Preoperative Evaluation

Patients with primary pineal region tumors present with signs and symptoms of hydro-cephalus secondary to compression or involvement of the tectum, occluding the Sylvian aqueduct, including headaches, diplopia, lethargy and ataxia. Compression of the tectum may also cause Parinaud's syndrome, resulting in vertical gaze paresis, impaired pupillary light reflex and convergence nystagmus. The clinical presentation for germ cell tumors is dependent upon the sites of involvement. Suprasellar involvement, particularly with germinomas, may be associated with a long prodrome (month to several years) of signs and symptoms of hypopituitarism. Diabetes insipidus is most common because of the involvement of the infundibulum, but growth failure and hypothy-roidism or precocious puberty can also be seen. Children with diabetes insipidus or hypopituitarism may harbor germ cell tumors and should be followed expectantly with MRI scans at regular intervals. Visual field or acuity impairments may occur related to compression of the optic chiasm or direct involvement of the optic nerve. Germinomas can spread directly along the floor and walls of the third ventricle or via CSF pathways. NGGCT have a higher incidence of metastatic dissemination than germinomas, with estimates ranging from 5 to 57%. Etraneural metastasis has been reported in up to 3% of all germ cell tumors, with lung and bone being the most common sites [16].

MRI is the radiographic imaging of choice in evaluating patients with pineal region tumors. CT, however, can be helpful in looking for calcification of the pineal region, which can be seen in the normal gland, germinomas, pineo-cytomas and teratomas, or for assessing hemorrhage and degree of ventriculomegaly. On MRI scans, germinomas are often isointense to gray matter, and slightly hyperintense on T2-weighted images. These tumors have homogeneous and dramatic contrast enhancement. Cystic areas can occasionally be seen. It is important to assess the suprasellar region and lateral and third ventricles for tumor involvement. There are no typical radiographic features of NGGCT, but they are often heterogeneous on MRI scans and tend to have infiltrating borders with variable degrees of enhancement. Teratomas, in particular, have marked heterogeneity, loculations and irregular enhancement related to lipid, soft tissue and cystic components as well as calcification. Malignant teratomas have similar features but demonstrate invasion into the surrounding structures [21]. Pineoblastomas are often heterogeneous on T1-weighted sequences and tend to be hyperintense on T2-weighted sequences. There is usually strong enhancement with some heterogeneous areas within the tumor (Figure 13.4). These tumors are aggressive and frequently disseminate in the neuraxis. There may be regions of necrosis or hemorrhage contributing to the heterogeneity. Pineocytomas are typically iso or hypointense on T1-weighted imaging with homogeneous and intense enhancement. However, pineocytomas can have variable appearance and can be associated with a hypointense cyst on T1-weighted images, similar to pineal cysts. MRI also provides critical anatomic information when considering surgical approach, extension of the tumor, the degree of brainstem involvement and the relationship of the deep venous system to the tumor.

All patients with pineal region tumors should undergo a high-resolution MRI scan with gadolinium of the head and screening MRI of the spinal axis (post-contrast sagittal view). Patients also require CSF and serum measurements of AFP, human chorionic gonadotropin (HCG) and CEA levels. CSF should also be sent for cytology. Evaluation of pituitary function should be performed if endocrine abnormalities are suspected and formal visual field examination in patients with evidence of suprasellar involvement.

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