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The glycosylphosphatidylinositol (GPI) is a glycol-lipid that anchors several proteins to the cell surface. The GPI-anchor pathway is crucial for the correct function of proteins involved in cell function, and it is fundamental in early neurogenesis and neural development. The PIG gene family is a group of genes involved in this pathway with six genes identified so far, and defects in these genes are associated with a rare inborn metabolic disorder manifesting with a spectrum of clinical phenotypes in newborns and children. Among them, the PIGO gene encodes for phosphatidylinositol glycan anchor biosynthesis class O protein (PIGO), an enzyme participating in this cascade, and the loss of its function often leads to a severe clinical picture characterized by global developmental delay, seizures, Hirschsprung disease, and other congenital malformations. To date, 19 patients with confirmed PIGO deficiency have been described in the literature with a host of clinical and radiological manifestations. We report a case of a male term newborn with two compound heterozygous variants of the PIGO genes, presenting with encephalopathy, drug-resistant epilepsy, and gastrointestinal abnormalities. Brain MRI first showed diffusion restriction in the ponto-medullary tegmentum, ventral mesencephalon, superior cerebellar peduncles, cerebral peduncles, and globi pallidi. This pattern of lesion distribution has been described as part of the neuroradiological spectrum of PIG genes-related disorders. However, after one month of life, he also showed a previously undescribed MRI pattern characterized by extensive cortical and subcortical involvement of the brain hemispheres. The presence of two different mutations in both the PIGO genes may have been responsible for the particularly severe clinical picture and worse outcome, leading to the death of the newborn in the sixth month of life despite therapeutic attempts. This case expands the neuroradiological spectrum and may bring new insights on glycosylation-related disorders brain manifestations.

Bacterial meningoencephalitis in newborns is a severe and life-threatening pathology, which results from meningeal infection and the subsequent involvement of the brain parenchyma. The severity of the acute onset of symptoms and the risk of neurodevelopmental adverse sequelae in children strongly depend on the timing of the infection, the immunological protection transmitted by the mother to the fetus during pregnancy, and the neonate's inflammatory and immune system response after birth. Although the incidence of neonatal meningitis and meningoencephalitis and related mortality declined in the past twenty years with the improvement of prenatal care and with the introduction of intrapartum antibiotic prophylaxis against Streptococcus beta Hemolyticus group B (Streptococcus Agalactiae) in the 1990s, bacterial meningitis remains the most common form of cerebrospinal fluid infection in pediatric patients. To date, the rate of unfavorable neurological outcomes is still from 20% to 60%, and the possibility of containing its rate strongly depends on early diagnosis, therapy, and a multidisciplinary approach, which involves neonatologists, neurologists, neuroradiologists, and physiotherapists. Neonatal meningitis remains difficult to diagnose because the responsible bacteria vary with gestational age at birth, age at presentation, and environmental context. The clinical presentation, especially in the newborn, is very ambiguous. From a clinical point of view, the definitive test for diagnosis is lumbar puncture in patients with symptoms suggestive of neurological involvement. Therefore, neuroimaging is key for raising clinical suspicion of meningitis or corroborating the diagnosis based on clinical and laboratory data. Our pictorial review offers a practical approach to neonatal meningoencephalitis by describing the epidemiology, the pathophysiology of bacterial meningoencephalitis, defining the indications and suggesting optimized protocols for neuroimaging techniques, and showing the main neuroimaging findings to reach the diagnosis and offering proper follow-up of bacterial meningitis. Moreover, we tried identifying some peculiar MRI patterns related to some bacteria.