A 35-year-old woman is admitted with a severe head injury (GCS 8/15) following a fall from height. Initial non-contrast CT head shows a right acute subdural hematoma with 8 mm midline shift. She is intubated and sedated. Her pupils are equal and reactive. Six hours later, her left pupil becomes dilated and unreactive. What is the most appropriate next investigation to assess the progression of injury?

Explanation

## Investigation of Choice in Deteriorating Head Injury **Key Point:** Repeat non-contrast CT head is the most appropriate investigation when there is clinical deterioration (anisocoria, change in GCS, pupillary changes) in a patient with known intracranial injury. It provides rapid assessment of hematoma expansion, herniation, and need for emergency neurosurgical intervention. ### Clinical Context: Herniation Syndrome Anisocoria (dilated left pupil) in a patient with right subdural hematoma suggests **uncal herniation** with compression of the ipsilateral oculomotor nerve (CN III). This is a **neurosurgical emergency** requiring immediate imaging to confirm hematoma expansion and guide surgical evacuation. ```mermaid flowchart TD A[Head injury with known SDH]:::outcome --> B{Clinical deterioration?}:::decision B -->|Anisocoria, GCS drop| C[Repeat CT head STAT]:::action B -->|Stable neuro exam| D[Observe, monitor ICP]:::action C --> E{Hematoma expansion?}:::decision E -->|Yes| F[Emergency neurosurgery]:::urgent E -->|No| G[Reassess, continue monitoring]:::action ``` ### Why Repeat CT is Superior | Investigation | Role in Deterioration | Speed | Specificity | |---|---|---|---| | **Repeat CT head** | Confirms hematoma expansion, herniation, need for surgery | **Immediate** | **Highest** | | **TCD ultrasound** | Assesses cerebral blood flow, not diagnostic for hematoma | 10–15 min | Low for acute bleed | | **ICP monitoring** | Measures pressure, does not identify cause | Continuous | Indirect | | **EEG** | Detects seizures, not diagnostic for hematoma | 30+ min | Not relevant | **High-Yield:** In a patient with known intracranial hemorrhage and acute neurological deterioration (especially pupillary changes), **repeat CT is mandatory** before any other investigation. It directly answers the question: "Is the hematoma expanding and causing herniation?" ### Clinical Pearl Anisocoria (unequal pupils) is a **red flag** for uncal herniation. The dilated pupil is on the side of the mass (ipsilateral). This patient requires **emergent CT and neurosurgical consultation**—not just monitoring. **Warning:** Do not waste time with TCD, EEG, or ICP monitoring when there is clinical evidence of herniation. Repeat imaging is the priority.