History and Physical
A 7-year-old male presented with fever for the past three days, followed by multiple generalized tonic seizures and altered sensorium. There was no recent history of respiratory symptoms or known exposure to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection. Birth history was unremarkable. At 2 months of age, he had one episode of unprovoked seizure for which he received antiseizure medications for 3 months. He was the second child of 4 siblings and showed mild developmental delay.
On examination, he was febrile with tachycardia (120/min) and normal blood pressure. Anthropometry was normal for age. He had mild pallor, a Glasgow Coma Scale of 10, right facial palsy, normal tone, brisk deep tendon reflexes, extensor plantar responses, normally reacting pupils, and absence of papilledema. He was empirically started on intravenous ceftriaxone, acyclovir, and phenytoin.
Diagnostic Workup
MRI brain on day 1 of hospitalization showed bilateral asymmetrical hyperintense lesions involving the thalamus, midbrain, and pons on T2 weighted images with diffusion restriction ( Fig. 38.1 ).
Acute necrotizing encephalopathy of childhood. Brain MRI, (A) axial T2, (B) FLAIR, and (C) ADC show hyperintense signal and restricted diffusion in the bilateral thalami, internal capsules, and pons ( arrows ).
Complete blood count, renal and liver function tests were normal. Blood culture was sterile. Cerebrospinal fluid examination (CSF) showed 3 cells/mm 3 , glucose 67 mg%, protein 68 mg%, sterile culture, and negative PCR for HSV-1 and Japanese encephalitis (JE) viruses. Serum ammonia was 58 mmol/L and lactate was 1.4 mmol/L.
Nasopharyngeal swab PCR was positive for SARS-CoV-2. SARS-CoV-2 serology was negative. The patient was treated with intravenous methylprednisolone (30 mg/kg/day) for 5 days, resulting in gradual improvement of sensorium and discharge after a hospital stay of 10 days.
Clinical Differential Diagnoses
Acute febrile encephalopathy can be seen with infectious etiologies, such as acute viral encephalitis (HSV) and acute pyogenic bacterial meningitis. Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) can directly affect the CNS.
Autoimmune disorders include acute necrotizing encephalopathy of childhood (ANEC), demyelinating diseases, and febrile infection-related status epilepticus (FIRES).
Metabolic encephalopathies (urea cycle, organic acidemias, mitochondrial disorders) can be triggered by febrile illness.
Imaging Differential Diagnoses
Bilateral thalamic and brainstem involvement can be seen in viral infections like JE ( Fig. 38.2 ), rabies encephalitis ( Fig. 38.3 ), dengue, and West Nile virus.
