Posterior fossa abnormalities are among the most complex and diagnostically challenging findings on foetal MRI. They encompass a wide spectrum of malformations of the cerebellum, brainstem, and fourth ventricle, with variable prognostic implications. Accurate prenatal characterisation is essential for counselling parents, genetic testing and perinatal planning. In this poster we aim to provide a structured, reproducible framework for evaluating foetal posterior fossa abnormalities. A total of 1,400 foetal brain MRI examinations performed over eight years at a tertiary referral centre have been reviewed, identifying all cases with posterior fossa abnormalities. Images were analysed for vermian morphology, cerebellar hemispheric development, fourth ventricular configuration, brainstem integrity, and associated syndromic features. Posterior fossa abnormalities were stratified into five categories: Cerebellar vermis and fourth ventricle malformations, including the recent insights into Dandy–Walker spectrum, Blake’s pouch cyst, isolated vermian hypoplasia, and mega cisterna magna; Cerebellar hemispheric anomalies, such as unilateral/bilateral hypoplasia and cerebellar dysplasia as well as rhombencephalosynapsis; Midbrain–hindbrain junction disorders, including Joubert syndrome and related disorders, and pontocerebellar hypoplasia; Cystic or acquired lesions, including arachnoid cysts and post-ischemic/post-hemorrhagic cystic changes; Syndromic or complex malformations, including Walker–Warburg spectrum and tubulinopathies. The poster highlights refined Dandy–Walker criteria, including inferior-predominant vermian hypoplasia, enlarged tegmentovermian and fastigial recess angles, and inferolateral displacement of the tela choroidea and choroid plexus, distinguishing it from Blake’s pouch cyst and mega cisterna magna. This review illustrates the full spectrum of fetal posterior fossa abnormalities. Annotated MRI cases, schematic diagrams, and a stepwise diagnostic algorithm are provided to enhance interpretative accuracy, reporting consistency, and prenatal counselling. Read More

Meeting name: SPR 2026 Annual Meeting , 2026

Authors: Prasher Sparsh, Maniyar Amit, Wigmore Edward, Harris Debra

Keywords: Fetal Brain MRI, Fetal Magnetic Resonance Imaging, Posterior Fossa

Encephalopathy is a well-recognised complication of intrathecal methotrexate in paediatric acute lymphoblastic leukaemia (ALL), often presenting with seizures, altered consciousness, and motor deficits that typically resolve spontaneously within 24–48 hours. In contrast, methotrexate-induced myelopathy is a far rarer and under-recognised entity, with the potential for lasting neurological sequelae if not diagnosed and treated promptly. We present an unusual case of methotrexate-induced myelopathy in a child with ALL, featuring an atypical clinical presentation and novel MRI findings that expand the recognised radiological phenotype. A 4-year-old boy in remission from low-risk B-cell ALL (without CNS involvement) received intrathecal and intravenous methotrexate via an atraumatic lumbar puncture. Within hours, he developed left-sided hemiparesis, progressing to quadriparesis, with predominant weakness on the left and brief truncal involvement. He remained afebrile and haemodynamically stable, and laboratory tests, CSF analysis, and methotrexate clearance were all unremarkable. Brain imaging (CT, MRI, MRA) was normal. However, spinal MRI revealed extensive T2 hyperintensity throughout the cervical, thoracic, and lumbar spinal cord, involving both grey and white matter — a pattern more reminiscent of transverse myelitis than classic methotrexate myelopathy. CSF cytology was negative for malignant cells, and autoimmune and infectious screens, including MOG and AQP4 antibodies, were negative. Treatment with high-dose corticosteroids, folinic acid rescue, and IVIG was initiated within 12 hours of symptom onset. The patient showed marked improvement and was discharged ambulant after six weeks, with only mild residual left-sided weakness. Classic methotrexate myelopathy typically affects the dorsal columns in a caudal-to-rostral progression. In contrast, this case demonstrated diffuse longitudinal cord involvement with mixed grey and white matter changes. Such imaging findings are not widely reported. Histopathological studies in similar cases support a mechanism of superficial demyelination from CSF-contact toxicity, aligning with this radiological presentation. This case expands the radiological spectrum of methotrexate-induced myelopathy. Recognition of atypical spinal imaging findings is critical for timely diagnosis and early immunomodulatory treatment, which can significantly improve neurological outcomes. Read More

Meeting name: SPR 2026 Annual Meeting , 2026

Authors: Prasher Sparsh, Wigmore Edward, Surana Snehal, Vraka Katerina, Bonney Denise

Keywords: ALL, Spinal Cord, Pediatric Neuroradiology