Neuroendoscopy via an Extremely Narrow Foramen of Monro: A Case Report

Abstract

Herein, safe and reliable neuroendoscopic biopsy via an extremely narrow foramen of Monro (ENFM) for a non-hydrocephalic patient with hypothalamic and pineal region tumors was successfully applied. A 17-year-old boy presented with hypothalamic manifestations attributed to hypothalamic and pineal region tumors. Small ventricles were seen. Intraoperatively, to advance different diameter steerable fiberscopes via ENFM, the third ventricle was flushed to induce a moment increase in the intraventricular pressure with subsequent dilatation of FM. Postoperative course was uneventful. Histopathological studies revealed a yolk sac tumor. Adjuvant therapy was applied. Follow-up neuroimaging disclosed marvellous improvement of the condition. His symptoms gradually improved.

Keywords: endoscopic biopsy; fiberscope; foramen of Monro; pineal tumor; small ventricle.

Fig. 1

Preoperative MRI; (A) Post-contrasted sagittal MRI showing the suprasellar hypothalamic tumor (red circle) measuring 29 mm and pineal region tumor (black arrows) measuring 9 mm in the maximum diameters. Fourth ventricular nodules (red arrows), indicating dissemination, are seen. (B) Post-contrasted axial MRI showing no hydrocephalus (red circle), notice the extremely narrow foramina of Monro and the slit-like third ventricle (yellow circle). (C) FLAIR-MRI axial view, showing edema of the fornix with subsequent narrowing of the foramina of Monro “ left = 2.02 mm, right = 1.35 mm in diameters ” (yellow circle). (D) Zoom in (400%) at the level of the extremely narrow foramina of Monro, the right route (white line) is narrower than the left one (red line).

Fig. 2

Neuroendoscopic video-captured images; (A, B, C) A 2.5 mm fiberscope during careful endoscopic inspection. The major anatomical landmarks were identified: “the choroid plexus (CP) passing through an extremely narrow FM (M) to the third ventricle, and at its lower margin the point where the thalamostriate vein unites with the septal vein (Sv)”. The whitish hypothalamic tumor (T) was visualized inside the 3^rd ventricle. Notice the (image B) flushing-induced dilatation of the FM. (D) A 3.7 mm fiberscope was used to get tumor biopsies. (E–I) A 5.0 mm videoscope was introduced in order to gain accurate pertinent anatomical orientation and to obtain reliable biopsies. Before flushing the ventricle was like a gorge (E), however, during flushing the landmarks became gradually obvious (F). Just before passing through the FM to the third-ventricle: a closer position of the fiberscopes showing the efficacy of the flush technique (B and G). Notice the degree of FM dilatation and its’ increased diameter (a space was created around the CP “red arrows”). Additionally, the high resolution images obtained by the 5.0 mm videoscope ruled-out any forniceal injury (I). CP: choroid plexus, M: foramen of Monro, Sv: Septal vein, T: tumor, *: tumor forceps.

Fig. 3

Schematic drawing showing the flush technique, (A) A direct bolus of 10-ml warm artificial CSF solution was flushed gradually, via the endoscopic channel (red arrow). (B) A moment increase in the intra-third-ventricular pressure (brown arrows) and subsequent dilatation of the FM were achived. Simultaneously, the fiberscope (red arrow) was safely advanced to the third ventricle (yellow arrow). The third ventricular size became comparable.

Fig. 4

Postoperative and follow-up neuroimaging; (A) CT on postoperative day 1 ruled out surgery-related complications. (B) Follow-up post-contrasted sagittal MRI 3 months postoperatively (effect of adjuvant therapy) disclosed marvelous improvement of the condition and almost disappearance of the intracranial lesions C: Follow-up FLAIR-MRI axial view 6 months postoperatively, showing resolution of the forniceal edema and normalization of the foramina of Monro (left = 4.98 mm, right = 4.25 mm in diameters).

Fig. 5

Immunohistochemical and histopathological studies; (A) (AFP × 10) and (B) (AFP × 20): Immunohistochemical staining for α -fetoprotein (AFP), tumor cells showed strong cytoplasmic staining. (C) (HE × 10) and (D) (HE × 20): Photomicrograph of histopathological sections with hematoxylin and eosin (HE) staining: small slit-like spaces lined by atypical tumor cells. Tumor cells were pleomorphic, had abundant eosinophilic or clear cytoplasm and marked nucleoli which were arranged in nest or reticular pattern. Papillary growth pattern and mitotic figures could be found.