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CT Brain Analysis - Non-Contrast Head CT (NCCT)
⚠️ IMPORTANT DISCLAIMER: This analysis is for educational/informational purposes only. Clinical decisions must be made by qualified physicians with direct patient assessment.
Primary Diagnosis: Acute Cerebellar (Posterior Fossa) Intraparenchymal Hemorrhage with Acute Obstructive Hydrocephalus
Systematic CT Findings
1. Posterior Fossa - Primary Lesion
A large, well-defined, homogeneously hyperdense mass is visible in the posterior fossa on the lower axial slices. Key features:
- Location: Centered in the cerebellar vermis with extension into both cerebellar hemispheres (left > right)
- Density: ~60-80 Hounsfield Units (HU) - consistent with acute blood (hyperacute/acute intraparenchymal hematoma)
- Size: Appears to be ≥4 cm in maximum diameter, placing it in the highest-risk category
2. Fourth Ventricle
- The fourth ventricle is completely effaced/compressed by the hematoma
- This is the mechanism of obstructive hydrocephalus (CSF cannot flow from the 3rd to 4th ventricle and out through the foramina of Luschka/Magendie)
3. Ventricular System - Acute Obstructive Hydrocephalus
Marked dilatation of the entire supratentorial ventricular system:
- Lateral ventricles: Markedly enlarged bilaterally (frontal, temporal, and occipital horns)
- Temporal horns: Prominently dilated - a sensitive early sign of raised ICP
- Third ventricle: Dilated
- Transependymal edema: Bilateral periventricular hypodensity (dark halos) around the frontal horns of the lateral ventricles, indicating transependymal CSF seepage - a sign of acute, high-pressure hydrocephalus
4. Posterior Fossa Cisterns
The quadrigeminal, prepontine, and cerebellopontine angle cisterns are effaced/obliterated due to mass effect from the hematoma - a sign of critically elevated posterior fossa pressure.
5. Supratentorial Parenchyma
- No midline shift (symmetric supratentorial dilatation)
- No additional supratentorial hemorrhage identified
- Cortical sulci are flattened/reduced in the upper slices, consistent with raised ICP
6. Lateral Scout View (top-left thumbnail)
A lateral skull radiograph is visible showing normal calvarium with no obvious fracture.
Summary of Findings
| Finding | Detail |
|---|---|
| Primary lesion | Acute cerebellar intraparenchymal hematoma (vermis + hemispheres, left > right) |
| Estimated size | ≥4 cm (high-risk threshold) |
| 4th ventricle | Completely compressed / obliterated |
| Hydrocephalus | Acute obstructive, marked, bilateral symmetric ventricular dilatation |
| Transependymal edema | Present bilaterally - sign of acute high-pressure hydrocephalus |
| Cistern effacement | Posterior fossa cisterns effaced - critical posterior fossa herniation risk |
| Midline shift | Absent |
Clinical Significance & Management Implications
This is a neurosurgical emergency. Key management points from the literature:
Surgical Thresholds:
- Hematomas ≥4 cm or those in the vermis carry the highest risk; many surgeons recommend evacuation regardless of clinical status at this size
- Posterior fossa craniotomy with hematoma evacuation is the generally accepted treatment - it is more important than simply draining the ventricles alone
- The degree of quadrigeminal/perimesencephalic cistern obliteration (present here) is a key surgical indicator
Hydrocephalus:
- Acute obstructive hydrocephalus from 4th ventricle compression requires urgent treatment - an external ventricular drain (EVD) may be needed emergently
- However, EVD alone is inadequate; posterior fossa decompression addresses the root cause
Clinical Decision Points (per Adams & Victor's Principles of Neurology):
- A stuporous or arrhythmically breathing patient should be intubated and taken to the OR within hours
- Once coma and pupillary changes occur, prognosis is very poor even with surgery
- Transient medical stabilization with mannitol and hyperventilation may be used as a bridge to surgery
Poor Prognostic Factors:
- Hematoma size (this appears large/critical)
- Herniation signs (cistern effacement present)
- Degree of hydrocephalus (marked here)
- Altered consciousness
- 28-38% of patients show hematoma expansion within 3 hours; hematoma expansion is associated with a 5x increase in poor outcomes
Common Etiologies to Consider:
- Hypertensive hemorrhage (most common, 32-73% of patients have HTN)
- Amyloid angiopathy
- AVM
- Coagulopathy (14% of cases)
Differential for Hyperdense Posterior Fossa Mass
| Dx | Features |
|---|---|
| Acute intraparenchymal hemorrhage | Most likely - homogenous hyperdensity, mass effect, no rim enhancement |
| Hemorrhagic metastasis | Usually ring-enhancing on contrast; may be heterogeneous |
| Cerebellar abscess | Typically hypodense with ring enhancement |
| Medulloblastoma with hemorrhage | Usually midline, hyperdense in children |
Most consistent with: Spontaneous acute cerebellar intraparenchymal hemorrhage (hypertensive etiology most likely given demographics).
Sources: Adams and Victor's Principles of Neurology, 12th Ed., p.849; Symptom to Diagnosis: An Evidence Based Guide, 4th Ed.; Lobo et al. 2025 meta-analysis (PMID 39969621) comparing minimally invasive neuroendoscopic vs. open surgery for spontaneous cerebellar hemorrhage.
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