Medical Student Research Fellowship for Summer 2012
Mentor: Dr. Mark Johnson
Department: Neurology and Neurotherapeutics
Room number: C505.420
Mail Code: 8897
Phone number: (214)648-3748
Project title: The Predictive Value of Basilar Artery for Cerebral Vasospasm
Human subjects IRB approved project number (where applicable):
Animal subjects IRB approved project number (where applicable):
Project Type (patient-based research, animal-based research, or basic research; this characterization is only to permit a general classification for grouping similar types of projects)
Patient-based; All patient identifiers will be removed upon data entry.
Brief Description of Project:
Subarachnoid hemorrhage (SAH) is a common yet debilitating condition that can be caused by cerebral aneurysm or head trauma. SAH affects about 30,000 Americans a year and accounts for ~5% of all strokes1. Typically, cerebral vasospasm, a serious complication associated with subarachnoid hemorrhage, occurs a few days after the incident of the hemorrhage and puts the patient at high risk of cerebral ischemia. Cerebral ischemia can lead to ischemic brain injury or permanent brain damage if it is not detected and treated early enough. About one-third of patients admitted with SAH will have cerebral vasospasms, and about half of those who have cerebral vasospasms will suffer permanent brain damage2. Therefore, clinicians always closely monitor patients who have suffered a SAH. Early detection of cerebral vasospasms is vital to provide patients with adequate treatment and prevent brain damage.
The Transcranial Doppler (TCD) is an accurate, noninvasive tool that clinicians frequently employ to diagnose cerebral vasospasms in SAH patients. TCD measures the blood flow velocity of the brain’s basal arteries. Studies have demonstrated a correlation between elevated blood flow velocities in the basal arteries of the brain and onset of vasospasms3,4. However, cerebral vasospasms may not be accurately differentiated from cerebral hyperemia. Thus, clinicians have developed several indices to combat the shortcomings of TCD to accurately diagnose cerebral vasospasms. One of the more common indices used is the ratio of blood flow velocities between the middle cerebral arteries and the internal carotid artery (MCA/ICA)4. However, this ratio mainly focuses on the anterior cerebral circulation. Sousitel, et al developed the basilar artery index to detect vasospasms in the posterior cerebral circulation that takes the ratio of blood flow velocities between the basilar artery and the external vertebral arteries (BA/eVA)5. However, studies have questioned the accuracy of the index based on the study’s methodology6,7.
Recently, a large cohort study found that patients who experienced BA vasospasms after a SAH had a higher incidence of posterior cerebral ischemia, particularly in the brainstem8. In addition, BA blood flow velocities correlated with the severity of brainstem ischemia. Finally, patients who experienced BA vasospasms or brainstem ischemia had worse outcomes than those who did not. These findings suggest that BA vasospasm plays a significant role in cerebral vasospasms after an incidence of SAH. Therefore, the basilar index needs to be accurate so that clinicians can accurately diagnose BA vasospasms in SAH patients early enough to implement the proper treatment.
The aim of the present study is to confirm the clinical validity of the basilar artery index and possibly identify other methods of assessment of posterior cerebral vasospasm. An additional goal of the present study is to enhance the current level of knowledge for treatment of patients with SAH and improve early detection of clinically significant cerebral vasospasm.
Throughout the course of this study, I will be working closely with Dr. Mark Johnson to establish a database based on clinical imaging data for TCD and catheter angiograms available in the Neurosonology lab at UT Southwestern Medical Center. The database will include pertinent data to examine the accuracy of the basilar artery index compared to other established assessments of cerebral vasospasm. During this process, I will learn how to interpret TCD imaging data and how it is used in a clinical setting. Once Dr. Johnson and I have established a database, I will analyze the data to determine if the BA index is a reliable index to use in the diagnosis of posterior cerebral vasospasm. At completion of my research period, I plan to have the results available to share with the medical community. I hope that the results will provide clinicians with more knowledge about diagnosing posterior cerebral vasospasms with the BA index and possibly a new index for diagnosing cerebral vasospasms. In diagnosing cerebral vasospasms, the more information about diagnostic indices and the more diagnostic indices available to clinicians, the more accurate cerebral vasospasm diagnosis will be.
1. Bederson JB, Connolly ES, Jr., Batjer HH, et al. Guidelines for the management of aneurysmal subarachnoid hemorrhage: a statement for healthcare professionals from a special writing group of the Stroke Council, American Heart Association. Stroke; a journal of cerebral circulation 2009;40:994-1025.
2. Dorhout Mees SM, Rinkel GJ, Feigin VL, et al. Calcium antagonists for aneurysmal subarachnoid haemorrhage. Cochrane Database Syst Rev 2007:CD000277.
3. Laumer R, Steinmeier R, Gonner F, Vogtmann T, Priem R, Fahlbusch R. Cerebral hemodynamics in subarachnoid hemorrhage evaluated by transcranial Doppler sonography. Part 1. Reliability of flow velocities in clinical management. Neurosurgery 1993;33:1-8; discussion -9.
4. Lindegaard KF, Nornes H, Bakke SJ, Sorteberg W, Nakstad P. Cerebral vasospasm after subarachnoid haemorrhage investigated by means of transcranial Doppler ultrasound. Acta neurochirurgica Supplementum 1988;42:81-4.
5. Soustiel JF, Shik V, Shreiber R, Tavor Y, Goldsher D. Basilar vasospasm diagnosis: investigation of a modified "Lindegaard Index" based on imaging studies and blood velocity measurements of the basilar artery. Stroke; a journal of cerebral circulation 2002;33:72-7.
6. Sloan MA. Diagnosis of basilar artery vasospasm. Stroke; a journal of cerebral circulation 2002;33:1746-7; author reply -7.
7. Sviri GE, Ghodke B, Britz GW, et al. Transcranial Doppler grading criteria for basilar artery vasospasm. Neurosurgery 2006;59:360-6; discussion -6.
8. Sviri GE, Lewis DH, Correa R, Britz GW, Douville CM, Newell DW. Basilar artery vasospasm and delayed posterior circulation ischemia after aneurysmal subarachnoid hemorrhage. Stroke; a journal of cerebral circulation 2004;35:1867-72.
Previous Research Activities or Publications with Medical Students:
Jessica Lee, M.D.; Paul Hansen, M.D.; Fazeed Siddiqui – Use of Mechanical Thrombectomy in Cerebral Sinus Thrombosis: A single center experience.