PARASAGITTAL MENINGIOMAS Coordonator conf. dr. Ligia Tătăranu stud. Lascăr Octavian-Toma
Jan 19, 2016
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!