Intracranial Pressure Monitoring Techniques
🧠 Invasive Techniques (Gold Standard)
Intraventricular Catheter (EVD – External Ventricular Drain)
- Location: Lateral ventricle
- Advantages:
- Gold standard – measures true ICP
- Allows cerebrospinal fluid (CSF) drainage
- Can be recalibrated and zeroed
- Disadvantages:
- Requires anatomical precision
- Risk of infection and hemorrhage
Intraparenchymal Monitor (e.g., Codman, Camino)
- Location: Frontal white matter (brain parenchyma)
- Advantages:
- Easier and faster to place than EVD
- Lower infection rate
- Disadvantages:
- Cannot drain CSF
- Cannot be recalibrated – may drift over time
Subdural / Epidural Sensors
- Location: Subdural or epidural space
- Advantages:
- Less invasive
- Disadvantages:
- Less accurate
- Rarely used today
Subarachnoid Bolt
- Location: Subarachnoid space
- Advantages:
- Moderate accuracy
- Disadvantages:
- Cannot drain CSF
🩺 Non-Invasive Techniques (Adjuncts or Experimental)
Transcranial Doppler Ultrasonography (TCD)
- Measures cerebral blood flow velocity and pulsatility index
- Indirect correlation with ICP
Optic Nerve Sheath Diameter (ONSD) via Ultrasound
- Detects optic nerve sheath dilation due to raised ICP
- Rapid bedside screening tool
MRI / CT-Based Morphometrics
- Measures ventricular size and brain shifts
- Not continuous monitoring
Tympanic Membrane Displacement
- Measures displacement due to CSF pressure transmission to cochlea
- Experimental
📊 Comparative Table
| Parameter | Intraventricular | Intraparenchymal | Non-Invasive |
|---|---|---|---|
| Accuracy | High | High | Low–Medium |
| CSF drainage | Yes | No | No |
| Infection risk | High | Moderate | None |
| Recalibration possible | Yes | No | No |
| ICU use | Yes | Yes | Rare/Adjunct only |