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Introduction

The pineal region is a midline area that includes the pineal gland, the posterior third ventricle, the surrounding cisterns of the quadrigeminal plate and velum interpositum and the adjacent solid tissues of the brainstem, the thalami, and the overlying splenium of the corpus callosum (Ringertz et al. 1954). The pineal gland develops during the second month of gestation from the most caudal portion of the roof of the third ventricle (Langman 1975). The principal cell of the gland is the pineal parenchymal cell. Pineal gland is richly innervated with sympathetic noradrenergic input from a pathway originating from the retina. Upon stimulation the gland produces melatonin, which has regulatory effects on certain hormones such as follicle stimulating hormone and luteinizing hormone. Additionally, the gland plays a central role in maintaining the human circadian rhythm by acting as a neuroendocrine transducer, synchronizing hormonal release with phases of daily light–dark cycle.

Pineal region tumors are derived from cells located in and around the pineal gland. Lesions occurring in this area may be neoplastic or nonneoplastic and are diverse in nature, involving various types of tissues. Most of the tumors are malignant with a propensity to seeding. Combined, these lesions represent less than 1% of all adult intracranial tumors in the United States but the occurrence of pineal masses is higher in Asia with an unexplained higher incidence in Japan (Sano 1998). Pineal region tumors are ten times more common in children than in adults (Abay et al. 1981) and can be found in 3–8% of all pediatric intracranial tumors. Most children are aged 10–20 years at presentation while adults typically present around the age of 30. Jennings et al. (1985) showed that males are 2.2 times more likely to get pineal region tumors than female. This review will discuss the diagnosis, types and optimal neurosurgical treatment of pineal region tumors.

Diagnosis of Pineal Region Tumors

Clinical Presentation

The clinical signs and symptoms of tumors in the pineal region are associated with normal pineal anatomy and specific tumor histology. Sympto-matic hydrocephalus or occulomotor signs are generally the first clinical manifestations of pineal region tumors. Hydrocephalus is triventricular by compression of the aqueduct of Sylvius and can be acute or chronic. Acute obstructive hydrocephalus might be severe enough to result in a downward transtentorial herniation. In slow-growing tumors, chronic hydrocephalus may develop and cause dementia. Hydrocephalus is common at the time of diagnosis. Other symptoms and signs include headaches, visual problems and gait. Occulomotor signs can frequently occur through direct compression of the superior colliculi or the posterior commisure (Sawamura and de Tribolet 2002). Pineal region masses that compromise the superior colliculi may result in Parinaud’s syndrome. This syndrome, described by Parinaud (1883) involves vertical gaze palsy (usually paralysis of the upward gaze), eyelid retraction and convergence/refractory nystagmus; it has become pathognomonic for lesions involving the quadrigeminal plate. Patients can also present with motor impairment such as dysmetria and ataxia due to the compression of cerebellar efferent fibres within the superior cerebellar peduncle. Children with pineal region tumors can also present with endocrine malfunction such as diabetes insipidus and precocious puberty. Pineal apoplexy can rarely occur as a presenting feature of pineal region tumors (Kobayashi et al. 2001). Hemorrhage into a vascular-rich pineal tumor can occur preoperatively and is a well-described postoperative complication.

Neuroimaging

The radiological investigation of choice is magnetic resonance imaging (MRI) which will reveal the tumor and its relations to adjacent anatomical structures. Particular attention has to be given to T1 with gadolinium sequences, high resolution T2 sequences for surrounding vessels (flow-void) and cranial nerves, phlebo-MRI sequences for assessing the 3D anatomy of the deep venous system and its relation with the tumor. A computed tomography (CT) scan is also useful to detect intra-tumoral calcifications or hemorrhage. Even if the different pineal tumor types may have a preferential appearance on imaging, no such characteristics are specific for one or another tumor type and this does not preclude obtaining tissue for histological examination. One exception is the benign pineal cysts, which have a homogenous cyst content with a thin enhancing rim and have no or only mild mass effect on surrounding structures. Except for pineal region meningiomas, angiography is usually not necessary (Sawamura and de Tribolet 2002). The role of magnetic resonance angiography (MRA) to study the patency of the venous system and the arterial supply still remains inferior to digital subtraction angiography (DSA). DSA allows studying details of the vascular anatomy, which is highly complex in the pineal region. It should be mentioned that not visualizing on DSA a vein or a sinus encased in a tumor does not always mean that the structure is occluded and could be safely sacrificed without intraoperative examination.

Tumor Markers

Serum and cerebrospinal fluid (CSF) markers contribute to the diagnosis of pineal tumors and assessment of their malignancy. Embryonic proteins such as beta human chorionic gonadotrophin (βhCG) and alfa-fetoprotein (AFP) are found in germ cell tumors. βhCG is mainly positive in choriocarcinomas, embryonal carcinomas and mixed germ cell tumors. The expression of βHCG is usually low in germinomas which are often positive for placental alkaline phosphate (PLAP) on immunohistochemistry (Sawamura 1998). AFP is expressed by yolk sac tumors (high levels), embryonic carcinomas, immature teratomas and mixed germ cell tumors.

Biopsy

Histological diagnosis is obtained either by stereotactic or endoscopic transventricular biopsy or directly during open surgery. For large pineal tumors a stereotactic biopsy is a safe initial procedure to obtain diagnosis. For tumors extending into the posterior part of the third ventricle, endoscopic transventricular biopsy allows access to tumor tissue as well as third ventriculostomy to treat hydrocephalus.

Types of Pineal Region Tumors

Germ Cell Tumors

Pineal germ cell tumors derive from pluripotential germ cells and affect mainly children and adolescents (90% occurs in the first 25 years of life with a peak between 10 and 14 years). It is more common in males. An accurate histological diagnosis is critical for appropriate treatments and prognosis. It can be said that only germinoma and teratoma are found as pure tumor types.

Germinoma (WHO-2007 Grade 4)

Germinoma is the most common type of pineal region masses, accounting for approximately 65% of germ cell tumors and 40% of all pineal region tumors. About 80% of intracranial germinomas are in the pineal area. Male patients are affected up to 17 times more often than female patients. The peak age of presentation is in the second decade and only a few patients are older than 30 years old at initial presentation. A large number of young children have germinomas associated with precocious puberty (Simson et al. 1968).

Germinoma is a malignant tumor with a biphasic pattern. It is composed of a mixture of large multipotential primitive germ cells with prominently nucleolated large nuclei and fibrovascular septa infiltrated with T-lymphocytes and plasma cells. Because germinomas are unencapsulated, they may invade the adjacent structures of the brain, leading to the fact that at initial presentation the patient would normally already have disseminated disease. Measurement of serum and CSF tumor markers plays a vital role in the initial investigation of patients with germ cell tumors; the expressions of AFP and βhCG are suggestive of malignant germ cells (Allen et al. 1979). In CT scans obtained without contrast, germinomas appear as homogenous masses that either have attenuation equal or slightly higher to that of the gray matter. Similarly, on MRI scans, the signal intensity of germinomas tends to be equal to that of the gray matter on images obtained with both short and long pulse sequences. Therefore, the findings of a non-calcified, homogenous pineal region mass with such signal intensity are strongly suggestive of a germinoma. Although germinomas appear highly enhanced on both CT and MRI scans with contrast material, the enhancement is non-specific and gadolinium-enhanced MRI is recommended to help distinguish metastases from CSF seeding. Germinoma is not a surgical lesion and it is a highly radiosensitive tumor with 85% 10-year survival rate.

Teratoma (Mature: WHO-2007 Grade 1–2; Immature: WHO-2007 Grade 3–4)

Pineal teratoma is the second most common pineal region tumor, contributing to almost 15% of all pineal region masses. Teratomas have a male predilection that ranges from 2:1 to 8:1. They are well-circumscribed benign tumors of multipotential cells that undergo normal organogenesis thereby producing tissues consisting of a mixture of two or more of the embryologic layers of ectoderm, mesoderm and endoderm. Hosoi (1930) first used the term “teratoid” to describe less structured tumors in which derivatives of all three germinal layers could not be distinguished easily. These tumors may contain bone, cartilage and hair. Pineal region teratomas are usually partially or totally encapsulated; however they may also be unencapsulated and locally invasive (Jennings et al. 1985).

Although teratomas do not secrete AFP, the less-differentiated immature teratomas can produce detectable amounts. Immature teratomas contain incompletely differentiated components, resembling fetal tissues and can have primitive neuroectodermal elements like rosettes, arrays and melanotic neuroepithelium. In imaging studies, teratomas tend to be heterogenous, multilocular, ring or ring-enhanced lesions. They may have areas of mixed CSF, lipid and soft-tissue characteristics, as well as calcification. On TI-weighted MRI scans, teratomas may show evidence of fatty or lipid components as areas of signal hyperintensity (Zee et al. 1991). Teratomas may also demonstrate contrast enhancement on both CT and MRI scans. Pineal region teratoma may rupture spontaneously or at surgery, spilling their varied contents and causing chemical meningitis. The third type of teratoma is designated as teratoma with malignant transformation (WHO-2007 4 grade). It usually contains a cancer, mainly rhabdomyosarcoma or undifferentiated sarcoma and less commonly enteric-type adenocarcinoma.

Choriocarcinoma (WHO-2007 Grade 4)

Choriocarcinomas make up less than 5% of all pineal masses and also have a male predilection. They arise from the differentiation of the pluripotential germ cells into the extraembryonic placenta-like tissues. This tumor contains cytotrophoblast (large, mononucleate cells with vesicular nuclei and eosinophilic cytoplasm) and syncytiotrophoblast (giant, βΗCG-positive cells with multiple densely hyperchromatic nuclei arranged in knot-like clusters). Typical findings for these tumors are ectatic vascular channels in stroma and extensive hemorrhage necrosis. Choriocarcinomas secrete large amounts of βhCG and are associated with elevated levels of both CSF and plasma βhCG. Their appearance at CT scans is non-specific and like germinomas they are often represented by areas of high attenuation and show prominent contrast enhancement. Other types of germ cell tumors are yolk sac (endodermal sinus) tumors and embryonal carcinomas. Both tumors are very malignant (WHO-2007 grade 4). Yolk sac tumor contains epithelial cells which form Schiller-Duval bodies (papillary perivascular cuboidal epithelium). Embyonal carcinoma contains large cells lining spaces replicating structure of the early embryo (embryoid bodies).

Pineal Parenchymal Tumors

Pineal parenchymal tumors are the second major group of pineal region tumors, accounting for up to 30% of all tumors in this location. These tumors can occur at any age and should be considered as a true neoplasm of pineal glandular tissue.

Pineocytoma (WHO-2007 Grade 1)

Pineocytoma is a slow-growing tumor usually composed of well-differentiated mature cells that are almost indistinguishable from the normal pineal parenchyma (Preslock 1984). The tumor cells are small and uniform, often forming large pineocytomatous rosettes. It is very rare that large ganglion cells accompanied by small cells with nuclear pleomorphism and hyperchromasia occur. Usually the only feature distinguishing a tumor from a normal tissue is the presence of a mass or an obviously enlarged pineal gland. Pineocytomas constitute approximately 45% of pineal parenchymal tumors. There is no sex predilection but pineocytomas have a tendency to affect young adults. Although pineocytoma is an unencapsulated tumor, it remains locally confined and is unlikely to spread via the CSF system though it may extend into the third ventricle. Because it is a benign tumor, hemorrhage and necrosis are uncommon. Microscopically, pineocytoma is a moderately cellular tumor with large pseudorosettes and abundant cytoplasmic processes. The pseudorosettes (pineocytomatous rosettes), vary in size and shape. Pineal parenchymal cell tumor markers are less well-characterized than their germ cell counterparts. They include melatonin and the S antigen though neither of these proteins has been proven valuable in the diagnosis of pineal parenchymal tumors. On CT scans, pineocytomas are usually globular, demarcated masses measuring less than 3 cm in diameter. They appear hypodense and homogenous, but some show peripheral calcification or occasional cystic changes. Most tumors exhibit homogenous contrast enhancement. On MRI scans, the tumors tend to be low or isodense on T1- and hyperintense on T2-weighted images with strong, homogenous contrast enhancement. It is typical that 5-year survival rate of pineocytoma is very high (86–100%) and there is no relapses following total surgical resection. Tumor with divergent differentiation shares a similar prognosis.

Pineoblastoma (WHO-2007 Grade 4)

Pineoblastoma is a fast-growing, highly malignant primitive embryonic tumor of the pineal gland and composed of dense, patternless sheets of small cells with round to somewhat irregular nuclei and scant cytoplasm. It represents a typical primitive neuroectodermal tumor (PNET). Pineoblastomas comprise approximately 40% of all pineal parenchymal tumors. They originate from immature neoplastic cells of the parenchyma and while they may occur at any age, most present in the first two decades of life with a certain predilection for children. There is no gender preference. Median post-surgical ­survivals vary from 24 to 30 months (Abay et al. 1981); 5-year survival rate is more that 50%. Histologically, pineoblastoma is highly cellular, made up of small cells arranged either in sheets or rosettes. Homer-Wright and Flexner-Wintersteiner rosettes and fleurettes may occur. There are numerous mitoses and intratumoral necrosis. The cells tend to seed within the subarachnoid space and metastasize outside the cerebrum. In contrast to pineocytoma, the CT appearance of pineoblastoma is that of a large, lobulated or poorly-demarcated homogenous mass which is hyperdense after contrast enhancement. On TI-weighted MRI scans, pineoblastomas are hypo- or isodense though they show heterogenous contrast enhancement. Calcification is infrequent. Pineal parenchymal tumors may be inseparable at imaging but may be distinguished from the germ cell tumors because they displace preexisting pineal calcifications, producing an exploded appearance. With the exception of pineocytomas, all other pineal parenchymal tumors are potentially aggressive. Extent of disease at the time of diagnosis, as determined by CSF examination and MRI of the spine, directly affects the survival of patients with pineoblastoma. Not surprisingly, metastases of the pineal tumor within the CNS and vertebral column are the most common cause of death.

Pineal Parenchymal Tumor of Intermediate Differentiation; PPTID (WHO-2007 Grade 2–3)

This tumor type is a pineal parenchymal tumor of intermediate-grade malignancy, affecting all ages and composed of diffuse sheets of large lobules of uniform cells with mild to moderate nuclear atypia and low to moderate level mitotic activity. This tumor group accounts for at least 20% of all pineal parenchymal tumors. The gross appearance of PPTID shows intermediate degrees of development in the club-shaped expansions, dendritic processes, clear vesicles and dense core vesicles between pineocytomas and pineoblastomas (Jouvet et al. 2000). This tumor is diffuse neurocytoma-like tumor with tendency to form nucleus-free perivascular zones. The clinical behavior of this type of tumor is variable and 5-year survival rate is 39–74%. Since Schild et al. (1993) first introduced the term “PPTID”, other subtypes such as mixed pineocytoma/pineoblastoma, malignant pineocytomas and pineoblastomas with lobules have been included in the category.

Others

Other tumors found in the pineal region include metastases, gliomas (fibrillary astrocytoma, ­pilocytic astrocytoma, glioblastoma, oligodendroglioma, ependymoma and choroid plexus papilloma), melanomas, neurocytomas, hemangioblastomas, cavernous hemangiomas, gangliogliomas, symptomatic pineal cysts and meningomas.

Meningioma

Meningiomas in the vicinity of the pineal gland irrespective of their insertion on the falco-tentorial dura can be considered as meningiomas of the pineal region. According to origin, there are two main groups of pineal region meningiomas. The first group has the origin at the velum interpositum without dural attachment and occupies the pineal region and the posterior third ventricle (Konovalov et al. 1996). The second group arises from the falco-tentorial junction and has a dural attachment. These meningiomas also extend into the pineal region and the posterior third ventricle. Pineal region meningiomas are very rare and account for about 0.5–1% of all intracranial meningiomas (Raco et al. 2004; Okami et al. 2001). The first reports on falco-tentorial junction meningiomas were published by Balado (1927). A more detailed description of the falco-tentorial junction meningiomas was presented by Cushing and Eisenhardt in 1938; they described these tumors as a subtype of posterior falx meningiomas.

Pineal region meningiomas can be classified as follows: (a) meningiomas lying freely in the pineal space without dural attachment, (b) meningiomas attached to the tentorium and/or the falx without functional compromise of the venous system and (c) meningiomas with attachment and occlusion of the galenic system (Konovalov et al. 1996). Pineal meningiomas can be further divided according to their insertion and projection on sagittal MRI as anterior/posterior and superior/inferior, and on axial MRI as midline symmetrical and midline asymmetrical (Asari et al. 1994, 1995). Yasargil (1994) has given a very valuable contribution in microsurgical treatment and classification of tentorial meningiomas including pineal region meningiomas.

Neurosurgical Treatment

Microsurgical Anatomy

Pineal region tumors lie deep in the center of the cranium and are surrounded by critical nervous and vascular structures. Therefore, a precise knowledge of the pineal region anatomy is of paramount importance (Matsuno et al. 1988; Ono et al. 1984). The pineal gland is located on the midline and forms an appendix of the caudal end of the diencephalon embracing the pineal recess of the third ventricle. The pineal stem is continuous with the habenular commissure dorsally and the posterior commissure ventrally. The pineal body projects posteriorly in the quadrigeminal cistern where it is flanked by the splenium superiorly and lies on the tectal quadrigeminal plate between the left and right superior colliculi. The pineal gland is mainly vascularized by the medial and lateral posterior choroidal arteries. The tumor of this region is also vascularized by branches of the same arteries. The medial posterior choroidal arteries are branches of the posterior cerebral artery and in addition to the pineal body they supply the superior and inferior colliculi, and the choroidal plexus of the third ventricle. These arteries are displaced laterally by pineal tumors in the cistern and rostrally in the posterior part of the third ventricle together with internal cerebral veins. The lateral posterior choroidal artery supplies the pulvinar and is generally displaced laterally by pineal tumors. During surgical approaches to the pineal gland, the major anatomical obstacle is the Galenic venous system. The great vein of Galen originates a few millimeters behind the pineal gland and runs posterosuperiorly to drain into the straight sinus. There are several surgically significant vessels draining into the great vein. The midline-located superior vermian vein and the precentral cerebral vein run into the dorsal part of the great vein. The internal cerebral veins and the pineal veins join ventrally. Pineal tumors always rostrally elevate the posterior portion of the internal cerebral veins and the veins are occasionally separated from each other. On the lateral aspect of the great vein the medial occipital veins, the third segment of the basal veins of Rosenthal and the posterior mesencephalic veins join. The pineal veins are the draining veins of pineal tumors and drain into either the internal cerebral veins or the vein of Galen. It means that pineal tumors are adherent to the internal cerebral vein and/or the vein of Galen. An injury to the basal veins or the internal cerebral veins is associated with major complications. Also, a transection of a major medial occipital vein may cause homonymous hemianopsia or visual seizures.

Indications for Surgery and Microsurgical Approaches

For benign pineal tumors total surgical resection is a primary goal as surgery alone can be curative (Bruce and Stein 1995). For malignant tumors surgery is only a part of the treatment which consists of adjuvant therapies and therefore radical surgical resection is not an objective (Sawamura and de Tribolet 2002). In all cases focus should be given to reduce post-treatment morbidity. If a newly diagnosed pineal mass is accessible by stereotactic or endoscopic biopsy and the cranial MRI is compatible with a germinoma, a biopsy should first be done in order to avoid an unnecessary craniotomy. If the radiological examination is compatible with an asymptomatic benign pineal cyst and the serum and CSF markers are negative, the patient can be followed up without treatment. The treatment of other pineal tumors requires surgery but the choice of total or subtotal resection will depend on the diagnosis of the presurgical biopsy or the intraoperative frozen section. Benign tumors such as mature teratomas, pineocytomas or meningiomas require total surgical resection when feasible without compromising surrounding neurovascular structures. More aggressive tumors, such as malignant teratomas, pinealoblastomas, embryonal carcinomas, choroicarcinomas and yolk sac tumors require a combination of surgery, radiation therapy and chemotherapy. In any case, the prime goal of surgery should be avoiding surgical morbidity even at the cost of a less radical surgical resection. The choice of approach is a matter of evaluating the anatomical relation of the tumor with the surrounding structures. A steep angle of the straight sinus makes the infratentorial supracerebellar approach (Krause 1926; Stein 1971) difficult as an extensive retraction of the cerebellum is required to visualize and reach the pineal area. Moreover, the lateral exposure of the surgical field is restricted and this renders the resection of larger tumors more complicated.

Evaluating the relationship of the tumor with the quadrigeminal plate is also important. For smaller midline tumors located in the posterior part of the third ventricle and displacing the quadrigeminal plate and the tegmentum of the midbrain caudally, the infratentorial supracerebellar approach is favored as it allows simple, direct and symmetrical exposure of the walls of the third ventricle and internal cerebral veins on both sides. In cases where the tumor lies more caudally and extends into the upper portion of the aqueduct of Sylvius, lying therefore cranially at the tectum, the infratentorial approach is inappropriate as the quadrigeminal plate obstructs the surgical exposure. Finally, the occipital transtentorial approach (Poppen 1966; Jamieson 1971) is preferred in huge tumors with lateral extension in the pulvinar thalami as it gives a better lateral exposure of the walls of the third ventricle (Sawamura and de Tribolet 2002). Giant tumors of the pineal region can be removed by the combined occipital, transtentorial, and supracerellar transsinus approach described by Sekhar and Tzortzidis (1999) (Figs. 7.1 and 7.2).

Fig. 7.1
figure 1

Preoperative CT, large pineal region meningioma

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Fig. 7.2
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Postoperative CT after radical meningioma resection through the combined Sekhar’s approach

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Neurosurgical Operative Modalities

Stereotaxy

Stereotactic procedures are basically diagnostic tools for some pineal tumors such as germinomas or those that are not amenable to resection. Stereotactic biopsy is nowadays easy to use and more advanced with minimal imminent risk of procedure. The vessels of pineal region are frequently displaced from their normal position by the tumor so the complication rate in this kind of biopsy is quite low (1% mortality, 7% morbidity). The diagnostic value of stereotaxy is very high and is more than 90%.

Endoscopy

Hydrocephalus may be controlled with either tumor resection or a CSF diversion procedure. Classical treatment of acute hydrocephalus caused by pineal mass lesion was CSF diversion by ventriculoperitoneal (VP) shunt or external ventricular drainage. Also, surgical resection with the main goal of opening the aqueduct of Sylvius was one of the procedures for tumoral acute hydrocephalus. At present, the treatment of choice for hydrocephalus is the endoscopic third ventriculostomy. This procedure eliminates the necessity of a VP shunt and the risk of peritoneal dissemination of malignant tumor cells. Neuroendoscopy allows an inspection of posterior third ventricle and tumor biopsy at the same procedure with ventriculostomy. Potential risks of endoscopic ventriculostomy include hemorrhage from the basilar artery and posterior thalamoperforators and the tuber cinereum damage with consequent development of diabetes insipidus.

Microsurgery

Microsurgery is recommended in most adult cases and in selected pediatric cases. The five most common surgical approaches to the pineal gland have been described in the twentieth century. Dandy (1921) was the very first neurosurgeon who approached pineal region tumors. He used a parietal parasagittal transcallosal (posterior transcallosal) approach with interhemispheric fissure as an entry point. Following the retraction of parietal lobe and splitting of the splenium, the internal cerebral veins and vein of Galen can be seen. Ten years later, Van Wagenen (1931) describes the transventricular approach. This approach was limited to tumors in the non-dominant hemisphere and patients with eccentric tumor with ventriculomegalia because the entry point was in the cortex of posterior part of superior temporal gyrus and the surgical angle was more lateral compared with other approaches. These two approaches resulted in high morbidity and mortality rates. Microsurgical technique gives some credit to these approaches but they are mainly abandoned nowadays.

Krause (1926) described and successfully used the infratentorial supracerebellar approach. During the 1970s, Stein (1971) developed and popularized this approach by using microsurgical techniques. The occipital transtentorial approach was pioneered by Foerster in 1928 and described by Poppen (1966). This method required extensive lifting of the occipital lobe after CSF drainage via a ventricular catheter. It was modified by Jamieson (1971) who preferred to mobilize the occipital lobe laterally rather than proceeding below it. Shekar described the combined occipital, transtentorial, supracerebellar, transsinus approach which combined the advantages of the supracerebellar infratentorial and occipital transtentorial approaches (Sekhar and Tzortzidis 1999). The occipital transtentorial approach, the infratentorial supracerebellar approach and combined Shekar’s approach are nowadays accepted as the main standard accesses to the pineal region. Regardless of any chosen approach, an en-bloc tumor removal is rarely possible and as such piece-meal intracapsular decompression is an important step in preparing good cleavage planes especially the nearby quadrigeminal plate.

Occipital Transtentorial Approach

The occipital transtentorial approach can be performed with the patient placed in a prone, park-bench or sitting position. Currently, the park-bench position is preferred by majority of neurosurgeons. In this position the head is flexed and rotated, allowing the occipital lobe to fall aside with the help of gravity and the whole procedure can be done without placing any retractors on the brain. Approaching from the right side is more common although tumor extension and the torcular characteristic should always be taken into consideration before any decision is made. The typical skin incision is in an inverted U-shape manner starting 1 cm on the left of the occipital protuberance, extending upwards, turning right and finally downwards to reach the right mastoid. Two midline burr holes are performed, one over the torcular and another 6 cm apart and upward. A standard occipital craniotomy exposing 2 cm of the transverse sinus, the torcular and 6 cm of the superior sagittal sinus is completed. The inverted C-shape dural opening is made with the base on the superior sagittal sinus. After exposing the occipital lobe, the ipsilateral occipital horn is taped to release CSF and gain the space. The falx, tentorium and tumor can be visualized. The entry point is the unilateral interhemispheric space between the falx and the medial part of occipital lobe. The large occipital bridging veins are usually not present, but if veins are encountered, they should be preserved. The tentorium is incised from posterior to anterior and begins 2 cm anterior to the torcular and just lateral to the straight sinus and proceeds parallel to the sinus until the falco-tentorial junction is reached.

In some pineal region meningiomas, the straight sinus and the falco-tentorial junction are encased by the tumor. The tentorial incision is then made laterally to the tumor and proceeds again posteroanteriorly to the free tentorial edge interrupting the vascular supply on the way. The venous channels of the tentorium sometimes cause significant bleeding which can be controlled by bipolar coagulation. The surgeon can see the superior cerebellar artery and the cranial nerve IV running around the brainstem after reflecting the incised tentorium laterally. If the vein of Galen and the internal cerebral veins are extensively invaded by tumor, the residual tumor tissue around these veins can be left in place and treated by radiosurgery.

For extrinsic tumors freely lying in the pineal region, the technique is essentially the same as for pineal gland intrinsic neoplasms. After the tentorium has been divided, the dura reflected, one stay suture can be placed on the dura to increase visibility. When the thick arachnoid cistern of the great vein of Galen becomes visible, a gentle retraction of the occipital lobe is made, avoiding an over-compression of the calcarine sulcus and an avulsion of veins, which could cause hemianopsia. The splenium of corpus callosum comes into sight. An extensive dissection of the arachnoidea helps to expose the ipsilateral medial occipital vein, the pericallosal veins, the precentral cerebellar vein and the tributary veins. The superior vermian vein and the precentral vein can be coagulated and sectioned. The dissection proceeds towards the right ambient cistern to identify the P3 segment of posterior cerebral artery, the cranial nerve IV emerging below the inferior colliculus, and the third segment of the basal vein.

The quadrigeminal plate is a crucial nervous structure, which must be intraoperatively located before deep microsurgical manipulation for tumor resection is started. This plate is situated inferiorly in the operative filed. If the tumor is posterior, the quadrigeminal plate will be covered by it, whereas if it is more anterior, the quadrigeminal plate will be pushed backwards and downwards making it identifiable just after opening of the cistern. The dissection can proceed on both sides laterally to separate the tumor from the pulvinar thalami. During this dissection one should be aware of Rosenthal’s veins, which delineate the superior and lateral margins of operative view. Final dissection involves entering of the third ventricle and removing the superior part of the tumor adherent to the velum interpositum, the internal cerebral veins, and the anterior aspect of the vein of Galen. The main entry to the roof of the third ventricle is between the vein of Galen and the splenium. It can be done easily after cutting the posterior pericallosal veins which allows the splenium to be detached from the great vein. The bilateral internal cerebral veins will appear in the velum interpositum cistern. A dissection of the cistern will expose the anterior choroïdal artery in the third ventricle as well as the ventral part of tumor.

Another entry is below the vein of Galen and the internal cerebral vein. It is better to leave residual tumor behind rather than to damage the internal cerebral veins. If bleeding occurs, hemostasis should be achieved by packing surgicel without coagulation. After complete removal of the tumor, the surgeon will have a good view into the third ventricle, which can be extended to the foramina of Monroe and the lamina terminalis. Finally, care should be taken to “unplug” the aqueduct of Sylvius. When this is properly achieved, no postoperative drainage of CSF will be necessary.

Infratentorial Supracerebellar

The infratentorial supracerebellar approach is a gold standard in treating pineal gland tumors. Also, this approach is very useful for the resection of pineal region meningioma without dural attachment and which originates from the velum. The patient is always placed in a sitting position in which the cerebellum can fall inferiorly (Figs. 7.3 and 7.4). The preventative measures against air embolism including a central venous line, oesophageal Doppler and end-tidal CO2 monitoring are mandatory. A vertical midline skin incision extends from 2 cm above the external occipital protuberance down to the level of the C2 spinal process, or lower when a patient has a thick neck. A high-speed drill (instead of a craniotome) is used to make two burr holes just beside the torcular on each side of the midline and to crosscut the sinuses. The craniotomy should not involve the foramen magnum. After craniotomy, any venous leaks must be sealed due to avoid air embolism. The dura is incised in a dull “U” shaped fashion, and the dural flap is suspended upwards. The posterior bridging veins between the cerebellum and the tentorium are coagulated and transected. One retractor is then placed to pull up the tentorium. This creates a trajectory that leads along the straight sinus to the great vein of Galen. Pursuing the dissection of the arachnoid plane on both sides, a downward traction of the upper part of cerebellum exposes the deeply situated pineal area. A further retraction of the vermis can be executed after sectioning of the superior vermian and precentral veins.

Fig. 7.3
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The sitting position

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Fig. 7.4
figure 4

Infratentorial supracerebellar approach

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This approach offers a view through the midline that can provide an easy orientation and a symmetrical exposure of both walls and the roof of the third ventricle. Under direct observation, tight tumor adhesion can be freed from the internal cerebral veins or the great veins. The opening of the third ventricle can be closed by fibrin sealant to prevent an excessive CSF leakage. A watertight dural closure should be done with a running suture only after compression of the jugular veins (by anesthesiologist) and sealing of all venous leaks are completed.

The Combined Occipital, Transtentorial, Supracerebellar, Transsinus Approach

Shekar has described a combined supratentorial-infratentorial approach for large pineal region tumor especially for giant falco-tentorial meningiomas. This approach provides a wide view of the pineal region and all venous complexes. The patient is placed in a semiprone position and a suboccipital-occipital craniotomy is performed in three pieces. The infratentorial and supratentorial dura, the superior sagittal and transverse sinuses as well as the torcular are exposed. The cisterna magna is opened to relax the cerebellum and gain the operative space. A needle (20-gauge) attached to a manometer is placed into the transverse sinus just lateral to the torcular. The sinus is occluded for 5 min lateral to the needle. If no brain swelling is observed and venous pressure does not rise more than 5 mmHg, the transverse sinus can be divided on the non-dominant side. The tentorium is divided parasagittally toward the tentorial notch. The occipital lobe and the cerebellum as well as the tentorium and the falx cerebri can then be easily retracted to reach the pineal region tumor. The transverse sinus can sometimes be resutured or even reconstructed by a short vein graft. However, in majority of cases it is safe to leave the sinus permanently occluded.

The advantages of this approach are the wide exposure of the tumor and the deep veins that can restrict the exposure through the occipital transtentorial approach, the decreased retraction of the occipital lobe and the cerebellum, and finally the better control of the posterior third ventricle and the medullary velum. However, there are some concerns about dividing the transverse sinus in a situation where the venous return can easily decompensate.

In conclusion, contemporary management of pineal region tumors requires a multidisciplinary cooperation where surgery represents only one aspect of the treatment plan. However, with the exception of germinoma where only a biopsy is needed, the role of the surgeons still remains prominent as resection of pineal tumors requires high technical skill and experience as well as precise clinical judgment. The infratentorial supracerebellar approach and the occipital transtentorial approach when used appropriately allow access to nearly every type of pineal region neoplasm.