From the Research
Posterior cerebral artery (PCA) occlusions typically do not cause ipsilateral weakness, but rather contralateral weakness due to the normal anatomical arrangement of motor pathways in the brain. The PCA supplies the occipital lobe, parts of the temporal lobe, thalamus, and portions of the midbrain. When a PCA occlusion occurs, the resulting infarction affects these areas, leading to symptoms like contralateral homonymous hemianopia (vision loss), sensory deficits, and sometimes memory impairment. However, in rare cases, ipsilateral weakness can occur with PCA occlusions through specific mechanisms, such as:
- The PCA occlusion affecting the cerebral peduncle on the same side through involvement of perforating branches to the midbrain, causing ipsilateral cranial nerve III palsy with resultant weakness of eye muscles, as seen in a study published in 2021 1.
- The PCA occlusion being extensive enough to cause significant edema and mass effect, leading to compression of adjacent structures or midline shift that affects the ipsilateral side. These situations are uncommon, and the typical presentation of PCA occlusion involves contralateral deficits due to the crossing of motor pathways in the medulla before they reach the cortex. A study published in 2022 found that mechanical thrombectomy for acute posterior cerebral artery stroke is feasible and has predictors of outcome, including male sex, admission NIHSS, and pc-ASPECTS 2. Another study published in 2021 found that mechanical thrombectomy in isolated occlusion of the proximal posterior cerebral artery appears safe and feasible, with positive effects on clinical outcome, primarily on early neurological improvement 3. Additionally, a study published in 2020 found that thrombectomy and thrombolysis of isolated posterior cerebral artery occlusion have cognitive, visual, and disability outcomes, with increased odds of recanalization following IVT and even higher after EVT 4. A multicenter experience and systematic literature review published in 2021 found that thrombectomy for isolated occlusions of the posterior cerebral artery is feasible and safe, with a high rate of successful recanalization and low rate of complications 5. Overall, while PCA occlusions typically do not cause ipsilateral weakness, it is essential to consider the specific mechanisms and individual patient factors that may lead to rare cases of ipsilateral weakness.