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Neuroradiology Case of the Week

Case 163

Ravinder Sidhu, MD, Ajay Malhotra, MD and PL Westesson, MD, DDS, PhD

Clinical Presentation: Patient is a 16-year-old female presenting with headache.

Radiological Findings: A well-defined lesion of 1x1 cm size is seen in the anterior portion of the third ventricle. On T1-weighted images, the cyst shows hypointense signal (Figs. 1A&B). On T2-weighted images, the cyst is hyperintense with a hypointense rim (Fig. 2). Post-contrast images show faint enhancement of the rim (Fig. 3). No hydrocephalus is seen.

Diagnosis: Pineal cyst

Discussion: Pineal gland cystic lesions are seen in 21-41% on autopsy whereas on MR imaging, they are seen in 1-4% cases. Pineal gland lesions may be divided into four basic categories:

• Germ cell tumors
• Pineal parenchymal tumors
• Metastases
• Cysts

     Pineal cysts occur in all ages, more predominant in the fourth decade. They may be classified as neoplastic or benign as lined by glial tissue, ependymal, or surrounded by the normal texture of parenchymal tissue.
     Majority of the times, pineal cysts are asymptomatic. Pineal cysts are clinically important for 2 reasons: (1) They may enlarge over time due to intracystic hemorrhage / cyst fluid, and/or (2) May cause mass effect on adjacent structures. Mass effect on mid-brain may present with Perinaud's syndrome whereas mass effect on cerebral aqueduct causes hydrocephalus. Sudden death may also be seen due to acute hydrocephalus or intracystic hemorrhage, also called as pineal apoplexy.
     On MR imaging, they are seen as well-circumscribed, homogeneous signal characteristics associated to fluid. Signal may vary due to intracystic protein / hemorrhagic components. The walls of cysts are smooth measuring up to 2 mm. If cyst enlarges in size, mass effect on adjacent structures such as midbrain and aqueduct can be seen.
     The differential diagnosis of simple cysts and neoplastic lesions with cystic components, such as astrocytoma, pineocytoma, or pinealoblastoma, is of special importance. The markers of pineal tumors have been sought for many years, one of them is melatonin. Excessive secretion of melatonin may exist in true pineal tumors like pineocytomas, whereas low levels of melatonin favor benign pineal cystic lesions.
     If the cyst shows growth on successive MR images or progression of the clinical symptoms is observed, surgery is indicated.

References:

1. Mandera M, Marcol W, Bierzynska-Macyszyn G, Kluczewska E. Pineal cysts in childhood. Childs Nerv Syst. 2003 Nov;19(10-11):750-5. [Medline]
2. Kjos BO, Brant-Zawadzki M, Kucharczyk W, Kelly WM, Norman D, Newton TH. Cystic intracranial lesions: magnetic resonance imaging. Radiology. 1985 May;155(2):363-9. [Medline]