Clinically mild infantile encephalopathy associated with excitotoxicity

HHV-6-Associated Neurological Disease in Children: Epidemiologic, Clinical, Diagnostic, and Treatment Considerations

Human herpesviruses 6A and 6B, often referred to collectively as human herpesvirus 6, are a pair of beta-herpesviruses known to cause a variety of clinical syndromes in both immunocompetent and immunocompromised individuals. Most humans are infected with human herpesvirus 6B, and many with human herpesvirus 6A. Primary infection typically occurs in early childhood, although large-scale reviews on the topic are limited. Herein, the authors explore the clinical manifestations of human herpesvirus 6-associated disease in both immunocompetent and immunocompromised pediatric patients, the risk factors for development of human herpesvirus 6-associated neurological disease, the risk of autoimmunity associated with development of active or latent infection, the relevance of human herpesvirus 6-specific diagnostic tests, and the medications used to treat human herpesvirus 6. The goal of this review is to improve the current understanding of human herpesvirus 6 in pediatric populations and to examine the most effective diagnostic and therapeutic interventions in this disease state.

Granzyme A Participates in the Pathogenesis of Infection-Associated Acute Encephalopathy

OBJECTIVE

The present study aimed to determine whether granzymes are implicated in the pathogenesis of infection-associated acute encephalopathy (AE).

METHODS

We investigated granzyme and cytokine levels in the cerebrospinal fluid of patients with acute encephalopathy or complex febrile seizures (cFS). A total of 24 acute encephalopathy patients and 22 complex febrile seizures patients were included in the present study. Levels of granzymes A and B were measured using enzyme-linked immunosorbent assay, and levels of tumor necrosis factor α (TNF-α), interferon-γ (IFN-γ), interleukin 1β (IL-1β), IL-1 receptor antagonist (IL-1RA), IL-4, IL-6, IL-8, and IL-10 were assessed using the Bio-Plex suspension array system.

RESULTS

Cerebrospinal fluid levels of granzyme A were significantly higher, and those of TNF-α and IL-1RA were significantly lower in the AE group than in the cFS group; however, no significant differences in the levels of granzyme B, IFN-γ, IL-1β, IL-4, IL-6, IL-8, and IL-10 were observed between the 2 groups. In addition, no significant differences in granzyme A, granzyme B, or cytokine levels were observed between acute encephalopathy patients with and those without neurologic sequelae.

CONCLUSIONS

Our findings indicate the involvement of granzyme A in the pathogenesis of acute encephalopathy.

Prognostic value of MR spectroscopy in patients with acute excitotoxic encephalopathy

PURPOSE

Acute excitotoxic encephalopathy is the most common encephalopathy syndrome in Japan, and consists of acute encephalopathy with biphasic seizures and late reduced diffusion (AESD) and mild encephalopathy associated with excitotoxicity (MEEX). Neurological sequelae remain in approximately 70% of patients with AESD, however, it is difficult to predict the prognosis early in the course. We evaluated the brain metabolites observed on MRS as to whether they can predict the neurological outcome.

METHODS

16 previously healthy Japanese patients with excitotoxic encephalopathy (8 with AESD and 8 with MEEX) were included in this study. MR spectroscopy (MRS) was acquired from the fronto-parietal white matter (TR/TE = 5000/30 msec) with a 3.0 T scanner. Quantification of metabolites was performed using an LCModel. Neurological outcome was assessed with the Pediatric Cerebral Performance Category score, score 1 being classified as G1 (normal), scores 2 and 3 as G2 (mild to moderate), and scores 4-6 as G3 (severe).

RESULTS

MRS data which predict a poor neurological outcome (G2 and 3) include the following: decreased N-acetyl aspartate (NAA) (sensitivity 88%, specificity 100%), decreased creatine (47%, 100%), increased lactate (47%, 100%), and decreased glutamate (sensitivity 35%, specificity 100%). Limited to the acute stage within seven days of onset, those for a poor prognosis are as follows, decreased NAA (88%, 100%), decreased creatine (38%, 100%), and increased lactate (38%, 100%).

CONCLUSION

MRS is useful for prognosis prediction of acute excitotoxic encephalopathy. Decreased NAA will be the most effective metabolite for neurological prognosis prediction.

A new infectious encephalopathy syndrome, clinically mild encephalopathy associated with excitotoxicity (MEEX)

Acute infectious encephalopathy is often observed in children in East Asia including Japan. More than 40% of the patients remain unclassified into specific syndromes. To investigate the underlying pathomechanisms in those with unclassified encephalopathy, we evaluated brain metabolism by MR spectroscopy. Among seven patients with acute encephalopathy admitted to our hospital from June 2016 to May 2017, three were classified into acute encephalopathy with biphasic seizures and late reduced diffusion (AESD). The other four showed consciousness disturbance lasting more than three days with no parenchymal lesion visible on MRI, which led to a diagnosis of unclassified encephalopathy. MR spectroscopy in these four patients, however, revealed an increase of glutamine with a normal N-acetyl aspartate level on days 5 to 8, which had normalized by follow-up studies on days 11 to 16. The four patients clinically recovered completely. Among 27 patients with encephalopathy, including the present seven patients, admitted to our hospital from January 2015 to March 2017, seven (26%) were classified into this type, which we propose is a new encephalopathy syndrome, clinically mild encephalopathy associated with excitotoxicity (MEEX). MEEX is the second most common subtype, following AESD (30%). This study suggests that excitotoxicity may be a common underlying pathomechanism of acute infectious encephalopathy, and prompt astrocytic neuroprotection from excitotoxicity may prevent progression of MEEX into AESD.