Convexity meningioma surgery

Convexity meningioma surgery

Convexity meningioma surgery indications.

Preoperative embolization of intracranial meningioma.

see Surgical safety checklist.

see Preoperative antibiotic prophylaxis.

see Skin Preparation.

For convexity meningioma, the head is positioned so that the center of the tumor is uppermost, the same position as described for parasagittal tumors or for tumors close to the midline.

The incision and bone flap must be large enough to allow for excision of a good margin of dura around the tumor attachments.

The meningeal arteries are occluded as they are exposed.

These tumors can be removed intact by placing gentle traction on the dural attachment and working circumferentially around the tumor to divide the attachments to the cortex. However, if the surface of the tumor cannot be easily visualized without placing significant retraction on the cortex, internal decompression of the tumor is done and the capsule is reflected into the area of decompression.

In a situation where the tumor arises over the frontal temporal junction and grows into the sylvian fissure, the medial capsule and the dural attachment may extend down onto the lateral floor of the anterior fossa and anterior wall of the middle fossa, and the medial capsule of the tumor can be attached to branches of the middle cerebral artery.

A study showed that meningioma recurrence was unlikely when autologous cranioplasty was done with refashioned hyperostotic bone. This could be done in the same setting with meningioma excision. There was no recurrence at a mean of 5-year follow-up in convexity meningiomas 1).

Right Convexity Meningioma from Surgical Neurology International on Vimeo.

Left Frontal Convexity Meningioma from Surgical Neurology International on Vimeo.

An accurate and real-time model of soft tissue is critical for surgical simulation for which a user interacts haptically and visually with simulated patients. A paper focuses on the real-time deformation model of brain tissue for the interactive surgical simulation, such as neurosurgical simulation.

A new Finite Element Method (FEM) based model with constraints is proposed for the brain tissue in neurosurgical simulation. A new energy function of constraints characterizing the interaction between the virtual instrument and the soft tissue is incorporated into the optimization problem derived from the implicit integration scheme. Distance and permanent deformation constraints are introduced to describe the interaction in the convexity meningioma dissection and hemostasis. The proposed model is particularly suitable for GPU-based computing, making it possible to achieve real-time performance.

Simulation results show that the simulated soft tissue exhibits the behaviors of adhesion and permanent deformation under the constraints. Experiments show that the proposed model is able to converge to the exact solution of the implicit Euler method after 96 iterations. The proposed model was implemented in the development of a neurosurgical simulator, in which surgical procedures such as dissection of convexity meningioma and hemostasis were simulated 2).


1)

Lau BL, Che Othman MI, Fakhri M, San Liew DN, San Lim S, Bujang MA, Hieng Wong AS. Does putting back hyperostotic bone flap in meningioma surgery causes tumor recurrence? An observational prospective study. World Neurosurg. 2019 Mar 26. pii: S1878-8750(19)30863-0. doi: 10.1016/j.wneu.2019.03.183. [Epub ahead of print] PubMed PMID: 30926555.
2)

Hou W, Liu PX, Zheng M. A new model of soft tissue with constraints for interactive surgical simulation. Comput Methods Programs Biomed. 2019 Jul;175:35-43. doi: 10.1016/j.cmpb.2019.03.018. Epub 2019 Apr 1. PubMed PMID: 31104713.

Update: Cerebellar convexity meningioma

Cerebellar convexity meningioma

The tumor arises dorsal to the cerebellum, which results in the interposition of the cerebellar hemispheres between the tumor and the cranial nerves; therefore, no cranial nerves are encountered during the surgical exposure. Cerebellar convexity meningiomas are easily and accurately diagnosed via magnetic resonance imaging (MRI) or computed tomography (CT), and the surgical outcome is quite favorable.
They are usually attached to the tentorium, cerebellar or petrous dura, and may invade the transverse or sigmoid sinus.
Group A: Pure convexity meningiomas arising from the dura over the posterior convexity of the cerebellum.
Group B: Inferior peritorcular meningiomas arising from or invading the inferior wall of the torcular Herophili or the medial transverse sinus.
Group C: Parasinusal meningiomas arising in the angle beween the petrous and convexity dura. These tumors may include the wall of the sigmoid and lateral transverse sinuses. The major part of cerebellar convexity meningiomas belongs to this subgroup.
Group D: Meningiomas with secondary invasion of cerebellar convexity/fossa. This is the case of the rare intraosseus meningiomas of the posterior fossa and of other posterior fossa meningiomas with a consistent dural attachment in the cerebellar convexity 1).
Yasargil and colleagues classified cerebellar meningiomas as the fourth group of dorsal meningiomas and divided them into median, paramedian, and lateral lesions 2).

Clinical Features

There is no well defined clinical pattern characterizing these lesions. Often the patient is asymptomatic until the tumor becomes large enough to cause signs and symptoms of increased intracranial pressure and hydrocephalus.
Sometimes the patient may present with headache or progressive cerebellar dysfunction ipsilateral to the tumor.“ An elevation of intracranial venous pressure may occur in case of dural sinus invasion, expecially in the peritorcular meningiomas. For this reason, a small tumor growing inwardly into a sinus can cause early florid clinical symptoms.’ The clinical picture can be devious and mistaken for one of the more familiar diseases, particularly when false localizing signs occur. In the latter case, diplopia, trigeminal neuralgia, facial nerve palsy, hearing disturbance, tinnitus on the contralateral side, lower cranial nerve signs, truncal ataxia, and even bulbar palsy have all been reported and were attributed to the brain stem compression or to the cranial nerves stretching at the edges of dural orifices of the posterior fossa. 3).

Surgery

An adequate head position is important to keep intracranial venous pressure relatively low.
The head is positioned higher than the heart, tilting the cranial half of the operating table about 30 to 45 degrees.
Group A meningiomas can be approached with the patient in the prone position and with the head slightly flexed. A linear or a reverse U-shaped skin incision can be used.
The incision is carried through all layers of the scalp and pericranium, which are then elevated and held retracted over a rolled sponge.
The craniotomy can be uni- or bilateral according to the location of the tumor and of the invasion of the occipital sinus that can be sacrified. Removal is accomplished by a repetitive series of internal debulking and extracapsular microdissection. A careful dissection of the tumor from the surrounding cerebellar cortex and cortical vesels is needed to avoid damage of the vermian branch of the posterior inferior cerebellar artery and of cerebellar venous drainage, which can cause postoperative cerebellar strokes or edema.
Group B meningiomas can be approached with the patient in prone position. In cases with secondary supratentorial inva-sion, the Concorde position may be useful for performing a combined suboccipital/transtentorial/occipital approach:
The skin incision varies according the number of peritorcular quadrants containing tumor. After suboccipital craniotomy, a piecemeal rongeuring of bone is the safest method of dural
see more 4).

Case reports

A case of left sided convexity cerebellar meningioma associated with right trigeminal neuropathy in a 63-year-old lady is presented. Suboccipital craniectomy (left) and near total removal was done. The hypoaesthesia of right hemiface disappeared totally at the time of discharge 5).
1) , 3)

Delfini R., Santoro A., Pichierri A. (2009) Cerebellar Convexity Meningiomas. In: Lee J.H. (eds) Meningiomas. Springer, London
5)

Ghosh K, Ghorai SP, Saha S, Roy S. Contralateral trigeminal neuropathy in a case of convexity cerebellar meningioma. J Indian Med Assoc. 2010 Sep;108(9):602-3. PubMed PMID: 21510535.
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