Seizures are common in newborn infants with hypoxic-ischemic encephalopathy and are highly associated with adverse neurodevelopmental outcomes. The impact of seizure activity on the developing brain and the most effective way to manage these seizures remain surprisingly poorly understood, particularly in the era of therapeutic hypothermia. Critically, the extent to which seizures exacerbate brain injury or merely reflect the underlying evolution of injury is unclear. Current anticonvulsants, such as phenobarbital and phenytoin have poor efficacy and preclinical studies suggest that most anticonvulsants are associated with adverse effects on the developing brain. Levetiracetam seems to have less potential neurotoxic effects than other anticonvulsants but may not be more effective. Given that therapeutic hypothermia itself has significant anticonvulsant effects, randomized controlled trials of anticonvulsants combined with therapeutic hypothermia, are required to properly determine the safety and efficacy of these drugs. Small clinical studies suggest that prophylactic phenobarbital administration may improve neurodevelopmental outcomes compared to delayed administration; however, larger high-quality studies are required to confirm this. In conclusion, there is a distinct lack of high-quality evidence for whether and to what extent neonatal seizures exacerbate brain damage after hypoxia-ischemia and how best to manage them in the era of therapeutic hypothermia.

Perinatal brain injury secondary to hypoxia-ischemia and/or infection/inflammation remains a major cause of disability. Therapeutic hypothermia significantly improves outcomes, but in randomized controlled trials nearly half of infants still died or survived with disability, showing that additional interventions are needed. There is growing evidence that brain injury spreads over time from injured to previously uninjured regions of the brain. At least in part, this spread is related to opening of connexin hemichannels and pannexin channels, both of which are large conductance membrane channels found in many brain cells. Opening of these membrane channels releases adenosine triphosphate (ATP), and other neuroactive molecules, into the extracellular space. ATP has an important role in normal signaling, but pathologically can trigger the assembly of the multi-protein inflammasome complex. The inflammasome complex promotes activation of inflammatory caspases, and release of inflammatory cytokines. Overall, the connexin hemichannel appears to play a primary role in propagation of injury and chronic disease, and connexin hemichannel blockade has been shown to be neuroprotective in multiple animal models. Thus, there is potential for some blockers of connexin or pannexin channels to be developed into targeted interventions that could be used in conjunction with or separate to therapeutic hypothermia.

Hypoxic–ischaemic encephalopathy (HIE) is a major cause of neonatal brain injury and is associated with a high rate of death and lifelong disability. Its pathogenesis is still poorly understood, and there is no proven treatment for preterm infants. Therapeutic hypothermia for term and near-term infants partially improves outcomes, highlighting the need to target additional mechanisms. This review evaluates evidence that necrosis and necroptosis contribute materially to evolving brain injury in both term and preterm brains. Serial imaging studies suggest that lesions typically develop over many days after birth for term infants and over many weeks after birth for preterm infants. Growing evidence from animal studies shows that severe white matter injury can be mediated by programmed necroptosis. In particular, lesions that evolve late after acute HI are characterised by necrosis in association with agglomerations of microglia, with little apoptotic cell death. Critically, preclinical studies in large and small animals show that outcomes can be dramatically improved by very delayed intervention after HI including with cell therapy, anti-inflammatory agents, and endogenous neurotrophins. These findings strongly support the hypothesis that there may be a window of therapeutic opportunity for days or even weeks after birth to prevent delayed necrotic lesions.

Perinatal hypoxic–ischemic encephalopathy (HIE) is a condition resulting from oxygen deprivation around the time of birth and may be associated with death, brain damage, and disability. Alongside this, studies have shown that HIE may result in visual impairment. Previously, this was thought to be due to damage to the visual pathways in the brain, in a condition known as cerebral visual impairment. However, recent studies suggest that direct injury to the retina may occur after HIE. Of note, the nucleotide-binding domain, leucine-rich-containing family, and pyrin domain-containing-3 (NLRP3) inflammasome is thought to play a role in perpetuating inflammatory damage in the brain after hypoxia–ischemia (HI). As such, this study aimed to characterize retinal inflammation and the role of the NLRP3 inflammasome after HI using a modified Rice-Vannucci model in postnatal day 10 (P10) rat. Eighteen Sprague-Dawley rats were allocated evenly to three groups. Two groups received surgery to ligate the right common-carotid artery and induce HI, while another group received only sham surgery. Rats exposed to HI received subcutaneous injections of tonabersat (HI + Ton) or saline (HI + vehicle) at 1, 24 and 48 h after HI, and were culled at P17 for analysis. The results showed that the protein expression of GFAP, Iba-1, NLRP3, caspase-1 and connexin43 increased in the retina at 7 d after HI-vehicle compared with sham surgery, much more so in the ipsilateral = than the contralateral retina. Furthermore, = inflammasome components NLRP3, cleaved caspase-1 and connexin43 were significantly upregulated in the ipsilateral retina following HI-vehicle compared to the sham surgery group. Treatment with a connexin43 hemichannel blocker, tonabersat, significantly decreased the expression of the inflammasome markers, cleaved caspase-1 and connexin43, and diminished Iba-1+ cell infiltration in the ipsilateral retina. These findings suggest that direct retinal damage and inflammation may occur after HI. Furthermore, these inflammatory changes are likely mediated and propagated by activation of the NLRP3 inflammasome. Importantly, inhibition of the inflammasome by tonabersat may be able to inhibit retinal inflammation and damage, potentially preventing visual impairment after HI. Further investigation in humans is required to determine the efficacy of tonabersat in treating hypoxic–ischemic injuries to the brain and eye.