Intrachiasmatic craniopharyngioma: Assessment of visual outcome with optical coherence tomography after complete surgical removal

Abstract

Background: Optic chiasm invasion by a craniopharyngioma (CP) is exceptional. Surgical treatment of intrachiasmatic CPs associates a high risk of chiasm injury, which should be properly addressed before surgery.

Case description: We present a 46-year-old woman admitted to the hospital with low visual acuity (0.1 in the right eye and 0.5 in the left) and a severe defect in her visual fields, in addition to headaches, diabetes insipidus, and a long-term depressive disorder. Her visual deficit progressed from a right homonymous temporal inferior quadrantanopia to an almost complete loss of vision in both eyes that only spared the upper nasal quadrants. Brain MRI showed a rounded third ventricle tumor with a potbelly expansion of the optic chiasm, suggesting chiasm invasion by the tumor. Optical coherence tomography (OCT) showed the thinning of the retinal nerve fiber layer (RNFL) in the superior and temporal wedges of the right eye and in the temporal wedge of the left one. The tumor was completely removed by employing a frontotemporal craniotomy and a translamina terminalis approach. Histological analysis showed a squamous-papillary CP. Postoperatively, a significant worsening of the visual defect was evidenced on the perimetry, which was related to a marked RNFL atrophy measured with OCT, as compared to the preoperative study. The poor long-term visual outcome in this patient correlated well with the results of postoperative OCT.

Conclusions: Preoperative analysis of retinal atrophy with optic coherence tomography allows a reliable assessment of the patient's visual outcome in CPs involving the optic chiasm.

Keywords: Craniopharyngioma; optic chiasm; optical coherence tomography; third ventricle; visual outcome.

Figure 1

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)

Figure 2

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)

Figure 3

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

Figure 4

(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 × 16 (b1) and × 40 (b2)

Figure 5

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)