Initial Symptoms

Pineal region tumors are generally manifested in one of three ways^21,56: (1) symptoms of increased intracranial pressure from obstructive hydrocephalus, (2) direct brainstem and cerebellar compression, or (3) endocrine dysfunction.

The most common initial symptom is headache, which is associated with obstructive hydrocephalus secondary to compression of the aqueduct of Sylvius. Further progression of hydrocephalus can lead to nausea, vomiting, obtundation, cognitive impairment, papilledema, and ataxia. In rare cases, symptoms can develop abruptly in association with pineal apoplexy from hemorrhage in a pineal tumor.^57–60

Direct compression of the midbrain, particularly at the level of the superior colliculus, can cause disorders of extraocular movement, classically known as Parinaud’s syndrome.^61,62 This syndrome can consist of paralysis of upgaze, convergence or retraction nystagmus, and light-near pupillary dissociation. The sylvian aqueduct syndrome, which consists of paralysis of downgaze or horizontal gaze from further midbrain compression, can be superimposed on Parinaud’s syndrome.⁶³ Dorsal midbrain compression or infiltration can lead to lid retraction (Collier’s sign) or ptosis. Less commonly, fourth nerve palsies with diplopia and head tilt may occur. Although eye signs can be due to either hydrocephalus or direct brain compression, symptoms from hydrocephalus generally recede after a cerebrospinal fluid (CSF) diversion procedure. Interference with the cerebellar efferent pathways of the superior cerebellar peduncles can cause ataxia and dysmetria. Rare cases of hearing dysfunction have been reported, probably caused by a disturbance in structures associated with the inferior colliculi.^64,65

Endocrine dysfunction is rarely encountered but usually arises from the secondary effects of hydrocephalus or from spread of tumor to the hypothalamic region.⁶⁶ Diabetes insipidus can occur with a germinoma spreading along the floor of the third ventricle. Such symptoms may develop early in the disease process, even before the tumor is radiographically apparent. Precocious puberty has been linked historically with pineal masses; however, documented cases are rare.^48,66,67 This syndrome is actually precocious pseudopuberty because the hypothalamic-gonadal axis is not mature, and it is therefore limited to boys whose choriocarcinoma or germinoma contains syncytiotrophoblastic cells producing ectopic secretion of β-human chorionic gonadotropin.^66,68

Diagnosis

Magnetic resonance imaging (MRI) with gadolinium enhancement is the principal diagnostic test for pineal tumors.^49,69–71 MRI reveals the degree of hydrocephalus and allows evaluation of tumor size, vascularity, homogeneity, and anatomic relationships with surrounding structures. In planning the operative approach, knowledge of the relevant anatomic relationships is useful, including the position of the tumor within the third ventricle, the amount of lateral and supratentorial extension, and the degree of brainstem involvement. The extent of tumor invasiveness can be estimated from the margination and irregularities of the tumor border; however, the true degree of tumor encapsulation can be defined only at surgery.⁴²

Pineal tumors generally displace the vessels of the deep venous system superiorly along the dorsal periphery of the tumor. This is an important point when planning surgical approaches because most tumors can be separated from the surrounding veins and midbrain (Fig. 125-3).⁴² Notable exceptions are meningiomas arising from the velum interpositum and epidermoid or other tumors originating in the corpus callosum. These tumors displace the deep venous system ventrally and inferiorly, thereby providing a diagnostic clue on MRI. The position of the tumor relative to the deep venous system is important because it may influence the choice between an infratentorial and a supratentorial approach. Although the location of the deep venous system may be conspicuous on MRI, magnetic resonance venography may be desirable to better delineate it.

FIGURE 125-3 Magnetic resonance images showing the variability of the deep venous system in relation to pineal region tumors. A, The deep venous system is located superior and dorsal to the tumor. This is the most common configuration and is conducive to an infratentorial-supracerebellar approach. B, The deep venous system is located inferior and ventral to this epidermoid tumor and is conducive to a supratentorial approach.

Despite advances in high-resolution MRI, tumor histology cannot be reliably predicted on the basis of imaging features alone.^{21,69,70,72,73} Computed tomography can complement MRI by providing details of calcification, blood-brain barrier breakdown, and the degree of vascularity.⁷⁴ Angiography is not necessary unless a vascular anomaly is suspected.

Management of Hydrocephalus

Most patients are initially seen with obstructive hydrocephalus, which can be managed in several ways. Symptomatic patients are best managed initially with a stereotactic-guided endoscopic third ventriculostomy to allow gradual reduction of intracranial pressure and resolution of symptoms before tumor resection.⁹¹ This method is preferable to ventriculoperitoneal shunting because it eliminates potential complications such as infection, overshunting, and peritoneal seeding of malignant cells. Mildly symptomatic patients in whom gross total resection is anticipated at surgery can be managed with a ventricular drain placed at the time of surgical resection.^25,92 The drain can be removed or converted to a shunt in the postoperative period as circumstances dictate.

Tissue Diagnosis: Biopsy versus Open Resection

Given the diverse pathology that can occur in the pineal region, a histologic diagnosis is necessary to optimize management decisions.^{42,44,92–95} An individual tumor’s histology strongly influences the choice of postoperative adjuvant therapy, need for metastatic work-up, estimation of prognosis, and planning of long-term follow-up. Although CSF cytology and radiographic examination provide insight into the histologic diagnosis, they are not sufficiently sensitive to supplant a tissue diagnosis.^72,96–101 CSF cytology occasionally reveals malignant cells but is rarely diagnostic. The only time that a tissue diagnosis is unnecessary is in the presence of malignant germ cell markers; in these cases, chemotherapy and radiation therapy should proceed without a biopsy.^92,100,102

Tissue diagnosis can be achieved by either stereotactic biopsy or an open procedure. This decision is influenced by the clinical features of the patient, radiographic features of the tumor, and the surgeon’s degree of experience with the procedures. Inflexible or dogmatic dedication to either procedure is not appropriate. In general, patients with known primary systemic tumors, multiple lesions, or medical conditions that make open resection dangerous are good candidates for stereotactic biopsy.^49,92 Radiographic evidence of brainstem invasion might make stereotactic biopsy an attractive choice; however, the degree of invasion seen radiographically can be misleading and may not reflect a dissectible tumor capsule at surgery. The advantage of open resection is the ability to obtain larger amounts of tissue and more extensive tissue sampling. This is particularly important for pineal region lesions in general and germ cell tumors in particular because heterogeneity and mixed cell populations are common. This diversity makes it difficult for neuropathologists to appreciate the subtleties of histologic diagnosis when only small specimens are available (Fig. 125-4; Table 125-2).^{25,92,103–105}

FIGURE 125-4 Sagittal magnetic resonance image (A) and gross pathology (B) from a patient with a mixed germ cell tumor demonstrating the heterogeneity of the tumor. Such heterogeneity can lead to misdiagnosis if tissue sampling is limited.

TABLE 125-2 Pure versus Mixed Germ Cell Tumors at the New York Neurological Institute (1978-2000)

EST, endodermal sinus tumor.

Additionally, a clinical advantage is gained when the tumor burden is reduced with an open procedure. For the third of tumors that are benign, resection is usually complete and curative, thus making it the clear procedure of choice (Table 125-3).^42,92,106 The advantages of tumor debulking are less apparent with malignant tumors; however, anecdotal evidence favors more radical resection, when possible, to improve the response to adjuvant therapy.^{34,92,106–108} Additionally, for certain patients with mild hydrocephalus whose tumors can be completely resected, shunting can be avoided.^25,92

Stereotactic biopsy offers the advantages of relative ease of performance and reduced complications when compared with an open procedure.^{24,29,109–111} Usually, only local anesthesia is necessary. However, stereotactic biopsy carries a risk for hemorrhage from several mechanisms, including bleeding in highly vascular tumors, damage to the deep venous system, and bleeding into the ventricle, where tissue turgor is insufficient to tamponade minor bleeding.^{25,92,103,110,112} These risks notwithstanding, several large series have validated the relative safety of stereotactic biopsy for these tumors despite their rather hazardous location.^24,109 Of minor concern but worth mentioning is a report of metastatic seeding along the biopsy tract after biopsy of a pineoblastoma.¹¹³

Stereotactic Procedures

The relative technical ease of performing stereotactic biopsy procedures should be viewed cautiously with regard to lesions in the pineal region. There are numerous pitfalls that must be avoided to complete a successful biopsy. An appreciation of the complex anatomy at the biopsy site and through the potential trajectory is critical.

Most target-centered stereotactic frame systems are adequate for biopsy. Computed tomography is sufficient to provide accurate targeting information and to track the trajectory in three dimensions. MRI provides more sensitive soft tissue visualization, and current software has minimized any spatial inaccuracy. Volumetric treatment planning should be used to identify the trajectory in all the axial, sagittal, and coronal planes. Two possible approaches are favored for stereotactic surgical trajectories.^24,29,56,114 The most common is through a precoronal entry point, with the tumor being reached through an anterolaterosuperior approach that avoids the interior surface of the lateral ventricle and comes inferior and lateral to the internal cerebral veins to reduce the risk for bleeding. The alternative approach is through a posterolaterosuperior approach near the parieto-occipital junction, which can be useful for tumors that extend laterally or superiorly.

Serial biopsies are desirable whenever possible; however, this is often prohibited by the small size of the tumors commonly encountered.^24,109 The side-cutting cannula type of biopsy needle is preferred over a cup forceps instrument, which can tear a blood vessel. If bleeding is encountered, continuous suction and irrigation for up to 15 minutes may be necessary. When bleeding is suspected, an immediate scan should be obtained to assess for intraventricular blood and the degree of hydrocephalus to determine the need for ventricular drainage.

Endoscopic Biopsy

Endoscopic biopsy of pineal tumors through the ventricles has been reported as an alternative method for securing a tissue diagnosis.^115–119 In addition to sampling error, a major drawback of this procedure is that the tumor is biopsied along its ventricular surface, where there is no tissue turgor to tamponade the bleeding. Even minor bleeding within the CSF space can be difficult to manage, a problem that is compounded by the highly vascular properties of many pineal tumors. Typically, this procedure is combined with a ventriculostomy. However, even with flexible endoscopes, it is difficult to perform a biopsy simultaneously with a ventriculostomy because the trajectory required is different for each procedure. The rigid endoscope is not easily maneuverable without risk of damage to the fornix and the septal and thalamostriate veins at the foramen of Monro. A suitable entry point through the forehead might allow the use of a rigid scope, but this offers no advantage over a simple stereotactic biopsy. More typically, endoscopes have been used to aspirate pineal cysts; however, the benefits of this approach are equivocal.

Operative Procedures

Several variations on approaches to the pineal region exist, but essentially they are categorized as supratentorial or infratentorial.^36,42,92 Supratentorial approaches include transcallosal interhemispheric, occipital transtentorial, and the rarely used transcortical transventricular.^13,34,92,120 The infratentorial approach is through a natural corridor created between the tentorium and the cerebellum.^31,121 The choice of approach depends on the surgeon’s experience and comfort with the specific technique. Many of these approaches are interchangeable, although there are several caveats. Large tumors that extend supratentorially or laterally to the trigone of the lateral ventricle generally benefit from a supratentorial approach.⁹² Supratentorial approaches afford greater exposure than infratentorial approaches do, but they have the disadvantage of forcing the surgeon to work around the convergence of the vein of Galen and internal cerebral veins, where they interfere with tumor removal.

The location of most pineal tumors infratentorially and in the midline gives the infratentorial supracerebellar approach several natural advantages.^92,122 It is performed with the patient in the sitting position, whereby gravity allows the cerebellum and the tumor to drop downward. The tumor can then be dissected more easily off the deep venous system and velum interpositum, which is often the most technically difficult portion of tumor dissection. Besides the obvious anatomic advantage of using a midline trajectory, the deep venous system lies dorsal to the mass, thus making it more avoidable through most of the tumor dissection. The approach is less favorable if the tumor has a significant supratentorial or lateral extension, although with appropriate extra-long instruments, even tumors extending anteriorly into the third ventricle can be removed.

Sitting Position

The sitting position is usually preferred for the infratentorial supracerebellar approach (see Fig. 125-5A).^92,122 Gravity works in the surgeon’s favor by reducing pooling of blood in the operative field and by facilitating dissection of the tumor from the deep venous system. The risks for air embolism, pneumocephalus, or subdural hematoma associated with cortical collapse can be anticipated and managed with proper precautions.^92,123 Doppler monitoring helps detect small amounts of air entering the venous system during the operative procedure. A central venous catheter can be used to remove entrapped air if necessary.

The patient is brought to the sitting position by manipulating the operative table from the supine position while an assistant stabilizes the patient’s head. A reverse table capable of being lowered close to the floor is desirable. The head is flexed so that the tentorium is approximately parallel to the floor. The patient’s legs should be elevated to assist venous return. A three-point vise type of head holder keeps the head immobile. At least two fingerbreadths of space is needed between the patient’s chin and sternum to avoid compromising the airway and venous return. A Greenberg self-retaining retractor or similar system is arranged to frame the operative field to assist in cerebellar retraction and serve as a holder for cottonoids.

Lateral Position

The lateral decubitus position with the dependent, nondominant right hemisphere down is generally used.¹²⁴ The head is raised approximately 30 degrees above the horizontal in the midsagittal plane, especially for the transcallosal approach. For the occipital transtentorial approach, the head should be positioned with the patient’s nose rotated 30 degrees toward the floor.

A more desirable variation of this approach is the three-quarter prone position (Fig. 125-5B).¹²⁵ The legs are flexed with a pillow between them, and the patient is strapped down so that the table can be rotated during the procedure to improve exposure when appropriate. The three-quarter prone position is essentially an extension of the lateral position, except that the head is at an oblique 45-degree angle with the nondominant hemisphere dependent. This is suitable for more posterior approaches, such as the occipital transtentorial as opposed to the transcallosal approach. The nondominant hemisphere is easily retracted with the help of gravity. Surgeon fatigue is reduced because the surgeon’s hands are on a horizontal plane and are not extended to the degree they are with patients in the sitting position. The three-quarter prone position can be cumbersome and requires placing an axillary roll under the patient’s right axilla with the right arm supported in a sling-like fashion beneath the patient. A supporting roll is placed under the left thorax, and a three-point head-pin vise holder is used to support the head in a slightly extended and rotated position to the left at a 45-degree oblique angle. The patient is securely strapped, and the legs and feet are elevated to facilitate venous return.

Prone Position

The prone position is simple and safe for supratentorial approaches (Fig. 125-5C).^92,120 It is generally comfortable for the surgeon, although the operative field is considerably raised, which makes it difficult for the surgeon to be seated. This position is useful when two surgeons work together through an operative microscope that has a bridge to allow simultaneous binocular vision. The steep angle of the tentorium, however, makes the prone position impractical for the infratentorial approach. This position is often useful in the pediatric population. To facilitate its use, the position of the head can be rotated 15 degrees away from the craniotomy side in a variation known as the Concorde position (Fig. 125-5D).¹²⁶

Infratentorial Supracerebellar Approach

The infratentorial supracerebellar approach was first described by Krause at the beginning of the 20th century (Fig. 125-6, Video 125-1).⁵ The technique was lost for many years because of limitations in microsurgical technique until its rediscovery in 1971 by Stein.³¹

FIGURE 125-6 Infratentorial supracerebellar approach. A,

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