Neonatal Hyperekplexia: Is It Still a Diagnostic Challenge? Evidence From a Systematic Review.

Hyperekplexia is a neurologic disorder characterized by an exaggerated startle reflex in response to different types of stimuli. Hyperekplexia is defined by the triad of neonatal hypertonia, excessive startle reflexes, and generalized stiffness following the startle. Although uncommon, hyperekplexia can lead to serious consequences such as falls, brain injury, or sudden infant death syndrome.Aim of this study was to identify cases of neonatal hyperekplexia with a confirmed genetic diagnosis and to establish the genotype-phenotype correlation at onset. Articles were selected from 1993 to 2024 and PRISMA Statement was applied including newborns within 28 days of life. So, we retrieved from literature 14 cases of genetically confirmed neonatal hyperekplexia. The onset of clinical manifestations occurred in the first day of life in 8 of 14 patients (57.14%). Clinical findings were muscle stiffness (100%), startle reflex (66.66%), apnea/cyanosis (41.66%), positive nose-tapping test (33.33%), jerks (33.33%), jitteriness (25%), and ictal blinking (25%). Genes involved were in 9 of 14 (64.28%), in 2 of 14 (14.28%), in 1 of 14 (7.14%), and in 2 of 14 (14.28%). Patients showed heterozygous (66.66%) or homozygous (33.33%) status. In 7 of 14 cases (50%), the condition occurred in other family members. A genotype-phenotype correlation was not achievable.Timely diagnosis is crucial to improve the natural history of hyperekplexia avoiding/reducing possible major complications such as sudden infant death syndrome, brain injury, and serious falls. Early differentiation from epilepsy minimizes treatment cost and improves the quality of life of patients.