Gamma knife radiosurgery for a rare Rosette-forming glioneuronal tumor in the brainstem region: A case report and literature review

Abstract

Rationale: Rosette-forming glioneuronal tumor (RGNT) is a rare primary nervous system tumor, with limited treatment guidelines due to its rarity, especially in the brainstem. This report presents a unique case of brainstem RGNT treated with gamma knife radiosurgery (GKRS).

Patient concerns: A 35-year-old woman sought medical attention after sudden syncope and rapid decline in consciousness. Magnetic resonance imaging revealed a mass in the pineal region, extending to the brainstem and thalamus. Due to the critical location, only partial resection of the pineal tumor was possible, leaving most of the residual tumor in the vital brainstem area, requiring urgent intervention to control its growth and prevent sudden complications.

Diagnoses: Postoperative histopathological results confirmed a diagnosis of RGNT.

Interventions: The patient underwent 25 Gy/5 fractions of GKRS using the frameless Gamma Knife ICON™ (Elekta) device, as confirmed by cone-beam computed tomography scans for precise dose distribution and patient alignment.

Outcomes: GKRS was performed successfully and safely. The tumor significantly shrank 3 months post-GKRS, and the patient experienced symptom relief without any adverse effects.

Lessons: GKRS is considered an effective modality for RGNT in high-risk brainstem areas, minimizing risks while controlling tumor growth and alleviating symptoms. In addition, the frameless Gamma Knife ICON™ device enhanced patient comfort and treatment precision. GKRS offers a noninvasive alternative for similar RGNT cases.

Figure 1.

Cranial MRI findings prior to partial surgical resection. Red arrows represented the tumor, measuring approximately 45 × 31 × 52 mm. (A) Axial T1WI: lesion in the brainstem region and left thalamus observed as a heterogeneous hypointense signal. (B, C) Axial T2WI: lesion appeared hyperintense with mild surrounding edema, causing significant compression of the brainstem and narrowing of the cerebral aqueduct, leading to supratentorial ventricular enlargement and hydrocephalus. (D) Sagittal T2WI: lesion extended into the fourth ventricle and compresses the brainstem forward. (E) Axial post-contrast T1WI: a heterogeneous enhancement was seen in the lesion, suggesting active pathology. (F) Axial FLAIR imaging: a heterogeneous mixed signal was observed within the lesion, suggesting a mixture of components of the lesion. FLAIR = fluid-attenuated inversion recovery, MRI = magnetic resonance imaging, T1WI = T1-weighted imaging, T2WI = T2-weighted imaging.

Figure 2.

Cranial MRI findings after partial resection and prior to GKRS. Red arrows represented the tumor. A significant portion of the tumor remained in the brainstem and thalamic regions, resulting in compression of the brainstem. (A) Axial T1WI. (B) Axial T2WI. (C) Axial post-contrast T1WI. (D) Sagittal post-contrast T1WI. GKRS = gamma knife radiosurgery, MRI = magnetic resonance imaging, T1WI = T1-weighted imaging, T2WI = T2-weighted imaging.

Figure 3.

GKRS treatment plan and dose distribution. 25 Gy/5 fractions was performed. The green line represented the 25 Gy isodose line, while the yellow line represented the 12 Gy isodose line. Significant compression of the brainstem was observed at the treatment target, which was enclosed within the higher-dose region. The surrounding tissues, including portions of the ventricles and adjacent structures, were spared from high-dose radiation to minimize adverse effects. (A) Axial dose distribution map. (B) Coronal dose distribution map. (C) Sagittal dose distribution map. GKRS = gamma knife radiosurgery.

Figure 4.

Cranial MRI 3 months post-GKRS treatment. The lesion in the brainstem and thalamic regions was significantly reduced in size, measuring approximately 26 × 13 × 22 mm (indicated by red arrows). (A) Axial T1WI. (B) Axial T2WI. (C) Axial post-contrast T1WI: significant shrinkage of the lesion and no enhancement within the lesion. (D) Sagittal T2WI: lesion in the fourth ventricle almost disappeared, relieving compression of the brainstem. The narrowing of the cerebral aqueduct decreased, and the hydrocephalus improved. GKRS = gamma knife radiosurgery, MRI = magnetic resonance imaging, T1WI = T1-weighted imaging, T2WI = T2-weighted imaging.