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Pineal Region Masses—Imaging Findings and Surgical Approaches
Pineal Region Masses—Imaging Findings and Surgical Approaches Forrester D. Lensing, MD,a Travis A. Abele, MD,a Walavan Sivakumar, MD,b Philipp Taussky, MD,b Lubdha M. Shah, MD,a and Karen L. Salzman, MDa
The anatomy of the pineal region is complex. Despite advances in surgical techniques since the first reported successful pineal region surgery in the early 20th century, pineal region surgery remains challenging owing to the proximity of deep cerebral veins and dorsal midbrain structures critical for vision. In this article, we review the relevant surgical anatomy of the pineal region and discuss historically important and current surgical approaches. We describe specific imaging features of pineal region masses that may affect surgical planning and review neoplastic and nonneoplastic masses that occur in the pineal region.
Overview and Anatomy The pineal gland is an endocrine gland composed of pineal and neuroglial cells that lies deep within the brain along the dorsal aspect of the diencephalon. Its primary function is the production and secretion of melatonin, a hormone that has been associated with human circadian rhythms, endocrine function, immune regulation, and aging.1,2 The pineal gland lies outside the blood-brain barrier, which allows direct diffusion of melatonin into systemic blood vessels.3 The anatomy of the pineal region is complex (Fig 1), and the pineal region is difficult to access surgically. The major parenchymal components of the pineal region From the aNeuroradiology Section, Department of Radiology, University of Utah Health Science Center, Salt Lake City, UT; and bDepartment of Neurosurgery, University of Utah Health Science Center, Salt Lake City, UT. Reprint requests: Karen L. Salzman, MD, Neuroradiology Section, Department of Radiology, University of Utah Health Sciences Center, Salt Lake City, UT. E-mail: [email protected]. Curr Probl Diagn Radiol 2014;XX:XX–XX. & 2014 Mosby, Inc. All rights reserved. 0363-0188/$36.00 + 0 http://dx.doi.org/10.1067/j.cpradiol.2014.05.007
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include the pineal gland, the posterior commissure, the habenular commissure, and the superior and inferior colliculi of the tectal plate. The pineal region is defined anteriorly by the posterior recesses of the third ventricle, superiorly by the cistern of the velum interpositum and posteriorly by the quadrigeminal plate cistern. Important vascular structures include the paired internal cerebral veins, the vein of Galen, and the medial posterior choroidal artery. Tumors of the pineal region may present with headache, impaired vision, nausea, impaired ambulation, and impaired memory. Common clinical signs include papilledema, ataxia, and abnormal eye movements including Parinaud syndrome (dorsal midbrain syndrome), loss of vertical gaze, nystagmus on attempted convergence, and pseudo–Argyll Robertson pupil, related to compression of the tectal plate.4
Cystic Pineal Region Masses Cavum Velum Interpositum Usually discovered incidentally, the cavum velum interpositum (CVI) is a true cerebrospinal fluid (CSF) cistern found more commonly in younger patients. Its clinical significance is uncertain, but CVI likely reflects a developmental variant. One study suggests that CVI may be seen in up to 6% of patients undergoing magnetic resonance imaging (MRI) of the brain.5 CVI has not been associated with other brain malformations. On axial imaging, CVI has a characteristic triangular shape (Fig 2) with the triangle's base at the splenium of the corpus callosum and the apex at the foramen of Monro.6 The density on computed tomography (CT) and signal intensity on MRI are identical to CSF. CVI always results in caudal displacement of the internal cerebral veins, a
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FIG 1. Sagittal graphic (A) and sagittal T2W image illustrating surgical anatomy of the pineal region. Pineal gland (pg and black arrow), splenium of the corpus callosum (Spl), posterior commissure (pc) internal cerebral vein (icv), vein of Galen (VG), tectal plate (TP) medial posterior choroidal artery (white arrow in A), posterior commissure (black arrow in B), velum interpositum (VIp), quadrigeminal plate cistern (qpc), and cerebral aqueduct (white arrowhead in B). (Adapted and used with permission from Amirsys, Inc.) (Color version of figure is available online.)
feature that may distinguish it from other intracranial cysts in the pineal region.
Pineal Cysts Also usually discovered incidentally, pineal cysts are rarely associated with clinical symptoms, and the advent of high-resolution MRI techniques has increased the rate of detection of pineal cysts.7 Pu et al8 reported a prevalence of 23% of pineal cysts in healthy adult volunteers, and macroscopic cysts or cystic changes within the pineal gland are seen in 22% of autopsy specimens.9 Surgical treatment and radiologic follow-up of nonobstructing pineal cysts remains
controversial.10,11 Occasionally, pineal cysts may be large enough to exert mass effect on the dorsal midbrain or obstruct CSF flow through the cerebral aqueduct and may require surgical removal or shunting. On imaging, cysts may be isodense to slightly hyperdense to CSF on CT. Calcifications may be present in the cyst wall. On MRI, cysts are usually isointense to slightly hyperintense to CSF on T1weighted imaging (T1WI) and may incompletely suppress on fluid-attenuated inversion recovery (FLAIR) images (Fig 3). Postcontrast images typically show thin linear enhancement of the cyst wall.12 Pineal cysts with typical features and wall thickness
FIG 2. Cavum velum interpositum. On sagittal T1W image (A), the internal cerebral veins are displaced downward (white arrows). Axial T2WI (B) demonstrates the characteristic triangular shape of this anatomical variant (black arrows).
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FIG 3. Pineal cyst. Axial T2W (A), axial FLAIR (B), and postcontrast axial T1WI (C) images show the typical appearance of a simple pineal cyst (white arrows). Note the incomplete suppression of signal on FLAIR and thin rim enhancement. FLAIR, fluid-attenuated inversion recovery.
less than 2 mm do not require follow-up, as benign pineal cysts may grow or shrink over time.10,11,13 If atypical features (wall thickness 42 mm, nodular enhancement) are present, clinical follow-up and serial imaging can document stability.
Arachnoid Cysts Arachnoid cysts occur in the pineal region and usually follow CSF signal intensity on all imaging
sequences. Arachnoid cysts may be differentiated from pineal region epidermoid cysts by their lack of diffusion restriction on diffusion-weighted imaging. Large arachnoid cysts in the quadrigeminal plate cistern may result in obstructive hydrocephalus.14 Endoscopic fenestration and CSF diversion can effectively treat symptomatic arachnoid cysts in this region. Smaller, asymptomatic arachnoid cysts in the pineal region (Fig 4) are typically managed conservatively.
FIG 4. Arachnoid cyst. Axial T2W (A) and postcontrast axial T1W (B) images show a well-circumscribed, nonenhancing cyst along the left lateral aspect of the pineal gland in the upper quadrigeminal plate cistern (white arrows). Lack of diffusion restriction can be helpful to differentiate an arachnoid cyst from an epidermoid cyst.
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FIG 5. Pineocytoma. Sagittal FLAIR (A) and postcontrast sagittal T1W (B) images demonstrate a FLAIR hyperintense mass with nodular enhancement (white arrow in B) and associated hydrocephalus (arrowheads in A) due to aqueductal obstruction (dashed arrow in A). FLAIR, fluidattenuated inversion recovery.
Pineal Parenchymal Tumors Pineocytoma Pineocytoma is derived from pineal parenchymal cells and is classified as a World Health Organization grade I tumor.15 Pineocytoma may present with headache, Parinaud syndrome due to compression of dorsal midbrain structures, or obstruction of the cerebral aqueduct. Their natural history is marked by slow growth, and the 5-year survival is excellent. Aggressive surgical resection may improve survival.16 On CT scan, pineocytoma engulfs (rather than explodes) pineal calcification.17 On MRI (Fig 5), lesions may be cystic, solid, or mixed. Cystic lesions frequently demonstrate thick, nodular rim enhancement.
Pineal Parenchymal Tumor of Intermediate Differentiation Pineal parenchymal tumor of intermediate differentiation (PPTID) is a WHO II/III tumor with a more aggressive appearance and clinical course than pineocytoma.15 Histopathologically, PPTID falls on a spectrum between pineocytoma and pineoblastoma. It is characterized by uniform round cells with moderate to high cellularity, moderate atypia, and low to moderate mitotic activity without necrosis.18 PPTID is more common in middle-aged and older individuals.19 CSF dissemination is uncommon. On CT scan, PPTID
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engulfs pineal calcifications and may appear hyperdense or heterogeneous. On MRI, areas of cystic change are common on T2-weighted imaging (T2WI) (Fig 6), which may not suppress on fluid-attenuated inversion recovery. Hemorrhage may or may not be present, and strong enhancement of solid components is common.20
Papillary Tumor of the Pineal Region Papillary tumor of the pineal region (PTPR) is a WHO II-III tumor of pineal origin with characteristic papillary features, ependymal-type rosettes, and pseudorosettes on pathology.19 PTPR is primarily a tumor of adults, and PTPR may be indistinguishable from PPTID and pineocytoma on imaging. Small case series have reported a higher incidence of intrinsic T1 signal hyperintensity in these tumors.21 Cystic change on T2WI has also been reported. Although the provided example enhances homogeneously (Fig 7), most tumors enhance heterogeneously.
Germ Cell Tumors Germ cell tumors of the pineal region may be germinomatous (90%) or nongerminomatous (10%). Overall, 90% of germinomas occur in patients younger than 20 years. Most of these tumors occur in the pineal region, but germinomas also occur in the suprasellar region and, more rarely, in the basal ganglia.22 On CT scan, germinoma is typically hyperdense.23 On MRI, a
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restricts on diffusion-weighted imaging (Fig 8) and shows lower apparent diffusion coefficient values than pineal parenchymal tumors.17,24 Germinoma may be multifocal, involving both the suprasellar and pineal regions and may have a propensity for CSF spread. If a germinoma is suspected, surgical treatment may be limited to endoscopic biopsy and ventricular diversion, as radiotherapy with or without chemotherapy is the mainstay of treatment.25
Meningioma
FIG 6. Pineal parenchymal tumor of intermediate differentiation. Axial T2W (A), postcontrast axial T1W (B), and axial FLAIR (C) images demonstrate a heterogeneous, partially cystic mass with incomplete suppression of cyst contents on FLAIR imaging (white arrow in C) and nodular rim enhancement (small white arrows in B). Sagittal T2W (D) image shows the postoperative appearance after infratentorial supracerebellar resection (dashed line). FLAIR, fluid-attenuated inversion recovery.
germinoma is typically hyperintense on T2WI and enhances avidly. Regions of cystic change are common. Owing to its high cellularity, a germinoma
Meningioma, although it is one of the most common intracranial tumors, includes only 10% of pineal region tumors. Meningioma of the pineal region typically arises from the falcotentorial junction or the posterior portion of the velum interpositum.26,27 Patients with such tumors typically present with ocular disturbances and coordination difficulty. Meningiomas in the pineal region share imaging features with meningiomas that occur elsewhere. Their signal on T2WI is variable and tumoral cysts may be present. The lesions enhance avidly on postcontrast imaging (Fig 9). Broad dural attachment, dural tail, and CSF vascular cleft signs may be used to confirm extra-axial location.
Glial and Mixed Origin Tumors Tectal Glioma Tectal glioma is a unique subset of brainstem gliomas characterized by a periaqueductal location and a benign clinical course.28,29 The patients are
FIG 7. Papillary tumor of the pineal region. Axial T2W (A) and postcontrast sagittal T1W (B) images show a homogenous T2-isointense, mildly enhancing mass (white arrows) arising from the pineal gland and resulting in aqueductal obstruction. Most PTPRs appear more heterogeneous than the provided example.
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FIG 8. Germinoma. Diffusion-weighted image (A) demonstrates characteristic diffusion restriction in a pineal region germinoma. Additional patients with multifocal germinoma involving the pineal region and the suprasellar region (dashed arrows) (B) and with a pineal mass and nodular enhancement in the chiasmatic and infundibular recesses of the third ventricle (solid arrows) indicating CSF spread (C).
almost universally less than 25 years old at presentation. Lesions usually present with triventricular hydrocephalus due to aqueductal obstruction (Fig 10). Tumors are usually isointense on T1WI and hyperintense on T2WI. Most tectal gliomas do not enhance.29 Owing to the relatively benign clinical course, patients are usually treated with CSF diversion and followed up with serial imaging.
categorized as a WHO I lesion.15,19 Originally described as occurring in the fourth ventricle, multiple cases have been described occurring in the pineal region.30,31 RGNT typically has a mixed solid cystic appearance on MRI (Fig 11). Hemorrhage and calcification are common.32 Enhancement characteristics are variable, but the solid portions usually enhance. RGNT is potentially curable with extensive surgical resection.
Rosette-Forming Glioneuronal Tumor
Melanoma
Rosette-forming glioneuronal tumor (RGNT) was first included in the WHO classification in 2007 and
Melanoma of the pineal region may be either primary or metastatic.33 It has been proposed that
FIG 9. Meningioma. Postcontrast axial T1W (A) and sagittal T2W (B) images demonstrate a homogenously enhancing mass in the pineal region with broad dural attachment (small white arrows in A) and inferior displacement of the internal cerebral veins (white arrow in B). An occipital transtentorial approach (dashed arrow) was performed for resection of the mass.
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FIG 10. Tectal glioma. Sagittal T2W (A) and postcontrast axial T1W (B) images show a mildly T2 hyperintense mass without enhancement arising from the tectum (dashed white arrow in B) and resulting in aqueductal obstruction and triventricular hydrocephalus.
primary melanoma in the pineal region arises from melanin-producing meningeal cells surrounding the pineal gland. Metastatic melanoma in the central nervous system is far more common. Central nervous system melanoma may vary in signal on T1WI, depending on the melanin content. Typically, lesions are hyperdense on CT, isointense to low signal on T2WI, and avidly enhancing (Fig 12). Diffusion restriction may be present, depending on cellularity. The treatment of pineal region melanoma varies. If there is known systemic disease, palliative surgery or
radiotherapy may be performed to alleviate ventricular obstruction.
Surgical Approaches Since the earliest reported successful pineal surgery by Krause in 1913 via the infratentorial supracerebellar approach,34 multiple surgical approaches to the pineal region have been developed (Fig 13). Although early attempts at pineal surgery were marred by high morbidity and mortality, newer surgical techniques
FIG 11. Rosette-forming glioneuronal tumor. Axial T2W (A), axial gradient echo (B), and postcontrast sagittal T1W (C) images demonstrate a T2 heterogeneous mass (white arrows in A) with areas of hemorrhage (arrowhead in B) and nodular rim enhancement (dashed arrows in C). Hemorrhage and calcification are common in RGNT.
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FIG 12. Metastatic melanoma. Axial noncontrast CT (A) and postcontrast sagittal T1W (B) images demonstrate an intrinsically hyperdense mass (arrowhead in A) with avid enhancement in the pineal region (dashed arrow in B). After resection of the mass, the patient was found to have a small scalp melanoma.
and instruments have dramatically improved the safety of surgery in the pineal region. Case reports from the 1920s and 1930s describe the trans–lamina terminalis approach (Fig 13, #1) in the removal of pineal region tumors. Today, the approach is reserved for large tumors of the anterior third ventricle.35 The trans–lamina terminalis approach requires a bifrontal craniotomy. Exposure of the anterior third ventricular region is adequate, but exposure of the pineal region is sub-optimal. This approach has been replaced by less morbid posterior and transcallosal approaches.
FIG 13. Overview of surgical approaches to the pineal region. Trans–lamina terminalis (1), transcortical transventricular (2), transcallosal interhemispheric (3), posterior interhemispheric (4), occipital transtentorial (5), and infratentorial supracerebellar (6).
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Originally described by VanWagenen36 in 1931, the transcortical transventricular approach (Fig 13, #2) uses a cortical incision to gain access to the lateral ventricle and subsequently expose the pineal region. This approach often requires stereotactic guidance and may be useful if the tumor extends anteriorly and superiorly into the lateral ventricle. The use of a cortical incision provides only limited exposure and adds morbidity.37 The subchoroid approach uses the natural plane between the fornix and the thalamus to access the posterior wall of the third ventricle and the pineal region.38 Dandy39 described the first interhemispheric transcallosal approach (Fig 13, #3) to the pineal region in 1921. Although he achieved some initial success with this approach, surgery in the pineal region remained excessively morbid before the advent of the surgical microscope and the development of advanced neurologic critical care techniques.34 Today, this technique is considered safe and is used if a mass is located above the deep venous structures or extends anteriorly into the third ventricle. The interhemispheric transcallosal approach may also be used for resection of colloid cysts of the third ventricle.40 The occipital transtentorial approach (Fig 13, #5) is carried out through an occipital craniotomy, which allows exposure to the pineal region between the occipital lobes after dividing the tentorium.41 The occipital transtentorial approach is ideal for large tumors and tumors that straddle the tentorial hiatus.42
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FIG 14. Endoscopic approach to the pineal region. Sagittal T2W (A) image demonstrates dilated third and lateral ventricles (arrows) and small massa intermedia (arrowhead) due to a mass (M) obstructing the cerebral aqueduct, indicating a favorable scenario for a single-entry endoscopic approach. Postcontrast sagittal T1W (B) image demonstrates expected trajectory for third ventriculostomy and biopsy.
Retraction of the occipital lobes may result in homonymous hemianopsia, usually a transient phenomenon. Popularized by Stein43 in 1971, the infratentorial supracerebellar approach (Fig 13, #6) is performed with the patient in a seated position. The cerebellar hemispheres descend with gravity, allowing dissection of the dorsal venous system and the velum interpositum off the tumor.41,44 This approach also allows access to the posterior third ventricle. This approach is best suited for small to medium tumors. The endoscopic approach is now the favored approach for pineal region mass biopsy.45,46 This
approach may be performed with 1 or 2 bur holes and allows access to the ventricular system. If the operative goals include relief of obstructive hydrocephalus due to a pineal region tumor, endoscopic third ventriculostomy can be performed during biopsy.46
Preoperative Imaging When endoscopic biopsy or third ventriculostomy, or both, are considered, surgery can be performed via a single- or dual-entry approach.41 If the ventricular system is markedly enlarged, the massa intermedia is
FIG 15. Venous anatomy of the pineal region. Axial CT venography maximum-intensity projection (A) and axial graphic (B) images showing major deep veins in the pineal region and their relationship to the tentorial notch (dashed line): internal cerebral veins (arrowheads), basal vein of Rosenthal (dashed arrows), and vein of Galen (solid arrow and VG). (Adapted and used with permission from Amirsys, Inc.) (Color version of figure is available online.)
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FIG 16. Importance of venous displacement in surgical planning. Sagittal T2W (A) image shows upward displacement of the internal cerebral veins (arrows); an infratentorial approach (dashed line) would be favored. Postcontrast T1W (B) image demonstrates downward displacement of the internal cerebral veins; a supratentorial approach (dashed line) would likely be favored.
small and the operative goal is biopsy of the lesion, a single-entry approach is ideal (Fig 14). If the ventricles are small, the massa intermedia is large and the tumor is located posterior or superior to the massa intermedia, a dual-entry approach may be favored.47,48 If tumor removal is the operative goal, a dual-entry approach may be necessary. The venous anatomy of the pineal region is highly variable (Fig 15) but important to consider in planning pineal region surgery.49 In the most common variant, the basal veins of Rosenthal (BVR) drain into the vein of Galen. In other variants, the BVRs may drain into the internal cerebral veins or straight sinus; the BVRs may be replaced by posterior mesencephalic veins or may be completely absent.49 Recognition of venous anatomy is important in surgical planning and may be accomplished with magnetic resonance venography, CT venography, and susceptibility weighted imaging. Injury to the deep veins during surgery has been associated with significant morbidity, including midbrain or thalamic ischemia, miosis, pyramidal symptoms, and coma.50 In addition to venous variants, the pineal region tumor's mass effect on the deep veins should also be considered preoperatively.49 If the internal cerebral veins are displaced cranially, the surgeon may prefer the infratentorial supracerebellar approach (Fig 16). If the internal cerebral veins are displaced caudally, the surgeon may prefer a supratentorial approach.26
Conclusion Pineal region masses are relatively rare, and the anatomy of the pineal region is complex. Despite
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advances in surgical technique and postoperative care, pineal region surgery remains technically difficult and the proximity of deep cerebral veins and dorsal midbrain increases the risk of surgical morbidity. Radiologists should be familiar with the spectrum of pathology that occurs in this region and factors that may alter the surgical approach, particularly venous displacement and variants in venous anatomy.
REFERENCES 1. Carrillo-Vico A, Guerrero JM, Lardone PJ, et al. A review of the multiple actions of melatonin on the immune system. Endocrine 2005;27:189-200. 2. Macchi MM, Bruce JN. Human pineal physiology and functional significance of melatonin. Front Neuroendocrinol 2004;25:177-95. 3. Ballabh P, Braun A, Nedergaard M. The blood-brain barrier: An overview: Structure, regulation, and clinical implications. Neurobiol Dis 2004;16:1-13. 4. Schild SE, Scheithauer BW, Schomberg PJ, et al. Pineal parenchymal tumors: Clinical, pathologic, and therapeutic aspects. Cancer 1993;72:870-80. 5. Aldur MM, Celik HH, Gürcan F, et al. Frequency of cavum veli interpositi in non-psychotic population: A magnetic resonance imaging study. J Neuroradiol 2001;28:92-6. 6. Chen CY, Chen FH, Lee CC, et al. Sonographic characteristics of the cavum velum interpositum. Am J Neuroradiol 1998;19:1631-5. 7. Nolte I, Brockmann MA, Gerigk L, et al. TrueFISP imaging of the pineal gland: More cysts and more abnormalities. Clin Neurol Neurosurg 2010;112:204-8. 8. Pu Y, Mahankali S, Hou J, et al. High prevalence of pineal cysts in healthy adults demonstrated by high-resolution, noncontrast brain MR imaging. Am J Neuroradiol 2007;28: 1706-9.
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9. Hasegawa A, Ohtsubo K, Mori W. Pineal gland in old age; quantitative and qualitative morphological study of 168 human autopsy cases. Brain Res 1987;409:343-9. 10. Al-Holou WN, Terman SW, Kilburg C, et al. Prevalence and natural history of pineal cysts in adults: Clinical article. J Neurosurg 2011;115:1106-14. 11. Barboriak DP, Lee L, Provenzale JM. Serial MR imaging of pineal cysts: Implications for natural history and follow-up. Am J Roentgenol 2001;176:737-43. 12. Osborn AG, Preece MT. Intracranial cysts: Radiologicpathologic correlation and imaging approach. Radiology 2006;239:650-64. 13. Fakhran S, Escott EJ. Pineocytoma mimicking a pineal cyst on imaging: True diagnostic dilemma or a case of incomplete imaging? Am J Neuroradiol 2008;29:159-63. 14. El-Ghandour NMF. Endoscopic treatment of quadrigeminal arachnoid cysts in children: Clinical article. J Neurosurg Pediatr 2013;12:521-8. 15. Louis DN, Ohgaki H, Wiestler OD, et al. The 2007 WHO classification of tumours of the central nervous system. Acta Neuropathol 2007;114:97-109. 16. Clark AJ, Ivan ME, Sughrue ME, et al. Tumor control after surgery and radiotherapy for pineocytoma. J Neurosurg 2010;113:319-24. 17. Smith AB, Rushing EJ, Smirniotopoulos JG. From the archives of the AFIP: Lesions of the pineal region: Radiologic-pathologic correlation. RadioGraphics 2010;30: 2001-20. 18. Kıyıcı H, Sanal B. Pineal parenchymal tumor of intermediate differentiation: A brief report. Eur J Basic Med Sci 2012;2: 30-3. 19. Osborn AG, Salzman KL, Thurnher MM, et al. The new World Health Organization classification of central nervous system tumors: What can the neuroradiologist really say? Am J Neuroradiol 2012;33:795-802. 20. Komakula S, Warmuth-Metz M, Hildenbrand P, et al. Pineal parenchymal tumor of intermediate differentiation: Imaging spectrum of an unusual tumor in 11 cases. Neuroradiology 2011;53:577-84. 21. Chang AH, Fuller GN, Debnam JM, et al. MR imaging of papillary tumor of the pineal region. Am J Neuroradiol 2008;29:187-9. 22. Kanagaki M, Miki Y, Takahashi JA, et al. MRI and CT findings of neurohypophyseal germinoma. Eur J Radiol 2004;49:204-11. 23. Ganti SR, Hilal SK, Stein BM, et al. CT of pineal region tumors. Am J Roentgenol 1986;146:451-8. 24. Dumrongpisutikul N, Intrapiromkul J, Yousem DM. Distinguishing between germinomas and pineal cell tumors on MR imaging. Am J Neuroradiol 2012;33:550-5. 25. Jackson C, Jallo G, Lim M. Clinical outcomes after treatment of germ cell tumors. Neurosurg Clin N Am 2011;22:385-94. 26. Lozier AP, Bruce JN. Meningiomas of the velum interpositum: Surgical considerations. Neurosurg Focus 2003;15:E11. 27. Satoh H, Uozumi T, Kiva K, et al. MRI of pineal region tumours: Relationship between tumours and adjacent structures. Neuroradiology 1995;37:624-30.
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28. Squires LA, Allen JC, Abbott R, et al. Focal tectal tumors: Management and prognosis. Neurology 1994;44:953-6. 29. Bowers DC, Georgiades C, Aronson LJ, et al. Tectal gliomas: Natural history of an indolent lesion in pediatric patients. Pediatr Neurosurg 2000;32:24-9. 30. Frydenberg E, Laherty R, Rodriguez M, et al. A rosetteforming glioneuronal tumour of the pineal gland. J Clin Neurosci 2010;17:1326-8. 31. Ghosal N, Furtado SV, Hegde AS. Rosette forming glioneuronal tumor pineal gland and tectum: An intraoperative diagnosis on smear preparation. Diagn Cytopathol 2010;38: 590-3. 32. Solis OE, Mehta RI, Lai A, et al. Rosette-forming glioneuronal tumor: A pineal region case with IDH1 and IDH2 mutation analyses and literature review of 43 cases. J Neurooncol 2011;102:477-84. 33. Arantes M, Castro AF, Romão H, et al. Primary pineal malignant melanoma: Case report and literature review. Clin Neurol Neurosurg 2011;113:59-64. 34. Choudhry O, Gupta G, Prestigiacomo CJ. On the surgery of the seat of the soul: The pineal gland and the history of its surgical approaches. Neurosurg Clin N Am 2011;22:321-33. 35. Dehdashti AR, de Tribolet N. Frontobasal interhemispheric trans-lamina terminalis approach for suprasellar lesions. Neurosurgery 2005;56:418-24. 36. VanWagenen WP. A surgical approach for the removal of certain pineal tumors. Report of a case. Surg Gynecol Obstet 1931;53:216-20. 37. Suzuki J, Iwabuchi T. Surgical removal of pineal tumors (pinealomas and teratomas). Experience in a series of 19 cases. J Neurosurg 1965;23:565-71. 38. Konovalov AN, Pitskhelauri DI. Principles of treatment of the pineal region tumors. Surg Neurol 2003;59:252-70. 39. Dandy WE. An operation for the removal of pineal tumors. J Surg Gynecol Obstet 1921;33:113-9. 40. Horn EM, Feiz-Erfan I, Bristol RE, et al. Treatment options for third ventricular colloid cysts: Comparison of open microsurgical versus endoscopic resection. Neurosurgery 2007;60:613-8 [discussion 618-620]. 41. Kennedy BC, Bruce JN. Surgical approaches to the pineal region. Neurosurg Clin N Am 2011;22:367-80 [viii]. 42. Shirane R, Shamoto H, Umezawa K, et al. Surgical treatment of pineal region tumours through the occipital transtentorial approach: Evaluation of the effectiveness of intra-operative micro-endoscopy combined with neuronavigation. Acta Neurochir (Wien) 1999;141:801-9. 43. Stein BM. The infratentorial supracerebellar approach to pineal lesions. J Neurosurg 1971;35:197-202. 44. Bruce JN, Ogden AT. Surgical strategies for treating patients with pineal region tumors. J Neurooncol 2004;69:221-36. 45. Robinson S, Cohen AR. The role of neuroendoscopy in the treatment of pineal region tumors. Surg Neurol 1997;48: 360-7. 46. Oi S, Shibata M, Tominaga J, et al. Efficacy of neuroendoscopic procedures in minimally invasive preferential management of pineal region tumors: A prospective study. J Neurosurg 2000;93:245-53.
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47. Morgenstern PF, Osbun N, Schwartz TH, et al. Pineal region tumors: An optimal approach for simultaneous endo scopic third ventriculostomy and biopsy. Neurosurg Focus 2011;30:E3. 48. O'Brien DF, Hayhurst C, Pizer B, et al. Outcomes in patients undergoing single-trajectory endoscopic third ventriculostomy and endoscopic biopsy for midline tumors presenting with obstructive hydrocephalus. J Neurosurg 2006;105: 219-226.
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49. Giordano M, Lüdemann WO, Stieglitz L, et al. Identification of venous variants in the pineal region with three-dimensional preoperative magnetic resonance imaging navigation in patients harbouring tumors in this area: Significance for surgical approach to the lesion. Clin Neurol Neurosurg 2011;113:387-92. 50. Youssef AS, Downes AE, Agazzi S, et al. Life without the vein of Galen: Clinical and radiographic sequelae. Clin Anat 2011;24:776-85.
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The anatomy of the pineal region is complex. Despite advances in surgical techniques since the first reported successful pineal region surgery in the early 20th century, pineal region surgery remains challenging owing to the proximity of deep cerebral veins and dorsal midbrain structures critical for vision. In this article, we review the relevant surgical anatomy of the pineal region and discuss historically important and current surgical approaches. We describe specific imaging features of pineal region masses that may affect surgical planning and review neoplastic and nonneoplastic masses that occur in the pineal region.
Overview and Anatomy The pineal gland is an endocrine gland composed of pineal and neuroglial cells that lies deep within the brain along the dorsal aspect of the diencephalon. Its primary function is the production and secretion of melatonin, a hormone that has been associated with human circadian rhythms, endocrine function, immune regulation, and aging.1,2 The pineal gland lies outside the blood-brain barrier, which allows direct diffusion of melatonin into systemic blood vessels.3 The anatomy of the pineal region is complex (Fig 1), and the pineal region is difficult to access surgically. The major parenchymal components of the pineal region From the aNeuroradiology Section, Department of Radiology, University of Utah Health Science Center, Salt Lake City, UT; and bDepartment of Neurosurgery, University of Utah Health Science Center, Salt Lake City, UT. Reprint requests: Karen L. Salzman, MD, Neuroradiology Section, Department of Radiology, University of Utah Health Sciences Center, Salt Lake City, UT. E-mail: [email protected]. Curr Probl Diagn Radiol 2014;XX:XX–XX. & 2014 Mosby, Inc. All rights reserved. 0363-0188/$36.00 + 0 http://dx.doi.org/10.1067/j.cpradiol.2014.05.007
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include the pineal gland, the posterior commissure, the habenular commissure, and the superior and inferior colliculi of the tectal plate. The pineal region is defined anteriorly by the posterior recesses of the third ventricle, superiorly by the cistern of the velum interpositum and posteriorly by the quadrigeminal plate cistern. Important vascular structures include the paired internal cerebral veins, the vein of Galen, and the medial posterior choroidal artery. Tumors of the pineal region may present with headache, impaired vision, nausea, impaired ambulation, and impaired memory. Common clinical signs include papilledema, ataxia, and abnormal eye movements including Parinaud syndrome (dorsal midbrain syndrome), loss of vertical gaze, nystagmus on attempted convergence, and pseudo–Argyll Robertson pupil, related to compression of the tectal plate.4
Cystic Pineal Region Masses Cavum Velum Interpositum Usually discovered incidentally, the cavum velum interpositum (CVI) is a true cerebrospinal fluid (CSF) cistern found more commonly in younger patients. Its clinical significance is uncertain, but CVI likely reflects a developmental variant. One study suggests that CVI may be seen in up to 6% of patients undergoing magnetic resonance imaging (MRI) of the brain.5 CVI has not been associated with other brain malformations. On axial imaging, CVI has a characteristic triangular shape (Fig 2) with the triangle's base at the splenium of the corpus callosum and the apex at the foramen of Monro.6 The density on computed tomography (CT) and signal intensity on MRI are identical to CSF. CVI always results in caudal displacement of the internal cerebral veins, a
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FIG 1. Sagittal graphic (A) and sagittal T2W image illustrating surgical anatomy of the pineal region. Pineal gland (pg and black arrow), splenium of the corpus callosum (Spl), posterior commissure (pc) internal cerebral vein (icv), vein of Galen (VG), tectal plate (TP) medial posterior choroidal artery (white arrow in A), posterior commissure (black arrow in B), velum interpositum (VIp), quadrigeminal plate cistern (qpc), and cerebral aqueduct (white arrowhead in B). (Adapted and used with permission from Amirsys, Inc.) (Color version of figure is available online.)
feature that may distinguish it from other intracranial cysts in the pineal region.
Pineal Cysts Also usually discovered incidentally, pineal cysts are rarely associated with clinical symptoms, and the advent of high-resolution MRI techniques has increased the rate of detection of pineal cysts.7 Pu et al8 reported a prevalence of 23% of pineal cysts in healthy adult volunteers, and macroscopic cysts or cystic changes within the pineal gland are seen in 22% of autopsy specimens.9 Surgical treatment and radiologic follow-up of nonobstructing pineal cysts remains
controversial.10,11 Occasionally, pineal cysts may be large enough to exert mass effect on the dorsal midbrain or obstruct CSF flow through the cerebral aqueduct and may require surgical removal or shunting. On imaging, cysts may be isodense to slightly hyperdense to CSF on CT. Calcifications may be present in the cyst wall. On MRI, cysts are usually isointense to slightly hyperintense to CSF on T1weighted imaging (T1WI) and may incompletely suppress on fluid-attenuated inversion recovery (FLAIR) images (Fig 3). Postcontrast images typically show thin linear enhancement of the cyst wall.12 Pineal cysts with typical features and wall thickness
FIG 2. Cavum velum interpositum. On sagittal T1W image (A), the internal cerebral veins are displaced downward (white arrows). Axial T2WI (B) demonstrates the characteristic triangular shape of this anatomical variant (black arrows).
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FIG 3. Pineal cyst. Axial T2W (A), axial FLAIR (B), and postcontrast axial T1WI (C) images show the typical appearance of a simple pineal cyst (white arrows). Note the incomplete suppression of signal on FLAIR and thin rim enhancement. FLAIR, fluid-attenuated inversion recovery.
less than 2 mm do not require follow-up, as benign pineal cysts may grow or shrink over time.10,11,13 If atypical features (wall thickness 42 mm, nodular enhancement) are present, clinical follow-up and serial imaging can document stability.
Arachnoid Cysts Arachnoid cysts occur in the pineal region and usually follow CSF signal intensity on all imaging
sequences. Arachnoid cysts may be differentiated from pineal region epidermoid cysts by their lack of diffusion restriction on diffusion-weighted imaging. Large arachnoid cysts in the quadrigeminal plate cistern may result in obstructive hydrocephalus.14 Endoscopic fenestration and CSF diversion can effectively treat symptomatic arachnoid cysts in this region. Smaller, asymptomatic arachnoid cysts in the pineal region (Fig 4) are typically managed conservatively.
FIG 4. Arachnoid cyst. Axial T2W (A) and postcontrast axial T1W (B) images show a well-circumscribed, nonenhancing cyst along the left lateral aspect of the pineal gland in the upper quadrigeminal plate cistern (white arrows). Lack of diffusion restriction can be helpful to differentiate an arachnoid cyst from an epidermoid cyst.
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FIG 5. Pineocytoma. Sagittal FLAIR (A) and postcontrast sagittal T1W (B) images demonstrate a FLAIR hyperintense mass with nodular enhancement (white arrow in B) and associated hydrocephalus (arrowheads in A) due to aqueductal obstruction (dashed arrow in A). FLAIR, fluidattenuated inversion recovery.
Pineal Parenchymal Tumors Pineocytoma Pineocytoma is derived from pineal parenchymal cells and is classified as a World Health Organization grade I tumor.15 Pineocytoma may present with headache, Parinaud syndrome due to compression of dorsal midbrain structures, or obstruction of the cerebral aqueduct. Their natural history is marked by slow growth, and the 5-year survival is excellent. Aggressive surgical resection may improve survival.16 On CT scan, pineocytoma engulfs (rather than explodes) pineal calcification.17 On MRI (Fig 5), lesions may be cystic, solid, or mixed. Cystic lesions frequently demonstrate thick, nodular rim enhancement.
Pineal Parenchymal Tumor of Intermediate Differentiation Pineal parenchymal tumor of intermediate differentiation (PPTID) is a WHO II/III tumor with a more aggressive appearance and clinical course than pineocytoma.15 Histopathologically, PPTID falls on a spectrum between pineocytoma and pineoblastoma. It is characterized by uniform round cells with moderate to high cellularity, moderate atypia, and low to moderate mitotic activity without necrosis.18 PPTID is more common in middle-aged and older individuals.19 CSF dissemination is uncommon. On CT scan, PPTID
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engulfs pineal calcifications and may appear hyperdense or heterogeneous. On MRI, areas of cystic change are common on T2-weighted imaging (T2WI) (Fig 6), which may not suppress on fluid-attenuated inversion recovery. Hemorrhage may or may not be present, and strong enhancement of solid components is common.20
Papillary Tumor of the Pineal Region Papillary tumor of the pineal region (PTPR) is a WHO II-III tumor of pineal origin with characteristic papillary features, ependymal-type rosettes, and pseudorosettes on pathology.19 PTPR is primarily a tumor of adults, and PTPR may be indistinguishable from PPTID and pineocytoma on imaging. Small case series have reported a higher incidence of intrinsic T1 signal hyperintensity in these tumors.21 Cystic change on T2WI has also been reported. Although the provided example enhances homogeneously (Fig 7), most tumors enhance heterogeneously.
Germ Cell Tumors Germ cell tumors of the pineal region may be germinomatous (90%) or nongerminomatous (10%). Overall, 90% of germinomas occur in patients younger than 20 years. Most of these tumors occur in the pineal region, but germinomas also occur in the suprasellar region and, more rarely, in the basal ganglia.22 On CT scan, germinoma is typically hyperdense.23 On MRI, a
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restricts on diffusion-weighted imaging (Fig 8) and shows lower apparent diffusion coefficient values than pineal parenchymal tumors.17,24 Germinoma may be multifocal, involving both the suprasellar and pineal regions and may have a propensity for CSF spread. If a germinoma is suspected, surgical treatment may be limited to endoscopic biopsy and ventricular diversion, as radiotherapy with or without chemotherapy is the mainstay of treatment.25
Meningioma
FIG 6. Pineal parenchymal tumor of intermediate differentiation. Axial T2W (A), postcontrast axial T1W (B), and axial FLAIR (C) images demonstrate a heterogeneous, partially cystic mass with incomplete suppression of cyst contents on FLAIR imaging (white arrow in C) and nodular rim enhancement (small white arrows in B). Sagittal T2W (D) image shows the postoperative appearance after infratentorial supracerebellar resection (dashed line). FLAIR, fluid-attenuated inversion recovery.
germinoma is typically hyperintense on T2WI and enhances avidly. Regions of cystic change are common. Owing to its high cellularity, a germinoma
Meningioma, although it is one of the most common intracranial tumors, includes only 10% of pineal region tumors. Meningioma of the pineal region typically arises from the falcotentorial junction or the posterior portion of the velum interpositum.26,27 Patients with such tumors typically present with ocular disturbances and coordination difficulty. Meningiomas in the pineal region share imaging features with meningiomas that occur elsewhere. Their signal on T2WI is variable and tumoral cysts may be present. The lesions enhance avidly on postcontrast imaging (Fig 9). Broad dural attachment, dural tail, and CSF vascular cleft signs may be used to confirm extra-axial location.
Glial and Mixed Origin Tumors Tectal Glioma Tectal glioma is a unique subset of brainstem gliomas characterized by a periaqueductal location and a benign clinical course.28,29 The patients are
FIG 7. Papillary tumor of the pineal region. Axial T2W (A) and postcontrast sagittal T1W (B) images show a homogenous T2-isointense, mildly enhancing mass (white arrows) arising from the pineal gland and resulting in aqueductal obstruction. Most PTPRs appear more heterogeneous than the provided example.
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FIG 8. Germinoma. Diffusion-weighted image (A) demonstrates characteristic diffusion restriction in a pineal region germinoma. Additional patients with multifocal germinoma involving the pineal region and the suprasellar region (dashed arrows) (B) and with a pineal mass and nodular enhancement in the chiasmatic and infundibular recesses of the third ventricle (solid arrows) indicating CSF spread (C).
almost universally less than 25 years old at presentation. Lesions usually present with triventricular hydrocephalus due to aqueductal obstruction (Fig 10). Tumors are usually isointense on T1WI and hyperintense on T2WI. Most tectal gliomas do not enhance.29 Owing to the relatively benign clinical course, patients are usually treated with CSF diversion and followed up with serial imaging.
categorized as a WHO I lesion.15,19 Originally described as occurring in the fourth ventricle, multiple cases have been described occurring in the pineal region.30,31 RGNT typically has a mixed solid cystic appearance on MRI (Fig 11). Hemorrhage and calcification are common.32 Enhancement characteristics are variable, but the solid portions usually enhance. RGNT is potentially curable with extensive surgical resection.
Rosette-Forming Glioneuronal Tumor
Melanoma
Rosette-forming glioneuronal tumor (RGNT) was first included in the WHO classification in 2007 and
Melanoma of the pineal region may be either primary or metastatic.33 It has been proposed that
FIG 9. Meningioma. Postcontrast axial T1W (A) and sagittal T2W (B) images demonstrate a homogenously enhancing mass in the pineal region with broad dural attachment (small white arrows in A) and inferior displacement of the internal cerebral veins (white arrow in B). An occipital transtentorial approach (dashed arrow) was performed for resection of the mass.
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FIG 10. Tectal glioma. Sagittal T2W (A) and postcontrast axial T1W (B) images show a mildly T2 hyperintense mass without enhancement arising from the tectum (dashed white arrow in B) and resulting in aqueductal obstruction and triventricular hydrocephalus.
primary melanoma in the pineal region arises from melanin-producing meningeal cells surrounding the pineal gland. Metastatic melanoma in the central nervous system is far more common. Central nervous system melanoma may vary in signal on T1WI, depending on the melanin content. Typically, lesions are hyperdense on CT, isointense to low signal on T2WI, and avidly enhancing (Fig 12). Diffusion restriction may be present, depending on cellularity. The treatment of pineal region melanoma varies. If there is known systemic disease, palliative surgery or
radiotherapy may be performed to alleviate ventricular obstruction.
Surgical Approaches Since the earliest reported successful pineal surgery by Krause in 1913 via the infratentorial supracerebellar approach,34 multiple surgical approaches to the pineal region have been developed (Fig 13). Although early attempts at pineal surgery were marred by high morbidity and mortality, newer surgical techniques
FIG 11. Rosette-forming glioneuronal tumor. Axial T2W (A), axial gradient echo (B), and postcontrast sagittal T1W (C) images demonstrate a T2 heterogeneous mass (white arrows in A) with areas of hemorrhage (arrowhead in B) and nodular rim enhancement (dashed arrows in C). Hemorrhage and calcification are common in RGNT.
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FIG 12. Metastatic melanoma. Axial noncontrast CT (A) and postcontrast sagittal T1W (B) images demonstrate an intrinsically hyperdense mass (arrowhead in A) with avid enhancement in the pineal region (dashed arrow in B). After resection of the mass, the patient was found to have a small scalp melanoma.
and instruments have dramatically improved the safety of surgery in the pineal region. Case reports from the 1920s and 1930s describe the trans–lamina terminalis approach (Fig 13, #1) in the removal of pineal region tumors. Today, the approach is reserved for large tumors of the anterior third ventricle.35 The trans–lamina terminalis approach requires a bifrontal craniotomy. Exposure of the anterior third ventricular region is adequate, but exposure of the pineal region is sub-optimal. This approach has been replaced by less morbid posterior and transcallosal approaches.
FIG 13. Overview of surgical approaches to the pineal region. Trans–lamina terminalis (1), transcortical transventricular (2), transcallosal interhemispheric (3), posterior interhemispheric (4), occipital transtentorial (5), and infratentorial supracerebellar (6).
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Originally described by VanWagenen36 in 1931, the transcortical transventricular approach (Fig 13, #2) uses a cortical incision to gain access to the lateral ventricle and subsequently expose the pineal region. This approach often requires stereotactic guidance and may be useful if the tumor extends anteriorly and superiorly into the lateral ventricle. The use of a cortical incision provides only limited exposure and adds morbidity.37 The subchoroid approach uses the natural plane between the fornix and the thalamus to access the posterior wall of the third ventricle and the pineal region.38 Dandy39 described the first interhemispheric transcallosal approach (Fig 13, #3) to the pineal region in 1921. Although he achieved some initial success with this approach, surgery in the pineal region remained excessively morbid before the advent of the surgical microscope and the development of advanced neurologic critical care techniques.34 Today, this technique is considered safe and is used if a mass is located above the deep venous structures or extends anteriorly into the third ventricle. The interhemispheric transcallosal approach may also be used for resection of colloid cysts of the third ventricle.40 The occipital transtentorial approach (Fig 13, #5) is carried out through an occipital craniotomy, which allows exposure to the pineal region between the occipital lobes after dividing the tentorium.41 The occipital transtentorial approach is ideal for large tumors and tumors that straddle the tentorial hiatus.42
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FIG 14. Endoscopic approach to the pineal region. Sagittal T2W (A) image demonstrates dilated third and lateral ventricles (arrows) and small massa intermedia (arrowhead) due to a mass (M) obstructing the cerebral aqueduct, indicating a favorable scenario for a single-entry endoscopic approach. Postcontrast sagittal T1W (B) image demonstrates expected trajectory for third ventriculostomy and biopsy.
Retraction of the occipital lobes may result in homonymous hemianopsia, usually a transient phenomenon. Popularized by Stein43 in 1971, the infratentorial supracerebellar approach (Fig 13, #6) is performed with the patient in a seated position. The cerebellar hemispheres descend with gravity, allowing dissection of the dorsal venous system and the velum interpositum off the tumor.41,44 This approach also allows access to the posterior third ventricle. This approach is best suited for small to medium tumors. The endoscopic approach is now the favored approach for pineal region mass biopsy.45,46 This
approach may be performed with 1 or 2 bur holes and allows access to the ventricular system. If the operative goals include relief of obstructive hydrocephalus due to a pineal region tumor, endoscopic third ventriculostomy can be performed during biopsy.46
Preoperative Imaging When endoscopic biopsy or third ventriculostomy, or both, are considered, surgery can be performed via a single- or dual-entry approach.41 If the ventricular system is markedly enlarged, the massa intermedia is
FIG 15. Venous anatomy of the pineal region. Axial CT venography maximum-intensity projection (A) and axial graphic (B) images showing major deep veins in the pineal region and their relationship to the tentorial notch (dashed line): internal cerebral veins (arrowheads), basal vein of Rosenthal (dashed arrows), and vein of Galen (solid arrow and VG). (Adapted and used with permission from Amirsys, Inc.) (Color version of figure is available online.)
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FIG 16. Importance of venous displacement in surgical planning. Sagittal T2W (A) image shows upward displacement of the internal cerebral veins (arrows); an infratentorial approach (dashed line) would be favored. Postcontrast T1W (B) image demonstrates downward displacement of the internal cerebral veins; a supratentorial approach (dashed line) would likely be favored.
small and the operative goal is biopsy of the lesion, a single-entry approach is ideal (Fig 14). If the ventricles are small, the massa intermedia is large and the tumor is located posterior or superior to the massa intermedia, a dual-entry approach may be favored.47,48 If tumor removal is the operative goal, a dual-entry approach may be necessary. The venous anatomy of the pineal region is highly variable (Fig 15) but important to consider in planning pineal region surgery.49 In the most common variant, the basal veins of Rosenthal (BVR) drain into the vein of Galen. In other variants, the BVRs may drain into the internal cerebral veins or straight sinus; the BVRs may be replaced by posterior mesencephalic veins or may be completely absent.49 Recognition of venous anatomy is important in surgical planning and may be accomplished with magnetic resonance venography, CT venography, and susceptibility weighted imaging. Injury to the deep veins during surgery has been associated with significant morbidity, including midbrain or thalamic ischemia, miosis, pyramidal symptoms, and coma.50 In addition to venous variants, the pineal region tumor's mass effect on the deep veins should also be considered preoperatively.49 If the internal cerebral veins are displaced cranially, the surgeon may prefer the infratentorial supracerebellar approach (Fig 16). If the internal cerebral veins are displaced caudally, the surgeon may prefer a supratentorial approach.26
Conclusion Pineal region masses are relatively rare, and the anatomy of the pineal region is complex. Despite
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advances in surgical technique and postoperative care, pineal region surgery remains technically difficult and the proximity of deep cerebral veins and dorsal midbrain increases the risk of surgical morbidity. Radiologists should be familiar with the spectrum of pathology that occurs in this region and factors that may alter the surgical approach, particularly venous displacement and variants in venous anatomy.
REFERENCES 1. Carrillo-Vico A, Guerrero JM, Lardone PJ, et al. A review of the multiple actions of melatonin on the immune system. Endocrine 2005;27:189-200. 2. Macchi MM, Bruce JN. Human pineal physiology and functional significance of melatonin. Front Neuroendocrinol 2004;25:177-95. 3. Ballabh P, Braun A, Nedergaard M. The blood-brain barrier: An overview: Structure, regulation, and clinical implications. Neurobiol Dis 2004;16:1-13. 4. Schild SE, Scheithauer BW, Schomberg PJ, et al. Pineal parenchymal tumors: Clinical, pathologic, and therapeutic aspects. Cancer 1993;72:870-80. 5. Aldur MM, Celik HH, Gürcan F, et al. Frequency of cavum veli interpositi in non-psychotic population: A magnetic resonance imaging study. J Neuroradiol 2001;28:92-6. 6. Chen CY, Chen FH, Lee CC, et al. Sonographic characteristics of the cavum velum interpositum. Am J Neuroradiol 1998;19:1631-5. 7. Nolte I, Brockmann MA, Gerigk L, et al. TrueFISP imaging of the pineal gland: More cysts and more abnormalities. Clin Neurol Neurosurg 2010;112:204-8. 8. Pu Y, Mahankali S, Hou J, et al. High prevalence of pineal cysts in healthy adults demonstrated by high-resolution, noncontrast brain MR imaging. Am J Neuroradiol 2007;28: 1706-9.
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9. Hasegawa A, Ohtsubo K, Mori W. Pineal gland in old age; quantitative and qualitative morphological study of 168 human autopsy cases. Brain Res 1987;409:343-9. 10. Al-Holou WN, Terman SW, Kilburg C, et al. Prevalence and natural history of pineal cysts in adults: Clinical article. J Neurosurg 2011;115:1106-14. 11. Barboriak DP, Lee L, Provenzale JM. Serial MR imaging of pineal cysts: Implications for natural history and follow-up. Am J Roentgenol 2001;176:737-43. 12. Osborn AG, Preece MT. Intracranial cysts: Radiologicpathologic correlation and imaging approach. Radiology 2006;239:650-64. 13. Fakhran S, Escott EJ. Pineocytoma mimicking a pineal cyst on imaging: True diagnostic dilemma or a case of incomplete imaging? Am J Neuroradiol 2008;29:159-63. 14. El-Ghandour NMF. Endoscopic treatment of quadrigeminal arachnoid cysts in children: Clinical article. J Neurosurg Pediatr 2013;12:521-8. 15. Louis DN, Ohgaki H, Wiestler OD, et al. The 2007 WHO classification of tumours of the central nervous system. Acta Neuropathol 2007;114:97-109. 16. Clark AJ, Ivan ME, Sughrue ME, et al. Tumor control after surgery and radiotherapy for pineocytoma. J Neurosurg 2010;113:319-24. 17. Smith AB, Rushing EJ, Smirniotopoulos JG. From the archives of the AFIP: Lesions of the pineal region: Radiologic-pathologic correlation. RadioGraphics 2010;30: 2001-20. 18. Kıyıcı H, Sanal B. Pineal parenchymal tumor of intermediate differentiation: A brief report. Eur J Basic Med Sci 2012;2: 30-3. 19. Osborn AG, Salzman KL, Thurnher MM, et al. The new World Health Organization classification of central nervous system tumors: What can the neuroradiologist really say? Am J Neuroradiol 2012;33:795-802. 20. Komakula S, Warmuth-Metz M, Hildenbrand P, et al. Pineal parenchymal tumor of intermediate differentiation: Imaging spectrum of an unusual tumor in 11 cases. Neuroradiology 2011;53:577-84. 21. Chang AH, Fuller GN, Debnam JM, et al. MR imaging of papillary tumor of the pineal region. Am J Neuroradiol 2008;29:187-9. 22. Kanagaki M, Miki Y, Takahashi JA, et al. MRI and CT findings of neurohypophyseal germinoma. Eur J Radiol 2004;49:204-11. 23. Ganti SR, Hilal SK, Stein BM, et al. CT of pineal region tumors. Am J Roentgenol 1986;146:451-8. 24. Dumrongpisutikul N, Intrapiromkul J, Yousem DM. Distinguishing between germinomas and pineal cell tumors on MR imaging. Am J Neuroradiol 2012;33:550-5. 25. Jackson C, Jallo G, Lim M. Clinical outcomes after treatment of germ cell tumors. Neurosurg Clin N Am 2011;22:385-94. 26. Lozier AP, Bruce JN. Meningiomas of the velum interpositum: Surgical considerations. Neurosurg Focus 2003;15:E11. 27. Satoh H, Uozumi T, Kiva K, et al. MRI of pineal region tumours: Relationship between tumours and adjacent structures. Neuroradiology 1995;37:624-30.
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28. Squires LA, Allen JC, Abbott R, et al. Focal tectal tumors: Management and prognosis. Neurology 1994;44:953-6. 29. Bowers DC, Georgiades C, Aronson LJ, et al. Tectal gliomas: Natural history of an indolent lesion in pediatric patients. Pediatr Neurosurg 2000;32:24-9. 30. Frydenberg E, Laherty R, Rodriguez M, et al. A rosetteforming glioneuronal tumour of the pineal gland. J Clin Neurosci 2010;17:1326-8. 31. Ghosal N, Furtado SV, Hegde AS. Rosette forming glioneuronal tumor pineal gland and tectum: An intraoperative diagnosis on smear preparation. Diagn Cytopathol 2010;38: 590-3. 32. Solis OE, Mehta RI, Lai A, et al. Rosette-forming glioneuronal tumor: A pineal region case with IDH1 and IDH2 mutation analyses and literature review of 43 cases. J Neurooncol 2011;102:477-84. 33. Arantes M, Castro AF, Romão H, et al. Primary pineal malignant melanoma: Case report and literature review. Clin Neurol Neurosurg 2011;113:59-64. 34. Choudhry O, Gupta G, Prestigiacomo CJ. On the surgery of the seat of the soul: The pineal gland and the history of its surgical approaches. Neurosurg Clin N Am 2011;22:321-33. 35. Dehdashti AR, de Tribolet N. Frontobasal interhemispheric trans-lamina terminalis approach for suprasellar lesions. Neurosurgery 2005;56:418-24. 36. VanWagenen WP. A surgical approach for the removal of certain pineal tumors. Report of a case. Surg Gynecol Obstet 1931;53:216-20. 37. Suzuki J, Iwabuchi T. Surgical removal of pineal tumors (pinealomas and teratomas). Experience in a series of 19 cases. J Neurosurg 1965;23:565-71. 38. Konovalov AN, Pitskhelauri DI. Principles of treatment of the pineal region tumors. Surg Neurol 2003;59:252-70. 39. Dandy WE. An operation for the removal of pineal tumors. J Surg Gynecol Obstet 1921;33:113-9. 40. Horn EM, Feiz-Erfan I, Bristol RE, et al. Treatment options for third ventricular colloid cysts: Comparison of open microsurgical versus endoscopic resection. Neurosurgery 2007;60:613-8 [discussion 618-620]. 41. Kennedy BC, Bruce JN. Surgical approaches to the pineal region. Neurosurg Clin N Am 2011;22:367-80 [viii]. 42. Shirane R, Shamoto H, Umezawa K, et al. Surgical treatment of pineal region tumours through the occipital transtentorial approach: Evaluation of the effectiveness of intra-operative micro-endoscopy combined with neuronavigation. Acta Neurochir (Wien) 1999;141:801-9. 43. Stein BM. The infratentorial supracerebellar approach to pineal lesions. J Neurosurg 1971;35:197-202. 44. Bruce JN, Ogden AT. Surgical strategies for treating patients with pineal region tumors. J Neurooncol 2004;69:221-36. 45. Robinson S, Cohen AR. The role of neuroendoscopy in the treatment of pineal region tumors. Surg Neurol 1997;48: 360-7. 46. Oi S, Shibata M, Tominaga J, et al. Efficacy of neuroendoscopic procedures in minimally invasive preferential management of pineal region tumors: A prospective study. J Neurosurg 2000;93:245-53.
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47. Morgenstern PF, Osbun N, Schwartz TH, et al. Pineal region tumors: An optimal approach for simultaneous endo scopic third ventriculostomy and biopsy. Neurosurg Focus 2011;30:E3. 48. O'Brien DF, Hayhurst C, Pizer B, et al. Outcomes in patients undergoing single-trajectory endoscopic third ventriculostomy and endoscopic biopsy for midline tumors presenting with obstructive hydrocephalus. J Neurosurg 2006;105: 219-226.
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49. Giordano M, Lüdemann WO, Stieglitz L, et al. Identification of venous variants in the pineal region with three-dimensional preoperative magnetic resonance imaging navigation in patients harbouring tumors in this area: Significance for surgical approach to the lesion. Clin Neurol Neurosurg 2011;113:387-92. 50. Youssef AS, Downes AE, Agazzi S, et al. Life without the vein of Galen: Clinical and radiographic sequelae. Clin Anat 2011;24:776-85.
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