FDG-PET and ASL MRI identify largely overlapping hypermetabolic and hyperperfusion changes in limbic autoimmune encephalitis.

BACKGROUND: Arterial spin labeling (ASL) MRI has been anecdotally used to assess brain perfusion in autoimmune encephalitis (AE) and its relationship with [18F]FDG-PET dysmetabolism has been scarcely investigated.Considering the physiological coupling of metabolism and perfusion, we aimed to evaluate the degree of correspondence between ASL-MRI and [18F]FDG-PET in AE. METHODS: A retrospective cohort of five patients underwent ASL-MRI and [18F]FDG-PET during the acute stage and at follow-up. We assessed the presence of regions with hypermetabolism on [18F]FDG-PET and hyperperfusion on ASL-MRI and evaluated concordance and spatial overlap of these metrics. Clinical assessment scale in AE and modified Rankin Scale were obtained at baseline and follow-up. RESULTS: In two patients [18F]FDG-PET and ASL-MRI were unremarkable; in three patients there were anatomically overlapping areas of hypermetabolism and hyperperfusion (average DICE similarity coefficient 0.358). Following immunotherapy, metabolic and perfusion changes consistently demonstrated a progressive normalization, aligning with clinical improvement. CONCLUSIONS: We identified suboptimal anatomical correspondence of abnormalities assessed with [18F]FDG-PET and ASL-MRI. Hyperperfusion and hypermetabolism might reflect differently AE-related pathophysiological correlates, but they both demonstrate ability to monitor disease activity. ASL-MRI is a promising marker of disease activity in AE and a favorable alternative to [18F]FDG-PET due to its cost-effectiveness, safety, and wide availability.

Autoimmune encephalitis: what the radiologist needs to know.

Autoimmune encephalitis is a relatively novel nosological entity characterized by an immune-mediated damage of the central nervous system. While originally described as a paraneoplastic inflammatory phenomenon affecting limbic structures, numerous instances of non-paraneoplastic pathogenesis, as well as extra-limbic involvement, have been characterized. Given the wide spectrum of insidious clinical presentations ranging from cognitive impairment to psychiatric symptoms or seizures, it is crucial to raise awareness about this disease category. In fact, an early diagnosis can be dramatically beneficial for the prognosis both to achieve an early therapeutic intervention and to detect a potential underlying malignancy. In this scenario, the radiologist can be the first to pose the hypothesis of autoimmune encephalitis and refer the patient to a comprehensive diagnostic work-up - including clinical, serological, and neurophysiological assessments.In this article, we illustrate the main radiological characteristics of autoimmune encephalitis and its subtypes, including the typical limbic presentation, the features of extra-limbic involvement, and also peculiar imaging findings. In addition, we review the most relevant alternative diagnoses that should be considered, ranging from other encephalitides to neoplasms, vascular conditions, and post-seizure alterations. Finally, we discuss the most appropriate imaging diagnostic work-up, also proposing a suggested MRI protocol.

Calcified brain metastases may be more frequent than normally considered.

OBJECTIVES: To verify the incidence of calcified brain metastases (CBM), illustrating the different presentation patterns and histology of primary tumor. METHODS: A series of 1002 consecutive brain computed tomography (CT) scans of patients with known primary tumors was retrospectively assessed. CBM were defined by the presence of calcification within intra-axial-enhancing lesions; identification of CBM was based on visual examination and ROI analysis (> 85 Hounsfield units). Also, calcifications in the primary tumor of all patients with brain metastases were evaluated. In CBM patients, we investigated the type of calcifications (punctate, nodular, cluster, ring, coarse), the histology of primary tumor, and if a previous RT was performed. RESULTS: Among 190 (18.9%) patients with brain metastatic disease, 34 presented with CBM (17.9%). Sixteen patients were previously treated with RT, while 18 presented calcifications ab initio (9.5% of all brain metastases). The majority of patients with CBM had a primitive lung adenocarcinoma (56%), followed by breast ductal invasive carcinoma (20%) and small cell lung carcinoma (11.8%). CBM were single in 44.1% of patients and multiple in 55.9%. With regard to the type of calcifications, the majority of CBM were punctate, without specific correlations between calcification type and histology of primary tumor. No patients with ab initio CBM had calcifications in primary tumor. CONCLUSION: In conclusion, our data show that CBM are more common than usually thought, showing an incidence of 9.5% ab initio in patients with brain metastases. This study underlines that neuroradiologists should not overlook intraparenchymal brain calcifications, especially in oncologic patients. KEY POINTS: • Among the differential diagnosis of brain intraparenchymal calcifications, metastases are considered uncommon and found predominantly in patients treated with radiotherapy (RT). • Our data show that CBM are more common than usually thought, showing an incidence of 9.5% ab initio in patients with brain metastases. • A proportion of intraparenchymal brain calcifications, especially in oncologic patients, might represent evolving lesions and neuroradiologists should not overlook them to avoid a delay in diagnosis and treatment.

Spatial coefficient of variation applied to arterial spin labeling MRI may contribute to predict surgical revascularization outcomes in pediatric moyamoya vasculopathy.

PURPOSE: In moyamoya vasculopathy, prolonged arterial transit time may increase the arterial spin labeling (ASL) signal heterogeneity, which can be quantitatively expressed by the spatial coefficient of variation of ASL-CBF (ASL-sCoV). The aim was to compare the accuracy of ASL-sCoV and ASL-CBF with dynamic susceptibility contrast (DSC)-CBF and time-to-peak (DSC-TTP) in the evaluation of perfusion changes and clinical outcome after encephalo-duro-arterio-myo-synangiosis (EDAMS) in pediatric moyamoya patients. METHODS: A total of 37 children with moyamoya vasculopathy (mean age 6.31 years (1.12-15.42)) underwent ASL and DSC perfusion imaging at 3T before and up to 24 months after EDAMS. Mean DSC-CBF, mean DSC-TTP, mean ASL-CBF, and ASL-sCoV were calculated in middle cerebral artery territories. Generalized linear model analyses were used to evaluate temporal variations of postoperative perfusion changes and to compare these variations between patients developing valid pial collateralization and those without angiographic improvement. Relationship between perfusion parameters and clinical outcome after surgery was tested using multivariate regression analysis. RESULTS: Significant reduction was observed after EDAMS for ASL-sCoV (P = .002; eta-squared (η2) = 0.247) and DSC-TTP (P < .001; η2 = 0.415), whereas only a trend of increase was observed for DSC-CBF and ASL-CBF, with larger discrepancy before and 6 months after surgery. At last follow-up, children developing pial collateralization showed lower absolute ASL-sCoV (P = .002 Cohen's d = 0.84) and DSC-TTP (P = .027; Cohen's d = 0.64) and higher DSC-CBF (P = .002; Cohen's d = - 0.55) compared with those without vascular improvement. Low preoperative and early post-surgical ASL-sCoV predicted better long-term neurological outcome (P < .001; ß = - 0.631). CONCLUSIONS: ASL-sCoV may contribute to predict surgical outcomes in pediatric moyamoya patients undergoing EDAMS.

Correction to: Spatial coefficient of variation applied to arterial spin labeling MRI may contribute to predict surgical revascularization outcomes in pediatric moyamoya vasculopathy.

This article was published online with incorrect alignment in Table 4. Column and rows are out of order. The correct Table 4 is presented here. The original article has been corrected.

Duplication of Intracavernous Internal Carotid Artery.

ation. No significant past medical history except for pharmacologically controlled mild hypertension. During the neurological examination the patient appeared alert, oriented and showed no deficit of strength, sensitivity and coordination. An expressive temporary aphasia was confirmed and Transient Ischemic Attacks (TIA) was suspected. Cranial Computed Tomography Angiography (CTA) showed hypoplasia of left Internal Carotid Artery (ICA) with a focal duplication in the intracavernous segment (Figure 1, arrowhead). Circle of Willis appears to be regular, with the left middle cerebral artery supported by the vertebrobasilar system through the left posterior communicating artery of increased caliber, and by the contralateral ICA via anterior communicating artery. Consequently, patient underwent Digital Subtraction Angiography (DSA) lateral view that confirmed the segmental duplication of the left intracavernous ICA (Figure 2, arrowhead). Vessels had a lightly winding course within the cavernous sinus and the intracranial branches downstream of their confluence presented a slight delay in visualization. After few hours her symptoms completely regressed and, in agreement with clinical and imaging data, diagnosis of TIA was made. The transient ischemic event was, in fact, most likely caused by low flow to the left cerebral hemisphere due to hypoplasia of the ICA and aforementioned abnormalities of its intracavernous tract that caused alteration and reduction of intracranial flow distribution. Medical treatment with anti-platelet drugs was started and patient was discharged with a clinical, laboratory and imaging follow-up program. Duplications of ICA in the intracranial tract are very rare(1,2). Most of the cases are localized in the supraclinoid segment. To our knowledge this is the first case described in literature of true duplication of ICA in the intracavernous tract. Patients with congenital variants or acquired pathology of ICA are mostly asymptomatic, but when symptoms appear, patients must be investigated(1-3). CTA is considered the first line non-invasive diagnostic method for intracranial vascular anatomy. At present, medical treatment remains the choice in patients with no-complicated duplications of ICA in the intracranial tract.

Recurrent Epistaxis of Unknown Origin: the Role of Imaging.

We report two cases of patients who presented to the Emergency Room (ER) with a history of recurrent epistaxis. Conservative treatment was provided to both patients and the most common causes of bleeding were excluded. Patients underwent radiological examinations that revealed the presence of an Intracavernous Carotid Artery Aneurysm (ICAA) extending into the sphenoid sinus through the erosion of postero-lateral bony wall. Aneurysms rupture caused massive nasal bleeding. The purpose of our case report is to illustrate as a very common symptom like epistaxis, in a small number of cases can be underestimated: rare and severe causes of nasal bleeding, as ICAA, should therefore always be considered in the differential diagnosis.

Incident anti-LGI1 autoimmune encephalitis during dementia with Lewy bodies: when Occam razor is a double-edged sword.

In Dementia with Lewy bodies (DLB), rapid cognitive decline and seizures seldom complicate the typical clinical course. Nevertheless, concurrent, treatable conditions may be responsible. We report a case of DLB with superimposed anti-LGI1 encephalitis, emphasizing the importance of thorough diagnostic reasoning beyond the simplest explanation amid distinct clinical cues.

Anti-LGI1 encephalitis and Langerhans cell histiocytosis: Two associated entities? A case report.

Autoimmune encephalitis (AE) is an immune-mediated condition that induces brain inflammation due to several neural-specific autoantibodies. The main triggering and predisposing factors are infections, genetics, the use of immune checkpoint inhibitors and tumors. We report a case of a 57-year-old male with a biopsy-confirmed Langerhans cell histiocytosis (LCH) and a concomitant anti-LGI1 encephalitis discussing a possible relationship in the pathogenesis of these phenomena. Only sporadic cases of AE developing in the context of histiocytic neoplasms have been described and there are no other reports on the relationship between LGI1-AE and LCH worldwide due to small number of cases.

Calcifications in diffuse leptomeningeal glioneuronal tumors: a case series.

Diffuse leptomeningeal glioneuronal tumor (DLGNT) is a new rare entity, typically seen in the pediatric population. Classical neuroimaging features at clinical onset include marked subarachnoid/leptomeningeal enhancement and tiny pseudo-cystic lesions along the subpial surface of the neuroaxis, frequently associated with communicating hydrocephalus. However, data on the long-term appearance of this tumor on computed tomography (CT) and magnetic resonance imaging (MRI) are still lacking. We describe a peculiar pattern of progressive leptomeningeal calcifications in three young patients with DLGNT. The calcifications, mainly located in the basal cisterns, sylvian fissures and posterior surface of the thalami, were present at clinical onset in the older subject and appeared about 2 years after clinical onset in the other two. Patients underwent different schemes of chemotherapy, variably associated with craniospinal irradiation and/or bevacizumab. In all cases, calcifications were present before starting craniospinal irradiation and/or treatment with bevacizumab. This novel peculiar pattern of progressive leptomeningeal calcifications expands the imaging phenotype of DLGNT and should be carefully sought, especially in later phases of the disease. Taking into consideration the onset, evolution, and absence of direct relationship with treatments, we hypothesize that calcifications in DLGNTs might be the effect of natural changes in the tumor and its environment.