What are the features of raised Intracranial Pressure (ICP)?

Features of Raised Intracranial Pressure (ICP)

The key features of raised intracranial pressure include declining consciousness, focal neurological deficits, abnormal pupillary responses, and abnormal posturing, which typically develop in the later stages and constitute a medical emergency requiring immediate intervention. 1

Clinical Manifestations

Early Signs and Symptoms

• Headache that is often severe and may worsen with Valsalva maneuvers 1
• Nausea and vomiting, particularly projectile vomiting without preceding nausea 1
• Visual disturbances, including blurred vision, diplopia, and visual field defects 1
• Altered mental status, ranging from mild confusion to progressive decline in consciousness 1
• Papilledema (swelling of the optic disc visible on fundoscopic examination) 1

Late Signs (Indicating Critical ICP Elevation)

• Declining level of consciousness progressing to stupor and coma 2
• Pupillary abnormalities, including sluggish response to light or fixed and dilated pupils 1
• Hemiparesis or quadriparesis 2
• Abnormal posturing (decorticate or decerebrate) 2
• Respiratory abnormalities 2
• Cushing's triad (hypertension, bradycardia, and irregular respiration) - a late sign of critically elevated ICP 3
• Sixth nerve palsy causing incomitant esotropia 1

Diagnostic Findings

Clinical Assessment

• Glasgow Coma Scale (GCS) for standardized assessment of consciousness level 4
• National Institutes of Health Stroke Scale (NIHSS) for neurological assessment 4
• Fundoscopic examination to detect papilledema 1

Imaging Findings

• CT/MRI findings: disappearance of cerebral ventricles, brain midline shift >5mm, compression of basal cisterns 1
• Transcranial Doppler sonography changes: decreased diastolic velocity and increased pulsatility index 4

Invasive Monitoring

• ICP >20-25 mmHg is generally considered elevated 4, 2
• ICP >20-40 mmHg is associated with 3.95 times higher risk of mortality and poor neurological outcome 5
• When ICP exceeds 40 mmHg, mortality risk increases 6.9 times 5
• Lumbar puncture opening pressure >200 mm H₂O indicates elevated ICP 1

Special Considerations

Pediatric Patients

• In infants with open fontanelles: bulging fontanelle, increased head circumference, and separation of cranial sutures 1
• Progressive splaying of sagittal suture width is a reliable indication of increased pressure in neonates 6
• Apnea, bradycardia, lethargy, and decreased activity may be present but are nonspecific signs in neonates 6

Important Caveats

• Papilledema may be absent despite significantly elevated ICP, especially in acute onset 1
• Clinical signs alone may have limited reliability, particularly in early stages 6
• ICP dynamics (trends over time) are often more important than absolute values at any single time point 7
• Different pressure gradients may exist in and around hematomas versus distant areas 6

Monitoring Approaches

Invasive Monitoring

• Fiberoptic ICP monitors within brain parenchyma provide continuous monitoring 4
• Ventricular catheters (external ventricular drains) allow both monitoring and therapeutic CSF drainage 4
• ICP monitoring is recommended as part of protocol-driven care in patients at risk of elevated ICP based on clinical and/or imaging features 4

Non-invasive Assessment

• Transcranial Doppler sonography to assess mass effect and track ICP changes 4
• Point-of-care ultrasound to detect changes in optic nerve sheath diameter in neonates 6
• Serial neurological examinations to detect clinical deterioration 1

Pathophysiological Consequences

• Cerebral hypoperfusion due to reduced cerebral perfusion pressure (CPP = MAP - ICP) 3
• Mechanical distortion and compression of brain tissue 3
• Potential progression to brain herniation syndromes 2
• Cardiopulmonary instability and eventual arrest if left untreated 2

Understanding these features is crucial for early recognition and prompt management of raised ICP to prevent secondary brain injury and improve patient outcomes.