Somatosensory evoked potentials in neonates with hypoxic-ischemic encephalopathy treated with hypothermia

Somatosensory evoked potentials (SEPs) are reported to have high positive predictive value (PPV) for neurodevelopmental impairment (NDI) in neonates with moderate or severe hypoxic-ischemic encephalopathy (HIE). Our objective was to assess if this predictive value remains high with the use of therapeutic hypothermia.

A cohort of HIE neonates treated with hypothermia was recruited between September 2008 and September 2010. SEPs were elicited after hypothermia and classified as bilateral absent N19, abnormal N19 (i.e., delayed or unilateral absent), or normal. Qualitative evaluation of MRI was also performed. The primary outcome was moderate or severe NDI around 2 years of age.

SEPs were performed after hypothermia in 26 of 34 neonates submitted to hypothermia with adequate follow-up at a median day of life 11 (IQR 9, 13). Twenty-three (88%) had moderate encephalopathy. Eleven neonates (42%) had bilateral absent N19, 4 of whom had NDI, while fifteen neonates (58%) had either abnormal or normal N19, of whom only one had NDI. SEPs thus had a PPV of 0.36 (4/11) and a negative predictive value (NPV) of 0.93 (14/15). Eighteen neonates (69%) had brain injury on MRI. MRI thus had a PPV of 0.28 (5/18) and an NPV of 1.00 (8/8).

Neonates with HIE treated with hypothermia with bilateral absent N19 potentials may have a better prognosis than reported in the pre-hypothermia era. MRI also had a low PPV and high NPV. SEPs should be interpreted with caution in this new population and need to be re-evaluated in larger studies.