Confusion recurs 2 weeks after fall
Initial head and neck CT scans following a syncopal episode were unrevealing. Two weeks later, a follow-up scan painted a different picture.
Diagnosis: Delayed acute subdural hematoma
The CT scan (FIGURE 2) revealed an acute on chronic large left frontotemporoparietal and a right frontoparietal subdural hematoma (SDH) with resultant left to right subfalcine herniation. The patient was given a diagnosis of a delayed acute subdural hematoma (DASH)—an acute subdural hematoma that is not apparent on an initial CT scan, but is detected on follow-up CT imaging days or weeks after the injury.1 The incidence of DASH is approximately 0.5% among acute SDH patients who require operative treatment.1
Because DASH is rare, there is a lot of uncertainty surrounding its presentation, pathophysiology, and outcomes. In the few cases that have been described, patients have varied from those who were healthy, and had no coagulation abnormalities, to those who were elderly and taking anticoagulants.2,3 In addition, the period between the head injury and the development of SDH is variable.3
While not much is known about DASH, the mechanism of acute SDH has been widely studied and researched. Acute SDH, which typically follows a head trauma, results from the tearing of bridging veins that lack supporting structures and are most vulnerable to injury when crossing the subdural space.4 The potential pathophysiology for DASH is not completely understood, but is likely to involve subtle damage to the bridging veins of the brain that continue to leak over a matter of hours and days.1,5
Two risk factors to consider. Increasing age and use of oral anticoagulants can increase the risk of developing an intracranial lesion after head injury.3 Due to the infrequency of DASH, the same risk factors for SDH should be considered for DASH. These factors make it increasingly important to establish guidelines on how to approach mild traumatic brain injury (TBI) in both DASH and SDH, especially for those who are elderly or have been on anticoagulation therapy.
Differential Dx
The differential diagnosis for our patient’s decline and altered mentation weeks after the initial event included worsening normal pressure hydrocephalus, cerebrovascular accident, and seizure.
Normal pressure hydrocephalus typically has a more chronic onset than DASH. It manifests with the classic triad of dementia, incontinence, and magnetic or festinating gait (“wild, wet, and wobbly”).
Cerebrovascular accidents are most often associated with focal neurologic deficits, which can be ischemic or hemorrhagic. If hemorrhagic, the hemorrhage is typically parenchymal and not subdural.
Seizure, especially partial complex seizure, can arise after trauma and may not involve obvious motor movements. Symptoms generally abate over a few minutes to hours with treatment. Electroencephalogram and CT scan can differentiate seizure from a subdural hematoma.
