Can intracranial (within the skull) hypotension (low pressure) be diagnosed on a computed tomography (CT) scan?

Intracranial Hypotension on CT Scan

Intracranial hypotension can be detected on CT scan, but MRI is significantly more sensitive and is the preferred imaging modality for diagnosing this condition. 1

CT Findings in Intracranial Hypotension

CT scan may show several features suggestive of intracranial hypotension, including:

• Subdural fluid collections or hematomas 1
• Engorgement of venous sinuses 1
• Brain sagging or descent of the brain 1
• Effacement of basal cisterns 1
• Convex superior surface of the pituitary 1

However, CT has significant limitations in detecting intracranial hypotension:

• Many of the subtle findings may be missed on non-contrast CT 1
• CT without contrast is not recommended as an initial imaging study for suspected intracranial hypotension 1
• Even CT with contrast is less sensitive than MRI for detecting the characteristic findings 1, 2

Preferred Imaging Approach

For suspected intracranial hypotension, the imaging approach should follow this algorithm:

1. Initial brain imaging: MRI head without and with IV contrast is most useful for initial evaluation 1

   • Detects qualitative signs: pachymeningeal enhancement, midbrain descent, subdural collections 1
   • Evaluates quantitative signs: pituitary height, pontomesencephalic angle, midbrain descent 1

2. Initial spine imaging: MRI complete spine without IV contrast (or without and with contrast) 1

   • Optimized with fluid-sensitive sequences, especially 3D T2-weighted fat-saturated sequences 1
   • Detects epidural fluid collections and meningeal diverticula 1

3. Advanced imaging (if initial studies are negative but clinical suspicion remains high):

   • Dynamic CT myelography or digital subtraction myelography 1
   • These techniques are more sensitive for detecting subtle CSF leaks and CSF-venous fistulas 1

Clinical Implications

The accurate diagnosis of intracranial hypotension is crucial for patient outcomes:

• Misdiagnosis can lead to unnecessary procedures and prolonged morbidity 2, 3
• Proper imaging guides targeted therapy such as epidural blood patch, which is the mainstay of treatment 1, 4
• In severe cases with obtundation, prompt diagnosis and treatment are essential to prevent serious neurological complications 1

Important Considerations

• The spine is the anatomical source of most symptomatic CSF leaks, not the intracranial compartment 1
• Approximately 20% of initial brain MRIs and 46-67% of initial spine imaging may be normal in patients with clinically suspected intracranial hypotension 1, 3
• CSF pressure can be normal in some patients with intracranial hypotension, so imaging findings are crucial for diagnosis 1, 5

In summary, while CT can detect some features of intracranial hypotension, MRI is the preferred initial imaging modality due to its superior sensitivity for the characteristic findings of this condition.