Head CT: The Basics Stephen Magill Radiology Rotation August, 2012

Computed Tomography: Intro Uses X-Rays (radiation) to create cross sectional images (tomographs) through the human body Findings are always described based in relative “densities” (vs MRI “intensity”)

CT: Relative Density Bright (High Density) Dark (Low Density) Bone Contrast Acute Blood Soft Tissue: Gray matter White matter Water Fat Air Bone is

How To Describe A Head CT Always start with this sentence: “This is a [non-contrast vs contrast enhanced] [axial vs sagittal vs coronal] head CT showing…”

Normal Axial Head CT TOP (Superior) BOTTOM (Inferior) 23 yr old

Important Places to look: Basilar Cistern B Ventricle Size Make sure no hydrocephalus - Evans ratio (A/B) < 0.3 Also check temporal horns Cisterns Should be plenty of CSF (Black space) No blood/compression

Lesion Location: Intra- vs Extraparenchymal Intraparenchymal: Located within brain tissue Extraparenchymal: Located within the bony casing of CNS BUT outside the brain tissue itself

Lesion Location: Extraparenchymal Two examples of meningioma Extraparenchymal tumor (not in the brain tissue) The tumor is slow growing which is reflected in by the mild displacement of the other brain structures; acute extraparenchymal lesions (bleeds) will cause marked displacement or herniation

Lesion Location: Intraparenchymal Two examples of glioblastoma Intraparenchymal tumor (within the brain tissue) Dark regions (gray arrow) within the tumor are necrotic cavities

Head CT in Acute Situation Anytime someone has head trauma with altered mental status they should have a head CT You are looking for acute blood, which is bright All MD’s should know what acute blood looks like and be able to describe its general location: Epidural Subdural Subarachnoid (SAH) Intraventricular (IVH) Intraparaenchymal (IPH) Location (Cause) Between Skull and Dura (Trauma) Between Dura and Arachnoid (Trauma) Cisterns or Sulci (Trauma, Aneurysm rupture) Ventricles (Trauma, HTN hemorrhage) Brain Tissue (Tra./Tmor, HTN hem) OUT IN

Locations of blood around/in the brain

Locations of blood around/in the brain IPH

Examples of bleeding in different locations EDH Blood spread limited by suture lines Midline shift IPH SAH filling sulci SDH Blood crosses suture lines Calcified choroid Plexus (normal) IVH Saatman et al (2008) J Neurotrauma

Examples of bleeding in different locations IVH

Examples of bleeding in different locations SAH in the basilar cistern and extending out into the fissures A classic CT after rupture of a Circle of Willis aneurysm So called “Star of Death”

Considering hypertensive hemorrhage Head CT shows… Case example 68 y/o female brought in by ambulance to ED after rapid mental status deterioration Obtunded on exam BP: 210/106 Considering hypertensive hemorrhage Head CT shows…

Try to describe it as you would present it. Case example What do you see? Try to describe it as you would present it.

Case example “This is a non-contrast, axial head CT showing… Surrounding soft tissue edema (dark areas) Midline shift IPH “This is a non-contrast, axial head CT showing… …a large left-sided intraparenchymal hemorrhage with surrounding edema and significant midline shift”

Case example “This is a non-contrast, axial head CT showing… Surrounding soft tissue edema (dark areas) Midline shift IPH “This is a non-contrast, axial head CT showing… …a large left-sided intraparenchymal hemorrhage with surrounding edema and 2.2 cm of midline shift”

Case example “This is a non-contrast, axial head CT showing… More caudal slice of previous axial head CT Herniating Uncus Notice the lack of space where the basilar cistern should be; it is filled with brainstem Inferior portion of IPH “This is a non-contrast, axial head CT showing… …a large left-sided intraparenchymal hemorrhage with surrounding edema and 2.1 cm of midline shift. There is also left sided uncal herniation and compression of the basilar cistern due to likely brainstem herniation.”

Taken to OR for clot evacuation Post op-head CT shows… Case Example Taken to OR for clot evacuation Post op-head CT shows…

Case Example Pneumocephalus Markedly improved midline shift Drain Some new IVH Residual IPH Removal of the majority of the clot and improvement in midline shift. Also notice the drain that is left in place. Pneumocephalus (air in the head) is also present, a normal post-operative finding

Case Example Decompression allows improvement in herniation Basilar cistern is now open and decompressed Pneumocephalus where inferior portion of IPH was located Decompression allows improvement in herniation Basilar cistern now wide open Neurological exam improved post-operatively

The End