[Acute necrotizing encephalopathy with horizontal gaze palsy].

Acute necrotizing encephalopathy (ANE) of childhood is a newly proposed disease entity characterized by symmetrically distributed necrotic brain lesions in the thalamus, cerebral white matter, brainstem, and cerebellum. We report a 4-year-old girl with severe psychomotor delay and horizontal gaze palsy as sequelae of ANE at 17 months of age. The computed tomography showed bilaterally symmetrical low density areas in the thalamus and low density areas in the left middle cerebral artery (MCA) region and the posterior cerebral artery (PCA) region. MRI (T 1-weighted) revealed unevenly distributed small low signal intensity areas with scattered high intensity regions in the thalamus bilaterally. The T2-weighted images showed multiple small low intensity areas around high intensity areas, and low signal intensity areas in the left middle cerebral artery (MCA) region and the posterior cerebral artery (PCA) region. In addition to severe psychomotor delay, the patient exhibited a peculiar eye movements. Horizontal ocular movement was impaired, but vertical ocular movement was almost completely normal. As clearly shown by MRI of the brain, the pontine tegmentum, including bilateral abducens nucleus, paramedian pontine reticular formation (PPRF), medial longitudinal fasciculus (MLF), and the facial nerve were affected, but the thalamo-mesencephalic junction, including the rostral interstitial medial longitudinal fasciculus (riMLF) and the nucleus of Cajal, was spared. To our knowledge, this is the first case of ANE associated with this selective ocular movement disorder ever reported. Because of the multiple symmetrical lesions and pons and the asymmetrical lesions of the MCA and PCA regions in the present case, occlusion of a single vessel could not account for the pathology. The pathophysiological mechanism of ANE is unknown. We postulate that some toxic or vasoactive agent caused vasospasm and subsequent breakdown of the blood-brain barrier, especially in the thalamus and pons, resulting in the unique distribution of the lesions and the rare eye movement disorder observed in the present case.