A petrosal oblique meningioma is a meningioma that originates from the petrosal-oblique cleft, centered on the middle and upper slope and the petrosal bone on the medial side of the trigeminal nerve.
Due to the hidden location and complex anatomical structure of the petrosal oblique area, the tumor compresses the brainstem and the nerves and blood vessels at the base of the skull, which is considered to be one of the most difficult diseases in neurosurgery.
There are many surgical approaches, high postoperative tumor residual rate, poor prognosis and other phenomena still exist, and the blind pursuit of total tumor resection during surgery is also the main factor leading to high postoperative mortality rate and high disability rate.
Therefore, it is difficult to formulate an individualized optimal surgical approach according to the location and nature of the tumor during surgery, fully expose the tumor and surrounding important structures, reduce the traction of brain tissue, avoid damage to peripheral nerves and blood vessels, reduce postoperative complications and new neurological dysfunction, and achieve a high tumor resection rate while improving the long-term quality of life of patients.
Myth: Many patients will confuse meningioma in the petrosal slope area with meningioma in the slope area, resulting in the need for the doctor to repeatedly confirm the condition and delay the diagnosis and treatment time in the process of communicating with the doctor for a second opinion.
Petrol slope meningioma refers to the area surrounded by the sphenoid bone, temporal bone and occipital bone, and can be divided into cavernous sinus meningioma, middle fossa meningioma, pontine cerebellar angle meningioma, petrosal tip meningioma, slope meningioma, occipital foramen magnum meningioma, etc., and the tumor located in the 2/3 slope of the posterior fossa and the petrosal crest within the internal auditory canal is difficult to operate because of its location deep in the skull base, the tumor is close to the posterior cranial nerve, basilar artery and its branches, cerebellar hemisphere, brainstem and other important structures. Posterior fossa meningiomas account for 10% of all intracranial meningiomas. In the posterior fossa meningioma, petrosal-slope meningioma accounts for about 50%, and there are more females than males, and the female:male ratio is about 2:1, and the age of onset is mostly middle-aged or older. Some scholars divide tumors into three types according to the location of tumors, growth directions, clinical manifestations and surgical approaches:
1. Petro-oblique meningioma: the tumor extends from the lithoscopic slope cracking to one side. The tumour is mainly located on the middle slope and cerebellar pontine angle. The tumor is mainly supplied by the pituitary xerosis, the occipital branch of the vertebral artery, and the petrous branch of the slope artery.
2. Slope meningioma: spider cells grow in the cracked dura of the petrosal slope and develop to the opposite side of the midline. The tumour is predominantly located on the mid-upper slope, compressing the midbrain and pons posteriorly. The blood supply consists of dry meningopituitary gland, meningeal branches of the middle meningeal artery, and slope branches of the vertebral artery.
3. Sphenoidal slope meningioma: the tumor grows from the slope of the sphenoid bone, extends to the sella sphenoid, middle cranial fossa, and petrosal tip, and develops through the tentorial hiatus to the saddle dorsal. Cerebral angiography showed that the meningopituitary gland was dry, the meningeal branch of the middle meningeal artery, and the slope branch of the ascending pharyngeal artery were involved in blood supply.
There are six major difficulties in the operation of meningioma in the petrosal oblique area
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1. The anterior and upper parts of the brainstem mainly involve important tissue structures such as the third ventricle, hypothalamus, pituitary gland, and cerebral basilar artery ring.
2. The posterior and upper part of the brainstem mainly involves the pineal gland, cerebellar tentoria, cerebral vein and other tissue structures, and the tumor is generally prone to compress the midbrain aqueduct to cause symptoms such as hydrocephalus and difficulty in seeing upward, and the treatment methods adopted are different according to the nature of the tumor.
3. The anterior part of the brainstem mainly involves the petrosal slope, basilar artery, cranial nerve and other tissue structures, and the preoperative symptoms are mostly mild and the course of the disease is long, but the location of the tumor is deep and the operation is difficult.
4. The lateral side of the brainstem mainly involves tissue structures such as pontine cerebellar angle area and jugular foramen area, which is difficult to be exposed by surgery.
5. The posterior part of the brainstem mainly involves the fourth ventricle, cerebellar vermis, cerebellar foot and other tissue structures, and tumors are generally prone to cause symptoms of hydrocephalus and intracranial hypertension, and tumors can invade the brainstem.
6. The lower part of the brainstem mainly involves the foramen magnum, vertebral artery and other tissue structures, and the tumor is easy to cause dyspnea, hydrocephalus, intracranial hypertension, etc., because it affects the medulla oblongata, the operation requires finesse.
Case 1: Posterior sigmoid approach
A 48-year-old woman with a large petrosal oblique meningioma extending to the jugular foramen began to develop progressive hearing loss, dysphagia and diplopia three years ago, and the neurological examination on admission showed no abnormalities, and the preoperative MRI showed that the tumor extended below the foramen magnum and extended on the medial wall of the cavernous sinus, as well as a small tumor extension of the foramen jugular venous. Professor Ba resected the tumor through the posterior sigmoid sinus (RS) approach, with no nerve damage during the operation, no new permanent complications after the operation, and MRI examination proved that the tumor was completely resected. Two days after surgery, the patient was transferred to a general ward; At the time of discharge, her only symptom was hearing loss on her left side, and MRI follow-up was recommended within 6 months.
Case 2: Anterior sigmoid transtentorial approach to the sigmoid sinus
The 33-year-old woman had a meningioma in a large lithosque area on the right side of the brain, which extended into the Meckel cavity. On the magnetic resonance image, the brainstem is visibly compressed. Professor Ba used the anterior sigmoid sinus approach to completely remove the tumor, and although part of the tumour capsule adhered to the nerve structure, the nerve was still preserved and all blood vessels were intact at the end of the operation. The patient quickly woke up and had the endotracheal tube removed. For the first 24 hours, she did not have any defects, and on the second day after surgery, left hemiplegia and facial paralysis developed and appropriate treatment began. Over the next 4 weeks, she made a full recovery and was discharged from the hospital with no neurological deficits.
1. Posterior sigmoid sinus approach and its modification
The posterior sigmoid approach is suitable for petrosal oblique area meningiomas that extend over a large area like the posterior fossa. It is a simple and quick surgical approach that is familiar to most neurosurgeons and avoids many of the complications associated with intraoperative temporal lobe traction, such as venous infarction, and the modification of the approach allows the surgeon to access the part of the fossa and Meckel's cavity (if the tumor is not extensive). The main disadvantages of this method are the deep surgical field and the fact that the central nervous system VII-VIII is often operated outside the surgical field, so it is easy to cause postoperative facial paralysis. Another disadvantage is that it has only one approach and a narrow working area compared to other approaches, such as combined petroid abrasion, which allows for a larger surgical field of view and multiple trajectories to separate the tumor from key neurovascular structures. Drilling in the epidural remains a challenging procedure, and tumor resection is based on traction due to limited visualization of the Meckel cave, and therefore relies on adhesion between the tumor and cranial nerves. Finally, the posterior sigmoid approach is also less likely to undergo extensive devascularization of the proximal basal vessels prior to tumor resection than the transpetrol approach.
The supratentorial cerebellar approach is a variant of the classical posterior sigmoid approach with minimal modification of craniotomy. In fact, both the posterior sigmoid approach and the supratentorial approach of the cerebellum can be used. The superior cerebellar approach is indicated for meningiomas whose tumors originate in petrosal oblique regions above the internal tract. It has the advantage of being easy to craniotomy, and the posterior sigmoid sinus approach allows early identification of the tumor-brainstem interface at the upper limit of the tumor, and better control of CNs VII/VIII located at the lower limit of the surgical field. One of the major drawbacks of the posterior and lateral superior cerebellum of the sigmoid sinus is the difficulty of managing the lateral wall of the cavernous sinus and protruding anteriorly into the fossa, which may require a two-stage surgery. However, endoscopic assistance requires special surgical equipment and skills that can overcome some of the limitations of the posterior sigmoid approach and allow direct visualization of dead spaces such as the Merkle cavity, inferior slope depression, and mid fossa. Some authors also believe that since the body of the tumor is lower than the upper position, the use of a semi-sitting position can help remove the tumor, improve brain relaxation, and reduce venous congestion and hemorrhage.
2. Entrance Road
The anterior temporal approach is usually based on a frontotemporal craniotomy plus removal of the lateral orbital margin or zygomatic bone. Anterior temporal craniotomy is one or two excisions depending on the extension of the lesion. The next step is epidural processing, which aims to create a surgical field with the critical manipulation field between the lateral wall of the stripped cavernous sinus. This approach separates the intracavernous part of the tumour (the part that should be left behind) from the intradural part (the part that should be removed). Other advantages of this approach are the avoidance of intradural temporal lobe traction and control of the basilar artery from the middle meningeal artery and the middle cerebral artery. It is best suited for sphenoid spiny-cavernous sinus-petrosus slope meningiomas with a predominance of the middle cranial fossa and cavernous sinus. The main surgical complications of this approach are oculomotor and trochlear nerve damage, as well as the difficulty of resecting tumors below the level of the internal auditory canal. Even with some later modifications, such as the anterior temporal transMekel cavity approach, the inferior slope area cannot be accessed.
3. Rock Bone Entry Road
The transpetrosal approach includes anterior petrosectomy, posterior petrosectomy, or a combination of both. Professor Takatoku Fukushima and Professor Kawase, two members of the INC's World Advisory Group on Neurosurgery (WANG), have already dug deep into the Iwamae approach and is an option in cases where the meningioma in the petrosal oblique area does not extend downward or laterally into the internal auditory canal. Control of the auditory/facial nerve (CNs VII/VIII) can be achieved by triangular drilling behind the ear between the IAC and the superior semicircular canal and the use of an endoscope. Adachi et al. describe exceptions to this general rule, primarily based on the assessment of the supplying arteries. Professor Kawase et al. believe that the anterior petrosal approach reduces the risk of facial nerve palsy, hearing loss, and cerebrospinal fluid leakage compared to the postpetrosal approach. However, there is still a risk of damage to the superficial petrosal greater nerve (GSPN) and geniculate ganglion (GG), primarily due to facial paralysis due to dehiscence of the superficial petrosal greater nerve, avulsion of the geniculate ganglion from the geniculate ganglion, or posterior-to-anterior traction of the geniculate ganglion.
In addition, due to the small surgical field, dural suturing is difficult; For this reason, most authors use autologous fat for closure, with a low rate of CSF leakage even in the presence of gasification of the petrosal apex. Last but not least, litropreabrasis involves prolonged temporal lobe contraction, which can lead to temporal lobe edema and cognitive impairment.
With regard to petrosal resection, there are differently named subclassifications in the neurosurgical and otological literature according to the amount of temporal bone resection. It can be simplified to: post-labyrinthed, extralabyrinthal, transcochlear. The key concept of this approach, highlighted by Professor AlMeft, is the displacement of the sigmoid sinus junction in order to create a posterior-to-anterior, outer-in-inside, bottom-up surgical passage under the temporal lobe towards the basal cistern, and also to provide good control of the lower part of the lesion and cranial nerves VII, VIII, IX, X, and XI. The sigmoid sinus can be opened by incision of the dural incision above the transverse sinus (TS), anterior to the sigmoid sinus (SS), and by incision of the superior petrous sinus (SPS) and canopy.
For petrosal oblique meningioma, the postpetrosal approach is often combined with the anterior petrosal approach, also known as the petrosal symphysis approach. The petrososal symphysis approach provides multiple surgical perspectives for tumors and critical structures, and can deflow some of the major supplying arteries through the electrocondensed postdura mater and canopy. One of the key steps in the joint petrosal approach is the incision of the canopy, which is an important component of dural attachment for most petrosal oblique meningiomas. This procedure uses electrocoagulation to coagulate the cerebellar tentor from the middle cerebral artery to cut off the flow of the tumor and open surgical access to the tumor.
The advantages of the transpetrosal approach are shortened access distance, early interruption, reduced need for cerebral traction, and the possibility of using multiple fields of view during resection. However, the main disadvantages of this surgical approach are the technically demanding, time-consuming, and increased risk of complications such as pulmonary embolism or venous sinus thrombosis and cerebrospinal fluid fistula. In addition, they are at risk of hearing loss.
4. Endoscopic transnasal approach
Over the past few years, a large number of anatomical studies have been published on the access of the transnasal enlarged approach (EEA) into the rocky slope area. These studies have used EEA to access this complex area with the aim of avoiding cerebral traction and reducing cranial nerve injury across the surgical field, particularly when using the posterior approach to the sigmoid sinus. Van Gompel et al. studied endoscopic anterior petrosectomy and found that the endoscopic anterior petroscopection had a smaller surgical field than transcranial anterior lithotomy. The limitations of the endoscopic petrosal approach were later confirmed by the same group. Other authors have pointed to the location of the cranial nerves as a key factor in the selection of a surgical approach. In true petrosal slope meningioma, CN VI is often displaced medially, making the EEA inappropriate. Mid-slope tumors originating from the midline are rare, but they tend to be mediatally displaced by CN V and CN VI, making them good candidates for EEA. There are clinical experiences with the use of EEA for the resection of petrosal slope meningioma rarely, with a recent article by Gardner et al. reporting a high rate of cerebrospinal fluid leakage (28.1%) and a very low rate of total tumor resection (18.8%).
Screenshot of the speech of Professor Froelich of France at INC: Schematic diagram of transnasal endoscopy
Summary of the application of surgical approaches to meningioma in the petrosal oblique area
Petrooblique meningioma can be divided into 2 subtypes: midline and lateral. This distinction is based on the major site of dural attachment and the pattern of CN deviation. Meningiomas originating from the meningeal layer of the oblique area of the dural petrosal region easily invade the Meckel cavity and cisterna and often do not have a clear anatomical plane between the tumor and the central nervous system. This is especially true of the abducens nerve. Petrosal oblique meningioma is one of the most controversial entities in the choice of surgical approach, especially when choosing between craniotomy and intranasal approaches. When choosing an approach to the intradural portion of the petrosal oblique, the location of key neurovascular structures associated with the lesion, including the abducens and trigeminal nerves, must be considered.
Due to the particularity and diversity of tumor growth and invasion sites, there are various surgical approaches to petrosal oblique meningioma. Each surgical approach has its own advantages and disadvantages, and the most suitable approach is the best approach; It is not possible to expand the scope of adaptation in order to try a new and difficult approach; The use and performance of surgical skills should be based on bringing the greatest benefit to the patient. The choice of surgical approach needs to consider the location, size, invasion site, degree of brainstem compression, blood supply to the tumor, and the patient's age, preoperative hearing, and facial nerve function. The ideal surgical approach to petrosal oblique meningioma can not only fully expose and resect the tumor, but also reduce the traction and damage to the brain tissue, especially the brainstem and the important neurovascular around the tumor.
Staging surgical strategies have been proposed based on patient characteristics (older and frail patients), tumor size (i.e., large or large lesions), and tumor growth pattern and direction of invasion (i.e., sphenoid slope meningioma). A staging strategy involves decompression of the brainstem by first entering the sigmoid sinus followed by a frontotemporal craniotomy, particularly in the case of sphenoid-petrosal slope meningioma, which may require oblique process resection and optic nerve decompression. The supratentorial approach can also include orbitozygomatic craniotomy, which provides greater surgical field exposure, a lower and wider surgical perspective, and a shorter surgical approach distance, although this approach is more time-consuming and carries additional risks.
The goal of the first surgery is to decompress the brainstem, which is often the most critical part of the petrosal oblique meningioma. The second surgery is usually performed after the patient has fully recovered and focuses on decompression of the optic and oculomotor nerves and safe resection of the tumor around the ICA. In selected cases (e.g., elderly patients), secondary surgery may not be necessary if the patient does not present with symptoms associated with residual tumour.
In these cases, close follow-up is reasonable. Another staging strategy may be to resect the lower part of the lesion via the petrosal anterior approach followed by the posterior or distal sigmoid approach, particularly if the tumor extends into the inferior slope and foramen magnum.
Finally, a staged surgical approach, including a first-stage combined epidural approach and tumor resection as a second-stage, can be used to reduce risks associated with operative time (i.e., embolization, pressure ulcers) and surgeon fatigue. For giant petrosal slope meningioma, patients with a staged approach may be better tolerated. Another advantage of this staged petrososal symphysis approach is that the lesion is partially cut off first, sometimes leading to partial necrosis and tumor softening, greatly accelerating the time to tumor resection. Therefore, the intradural phase should not be unduly delayed to avoid tumor revascularization and scar tissue formation by collateral revascularization. However, there is little literature on the petrosal-slope meningioma staging approach, and further research is needed to elaborate on the advantages and limitations of this strategy in terms of surgical morbidity and tumor control.
The selection of the appropriate surgical approach should take into account the location of the tumor (posterior fossa, middle fossa or across the middle and posterior fossa), the age of the patient, preoperative neurological impairment (including hearing, facial paralysis, etc.), the extent of surgical resection, and the surgeon's confidence in the surgical technique. Different surgical approaches (even combined approaches) can achieve good results, but none of them have definitively proven to be better. The transpetrosal approach is valuable, especially when solid consistency of the tumor is expected based on preoperative imaging features. If the tumor has a highly homogeneous T2 signal, the lesion is soft, suckable, has a clear arachnoid fissure, and is easy to manage, the classic posterior sigmoid approach should be considered.
Summary of surgical treatment of meningioma in the petrosal oblique area
Microsurgery is the preferred treatment for petrosal meningioma, but it remains a major challenge for neurosurgeons due to the complex location of the tumor. The posterior suboccipital sigmoid approach is a safe and effective surgical approach. According to the preoperative imaging data, tumor characteristics, the patient's own condition and the experience of the surgeon, the individualized treatment plan and the best surgical approach are comprehensively formulated to find the balance between the maximum tumor resection rate and the protection of the patient's neurological function, which will help reduce postoperative complications and neurological damage, and improve the quality of life of patients. If the financial conditions allow, the quality of life requirements are high, and the prognosis is more prognostic, it is recommended that patients seek a doctor with successful surgical experience and a hospital with advanced medical equipment for diagnosis and surgical treatment.