Extrapontine Myelinolysis With Involvement of the Hippocampus in Three Children With Severe Hypernatremia

Abstract

Central pontine myelinolysis is a disorder of unknown etiology linked to overly aggressive correction of hyponatremia. In addition to the typical location of demyelination with preservation of neurons and axon cylinders in the basis pontis, similar lesions have been described in extrapontine locations. Central pontine myelinolysis and extrapontine myelinolysis usually occur together, and are identified at autopsy rather than in life because symptoms of extrapontine myelinolysis are often masked in the critically ill patient. Central pontine myelinolysis is described in children, usually in the clinical setting of hyponatremic dehydration. Extrapontine myelinolysis has not been described in children previously. We report three children with severe hypernatremia and extrapontine myelinolysis involving various combinations of thalamus, basal ganglia, external and extreme capsules, and cerebellar vermis. All three had additional involvement of the hippocampus seen on T2-weighted magnetic resonance imaging. None of the three had detectable pontine lesions. Clinical features of the three cases were dehydration in a 28-month-old girl, respiratory syncytial virus bronchiolitis in a 14-month-old girl, and acute respiratory failure due to anaphylaxis after consumption of walnuts in a 3-year-old boy. Peak sodium values in each child were 195, 168, and 177 mmol/L, respectively; each received aggressive treatment for hypernatremia. We believe this to be the first report of extrapontine myelinolysis in children, the first report of extrapontine myelinolysis without central pontine myelinolysis in children, and the first report in children of hippocampal formation involvement. The pathogenesis of the central and extrapontine myelinolysis complex in children is more complicated than previously believed, and might differ significantly from that of adults.

Clinical Semiology and Neuroradiologic Correlates of Acute Hypernatremic Osmotic Challenge in Adults: A Literature Review

“…Both CPM 62,63 and EPM presentations are frequently encountered in pediatric patients, with extrapontine lesions reported to be thalamic, 64,65 in the basal ganglia, 66 and hippocampal. 67 Despite similar distributions of lesions, pediatric patients have better recovery and the associated MR imaging lesions are more reversible, 41,68 results that may be related to age-associated changes in osmotic regulatory mechanisms. It has been shown that water, electrolytes, and organic osmole (mainly taurine) content in the brain of normonatremic rats decreases with age, implying that young brains might have a greater capacity to counteract osmotic perturbations.…”

Pontine and extrapontine osmotic myelinolysis after the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) associated with fluoxetine: case report

“…Demyelination in pontine or extrapontine locations does not appear exclusively in adult or alcoholic patients with hyponatremia 12 but may occur when the serum sodium level is normal 13,14 or elevated 15,16 .…”

Central pontine and extrapontine myelinolysis: report of a case with a tragic outcome

“…As lesões pontinas podem estar associadas à mielinólise extrapontina (MEP), a qual pode acometer de maneira simétrica os pedúnculos cerebelares, núcleo caudado, putame, substância branca frontal e temporal, fórnix, cápsula externa e extrema, claustro, tálamo, núcleo subtalâmico, cápsula interna, núcleo amigdalóide, corpo geniculado lateral, camadas profundas do córtex cerebral, hipocampo e corpo caloso 3,4,[6][7][8][9] .…”

“…Alguns distúrbios parecem acarretar predisposição ao desenvolvimento dessa complicação, como insuficiência hepática, transplante hepático, cirurgia de ressecção de tumor da hipófise, queimaduras graves, insuficiência renal crônica, hemodiálise, linfoma, carcinoma, desnutrição, infecções bacterianas graves, desidratação, desequilí-brios eletrolíticos (hiponatremia, hipernatremia 7 , hiperglicemia, hipocalemia 6 , diabetes), pancreatite hemorrágica aguda e alcoolismo crônico, entre outros 4,6,7,9,12 .…”

“…Sua apresentação clínica inclui tetraparesia inicialmente flácida e depois espástica, paralisia pseudobulbar, alterações agudas no estado mental com depressão da consciên-cia, coma, síndrome de encarceramento, podendo progredir para morte [1][2][3][4][5][6][7][8][9][10][12][13][14] . Comumente surge 2 a 7 dias após a correção da hiponatremia 2,3,5,9,12 .…”