Long-term outcomes after formation of a low-flow STA-MCA bypass for treatment of symptomatic occlusion of the internal carotid artery

Aim. To evaluate short‑ and long‑term effectiveness of low‑flow bypass between superficial temporal artery and M4 segment of middle cerebral artery (low‑flow STA‑MCA bypass) in patients with symptomatic occlusion of the internal carotid artery (ICA).

Materials and methods. Between 2016 and 2019 at the Department of Neurosurgery of the N. V. Sklifosovsky Research Institute of Emergency Medicine, 54 patients who underwent low‑flow STA‑MCA bypass formation at the side of symptomatic ICA occlusion between 2013 and 2015 were examined. Symptomatic ICA occlusion was more common in men than in women (7:1 ratio). Patient age varied between 48 and 73 years (mean age was 62 years).

During low‑flow STA‑MCA bypass formation surgery for symptomatic ICA occlusion, intraoperative flowmetry was used in 52 (96 %) patients, in 2 (4 %) patients this diagnostic method was impossible to perform due to technical difficulties. The main examination methods in the long term after cerebral revascularization were evaluation of neurological status dynamics per the National Institute of Health Stroke Scale (NIHSS); modified Rankin scale; Rivermead mobility index; computed tomography angiography of the extra‑intracranial arteries; ultrasound (US) examination of the STA‑MCA bypass for eval uation of linear and volumetric blood flow velocities; single‑photon emission computed tomography. The type and size of trephination were evaluated, and operative time was taken into account.

The patients were divided into 3 groups: group 1 included patients with follow‑up period of 1–2 years after cerebral revascularization, group 2 – 3–4 years, group 3 – 5–6 years. All results were compared to preoperative, early, and longterm measurements.

Results. In the long‑term postoperative period between 1 and 6 years after cerebral revascularization, 54 patients were examined. Computed tomography angiography and US showed functioning STA‑MCA bypass in 53 (98 %) patients. According to single‑photon emission computed tomography of the brain, regional cerebral blood flow in the longterm postoperative period varied between 28 and 40 mL / 100 g / min, median regional cerebral blood flow in the long‑term postoperative period was 38 mL / 100 g / min. Intraoperative flowmetry was performed in 52 (96 %) patients, median was 15.5 mL / min. US showed that linear blood flow velocity in the STA‑MCA bypass varied between 20 and 95 cm / s, median was 49 cm / s. Volumetric blood flow varied between 30 and 85 mL / min with median of 75 mL / min.

Resection trephination was performed in 36 (67 %) patients, mean size of trephination hole was 3 cm³. In the study, operative time was measured: mean value was 212 min; no significant correlation between operative time and trephination size was observed.

Improved neurological status was observed in all study groups. Per the NIHSS, in group 1 (1–2 years) improvement was observed in 59 % of patients, in group 2 (3–4 years) in 48 %, in group 3 (5–6 years) in 47 %. Per the modified Rankin scale, in group 1 improvement was observed in 36.4 % of patients, in group 2 – in 48 %, in group 3 – in 42.9 %. Per the Rivermead mobility index, in group 1 improvement was observed in 63.3 % patients, in group 2 – in 56 %; in group 3 – in 57.1 %. The best outcomes were observed in group 1 (63.3 %).

Conclusion. Instrumental diagnostic methods and evaluation of neurological status showed positive dynamics both in the postoperative period and in long‑term period between 1 and 6 years after low‑flow STA‑MCA bypass formation. In the long term, repeat abnormalities of cerebral blood flow of ischemic type and repeat transient ischemic attacks were not observed. Correct selection of patients in the preoperative period and comprehensive treatment including drug therapy in the postoperative and long‑term periods allow to prevent repeat ischemic cerebrovascular disease and therefore improve patients’ quality of life.

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