Infant traumatic brain injury with a biphasic clinical course and late diffusion restriction: a case report.

Traumatic brain injury (TBI) in young children can rarely exhibit a biphasic clinical course with delayed neurological deterioration. We report a 2-year-old boy who fell from 50 cm and briefly lost consciousness with vomiting, initially found to have a right frontotemporoparietal acute subdural hematoma (SDH) with midline shift but no brain contusions. After transient stabilization, he developed new left-sided limb weakness and status epilepticus on day 3 post-injury. Follow-up diffusion-weighted magnetic resonance imaging (DWI) revealed a characteristic "bright tree" pattern of bilateral subcortical white matter diffusion restriction with corresponding decreased apparent diffusion coefficient (ADC) values. Electroencephalography showed generalized slowing with interictal focal epileptiform discharges. The patient was managed with antiepileptic therapy and supportive care. He demonstrated steady improvement and achieved near-complete neurological recovery by 9-month follow-up. This biphasic presentation-early trauma and late-onset seizures with diffusion restriction-is consistent with Traumatic brain injury with a biphasic clinical course and late reduced diffusion (TBIRD). Early recognition of TBIRD is crucial, as it resembles acute encephalopathy with biphasic seizures and late diffusion changes, and likely stems from secondary excitotoxic injury. Timely intervention in our case was associated with a favorable outcome, underscoring the importance of vigilant monitoring for delayed neurologic sequelae in pediatric TBI.