The non-contrast CT brain images shown above demonstrate a large hyperdense lesion in the deep gray matter with significant intraventricular extension and ventricular dilation. What is the most likely diagnosis?

Explanation

## Image Findings * Multiple axial non-contrast CT brain images are provided. * A large, irregular, **spontaneously hyperdense lesion** is observed in the deep gray matter, likely involving the thalamus and/or basal ganglia on the patient's left side. * There is clear **intraventricular extension** of this hyperdense material into the lateral and third ventricles. * Significant **dilation of the lateral and third ventricles** is noted, indicating hydrocephalus. * Mild surrounding hypodensity, possibly representing edema, is also present. ## Diagnosis **Key Point:** The presence of a **spontaneously hyperdense lesion** on non-contrast CT in the acute setting is pathognomonic for **acute hemorrhage**. The CT images unequivocally show a large, irregular, hyperdense collection within the brain parenchyma, specifically in the deep gray matter. This hyperdensity is the characteristic appearance of acute blood on non-contrast CT. Furthermore, the blood has ruptured into the ventricular system, leading to intraventricular hemorrhage (IVH). The significant dilation of the lateral and third ventricles indicates obstructive hydrocephalus, a common complication of IVH where blood clots obstruct cerebrospinal fluid (CSF) flow, often at the foramen of Monro or within the aqueduct. ## Differential Diagnosis | Feature | Acute Intracerebral Hemorrhage (ICH) | Acute Ischemic Stroke | Brain Abscess | Glioblastoma Multiforme (GBM) | | :---------------------- | :----------------------------------- | :---------------------------------- | :------------------------------------------ | :---------------------------------------------- | | **Non-contrast CT** | **Hyperdense** lesion | **Hypodense** lesion (acute) | Hypodense center, variable rim (non-contrast) | Heterogeneous, often hypodense with edema | | **Contrast CT** | No enhancement (unless chronic) | No enhancement | Ring enhancement | Irregular ring enhancement, central necrosis | | **Mass Effect** | Present | Variable, less in early stages | Present | Significant | | **Intraventricular Blood** | **Common** | Rare | Absent | Rare (unless tumor hemorrhages) | | **Ventricular Dilation** | Common (obstructive hydrocephalus) | Less common, usually due to edema | Less common | Possible due to mass effect or CSF obstruction | ## Clinical Relevance **Clinical Pearl:** Acute intracerebral hemorrhage often presents with sudden onset of severe headache, focal neurological deficits, nausea, vomiting, and altered consciousness. The clinical presentation's severity correlates with the size and location of the bleed, and the presence of intraventricular extension or hydrocephalus. ## High-Yield for NEET PG **High-Yield:** On non-contrast CT, **acute blood is hyperdense**, subacute blood is isodense, and chronic blood is hypodense. **Key Point:** The most common cause of spontaneous intracerebral hemorrhage in adults is **hypertension**, typically affecting deep structures like the basal ganglia, thalamus, pons, and cerebellum. ## Common Traps **Warning:** Always confirm if the CT is non-contrast when evaluating for acute hemorrhage. Acute ischemic strokes appear hypodense, not hyperdense, on non-contrast CT. ## Reference [cite:Harrison's Principles of Internal Medicine, 20th Ed, Ch 429; Robbins Basic Pathology, 10th Ed, Ch 26]