Intracranial Hemorrhages: Imaging and Diagnosis for Students
Intracranial hemorrhages represent a critical neurosurgical emergency, and their accurate and timely diagnosis relies heavily on advanced imaging techniques. Understanding the distinct characteristics of each hemorrhage type on computed tomography (CT) and magnetic resonance imaging (MRI) is crucial for effective patient management and is a fundamental skill for medical students. This guide will break down the imaging features of subdural, epidural, subarachnoid, and intraventricular hemorrhages, making complex concepts easy to grasp.
Understanding Different Types of Intracranial Hemorrhages
Intracranial hemorrhages are broadly classified based on their location within the cranial cavity. Each type has unique origins, anatomical constraints, and imaging presentations. This section will introduce the key distinctions of subdural, epidural, subarachnoid, and intraventricular bleeds.
Subdural Hematoma (SDH): Imaging Essentials
Subdural hematomas are typically venous in origin, resulting from the stretching or tearing of cortical veins that bridge the subdural space to reach the dural sinuses. They can also arise from superficial cerebral arteries. SDHs commonly occur after acute deceleration injuries, such as motor vehicle accidents or falls, and are often associated with other injuries like cortical contusions.
CT Scan Features of Subdural Hematomas:
- Acute SDH: Appears as crescent-shaped extra-axial collections of high attenuation (hyperdense), typically measuring 50 to 60 Hounsfield Units (HU) relative to normal brain (18-30 HU). They are most often supratentorial, along the convexity, falx, and tentorium.
- Important Note: SDHs will not cross dural reflections (like the falx cerebri or tentorium) but can cross sutural margins.
- Occasionally, acute blood may be isodense or hypodense in cases of severe anemia or active extravasation (a