Numbers
- Meningiomas of the posterior cranial fossa account for 9% of all intracranial meningiomas.
- Tentorium meningiomas account for
- 3-6% of all intracranial meningiomas
- 30% of posterior fossa meningiomas
Tentorium cerebelli
- Divides the cranium into the supratentorial and infratentorial compartments.
- Incisura: Free edge of the tentorium
- A dural duplication
- Attachment
- Posteriorly
- To the transverse ridges on the inner surfaces of the occipital bone
- Encloses the transverse sinuses
- Anterolaterally
- To the superior ridge of the petrous portion of the temporal bone,
- Enclosing the superior petrous sinus on both sides.
- Anteriorly
- To the posterior and anterior clinoid processes.
- The free edges of the incisura pass over the trigeminal ganglion to insert onto the petrous apex and the anterior and posterior clinoid processes.
- These insertions form three dural fold/ligaments: (Aka oculomotor trigone, through which the oculomotor nerve enters the cavernous sinus)
- Anterior petroclinoid fold/ligaments
- Posterior petroclinoid fold/ligaments
- Interclinoid fold/ligaments
- The medial extension of the dura covering the oculomotor trigone is the diaphragma sellae. Dura extending anteriorly from the free edge will form the lateral wall of the cavernous sinus and cover the middle cranial fossa.
- Medially
- Incisura tentorii
- Preservation structures around the incisura by surgical dissecting the arachnoid layers forming the lateral walls of the chiasmatic, crural, ambient, and interpeduncular cisterns and is important to obtain a good surgical result.
- For transmission of the midbrain.
- Divided into
- Located in front of the brain stem
- Important structure
- Oculomotor nerve,
- Basal vein,
- Posterior communicating artery,
- Anterior choroidal artery,
- P1 and proximal P2 segments of the posterior cerebral artery,
- Superior cerebellar artery.
- Optic nerve and the optic chiasm may be involved
- Less often involved
- Located lateral to the brain stem
- Bounded medially by the cerebral peduncle and upper pons.
- Important structure
- Crural cistern, located between
- Uncus and cerebral peduncle anteriorly,
- Ambient cistern situated between the midbrain and parahippocampal gyrus posteriorly
- Trochlear nerve
- Tiny trochlear nerve located just beneath the tentorium because it may be damaged in the subtemporal or petrosal approach.
- Anterior choroidal artery
- P2 segment of the posterior cerebral artery
- Superior cerebellar artery
- Basilar vein constitute
- Located behind the brain stem
- Important structure
- Ambient cistern into the quadrigeminal cistern
- This space forms the pineal region and is related to anterior falcotentorial meningiomas.
- PCA and SCA: Trunks and branches
- Vein of Galen
- Which receives the paired internal cerebral and basal veins.
- Trochlear nerve
- Exits from below the inferior colliculi, curves around the dorsal midbrain, and enters the ambient cistern in the middle incisural space.
- Superiorly
- The falx cerebelli
- A small triangular dural process that arises in the midline from underneath the tentorium.
- It indents between the two cerebellar hemispheres.
- The upper surface of the tentorium connects to the posterior end of the falx cerebri in the midline,
- Enclosing the straight sinus along the line of junction.
- Straight sinus receives the vein of Galen and the inferior sagittal sinus at the tentorial apex and runs posteriorly to meet the transverse sinuses from both sides and the superior sagittal sinus from above at the torcular Herophili.
Anterior incisural space
Middle incisural space
Posterior incisural space
- Arterial supply from
- Basal tentorial artery (artery of Bernasconi-Cassinari) originating from
- Meningohypophyseal trunk
- Marginal tentorial artery arising from the inferolateral trunk of the intracavernous carotid
- Tentorial branches originating from
- SCA
- PCA
- A peculiarity of the tentorium is the presence of interdural venous sinuses, which may become particularly prominent when major venous channels are occluded by tumor.
- Brisk bleeding from these venous lakes may be anticipated during incision of the tentorium in the occipital transtentorial approach.
- This bleeding can be controlled by bipolar coagulation.
- In the authors’ experience, no neurological sequelae have been caused by their occlusion.
- The surgeon should study the venous drainage pattern of the temporal lobe and the point of termination of the subtemporal veins into the venous sinuses when planning for a subtemporal or petrosal approach.
Classification
- Modified (by Al Mefty) Yaşargil classification scheme comprising the following five tumour subgroups
- T1–T2 (medial “incisural” meningioma)
- T3–T8 (falcotentorial meningioma)
- T4 (paramedian “intermediate” meningioma)
- T5 (peritorcular “torcular” meningioma)
- T6–T7 (lateral tentorial meningioma)
- Most often encountered subtype
- Difficult to differentiate between infratentorial T6–T7 and posterior petrosal meningiomas on clinical and radiological grounds
- Lateral tentorial meningiomas may intraoperatively prove to have an additional origin from the suprameatal posterior petrosal surface
- Original Yaşargil classification (By the confinement of meningioma in relation to the tent)
- Meningiomas arising from the free tentorial notch (inner ring meningiomas)
- Anterior T1
- Middle T2
- Posterior T3
- Meningiomas originating from the intermediate tentorial surface (T4)
- Meningiomas involving the torcular Herophili (T5)
- Meningiomas arising from the lateral outer tentorial ring (posterior T6, anterior T7)
- Falcotentorial meningiomas (T8)
Clinical Presentation
- Depend on the location and size of the tumour
- Generally a chronic presentation
- Tumor-related complaints are often present for long periods, usually months or even years,
- Acute presentation
- Rarely
- Acute symptoms of obstructive hydrocephalus.
- Location and sympytoms
- T6–T7 infratentorial meningioma
- Commonly present with headache, dizziness, and gait unsteadiness
- T1–T2 meningiomas may intimately involve the brain stem and the CN V
- Hemiparesis, trigeminal neuralgia, and facial numbness
- T3–T8 meningiomas
- Often present with headache
- Hearing loss
- Impairment of the vestibulocochlear nerve
- Distortion of the central auditory pathways, such as the lateral lemniscus or the inferior colliculi
- Gait ataxia
- Impairment of the
- Vestibulocochlear nerve
- Cerebellum
- Gait ataxia in 43 to 62% of cases
- Seizures
- Supratentorial meningiomas, particularly those closely related to the medial temporal lobe
- Mental changes
- 46% of patients
- Homonymous hemianopsia
- 20 to 46%
Symptoms | No. of patients | % patients | Symptoms | No. of patients | % patients |
Headache | 76 | 70.4 | Seizures | 11 | 10.2 |
Dizziness | 50 | 46.3 | Hemiparesis | 8 | 7.4 |
Gait disturbance | 46 | 42.6 | Trigeminal neuralgia | 7 | 6.5 |
Mental changes | 13 | 12.0 | Hemihypesthesia | 5 | 4.6 |
Visual disturbance | 13 | 12.0 | Tinnitus | 4 | 3.7 |
Hearing impairment | 12 | 11.1 | Dysphagia | 2 | 1.9 |
Neurological sign | % patients | Neurological sign | % patients |
Gait ataxia | 50.0 | Mental deficits | 13.0 |
Cranial nerve deficits | 27.8 | Hemiparesis | 7.4 |
2nd nerve | 4.6 | Homonymous hemianopsia | 5.6 |
3rd nerve | 3.7 | Hemihypesthesia | 4.6 |
5th nerve | 5.6 | Aphasia | 2.8 |
8th nerve* | 13.0 | Symptoms—no deficits | 13.9 |
9th nerve | 1.9 | Incidental finding | 3.7 |
ㅤ | ㅤ | Arterial hypertension† | 1.9 |
Radiology
General
- Even the most sophisticated radiological investigations available today have important shortcomings that should be recognized.
- A nonvisible venous sinus on MRV or catheter angiography may prove to be patent during surgery.
- Tentorial sinuses, which may be a source of brisk bleeding, are usually not visualized preoperatively.
- Reliable information on functional significance of venous sinuses and major veins is usually lacking.
- The exact relationship of the tumour to neighbouring cranial nerves (displacement, infiltration) can only be fully appreciated during surgery.
CT
- Less important for the preoperative workup of tentorial meningiomas due to its inaccuracy in demonstrating posterior fossa pathologies and due to the fact that involvement of bone is not a prominent feature in these tumors.
- The rare presence of tumor calcification can give some clue to tumor consistency.
MRI
- Triplanar contrast-enhanced T1 weighted
- Gives the most accurate information for planning the surgical approach.
- Look for
- Dural attachment zone
- Extent of the tumor
- Displacement of the brain stem
- Displacement or engulfment of vertebrobasilar arteries
- Invasion of the cavernous sinus,
- Patency of the straight, transverse, and sigmoid sinuses
- T2
- Look for
- The interface between the tumor and the brain stem
- Disruption of the blood–brain barrier and difficulties in resecting the tumor from the brain stem may be anticipated.
- A hyperintensive signal within the brain parenchyma
- It is often safer to leave a tumor remnant in these situations.
MRV
- Look for
- Drainage pattern of the subtemporal venous complex and patency of venous sinuses
- This investigation has largely replaced invasive catheter angiography.
Management
Conservative
- Repeat scan and monitor
- Indicated
- Small tentorial meningioma
- Incidental on MRI
- Asymptomatic or presents with minor unspecific symptoms, such as headache and dizziness.
- In an elderly patient
- The tumor may remain quiescent for many years, and the initial unspecific symptoms may resolve spontaneously.
Surgery
Indication
- Follow-up examinations demonstrate progressive tumor growth
- Deterioration of symptoms
Primary goal of treatment
- Complete resection of the tumor
- Including its dural origin and any involved bone at first operation.
- Preservation of the integrity of neurovascular structures and restoration of normal function or at least preservation of preexisting neurological function.
Surgical technique
General
- To reduce the incidence of postoperative complications, tumor resection should strictly follow arachnoid cleavage planes.
- The arachnoid may be disrupted in large and recurrent tumors.
- Leave a tuft of tumor if it is adherent to critical structures:
- Brain stem
- Cranial nerves
- Blood vessels
- Nerve control
- Particular attention should be given to preserving the integrity of the trochlear nerve at the tentorial hiatus.
- CSF control
- Early opening of the cisterns and cerebrospinal fluid egress is desirable, but it may not be readily achievable at the very start of the exposure.
- Insertion of a lumbar drain is generally not safe, especially for large lesions with brain oedema.
- Venous sinus involvement
- The inner dural lining can often be kept intact.
- If both dural layers are intermingled with tumor.
- Preservation of a patent venous sinus is important so merely devitalize the tumor attachment area by low-current bipolar coagulation.
- If there is a radiologically completely occluded venous sinus
- Venous sinus can be resected along with the tumor
- However, there remains some uncertainty in regard to patency of the venous sinus. Atresia or septation in the region of the sinus confluence may lead to misinterpretation with regard to dominance of the venous sinus.
T3–T8 meningiomas
- The occipital interhemispheric approach exposes falcotentorial tumours and the occipital transtentorial approach is used for those extending to the pineal region and posterior central tentorial hiatus..
- Occipital transtentorial approach.
- More common
- Transection of the tentorium should be individualized and not routinely performed because there is a risk of significant blood loss due to opening a tentorial sinus.
- The occipital approach should be considered for tumors that have displaced the galenic venous system inferiorly.
- This information can be obtained from preoperative coronal or sagittal contrast enhanced MRI.
- Bioccipital approaches
- Usually avoided.
- Contralateral tumor portions can be resected transfalcially, which includes interruption of the inferior sagittal sinus.
- If the galenic venous system is displaced superiorly, a supracerebellar infratentorial approach may be more appropriate for tumor resection.
- Further considerations in choosing the most suitable route for resection of T3–T8 tumors include
- Steepness of the tentorium and
- Location of the main tumor bulk in relation to a line drawn along the straight sinus on T1-weighted sagittal MRI scans.
T5 meningioma
Large lesions may require a combined supra- and infratentorial approaches with preservation of the transverse sinus whenever possible.
- Preservation of patent straight sinus and the deep veins is most important and may necessitate leaving residual tumour.
- Complete removal often impossible and should not be done
- Because the venous sinus wall is usually heavily infiltrated
- Removal of the supra- and infratentorial tumor bulk, usually via a “four quadrant” (bioccipital/bisuboccipital) craniotomy is followed by cautious bipolar coagulation along its sinus wall attachment.
Supra-tentorial T1–T2 and T6–T7 tumors
- Supratentorial tumor extensions can be resected transtentorially.
- It is usually possible to resect the tumor matrix along with the outer dural layer to achieve a complete resection.
- Lateral suboccipital retrosigmoid approach
- Used for most T1-T2 and T6-T7 tumours
- Subtemporal route more common
- Positioning of the patient’s head to take advantage of gravity and preoperative insertion of lumbar cerebrospinal fluid (CSF) drainage may facilitate temporal lobe retraction.
- The craniotomy
- Should be flush with the base of the middle cranial fossa;
- In some cases it is advantageous to add a zygomatic osteotomy to provide a flatter angle of view to the lesion.
- The relation of the zygomatic arch to the base of the middle cranial fossa can be appreciated on preoperative reformatted coronal bone window CT scan.
- Should be large enough to facilitate preservation of the subtemporal veins
- Paramedian supracerebellar transtentorial approach
- Can be used If a supratentorial meningiomas that have not extended to the surface of the petrous bone, for T1–T2 meningiomas to avoid the veins of the temporal lobe.
Large supra-infra-tentorial T1-T2 meningiomas
- Supra-infra-tentorial presigmoid approach
Infratentorial T1–T2. T6–T7, T4, T5, and T3–T8 meningiomas
- Posterior fossa lesions which are supracerebellar and may extend to the cerebellopontine angle as well as petrotentorial meningiomas are approached via a suboccipital craniotomy.
- They tend to displace rather than directly involve the cranial nerves.
- Patient positioning
- Semisitting position
- Must employ standard anesthetic monitoring to detect and treat air embolism.
- Three-quarter prone (reduce the risk of air embolism)
- Park bench (reduce the risk of air embolism)
- Concorde position (reduce the risk of air embolism)
- In patients with significant obstructive hydrocephalus, insertion of a ventricular CSF drain at the time of tumor resection to relieve elevated brain pressure is advisable
- The supracerebellar infratentorial route may be more appropriate in more medial infratentorial T1–T2 tumors and in infratentorial T3–T8 tumors, and it is the approach of choice in infratentorial T4 tumors.
Treatment of recurrent tentorial meningiomas carries a high risk of surgical morbidity and mortality due to the absence of safe arachnoid dissection planes that help to protect important neurovascular structures.
- Resection of recurrent tumor is often incomplete.
Surgical approach
- Different surgical approaches are required based on the wide ranging locations and extensions of meningiomas arising from the tentorium.
- Resection of the tentorial attachment is desirable whenever possible to achieve complete resection, but one has to bear in mind potentially vital venous drainage from the deep brain structures and its variability. This is especially important around the falcotentorial junction and the torcular.
- Anteriorly located supratentorial meningiomas are approached via the trans-sylvian or subtemporal approaches trying to minimize brain retraction.
Tumor location | Surgical approach | Tumor location | Surgical approach |
T1/2 (incisural) | ㅤ | T5 (peritorcular) | ㅤ |
Infratentorial | - Supracerebellar infratentorial - Suboccipital retrosigmoid | Suprainfratentorial | Bioccipital / suboccipital |
Supratentorial | Subtemporal | Infratentorial | Supracerebellar infratentorial |
Suprainfratentorial | Infrasupratentorial presigmoid | T6/7 (lateral) | ㅤ |
T3/8 (falcotentorial) | ㅤ | Infratentorial | - Suboccipital retrosigmoid - Supracerebellar infratentorial |
Supratentorial | Bioccipital interhemispheric | Suprainfratentorial | - Retrosigmoid - subtemporal |
Suprainfratentorial | - Occipital transtentorial - Bioccipital / suboccipital | Supratentorial | Subtemporal |
Infratentorial | Supracerebellar infratentorial | Falx cerebelli | ㅤ |
T4 (paramedian) | ㅤ | Infratentorial | Supracerebellar infratentorial |
Infratentorial | Supracerebellar infratentorial | ㅤ | ㅤ |
- Midline infratentorial supracerebellar approach:
- Prone 3 pins concord position
- Get head as flex as possible
- Midline skin incision from above inion to C2
- The incision is so large vertically is to allow retraction laterally so that you can get lateral enough to the tumour
- Midline avascular dissection down to bone
- Subperiosteal dissection
- Detach rectus capitis posterior minor from C1 and wipe it off so you do not dissect into the vertebral artery.
- Dissect down to foramen magnum use kerrison to made two ridge on the foramen magnum.
- Mark out the transverse sinus + confluence of sinus
- Use a size 5mm cutting burr and make two small holes at the over the edge ½ sinus and ½ over the dura
- How far apart should the holes be? Just wide enough so that it is covering the horizontal dimension of the tumour
- Drill down the inion in the midline
- Use a kerrison to cut through the bone from one of the wholes to the other. If the keel is too thick use drill to drill down again.
- Use craniotome to drill from burr hole down to the foramen magnum to protect the Transverse sinus
- At one point due to the angulation of the post fossa you wont be able to continue so come from the foramen magnum up towards the the previously craniotomed area
- Visualize the dark blue nature of the venous sinus
- Place strips of surgicel around craniotomy site with large patties covering them
- Durotomy
- Y shaped opening of dura with 15 blade and Macdonald
- The vertical stem goes towards the foramen magnum
- Placed a haemostatic suture at the midline bleeding point and pull the edge up with clip-and-cut
- Placed clip and cut in other two edges
- Haemostasis the dura edges
- Get CSF out from cisterna magna with the use of a medium brain retractor
- Use suction to withdraw CSF
- When cerebellum is relaxed go above the cerebellum and use medium brain retractor to gently pull the cerebellum down to expose the lesion.
- Debulk the lesion internally with sonapet
- When it is slightly decompressed work between cerebellum and lesion
- Find the arachnoid margin and try to dissect the lesion off the cerebellum
- There will be strands of arachnoid that are attached on the lesion
- Place patties between tumour and cerebellum
- Continue to decompress the tumour
- When there is sufficient space to see the tentorium while working between the cerebellum and tumour then you can start working between tumour and tent
- Between tumour and tent
- Here is the main blood supply and attachment
- Watchout for very adhesive attachment between tumour and tent near the transvers sinus and torcula
- If you forcefully try to remove all the tumour here you can tear the sinus or veins entering the sinus causing venous bleeding that is very hard to control as the bleeding is on the under surface of the sinus where it is hard to visualize.
- Probably best to just leave some tumour here and work with bipolar to burr in the tumour and use sonapet to wipe some tumour off carefully without going too close to the sinus
- If there is a bleeding from and near the sinus.
- DO NOT BIPOLAR IT as it can make the dural defect larger
- Tech 1: place surgicel and use a pattie on it then use a fixed retractor to put pressure on this area and go an work on other areas of the tumour and come back
- Tech 2: Use a muscle surgicel sandwich and a pattie and do what you have done above
- Tech 3: use spongostan to pack it
- Tech 4: See picture
- Blue is sinus, red is bleeding point, purple is dura, grey is suture, brown/gold is spongostan
- Basically use the suture to tamponade the spongiostan into place
- Haemostasis with surgicel, cotton balls
- Close dura with 3.0 vicyrl -no need to be water tight if cannot
- Place large surgicel ontop of dura
- Closing
- Drill holes with a craniotome drill bit and using a brain retractor
- Drill on bone flap first-make 4 holes
- Then mark on skull
- Use a nylon 3.0 needle to pass them through the holes.
- Clip and cut all the sutures
- Tie them down
Complications
- Mortality rate of 0 to 3.7%
- Morbidity rate 14 and 55%
- Complications are often transient and resolve on follow-up.
- Postoperative morbidity is related to the
- Tumour site and
- Approach selected
- CN III, IV, and V are endangered during resection of T1–T2 tumors and in subtemporal and petrous transtentorial approaches,
- Whereas CN VII and VIII are jeopardized in infratentorial T6–T7 tumors and the retromastoid approach.
- Cortical blindness after undergoing a bilateral occipital transtentorial approach for resection of a large T3–T8 tumor.
- Prolonged and pointed spatula retraction of the medial occipital lobe (calcarine area) should be avoided
Tumor site | Complication | No. of patients | Tumor site | Complication | No. of patients |
T1/2 | Hemiparesis | 3 (permanent in two) | T5 | Gait ataxia | 1 (improved) |
ㅤ | Hemianopia | 1 (permanent) | ㅤ | Hemiparesis | 1 (walking but permanent) |
ㅤ | CN III deficit | 2 (permanent in one) | T6/7 | Gait ataxia | 1 (postoperative deterioration) |
ㅤ | CN IV deficit | 2 (permanent in one) | ㅤ | Hemiparesis | 1 (resolved) |
ㅤ | CN V deficit | 1 (permanent) | ㅤ | Cerebellar swelling | 1 (decompression) |
ㅤ | Gait ataxia | 1 (improved) | ㅤ | Cerebellar abscess | 1 (surgical revision) |
ㅤ | Mental disturbance | 1 (resolved) | ㅤ | Air embolism | 4 (no sequelae) |
ㅤ | Epidural hematoma | 1 (surgical revision) | ㅤ | CSF leak | 4 (lumbar drainage in three, shunting in one) |
ㅤ | CSF leak | 2 (treated with lumbar drainage) | ㅤ | CN VII | 2 (permanent in one) |
ㅤ | Meningitis | 1 (treated with antibiotics) | ㅤ | Tinnitus | 1 (permanent) |
ㅤ | Death | 1 | ㅤ | Meningitis | 1 (resolved with antibiotics) |
T3/8 | Hemiparesis | 2 (permanent in one) | ㅤ | Transverse sinus occlusion | 3 (no sequelae) |
ㅤ | Cortical blindness | 1 (bilateral, permanent) | ㅤ | Wound infection | 2 (surgical revision in 1, antibiotics) |
ㅤ | Gait ataxia | 1 (resolved) | ㅤ | ㅤ | ㅤ |
ㅤ | Phlebitis | 1 (no sequelae) | ㅤ | ㅤ | ㅤ |
T4 | CN V deficit | 1 (partially resolved) | ㅤ | ㅤ | ㅤ |
ㅤ | Hemorrhage | 1 (surgical revision) | ㅤ | ㅤ | ㅤ |
ㅤ | Gait ataxia | 1 (permanent) | ㅤ | ㅤ | ㅤ |
ㅤ | Air embolism | 1 (no sequelae) | ㅤ | ㅤ | ㅤ |
ㅤ | Death | 1 | ㅤ | ㅤ | ㅤ |
Outcomes
- Functional outcome
- Expected to be favourable if microsurgical principles are applied.
- 75 to 86% of the patients resumed a normal life after surgery with no or minimal symptoms (Karnofsky Performance Scale [KPS] score 80 to 100).
- Serious complications requiring permanent postoperative assistance of the patient (KPS score ≤ 50) are reported in less than 5% of the cases.
- Resection rate and tumour recurrence depends on the
- Site
- Pattern of growth
- Extent of the tumour
- Simpson grade I and II removal is reported in 77 to 91% of the patients
- A complete tumour resection is usually achieved in T4 meningiomas,
- Subtotal resection
- Acceptable for
- En plaque growth
- In the T1–T2 and T5 subgroups.
- Tumor recurrence or progression after subtotal removal has been noted in 0 to 26% of the patients in larger series with a long follow-up
- Stereotactic radiosurgery may be a useful treatment option in these patients.
- A recent small series using stereotactic radiosurgery in recurrent or incidental tentorial meningiomas reported an overall tumor control rate of 98% after a (short) mean follow-up period of 3 years.
- T6–T7 tumors can usually be completely resected via a retromastoid craniotomy,
- But infiltration of the adjacent venous sinuses may prevent complete resection.
- Do not aggressivly resect an infiltrated patent venous sinus.
- Furthermore, it has been demonstrated that subtotal removal of meningioma can be associated with a long progression-free period and high quality of life.
- Recommend preservation of an infiltrated but patent dural venous sinus.
Radiosurgery
- Indicated in selected patients who are not good surgical candidates due to advanced age or significant comorbidity.
- Residual tumour
- Due to
- Infiltration into venous sinuses
- Attachment to important structure
- Location of tumour
Made with Bullet