Cranial Magnetic Resonance Imaging Findings in Hypotonic Infants with Cobalamin Deficiency and Combined Methylmalonic Aciduria and Homocystinuria

Vitamin B12 begins to accumulate in infants within the first six months while mothers often remain asymptomatic and infantile vitamin B12 deficiency may not be noticed until the onset of neurological effects. In infants with Cbl deficiency, long-term exposure to elevated methylmalonic acid and homocysteine (MMA-HC) may have toxic effects on the central nervous system. The aim of this study was to evaluate cranial magnetic resonance (MRI) findings of 23 hypotonic infants that were followed up with a diagnosis of nutritional Cbl deficiency and combined MMA-HC. Of the 78 infants that presented with hypotonicity, 23 (29.4%) infants were detected with vitamin B12 deficiency. Elevated MMA-HC levels were detected in all patients (100%). Cranial MRI showed cortical atrophy in 6 (26.0%)-large sylvian fissures in 7 (30.4%)-ventricular dilatation in 5 (21.7%)-corpuscallosal thinning in 6 (26.0%)-delayed myelination in 3 (13%), and normal in 8 (34.7%) infants.Infants detected with corpus callosal thinning and cortical atrophy on MRI. Vitamin B12 deficiency is a treatable condition, it should be suspected in infants presenting with hypotonicity. Neuroradiological findings should be considered in the diagnosis of such patients. Infantile nutritional vitamin B12 deficiency, which can be a source of persistent neurological deficits during the long term, should be treated to allow the patient to allow healthy neuro-development for infants. Maternal and fetal vitamin B12 levels should be assessed during the third trimester of pregnancy to prevent long-term exposure to infantile vitamin B12 deficiency.