Does My Patient Have Increased ICP? Accuracy of Exam and CT

March 2, 2020

Written by Clay Smith

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No physical exam findings were able to clearly discriminate increased intracranial pressure (ICP) or not. On CT, pay attention to compressed basal cisterns and midline shift >10mm, but increased ICP may be present with a normal CT.

Why does this matter?
Can you tell at the bedside whether a patient has increased ICP? No? Neither can anyone else, apparently. How do we decide when to call neurosurgery? This review can still help us.

Is that brain swole?
This was a systematic review of 40 studies with 5,123 patients to determine the diagnostic accuracy of physical exam and imaging findings for the diagnosis of increased ICP, compared with a gold standard of invasive ICP monitoring. Pupillary dilation, GCS motor <3 (posturing), and total GCS ≤8 were all poor discriminators for increased ICP, with the best positive likelihood ratio (LR+) 2.0 and best negative likelihood ratio (LR-) 0.6 (that’s not very good at all). On CT, compression of the basal cisterns was 85.9% sensitivity (58.0–96.4); 61.0% specificity (29.1–85.6); LR+ 2.20 (0.99–4.93); LR- 0.23 (0.06–0.84). Midline shift >10mm on CT was 20.7% sensitive (13.0–31.3); 89.2% specific (77.5–95.2); LR+ 1.92 (0.87–4.25); LR- 0.89 (0.78–1.01). My take-away on CT – if you see compression of the basal cisterns, it should heighten concern; if significant midline shift is present, it’s real – call neurosurgery. They were not able to meta-analyze optic nerve sheath diameter due to varying cutoffs on size. Most studies were retrospective, and only midline shift >10mm was based on high quality evidence. In summary, none of these features alone were very helpful at ruling in or out increased ICP. A CT may look normal yet still have increased ICP. In reality, we combine worrisome exam, CT, and clinical course to determine disposition. In an altered patient with trauma, bleed, infarct, infection, mass, or other cause of edema, we usually need to involve neurosurgery and let them decide whether or not to place invasive monitoring.

Source
Accuracy of Physical Examination and Imaging Findings for the Diagnosis of Elevated Intracranial Pressure. Acad Emerg Med. 2020 Jan 29. doi: 10.1111/acem.13928. [Epub ahead of print]

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