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  Ischemic Stroke – CT Brain (Non-contrast) | Key Radiological Features    1. Hyperacute Phase (0–6 hours) Often subtle / may be normal Dense artery sign (e.g., Dense MCA sign) → acute thrombus Loss of gray–white differentiation Insular ribbon sign Lentiform nucleus obscuration Sulcal effacement (early edema) No hemorrhage (key to thrombolysis decision) 2. Acute Phase (6–24 hours) Hypodense area in vascular territory (wedge-shaped) Cytotoxic edema → ↓ attenuation Progressive loss of gray-white differentiation Mass effect Sulcal effacement Ventricular compression 3. Subacute Phase (1–7 days) Well-defined hypodensity Peak mass effect (3–5 days) Fogging effect (transient normalization ~1–2 weeks) Gyriform (cortical) enhancement (if contrast) ± Hemorrhagic transformation 4. Chronic Phase (>2–3 weeks) Encephalomalacia (CSF density area) Volume loss → ex vacuo ventricular dilatation Gliosis No mass effect High-Yield Signs (Rapid Recall) Dense MCA sign → thrombus Ins...

Radiological features of Raised ICP on CT Brain (in a nutshell) 🧠 Key CT Findings 1. Sulcal effacement Loss/obliteration of cortical sulci Earliest sign of diffuse cerebral edema 2. Ventricular compression Slit-like or reduced size of lateral and third ventricles May progress to near-complete effacement 3. Basal cistern effacement Obliteration of: Suprasellar cistern Perimesencephalic cistern Ambient cistern Strong indicator of significant ICP rise 4. Midline shift Displacement of septum pellucidum Indicates mass effect (quantify in mm) 5. Diffuse cerebral edema Loss of gray–white matter differentiation Generalized hypodensity of brain parenchyma 6. Herniation signs Subfalcine → cingulate gyrus shift under falx Uncal (transtentorial) → medial temporal lobe displacement Tonsillar → cerebellar tonsils descending (better on MRI but indirect CT signs present) 7. Effacement of CSF spaces Narrowing/obliteration of: Cortical sulci Ventricles Cisterns 🔑 Compact Mnemonic “SVeB MeD Her” S ...

  Pneumocephalus — CT Brain (Key Radiological Features) 1. Density Very low attenuation (black) HU ≈ −1000 (air) 2. Typical Locations Subdural (most common) Epidural Intraventricular Intracerebral / intraparenchymal Subarachnoid / cisternal 3. Characteristic Signs Mount Fuji sign (tension pneumocephalus) → Separation + compression of frontal lobes by subdural air Air bubble / multiple loculi sign → Scattered small air pockets Air-fluid level → Suggests CSF leak or communication 4. Mass Effect (if tension) Sulcal effacement Ventricular compression Midline shift Frontal lobe compression 5. Distribution Pattern Clues Non-dependent air (rises anteriorly/superiorly) Often frontal region in supine CT May outline cisterns → “negative contrast effect” 6. Associated Findings Skull base fracture Postoperative changes (craniotomy) Sinus/mastoid air communication CSF leak One-line clinical correlation Simple pneumocephalus → incidental, small, no mass effect Tension pneumocephalus → neuro...

  Radiological features of hydrocephalus on CT brain (concise) 1) Ventricular dilatation (core feature) Enlargement of lateral ventricles (rounded frontal horns) Dilated 3rd ventricle ± Dilated 4th ventricle (helps localize obstruction) Temporal horns early dilatation (sensitive early sign) 2) Disproportionate ventriculomegaly Ventricles enlarged out of proportion to cortical sulci Helps differentiate from cerebral atrophy (where sulci also enlarged) 3) Periventricular lucency (transependymal CSF seepage) Hypodense rim around ventricles Indicates raised intraventricular pressure 4) Effacement of cortical sulci & cisterns Sulcal effacement (compressed brain parenchyma) Basal cisterns may be compressed 5) Ballooning of ventricular horns Frontal and occipital horns become rounded/bulbous Loss of normal concavity 6) Signs suggesting type (useful clinically) Obstructive (non-communicating): Dilatation proximal to block e.g., enlarged lateral + 3rd ventricle, normal 4th → aquedu...

  Midline Shift on CT Brain — Key Radiological Features (Concise) 1. Septum Pellucidum Displacement (Most sensitive marker) Shift from midline (measured at level of foramen of Monro ) Quantified in mm (clinically significant ≥5 mm) 2. Third Ventricle Shift Deviated from midline Often compressed or slit-like 3. Pineal Gland Displacement Normally midline → shift indicates deep central displacement Useful when calcified (acts as a marker) 4. Lateral Ventricle Asymmetry Ipsilateral ventricle: compressed Contralateral ventricle: dilated (± obstructive hydrocephalus) 5. Effacement of Sulci Loss of cortical sulci on affected side due to mass effect 6. Subfalcine Herniation (Cingulate Shift) Cingulate gyrus displaced under falx cerebri Often accompanies significant MLS 7. Basal Cistern Compression Indicates raised ICP and possible transtentorial progression Measurement (Standard) Distance between: Ideal midline (line through falx) Actual septum pellucidum position Clinical Correlation Thr...

  Depressed Skull Fracture — CT Brain (Non-contrast) Key radiological features: 1. Bony Abnormality Inward displacement of skull fragment(s) below adjacent inner table Step defect in calvarium Often comminuted fragments Best seen in bone window 2. Depth Criteria (Clinical relevance) Depression > thickness of adjacent skull → significant Associated with higher risk of dural tear & brain injury 3. Intracranial Complications Underlying contusion / intracerebral hemorrhage Extradural hematoma (EDH) Subdural hematoma (SDH) Subarachnoid hemorrhage (SAH) Pneumocephalus (air entry) 4. Soft Tissue Findings Scalp swelling / hematoma Possible foreign body (in compound fractures) 5. Dural / Brain Involvement Dural breach (suggested by pneumocephalus or deep fragment) Brain laceration in severe cases 6. Special Situations Open (compound) fracture → air, contamination Over venous sinus → risk of sinus injury/thrombosis Frontal sinus involvement → CSF leak risk One-line summary: ...

Skull Fracture (Non-depressed) — CT Brain Features  1. Linear (most common) Thin radiolucent line in bone window Sharp, non-sclerotic margins Often crosses vascular grooves (vs grooves: branching, sclerotic margins) May cross sutures (vs sutures: serrated, symmetric) No displacement or depression 2. Diastatic fracture Widening of cranial sutures beyond normal Common in children Typically along coronal, sagittal, lambdoid sutures 3. Comminuted (non-depressed) Multiple intersecting fracture lines Bone fragmented but no inward displacement 4. Basilar skull fracture Often indirect signs predominate : Pneumocephalus Air-fluid levels in paranasal sinuses Opacification of mastoid air cells Fracture line may be subtle (bone window essential) Common sites: temporal bone, sphenoid, occipital base General CT Clues (All Types) Best seen in bone window Look for overlying scalp swelling/hematoma Assess for associated intracranial injury (EDH, SDH, contusion) Use multiplanar reconstructions ...

  Intracerebral Hemorrhage (ICH) — CT Brain (Non-contrast) Key radiological features (concise): 1. Hyperdense Intraparenchymal Lesion Acute blood = hyperdense (bright) (≈60–80 HU) Common sites: basal ganglia (putamen), thalamus, lobar, cerebellum, brainstem 2. Surrounding Edema Hypodense rim around hematoma (perihematomal edema) Develops within hours → increases over days 3. Mass Effect Effacement of sulci, ventricles Midline shift (quantify if needed) Compression of adjacent structures 4. Intraventricular Extension Hyperdense blood in ventricles May show fluid–fluid level / layering Risk of acute hydrocephalus 5. Shape & Margins Typically irregular or round/oval May have heterogeneous density (active bleed, clot retraction) “Swirl sign” → hypodense areas within clot (ongoing bleeding) 6. Location Clues (Etiology hint) Deep (putamen/thalamus) → hypertensive Lobar → amyloid angiopathy, tumor, AVM Multiple → metastasis, coagulopathy 7. Evolution (brief) Hyperacute (0–6 h):...

Subarachnoid Hemorrhage (SAH) — CT Brain (Non-contrast) Core radiological features (concise): 1) Hyperdensity in subarachnoid spaces Acute blood appears  hyperdense (bright) Typical locations: Basal cisterns  (suprasellar, interpeduncular, ambient) Sylvian fissures Interhemispheric fissure Cortical sulci 2) “Star sign” (basal cistern pattern) Star-shaped hyperdensity in  basal cisterns around Circle of Willis Classic for  aneurysmal SAH 3) Sulcal effacement with hyperdense sulci Blood outlines sulci →  prominent hyperdense cortical sulci May coexist with  early cerebral edema → sulcal effacement 4) Intraventricular extension (common) Hyperdensity within ventricles (especially  occipital horns ) May show  fluid–fluid levels 5) Hydrocephalus Acute obstructive or communicating hydrocephalus Findings: Ventricular dilatation Periventricular lucency (transependymal CSF seepage) 6) Loss of gray–white differentiation (severe cases) Due to  global cer...

  Subdural Hematoma (SDH) — CT Brain (Non-contrast) Key Features Typical Appearance 1. Shape & Location Crescent-shaped (concavo-convex)  extra-axial collection Lies  between dura and arachnoid Crosses sutures , but  does NOT cross midline  (limited by falx/tentorium) 2. Density (depends on age) Acute (0–3 days):  Hyperdense (bright) Subacute (3–21 days):  Isodense → may be subtle (“ CT occult ”) Chronic (>3 weeks):  Hypodense (dark) Mixed density:  Rebleed → fluid-fluid levels / layering 3. Mass Effect Sulcal effacement Midline shift Compression of ventricles Possible  subfalcine / transtentorial herniation 4. Internal Characteristics Homogeneous  (acute) or  heterogeneous  (chronic/rebleed) May show  septations/membranes  (chronic SDH) 5. Associated Findings Underlying cerebral edema Cortical contusions Skull fracture less common  than in EDH High-yield Differentiation (SDH vs EDH) SDH:  Cresce...

Normal CT Brain (Non-contrast) — Key Radiological Features (Concise)   1. Symmetry Bilateral cerebral hemispheres symmetrical No midline shift Falx cerebri in midline 2. Grey–White Matter Differentiation Clear distinction: Grey matter (cortex, basal ganglia) → slightly hyperdense White matter → slightly hypodense Preserved corticomedullary junction 3. Ventricular System Lateral, 3rd, 4th ventricles: Normal size and configuration Symmetrical No dilatation or compression 4. Cisterns & Sulci Basal cisterns ( suprasellar, ambient, quadrigeminal ) → open and well-defined Cortical sulci: Normal for age No effacement (→ edema) or prominence (→ atrophy) 5. Basal Ganglia & Thalami Normal density and symmetry No focal hypo/hyperdense lesions 6. Brainstem & Cerebellum Normal size, contour, and density No focal lesion or compression 7. No Abnormal Densities No: Hyperdensity → hemorrhage Hypodensity → infarct/edema No calcification (except physiological: pineal, choroid plexus) 8....