Diffuse Leptomeningeal Glioneuronal Tumor: A Rare Clinico-radiological Masquerade
Year: 2024
Type: article
Study design: Case Report
Abstract: Sir, Diffuse leptomeningeal glioneuronal tumor (DLGNT) is a recently described entity. Due to its rarity and non-specific clinical presentation, it is often not initially suspected. Its imaging features, though scantily reported and overlapping with some other conditions, are consistent.[1] We describe a case of DLGNT who was suspected to have tuberculosis initially and Langerhans cell histiocytosis (LCH) later. Imaging-directed sequential workup finally revealed the correct diagnosis which was also confirmed pathologically. A four-year-old boy presented with seizure and hydrocephalus. Contrast-enhanced computed tomography (CECT) was conducted [Figure 1]. He was tentatively diagnosed in local hospital as tubercular meningitis, and empirical antitubercular treatment was initiated. On examination, he had mild ataxia and decreased visual acuity bilaterally. Contrast-enhanced magnetic resonance imaging (CE-MRI) of the brain [Figure 2] revealed diffuse coalescing nodular leptomeningeal lesions involving basal cisterns, along bilateral cerebral and cerebellar hemispheres and brainstem and along the visualized part of the cervical cord. Few cyst-like lesions were seen expanding the pre-pontine and perimesencephalic cisterns. Pituitary stalk, hypothalamus, choroid plexus of the left lateral ventricle, and pineal gland were involved. Susceptibility and diffusion-weighted images were unremarkable. Intracranial vessels coursing through the lesions were normal.Figure 1: Axial NCCT head. Cisernal spaces are filled with lesions showing curvilinear rim-like calcification (arrows) and few central calcifications (arrowhead).Figure 2: Initial MRI (a-d): Avidly-enhancing cisternal nodules (closed-arrows); nodular leptomeningeal enhancement along cerebral and cerebellar convexities (open-arrows), spinal cord (arrowheads); peripherally-enhancing cyst-like lesions in cisterns (asterisk) and pineal region (red). Repeat scan after two months (e-h) shows disease progressionIn view of nodular enhancing meningeal deposits, CE-MRI differential diagnosis considered was as follows: i) histiocytic group of disorders (LCH/intracranial involvement in Rosai-Dorfman disease): cystic involvement of the pineal gland and involvement of pituitary hypophysis also favored this; ii) leukemic/lymphomatous group of disorders; iii) carcinomatous meningitis (primary or secondary); and iv) neurosarcoid. Routine blood investigations, cell counts, ultrasound abdomen and chest X-ray, and skeletal survey were unremarkable. Bone marrow biopsy revealed no atypical cells and was negative for CD1a, thus ruling out histiocytosis and leukemia. Diffuse and extensive involvement of the spinal cord, more on the dorsal aspect, favored a primary meningeal pathology over drop metastasis which occur in dependent thecal areas. Pineal germinoma was less likely due to cystic involvement of the pineal gland rather than a solid-enhancing lesion typical of germinomas. A meningeal biopsy was planned, but the patient was lost to follow-up. Patient returned after 2 months with massive shunt ascites, which on cytochemical examination was due to cerebrospinal fluid (CSF) overproduction. A CE-MRI of the spine and brain conducted at this time revealed nodular pachymeningeal enhancement involving the entire spine [Figure 2g]. A slight increase in the size of leptomeningeal nodules [Figure 2h] was noted. A diagnosis of primary leptomeningeal tumor was suspected at this stage, and a possibility of DLGNT was given. A meningeal biopsy was thereafter performed from the dura over the temporal region, which confirmed the diagnosis of DLGNT, World Health Organization (WHO) grade 2. The tumor cells were positive for 1p/19q co-deletion and BRAFK1AA fusion. The patient was planned for chemotherapy as per the ICLGG-SIOP protocol. Two cycles of vincristine and carboplatin were given. His disease was, however, progressive. The parents opted for palliative care. One year post-chemotherapy, the child became vegetative with loss of vision and succumbed 6 months later. The first few cases of DLGNT were described in 2010.[2] The 2016 WHO classification of brain tumors defined it as a separate entity under the neuronal and mixed neuroglial tumors category.[3] Histologically, it consists of glial and neuronal cells which may show 1p or 1p/19q co-deletion.[1,3] Isocitrate dehydrogenase (IDH) mutations are absent, and KIAA1549-BRAF gene fusions are usually present.[4] Recent molecular profiling has further subdivided them into two subgroups of better and worse prognosis (MC-1 and MC-2), based on deoxyribonucleic acid (DNA) methylation. The most consistent imaging features reported are diffuse nodular leptomeningeal enhancement of the brain and, typically, the basal cisterns with cerebral and cerebellar sulcal spaces and anterior interhemispheric fissure involvement. Subpial and cisternal cysts, inhomogeneous T2 hyperintensity of the CSF spaces with incomplete suppression on fluid-attenuated inversion recovery (FLAIR) images, are seen indicating the presence of tumor cells filling up the CSF spaces. Supratentorial hydrocephalus is commonly present.[1,2] Also, the involvement of the entire spinal cord surface, more on its dorsal aspect, is described.[1,2] Other features include intraparenchymal soft tissue masses in the brain and spinal cord with markedly elevated choline: creatine ratios on H1 MRS. Dystrophic calcifications have been seen in areas of leptomeningeal nodular enhancement. No optimal management protocols are defined. Most patients are treated with chemotherapy according to ICLGG-SIOP 2004 recommendations. There are different reports of prognosis ranging from short-term mortality to survivals up to 12 years. We emphasize that though DLGNT is a rare condition, knowledge of its imaging features is essential to suspect this condition early as one of the diagnostic possibilities. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.
Source: Neurology India
Authors: Charu Paruthi, Rohini Gupta Ghasi, Rachna Sehgal, Amitabh Singh
Language: English
Subfield: Genetics
Field: Medicine
Domain: Health Sciences
Open Access status: hybrid
OpenAlex ID: W4405507529