From Heart to Brain

History and Physical

A 2-month-old infant male prenatally diagnosed with transposition of the great arteries experienced neonatal seizures that were treated with phenobarbital. He then underwent an arterial switch operation, left ventricular outflow tract repair, and ventricular septal defect closure. In the immediate postoperative period, the patient presented with fluid-refractory hypotension. Three days after surgery, after sedatives were titrated down , he developed abrupt-onset stereotyped episodes of eye opening, mydriasis, and left lower limb clonic movements lasting several seconds. On neurological examination, he was awake and ventilated on low doses of sedative agents. Cranial nerve examination showed symmetric and reactive pupils. Motor and sensory examinations were normal, including deep tendon reflexes.

Diagnostic Workup

EEG showed paroxysms of sharp waves in both temporal lobes, with a wider initial amplitude on the right followed by voltage attenuation.

Head ultrasound was normal. Head CT performed 2 hours after seizure onset revealed multifocal cytotoxic edema in the right greater than left cerebral gray and white matter ( Fig. 23.1 ).

A C T Scan of multifocal areas of head swelling in the right and left cerebral hemispheres. The illustration contains three axial head C T panels labeled A through C. Panel A shows areas of low density in both the right and left cerebral hemispheres, with larger involvement on the right side. Panel B shows increased swelling in the right hemisphere and involves both gray and white matter. Panel C shows asymmetric low density in the cerebral hemispheres and preserves the midline. Arrows point to affected regions in all three panels. — Fig. 23.1

Brain MRI performed on day 16 exhibited evolution of infarcts with T2-hyperintense gliosis and volume loss ( Fig. 23.2A and B ). On diffusion-weighted imaging, there was restricted diffusion in the splenium of corpus callosum and right thalamus related to seizure activity ( Fig. 23.2C ).

An M R I scan shows labeled multiple hyperintense areas with two arrows and one arrowhead across three panels. The illustration contains three panels. Panel A shows two arrows that point to symmetrical regions in the occipital white matter near the posterior horns of the lateral ventricles. Panel B shows an arrow that points to a round area next to the right lateral ventricle within the periventricular white matter. Panel C shows an arrowhead that points to a midline area in the posterior brain at the level of the splenium of the corpus callosum. — Figure 23.2

Clinical Differential Diagnosis

Neurologic complications are common in children with CHD and can present with seizures following cardiac surgery. Reversible causes of seizure, such as hypoglycemia and electrolyte disturbances, should be excluded. Perioperative hypoxia-ischemia can lead to global cerebral hypoperfusion and postoperative reperfusion injury. Other vascular causes include vaso-occlusive insults and bland, fat, or air emboli from cardiopulmonary bypass. Extracorporeal membrane oxygenation (ECMO) may injure the brain through ischemic and/or hemorrhagic mechanisms. Systemic heparinization increases the risk of intracranial hemorrhage, either primary or secondary. Brain abscess is a rare complication of cyanotic heart disease with right-to-left shunts.

Acquired heart disease is most commonly caused by infection or parainfectious autoimmune conditions. Viral myocarditis and rheumatic heart disease predispose to embolism and cerebral ischemia.

Imaging Differential Diagnosis

Mild cases of hypoxic-ischemic encephalopathy (HIE) due to brief and partial limitations of blood flow or oxygen can demonstrate damage to the cerebral and cerebellar watershed zones ( Fig. 23.3 ). Moderate-to-severe HIE is seen with complete and prolonged loss of blood flow or oxygen. This selectively affects the most actively developing and hypermetabolic areas of the brain, including perirolandic and occipital cortex, basal ganglia, and limbic structures. In the first 1 to 2 days of injury, diffusion-weighted imaging (DWI) is positive, followed by T1 shortening from dysmyelination and then T2-hyperintense edema. Over time, areas of damaged brain evolve into apoptosis and/or necrosis with encephalomalacia.