A 52-year-old woman on warfarin for atrial fibrillation presents with acute-onset severe occipital headache, neck stiffness, and altered consciousness. Non-contrast CT head shows a hyperdense lesion in the posterior fossa with hydrocephalus. Which additional investigation is most appropriate to assess for a secondary cause and guide further management?

## Investigation for Secondary Hemorrhage in Posterior Fossa ICH **Key Point:** In a patient with ICH on anticoagulation, CTA is the most appropriate next investigation to identify underlying vascular lesions (aneurysm, AVM, cavernoma, dural venous sinus thrombosis) that may have precipitated the hemorrhage and require specific intervention. ### Clinical Context This patient has: - Anticoagulation (warfarin) — increases risk of spontaneous ICH - Posterior fossa hemorrhage with hydrocephalus — suggests a structural lesion (aneurysm, AVM, or cavernous malformation) - Acute presentation — requires rapid diagnosis to guide neurosurgical intervention ### Role of CTA in ICH Workup **CTA is indicated when:** 1. ICH in an unusual location (posterior fossa, lobar, basal ganglia in young patient) 2. Patient on anticoagulation or antiplatelet therapy 3. ICH with rapid expansion or intraventricular hemorrhage 4. Suspicion of underlying vascular lesion (aneurysm, AVM, cavernoma) **CTA advantages:** - Rapid (5–10 min) and widely available - High sensitivity (>95%) for aneurysms >3 mm - Detects AVMs, cavernomas, and dural sinus thrombosis - Guides neurosurgical planning (clipping vs. coiling vs. observation) ### Comparison of Investigations | Investigation | Detects Aneurysm | Detects AVM/Cavernoma | Detects DVST | Timing | Role in ICH | |---|---|---|---|---|---| | **CTA** | 95% (>3 mm) | Yes | Yes | 5–10 min | **First-line for secondary causes** | | Lumbar puncture | No | No | No | 30 min | Contraindicated (↑ICP, herniation risk) | | EEG | No | No | No | 20 min | For seizures, not diagnosis | | PET brain | No | No | No | 60+ min | Research only; not diagnostic | **Clinical Pearl:** Posterior fossa ICH with hydrocephalus is a neurosurgical emergency. CTA will rapidly identify whether this is a ruptured aneurysm (requiring urgent clipping/coiling), an AVM (requiring endovascular embolization), or a cavernoma (observation if stable). This directs the next step: ICU monitoring, neurosurgical consultation, or emergent intervention. **High-Yield:** CTA is the standard second-line imaging in ICH workup when a secondary cause is suspected. It is faster and safer than conventional angiography and has replaced DSA as the initial diagnostic tool for vascular lesions. **Warning:** Lumbar puncture is contraindicated in acute ICH with mass effect and hydrocephalus because it increases intracranial pressure and risks transtentorial herniation. CSF analysis is not diagnostic for the cause of hemorrhage.