How to assess intracranial pressure (ICP) in patients with a history of traumatic brain injury, stroke, or other neurological conditions, considering factors such as age, medical history, and underlying conditions like hypertension or diabetes?

How to Assess Intracranial Pressure (ICP)

Direct ICP Measurement: The Gold Standard

ICP cannot be reliably estimated from clinical features or CT findings alone and must be directly measured using invasive monitoring devices. 1, 2

Invasive Monitoring Methods

• Intraventricular catheters (external ventricular drains) are the preferred method as they both measure ICP and allow therapeutic CSF drainage 3, 4
• Intraparenchymal fiberoptic monitors placed within brain parenchyma provide continuous ICP readings and are typically used when high suspicion of elevated ICP exists or in clinically deteriorating patients 3, 4
• Both devices require invasive brain catheter placement and provide real-time pressure measurements, with ICP >20 mmHg sustained defining intracranial hypertension 4, 5

Indications for Invasive ICP Monitoring

Place ICP monitors in patients with Glasgow Coma Scale (GCS) ≤8 AND abnormal CT scan findings. 1

Additional indications include:

• Signs of high ICP on brain CT scan (compression/absence of basal cisterns, disappearance of ventricles, midline shift >5 mm, hematoma >25 mL) 1
• Patients requiring extracranial surgical procedures (except life-threatening emergencies) 1
• Do NOT place monitors if initial CT is completely normal with no clinical severity indicators and no transcranial Doppler abnormalities 1

Indirect Assessment Methods

CT Imaging Findings

While CT does not measure ICP directly, it identifies radiographic signs correlating with elevated ICP 1:

• Compression or absence of basal cisterns correlates with ICP >30 mmHg in >70% of cases 1
• Disappearance of cerebral ventricles indicates elevated pressure 1
• Midline shift >5 mm suggests significant mass effect 1
• Intracerebral hematoma volume >25 mL associates with elevated ICP 1
• Traumatic subarachnoid hemorrhage increases risk of intracranial hypertension 1

Transcranial Doppler Sonography

• Provides non-invasive assessment of mass effect and ICP changes through waveform analysis 3
• Decreased diastolic velocity and increased pulsatility index indicate elevated ICP and decreased cerebral perfusion pressure 3
• Requires confirmation by other means, as increased pulsatility index may reflect either intracranial hypertension or mass effect 3

Clinical Assessment

Neurological Monitoring

Assess neurological status frequently using standardized scales:

• National Institutes of Health Stroke Scale (NIHSS) for stroke patients 3
• Glasgow Coma Scale (GCS) for level of consciousness 3, 6

Clinical Signs of Elevated ICP (Progressive Sequence)

Early signs 4:

• Headache
• Papilledema
• Nausea and vomiting

Late signs 4:

• Stupor and coma
• Pupillary changes (dilated pupil indicates impending herniation requiring urgent neurosurgical evaluation) 6
• Hemiparesis or quadriparesis
• Posturing and respiratory abnormalities
• Cardiopulmonary arrest

Cardiopulmonary Monitoring

• Automated blood pressure cuff is adequate for routine monitoring 3
• Continuous arterial pressure monitoring is required for patients receiving continuous IV antihypertensives or those with deteriorating neurological status 3
• Monitor airway, oxygenation via respiratory status and pulse oximetry 3
• Cardiopulmonary instability with increased ICP must be avoided to minimize secondary injury in patients with impaired autoregulation 3

Advanced Multimodal Monitoring

For patients in neuroscience intensive care units 3:

• Cerebral blood flow (CBF) monitoring provides physiological information at the cellular level 3
• Brain tissue oxygenation monitoring assesses metabolic status 3
• Intracerebral microdialysis evaluates metabolic variables 3

Note: Efficacy of these measures in intracerebral hemorrhage patients has not been tested in randomized trials 3

Critical Thresholds and Prognostic Information

• ICP 20-40 mmHg increases mortality risk 3.95-fold 1, 6
• ICP >40 mmHg increases mortality risk 6.9-fold 1, 6
• Maintain cerebral perfusion pressure (CPP) 60-70 mmHg in adults without multimodal monitoring 6

Common Pitfalls to Avoid

• Do not rely on single CT imaging as it provides only static information and cannot track dynamic ICP changes 3
• Do not perform frequent repeat imaging as it is impractical; use continuous invasive monitoring instead for dynamic assessment 3
• Do not delay neurosurgical consultation in patients with skull fracture and unilateral pupillary dilation, as this indicates impending herniation 6
• Avoid aggressive hyperventilation as it may worsen outcomes through cerebral ischemia 6