Neurologic sequelae of opioid overdose in a child
Four-year-old child presented with neurologic sequelae of accidental oxycodone overdose.
In the supratentorial brain, prescription opioid overdose presents as hypoxic ischemic changes with cytotoxic edema, ischemic neuronal damage and loss assumed to occur due to prolonged periods of respiratory depression. These are seen on CT as diffuse loss of gray-white matter differentiation in bilateral cerebral hemispheres and on MRI as restricted diffusion with T2 hyperintensity and T1 hypointensity. Involvement of basal ganglia, hippocampus and corpus callosum are mentioned in the literature but not seen consistently. Prolonged ischemia can result in mass effect with ventricular and sulcal effacement as well as uncal and inferior transtentorial herniation resulting in additional areas of microvascular compromise and infarcts. Hemorrhagic conversion has been reported in the literature as well, presumably due to microvascular damage from ischemia. In the infratentorial brain, similar hypoxic ischemic changes with CT and MRI features have been reported in the cerebellar white matter symmetrically. Prolonged ischemia can result in mass effect, which can efface the 4th ventricle and result in obstructive hydrocephalus and superior or inferior transtentorial herniation resulting in additional areas of microvascular compromise and infarcts. Likewise, hemorrhagic conversion has been reported as well.
It is understood that the greatest number of opioid associated mu receptors in the brain are found in the cerebellum. It has been hypothesized that hyperstimulation of these receptors causes proportionate increase in cellular metabolic activity which depletes the energy stores. Cerebellar energy store depletion is further exacerbated by systemic hypoxia/ischemia and acidosis. On MR spectroscopy, findings of elevated lactate levels while preserved myelination of the cerebellum further corroborates this hypothesis.
Hypoxic ischemic changes with hemorrhage, involving both supratentorial and infratentorial brain are key features of opioid toxicity in children.