Lucid interval in abusive head trauma: a systematic review

BACKGROUND: Abusive head trauma (AHT) is a major cause of infant morbidity and mortality but remains a challenging diagnose, as a clear history of trauma is often lacking and witnesses are usually limited to the perpetrator. Because several caregivers may attend to the same child, determining the timing of injury is crucial for identifying the offender. Among the approaches used to establish timing, the existence of a "lucid interval" between trauma and symptom onset remains controversial. OBJECTIVE: To systematically reviewed the existing literature on the presence or absence of a lucid interval between AHT and symptom onset. PARTICIPANTS AND SETTING: Eligible studies included children evaluated for AHT in whom both the timing of trauma and the onset of symptoms were reported. METHODS: MEDLINE, EMBASE and Google Scholar were systematically searched for articles published up to 2026. RESULTS: 16 studies were included: 5 case-reports or case-series, 10 retrospective studies and 1 systematic review published in 1995. Differences between studies mainly reflected how a lucid interval was defined. Studies reporting immediate symptoms defined the interval as the time to any symptoms, even nonspecific ones (e.g. vomiting, lethargy, irritability), whereas others often considered the delay to specific neurological signs such as seizures or loss of consciousness. CONCLUSIONS: Despite the low level of evidence of the included studies, this review suggests that symptoms occur immediately at the time of AHT, although early nonspecific signs may initially be overlooked. When combined with other methods, these findings may help experts determine the timing of AHT.