Diffusion-weighted MRI for early diagnosis of neonatal herpes simplex encephalitis

Understanding the impact of congenital infections and perinatal viral exposures on the developing brain using white matter magnetic resonance imaging: a scoping review

BACKGROUND

Magnetic Resonance Imaging (MRI)-based imaging techniques are useful for assessing white matter (WM) structural and microstructural integrity in the context of infection and inflammation. The purpose of this scoping review was to assess the range of work on the use of WM neuroimaging approaches to understand the impact of congenital and perinatal viral infections or exposures on the developing brain.

METHODS

This scoping review was conducted according to the Arksey and O' Malley framework. A literature search was performed in Web of Science, Scopus and PubMed for primary research articles published from database conception up to January 2022. Studies evaluating the use of MRI-based WM imaging techniques in congenital and perinatal viral infections or exposures were included. Results were grouped by age and infection.

RESULTS

A total of 826 articles were identified for screening and 28 final articles were included. Congenital and perinatal infections represented in the included studies were cytomegalovirus (CMV) infection (n = 12), human immunodeficiency virus (HIV) infection (n = 11) or exposure (n = 2) or combined (n = 2), and herpes simplex virus (HSV) infection (n = 1). The represented MRI-based WM imaging methods included structural MRI and diffusion-weighted and diffusion tensor MRI (DWI/ DTI). Regions with the most frequently reported diffusion metric group differences included the cerebellar region, corticospinal tract and association fibre WM tracts in both children with HIV infection and children who are HIV-exposed uninfected. In qualitative imaging studies, WM hyperintensities were the most frequently reported brain abnormality in children with CMV infection and children with HSV infection.

CONCLUSION

There was evidence that WM imaging techniques can play a role as diagnostic and evaluation tools assessing the impact of congenital infections and perinatal viral exposures on the developing brain. The high sensitivity for identifying WM hyperintensities suggests structural brain MRI is a useful neurodiagnostic modality in assessing children with congenital CMV infection, while the DTI changes associated with HIV suggest metrics such as fractional anisotropy have the potential to be specific markers of subtle impairment or WM damage in neuroHIV.

Neonatal herpes simplex virus infection: From the maternal infection to the child outcome

This review examines the recent literature on the management of herpes simplex virus (HSV) infections in neonates. We summarized the three clinical categories of maternal HSV infection during pregnancy (primary first episode, nonprimary first episode, or recurrent episode) and the mechanisms of fetal damage. Considering when the transmission of the infection from the mother to the fetus/newborn occurs, three types of neonatal infection can be distinguished: intrauterine infection (5% of cases), postnatal infection (10% of cases), and perinatal infections (85% of cases). Neonatal presentation could range from a limited disease with skin, eye, and mouth disease to central nervous system disease or disseminated disease: the treatment with acyclovir should be tailored according to symptoms and signs of infection, and virological tests. These children need a multidisciplinary follow-up, to timely intercept any deviation from normal neurodevelopmental milestones. Prevention strategies remain a challenge, in the absence of an available vaccine against HSV.

The Many Faces of Neurological Neonatal Herpes Simplex Virus Infection

This case series explores the various manifestations of central nervous system (CNS) involvement in neonatal herpes simplex virus (HSV) infection and highlights the challenges involved in their diagnosis and treatment. Neonatal HSV infection is a rare but serious condition that can have significant neurological consequences. The article presents three cases of neonatal HSV infection, all involving the CNS, each characterized by distinct clinical features and outcomes. Case 1 describes a three-week-old male with severe HSV meningoencephalitis resulting in poor response to treatment and death. Cases 2 and 3 describe younger neonates who presented early in the disease course with disseminated infection and skin, eye, and mouth (SEM) lesions. Although both patients had CNS involvement, their outcomes were remarkably favorable. The wide range of clinical presentations of CNS manifestations in neonatal HSV infection, ranging from nonspecific to evident neurological symptoms, underscores the need for a high index of suspicion and comprehensive evaluation to ensure early diagnosis and appropriate treatment. However, it also notes that even with timely treatment, some cases may still have a poor prognosis.

From Fetal to Neonatal Neuroimaging in TORCH Infections: A Pictorial Review

Congenital infections represent a challenging and varied clinical scenario in which the brain is frequently involved. Therefore, fetal and neonatal neuro-imaging plays a pivotal role in reaching an accurate diagnosis and in predicting the clinical outcome. Congenital brain infections are characterized by various clinical manifestations, ranging from nearly asymptomatic diseases to syndromic disorders, often associated with severe neurological symptoms. Brain damage results from the complex interaction among the infectious agent, its specific cellular tropism, and the stage of development of the central nervous system at the time of the maternal infection. Therefore, neuroradiological findings vary widely and are the result of complex events. An early detection is essential to establishing a proper diagnosis and prognosis, and to guarantee an optimal and prompt therapeutic perinatal management. Recently, emerging infective agents (i.e., Zika virus and SARS-CoV2) have been related to possible pre- and perinatal brain damage, thus expanding the spectrum of congenital brain infections. The purpose of this pictorial review is to provide an overview of the current knowledge on fetal and neonatal brain neuroimaging patterns in congenital brain infections used in clinical practice.

Uncommon acute neuroimaging findings in severe neonatal herpes simplex virus 2 and consequences of delayed diagnosis

Neonatal herpes simplex virus (HSV) infection of the central nervous system (CNS) is an emergency that can have devastating structural consequences and clinical outcomes. As it presents non-specifically in neonates, it is difficult to rapidly diagnose without neuroimaging. Although once thought to cause widespread parenchymal destruction, neonatal CNS HSV infection may present with more focal parenchymal injury on neuroimaging, not involving the medial temporal lobes as in adults. We report a case of a three-week-old girl with herpes simplex virus type 2 (HSV-2) encephalitis with exclusive bilateral corticospinal and frontal opercular involvement, which remained undiagnosed and untreated until three months of age. Neuroimaging upon presentation to the emergency room demonstrates a highly suggestive pattern of severe neonatal CNS HSV-2 infection which followed the natural history on subsequent imaging, highlighting the importance of emergency neuroimaging as well as having a high index of suspicion for making the diagnosis.

Viral Infections of the Central Nervous System in Children: A Systematic Review

Viral infections of the central nervous system such as meningitis, encephalitis or meningoencephalitis, are important causes of significant morbidities and mortality worldwide. Early diagnosis and prompt treatment will lead to better outcomes, but any delay may results in high fatality with serious neurologic sequelae among survivors. We conducted a systematic review of published literature on the clinical presentation, diagnosis, treatment and complications of viral infections of the central nervous system from 1980 to 2019 on four databases comprising of PubMed, PubMed Central, Google Scholar and Medline to give the current understanding for better patient management. This systematic review demonstrates the management approach of viral infections of the central nervous system in children from the point of clinical presentation, diagnosis, treatment and complications. Definitive treatment remained unknown; however, certain antiviral drugs were proved to be effective. Therefore, prevention through childhood vaccination is the best management option.

Enteroviral and herpes simplex virus central nervous system infections in infants < 90 days old: a Paediatric Investigators' Collaborative Network on Infections in Canada (PICNIC) study

Background

The relative contribution of viruses to central nervous system (CNS) infections in young infants is not clear. For viral CNS infections, there are limited data on features that suggest HSV etiology or on predictors of unfavorable outcome.

Methods

In this cross-sectional retrospective study, seven centers from the Pediatric Investigators Collaborative Network on Infections in Canada identified infants < 90 days of age with CNS infection proven to be due to enterovirus (EV) or herpes simplex virus (HSV) January 1, 2013 through December 31, 2014.

Results

Of 174 CNS infections with a proven etiology, EV accounted for 103 (59%) and HSV for 7 (4%). All HSV cases and 41 (40%) EV cases presented before 21 days of age. Four HSV cases (57%) and 5 EV cases (5%) had seizures. Three (43%) HSV and 23 (23%) EV cases lacked cerebrospinal fluid (CSF) pleocytosis. HSV cases were more likely to require ICU admission (p = 0.010), present with seizures (p = 0.031) and have extra-CNS disease (p < 0.001). Unfavorable outcome occurred in 12 cases (11% of all EV and HSV infections) but was more likely following HSV than EV infection (4 (57%) versus 8 (8%); p = 0.002).

Conclusions

Viruses accounted for approximately two-thirds of proven CNS infections in the first 90 days of life. Empiric therapy for HSV should be considered in suspected CNS infections in the first 21 days even in the absence of CSF pleocytosis unless CSF parameters are suggestive of bacterial meningitis. Neurodevelopmental follow-up should be considered in infants whose course of illness is complicated by seizures.

Viral Infections and the Neonatal Brain

This review includes the congenital infections best known by the acronym TORCH (Toxoplasma gondii, rubella virus, cytomegalovirus, and herpes virus), as well as Zika virus infection and perinatally acquired infections (enterovirus, parechovirus, rotavirus, parvovirus). Congenital infections are due to pathogens that can cross the placenta and are more likely to injure the brain when the infection occurs early in pregnancy. There are many similarities, with regards to brain lesions, for congenital Zika syndrome and congenital cytomegalovirus infection. Perinatally acquired viral infections tend to injure the white matter, with cystic evolution being more likely in the (late) preterm infant compared to the full-term infant. Congenital and perinatally acquired viral infections can be associated with adverse neurological outcomes. Prevention is important, especially as therapeutic options are limited. In this review both congenital as well as perinatally acquired viral infections will be discussed with a focus on neuro-imaging findings.

Magnetic resonanse imaging as a prognostic tool in encephalitis in children

We provide the data on the modern use of MRI of different modalities as a prognostic tool in the encephalitis diagnostics in pediatrics. According to the recent scientific knowledge, this implementation is possible, but its efficacy depends on the modality of MRI: structural, functional or MRI with contrast. Structural MRI efficacy in children with encephalitis is dubious and clearly depends on the etiology and phase of the inflammatory process. In the recent years, the implementation of the functional MRI methods (DTI MRS) and MRI with contrast significantly changed the imaging practice; there are some reports that these modalities of MRI are more effective as a prognostic tool in encephalitis than the structural one. Thus, a future research in this field is needed.

Neonatal brain: Fabrication of a tissue-mimicking phantom and optimization of clinical Τ1w and T2w MRI sequences at 1.5 T

PURPOSE

Tο fabricate a tissue-mimicking phantom simulating the MR relaxation times of neonatal gray and white matter at 1.5 T, for the optimization of clinical Τ1 weighted (T1w) and T2 weighted (T2w) sequences.

METHODS

Numerous agarose gel solutions, doped with paramagnetic Gadopentetic acid (Gd-DTPA) ions, underwent quantitative relaxometry with a Turbo-Inversion-Recovery Spin-Echo (TIRSE) sequence and a Car-Purcell-Meiboom-Gill (CPMG) sequence for T1 and T2 measurements, respectively. Twenty samples which simulated the spectrum of relaxation times of neonatal brain parenchyma were selected. Reproducibility was tested by refabrication and relaxometry of the relevant samples while stability was tested by six sets of quantitative relaxometry scans during a 12-month period.

RESULTS

"Neonatal gray matter equivalent"(0.6%w/v agarose-0.10 mM Gd-DTPA), accurately mimicked relaxation times of neonatal gray matter: T1 = (1134 ± 7)ms, T2 = (200 ± 7)ms. "Neonatal white matter equivalent"(0.3%w/v agarose-0.03 mM Gd-DTPA), accurately mimicked relaxation times of neonatal white matter: T1 = (1654 ± 9)ms, T2 = (376 ± 4)ms. Coefficient of variation of T1 and T2 relaxation times measurements remained less than 5% during 12 months. Sequences were modified according to maximum relative contrast (RC) between neonatal gray and white matter equivalents. Optimized T2wTSE and T1wTSE parameters were TR/TE = 9500 ms/280 ms and TR/TE = 1200 ms/10 ms, respectively for a MAGNETOM Vision/Sonata Hybrid 1.5 T system. Quantitative relaxometry at different 1.5 T MR systems resulted in inter-system T1, T2 measurement deviations of 12% and 3%, respectively.

CONCLUSION

A precise, stable and reproducible phantom for the neonatal brain was fabricated. Subsequent optimization of clinical T1w and T2w sequences based on maximum RC between neonatal gray and white matter equivalents was scientifically supported with robust relaxometry. The procedure was applicable in different 1.5 T systems.

HIGHLIGHT

TR & TE optimization of neonatal brain at 1.5 T was based on relaxometry of a stable, reproducible phantom.

Use of high b value diffusion-weighted magnetic resonance imaging in acute encephalopathy/encephalitis during childhood

AIM

To determine the use of high b value diffusion-weighted imaging (DWI) in the diagnosis and assessment of acute febrile encephalopathy/encephalitis in childhood.

SUBJECTS AND METHODS

We enrolled 22 children, for whom we examined DWI with b=1000s/mm², DWI with b=3000s/mm², and apparent diffusion coefficient (ADC) map with b=1000 during the acute phase of febrile encephalopathy/encephalitis. Clinical diagnoses included acute encephalopathy with biphasic seizures and late reduced diffusion (AESD; n=6), clinically mild encephalopathy/encephalitis with a reversible splenial lesion (MERS; n=6), and herpes simplex virus encephalitis (HSE; n=3), unclassified acute encephalopathy/acute encephalitis (n=2); acute encephalitis with refractory, repetitive partial seizures (AERRPS; n=1); other encephalopathy (n=1); infarction (n=1); head injury (n=1); or mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (n=1). The diagnostic quality of brain lesions was compared between b=1000 and b=3000 DWI images by visual inspection. In addition, we attempted a quantitative assessment using apparent diffusion coefficient (ADC) value and an index of signal intensity (SI) ratio, defined as the mean SI at the affected lesion divided by the mean SI at the pons.

RESULTS

High intensity lesions were either visible only on b=3000 DWI (n=5; 2 AESD, 1 MERS, 1 HSE, and 1 unclassifiable encephalopathy) or more effectively identified on b=3000 DWI than on b=1000 DWI (n=17). The outcome of the former five subjects was favorable, without motor or intellectual sequelae. The mean SI ratio of b=3000 was significantly greater than that of b=1000 in AESD and MERS subgroups as well as in all 22 subjects. Mean ADC values were lower in the AESD and MERS than that in the HSE subgroups.

CONCLUSION

We concluded that b=3000 DWI was superior to b=1000 DWI in detecting abnormal lesions in acute encephalopathy/encephalitis during childhood.

Apparent Diffusion Coefficient analysis of encephalitis: A comparative study with topographic evaluation and conventional MRI findings

Objective:

Our purpose was to reveal the efficiency of diffusion weighted imaging (DWI) in the diagnosis of encephalitis, and to determine the relation between the apparent diffusion coefficient (ADC) values, the onset of the clinical symptoms, and the lesion extent.

Methods:

Conventional magnetic resonance imaging (MRI) was performed in 17 patients with encephalitis diagnosed on the basis of laboratory, clinical and radiologic findings during 2009 and 2015. Based on the duration between the onset of the symptoms and the brain MRI findings, the patients were divided into three groups. ADC values of the encephalitis lesion, the lesions’ topographic analysis score, deep gray matter involvement, patients’ clinical situation and the duration of the arrival to the clinic was examined.

Results:

Mean ADC values were 0,988±0,335 x10^-3 mm²/s in group I (0-2 days), 1,045±0,347 x10^-3 mm²/s in Group-II (3-7 days), 1,451±0,225 x10^-3 mm²/s in Group-III (8 days and over). The relation between the ADC values and the duration of the arrival, topographic analysis score, the relation between the patients’ clinical situation and the deep gray matter involvement were found to be statistically significant. The deep gray matter involvement was demonstrated more clearly by FLAIR images when compared with DWI.

Conclusion:

Conventional MRI sequences may be insufficient in showing the encephalitis lesion. DWI must be added to the imaging modalities immediately in the cases suspected of having encephalitis.

Herpes Simplex Virus-1 Encephalitis in Adults: Pathophysiology, Diagnosis, and Management

Herpetic infections have plagued humanity for thousands of years, but only recently have advances in antiviral medications and supportive treatments equipped physicians to combat the most severe manifestations of disease. Prompt recognition and treatment can be life-saving in the care of patients with herpes simplex-1 virus encephalitis, the most commonly identified cause of sporadic encephalitis worldwide. Clinicians should be able to recognize the clinical signs and symptoms of the infection and familiarize themselves with a rational diagnostic approach and therapeutic modalities, as early recognition and treatment are key to improving outcomes. Clinicians should also be vigilant for the development of acute complications, including cerebral edema and status epilepticus, as well as chronic complications, including the development of autoimmune encephalitis associated with antibodies to the N-methyl-D-aspartate receptor and other neuronal cell surface and synaptic epitopes. Herein, we review the pathophysiology, differential diagnosis, and clinical and radiological features of herpes simplex virus-1 encephalitis in adults, including a discussion of the most common complications and their treatment. While great progress has been made in the treatment of this life-threatening infection, a majority of patients will not return to their previous neurologic baseline, indicating the need for further research efforts aimed at improving the long-term sequelae.