Pitfalls in the diagnosis of subdural hemorrhage – Mimics and uncommon causes

Abstract Purpose Subdural hemorrhage (SDH), the accumulation of blood between the dura and arachnoid mater, is one of the most commonly encountered traumatic findings in emergency radiology setting. The purpose of this essay is to review the pitfalls in the diagnosis of SDH including a) mimics on CT imaging and b) etiology other than accidental trauma. We describe several entities that closely mimic SDH on non-contrast CT scans. A knowledge of these mimics is essential in the emergency setting since overdiagnosis of SDH can lead to unnecessary hospital admissions, potentially invasive procedures, or even delay in necessary treatment. The mimics of SDH on non-contrast head CT include: PATHOLOGIC ENTITIES 1. Cerebral venous thrombosis 2. Dural based benign masses 3. Dural based malignant neoplasms 4. Epidural hematoma 5. Hemorrhage in arachnoid cyst 6. Intracranial hypotension 7. Subdural hygroma 8. Subdural empyema IATROGENIC MIMICS 1. Enhancement of chronic subdural collection after contrast administration 2. Temporalis muscle entrapment under craniotomy flap ANATOMIC/PHYSIOLOGIC MIMICS 1. Cortical veins 2. Dural calcification/thickening 3. Dural enhancement 4. Hyperdense dural venous sinuses ARTIFACTUAL MIMICS 1. Cerebral edema 2. Streak and motion artifact We also briefly review non-accidental and non-traumatic causes of SDH. Although, the most common cause of SDH is accidental trauma, other routinely encountered causes of SDH include coagulopathy, non-accidental trauma, cranial surgery, vascular malformations etc. Conclusion Clinicians dealing with SDH in the emergency setting should consider SDH mimics and less common etiologies of SDH in order to facilitate appropriate patient management.