Does subarachnoid hemorrhage show on CT?
Bob: Emergency medicine dogma has stated that computed tomography (CT) is not sensitive enough to detect subtle subarachnoid hemorrhage (SAH), and that negative 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 causes Perimesencephalic subarachnoid hemorrhage?
Most cases of SAH are caused by rupture of an intracranial aneurysm, but approximately 15 to 20 percent of patients do not have an established vascular lesion on initial four-vessel cerebral angiography [1,2].
Where is a Perimesencephalic subarachnoid hemorrhage?
PMSAH, as opposed to aneurysmal SAH, is classically located in the lateral basal cisterns, primarily involving the quadrigeminal cistern, ambient cistern, and cerebellopontine angle cistern. It may secondarily extend into the remaining basal cisterns.
What is a non-aneurysmal subarachnoid hemorrhage?
The bleeding usually arises from an abnormality of blood vessels such as an aneurysm or arteriovenous malformation. In up to 20% of patients no abnormality is identified. The bleeding is thought to originate from a small vein or artery at the base of the brain and is referred to as a non-aneurysmal SAH.
How is subarachnoid hemorrhage diagnosed?
To diagnose a subarachnoid hemorrhage, your doctor is likely to recommend: CT scan. This imaging test can detect bleeding in your brain. Your doctor may inject a contrast dye to view your blood vessels in greater detail (CT angiogram).
What is a Perimesencephalic hemorrhage?
Perimesencephalic subarachnoid hemorrhage (PMSAH) is a distinct pattern of subarachnoid hemorrhage (SAH), which is centered on the basal cisterns around the midbrain.
What causes non-aneurysmal subarachnoid haemorrhage?
There are other non-aneurysmal causes of acute SAH including trauma, dural arteriovenous fistula, spinal tumour or vascular malformation, vasculitis, coagulopathy, cocaine abuse, sickle cell disease, pituitary apoplexy, intracranial arterial dissection and intracranial neoplasia or infarction1,2,12,13.
Why head CT scan is done?
A CT of the brain may be performed to assess the brain for tumors and other lesions, injuries, intracranial bleeding, structural anomalies (e.g., hydrocephalus , infections, brain function or other conditions), particularly when another type of examination (e.g., X-rays or a physical exam) are inconclusive.
What does a subarachnoid hemorrhage look like on CT?
On CT scans, subarachnoid hemorrhage (SAH) appears as a high-attenuating, amorphous substance that fills the normally dark, CSF-filled subarachnoid spaces around the brain, as shown in the images below. The normally black subarachnoid cisterns and sulci may appear white in acute hemorrhage.
What is Perimesencephalic subarachnoid hemorrhage?
Perimesencephalic subarachnoid hemorrhage has been defined as subarachnoid hemorrhage, which on CT within three days of symptom onset 4: is centered anteriorly to the pons and midbrain may extend into the basal and suprasellar cisterns and into the proximal/basal Sylvian fissure and interhemispheric fissure
What is the prevalence of nonaneurysmal Perimesencephalic subarachnoid hemorrhage?
Background Nonaneurysmal perimesencephalic subarachnoid hemorrhage (PMSAH) appears to have an etiology and natural history distinct from aneurysm rupture. Referral-based studies suggest that 15% of SAH patients have no discernable cause of bleeding, but the incidence of PMSAH is unknown.
How common are Perimesencephalic hemorrhages in a ruptured brain aneurysm?
This pattern of hemorrhage was found in only 1 of 92 patients with a ruptured aneurysm. None of the unexplained perimesencephalic hemorrhages was associated with intracerebral hematoma or intraventricular hemorrhage.
Should patients with Perimesencephalic subarachnoid hemorrhage (SAH) have a negative angiogram?
aneurysm highlights the concerns in clinical practice when a patient with a perimesencephalic pattern of SAH is encountered. Possibly, physicians who recognize a perimesencephalic pattern of SAH on CT may bias their expectations for a negative angiogram. Although our case material does not support a second angio-