What are the signs and symptoms of elevated intracranial pressure (ICP) in a patient with a history of head trauma and a diagnosed subdural hematoma?

Signs and Symptoms of Elevated Intracranial Pressure

In a patient with head trauma and subdural hematoma, recognize elevated ICP through early signs of decreased level of consciousness and late signs of pupillary abnormalities, with the understanding that changes in consciousness are the most sensitive early indicator while pupillary changes signal impending herniation. 1, 2

Early Clinical Signs

Changes in level of consciousness represent the earliest and most sensitive indicator of rising ICP and should prompt immediate intervention before progression to herniation. 1

• Decreased level of consciousness or deterioration in mental status is the primary early warning sign 1, 3
• Headache (in conscious patients) 1, 3
• Visual disturbances 1
• Nausea and vomiting 3
• Deterioration in motor function 1
• Changes in blood pressure or heart rate (early hemodynamic instability) 1
• Changes in respiratory pattern 1

Late Clinical Signs (Medical Emergency)

Pupillary abnormalities are late signs indicating severe intracranial hypertension and impending herniation, requiring emergent neurosurgical intervention. 1, 3

• Pupillary changes (anisocoria or bilateral mydriasis) - this is a late and ominous sign 1, 3
• More persistent changes in vital signs 1
• Posturing (decorticate or decerebrate) 3
• Hemiparesis or quadriparesis 3
• Respiratory abnormalities with changes in arterial blood gases 1, 3
• Cushing's reflex (hypertension, bradycardia, and respiratory irregularity) - indicates severe intracranial hypertension with ICP typically >40 mmHg 4

Imaging Findings Correlating with Elevated ICP

CT scan findings provide critical objective evidence of elevated ICP, with compression of basal cisterns being the most reliable radiographic predictor. 1

• Compression or absence of basal cisterns - associated with ICP >30 mmHg in over 70% of cases 1, 2
• Disappearance of cerebral ventricles 1, 2
• Midline shift >5 mm 1, 2
• Intracerebral hematoma volume >25 mL 1, 2
• Presence of traumatic subarachnoid hemorrhage 1
• Mass effect with frontal horn compression or shift of septum pellucidum or pineal gland 1

Critical Thresholds and Prognostic Information

ICP elevation carries specific mortality risks that escalate dramatically above 40 mmHg. 1, 5, 4

• ICP 20-40 mmHg: Associated with 3.95-fold increased risk of mortality and poor neurological outcome 1, 5, 4
• ICP >40 mmHg: Mortality risk increases 6.9-fold and is almost universally associated with severe consciousness impairment or coma 1, 5, 4
• ICP >20-25 mmHg is generally considered elevated and requires aggressive therapy 4

Specific Considerations for Subdural Hematoma

In patients with subdural hematoma, high initial ICP at admission predicts subsequent ICP elevation, along with coagulation abnormalities. 6

• Elevated initial ICP (>20 mmHg) strongly predicts ongoing intracranial hypertension 6
• Prolonged activated partial thromboplastin time (APTT >35 seconds) is associated with ICP elevation 6
• Low fibrinogen levels (<200 mg/dL) correlate with elevated ICP 6
• Isolated cranial nerve palsies (particularly oculomotor nerve palsy) may be the only presenting sign in smaller tentorial subdural hematomas 7

Common Pitfalls to Avoid

• Do not wait for pupillary changes - these are late signs indicating imminent herniation; act on early consciousness changes 1
• Do not assume normal CT scan excludes elevated ICP - while rare (0-8% incidence), elevated ICP can occur with normal imaging, particularly if neurological assessment is not feasible 1
• Do not rely solely on clinical signs - ICP cannot be reliably estimated from clinical features alone and requires direct measurement when indicated 2
• Recognize that visible basal cisterns do not exclude intracranial hypertension - their visibility cannot definitively rule out elevated ICP 1

Indications for Invasive ICP Monitoring in This Context

Place ICP monitors in subdural hematoma patients with GCS ≤8, clinical evidence of transtentorial herniation, or significant imaging abnormalities. 1, 2

• Glasgow Coma Scale score ≤8 1, 2
• Clinical evidence of transtentorial herniation 1
• Significant intraventricular hemorrhage or hydrocephalus 1
• Post-operative monitoring after hematoma evacuation if any of the following: preoperative GCS motor response ≤5, preoperative anisocoria/bilateral mydriasis, preoperative hemodynamic instability, or severe CT findings 1