Acute neonatal hypoglycaemic encephalopathy

This is a case of an 8 days old baby boy came with complaints of lethargy, poor feeding, refractory seizures and hypotonia for 1 day. He is a full-term normal vaginal delivery child and cried immediately after birth.

Figure 1: On MRI, symmetric areas of restricted diffusion are seen in bilateral parieto-occipital lobes in grey and white matter (red arrow), optic radiations, posterolateral thalami (blue arrow), and corpus callosum (yellow arrow) (Figure 1).

Figure 2: These regions appear isointense to hypointense on T1W (Figure 2a) and slightly hyperintense signal on T2W images (Figure 2b). The basal ganglia appear normal (Figure 1, 2a, 2b).

Figure 3: On MRI, high frontoparietal region showing restricted diffusion in high parietal region (red arrow).

Figure 4: The peri-rolandic region appeared normal.

Background: Neonatal hypoglycaemic encephalopathy is a brain injury caused by low blood glucose < 46gm/dl for prolonged duration.

Pathophysiology: Glucose is the main source of energy for the nervous system. Glucose is oxidised to form ATPs which is used by the nervous system for energy. In hypoglycaemia, due to lack of glucose, damage occurs to the neurons which are responsible for the manifestations.

Clinical Perspective: Clinical presentation of these neonates depend on the extent of hypoglycaemia, rapidity of the fall in glucose levels, duration of hypoglycaemia, responsiveness to treatment and overall condition of the child.

Clinically these patients present with lethargy, poor feeding, seizures, altered sensorium and in later stages coma can occur.

Imaging is needed for definitive diagnosis, to rule out other causes and prognosis.

Imaging Perspective: Brain MRI along with relevant clinical history has an important role in definitive diagnosis of Acute Neonatal Hypoglycaemic Encephalopathy.

On MRI, in the early stages (< 7 days of hypoglycaemia) there are bilaterally symmetrical areas of restricted diffusion involving parieto-occipital lobes, pulvinar of thalami, splenium of corpus callosum and optic radiations. Other MRI patterns described are injury to posterior white matter, white matter haemorrhages, injury to basal ganglia, thalami and posterior limb of internal capsule (Reference no. 2). These areas appear hypointense on T1 and hyperintense on T2 / FLAIR images. In the later stages, gliosis with cystic encephalomalacic changes and atrophy is seen.

Outcome: Intravenous glucose drip to correct the blood glucose level is used. Prognosis depends mainly upon the severity and duration of hypoglycaemia. In cases of recurrent and persistent hypoglycaemia, long term visual, hearing and cognitive impairment, developmental delay or secondary epilepsy may be seen.

Take-Home Message / Teaching Points: It is important to diagnose hypoglycaemic encephalopathy in early stages. Relevant medical history with early MRI especially the DWI and ADC images are valuable for diagnosis.