Relapsing demyelinating syndromes (RDS) in children encompass a diverse spectrum of entities including multiple sclerosis (MS) acute disseminated encephalomyelitis (ADEM), aquaporin-4 antibody ...associated neuromyelitis optica spectrum disorder (AQP4-NMOSD) and myelin oligodendrocyte glycoprotein antibody disease (MOG-AD). In addition to these, there are “antibody-negative” demyelinating syndromes which are yet to be fully characterized and defined. The paucity of specific biomarkers and overlap in clinical presentations makes the distinction between these disease entities difficult at initial presentation and, as such, there is a heavy reliance on magnetic resonance imaging (MRI) findings to satisfy the criteria for treatment initiation and optimization. Misdiagnosis is not uncommon and is usually related to the inaccurate application of criteria or failure to identify potential clinical and radiological mimics. It is also notable that there are instances where AQP4 and MOG antibody testing may be falsely negative during initial clinical episodes, further complicating the issue. This article illustrates the typical clinico-radiological phenotypes associated with the known pediatric RDS at presentation and describes the neuroimaging mimics of these using a pattern-based approach in the brain, optic nerves, and spinal cord. Practical guidance on key distinguishing features in the form of clinical and radiological red flags are incorporated. A subsection on clinical mimics with characteristic imaging patterns that assist in establishing alternative diagnoses is also included.
The central nervous system (CNS) undergoes constant immune surveillance enabled via regionally specialized mechanisms. These include selectively permissive barriers and modifications to interlinked ...innate and adaptive immune systems that detect and remove an inciting trigger. The end-points of brain injury and edema from these triggers are varied but often follow recognizable patterns due to shared underlying immune drivers. Imaging provides insights to understanding these patterns that often arise from unique interplays of infection, inflammation and genetics. We review the current updates in our understanding of these intersections and through examples of cases from our practice, highlight that infection and inflammation follow diverse yet convergent mechanisms that can challenge the CNS in children.
Purpose
T2-FLAIR mismatch serves as a highly specific but insensitive marker for IDH-mutant (IDHm) astrocytoma with potential limitations in real-world application. We aimed to assess the utility of ...a broader definition of T2-FLAIR discordance across a cohort of adult-type diffuse lower-grade gliomas (LrGG) to see if specific patterns emerge and additionally examine factors determining deviation from the classic T2-FLAIR mismatch sign.
Methods
Preoperative MRIs of non-enhancing adult-type diffuse LrGGs were reviewed. Relevant demographic, molecular, and MRI data were compared across tumor subgroups.
Results
Eighty cases satisfied the inclusion criteria. Highest discordance prevalence and > 50% T2-FLAIR discordance volume were noted with IDHm astrocytomas (
P
< 0.001), while < 25% discordance volume was associated with oligodendrogliomas (
P
= 0.03) and IDH-wildtype (IDHw) LrGG (
P
= 0.004). “T2-FLAIR matched pattern” was associated with IDHw LrGG (
P
< 0.001) and small or minimal areas of discordance with oligodendrogliomas (
P
= 0.03). Sensitivity and specificity of classic mismatch sign for IDHm astrocytoma were 25.7% and 100%, respectively (
P
= 0.06). Retained ATRX expression and/or non-canonical IDH mutation (
n
= 10) emerged as a significant factor associated with absence of classic T2-FLAIR mismatch sign in IDHm astrocytomas (100%,
P
= 0.02) and instead had minimal discordance or matched pattern (40%,
P
= 0.04).
Conclusion
T2-FLAIR discordance patterns in adult-type diffuse LrGGs exist on a diverging but distinct spectrum of classic mismatch to T2-FLAIR matched patterns. Specific molecular markers may play a role in deviations from classic mismatch sign.
Hypomyelinating Leukodystrophies (HLDs) are a genetically heterogeneous, clinically overlapping group of disorders with the unifying MR imaging appearance of myelin deficit in the brain. In fact, it ...is the MRI phenotype that typically raises the diagnostic suspicion in this single largest group of undiagnosed leukodystrophies and guides gene testing for confirmation. This article reviews the neurobiology of myelination, focussing on the complex interplay of molecular genetic pathways and presents a practical clinico-radiological diagnostic algorithm based on the neuroimaging patterns of the common hypomyelinating disorders. The authors also address the current controversies about the definition and use of the term ‘hypomyelination’.
•Hypomyelination is a commonly encountered MR imaging phenotype in Paediatric Neurology practice.•Many clinically and genetically diverse group of disorders share the hypomyelination phenotype on imaging. It is imperative to differentiate primary delayed myelination and demyelination from this entity.•Clinical clues, pattern recognition and recognition of other associated imaging findings can help narrow these differential diagnoses and guide the diagnostic process.•Our understanding of normal myelination and disorders affecting it is still evolving. This leads to semantic confusions and diagnostic conundrums around hypomyelinating disorders. Accurate description of imaging features and reverse phenotyping after genetic diagnosis are possible practical solutions.
Purpose
Basal duct-like recess (DR) sign serves as a specific marker of papillary craniopharyngiomas (PCPs) of the strictly third-ventricular (3 V) topography. Origins of this sign are poorly ...understood with limited validation in external cohorts.
Methods
In this retrospective study, MRIs of pathologically proven PCPs were reviewed and evaluated for tumor topography, DR sign prevalence, and morphological subtypes.
Results
Twenty-three cases with 24 MRIs satisfied our inclusion criteria. Median age was 44.5 years with a predominant male distribution (M/F ratio 4.7:1). Overall, strictly 3 V was the commonest tumor topography (8/24, 33.3%), and tumors were most commonly solid-cystic (10/24, 41.7%). The prevalence of DR sign was 21.7% (5/23 cases), all with strictly 3 V topography and with a predominantly solid consistency. The sensitivity, specificity and positive and negative predictive value of the DR sign for strict 3 V topography was 62.5%, 100%, 100% and 84.2% respectively. New pertinent findings associated with the DR sign were observed in our cohort. This included development of the cleft-like variant of DR sign after a 9-year follow-up initially absent at baseline imaging. Additionally, cystic dilatation of the basal tumor cleft at the pituitary stalk-tumor junction and presence of a vascular structure overlapping the DR sign were noted. Relevant mechanisms, hypotheses, and implications were explored.
Conclusion
We confirm the DR sign as a highly specific marker of the strictly 3 V topography in PCPs. While embryological and molecular factors remain pertinent in understanding origins of the DR sign, non-embryological mechanisms may play a role in development of the cleft-like variant.
PDF
