Holohemispheric Hemorhhage in Infantile Acute Subdural Hematoma: Serial Neuroimaging Analysis

Background: An acute subdural hematoma (ASDH) in infants without any external sign of trauma is differently recognized as shaken baby syndrome (SBS) / abusive head trauma (AHT) in the United States or as infantile acute subdural hematoma (IASDH) due to minor head trauma in Japan. The present case report aimed to demonstrate that IASDH can occur after a mild head impact if the dural border cell layer is disrupted in an infant with cranio-cerebral disproportion (CCD). Case description: A 5-month-old, male patient fell from a baby bed and struck his occiput against a mat. He began to cry and soon thereafter demonstrated signs of altered consciousness. He was taken to a pediatric hospital where computed tomography (CT) revealed a thin subdural hematoma (SDH) surrounding the entire right cerebral hemisphere. Fundoscopy found a right-sided retinal hemorrhage. Magnetic resonance imaging (MRI) on hospital day 4 revealed a thin, high-intensity ASDH surrounding the entire, cerebral convexity on the right side. In addition, benign enlargement of the subarachnoid space (BESS) and large sylvian fissure (LSF) were noted. On hospital day 12 and 18, follow-up MRI revealed a residual SDH with minimal reduction. The patient had an uneventful clinical course and met all the normal, developmental milestones as of his current age of 3 years. Conclusion: The present case is invaluable because it demonstrates that ASDH can occur as a result of a mild, occipital impact. Particularly relevant here is the thin, holohemispheric appearance of the hematoma on neuroimaging studies, which has been suitably termed, holohemispheric subdural hematoma (HHSDH). Also noteworthy is the long-term presence of the HHSDH with minimal reduction of the SDH. The HHSDH may be caused by entrapment of the hematoma in the dural border cell layer in the absence of any communication with the surrounding structures.