Individual non-invasive tests are not adequate for brain injury diagnosis

Researchers discover that individual tests checking for physical signs such as dilated pupils, abnormal posturing and reduced levels of consciousness are not able to accurately detect increased intracranial pressure.

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In a study published in The British Medical Journal, researchers have discovered  tests based on physical signs are not able to detect increased intracranial pressure (ICP) around the brain caused by head injury or illness.

Clinicians typically depend on checking for physical signs such as dilated pupils, abnormal posturing, reduced levels of consciousness or signs of damage on a CT scan, however,  the accuracy of these tests is uncertain.

The team of researchers advise that these tests should not be used independently to rule out brain injury and patients with increased ICP should be monitored further at an expert center.

The researchers used findings from 40 studies investigating the accuracy of non-invasive tests conducted on 5123 critically ill adults. 

The team calculated both severity and specificity for each of the tests. Sensitivity measured the percentage of people who are correctly identified as having a condition, whilst specificity measured the percentage of people who are correctly identified as not having a condition. 

Three physical signs typically associated with brain injury were evaluated: 

  • Presence of dilated pupils had sensitivity of 28% and specificity of 86% for detecting ICP, meaning that 72% of patients with the condition would be missed and 14% of patients without the condition would be incorrectly diagnosed. 
  • Abnormal posturing had sensitivity of 54% and a specificity of 64%.
  • Reduced consciousness had a sensitivity if 76% and a specificity of 40%. 

Several other non-invasive tests also had poor accuracy for increased ICP.

CT imaging signs typically associated with brain injury was discovered to have better diagnostic accuracy, however, are not available in all centers. For example, absence or compression of basal cisterns had sensitivity of 86% and specificity of 61%. 

The findings from this study suggest that individual physical examinations are not adequate to accurately diagnose elevated ICP. However, in practice a combination of tests are used to diagnose patients with brain injuries. Therefore, further future studies looking into the sensitivity and specificity of a series of physical examinations are required. 

The team of researchers came to the conclusion that a more comprehensive view should be taken, focusing  on patient factors, factors related to brain injury as we as clinical signs.

Sources: Fernando SM, Tran A, Cheng W et al. Diagnosis of elevated intracranial pressure in critically ill adults: systematic review and meta-analysis. BMJ. doi:10.1136/bmj.l4225 (2019) (Epub ahead of print);

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Kimberley Ndungu

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