Incidental IDH1 Mutant Low-grade Astrocytoma Mimicking TBI Later Transforming into Aggressive Glioblastoma: Diagnostic and Serial Surgical Challenges in Gliomas

Abstract

Low grade gliomas have better outcomes following intervention compared to high grade gliomas including glioblastomas. About 14.4% of diffuse astrocytoma (WHO II) transform and progress into high grade malignant subtypes. Early diagnosis and intervention can therefore warrant halted transformation and progression and prolong survival with improved quality of life. However, asymptomatic low-grade astrocytoma lesions are difficult to diagnose, ascertain, and differentiate from other non-enhancing lesions including brain contusion. We report a case of grade II astrocytoma that was missed for three years on incidental intra-cranial imaging following two incidences of trauma. A 30-year-old female was involved in motor traffic crash and lost consciousness for less than 20 minutes, with no other neurological complaints or deficits. CT and follow up MR imaging revealed a low density, non-enhancing left frontal lesion that was thought to be non- hemorrhagic cerebral contusion sequela. Brain imaging done three years later following another accident showed the initial lesion had significantly increased in size. Astrocytoma was then suspected, and the patient underwent tumor resection with histological diagnosis of diffuse astrocytoma. There was tumor recurrence after two years with features of malignancy. Secondary resection was done with immunohistochemical and genetic analysis revealing an Isocitrate Dehydrogenase 1 (IDH1) Mutant Glioblastoma (WHO IV). Along the course of the surgical and medical interventions, the patient again underwent an additional third surgical intervention with autografting dura repair following cerebrospinal fluid effusion through the previously repaired dura. High index of suspicion is paramount for early diagnosis and intervention of asymptomatic low-grade gliomas. Along with the known hypothesis that traumatic brain injury can induce malignant transformation in the astrocytic cells, incidental findings that are synchronous with events such as trauma can also mask-off already occurring malignant changes that would otherwise require advanced diagnostic skills, experience, and techniques including structural and functional imaging.