Cognitive Function After Surgical Repair of Unruptured Intracranial Aneurysms
To the Editor:
Otawara et al1 found no cognitive impairment or cerebral blood flow reduction in 42 patients submitted to surgical clipping of unruptured cerebral aneurysms. Two further patients of the series—supposed to be consecutive—were excluded from cognitive evaluation because of brain injuries caused by surgery, with Rankin Scale decrease >1. In other words, they had 0% mortality, 4.5% morbidity, and no cognitive impairment in the remaining 95.5%. These data favorably compare with 2.7% mortality and 9.9% morbidity resulting from the ISUIA study,2 as usually happens, for a series of reasons for single-center series in comparison with multicenter trials. The authors conclude that unruptured aneurysm surgery does not affect cognitive function, provided that the patient does not have brain damage sustained from the surgery. I wonder about the meaning of this statement for 2 reasons: first, it does not make sense to exclude patients with brain damage sustained from surgery; second, even uncomplicated surgery always requires a series of invasive maneuvers on the brain, making brain damage unavoidable. Clinical symptoms may appear or not, depending on the extent of the damage, on the region of the brain involved, and on the sensitivity of the applied tests. Neuropsycological and brain flow measurements are simply not sensitive enough to reveal subtle damages of the brain function.
We appreciate the interest of Dr Bergui and colleagues in our article on safe surgery for unruptured intracranial aneurysms in patients without restrictions in postoperative lifestyle.1 Dr Bergui focuses our attention on the exclusion of two patients with surgical complications. We certainly agree with them that clinical symptoms may or may not appear, depending on the extent of the brain damage, the region of the brain damage involved, and the sensitivity of the tests applied. However, we maintain our conclusions for the following reasons.
The cognitive tests we applied can detect general intellectual function, visuospatial construction, and memory function. Although this test battery is not perfect, it can detect cognitive dysfunction if trans-Sylvian surgery affected the frontal and/or temporal lobes of the patient.
I do not agree that even uncomplicated surgery always requires invasive maneuvers in the brain, resulting in unavoidable brain damage. Surgery for unruptured intracranial aneurysm should not cause brain damage, although brain retraction is essential for this procedure. Our surgical procedure involved wide opening of the Sylvian fissure, intermittent use of self-retractors, and careful preservation of the cerebral veins. We believe that these surgical manipulations will preserve the cerebral blood flow and cognitive functions. Previous literature also supports the safety of unruptured aneurysm surgery based on cognitive tests2 and positron emission tomography.3
We believe that surgery for unruptured intracranial aneurysm is safe if we exclude patients with restrictions in postoperative lifestyle. However, we must continue to improve our surgical results.
We thank Dr Bergui and colleagues for their insightful comments.
Otawara Y, Ogasawara K, Ogawa A, Yamadate K. Cognitive function before and after surgery in patients with unruptured intracranial aneurysm. Stroke. 2005; 36: 142–143.
Tuffiash E, Tamargo RJ, Lillis AE. Craniotomy for treatment of unruptured aneurysms is not associated with long-term cognitive dysfunction. Stroke. 2003; 34: 2195–2199.