Abstract
Surgical intervention remains a mainstay of effective treatment for both benign and malignant pineal lesions and a variety of surgical approaches have been designed to treat tumors arising in this anatomically complex region. Advances in microsurgical techniques have enabled surgeons to achieve safe and complete resections of the majority of lesions that arise within the pineal region with excellent long term prognoses for patients with benign tumors and a large percentage of patients with malignant tumors. While morbidity is low, and mortality rates significantly improved from the early days of pineal surgery, a deep understanding of the anatomical associations of the region in the context of the particular approach and position chosen is critical to successful pineal region surgery. Special attention should be given to preservation of critical deep neurovascular structures, and postoperative surveillance for catastrophic hemorrhage or significant cerebellar swelling is critical.
Keywords
supracerebellar infratentorial, occipital transtentorial, pineal, pineal tumor, interhemispheric transcallosal, brain tumor, complications, hydrocephalus
Highlights
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Gross total resection decreases the risk for postoperative hemorrhage and should be pursued in the absence of contraindications.
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Pupil abnormalities, difficulty focusing or accommodating, impaired extraocular movements, and limited upward gaze are postoperative deficits that are frequently encountered after surgery for pineal lesions. These deficits are typically transient.
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Great care should always be taken to avoid damage to the deep cerebral veins.
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Acute cerebellar swelling from venous infarct is an unpredictable and potentially deadly complication of supracerebellar infratentorial approaches to the pineal region.
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In the setting of acute postoperative cerebellar swelling, rapid decompression and/or removal of hematoma and infarcted cerebellum may be the only way to efficiently treat and save a patient.
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The use of fixed retractors should be minimized whenever possible.
Background
The pineal region gives rise to a heterogeneous group of neoplastic and nonneoplastic lesions. Neurosurgical intervention—ranging from biopsy to complete resection—remains vital to the management of pineal region tumors. In particular, aggressive surgical resection facilitates accurate diagnosis, the reduction of mass effect, and the management of associated symptoms such as hydrocephalus. Management strategies centered around aggressive resection, in conjunction with advances in microsurgical techniques, neuroanesthesia, postoperative critical care, and chemotherapy/radiotherapy, have resulted in excellent long-term outcomes for patients with benign pathologies and in improved long-term prognoses for patients with malignant tumors.
The pineal region is an anatomically complex and surgically intimidating environment. Located deep and centrally within the posterior incisural space, the pineal gland is in close proximity to the cerebellum, collicular plate, bilateral pulvinars, and critical deep cerebrovascular structures. As a result, the complete, safe resection of pineal lesions remains among the most challenging of neurosurgical procedures.
Fortunately, a variety of adaptable surgical approaches to the pineal region have been developed. Each approach takes into consideration the relevant anatomic relationships of the region, the location of the blood supply to the lesion, and the extent of resection goals of the surgery. Furthermore, each approach offers unique mitigation of the risks to critical adjacent structures. Although the availability of a variety of surgical approaches, in combination with advances in microsurgical techniques, has made the surgical management of pineal lesions safer, surgery for pineal region tumors remains complex and fraught with potential pitfalls, with permanent morbidity ranging from 1.0% to 20.0%, and reported mortality rates ranging from 0.7% to 4.0% ( Table 24.1 ) in large series.
| Author | Year | n | Approach | Severe/Permanent Morbidity | % | Mortality (%) |
|---|---|---|---|---|---|---|
| Bruce and Stein | 1995 | 160 | SCIT | EOM dysfunction | 16.0 | 4.0 |
| IHTC | Hemorrhage | 6.0 | ||||
| OTT | Altered mental status | 5.0 | ||||
| Ataxia | 3.0 | |||||
| Hemianopsia | 1.0 | |||||
| Paraparesis/quadriparesis | 1.0 | |||||
| Konovalov and Pitskhelauri | 2003 | 287 | OTT | EOM dysfunction | 31.0 | 1.8 |
| SCIT | Hemorrhage | 11.0 | ||||
| Subchoroidal | Meningoencephalitis | 6.0 | ||||
| Fourth ventricle | Hemianopsia | 4.0 | ||||
| Hernesniemi et al . | 2008 | 119 | SCIT | Ataxia | 1.7 | 0 |
| OTT | Vision changes | 1.6 | ||||
| Hemiparesis | 0.8 | |||||
| Qi et al. | 2014 | 143 | OTT | Hemorrhage | 3.5 | 0.7 |
| Hemianopsia | 3.5 | |||||
| Parinaud syndrome | 2.1 | |||||
| Hemiparesis | 2.1 | |||||
| Altered mental status | 1.4 |
Anatomic Insights
Hemorrhage
Postoperative hemorrhage into an incompletely resected tumor ( Fig. 24.1 ) is the most serious complication after pineal surgery. Risk of postoperative hemorrhage is closely associated with the nature of the tumor and its malignant potential, with a higher incidence after subtotal resections of soft, vascular malignant pineal parenchymal tumors. Notably, the risk of postoperative hemorrhage remains over several postoperative days, and careful surveillance with frequent neurologic assessment is critical. Whereas small hemorrhages without significant mass effect can usually be managed conservatively, large hemorrhages may require immediate evacuation and are associated with a greater risk of mortality. Importantly, any hemorrhage can result in obstructive hydrocephalus requiring urgent cerebrospinal fluid (CSF) diversion.
Hydrocephalus
Pineal lesions are commonly diagnosed in the setting of progressive symptomatic hydrocephalus, and the majority of patients require preoperative CSF diversion. Accepted methods of preoperative CSF diversion include temporary solutions such as external ventricular drain (EVD) insertion, or permanent solutions such as ventriculoperitoneal shunt (VPS) insertion or endoscopic third ventriculostomy (ETV). Regardless of the surgeon’s choice of CSF diversion, postoperative air, blood, or operative debris after resection of a pineal tumor can result in blockage of a preexisting VPS or EVD catheter, or ventriculostomy. This is particularly worrisome because acute hydrocephalus can result in rapid neurologic deterioration and major morbidity. In cases of acute hydrocephalus after pineal surgery in patients with previous CSF diversion, urgent replacement of an EVD, revision of VPS, or exploration of the previous ventriculostomy should be considered.
In asymptomatic or nonhydrocephalus patients, the surgical resection of a pineal lesion communicates the third ventricle with the quadrigeminal cistern and may preclude the need for permanent CSF diversion. As a result, these patients often do not undergo preoperative definitive management of their hydrocephalus in hopes that resection of the pineal region tumor will prevent the future development of hydrocephalus. However, the presence of intraoperative or postoperative hemorrhage, air, or debris into the ventricular system after pineal region tumor resection can similarly result in the blockage of natural CSF egress with the subsequent development of acute hydrocephalus. Postoperative surveillance is again critical because this group of patients may similarly require urgent temporary or permanent CSF diversion.
Third Ventricle, Brainstem, and Cerebellum
Pineal lesions may cause mass effect on the posterior third ventricle anteriorly, the quadrigeminal plate inferiorly, and the cerebellum posteriorly. Dissection of lesions off the quadrigeminal plate commonly results in pupil abnormalities, difficulty with focusing or accommodating, impaired extraocular movements, and limited upward gaze. Permanent impairment is rare. However, normal function may take several months to return, or sometimes as long as a year, and patients should be counseled accordingly. A residual mild limitation of upgaze is common but bears little clinical significance. Although the fourth cranial nerve originates on the posterior midbrain, it generally arises caudal to the tumor origin and is rarely identified or injured during resection.
Impaired consciousness can result from manipulation of brain adjacent to the third ventricle. This impairment is typically transient with return to normal mental status occurring usually over several days after surgery. Significant manipulation of the brainstem can also result in cognitive impairment or, rarely, akinetic mutism.
Cerebellar manipulation frequently results in mild ataxia postoperatively that resolves over several days. Of greater clinical significance, cerebellar venous infarction with acute cerebellar swelling is a rare and dangerous complication that may cause a rapid clinical decline with high risk of morbidity and mortality due to associated obstructive hydrocephalus or mass effect on the brainstem. This is further discussed below.
Arterial
The pineal gland receives its blood supply from the medial and lateral posterior choroidal branches of the posterior cerebral artery (PCA), and through anastomoses between the pericallosal arteries, the PCA, and the superior cerebellar artery (SCA). Both the PCA and SCA and their branches course through the posterior incisural space. The PCA bifurcates into the calcarine and parieto-occipital arteries within the posterior incisural space before crossing above the free edge of the tentorium. Typically, branches of the PCA supply structures above the level of the superior colliculus, whereas branches of the SCA supply structures at or below the inferior colliculus. Damage to the trunks of the PCA or the SCA is rare during surgery for pineal lesions given their caudal location in relation to the tumor. The main arterial risk is to the small perforating branches of the PCA, the SCA, and the choroidal arteries that enter the borders of the quadrigeminal cistern and supply the colliculi, thalamus, and pineal gland itself. In general, choroidal vessels along the tumor capsule are dissected if amenable. However, their preservation is not mandatory if they are simply supplying the choroid plexus.
Venous
The pineal gland is located just anterior to the vein of Galen and is surrounded by many of its large tributaries, including the internal cerebral and basal veins of Rosenthal. Additional nearby veins include the anterior calcarine vein, the posterior pericallosal vein, the collicular veins, and the pineal veins. The risk of significant venous injury varies with approach. Supratentorial approaches require the surgeon to work carefully around the convergence of the deep cerebral veins, where injury can result in venous infarction of the thalamus, hypothalamus, or midbrain. Infratentorial approaches are more suitable for protecting the deep cerebral veins, because the surgeon accesses the pineal gland from a space beneath the bilateral basal veins of Rosenthal.
Two significant venous convergences must still be carefully navigated with infratentorial approaches. Superior cerebellar hemispheric veins and inferior cerebellar hemispheric veins frequently join to form bridging veins that drain large parts of the cerebellum into the tentorial sinuses. Whereas lateral bridging veins may be avoided with midline or off-midline approaches, midline veins may need to be retracted or sacrificed to reach the quadrigeminal cistern and the pineal gland. There is considerable variability in the site of these veins, and available preoperative imaging should be thoroughly reviewed before planning a particular surgical approach.
Once the arachnoid of the quadrigeminal cistern is dissected during infratentorial approaches, a second significant venous convergence that blocks access to the pineal region is identified. The superior vermian vein and the precentral cerebellar vein approach the vein of Galen inferiorly in the midline. The superior vermian vein and the precentral cerebellar vein may need to be retracted or are often sacrificed with midline supracerebellar infratentorial (SCIT) approaches to the pineal region. Importantly, when the precentral cerebellar vein must be sacrificed, it should be divided peripherally to avoid back propagation of thrombosis into the vein of Galen and occlusion of critical collateral circulation, because rare but devastating injuries have been reported.
In general, sacrificing the superior vermian, precentral cerebellar, and hemispheric or vermian bridging veins has been considered relatively safe as long as the collateral circulation of each vein is preserved. Unfortunately, sacrificing even a limited number of these veins may cause acute or subacute postoperative cerebellar swelling due to venous infarction and/or hemorrhagic conversion ( Fig. 24.2 ). This serious complication may rapidly progress to a life-threatening condition because of mass effect on the brainstem or direct venous infarct of the brainstem. This rare and unpredictable complication is thought to be the result of venous insufficiency in a small subset of patients who cannot tolerate the sacrifice of bridging veins in the cerebellum.
