Definition
- Torcular meningiomas arise from, invade, or are attached to a wall of the torcular Herophili, the site of confluence of the superior sagittal, straight, occipital, and both transverse sinuses
Numbers
- Average age at presentation was 35.5 years
- Median interval between symptom onset and diagnosis was 1 year
Pathology
- Arise from arachnoidal cap cells in the region of the torcular Herophili
- The dura is a poor barrier to tumor extension; tumors frequently penetrate the distal falx or posterior tentorium to reach an adjacent torcular quadrant.
- By compressing or invading the superior sagittal, straight, transverse, and/or occipital sinuses, peritorcular meningiomas threaten dural venous sinus flow at the torcular Herophili
Clinical Presentation
- Pain
- Headache (50%)
- Generalized
- Due to
- Increased intracranial pressure.
- Venous congestion
- Occipital and suboccipital pain
- Due to deformation of surrounding dura
- Neck pain and stiffness
- Due to incipient tonsillar herniation
- Symptoms of generalized intracranial hypertension (headache, vomiting, and seizures).
- Due to
- Venous congestion
- Cerebellar signs
- Due to infratentorial tumor extension
- Eg nystagmus, dysmetria, hypotonia, and ataxia
- Most are slow growing so it is rare to have acute neurological deterioration that might result from sudden thrombosis of a partially occluded dominant sinus
- Dysfunction of the occipital lobe (visual field loss and seizures)
- Patients with Peritorcular meningiomas (n=12)
Symptoms | Count | Signs | Count |
Visual loss | 11 | Papilledema | 12 |
Headache | 10 | Homonymous field cut | 7 |
Neck pain/stiffness | 4 | Cerebellar deficits | 5 |
Gait difficulty | 3 | Scotoma/atrophic blindness | 3 |
Memory problems | 2 | Cortical sensorimotor loss | 3 |
Radiology
MRI
- MRI+C
- The distinctiveness of the margin between tumor capsule and cortex may correlate with the ease of maintenance of a plane of surgical dissection and with benign rather than invasive malignant histology
- T2:
- A patent sinus has a signal void characteristic of flowing blood: this is especially evident on T2-weighted scans, which maximize contrast with the higher intensity of cerebrospinal fluid (CSF).
MRV
- Peritorcular venous channels are usually asymmetrical and septate.
- The right transverse sinus frequently carries most of the superior sagittal sinus outflow and may be larger than the left transverse sinus, which frequently carries most of the straight sinus flow
Angiography
- MRA
- DSA+embolization
- Sinus occlusion manifests as absence of sinus filling and flow of blood from the torcular into dural, cerebral, or cerebellar collaterals.
- The details of the site and cause of venous sinus obstruction are best seen on retrograde dural sinus venography.
- Direct endovascular cannulation of the transverse sinus also allows assessment of tolerance of sinus obliteration;
- Neurological function and intraluminal pressure proximal to the blockage should be measured during periods of balloon inflation.
- The extent of communication of the superior sagittal flow with each transverse sinus and of one transverse sinus with the other determines the safety of sinus occlusion and thus the surgical resectability of a peritorcular meningioma
- Embolization of the feeding arteries
- (Usually the middle meningeal and occipital branches from the external carotid artery, the meningeal branches of the vertebral artery, and the tentorial branches of the cavernous internal carotid artery) can be identified and possibly embolized, as can vessels within the tumor itself.
Surgery
Perioperative Management and Anesthetic Technique
- Preoperative administration of prophylactic corticosteroids and antibiotics is indicated;
- Anticonvulsants should be given if there is a history of seizure
- GA combination of inhalation agents and intravenous narcotics is required
- Moderate hyperventilation and osmotic diuresis reduce brain volume and facilitate exposure.
- Use of intermittent-compression boots reduces the risk of deep vein thrombosis.
- Two large-gauge IV lines are placed in the event that rapid volume replacement is needed.
- Arterial line facilitates monitoring of blood pressure and respiratory function.
- Signs of venous air embolism are sought with an esophageal cardiac Doppler monitor and a gauge for end-tidal Pco2
Position
- Unilateral approaches
- 45-degree prone oblique
- Concorde
- Sitting positions
- Bilateral exposures
- Prone
- Concorde
- Sitting position
- Higher risk of venous air embolism.
Incision
- An inverted U-shaped incision with its apex at the lambda and its base between the mastoid process is excellent for bilateral combined exposures.
- The incision may be narrowed, shortened, or even replaced by a linear incision if less exposure is required.
- The incision is carried through all layers of the scalp and pericranium, which are then elevated and held retracted over a rolled sponge.
Craniotomy/Craniectomy
- Bone is ordinarily removed through a free-flap occipital craniotomy or a suboccipital craniectomy
- When traversing the superior sagittal sinus, transverse sinuses, torcular Herophili, thinning the bone with a drill and then removing the eggshell remnant with a fine bone punch will reduce the risk of sinus injury.
- Dural adhesion to bone
- Resulting from
- Osseous tumor invasion
- Hyperostosis
- Patient age
- Increases the risk of injury to the
- Dura
- Tumor’s feeding arteries
- Venous sinus
- Subdural tracking of the craniotome footplate can be avoided by performing a strip craniectomy at the margins of the bone flap, exposing the marginal dura under direct vision, and interrupting dural arteries before removal of the bone flap
- If the roof of a venous sinus is incorporated in the bone to be removed, its laceration can be avoided by performing a unilateral free flap craniotomy to the edge of the superior sagittal sinus and torcular Herophili on one side:
- Then, under direct vision, the superficial surface of the sinuses can be freed from overlying bone before the contralateral craniotomy plate is removed
- Single craniotomy flap
- When dural adhesion to bone is unlikely because the patient is young, the tumor is small, and hyperostosis is absent, all four quadrants of the peritorcular region
- Infiltrated or hyperostotic bone should be removed and discarded.
- Peripheral epidural tacking sutures are placed.
- Bilateral
- For tumors arising directly from the torcular wall, exposure of all four quadrants of the peritorcular region is advisable because it permits control of all venous flow in and out of the region.
Durotomy
- The dura should be incised 1 to 2 cm from the tumor’s margin
- Large afferent tumor arteries within the dura should be well coagulated or clipped or both before being cut.
- The dura should be hinged to maximize the view of a peritorcular tumor
- Relaxation of protruding tumor and/or brain is facilitated by draining CSF either supratentorially by ventriculostomy of the lateral ventricle or infratentorially by opening the cisterna magna.
- Additional attachments of the tumor to convexity dura should be coagulated and divided.
Tumor Resection
- Tumor removal is best accomplished in four stages:
- Coagulation and division of the tumor at its attachments to accessible dural leaves and sinus walls; this devascularizes the main tumor mass of all but its parenchymal inflow;
- Internal debulking of the main tumor mass;
- Microdissection of the tumor capsule from the surrounding cortex; and
- Removal of tumor remnants along or within the major sinuses.
- Exposure of the dorsal surface of the tumor is increased by gentle superior retraction of the overlying occipital pole and inferior mobilization of the cerebellar hemisphere.
- As exposure is deepened, the remaining dural arterial inflow can be divided as access is gained
- Removal of most tumors is accomplished by a repetitive series of internal debulking using morcellization by coagulation and suction or an ultrasonic aspirator and microdissection of the thinned capsule away from occipital or cerebellar cortex. Meticulous extraarachnoidal microdissection that preserves the pia of the occipital lobe is critical to avoiding visual loss.
Closure
- Closure is begun only after the integrity of all sinus suture lines is confirmed during a Valsalva maneuver.
- Occipital and cerebellar cortex is checked for injury as retraction is released.
- Defects in convexity dura are closed with grafts of pericranium harvested from the inner surface of the scalp flap.
- The craniectomy plate is fixed with titanium miniplates.
- The craniectomy defect is bridged with titanium wire mesh. The wound is closed in two layers and dressed in routine fashion.
Management of Sinuses
- Best is to just leave tumour and Sinus and either watch overtime or irradiated.
- The likelihood of achieving total resection of a peritorcular meningioma depends on the nature of sinus involvement by the tumor: only rarely is tumor resection precluded by tumor attachment to eloquent cortex or critical arteries.
- Sinus is not patent
- The portion of a venous sinus completely occluded by tumor can be resected safely.
- When removing an occluded superior sagittal sinus, special care must be taken to preserve the anterior and lateral collaterals carrying the hemispheric flow.
- An involved transverse sinus can be divided and resected
- If preoperative CTV/MRV has shown that
- The sinus is occluded by tumor or is congenitally atretic
- The medial portion of the sinus communicates completely with a patent contralateral transverse sinus of adequate caliber
- The superior sagittal sinus and straight sinus are fully confluent with a patent contralateral transverse sinus of adequate caliber.
- If preoperative venography has not unequivocally demonstrated the adequacy of the contralateral sinus, trial occlusion of the involved sinus by temporary intraoperative clamping may help assess the compensatory capacity of the contralateral sinus.
- Interruption of a transverse sinus should be medial (posterior) to the junction of the vein of Labbé and the transverse sinus.
- The occipital sinus
- Is of little importance unless, as a hypertrophied collateral of an obstructed transverse sinus, it carries substantial superior sagittal or straight sinus outflow to the jugular bulb.
- Sinus is still patent
- When the venous anatomy demands preservation of the flow through a sinus involved with tumor, the possibility of removing the tumor from the sinus depends on the extent of sinus involvement.
- If a tumor merely abuts or is attached to the sinus by arachnoidal adhesions, it can be peeled from the sinus wall. The external sinus surface should then be coagulated with bipolar cautery.
- When tumor invasion is limited to one wall or a corner of a critical sinus, the tumor external to the sinus should be truncated
- The invaded wall or corner and intrasinus extension of tumor can often be removed, and the resultant defect closed with direct suture or patch graft.
- This is best done by sequentially opening and closing small segments of the sinus as the tumor is progressively removed from within the sinus.
- The walls of the partially opened sinus are grasped with vascular forceps or small clamps such that they can be released to permit removal of tumor or approximated to allow closure
- Transient opening of the sinus in such a controlled fashion permits removal of an intrasinus tumor with relatively little blood loss.
- Removing a tumor involving more than one wall or corner of the sinus is much more hazardous because sinus flow must be interrupted during repair of the sinus. A blood-diverting shunt has been used in tumor removal and patch graft repair of the more proximal superior sagittal sinus. An analogous approach using a shunt from the superior sagittal sinus to the transverse sinus during isolation and repair of a tumor-invaded torcular Herophili is appealing in theory but would likely be quite hazardous.
- Patch grafts that replace more than one sinus wall are often unsatisfactory because wall collapse and luminal obstruction can occur when sinus venous pressure is low.
- Removing a tumor involving the torcular itself might necessitate shunting flow from the superior sagittal, straight, and occipital sinuses and replacement of the torcular by a four-limbed prosthesis. In such cases, the risks concomitant with interruption or diversion of venous sinus flow and reconstruction of the torcular Herophili in an attempt to achieve complete resection of a peritorcular tumor are likely unwarranted.
Surgical Outcome
- Postoperative Complications
- Catastrophic outcomes can result from mismanagement of the dural sinuses.
- Failure to repair an opened sinus can result in life-threatening intracranial hemorrhage.
- Compromise of a previously patent sinus can lead to cerebral venous congestion, infarction, and intraparenchymal hemorrhage.
- Visual loss
- Due to
- Venous congestion of the visual cortex
- Indelicate microdissection of the tumor capsule
- Heavy-handed retraction of the occipital lobe.
- Excessive retraction is best avoided by extensive internal debulking of a tumor that permits inward collapse of an attenuated capsule.
- Infection
- Reduced by
- Operative technique
- Copious irrigation of the operative site
- Prophylactic antibiotics
- Seizures
- Diminished by
- Careful manipulation of the occipital cortex
- Preservation of cortical venous drainage
- Prophylactic anticonvulsants.
- Long-Term Prognosis
- The risk of tumor growth varies inversely with the extent of resection
- Complete resection is often precluded by involvement either of the walls of the torcular or of more than one wall of an adjacent sinus.
- For such cases, the risks of attempts at resecting all involved dura are unwarranted. Small residua of tumors should be followed by periodic neurological examination and MRI+C.
- Recurrent tumor growth can be treated by
- Reoperation
- Stereotactic radiosurgery
- Fractionated radiation therapy (50 to 60 Gy)
- Indicated if dural spread is extensive
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