the choroid plexus of the third
ventricle, in close proximity with the foramen of
monro
 Slow growing

3. ANATOMY

13. PATHOGENESIS
 Origin: Unknown
 Implicated structures include:
 Paraphysis
 Diencephalic ependyma in the recess of postvelar arch
 Ventricular neuroepithelium
 Comprised of fibrous epithelial-lined wall filled with
either mucoid or dense hyaloid substance

15.  Can occur in any age with peak between the 2nd and 4th
decades of life with no sex predilection.
 Cyst wall is lined with simple or pseudostratified
cuboidal or low columnar ciliated epithelial cells
 Stain positive for PAS & S100 and negative for GFAP,
vimentin and neurofilament.

16. SYMPTOMS
 In 75% of the patients, the initial symptom is headache
with variable intensity.
 Other symptoms include nausea, vomiting, gait
disturbance and blurred vision.
 A sudden increase in ICP from rapid onset
hydrocephalus can lead to sudden death

17.  By compression of the surrounding anatomic
structures, the patient can experience thermal
dysregulation, electrolyte and hormonal imbalances,
endocrine dysfunction , altered personality, memory
loss or visual changes.

20.  Most cysts <1cm donot produce hydrocephalus and are
asymptomatic.
 Colloid cysts may cause chronic, acute or intermittent
hydrocephalus .
 Intermittent symptoms are attributed to the movement
on the cyst on its pedicle causing intermittent
obstruction to CSF flow.

21. EVALUATION
 Imaging usually demonstrates the tumor located in the
anterior third ventricle.
 If there is obstruction to CSF flow due to the cyst, it
manifests as pathognomonic hydrocephalus involving
only the lateral ventricles.
 MRI is usually the imaging modality of choice.

22. CT SCAN:
 Most are hyperdense
 Density may correlate with
viscosity of the contents
 Typically homogenous, with
presence of calcifications being
an exception.

23. MRI :
 Appearance variable
 T1WI: Hyperintense
 T2WI: Hypointense
 No or minimal contrast enhancement, sometimes only
involving the capsule
 Symptomatic patients are more likely to display T2
hyperintense cysts

27. TREATMENT
 Conservative
 Shunting procedure
 Surgical
 Microsurgical
 Endoscopic

28. RECURSIVE PARTITIONING ANALYSIS

30. DIVERSION PROCEDURES:
 Bilateral ventriculoperitoneal shunts
 Unilateral shunt with septum pellucidotomy
 However, direct surgical treatment is usually
recommended due to:
 To prevent shunt dependency
 To reduce the possibility of tumor progression
 Risk of cardiovascular instability

31. SURGICAL MANAGEMENT:
 Transcallosal approach : Not dependent on
ventriculomegaly
 Transcortical approach: In patients with HCP
 Stereotactic drainage
 Ventriculoscopic removal

32. STEREOTACTIC DRAINAGE:
 Maybe useful in patients with normal ventricles
 High recurrence rate
 Short hospital stay and early recovery time
 Viscous contents and tough capsule lead to failure of
procedure

33.  Two features correlating with unsuccesful aspiration:
 High viscosity: Correlates with hyperdensity on CT
 Deflection of the cyst from tip of the aspiration needle
due to small size

34. Technique:
 Insertion point of the needle is just anterior to the right
coronal suture

35.  Start with sharp-tipped 1.8mm probe, and advance to
3–5mm beyond target site (to accommodate for
displacement of cyst wall

36.  Use a 10ml syringe and apply 6–8ml of negative
aspiration pressure

37.  If this does not yield any material, repeat with a
2.1mm probe.
 Although complete cyst evacuation is desirable, if this
cannot be accomplished an acceptable goal of
aspiration is re-establishment of patency of the
ventricular pathways (may be verified by injecting 1–2
cc of iohexol)

38. ENDOSCOPIC Vs. MICROSURGICAL
ENDOSCOPIC MICROSURGICAL
Lesser extent of resection Greater extent of resection
Higher rates of recurrence (3.91%) Lower rates of recurrence (1.48%)
Higher rates of reoperation (3.0%) Lower rates of reoperation (0.38%)
Lower complication rate (10.5%) Higher complication rate (16.3%)
Similar mortality rate Similar mortality rate

39. ENDOSCOPIC APPROACH:
 Planning:
 Preop MRI for frameless stereotactic guidance
 Place patient’s head in three point fixation, flexed at 45
degrees
 Incision should be behind the hairline
 Place a burrhole 8cm from the nasion, 5 -7 cm lateral to
the midline

40. PROCEDURE:
 Create a burrhole large enough for easy maneuvering
of the endoscope (usually 11mm)
 Tap into the lateral ventricle
 Use a 0 degree scope to identify the landmarks of the
colloid cyst and foramen on monro.

43.  Change to a 30 degree scope
 Colloid cyst can be identified by its greenish grey
membrane
 Resection technique for the cyst depends on it’s size
and consistency
 If the contents are liquid, cyst can be punctured and
contents aspirated through an appropriate suction tube.
 Sometimes, cyst has to be opened with microscissors
and contents removed in a piecemeal fashion

45. TRANSCALLOSAL APPROACH:
 Interhemispheric approach to the third ventricle via a
parietal craniotomy
 Position: Supine with neck flexed. Thorax elevated at
20 degrees. Keep the head vertical
 Skin Incision:
 Inverted U with the top just left of midline, 6cm anterior
to the coronal suture, to 2 cm behind the coronal suture,
taking the sides for 7-8cm
 Souttar skin incision

47. Craniotomy:
 The bone flap is either trapezoid or triangular
 For adequate exposure, it is critical to go all the way to
the superior sagittal sinus
 To stay away from the motor strip and to keep sagittal
sinus exposure as anterior as possible:
 2/3rd of the craniotomy anterior to the coronal suture
 1/3rd posterior to the coronal suture

48.  Total craniotomy size should be 6cm
 4cm anterior to the coronal suture
 2 cm posterior to the coronal suture
 4cm to the right of midline
 The dural flap is based towards the sagittal sinus

54. COMPLICATIONS:
 Venous infarction
 Sacrifice of critical cortical draining veins
 SSS thrombosis
 Transient Mutism due to rough retraction of cingulate gyrus
 Decrease in spontaneous speech due to resection of anterior
portion of CC
 Damage to fornix resulting in temporary or persistent
amnestic syndromes
 Intraventricular bleeding
 CSF leak

55. TRANSCORTICAL APPROACH:
 Patient supine with three pin fixation, head flexed at
30 degrees, 10 to 50 degree rotation to the contralateral
side
 3x4 cm bone flap placed over the location of the
middle frontal gyrus
 Medial border should just cross the midline and the
anterior border 2cm anterior to the coronal suture and
posterior border 2 cm behind.