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Un caso clinico di corea in paziente con iperglicemia non chetoacidosica e infezione da SARS-Cov-2

The detection of atypical and sometimes aggressive or tumefactive demyelinating lesions of the central nervous system often poses difficulties in the differential diagnosis. The clinical presentation is generally aspecific, related to the location and similar to a number of different lesions, including neoplasms and other intracranial lesions with mass effect. CSF analysis may also be inconclusive, especially for lesions presenting as a single mass at onset. As a consequence, a brain biopsy is frequently performed for characterization. Advanced MRI imaging plays an important role in directing the diagnosis, reducing the rate of unnecessary biopsies and allowing a prompt start of therapy that is often crucial, especially in the case of infratentorial lesions. In this review, the main pattern of presentation of atypical inflammatory demyelinating diseases is discussed, with particular attention on the differential diagnosis and how to adequately define the correct etiology.

Objectives: Cranial neuropathies (CNs) can be due to a wide spectrum of causes, and the differential diagnosis is particularly challenging in patients with positive history of hematological malignancies, when neoplastic meningitis (NM) must be excluded. Patients and Methods: We retrospectively selected a series of twelve haematological patients with isolated cranial neuropathies (ICNs) or multiple cranial neuropathies (MCNs). among 71 patients that developed neurologic symptoms during different stages of the cancer, between 1 January, 2010 and 31 December, 2017. Brain and cauda equina magnetic resonance imaging (MRI) with gadolinium, cerebrospinal fluid (CSF) analysis, including flow cytometry for cell immunophenotyping and microbiological exams were performed in all patients. Results: Patients developed signs and symptoms of involvement of isolated (n = 11) or multiple (n = 1) cranial nerves, at different stages of the primary disease, and, in 5 of these cases in complete remission after hematopoietic stem cell transplantation. Among the 5 cases that eventually were diagnosed as having NM, cerebrospinal fluid was positive for neoplastic cells in 3, and MRI gadolinium-enhancement was present in 3. The other episodes were attributed to heterogeneous pathologies that were unrelated to meningeal infiltration by neoplastic cells. Conclusions: Our observations confirm that NM in haematological malignancies can yield insidious isolated signs of cranial nerves. Only a multidisciplinary approach allows prompt recognition of these conditions through a challenging process of differential diagnosis, and proper therapies.

Background: Vascular lesions may be a common finding also in Alzheimer's dementia, but their role on cognitive status is uncertain. Objective: The study aims to investigate their distribution in patients with Alzheimer's, vascular or mixed dementia and detect any distinctive neuroradiological profiles. Methods: Seventy-six subjects received a diagnosis of Alzheimer’s (AD=32), vascular (VD=26) and mixed (MD=18) dementia. Three independent raters assessed the brain images acquired with an optimized 3T MRI protocol (including (3D FLAIR, T1, SWI, and 2D coronal T2 sequences) using semiquantitative scales for vascular lesions (periventricular lesions (PVL), deep white matter lesions (DWML), deep grey matter lesions (DGML), enlarged perivascular spaces (PVS), and microbleeds (MB)) and brain atrophy (medial temporal atrophy (MTA), posterior atrophy (PA), global cortical atrophy- frontal (GCA-F) and Evans’ index). Results: Raters reached a good-to-excellent agreement for all scales (ICC ranging from 0.78-0.96). A greater number of PVL (p Conclusion: The proposed MRI protocol represents a useful advancement in the diagnostic assessment of patients with cognitive impairment by more accurately detecting vascular lesions, mainly microbleeds, without a significant increase in time and resource expenditure. Our findings confirm that white and grey matter lesions predominate in vascular and mixed dementia, whereas deep and juxtacortical microbleeds predominate in mixed dementia, suggesting that cerebral amyloid angiopathy could be the main underlying pathology.

Background Fulminant inflammatory demyelination is a possible presentation of inflammatory demyelinating disorders, thus representing a potential stroke mimic especially in younger patients. Aims of the study To describe clinical and diagnostic pitfalls in a case of fulminant inflammatory demyelination presenting with stroke‐like symptoms in an elderly patient. Methods Case report and case‐based review of the literature. Results A 67‐year‐old woman, who accessed the emergency room as suspect stroke for hyperacute onset of rapidly worsening speech impairment and drowsiness, was later diagnosed with a huge brain inflammatory demyelination. Clinical, laboratory, and neuroimaging tests did not allow to put a more specific diagnosis. Due to the rapidly deteriorating course, she received immunosuppression with benefit. Conclusion This report is meant to highlight the diagnostic challenges connected with fulminant inflammatory demyelination, which sometime can resemble a stroke‐in evolution and appear clinically unfitting for inclusion in any specific pathological entities within the broad‐spectrum of inflammatory demyelinating disorders., Fulminant inflammatory demyelination represents a possible presentation of inflammatory demyelinating disorders. Here we describe a case affecting a 67 year‐old woman, who accessed the emergency room for hyperacute onset of rapidly worsening speech impairment and drowsiness. This report is meant to highlight the diagnostic challenges connected with fulminant inflammatory demyelination, which sometime can resemble a stroke‐in evolution and appear clinically unfitted for inclusion in any specific pathological entities within the broad spectrum of inflammatory demyelinating disorders.

To assess early microstructural changes of meningiomas treated with proton therapy through quantitative analysis of intravoxel incoherent motion (IVIM) and diffusion-weighted imaging (DWI) parameters. Seventeen subjects with meningiomas that were eligible for proton therapy treatment were retrospectively enrolled. Each subject underwent a magnetic resonance imaging (MRI) including DWI sequences and IVIM assessments at baseline, immediately before the 1st (t0), 10th (t10), 20th (t20), and 30th (t30) treatment fraction and at follow-up. Manual tumor contours were drawn on T2-weighted images by two expert neuroradiologists and then rigidly registered to DWI images. Median values of the apparent diffusion coefficient (ADC), true diffusion (D), pseudo-diffusion (D*), and perfusion fraction (f) were extracted at all timepoints. Statistical analysis was performed using the pairwise Wilcoxon test. Statistically significant differences from baseline to follow-up were found for ADC, D, and D* values, with a progressive increase in ADC and D in conjunction with a progressive decrease in D*. MRI during treatment showed statistically significant differences in D values between t0 and t20 (p = 0.03) and t0 and t30 (p = 0.02), and for ADC values between t0 and t20 (p = 0.04), t10 and t20 (p = 0.02), and t10 and t30 (p = 0.035). Subjects that showed a volume reduction greater than 15% of the baseline tumor size at follow-up showed early D changes, whereas ADC changes were not statistically significant. IVIM appears to be a useful tool for detecting early microstructural changes within meningiomas treated with proton therapy and may potentially be able to predict tumor response.

Meningiomas are mainly benign tumors, though a considerable proportion shows aggressive behaviors histologically consistent with atypia/anaplasia. Histopathological grading is usually assessed through invasive procedures, which is not always feasible due to the inaccessibility of the lesion or to treatment contraindications. Therefore, we propose a multi-parametric MRI assessment as a predictor of meningioma histopathological grading.Seventy-three patients with 74 histologically proven and previously treated meningiomas were retrospectively enrolled (42 WHO I, 24 WHO II, 8 WHO III) and studied with MRI including T2 TSE, FLAIR, Gradient Echo, DWI, and pre- and post-contrast T1 sequences. Lesion masks were segmented on post-contrast T1 sequences and rigidly registered to ADC maps to extract quantitative parameters from conventional DWI and intravoxel incoherent motion model assessing tumor perfusion. Two expert neuroradiologists assessed morphological features of meningiomas with semi-quantitative scores.Univariate analysis showed different distributions (p 0.05) of quantitative diffusion parameters (Wilcoxon rank-sum test) and morphological features (Pearson's chi-square; Fisher's exact test) among meningiomas grouped in low-grade (WHO I) and higher grade forms (WHO II/III); the only exception consisted of the tumor-brain interface. A multivariate logistic regression, combining all parameters showing statistical significance in the univariate analysis, allowed discrimination between the groups of meningiomas with high sensitivity (0.968) and specificity (0.925). Heterogeneous contrast enhancement and low ADC were the best independent predictors of atypia and anaplasia.Our multi-parametric MRI assessment showed high sensitivity and specificity in predicting histological grading of meningiomas. Such an assessment may be clinically useful in characterizing lesions without histological diagnosis. Key points • When surgery and biopsy are not feasible, parameters obtained from both conventional and diffusion-weighted MRI can predict atypia and anaplasia in meningiomas with high sensitivity and specificity. • Low ADC values and heterogeneous contrast enhancement are the best predictors of higher grade meningioma.

Nowadays, hadrontherapy is increasingly used for the treatment of various tumors, in particular of those resistant to conventional radiotherapy. Proton and carbon ions are characterized by physical and biological features that allow a high radiation dose to tumors, minimizing irradiation to adjacent normal tissues. For this reason, radioresistant tumors and tumors located near highly radiosensitive critical organs, such as skull base tumors, represent the best target for this kind of therapy. However, also hadrontherapy can be associated with radiation adverse effects, generally referred as acute, early-delayed and late-delayed. Among late-delayed effects, the most severe form of injury is radiation necrosis. There are various underlying mechanisms involved in the development of radiation necrosis, as well as different clinical presentations requiring specific treatments. In most cases, radiation necrosis presents as a single focal lesion, but it can be multifocal and involve a single or multiple lobes simulating brain metastasis, or it can also involve both cerebral hemispheres. In every case, radiation necrosis results always related to the extension of radiation delivery field. Multiple MRI techniques, including diffusion, perfusion imaging, and spectroscopy, are important tools for the radiologist to formulate the correct diagnosis. The aim of this paper is to illustrate the possible different radiologic patterns of radiation necrosis that can be observed in different MRI techniques in patients treated with hadrontherapy for tumors involving the skull base. The images of exemplary cases of radiation necrosis are also presented.

Background and purpose Patients with a history of brain radiotherapy can experience acute stroke-like syndromes related to the delayed effects of brain radiation, including stroke-like migraine attacks after radiation therapy syndrome, peri-ictal pseudoprogression and acute late-onset encephalopathy after radiation therapy syndrome. The aim of this study was to collect evidence on the long-term outcome and treatment of these conditions, whose knowledge is undermined by their rarity and fragmented description. Methods Cases were collected, both prospectively and retrospectively, amongst six neuro-oncology departments. Inclusion criteria were as follows: (i) history of brain radiotherapy (completed at least 6 months before the acute episode); (ii) new onset of acute/subacute neurological symptoms; (iii) exclusion of all etiologies unrelated to brain irradiation. A review of current literature on stroke-like syndromes was performed to corroborate our findings. Results Thirty-two patients with acute neurological conditions attributed to the delayed effects of radiation were identified, including 26 patients with stroke-like syndromes. Patients with stroke-like syndromes commonly presented with a mosaic of symptoms, including focal deficits (77%), encephalopathy (50%), seizures (35%) and headache (35%). Seventy-three percent of them had acute consistent magnetic resonance imaging alterations. Treatment included high-dose steroids in 65% of cases. Twenty-two patients recovered completely (85%). Sixteen patients (62%) experienced relapses (median follow-up 3.5 years). A literature review identified 87 additional stroke-like cases with similar characteristics. Conclusions Stroke-like events related to brain irradiation may be associated with permanent sequelae. Steroids are often administered on empirical grounds, as they are thought to accelerate recovery. Relapses are common, highlighting the need to elaborate adequate prevention strategies.

Cerebral amyloid angiopathy (CAA) is a cerebrovascular disorder caused by the deposition of amyloid beta-peptide (Aβ) aggregates. Aβ aggregates lead to vessel rupture and intracerebral hemorrhages, detected by magnetic resonance imaging (MRI). Presenile CAA is usually genetically determined by mutations in the amyloid precursor protein (APP) gene. However, mutations after codon 200 in the presenilin 1 (PSEN1) gene have been reported to facilitate CAA onset. Here, we analyzed the genetic bases in a patient of 55 years old affected by CAA and cognitive decline. DNA was isolated and genetic analysis was performed by Next-Generation Sequencing (NGS). RNA was extracted and retro-transcribed to perform segregation analysis by TOPO-TA cloning. WB analysis was carried out to check the impact of the mutations on protein. Two compound heterozygous mutations in PSEN1 exon 10, such as a novel stop-gain mutation (c.1070C > G) and a pathogenic splice variant (c.1129A > T), were found by NGS. Both mutations altered the presenilin 1 protein, truncating its C-terminal portion. This is the first case of CAA and cognitive decline caused by two compound mutations in PSEN1. With this report, we suggest extending the genetic analysis to PSEN1 when cerebral microbleeds are observed by MRI investigation in a patient affected by presenile cognitive decline.

BACKGROUND: beam radiotherapy (IBRT) is increasingly used for the treatment of head/neck cancers in order to spare radiosensitive structures. The occurrence of brain radiation necrosis (RN) following this modality has been reported in small case series, although its long-term outcome has not been clarified yet. The aim of this study is to define the clinical and radiological course of brain RN after IBRT, with a focus on neuropsychological (NPS) deficits and epilepsy. MATERIAL AND METHODS: Patients were prospectively identified from 07/2014 to 10/2017 during their follow-up at CNAO Foundation. Inclusion criteria were: 1) history of IBRT for a head/neck cancer; 2) age ≥18 years at the time of IBRT; 3) new MRI alterations compatible with brain RN. Enrolled patients underwent multimodal evaluations (including neurological examination, contrast brain MRI, EEG,and NPS testing), at the time of RN detection, after three months and then every six months. RESULTS: A total of 22 patients were identified. All of them had received IBRT for intracranial extraparenchymal tumors. Median age at the time of IBRT was 49 years (range 29–64). IBRT consisted of protons in 9 cases and of carbon ions in 13 cases. Median total dose was 68.8 Gy[RBE] (range 14–76.8). Six patients had been previously irradiated. Median time from the end of IBRT to RN identification was 16 months (range 3–37). In 86% of cases, RN was identified during scheduled MRI scans. RN was located in the temporal lobes in 21 cases (95%). At the time of RN detection, 71% of the patients tested had NPS deficits. Six patients developed seizures (27%). Patients were followed for a median of 23 months (range 4–41). Sixteen patients (73%) needed corticosteroid therapy and 9 (41%) were started on antiepileptic drugs. At last follow-up, 35% of patients still had multidomain NPS deficits. Within the first six months of follow-up, 74% of patients had the appearance of new enhancing lesions o enlargement of previously described lesions on MRI, though in most cases RN was reduced at last radiological follow-up. CONCLUSION: The incidence of RN peaks during the second year after IBRT. Although in most cases RN was identified during scheduled MRI scans, cognitive deficits and symptomatic epilepsy were detected in a large proportion of patients. Long-term outcome is not predictable, as some patients tend to improve over time, while others develop new symptoms. Corticosteroids and antiepileptic drugs are needed in most patients to control symptoms.

Common postictal MRI findings include transient cortical T2 hyperintensity, restricted diffusion, and gyral and/or adjacent leptomeningeal contrast enhancement. In certain uncommon pathological conditions, other signal abnormalities can be present, suggesting a different underlying pathogenic mechanism. We report the case of a 66-year-old man, recently diagnosed with diabetes mellitus type 2, presenting with new-onset visual and auditory hallucinations, "absence" seizures, and repeated peaks of hyperglycaemia without hyperketonaemia or increased serum osmolarity. EEG confirmed epileptic discharges in the right temporal region and MRI showed vast subcortical T2 hypointensity in the right temporal lobe, without any cortical hyperintensity, restricted diffusion, or contrast enhancement. Subcortical signal abnormality and EEG discharges resolved after a month of follow-up, with a small juxtacortical gliotic focus as a sequela. Peaks in hyperglycaemia have been reported to be responsible for T2 hypointense subcortical abnormalities through a proconvulsant mechanism linked to increased ketone body concentrations. Hyperosmolarity and hyperketonaemia were not evident in this case, however, transient accumulation of free radicals that alter the intercellular space can be considered the presumable cause of this finding. In summary, it is important to consider any unusual findings on postictal MRI in order to avoid errors in interpretation.

The Bing-Neel syndrome is a rare neurological complication of Waldenström’s Macroglobulinemia which results from a direct involvement of central nervous system by malignant lymphoplasmacytic cells. The clinical suspicion of Bing-Neel syndrome may be difficult because neurologic symptoms are heterogeneous, non specific and sometimes underhand. A definitive diagnosis of Bing-Neel syndrome can be confidently made using brain and spinal cord magnetic resonance imaging as well as histopathology and/or cerebrospinal fluid analysis to confirm the neoplastic infiltration of central nervous system. The detection in the cerebrospinal fluid of patients with Bing-Neel syndrome of the MYD88 (L265P) somatic mutation, which is highly recurrent in Waldenström’s Macroglobulinemia, revealed useful for the diagnosis and monitoring of central nervous system involvement. Despite recommendations recently published, there is still no clear consensus on treatment of Bing-Neel syndrome, which includes systemic immunochemotherapy, intrathecal chemotherapy and brain irradiation as possible options. Ibrutinib, a Bruton kinase inhibitor highly active in patients with Waldenström’s Macroglobulinemia, has been recently added to the therapeutic armamentarium of Bing-Neel syndrome due to its ability to pass the blood-brain barrier. However, prospective clinical trials are eagerly awaited with the aim to define the optimal treatment strategy. Here we describe four illustrative cases of Bing-Neel syndrome diagnosed and treated at our Institution and review the literature on this topic.

Neoplastic meningitis is a central nervous system complication that occurs in 3–5% of patients with cancer. Although most commonly seen in patients with disseminated disease, in a small percentage of patients, it may be the initial manifestation of cancer or even primitive in origin. In the absence of cancer history, the diagnosis of neoplastic meningitis may be challenging even for expert neurologists. Prognosis is poor, with a median overall survival of weeks from diagnosis. In the retrospective study herein, we described three cases of meningeal melanomatosis in patients without previous cancer history. The patients were diagnosed with significant delay (17 to 47 weeks from symptom onset) mainly due to the deferral in performing the appropriate testing. Even when the diagnosis was suspected, investigations by MRI, cerebrospinal fluid, or both proved at times unhelpful for confirmation. Prognosis was dismal, with a median survival of 4 weeks after diagnosis. Our observations are a cue to analyze the main pitfalls in the diagnosis of neoplastic meningitis in patients without cancer history and emphasize key elements that may facilitate early diagnosis.

INTRODUCTION: Allogeneic bone marrow transplantation (BMT) has now become a common procedure in the treatment of a variety of hematologic disorders. Neurological complications after BMT are a frequent event, including subtle relapses of hematologic malignancy and a number of pleomorphic conditions, ranging from CNS infections to cerebrovascular diseases, radiation-induced and toxic encephalopathies and acute/chronic graft versus host disease (GVHD). Diagnosis may be challenging due to the variety of disorders involved, and timeliness of treatment is crucial, as most of these complications may be life-threatening. We present our decennial experience in the field through a number of iconic cases, and propose an algorithm to guide the neurologist in the complex process of differential diagnosis. MATERIAL AND METHODS: Patients were recruited among our two institutions (Neuro-oncology/ General Neurology Unit, C. Mondino Institute, Pavia; Haematology and Transplantation Unit, Policlinico San Matteo, Pavia), and data collected retrospectively from clinical records referring to the period from January, 2010 to March, 2014. RESULTS: We selected eight patients with a history of bone marrow transplantation for different hematologic malignancies (acute lymphocytic or myeloid leukaemia and non-Hodgkin lymphomas). Neurological symptoms occurred between 1 month and 7 years after BMT, and were pleomorphic. In one patient the final diagnosis was of localization of the malignancy to the peripheral nervous system. Two patients had infectious complications: one acute limbic encephalitis by HHV-6, and one neuro-toxoplasmosis. Two other patients had autoimmune disorders of the CNS (one neuromyelitis optica and one chronic GvHD). One patient presented with PRES, and the final two with toxic encephalopathies induced respectively by radiotherapy and intrathecal chemotherapy. Complications occurred with a characteristic timing after engraftment, with PRES and limbic encephalitis being the earliest to occur and autoimmune disorders the latest. CONCLUSIONS: The timely and accurate diagnosis of neurological complications after BMT is a diagnostic challenge, that involves a multidisciplinary expert team. The definition of diagnostic algorithms could help to quicken the process of diagnosis, thus reducing the severe morbidity and mortality associated with these complications. We present our experience in the field and propose a joint prospective multicentric collection of data to address this unresolved issue.

Objectives In recent years, herpes simplex encephalitis (HSE) has been reported with increasing frequency in settings of immunosuppression, such as acquired immunodeficiency, transplantation and cancer. As observed, in immunocompromised individuals HSE presents peculiar clinical and paraclinical features, and poorer prognosis. Methods Here we describe a retrospective series of seven cases of HSE in patients with high-grade glioma (HGG), collected among three institutions in a 5-year period (during this time, a total of 1750 patients with HGG were treated). Results Diagnosis of the condition was particularly challenging due to the confounding clinical presentation and the atypical biological findings. As a result, antiviral treatment was started with a sharp delay compared with immunocompetent hosts. Prognosis was poor, with high short-term mortality and severe residual disability in survivors. Conclusions The substantial incidence of HSE observed in our centres together with the difficulty in diagnosing the condition suggest that the incidence of this complication may be highly underestimated. The aim of our report is to strengthen the observation of HSE in patients with HGG and outline the key elements that may allow its diagnosis.

Tumoral neoangiogenesis characterizes high grade gliomas. Relative Cerebral Blood Volume (rCBV), calculated with Dynamic Susceptibility Contrast (DSC) Perfusion-Weighted Imaging (PWI), allows for the estimation of vascular density over the tumor bed. The aim of the study was to characterize putative tumoral neoangiogenesis via the study of maximal rCBV with a Region of Interest (ROI) approach in three tumor areas—the contrast-enhancing area, the nonenhancing tumor, and the high perfusion area on CBV map—in patients affected by contrast-enhancing glioma (grades III and IV). Twenty-one patients were included: 15 were affected by grade IV and 6 by grade III glioma. Maximal rCBV values for each patient were averaged according to glioma grade. Although rCBV from contrast-enhancement and from nonenhancing tumor areas was higher in grade IV glioma than in grade III (5.58 and 2.68; 3.01 and 2.2, resp.), the differences were not significant. Instead, rCBV recorded in the high perfusion area on CBV map, independently of tumor compartment, was significantly higher in grade IV glioma than in grade III (7.51 versus 3.78,P=0.036). In conclusion, neoangiogenesis encompasses different tumor compartments and CBV maps appear capable of best characterizing the degree of neovascularization. Facing contrast-enhancing brain tumors, areas of high perfusion on CBV maps should be considered as the reference areas to be targeted for glioma grading.

There have been several reports of disulfiram intoxication, but little evidence of neurologic conditions resulting from disulfiram-induced brain damage combined with Wernicke encephalopathy-associated lesions. We report a rare patient with both Wernicke encephalopathy and disulfiram intoxication. This 50-year-old woman, who was taking disulfiram for chronic alcohol abuse, presented with an acute confusional state, dysarthria, nystagmus, supranuclear ophthalmoplegia, and paraparesis. Biochemical serum and cerebrospinal fluid analyses were normal. An electromyogram detected a motor polyneuropathy. Cognitive assessment revealed severe impairment of memory, attention, and logical and executive abilities. Magnetic resonance imaging with gadolinium enhancement showed brain lesions consistent with Wernicke encephalopathy, but also symmetric hyperintensities on T2-weighted images in the globus pallidus. Stopping the disulfiram and treating with hydration, high-dose thiamine supplements, and benzodiazepines significantly improved the patient's consciousness and oculomotor function. A magnetic resonance imaging scan after 1 month of treatment showed complete disappearance of the brain lesions and the hyperintensities in the globus pallidus. After a further month of intensive neurorehabilitation, the patient was able to interact with the medical staff, and her neuropsychological tests showed only mild memory impairment. Patients with alcoholism who present at emergency departments are at high risk for misdiagnosis, especially because there is no specific routine laboratory test for detecting asymptomatic disulfiram intoxication. Although uncommon, the combination of Wernicke encephalopathy and disulfiram intoxication should be suspected in patients with alcoholism. The disorder can be detected through a careful history and prompt clinical evaluation, together with characteristic magnetic resonance imaging findings.

Transient global amnesia (TGA) is an episodic dysfunction of declarative memory that usually resolves within 12 hours and whose underlying pathophysiological mechanisms are still unclear. Recent studies, on the basis of transient focal high-signal abnormalities in the hippocampus on diffusion-weighted imaging (DWI), suggest involvement of memory circuits in the temporo-mesial region. Out of a total of 65 patients presenting with acute or subacute TGA between May 2004 and May 2008, we retrospectively analysed 21 in whom a DWI sequence was performed. Five patients showed a focal hippocampal signal alteration both on DWI and on conventional T2; this alteration was no longer detectable on follow-up MRI two months later. The presence of transient DWI and T2 alterations in the hippocampal formation suggests that TGA could have a multifactorial, non-vascular aetiology. The presence of local susceptibility to neuronal metabolic stress emerges as a likely hypothesis.