Acute necrotizing encephalitis of childhood

Acute necrotizing encephalitis of childhood (ANEC) is a rare type of encephalopathy characterized by multiple bilateral brain lesions, mainly involving the thalami, but also the putamina, internal and external capsules, cerebellar white matter, and the brainstem tegmentum.

Acute necrotizing encephalitis of childhood is a rare condition with less than 150 cases reported in the literature. From the first case described in 1995, many cases have been reported in Asia as well as many Western countries. Most cases are sporadic; however, a few cases of recurrent and/or familial episodes have been reported suggesting an inherited pattern. 

Acute necrotizing encephalitis of childhood is seen around the age of 4 years. Clinically, it is characterized by acute encephalopathy, with dramatic neurological deficits/symptoms. A viral etiology has been proposed in some cases; viral prodrome hence may precede the neurological deficits.

The etiology and the pathogenesis of acute necrotizing encephalitis of childhood is only partially clear. Usually, it develops secondary to viral infections, including influenza A and influenza B, parainfluenza, varicella and enterovirus.

Pathologically, the lesions show edema, hemorrhage and necrosis. ANEC is characterized by the lack of inflammatory cells in affected brain parenchyma in comparison to the more common entities of acute disseminated encephalomyelitis and acute hemorrhagic encephalitis 1.

On CT, the corresponding thalamic, putamina, cerebral, cerebellar and brainstem abnormalities are hypodense.

Intracranial hemorrhage and cavitation may also be seen, both of which are associated with a worse prognosis.

In most cases of acute necrotizing encephalitis of childhood, there is bilateral symmetrical thalamic involvement. Abnormal signals on MRI are hypointense on T1 and hyperintense on T2. Restricted diffusion of the involved regions can be seen. 7 These findings can be quite extensive. Hemorrhage, cavitation, and post-contrast enhancement are also seen.

Acute necrotizing encephalitis of childhood carries a very poor prognosis; the mortality rate is near 70%. Treatment is mainly supportive, as the precise etiology remains unknown.

If characteristic symmetric imaging findings are present, the differential diagnosis is limited. Lactic acidosis is not a classic finding of ANEC. Otherwise, the differential diagnoses include:

Clinically, acute necrotizing encephalitis of childhood may be differentiated from ADEM by an early onset of encephalitic features just after the prodromal illness while in ADEM, they may take 1 to 2 weeks to develop. 

Infections of the central nervous system
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Article information

rID: 24838
Synonyms or Alternate Spellings:
  • Acute necrotizing encephalopathy of childhood
  • ANEC
  • Acute necrotizing encephalitis of childhood
  • Acute necrotising encephalitis of childhood (ANEC)

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