Primary glioblastoma multiform (GBM) of the optic nerve and chiasma: A case report and systematic review of the literature.

Key Clinical Message: Primary GBM of the optic nerve and chiasma should be included in the differential diagnosis of progressive lesions despite initial treatment; clinicians should avoid delay in confirming the histology to initiate proper treatment and improve prognosis. Abstract: Primary GBM of the optic nerve or chiasma is very rare. The characteristics of this condition have not been well-described, which poses difficulties in establishing the correct diagnosis, affecting the treatment and the prognosis. We present a case of GBM of the optic chiasma diagnosed through an open biopsy at our centre. Following the PRISMA statement, we also conducted a systematic review after protocol registration in PROSPERO (CRD42021285855). We searched Medline and Embase through Ovid from inception until December 31, 2021. Two reviewers independently screened the studies. Studies were eligible for inclusion if they reported cases of primary GBM confined to the optic nerve or chiasma as the initial radiological diagnosis. A 77-year-old female was referred for progressive visual loss lasting 8 weeks. MRI revealed a suspected lesion in the left chiasma. The patient's vision deteriorated further despite initially diagnosing an inflammatory process and empirical treatment with corticosteroids. Subsequently, the patient underwent an open biopsy and surgical debulking. Histology, including epigenetic analysis, confirmed GBM grade IV. Radiochemotherapy was administered. The patient died 19 months after surgery. We identified 45 similar cases (22 female) reported in 35 studies between 1949 and 2020. The mean age of the cases was 61 (SD = 14.6). Most cases were misdiagnosed and mistreated accordingly, so there was a median delay of 8 weeks (IQR: 5-14 weeks) in obtaining histological confirmation of the diagnosis, delaying the initiation of appropriate treatment. Five cases became no treatment since the patients died shortly after the delayed histologic diagnosis. The Kaplan-Meier estimate indicated that most patients died within 20 months of presentation, with a 1-year survival rate of 50%, and untreated cases had very low survival rates compared to treated cases. Primary GBM of the optic nerve and chiasma is a rare condition primarily affecting adults. The rarity of this condition contributes to initial misdiagnosis, mistreatment, and delays in confirming the histology and initiating appropriate treatment. The prognosis remains poor, but treatment, including surgery and radiochemotherapy, improves survival.