The number of pediatric patients with COVID-19 has increased rapidly since the omicron variant became the main cause of the disease. By November 2022, 103 cases of COVID-19-related acute encephalopathy had been reported. Acute encephalopathy with biphasic seizures and late reduced diffusion (AESD) was the most common syndrome (27 cases, 26.2%). There were 8 cases of hemorrhagic shock and encephalopathy syndrome (HSES), 6 cases of encephalopathy with acute fulminant cerebral edema (AFCE), and 4 cases of acute necrotizing encephalopathy (ANE); thus, in total, there were 18 cases (17.5%) of cytokine storm encephalopathy. The frequencies were higher than those reported in 2017 for ANE (2.8%) and HSES (1.7%), before COVID-19. The prognosis of COVID-19-related acute encephalopathy was poor (11 deaths, 10.7%) due to the high frequencies of HSES and AFCE, which have a severe course.

Radiographs followed by magnetic resonance imaging (MRI) are the first-choice modality for pediatric osteomyelitis imaging. Imaging aims to diagnose the presence and extent of osteomyelitis, assess the need for debridement of abscesses, evaluate risk factors, such as lesions extending the growth plate that may lead to growth disturbances, and determine the presence of complications, such as thrombosis and ischemia. It is essential to understand the anatomical and physiological characteristics of developing bones and tailor MRI protocols according to age. Key points in image interpretation include the differences between acute bacterial osteomyelitis, such as that caused by staphylococcus, and osteomyelitis caused by low-virulence bacteria, such as mycobacterium, as well as imaging features of subacute and chronic osteomyelitis. Growth disturbances as late complications are a significant concern in pediatric osteomyelitis, highlighting the need for an accurate early diagnosis.

Influenza encephalopathy encompasses a wide range of syndromes. The conditions presumed to be involved in its pathogenesis include metabolic derangement, the systemic inflammatory response, and excitotoxicity. Imaging findings are important for the diagnosis of influenza encephalopathy. Acute necrotizing encephalopathy is characterized by bilateral thalamic lesions. Acute encephalopathy with biphasic seizures and late reduced diffusion is characterized by reduced diffusion in the subcortical white matter (bright tree appearance). Clinically, mild encephalitis/encephalopathy with a reversible splenial lesion is characterized by reduced diffusion in the splenium of the corpus callosum and it may be associated with symmetrical lesions in the deep white matter. Hemorrhagic shock and encephalopathy syndrome are characterized by rapidly progressing, extensive cerebral edema. Acute fulminant cerebral edema is a recently proposed disease entity, and its imaging findings are not yet well established. Although each imaging finding is characteristic, a comprehensive diagnosis, which includes the evaluation of clinical symptoms and other factors, should always be made.

Congenital infections generally include infections that occur in utero or perinatally. As part of TORCH syndrome, these infections include congenital toxoplasmosis, congenital rubella syndrome, congenital cytomegalovirus infection, neonatal herpes simplex virus encephalitis, congenital HIV infection, and hepatitis virus congenital infections. Lymphocytic choriomeningitis virus and Zika virus can also cause intrauterine infections, while central nervous system damage due to human parechovirus type 3 and Group B streptococcus can occur in perinatal infections. Intrauterine infections present different symptoms and imaging findings depending on the timing of fetal infection, with earlier infections being more severe. Common imaging findings include ventricular enlargement and intracerebral calcifications, but the etiology of ventricular enlargement (i.e., whether due to hydrocephalus or brain volume reduction) and the location of intracerebral calcifications vary by disease. Rapid diagnosis and treatment are crucial for perinatal infections. Definitive diagnosis involves detecting the causative pathogen in cerebrospinal fluid or blood, but obtaining these results can take time. Imaging diagnostics provide indirect evidence for early diagnosis, with MRI, especially diffusion-weighted imaging, being particularly useful.

Congenital cytomegalovirus (CMV) infection is the most common type of TORCH syndrome, and it is estimated to occur at a frequency of 1 in 300 newborns. For symptomatic infants, the administration of valganciclovir within the first 2 months of life is effective. Treatment initiation should be considered for symptomatic infections, and abnormalities, such as intracranial calcifications or white matter lesions, which are observed on head imaging. The imaging findings vary depending on the timing of the infection, and some findings have been associated with the neurological prognosis and a risk of hearing loss. This article provides an overview of the clinical aspects of congenital CMV infection, including the imaging findings, and the differential diagnosis.

In children presenting with pulmonary tuberculosis, the proportion of those presenting with primary tuberculosis is high, and these findings often cannot be identified on chest radiography. This disease is characterized by swollen lymph nodes in the hilum and mediastinum. As a result, if tuberculosis is suspected in children, then aggressive contrast-enhanced chest CT is required. In infants, careful attention should be paid to potential complications of miliary tuberculosis and tuberculous meningitis, and a thorough search for these is particularly necessary when swelling of the mediastinal lymph nodes is observed. Head CT and MRI in patients with tuberculous meningitis are necessary to determine the presence of cerebral infarction in the middle cerebral artery region and communicating hydrocephalus. Congenital tuberculosis is a type of tuberculosis that is unique to newborns, and in cases where the mother has undiagnosed genital tuberculosis, a definitive diagnosis often takes a long time to be made because the images often resemble those of aspiration pneumonia.

Horseshoe lung is a very rare congenital respiratory and vascular malformation characterized by fusion of the bases of the bilateral lungs across the middle mediastinum. It is commonly associated with cardiovascular malformations, such as Scimitar syndrome. Young patients with horseshoe lung may develop recurrent pneumonia and pulmonary hypertension, which can sometimes be fatal. However, if symptoms are not clinically severe, follow-up alone may be appropriate. We report a case of horseshoe lung with suspected intralobar sequestration revealed by preoperative computed tomography. There are only a few reported cases of horseshoe lung and they present with a wide variety of findings. Diagnosis of this congenital malformation requires attention to arteriovenous and bronchial findings, as well as to the lungs.

Kallmann syndrome is a genetic disease that combines hypogonadotropic hypogonadism and olfactory abnormality, with various accompanying symptoms depending on the genetic type. The patient in this case was a 3-year-old boy. At a health checkup at 1.5 years old, poor eye contact was noted, which led to strabismus, left eyelid ptosis, and left amblyopia. A head MRI scan incidentally revealed the absence of the olfactory bulb, olfactory sulcus, and olfactory tract. Kallmann syndrome was suspected. Subsequent examination revealed low gonadotropin levels and a pathogenic variant of the ANOS1 (KAL1) gene, leading to a definitive diagnosis of Kallmann syndrome. Abdominal MRI and renal scintigraphy revealed that the patient had a single right kidney. Kallmann syndrome is often diagnosed with delayed onset of puberty, but due to the various accompanying symptoms, it may be possible to make an early diagnosis based on symptoms such as ptosis, amblyopia, and renal hypoplasia. In addition, the absence of the olfactory bulb, olfactory groove, and olfactory tract on head MRI is a characteristic finding of Kallmann syndrome and is useful for diagnosis.

Rubinstein-Taybi syndrome is a congenital anomaly syndrome characterized by various features such as mental and motor developmental delay, broad thumbs, and large-sized toes. Reports on patients typically focus on growth and physical examination findings, however, reports on the common characteristics of head MRI findings are limited. We herein report the case of a male infant with diverse and characteristic midline structural brain abnormalities which were identified in the early postnal period.

The patient was born at 38 weeks and 2 days gestation, with a birth weight of 1,954 g. The infant exhibited distinctive facial features, broad bilateral great toes, and the misalignment of the toes from birth. Magnetic resonance imaging of the head revealed hypoplasia of the corpus callosum, persistent falcine sinus, sinus pericranii, and pituitary hypoplasia. The presence of a persistent falcine sinus and sinus pericranii may be related to other midline structural brain abnormalities. While the diagnosis of Rubinstein-Taybi syndrome is typically based on the clinical features and findings of genetic examinations, accumulating knowledge of radiological abnormalities may also contribute to making an earlier diagnosis in the future.

The patient was an 11-month-old boy and a first-born twin. The second-born twin was breastfed, whereas the first-born twin was fed baby formula. Unlike second-born twins, first-born twins sometimes have developmental delays of unknown cause. The patient was emergently transported to our hospital after experiencing a sudden impaired consciousness while his mother was attending to her children by herself. Upon arrival, the patient’s Glasgow Coma Scale was E1V2M1, but head MRI showed no obvious abnormalities. However, frequent convulsions began on the third day, and on the sixth day, head MRI revealed an acute subdural hematoma, and diffusion-weighted imaging showed a bright tree appearance in the bilateral temporo-occipital lobes. An ophthalmological examination revealed a retinal hemorrhage. The patient had an infantile head injury with a biphasic clinical course and late reduced diffusion because of how he was being nurtured and the presence of a retinal hemorrhage based on the findings of an ophthalmologic examination. Steroid pulse therapy was administered, and the patient recovered clinically to their pre-illness condition. However, brain MRI on the 33rd day of hospitalization revealed polycystic changes.