Intracranial stents are metal mesh-wire tubes that are placed within an artery using a threaded catheter. The wire mesh is opened up using a balloon inflation device. Stents are frequently used to open up clogged or narrowed arteries during angioplasty (surgical reshaping of the artery). Atherosclerotic stenoses (a condition characterized by narrowing and thickening of the artery wall leading to a decrease in the blood flow) less frequently affects the intracranial arteries, than the extra-cranial arteries.
Intracranial atherosclerotic stenosis can be treated with medications (such as aspirin, clopidogrel, and ticlopidine) and prevented with a newly phosphodiesterase inhibitor known as ‘cilostazol’ (Kwon et al, 2005). However, if the drug is not useful at lowering the development of atherosclerotic stenosis, balloon angioplasty along with placement of a stent may be required. Studies are also being conducted to determine its use for cerebral vasospasm associated with aneurysmal sub-arachnoid hemorrhage (SAH).
Komotar et al (2005) suggested that intracranial stenting could be routinely used by neurosurgeons in the future to treat atherosclerotic stenosis of the intracranial arteries. However, further studies were required to study their effectiveness, appropriateness and the ways in which complications can be reduced. Only through multidisciplinary approach and experience, could the chances of complications be reduced. The FDA has cleared the use of the ‘Neurolink system” in August, 2002. It can be used for individuals suffering from recurrent intracranial strokes arising from atherosclerotic stenosis resistant to drug therapy.
The vessels should have a diameter of 2. 5 to 4. 5 mm. A study was conducted in 2004 (SSLYVIA Study Group) to determine the effectiveness and safety of the Neurolink System on about 61 patients requiring stent placement. Stokes occurred in 6. 6 % within a one month period, and in 7. 3 % beyond a month and less than a year. In the remaining patients, the stents were successfully placed. Re-stenosis greater than 50 % occurred in about 32 % of the cases after a six month period, but 61 % of the cases did not develop any symptoms.
There are chances of several complications such as re-stenosis, sudden obstruction of the arteries, symptomatic dissection, arterial rupture, stroke, etc of developing. Hauth et al (2004) said that intracranial stenting of the vertebral artery was possible, but the chances of complications were high compared to extra-cranial stenting of the vertebral artery. Doerfler et al (2004) also suggested that intracranial stenting was possible in patients with atherosclerotic stenosis of the intracranial arteries, but the chances of life-threatening complications were high. Hence, they should be performed only in certain patients.
It was suggested that a multi-disciplinary approach had to be followed, and the patients and to be closely followed up after the surgery. Intracranial stenting can lower the rate of re-stenosis of the cranial arteries, but the benefits are not fully confirmed. Lylyk et al (2005) conducted a study on the use of intracranial stents. He found that the extent of stenosis on an average could be reduced to less than 30 %. The chances of complications developing from the procedure were about 5. 7% and fatalities were 3. 8 %. Yu et al (2005) demonstrated that the outcome on 15 of the 18 patients were excellent after two years of stenting.
2 patients died after 30 and 36 months due to medical disorders, and one patient developed recurrent stroke attacks. Kim et al (2004) suggested that stenting for the coronary and peripheral arteries had predictable outcomes. However, the results in the case of intracranial stenting had to be established. It was observed that in two cases, the intracranial stenting was unsuccessful due to the development of a tortuous curve in the internal carotid artery. The rate of re-stenosis was low following intracranial stent placement, but the chances of complications were rather high.
Studies conducted in individuals receiving intracranial stents for the middle cerebral artery demonstrated that four of the five patients with transient ischemia attacks and five of the six patients with stroke had better functional levels. Further studies are required to compare the effectiveness of intracranial stenting with other treatment modalities in preventing stokes. The occurrences of several complications such as strokes, fatal outcomes, minor complications (such as bleeding, hematoma formation, wound infections, nerve paralysis), the rate of recurrences or re-stenosis and the need for hospitalizations should be clearly determined.
References:
Doerfler A, Becker W, Wanke I, et al (2004). “Endovascular treatment of cerebrovascular disease. Curr Opin Neurol, 17(4), 481-487. Hauth EA, Gissler HM, Drescher R, et al (2004). “Angioplasty or stenting of extra- and intracranial vertebral artery stenoses. ” Cardiovasc Intervent Radiol, 27(1), 51-57. Kim JK, Ahn JY, Lee BH, et al (2004). “Elective stenting for symptomatic middle cerebral artery stenosis presenting as transient ischaemic deficits or stroke attacks: Short term arteriographical and clinical outcome. ” J Neurol Neurosurg Psychiatry, 75(6), 847-851.