Clival and petroclival meningiomas

Localisation

Location is medial to the internal auditory meatus and posterior to the Gasserian (trigeminal) ganglion.

Features	Clival	Petroclival
Dural attachment	- Upper two thirds of the clivus - Close to the midline	- Upper two thirds of the clivus - Centered on the petroclival junction.
Displacement	Brain stem posteriorly	Displace the brain stem and basilar artery posteriorly and to the contralateral side.

Petroclival meningiomas

Usually present as large tumors when they become symptomatic
Invasion of the posterior aspect of the cavernous sinus, parasellar region, tentorium, or foramen magnum is not uncommon.

Nomenclature	Origin	Brainstem and basilar displacement	Cranial nerve involvement
Petroclival meningiomas	- Upper 2/3 of clivus - Originate medial to CN5 and posteriorly to the Meckel’s cave.	- Brainstem and basilar displaced posteriorly and contralaterally	- CN5 displaced laterally - CN6 displaced medially - CN7/8 displaced laterally
Clival meningiomas	- Upper 2/3 of clivus - Arise at midline - medial to the CN6 and may extend to the cavernous sinus	- Brainstem displaced posteriorly - Basilar displaced posteriorly or encased	- CN displaced laterally
Petrous face meningiomas	- Arise at petrous bone lateral to CN5	- Brainstem and basilar displaced laterally	- Anterior petrous: CN7/8 displaced posteriorly - Posterior petrous: CN7/8 displaced anteriorly
Petroclivalsphenoidal meningioma	- Upper 2/3 of clivus - Originate medial to CN5 - Grow from posterior cranial fossa to middle cranial fossa, infratentorial to supratentorial	- Brainstem and basilar displaced posteriorly and contralaterally	- Invades Meckel’s cave
Sphenopetroclival meningioma	- Upper 2/3 of clivus - Grows from middle cranial fossa to posterior cranial fossa	- Brainstem and basilar displaced posterior and contralaterally	- Subtype 1: originates within cavernous sinus - Subtype 2: originates from lateral wall of cavernous sinus

Numbers

2% of all intracranial meningiomas

Affect middle aged and older women

Clinical features

Tumor (diameter) size varies greatly at the time of diagnosis

< 2cm least common scenario.
2 to 4 cm.

Most common size on presentation

>4 cm

Second most common

The onset of symptoms

The onset of these tumors is insidious, with patients developing headaches and gait problems.
Cranial nerve palsies → cerebellar + brain stem compression signs

Compressive symptoms

Brainstem compression
Cerebellar compression
Cranial neuropathies

Common

Most common
Trigeminal neuralgia, facial pain, or varying degrees of facial hypesthesia or frank anesthesia

Diplopia, hearing loss, and vertigo

Less common

Dysphonia facial weakness, and dysphagia

Visual loss

Cavernous sinus involvement through the Meckel cave.

Patients may be symptomatic for prolonged periods of time before the patient is imaged and the diagnosis is made
A low threshold should exist for imaging patients exhibiting compatible symptoms.

A slow onset of obstructive hydrocephalus

Natural History

Deaths caused by tumor growth only in a minority of patients.

An increase in tumor growth rate often precedes a clinical deterioration.

Tumour growth

A great variability in growth patterns exists between different tumors, and growth patterns for individual tumors are not linear.
After surgery + adjuvant radiotherapy

Overall tumor recurrence or progression has been observed in 13% of patients at 6 years

Untreated or subtotally resected petroclival meningiomas

0.81 mm/ year to 0.37 cm/year.
Radiological tumor growth in 76% of patients at 4 years.
42% of tumors showed radiological progression over 4 years with a faster growth pattern.
Tumors’ mean doubling time was 8 years.
No radiological tumor growth in 24%-58% over a 4-year period

Conservative observation may be justified in asymptomatic elderly patients when close radiological follow-up can be performed.

Older patients and those who have gone through menopause seemed to have slower-growing tumors.

Radiology

MRI

Similar meningioma radiological characteristics

Isointense extra-axial lesions on

T1+C

Enhance homogeneously
Dural tail

Variable intensity

Fat suppression imaging techniques FLAIR

Useful in differentiating tumor involvement of bone from normal marrow in selected cases.

FLAIR hyperintesity indicates disruption of the pial surface

Expect adhesion to the brainstem and its vascular supply
Subtotal resection is advised.
Occurs in 1/3 cases

CT

Scan of the skull base

To identify extension of the tumour into the

Internal auditory meatus or
Meckel cave

DSA

Identify

Venous sinus patency
Anatomy of temporal draining veins
Tumour blood supply

Embolisation

Direct feeders from the posterior circulation
Meningohypophyseal trunk of the internal carotid artery.
Rarely done

Risks with embolisation of meningiomas in this location,

An angiogram with a balloon test occlusion of the carotid artery may be necessary in cases of young patients with symptomatic cavernous sinus involvement in which a high-flow bypass is contemplated before a radical resection.

Management

General

Results of microsurgical resection have greatly improved over the last 2 decades, and the efficacy of radiosurgery has further augmented treatment options.

Management Algorithm

Patient Age	Small tumor (< 3 cm)	Large tumor (> 3 cm)
Young	MS GTR	1. No radiographic evidence of cavernous sinus involvement: MS GTR 2. Radiographic cavernous sinus involvement: - CN: STR and observation of residual or radiosurgery of residual + CN: MS GTR
Old	Symptomatic: MS GTR vs radiosurgery Asymptomatic: Observation vs radiosurgery	STR of symptomatic mass followed by: 1. Observation if MRI is stable 2. Radiosurgery if radiological progression

Abbreviations: CN, cranial nerve palsy; GTR, gross total resection; MRI, magnetic resonance imaging; MS, microsurgery; STR, subtotal resection.

Conservative

Once tumour progression has been documented, delay of treatment is not warranted because it may precede a neurological decline.

Surgery

General

Gross total resection should only be attempted if it can be done safely.

Resection of tumor in the cavernous sinus or parasellar region is not warranted at the time of first resection,

Radiosurgery or radiotherapy should be used as adjuvant therapy in cases of residual tumor progression

Indications

Should be contemplated in

Young patients with rapidly growing tumors
Tumors with brain stem compression, or
Cases where the diagnosis of a benign lesion might be in doubt.

Aims

Decompress brain stem with minimal damage to the cranial nerves

Surgical difficulties

Central location of the tumours medial to the cranial nerve foramina

Difficult to get gross total resection

Can lead to higher surgical morbidity
Difficult tumours to resect because

Cranial nerves are interposed between the surgeon and the tumor
Intimate relationship between the brain stem vascular supply and the tumor.

Preoperative Evaluation

Look for relationships of the tumour vs:

Basilar artery

Encased in the tumor in many cases

Cavernous sinus

Extension of the tumor into the cavernous sinus seems to be very common

Parasellar region
Internal auditory meatus

Less likely

Tentorium cerebelli

Tumor may also extend past

Extension of the tumor to the midline of the clivus

Occurs in ~20%
Makes surgical resection more difficult.

Jugular tubercle

FLAIR hyperintesity indicates disruption of the pial surface

Expect adhesion to the brainstem and its vascular supply
Subtotal resection is advised.
Occurs in 1/3 cases

Adjunction

Electrohysiological monitoring

Somatosensory evoked potentials,
Electroencephalography,
Motor evoked potentials,
Facial nerve monitoring,
Brain stem auditory evoked responses.
Electromyographic endotracheal tube

Cranial nerve (CN) X monitoring

Electrodes placed into the sternocleidomastoid muscle

Can provide monitoring for CN XI.

Navigation

Surgical approaches

Selection of approach depends on

Surgeon preference
Optimize tumour exposure with adequate visualisation of the dissection planes
Limiting the need for brain retraction and the possibility of injury to cranial nerves and vascular structures
Ability to decompress the brainstem

Pterional and suboccipital approaches

Provide access to the tumor with a narrow central corridor

Dissection of the tumor in its periphery under direct visualization is limited.

Skull base approaches

Provide a more direct route to the tumor and may extend the exposure with a better anterior view of the brain stem

Anterior petrosectomy

Can be combined with a

Pterional approach or
Subtemporal approach (extended middle fossa approach)

To provide better access to the tumor in its infratentorial compartment.

Indication

When tumors crossing the midline
When the central clival depression needs to be accessed

Technique

Extradural approach

Should be used up to the outer layer (dura propria) of the lateral wall of the cavernous sinus, which is elevated extradurally to the gasserian ganglion and the inferior aspect of V3 to the foramen ovale.
Elevate dura from posterior to anterior to prevent damaging and avulsing the GSPN

Bony removal is limited to the Kawase triangle

Limited

Anteriorly by V3
Laterally by the greater superficial petrosal nerve and internal carotid artery
Posteriorly by the internal acoustic canal
Medially by the petrous edge

GSPN rcuate eminence Petrous ridgc Gasserian gang. —GSPR' Petrous ridge T&nwal Lobe Kawase's Triangle MDK Rhomboid MOK

The dural opening should then be parallel to the base of the temporal lobe followed by ligation of the superior petrosal sinus anterior to the drainage of the vein of Labbé.
The tentorium is divided, offering a combined supra- and infratentorial access.

The infratentorial component of the tumor can be removed above the internal acoustic meatus, and the approach provides a good view of the anterior surface of the brain stem.

Risk

Injury of trigeminal nerve is possible because of its central location in the surgical corridor.
CSF leaks
Hearing loss
Decreased tearing
Facial nerve palsy
Temporal lobe injury secondary to

Brain retraction
Sacrifice of the superior petrosal sinus.

Posterior petrosal approaches

Expose the middle fossa as well as the posterior fossa in a presigmoid fashion and address the tumor laterally and inferior to the internal acoustic meatus

Varying degrees of temporal bone can be removed based on the patient’s preoperative hearing status

Retrolabyrinthine approaches

Preserves hearing by leaving the otologic structures intact.

Translabyrinthine approaches

Drilling of the semicircular canals

Sacrifice of hearing

Reserved for patients who do not have serviceable hearing (speech discrimination score inferior to 50% or hearing loss greater than 50 dB on formal audiogram testing).

For a more anterior trajectory to the tumor

Transcochlear approaches

Drilling of all otologic structures as well as transposing the facial nerve posteriorly to maximize the surgical view.

Sacrifice hearing

Reserved for patients who do not have serviceable hearing (speech discrimination score inferior to 50% or hearing loss greater than 50 dB on formal audiogram testing).

The superior petrosal sinus is sacrificed in all posterior petrosal approaches but care should be taken to preserve the drainage of the vein of Labbé.

The tentorium should only be divided anterior to the drainage of the vein of Labbé, which may drain directly into the sigmoid sinus or the superior petrosal sinus.

Benefits

Offer a more direct trajectory to the tumor with minimal retraction on the temporal lobe and cerebellar hemispheres.
Earlier interruption of the tumor’s blood supply is also feasible due to a more anterior surgical trajectory.

Complications

CSF leaks

More prominent in the posterior petrosal approaches than in anterior approaches
Can be treated with temporary drainage in most cases
Avoided by

At the time of closure, the dura should be closed, and a fascia lata graft may be necessary.
Packing the defect created by the mastoidectomy with fat is often necessary, and care should be taken not to create mass effect on the dura.

Hearing loss

Hearing preservation has been reported in up to 92% of patients with petroclival meningiomas treated with a posterior retrolabyrinthine petrosal approach.
Partial resection of the posterior and superior semicircular canals may still preserve hearing and improve midline access, obviating the need to perform a full translabyrinthine approach.

Facial nerve paresis.

A transcochlear approach improves midline exposure at a higher risk of permanent facial palsy secondary to ischemia of the nerve if the nerve is translocated. Because of the high incidence of facial nerve palsies in these approaches and the opportunity to access the midline structures through an anterior petrosectomy, the usefulness of the translabyrinthine and transcochlear approach in the context of petroclival meningiomas has been questioned.

Cautions

Venous anatomy may alter the effectiveness of a posterior petrosal approach.

A high jugular bulb may limit the size of the presigmoid corridor, severely limiting the benefit of the approach.
Variations in the draining of the vein of Labbé also alter the posterior extent of the cut through the tentorium.

Preoperative MRV and CTA can more accurately predict the usefulness of posterior petrosal approaches

Coagulation should be avoided in the close vicinity of the brain stem, and copious irrigation may be preferable to accomplish hemostasis.
A complete resection of the tumor against the brain stem may be dangerous in cases where the tumor is adherent or has parasitized the blood supply to the brain stem.
Several papers still advocate the use of a suboccipital retrosigmoid craniotomy for petroclival meningiomas without supratentorial extent because there is typically less morbidity with this approach.

Combined petrosal approach

Supratentorial access with an anterior petrosectomy and

Infratentorial retrolabyrinthine presigmoid access

Tumour resection

Regardless of the approach used, tumour removal is performed in a piecemeal fashion.

Tumour distortion of anatomy

Inspection of the inferior part of the tumor should permit visualisation of the vertebral artery, posterior inferior cerebellar artery, and cranial nerves IX through XI

The fourth and fifth cranial nerves are usually displaced toward the superior end of the tumor

The sixth cranial nerve

Is usually displaced medially to the tumor and is encountered in the later stages of the dissection.
If damage put a single suture to bring the two ends together

Patient can heal

The seventh and eighth cranial nerve complex may be displaced laterally to the tumor or can be embedded in the tumor

Surgical outcome

Gross total resection

Rates vary greatly: 20% - 79%
Factors affecting gross total resection:

Cavernous sinus involvement
Vascular involvement
Cranial nerves involvement at their cranial foramina.

Somatosensory symptoms usually improve long term, but the evolution of cranial neuropathies is less predictable because of the small numbers of patients in each series

Increased risk factor for surgical morbidity:

Peritumoral edema
Extension of the tumor to the lower cranial nerves

Surgical results of different series are difficult to compare because

Heterogeneity of these tumors in their invasion of adjacent structures.
These are rare tumours
Some centers have opted for a less aggressive surgical intervention, with decreased postoperative morbidity.

Perioperative mortality rates

0 to 7%
Mainly due to a poor neurological outcome secondary to a brain stem stroke.

Morbidity

Cranial nerve palsies

Most common complication after treatment of petroclival meningiomas

New or worsening of pre-existing cranial nerve palsies occur in up to 76% of patients.

CN4 → CN3 → CN8
Injury to lower cranial nerves is less commonly observed

Results in a significantly decreased functional state, which may require the use of a tracheostomy or gastrostomy.

The cranial nerve palsies may be transient in nature, and long-term outcomes for patients with cranial nerve palsies appear to return to at least preoperative status,8with improvement seen in some series.

Risk

Related to the aggressiveness at surgery
Preoperative imaging characteristics

Presence of peritumoral edema,

Prior surgery
Preoperative cranial nerve palsies
Operative findings (e.g., fibrous tumor)

A fibrous and adherent tumor, whose characteristics may be suspected preoperatively based on the presence of brain stem edema, should prompt the surgeon to limit aggressiveness.

Brain stem injury

Due to dissection of the tumor off its pial surface or vascular supply

Devastating consequences resulting in serious morbidity or death.

Recurrence

Recurrence and progression rates after the surgical resection of petroclival meningiomas 0 to 42%

Some studies vary in their definition of recurrence or progression based on clinical or radiological criteria.

Tumor recurrence risk

Less extensive surgical resection,
Malignant histopathological results
Cavernous sinus involvement.

Length of followup in most studies remains short, and the incidence with which radiosurgery is used postoperatively also varies among studies.
The best long-term (6 to 8 years) for surgical resection + radiosurgery recurrence or progression rates of 4.5 to 22%

Radiosurgery

General

Most effective at treating tumors whose diameter is less than 3 cm.

If volume of residual tumor is too large for radiosurgery

Conventionally fractionated radiation therapy using three-dimensional conformal (3DCRT) or intensity-modulated techniques (IMRT) provides equally good long-term tumor control.

Indication

Can be used as the primary treatment method in

Elderly patients
Asymptomatic patients
Patients without significant brain stem compression

Controlling progression of residual tumor.

Outcome

Failure of radiosurgery after microsurgery in controlling residual disease has been reported to be as low as 0% -13% at 3-4 year follow-up

This clearly compares favorably with progression rates of residual tumor of 42% at 4 years.
The efficacy of radiosurgery has prompted surgeons to be less aggressive in resecting tumor extension into the cavernous sinus or to accept a subtotal resection in cases of high risk of postoperative morbidity.

Morbidity

Transient new cranial nerve palsies: 6% of cases
Permanent new cranial nerve palsies: 5% of cases.

No mortality has been reported

Brain stem injury:

In the form of worsening of neurological function can be permanent in up to 6% of cases.

Radiosurgery as a primary treatment modality

100% control rate of petroclival meningiomas by MRI criteria, mean follow-up 3 to 4 years.
Clinical outcomes

Improvement of neurological function in 96 to 100% of cases
Improvement in cranial nerve function in 50% of cases

These series are difficult to compare with microsurgical series because

They are still limited in number
Have inadequate follow-up
A higher proportion of cases in which the patient has undergone radiosurgery as a primary treatment have been asymptomatic in these studies compared with surgical series.