Can increased intracranial pressure be seen on a computed tomography (CT) scan of the head?

Can Increased Intracranial Pressure Be Seen on CT?

Yes, CT can detect certain signs of increased intracranial pressure, but it is unreliable and frequently misses elevated ICP—a normal CT does NOT exclude dangerously elevated intracranial pressure. 1, 2, 3, 4

Critical Limitations of CT for Detecting Elevated ICP

CT scans are not reliable tools for diagnosing raised intracranial pressure and should not be used as the sole method for this purpose. 3 The evidence demonstrates significant discrepancies between CT findings and actual measured ICP values:

• Patients with severely elevated ICP (44-90 mmHg measured by ventriculostomy) can have CT scans that greatly underestimate or completely fail to show signs of increased pressure. 4
• Even when clinical cerebral herniation is evident, contemporary CT may fail to detect it in patients with conditions like pneumococcal meningitis. 4
• In severely head-injured comatose patients whose initial CT appears normal or shows no mass lesion, midline shift, or abnormal cisterns, 7 out of 8 patients (87.5%) still developed intracranial hypertension on continuous monitoring. 5

CT Findings That Suggest Elevated ICP (When Present)

When CT does show abnormalities, certain findings correlate with elevated ICP:

High-Yield CT Signs

• Third ventricle compression correlates significantly with measured ICP ≥20 mmHg and is associated with poor outcomes. 6, 7
• Sulcal obliteration is significantly associated with measured ICP ≥20 mmHg. 6
• Basal cistern compression or effacement closely correlates with ICP >20 mmHg and indicates midbrain dysfunction with worse prognosis. 7
• Lateral ventricle compression is associated with elevated ICP. 6
• Midline shift suggests mass effect and elevated pressure. 6
• Herniation (when visible) indicates critically elevated ICP. 6

Prognostic Value

• The presence of all five radiographic signs (sulcal obliteration, lateral ventricle compression, third ventricle compression, midline shift, herniation) predicts poor functional outcome (OR = 4.44). 6
• Hemorrhage volume >30 cc is associated with increased mortality (OR = 3.702). 6
• Posterior fossa hemorrhage (OR = 3.208) and basal ganglia hemorrhage (OR = 3.079) are associated with death. 6

The Superior Alternative: MRI

MRI of the head and orbits is the most useful imaging modality for detecting elevated ICP, as it identifies subtle signs that CT consistently misses. 1, 2, 8, 3

MRI Findings with High Specificity for Elevated ICP

• Posterior globe flattening: 56% sensitivity, 100% specificity. 1, 8
• Intraocular protrusion of the optic nerve: 40% sensitivity, 100% specificity. 1, 8
• Horizontal tortuosity of the optic nerve: 68% sensitivity, 83% specificity. 1, 8
• Enlarged optic nerve sheath (mean 4.3 mm vs 3.2 mm in controls). 1, 8
• Empty or partially empty sella. 1, 2, 8
• Distention of the perioptic subarachnoid space. 1

Essential MRI Protocol Components

• Standard brain sequences to exclude mass lesions or hydrocephalus. 8, 3
• Orbital imaging with coronal, fat-saturated T2-weighted sequences to evaluate optic nerve sheaths. 8, 3
• MR venography (MRV) must be included to evaluate for venous outflow obstruction or transverse sinus stenosis. 1, 2, 8

Clinical Algorithm for Suspected Elevated ICP

Step 1: Initial Imaging Decision

• CT head without contrast may be useful as a rapid first-line test to detect space-occupying lesions or hydrocephalus causing elevated ICP. 1
• CT is appropriate when immediate assessment for surgical lesions (hemorrhage, mass) is needed. 1
• However, proceed to MRI regardless of CT findings if clinical suspicion for elevated ICP remains high. 2, 8

Step 2: Definitive Evaluation

• MRI head and orbits with MRV is required for definitive evaluation when elevated ICP is suspected. 2, 8, 3
• CT venography can substitute for MRV if MRI is contraindicated. 1

Step 3: Confirmatory Testing

• Lumbar puncture with opening pressure measurement is essential when imaging is normal or shows only subtle findings. 2, 8, 3
• Opening pressure >250 mmH₂O (or >280 mmH₂O in sedated/obese children) confirms elevated ICP. 2, 3
• Normal CSF composition distinguishes idiopathic intracranial hypertension from infectious or inflammatory causes. 1

Common Pitfalls to Avoid

• Never rely on a normal CT to exclude elevated ICP in comatose patients or those with persistent symptoms. 5, 4
• Do not assume that absence of papilledema on initial examination excludes elevated ICP—it may develop later. 2
• In severely head-injured comatose patients, continuous ICP monitoring should be considered even with normal CT findings. 5
• CT may be particularly unreliable in infectious meningitis—consider early ICP monitoring regardless of CT appearance in prolonged coma. 4
• When CT shows signs of elevated ICP, the actual measured pressure is often higher than CT findings suggest. 4

Role of Direct ICP Monitoring

• Continuous ICP and blood pressure monitoring with derived cerebral perfusion pressure is recommended for all comatose head-injured patients, regardless of initial CT findings. 5
• Ventriculostomy provides both diagnostic ICP measurement and therapeutic CSF drainage. 4
• The proportion of time with sustained ICP ≥20 mmHg directly correlates with mortality. 6