IMPORTANT: We currently have a number of bugs related to image cropping and are actively trying to resolve them. In the meantime, we have disabled cropping. Apologies for any inconvenience. Stay informed: radiopaedia.org/chat

Subarachnoid hemorrhage - posterior fossa

Case contributed by Peter Mitchell
Diagnosis certain

Presentation

Headache and altered conscious state - SAH?

Patient Data

Age: 65 years
Gender: Male

Subarachnoid blood of heterogeneous density is seen around the cervicomedullary junction, inferior cerebellar vermis and basal cisterns. There is intraventricular blood is evident. Moderately severe hydrocephalus is seen. There is mild effacement of the cortical sulci.

Pattern suggests dissecting aneurysm or aneurysm of PICA.

No aneurysm, dissection or focal narrowing of vertebral areteries shown.

Normal. Remain suspcicious for dissection - close imaging follow up with multiple modalities recommended.

Partially shown on this MRA of tthe neck vessels is narrowing in the V4 segment of the vertebral artery. Vasospasm or dissection are the differential diagnoses.

Normal

Note marked progressive narrowing of the V4 segments has developed bilaterally, crossing the PICA origins. Changes are worse on the right. No vasospasm in the anterior circulation. Close inspection reveals a small aneurysm at the junction of the right PICA and vertebral artery. Likely diagnosis is dissecting aneurysm of vertebral / PICA junction - bilateral dissections, major differential diagnosis is dissection of PICA origin and vasospasm explaining the vertebral stenoses.

Case Discussion

Posterior fossa pattern of SAH is shown - the differential diagnosis is between PICA aneurysm and vertebral dissecting aneurysm.  PICA aneurysms are usually evident on initial imaging - if initial imaging is negative remain suspicious of underlying dissection.  Repeat imaging may be required over several days to make the diagnosis. In this case, the likely diagnosis is dissecting aneurysm of the PICA/Vertebral junction, with dissection involving the vertebral with associated vasospasm in both V4 segments.  The alternative diagnoses are initially occult PICA berry aneurysm and now vasospasm, or dissecting aneurysm with bilateral V4 dissections.

How to use cases

You can use Radiopaedia cases in a variety of ways to help you learn and teach.

Creating your own cases is easy.

Updating… Please wait.

 Unable to process the form. Check for errors and try again.

 Thank you for updating your details.