Ординатура / Офтальмология / Английские материалы / Imaging of Orbital and Visual Pathway Pathology_Muller-Forell_2005

depend on their histological type and site. With respect to visual pathway disturbances, involvement of the pineal gland may lead to Parinaud’s syndrome, which is characterized by paralysis of the upward gaze and convergence (Fig. 7.54), whereas a suprasellar growth typically impinges on the chiasm with resulting visual or cranial nerve problems (Figs. 7.53, 7.55). Hormonal disturbances may be an additional and in some cases the only clinical symptomatology (Fig.7.52) caused by infiltration and disruption of the hypothalamic-hypophyseal axis with pituitary fail-

ure. These patients present with the clinical symptoms of diabetes insipidus, growth retardation (Figs. 7.53, 7.55), precocious puberty, or retarded sexual maturation (Kucharczyk et al. 1996; Rosenblum et al. 2000).

Pinealoblastomas are rare, malignant, poorly differ-entiated embryonal tumors of the pineal gland (WHO grade IV), accounting for about 45% of all pineal parenchymal tumors. They may arise in any age group, but with a dominance of the first two decades and a slight male preponderance (Mena et

al. 2000). They often infiltrate surrounding structures, including the meninges, responsible for common craniospinal dissemination. The clinical presentation is mostly unspecific with signs of increased intracranial pressure and neuro-ophthalmological deficits as, e.g., Parinaud’s syndrome, similar to those found in other tumors of the pineal region (Fig. 7.56) (Sartor 1992).

Imaging Characteristics. As germinomas are composed of large polygonal germ cells and clusters of lymphocytes in a dense connective tissue stroma,

they appear as a solid, homogeneous mass on imaging. In contrast to craniopharyngioma, they rarely include cystic parts. Suprasellar germinomas tend to infiltrate the hypothalamus, are not encapsulated, and, like pineal germ cell tumors, tend to spread into the subarachnoid space. Appearing hyperdense on CT, hyperintense on MRI (even unspecific) on T2-weighted views, and slightly hypointense in T1weighted images, marked enhance-ment is seen after contrast administration with both imaging techniques (Figs. 7.52–7.55) (Osborn and Raus-

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Fig. 7.53a–g. A 10-year-old girl with recurrent vomiting and severe weight loss. Ophthalmologic examination detected paleness of the optic papilla, but no deficit of the visual field. Diagnosis: malignant germinoma of the pituitary gland. MRI: a Axial T2-weighted view at the level of the optic chiasm where the partly cystic tumor occupies the entire pentagon cistern and causes spreading of the vessels of Willis’ circle.Although the chiasm and the anterior part of the expanded left optic tract are visualized, the corresponding right structures are hidden by the tumor. b Corresponding T1-weighted, contrastenhanced view. c Corresponding diagram: 12.2 = chiasm, 12.3 = optic tract. d Axial T2-weighted view at the level of the anterior commissure demonstrating the intraventricular (III ventricle) growth between the extended columns of the fornix (arrowheads). e Coronal, T1-weighted, contrast-enhanced view showing the lobulated configuration of the lesion with an interfornical tumor segment (white arrow). f Midsagittal, T1-weighted, contrast-enhanced image, demonstrating the caudocranial direction of the tumor growth arising from the widened sella, along the no longer identifiable pituitary stalk, dislocating the chiasm (small white arrow) anterior, invading the hypothalamus and third ventricle, and expanding superiorly to the level of the internal cerebral veins (large white arrow). g Corresponding diagram: 3.3 = sella turcica, 3.5 = clivus, 12.2 = chiasm, 15.2 = internal cerebral vein, 15.3 = vein of Galen

W. Müller-Forell

a

12.2

chning 1994; Kucharczyk et al. 1996). Pineoblastomas may already be quite large at the

time of diagnosis (Fig. 7.56) and present as a lobulated, in some cases poorly demarcated homogeneous mass with heterogeneous contrast enhancement, depending on the portion of solid tumor tissue (Sartor 1992; Osborn and Rauschning 1994). The MRI appearance of teratoma is related to the respective tumor grade. Benign teratoma (Fig. 7.57) thus shows a heterogeneous composition of different tissues (generally including fat and/or calcifications with hypoand hyperdense areas on CT, respectively) with a well demarcated lesion in the absence of invasion of the adjacent brain structures. In contrast, malignant teratoma shows no fat signal, but tumor infiltration of brain parenchyma with perifocal edema is usually present (Sartor 1992).

7.2.1.7.2 Metastasis

Secondary lesions should always be included in differential diagnostic considerations of extrinsic and even intrinsic tumors of the sellar region,particularly with a view to the capacity of some primarily extracranial tumors to involve the skull base (per continuitatem) or be hematogenous. Metastases involving the cavernous sinus predominantly arise from malignant tumors of the nasal cavity, growing perineurally or perivascu-larly via the basal foramina. They primarily become symptomatic because of cranial nerve deficits, e.g., double vision or ptosis. The leading entities of this tumor group consist of squamous cell carcinoma and adenoid cystic carcinoma of the epipharyngeal and nasal/paranasal region. A number of these reach the intracranial space with considerable destruction of the skull base, since the dura does not serve as a barrier over a prolonged period of time. The location of the metastasis determines the neurologic symptomatology (Fig. 7.58).

Imaging characteristics are nonspecific and similar to those encountered in more common tumors of the sellar region (Sartor 1992; Kucharczyk et al. 1996).

7.2.1.7.3

Cavernoma (Syn. Cavernous Hemangioma) of the Cavernous Sinus

Defined as the only venous vascular malformation consisting of thin-walled venous sinusoids without intervening neural tissue (Rosenblum et al. 1986), in neurologic patients, cavernoma are primarily localized in the brain parenchyma (Berenstein and

Lasjaunias 1992). In rare instances of intracranial extraparenchymal location in adults, the cavernous sinus is involved in the majority of cases (Suss et al. 1984; Tannouri et al. 2001), representing the basis for a differential diagnosis from meningioma or neurinoma of the cavernous sinus. Cavernoma of the cavernous sinus obviously originate from the dural compartment (Willing et al.1993) and present clinically with unspecific symptoms such as retro-orbital pain or ocular nerve disorders (Fig. 7.59). They present as well-defined tumorous lesions with a homogeneous, intermediate signal on T1-weighted views, a hyperintense signal on T2-weighted sequences, and homogeneous, massive enhancement after gadolinium administration (Fig. 7.59).

7.2.1.7.4 Chordoma

Arising from intraosseous vestigial remnants of the notochord, chordomas are extremely rare, with an incidence of less than 1% of all intracranial neoplasms. They are slow growing, osteodestructive, histologically benign, midline tumors with variable calcification and intratumoral hemorrhage (Zülch 1986; Okazaki 1989). They participate in ophthalmic disorders in only rare cases, i.e., when they arise from the clivus with an extension towards the chiasm (Fig. 7.60). On MRI, chordomas present with an intermediate signal on T1-weighted and a marked signal on T2weighted images, but with only moderate enhancement after Gd-DTPA administration (Meyers et al. 1992). The differential diagnosis should include chondromas, chondro-sarcomas, metastasis, as well as destructive, hormone-inactive pituitary adenomas or skull base meningiomas (Meyers et al. 1992).

7.2.1.7.5

Tolosa-Hunt Syndrome

The Tolosa-Hunt syndrome (THS) is an inflammatory disease of unknown origin, limited to the superior orbital fissure and the cavernous sinus (Smith and Taxdal 1966). The presentation of cranial nerve paresis of one or several of the cranial nerves passing the cavernous sinus (N III, N IV, N VI, and N V1) may coincide with the onset of orbital pain or follow it within a period of up to 2 weeks. The pain must be relieved within 72 h after steroid therapy. Although high resolution CT or MRI can neither exclude nor confirm THS when a lesion compatible with an inflammatory process is visualized, other causative lesions as, e.g., a malignant tumor must be excluded

(Forderreuther and Straube 1999). Clinical and neuroradiological follow-up must be done for at least 2 years, even in patients with negative findings on imaging at onset (Schramm and HÄhnel 2001).

7.2.1.7.6 Cystic Lesions

In the differential diagnosis of suprasellar tumorlike lesions, arachnoid cyst and epidermoid cyst play some important role, along with Rathke’s cleft cyst and hypothalamic hamartoma.

Rathke’s cleft cyst, a benign epithelium-lined cyst arising from remnants of Rathke’s pouch, may become symptomatic in the case of intraand suprasellar extension, a rather rare condition (Rose et al. 1992). On MRI, signal intensities vary

with cyst content from serous to mucoid (Osborn 1994b).

Arachnoid cysts account for about only 1% of all intracranial space-occupying lesions, but 10% arise in the suprasellar region (Armstrong et al. 1983). Arachnoidal cysts are filled with CSF; the etiology of these mainly congenital lesions remains poorly understood and controversial, but meningeal mal-develop- ment is preferred, so that minor aberrations of CSF flow through the loose, primitive, perimedullary mesenchyme are considered to result in a focal splitting of leptomeninges and the formation of a diverticulum or blind pocket within the arachnoid membrane (Schachenmayr and Friede 1979; Becker et al. 1991).As an arachnoid cyst is a well defined,sharply demarcated, extra-axial formation filled with CSF, MRI signal characteristics correspond with hypointense signal on T1-