PMC6357539_01
Preoperative magnetic resonance imaging (MRI) studies. (a, b) Initial MRI study, axial (a) and coronal (b) T1-weighted scans (1/25/2012), showing a heterogeneous solid-cystic lesion centered at the chiasmatic recess of the third ventricle. Note the anterior tongue-like tumor protrusion into the optic chiasm (white arrow). In the coronal image, there is a round hypointense area of similar low intensity as the tumor is visible over the trajectory of the right optic tract (white arrow). (c-f) Preoperative MRI study obtained 6 months later, just prior to the surgical procedure (7/13/2012), showing enlargement of the tumor. The finger-like tumor tissue projecting into the optic chiasm-right optic nerve can be identified (white arrow). (d) Axial T2-weighted preoperative MRI scan, showing hyperintense symmetrical signals following the course of both optic tracts, a sign known as "moustache sign," which is believed to correspond to optic tract edema (white arrows). (e, f) Coronal and midsagittal T1-weighted scans demonstrating the strictly third ventricle topography of this craniopharyngioma, which has developed above an intact third ventricle floor/pituitary stalk (white arrows)
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The brain MRI displayed a 1.5-cm mixed solid-cystic lesion occupying the lower 3V and adjacent hypothalamic-chiasmatic region [Figure 1a-c]. An MRI study showed a significant enlargement of the 3V lesion, which had a basal cauliflower-like nodule and a cystic upper component [Figure 1d-f]. The optic chiasm was grossly distorted, showing a potbelly downward deformation on coronal sections, due to tumor infiltration [Figure 1e]. In addition, on T2-weighted axial images, the optic tracts displayed a "moustache-like" appearance, characterized by a hyperintense signal of edema extending along both optic tracts and into the adjacent hypothalamus [Figure 1d]. At the last visual assessment, six months after surgery, a significant worsening of the visual defect was evidenced on the perimetry (Figure 2, fourth perimetry on 01/21/2013), probably due to degenerative changes of retinal fibers associated with gliotic scarring.
Visual field exam. Correlation between visual field defects and the anatomical injury to the visual pathways caused by the tumor and surgical procedure. (a) Chronological evolution of the visual field defects identified in the patient through consecutive automated perimetry exams. (b) Illustrative schemes showing the sequence of anatomical injuries to the optic chiasm and optic tracts, presumably caused by the tumor and the surgical procedure, consistent with the visual defects shown in the corresponding perimetry studies on the left panel. (c). Artistic illustration showing the spatial antero-posterior segregation of retinal fibers within the optic chiasm that accounts for the visual defects associated with intrachiasmatic craniopharyngiomas (CPs). The crossed fibers from the retina's upper quadrants follow their course at a more caudal (posterior) position within the chiasm, whereas those from the retina's lower quadrants tend to cross at a more rostral or anterior position within the chiasm. At the initial exam, the patient presented a homonymous left inferior quadrantanopia with worse visual acuity in the right eye (perimetry on 1/26/2012), a result congruent with the invasion of the chiasm's posterior aspect and right optic tract's medial aspect (top scheme in B). As the tumor enlarges, it encroaches upon a wider area of the posterior and central chiasm, including both optic tracts, thus damage resulting in a severe visual deficit (second perimetry on 07/16/2012) that only spared the uncrossed temporal inferior fibers from the left retina along the chiasm's left edge (second scheme from the top in (b) and brown tract of fibers in (c)). After removal of the CP, the persistence of the visual deficit in the lower quadrants of the right eye and in the nasal quadrants of the left eye (immediate postoperative perimetry on 8/6/2012) was congruent with irreversible injury to the chiasm's posterior aspect and the medial aspect of the right optic tract (third scheme from the top in B and blue tract of fibers in C). The late postoperative perimetry exam (postoperative perimetry on 01/21/2013) showed a significantly worsening of the visual defect, probably due to degenerative changes in retinal fibers associated with gliotic scarring (bottom scheme in B)
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Visual fields were impaired severely in both eyes with a generalized loss of sensitivity in the right one and sparing of the upper nasal quadrant of the left eye (Figure 2a, perimetry on 07/16/2012). Pathological diagnosis identified a CP of the squamous-papillary variety [Figure 4b1 and b2]. A marked improvement of vision in the nasal hemi-field in the left eye was observed as well, although only a partial recovery at the temporal-superior quadrant of the right eye occurred (Figure 2, third perimetry on 8/6/2012). At the last visual assessment, six months after surgery, a significant worsening of the visual defect was evidenced on the perimetry (Figure 2, fourth perimetry on 01/21/2013), probably due to degenerative changes of retinal fibers associated with gliotic scarring.
Optical coherence tomography (OCT) exams. Analysis of the changes in the retinal nerve fiber layer (RNFL) thickness that occurred as the result of the chiasmal damage associated with this intrachiasmatic craniopharyngioma and the surgical procedure for its removal. Left panel: Preoperative OCT confirmed the presence of RNFL thinning involving the superior and temporal wedges (or quadrants) of both eyes, more severe in the upper retina of the right eye (yellow wedge). Right panel: Postoperative OCT demonstrated further thinning of the RNFL in the upper retina of the right eye as well as in the temporal wedge of the left retina (orange wedges). Such a thinning reflected the irreversible damage of the axonal fibers within the area of the optic chiasm and optic tracts infiltrated by the tumor, a result indicative of a worse prognosis for recovery following the surgery
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OCT (SD-OCT SPECTRALIS, Heidelberg Engineering, Heidelberg, Germany, Software 5.3) was used to reveal slight thinning of the RNFL in the superior and temporal wedges of the right eye (90 mum on average) and atrophy of the temporal wedge in the left eye (Figure 3, preoperative OCT).
(a) Intraoperative view and histological diagnosis. Surgical view through the right frontal-temporal (pterional) approach showing the anatomical deformation of the optic chiasm under microscopic magnification. A prefixed, swollen optic chiasm is observed. Note the bulging of the lamina terminalis (yellow arrow) and the whitish expansion of the right optic tract, a sign of tumor infiltration. A1: A1 segment of the right anterior cerebral artery; ACoA: anterior communicating artery; CA: carotid artery; M1: M1 proximal segment of the right median artery; LON: left optic nerve; RON: right optic nerve; b1-b2: histopathological sections showing the distinctive features of this squamous-papillary craniopharyngioma. Solid areas of well-differentiated stratified squamous epithelium with basal palisading and pseudopapillae formation around cores of loose fibrovascular stroma are typical of this variant. H and E, original magnification x 16 (b1) and x 40 (b2)
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It was displaced against the tuberculum sellae and presented a quite swollen and shortened appearance [Figure 4a]. The lesion could be dissected out from the 3V walls, except at its solid basal portion where a solid tongue of the tumor infiltrated the right posterolateral region of the chiasm and extended into the swollen proximal portion of the right optic nerve [Figure 4a]. Pathological diagnosis identified a CP of the squamous-papillary variety [Figure 4b1 and b2].
Postoperative MRI studies. (a) Midsagittal T1-weighted MRI scan after total removal of this intrachiasmatic craniopharyngioma. The outline of the prefixed, downward displaced optic chiasm (white arrow) is observed next to the defective or "breached" third ventricle floor, as the atrophic tuber cinereum was removed along with the tumor. (b, c) Axial and coronal T1-weighted scans through the level of the optic apparatus. Notice the anatomical injury to the optic chiasm-right optic tract junction after removing the lesion (white arrows)
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Complete removal of the lesion was confirmed on postoperative MRI [Figure 5a], with a small defect or breach at the 3V floor that extended to the junction of the optic chiasm and the right optic tract, just at the site where the tumor infiltrated the chiasm [Figure 5b and c].