PARASAGITTAL MENINGIOMASCoordonator conf. dr. Ligia

Tătăranustud. Lascăr Octavian-Toma

General informations

tumors that fill the parasagittal angle, without brain tissue between the tumor and the superior sagittal sinus(SSS)

21 to 31% of intracranial meningiomas tend to occur where arachnoid

granulations are denser a higher incidence of malignant

meningiomas has been reported compared with meningiomas in other locations

59% located in the right side

Clasification

1. According to their location along the SSS:-located in the anterior third(12,8%)-

between crista galli and the coronal suture

-located in the middle third(69,2%)-between coronal suture and lambdoid suture

-located in the posterior third(17,9%)-between lambdoid suture and the torcula

Parasagittal (anterior third) and falx meningioma

Meningioma in the middle third

Meningioma in the posterior third

Clasification2. According to histopathological types:

Vascularization

multiple sources of vascularization: -meningeal arteries from extern carotid

artery -ethmoidal arteries from intern carotid

artery -cortical arteries

Symptoms

related to the proximity of the lesion to the Rolandic fissure

-sensory or motor seizures involving the contralateral lower extremity

-contralateral hemiparesis -parasthesias papilledema- optic disc swelling that is

secondary to elevated intracranial pressure (fundus eye exam is recommended)

-dementia

Symptoms

tumors arising from either the anterior or posterior third can remain undetected for long periods until mass effect triggers noticeable symptoms

-lesion in the anterior third-headache and frontal lobe syndrome

-lesion in the posterior third-homonymous hemianopsia

Diagnostic evaluation

CT-beneficial in cases in which either hyperostotic or lytic calvarial changes are expected. Is also used for prosthetic implants after surgery.

MRI-gives informations about the size, consistency of the lesion and the relationship with the falx, meninges, cortex, vascular structures

MRI+MRA(angiography)-gold standard. MRA is used for the visualization of the arterial, venous anatomy, collateral venous drainage patterns that develop following sinus occlusion.

Treatment

Preoperative consideration1.Embolization-used as an adjuvant therapy

to reduce intraoperator blood loss and for devascularization and subsequent necrosis of the tumor.

SINDOU AND ALVEMIA CLASIFICATION

-used to guide surgical decision making and preoperative planning based on six

categories:

Operative approach1.Position

in anterior third tumors, the patient is positioned supine with the head slightly flexed

in middle third tumors, the patient is positioned supine or lateral with the tumor positioned as the highest point in the vertical plane

in posterior third tumors, the patient is positioned semisitting, lateral, prone position with the tumor bellow the horizontal plane

under the influence of the gravity, the ipsilateral cerebral hemisphere is retracted , which facilitates dissection, particularly in lesions with significant falcine attachments

Operative approach2.Incision

-in anterior third tumors is used a bicoronal skin incision

-in middle third tumors is used a trapdoor or horseshoe incision

1-position for the anterior third tumor2-position for the middle third tumor

3-position for the posterior third tumor

Operative approach3.Craniotomy

Direct visualization of the sinus wall during dissection is the primary principle of the craniotomy. Special attention is given to the contralateral dura and adjacent veins, and osteotomies over the SSS are performed last.

Elevation of the bone flap can be complicated by engorged diploic anastomosis and by frequently encountered invasion of the dura and bone by the tumor.

3.Craniotomy

Operative approach4.Dural opening and resection

Dural opening: -made a semilunar dural flap along the SSS under direct microscopic visualization of the pial surface to avoid injury to the cortical draining veins

the dural incision is made lateral from the tumor

Operative approach4.Dural opening and resection

Resection: -dissection is initiated by visualization

and preservation of the tumor capsule on the lateral margins

-if the tumor has reached the pial surface, gentle dissection with selective bipolar coagulation is used to separate the capsule

Operative approach4.Dural opening and resection

all vascular structures must be identified and followed to determine their contribution to the tumor vasculature before coagulation because pericallosal and callosomarginal branches are frequently parasitized by these tumors and supply the inferomedial aspect of the lesions

injury to critical venous structures ( rolandic veins) can occur during dissection, and the surgeon must be prepared for a venous reconstruction to avoid a devastating venous hemorrhagic stroke in eloquent cortex

in cases that require SSS wall reconstruction, an end-to-end venous graft to the stump of the bridging vein can be performed

Operative approach5.Dural closure

made with pericranial graft hervested during the opening

fascia temporalis dural substitute such as allogenic human

skin

Complications

postoperative hematoma severe blood loss carotid thromboses pulmonary embolisms surgical site infections air embolism is influenced by the pacient

position

Tumor recurrence

can affect all histopathological grade tumors

tend to recur more frequently than meningiomas at other locations

increased risk of recurrence for younger patients

there is a relationship between extend of the resection and recurrence rates

Thank you!