Can a CT scan miss a subarachnoid hemorrhage?
Bob: Emergency medicine dogma has stated that com- puted tomography (CT) is not sensitive enough to detect subtle subarachnoid hemorrhage (SAH), and that nega- tive head CT must be followed by a lumbar puncture. As recently as 2008, researchers noted that four-slice CT had a 93 percent sensitivity for detecting SAH.
What is the most correct conclusion for having a normal head CT within 6 hours of onset of headache to rule out subarachnoid hemorrhage?
BOTTOM LINE: 0 Cases of death or negative outcome at 3 months if head CT negative and performed within 6 hours of symptom onset of headache.
How many days after SAH does vasospasm occur?
Vasospasm is the most common complication of SAH and is the main cause of delayed morbidity and mortality. It usually occurs 4 to 14 days after the initial accident, with a peak incidence at 7 days.
When do you suspect SAH?
The diagnosis of SAH should be considered in any patient with a severe and sudden onset or rapidly escalating headache.
What is the sensitivity of CT for SAH?
CT without contrast is the most sensitive imaging study in SAH (see the images below). When carried out within 6 hours of headache onset, CT has 100% sensitivity and specificity. Sensitivity is 93% within 24 hours of onset, 80% at 3 days, and 50% at 1 week.
What is Ottawa SAH rule?
The Ottawa subarachnoid hemorrhage (SAH) rule identifies patients with headache requiring no testing for SAH, while the 6-hour computed tomography (CT) rule guides when to forgo a lumbar puncture.
How is vasospasm treated after SAH?
Nimodipine has been recommended as first-line medical treatment for preventing post-aSAH cerebral vasospasm. It is usually given orally at a dosage of 60 mg every 4 hours for 21 days after the initial subarachnoid hemorrhage.
What causes high RBC in CSF?
Finding red blood cells in the CSF may be a sign of bleeding. However, red blood cells in the CSF may also be due to the spinal tap needle hitting a blood vessel. Additional conditions which this test may help diagnose include: Arteriovenous malformation (cerebral)
How do you rule out SAH?
Patients suspected of having subarachnoid hemorrhage are typically evaluated with an unenhanced computed tomography (CT) scan followed by a lumbar puncture if results of the CT scan are negative. Computed tomography is highly sensitive when performed soon after headache onset.
Is a CT scan 100% sensitive to SAH?
However, this data makes it pretty clear that a CT scan, even if it is within 6 hours, is not 100% sensitive for SAH. A systematic review that identified 5 trials (including the first but not the second Perry paper) encompassing 8907 patients concluded that a CT scan within 6 hours of headache onset has a sensitivity of 98.7%.
Does a normal head CT within 6 hours rule out Sah?
Does a Normal Head CT Within 6 Hours of Onset of Headache Rule Out SAH? Background: The traditional standard workup for ruling out subarachnoid hemorrhage (SAH) has been a non-contrast head CT and, if negative, a lumbar puncture.
What is the sensitivity of a CT scan for headache?
A systematic review that identified 5 trials (including the first but not the second Perry paper) encompassing 8907 patients concluded that a CT scan within 6 hours of headache onset has a sensitivity of 98.7%. (Dubosh 2016) There were 13 misses out of 8907 patients, or about 1.5 misses per 1000 patients.
How accurate is a CT scan after 6 hours?
Bottom line: Although CT within 6 hours is not 100% accurate, it results in a very low posttest probability. What if the CT happened after 6 hours? CT is much less accurate after 6 hours, with a reported sensitivity of approximately 86% (95% CI 78.3-90.3).