Description
An ischemic stroke is defined by the abrupt loss of blood flow to a region of the brain, which is followed by an impairment of neurologic function. The thrombotic or embolic occlusion of a cerebral artery causes acute ischemic stroke, which occurs more frequently than hemorrhagic stroke. Stroke assessment is traditionally aided by clinical localization, in which presenting deficits are linked to specific arterial locations in the brain. Although they are essential for delivering evidence-based stroke care, clinical localization skills are rarely taught to non-neurologists. They enable rapid patient identification, diagnosis, and, ultimately, the administration of immediate treatment. Despite advanced neuroimaging and laboratory research, technology cannot replace the clinician's history and examination-based anatomical localisation. Standard imaging tests may overlook lesions unless they are narrowly focused on the anatomical region thought to be affected. Understanding the system's architecture, physiology, blood supply, and the disease processes that influence it are necessary for localization.
Résumé
- The presentation discusses the anatomical localization of ischemic stroke, emphasizing the importance of clinical examination and imaging for accurate diagnosis. It highlights the need to differentiate between cortical, corona radiata, internal capsule, and brain stem lesions based on clinical findings such as cortical sensations and cranial nerve function.
- The presenter uses a case scenario of a 70-year-old man with right-sided weakness to illustrate the process of anatomical localization. They explain how to rule out different locations based on whether cortical sensations are intact, the presence of cranial nerve palsies, and the pattern of weakness in the upper and lower limbs. The case concludes it is likely an infarction in the left internal capsule, possibly due to thrombosis.
- The lecture delves into the arterial supply of the brain, focusing on the anterior and middle cerebral arteries. It explains the significance of the A1 and A2 segments of the anterior cerebral artery, highlighting that isolated A1 segment blockage can be asymptomatic due to collateral flow. Blockage of the A2 segment leads to lower limb weakness and frontal lobe dysfunction due to its supply to the medial surface of the cerebrum.
- It explains that a block of the Artery of Heubner can impact the internal capsule area associated with face and Upper Limb control. Specific scenarios include combinations of A2 and Heubner artery blocks, resulting in distinct hemiparesis patterns. A congenital absence of one side's A1 segment is discussed, and the consequences of blockage on the other side are detailed.
- The presenter also details M1 and M2 (superior and inferior) branches of the Middle Cerebral Artery, describing effects of various blockages in those territories. M1 blockages have penetrating branches that have internal capsule implications. The inferior branches have Wernicke's implications on language and superior visual fields.
- Posterior circulation strokes involving the vertebral and basilar arteries are also explained. Damage at the thalomogeniculate branch can impact sensation and visual field. Impact on midbrain and upper areas can impact cranial nerve function that also effects muscle use. The speaker then goes through pontine and medullary stroke issues to describe where certain symptoms can localize.
- The presentation highlights the critical distinction between medial and lateral medullary syndromes. Medial medullary syndrome can cause hemiparesis, while lateral medullary syndrome might not present with limb weakness. Lateral medullary syndrome instead manifests with vertigo, Horner's syndrome, cranial nerve deficits (9th and 10th), and loss of pain/temperature sensation. Subtle findings such as persistent hiccups can indicate the need for a detailed neurological examination.
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