An elderly man with mild encephalitis/encephalopathy with a reversible splenial lesion (MERS) without neuropsychiatric sequelae

Mild encephalitis/encephalopathy with a reversible splenial lesion (MERS) is less common in the elderly, and most have some sequelae. However, even in the elderly, MERS may have a good prognosis, and a specific treatment is not always required.

Japanese Spotted Fever Associated with Mild Encephalitis/Encephalopathy with a Reversible Splenial Lesion

A 58-year-old woman had disseminated intravascular coagulation (DIC) and septic shock caused by Japanese spotted fever (JSF). Following treatment with minocycline, her general condition gradually improved; however, her disorientation persisted. Mild encephalitis/encephalopathy with a reversible splenial lesion (MERS) type II was diagnosed based on brain magnetic resonance imaging (MRI) showing a hyperintense area in the splenium of the corpus callosum and bilateral cerebral white matter on diffusion-weighted imaging. Thereafter, her consciousness gradually improved, but she continued to experience difficulty concentrating and attention deficits. MERS type II may take longer to improve than type I, and long-term follow-up is required.

Mild Encephalitis/Encephalopathy with a Reversible Lesion in The Splenium

Mild encephalitis/encephalopathy with a reversible lesion in the splenium (MERS) is a clinico-radiological syndrome with mild central nervous system symptoms and a reversible lesion in the splenium of the corpus callosum. It is mainly associated with a number of viral and bacterial infections, including Coronavirus disease 2019 (COVID-19). In this paper, we report four MERS patients. One had a mumps infection, the second had aseptic meningitis, the third had Marchiafava-Bignami disease, and the fourth had atypical pneumonia associated with COVID-19 infection.

Atezolizumab-induced Encephalitis in a Patient with Hepatocellular Carcinoma: A Case Report and Literature Review

We herein report a case of encephalitis in a 42-year-old woman with hepatocellular carcinoma following atezolizumab plus bevacizumab therapy. After two weeks of treatment, she was admitted for a high fever, impaired consciousness, and convulsive seizure refractory to diazepam. Magnetic resonance imaging revealed a hyperintense splenial lesion. A cerebrospinal fluid test excluded malignancy and infection. These findings were highly suggestive of a diagnosis of encephalitis due to atezolizumab, an immune-related adverse event. Steroid pulse therapy improved the fever and seizure. However, her incomplete right-sided paralysis and aphasia persisted. This is the first case report of encephalitis caused by atezolizumab plus bevacizumab therapy for hepatocellular carcinoma.

Mild encephalitis/encephalopathy with a reversible splenial lesion secondary to encephalitis complicated by hyponatremia: A case report and literature review

RATIONALE

Mild encephalitis/encephalopathy with a reversible splenial lesion (MERS) is an infection-associated encephalitis/encephalopathy syndrome that is predominately caused by a virus. MERS has no direct association with central nervous system (CNS) infections or inflammation. Non-CNS infections may cause reversible lesion in the splenium of corpus callosum. Recently, there have been reports of many patients with hyponatremia related MERS. Interleukin-6 (IL-6) was also found elevated in serum and in cerebrospinal fluid (CSF) in patients with MERS. The role of IL-6 in the non-osmotic release of vasopressin is crucial. Persistent hyponatremia may be linked to this effect. The following is a case report of MERS secondary to encephalitis, complicated by hyponatremia. We will summarize the latest research and progress regarding MERS.

PATIENT CONCERNS

A 31-year-old man was admitted to our department with a 5-day history of fever and headache. His initial diagnosis was encephalitis and hyponatremia; during this period the patient also developed MERS secondary to the encephalitis.

DIAGNOSES

Encephalitis was diagnosed by reviewing the history of fever, headache, neck rigidity and Kerning sign (+) on clinical examination. Lab tests revealed: serum VCA IgG (+), EBNA-1 IgG (-), EBV IgM (-), and inflammation in the analysis of CSF. Cranial MRI+C showed that the blood vessels on the surface of the brain were obviously increasing and thickening and diffuse slow waves were detected on the electroencephalogram (EEG). The patient's hyponatremia aggravated on the third day of hospitalization. On the fourth day of hospitalization, the patient was somnolent, apathetic, and slow. Magnetic resonance imaging (MRI) of the brain, with a T2-weighted fluid attenuated inversion recovery image, showed high-signal intensity in the splenium of the corpus callosum (SCC) on the fifth day of hospitalization. Diffusion-weighted imaging (DWI) showed splenial hyperintensity as a "boomerang sign" and reduced diffusion on apparent diffusion coefficient (ADC) maps. Cranial MRI findings returned to normal after 1 month. The diagnosis of MERS was confirmed.

INTERVENTIONS

We administered an intravenous drip infusion of acyclovir and prescribed oral sodium supplementation.

OUTCOMES

The patient's neurological symptoms gradually improved. The MRI lesion in the SCC disappeared on the 30th day.

LESSONS

In patients with encephalitis accompanied by hyponatremia, elevated IL-6 or urinary β2-microglobulin (β2MG), and exacerbations such as sudden somnolence, delirium, confusion, and seizures, the possibility of secondary MERS should be investigated, in addition to the progression of encephalitis.

Transient Lesion of the Splenium of the Corpus Callosum after Acute Ischemic Stroke

Two patients who showed transient lesions in the splenium of the corpus callosum (SCC) secondary to acute ischemic stroke are reported. Both patients had embolic strokes and showed an isolated lesion in the SCC on magnetic resonance imaging (MRI) 1-2 weeks after the onset of stroke, with a hyperintense lesion on diffusion-weighted imaging and decreased apparent diffusion coefficient values, with no symptoms related to the lesion. In both cases, the lesion disappeared on MRI approximately 1 week later. Clinicians should note that transient SCC lesions can occur following acute ischemic stroke and avoid misdiagnosing them and performing unnecessary examinations or treatment.

Segmental Arterial Mediolysis with Preceding Symptoms Resembling Viral Infection Hampers the Differentiation from Polyarteritis Nodosa

A middle-aged man presented with a fever, arthralgia, gastrointestinal symptoms, headache, and rash. After two weeks, the patient suddenly complained of severe abdominal pain, and computed tomography revealed aneurysms in the hepatic and splenic arteries, which increased in size progressively. Given the elevated levels of inflammatory markers and orchitis, polyarteritis nodosa (PN) was initially suspected. Catheter embolization for the ruptured hepatic aneurysm and splenectomy for the large splenic ones were performed, and the pathological finding was consistent with segmental arterial mediolysis (SAM). Changes in inflammatory marker levels and aneurysmal size are also informative to differentiate SAM from PN.

MERS associated with bacterial translocation in a pediatric patient with congenital portal vein hypoplasia: A case report

A case of mild encephalitis/encephalopathy with a reversible splenial lesion (MERS) in a female child who developed bacterial translocation from a congenital portal vein hypoplasia is reported. The patient was diagnosed as having portal hypertension after examinations and laboratory results showing splenomegaly and thrombocytopenia at the age of 1 year. The patient required three endoscopic variceal ligation (EVL) surgeries before the age of 9 due to development of multiple esophageal varices. After the second and third EVL procedures, she developed septicemia, possibly due to bacterial translocation associated with the administration of general anesthesia. The day after the third EVL, the patient presented with high fever and neurological disturbances (altered consciousness). Magnetic resonance imaging detected abnormal intensities in the corpus callosum ampulla and cerebral white matter, which suggested a diagnosis of MERS type 2. Considering this clinical course, the possible association between bacterial translocation and MERS in a patient with congenital portal vein hypoplasia and portal hypertension is discussed.

Mild encephalitis/encephalopathy with a reversible splenial lesion (MERS) associated with bacteria meningitis caused by listeria monocytogenes: A case report

RATIONALE

Mild encephalitis/encephalopathy with a reversible splenial lesion is a clinico-radiological syndrome mainly triggered by viral infection. Bacteria, like listeria monocytogenes, are relatively rare pathogens.

PATIENT CONCERNS

A two and a half years old girl with a 3-day history of fever and vomiting, complicated by a sudden seizure. She was in a coma after seizure.

DIAGNOSES

Listeria monocytogenes was detected in cerebrospinal fluid cultures. Serum IL-6 remarkably elevated, and hyponatremia appeared on day 2 of hospitalization. Magnetic resonance imaging of the brain performed on day 3 of hospitalization showed right subdural effusion and a lesion in the central portion of the splenium of the corpus callosum.

INTERVENTIONS

We administered antimicrobial therapy, intravenous mannitol and hypertonic fluid therapy.

OUTCOMES

Her neurological symptoms improved gradually. The lesion in the splenium of the corpus callosum completely disappeared on magnetic resonance imaging on day 10 of hospitalization.

LESSONS

We diagnosed this case as mild encephalitis/encephalopathy with a reversible splenial lesion caused by listeria monocytogenes. The patient recovered completely clinically and on imaging, without any specific immunomodulatory treatment. It also indicated IL-6 may play a role in the forms of hyponatremia in mild encephalitis/encephalopathy with a reversible splenial lesion.

Mild Encephalitis/Encephalopathy with a Reversible Splenial Lesion in an Adult Patient with Influenza

We herein report the case of a 31-year-old Japanese woman who developed adult-onset clinically mild encephalitis/encephalopathy with a reversible splenial lesion (MERS) and presented with consciousness disorder and olfactory disturbance secondary to influenza A infection. The patient's neurological symptoms and the lesion in the splenium resolved within 14 days without therapy. Magnetic resonance images and the clinical course were consistent with a diagnosis of MERS; however, mental changes following the influenza infection always present a diagnostic dilemma for physicians. We considered various diagnoses, including viral encephalitis, medication-related encephalopathy, and MERS. A comprehensive assessment may be required to diagnose MERS, since it may mimic other neurological diseases, such as viral encephalitis and medication-related encephalopathy.

[Clinical features of mild encephalitis/encephalopathy with a reversible splenial lesion in children]

OBJECTIVE

To investigate the clinical features of mild encephalitis/encephalopathy with a reversible splenial lesion (MERS) in children.

METHODS

The clinical data of 8 children with MERS were retrospectively analyzed.

RESULTS

The mean age of onset was 5 years and 2 months (range 10 months to 12 years). The major clinical features included a history of prodromal infection, and among these children, 5 had pyrexia and 4 had vomiting. Of all the children, 6 were manifested as convulsion and 3 each were manifested as disturbance of consciousness and paroxysmal paropsia. Cranial diffusion-weighted magnetic resonance imaging (MRI) showed high signals in the splenium of the corpus callosum. Among these children, one child had symmetric and multiple long T1 and long T2 signals in the bilateral centrum semiovale and part of the temporal white matter. MRI reexamination performed after 5-30 days showed the disappearance of abnormal signals in all the children. The children were followed up for 3 months to 2 years, and no child experienced abnormal neurodevelopment.

CONCLUSIONS

The development of MERS in children is closely associated with infection. MERS is characterized by high signals in the splenium of the corpus callosum on cranial diffusion-weighted MRI. Most children have good prognosis.