Diffuse Leptomeningeal Glioneuronal Tumor (DLGNT) With Direct Cystic Infiltration of the Optic Chiasm and Tracts

Diffuse leptomeningeal glioneuronal tumor (DLGNT) is a rare pediatric neoplasm categorized by the WHO in 2016 (1, 2). It is characterized by communicating hydrocephalus, slow tumor growth, CSF with absence of tumor cells, and MRI showing diffuse leptomeningeal enhancement and cystic changes (3). Here we present, to our knowledge, the first case in which direct cystic tumor infiltration of the optic apparatus was the initial manifestation.

Poster 199 Diffuse Leptomeningeal Glioneuronal Tumor (DLGNT) with Direct Cystic Infiltration of the Optic Chiasm and Tracts John Paddock1, Daniel Elefant1, Sara Kingston2, David Pisapia1, Linda Heier1, Cristiano Oliveira1, Marc Dinkin1 1 Weill Cornell Medicine, New York, New York, USA, 2NewYork-Presbyterian Hospital, New York, New York, USA Introduction: Diffuse leptomeningeal glioneuronal tumor (DLGNT) is a rare pediatric neoplasm categorized by the WHO in 2016 (1, 2). It is characterized by communicating hydrocephalus, slow tumor growth, CSF with absence of tumor cells, and MRI showing diffuse leptomeningeal enhancement and cystic changes (3). Here we present, to our knowledge, the first case in which direct cystic tumor infiltration of the optic apparatus was the initial manifestation. Description of Case(s): A 3-year-old boy developed emesis, altered mental status, bilateral leg weakness, and decreased visual acuity to 20/125 OD and 20/160 OS. MRI showed hydrocephalus and diffuse leptomeningeal enhancement of the brain and spine. Lumbar puncture showed pleocytosis, elevated protein, positive enterovirus PCR, and opening pressure of 55 cm H2O. VP shunt was placed for presumed enterovirus meningitis. Symptoms of hydrocephalus resolved but vision did not improve. Exam showed optic disc pallor bilaterally and no papilledema. OCT demonstrated retinal nerve fiber layer thinning bilaterally. Visual decline progressed despite normalization of ICP. Repeat MRI brain/orbits showed multiple new subpial cysts along the optic tracts and optic chiasm. Filum biopsy showed rare inflammatory cell. Review of the pathology and radiological findings led to a consensus of DLGNT with cysts compressing and infiltrating optic chiasm and nerves. The patient was started on the MEK inhibitor trametinib, with stabilization of MRI findings and vision, but unfortunately without visual improvement. Conclusions, including unique features of the case(s): Pathologic confirmation of DLGNT can be difficult as safely obtained biopsy samples are typically small (4). In this case, bilateral optic neuropathy developed due to infiltration of the optic nerves, chiasm and tracts, while papilledema was never seen. MEK inhibitor therapy was initiated with stable disease (5). This diagnosis should be considered in pediatric patients with communicating hydrocephalus, diffuse leptomeningeal enhancement, and elevated CSF protein with otherwise normal profile including absence of tumor cells. References: Lee. A case of diffuse leptomeningeal glioneuronal tumor misdiagnosed as chronic tuberculous meningitis without brain biopsy. Case Rep Neurol Med. 2018;2018:1391943. Lyle. Newly identified characteristics and suggestions for diagnosis and treatment of diffuse leptomeningeal glioneuronal/neuroepithelial tumors: a case report and review of the literature. Child Neurol Open. 2015;2:2329048X14567531. Smith. Primary Diffuse Leptomeningeal Glioneuronal Tumor Presenting as Bilateral Vision Loss, Journal of Neuro-Ophthalmology: August 4, 2021. Abongwa. Primary diffuse leptomeningeal glioneuronal tumors of the central nervous system: report of three cases and review of literature. Pediatr Hematol Oncol. 2020;37:248–258. Perreault. A phase 2 study of Trametinib for patients with pediatric glioma with activation of the MAPK/ERK pathway TTRAM-01. US: Oxford University Press. Neuro-oncology (Charlottesville, Va.), Vol.22 (Suppl 3), p.iii371-iii371. Keywords: optic neuropathy, pediatric neuro-ophthalmology, tumors, high intracranial pressure/headache Financial Disclosures: The authors had no disclosures. Grant Support: None. Contact Information: Marc Dinkin, [e-mail] 2022 Annual Meeting Syllabus | 261