Current diagnostic Tests for Intracranial Aneurysms
Patients with ruptured aneurysms producing SAH are usually diagnosed by CT scan. However , no test is 100 percent sensitive, and CT scans may not always detect SAH, particularly when it is mild, or if it occurred more than 24 hours before the scan. The refore, whenever a diagnosis of SAH is being entertained, if the CT scan is negative, a lumbar puncture (spinal tap) must be performed for analyzing the spinal fluid for blood or its byproducts ("xanthochromia").
All patients with a diagnosis of SAH, or in whom an aneurysm is suspected
require 4-vessel cerebral angiography. Cerebral angiography is currently the only test sensitive enough to definitively confirm the presence of an aneurysm, and also provides critical information regarding the size, shape, and location of the aneurysm, as well as the presence of vasospasm.
For the patients without recent SAH, the initial diagnostic test is usually a Magnetic Resonance Image (MRI), a Magnetic Resonance Angiogram (MRA), or a Computed Tomographic Angiogram (CTA). These noninvasive tests have become increasingly sensitive in detecting intracranial aneurysms and the findings are generally sufficient for deciding whether the four vessel angiography is warranted. In certain situation noninvasive imaging can be used to make treatment decisions.
Current treatment Options for Intracranial Aneurysms
Aneurysms that have ruptured require treatment to prevent another rupture (rebleeding). Following the initial rupture of an aneurysm, rebleeding is very common (especially within the first two weeks after rupture), and is usually more severe than the initial rupture. Therefore, ruptured aneurysms need to be treated immediately to prevent the risk of rebleeding.
The two primary treatment methods are surgical clipping and endovascular coiling. The optimal treatment choice depends upon the patient's history, physical examination, age, risk factors, and the anatomical characteristics of the aneurysm. It is estimated that 60-65% cerebral aneurysm patients in the United States have received surgical clipping, while approximately the other 30-35% of the patents have received endovascular coiling.
Optimal treatment of patients with intracranial aneurysm requires a highly experienced center that is capable of both coiling and clipping.
Anesthesia for cerebral aneurysm coiling
An interventional neuroradiologist does the aneurysm coiling in radiology suite. The procedure involves placement of small plastic tube (micro-catheter), which is threaded from the groin to the aneurysm in the brain. Then fine platinum threads (coils) are inserted into the aneurysm to fill it up from the inside, much like filling a pothole. The catheter is then removed and the small groin incision covered with a Band-Aid. For an unruptured aneurysm, the patient is discharged home within 24 to 48 hours. During the coiling, general anesthesia is required at most of time. Neither SSEP nor MEP monitoring is often necessary. However, arterial BP monitoring is needed in most of the cases. There is no limitation for administering inhalation agents if patient is not on evoked potential (EP) study.
Anesthesia for cerebral aneurysm clipping
Since advanced radiological diagnostic tests have been applied to the patients, neurosurgeons are able to more precisely identify and localize cerebral aneurysm. Microscopic clipping and EP and electroencephalography (EEG) monitoring become very popular intraoperatively, which results in total intravenous anesthesia (TIVA) being required more often than before. As a trend, intentional hypotension technique and central lines are less needed since excessive introperative blood loss become less frequent. However, invasive BP mentoring still remains as pertinent requirement for the procedure. Newly designed arterial transducer (Edward-Swan) is able to calculated cardiac output. Popofol and Ramifentanyl continue infusion has provided patient with good anesthesia and analgesia with reduced time for emergence. The concept of tight control of blood glucose level is also applied, which directly affect postoperative neurological outcome. In studies published between 1966 and 1996 on clipping of unruptured aneurysms, mortality was 2.6% and morbidity was 10.9%.