Overview
This lecture covers brainstem stroke localization, key clinical syndromes, and associated arteries, emphasizing patterns such as “crossed findings” for diagnosis.
Recognizing Brainstem Strokes
- Crossed findings (face deficits opposite body deficits) suggest a brainstem stroke.
- Three key localization questions: 1) Which brainstem region (midbrain, pons, medulla)? 2) Medial or lateral? 3) Right or left side?
Localizing Brainstem Lesions
- Use cranial nerves to identify the brainstem level: 3-4 (midbrain), 5-8 (pons), 9-12 (medulla).
- Medial structures (“M”): motor pathway, medial lemniscus, medial longitudinal fasciculus, motor cranial nerves.
- Lateral structures (“S”): spinocerebellar tract, spinothalamic tract, sympathetic pathway, sensory trigeminal nuclei.
- Face deficits are usually ipsilateral; body deficits are contralateral.
Classic Brainstem Stroke Syndromes and Arteries
- Medial Medullary Syndrome: Contralateral body weakness, ipsilateral tongue weakness, caused by anterior spinal artery stroke.
- Lateral Medullary Syndrome: Contralateral body and ipsilateral face protopathic sensory loss, ataxia, vertigo, Horner’s syndrome, dysphagia, caused by posterior inferior cerebellar artery (PICA) stroke.
- Lateral Pontine Syndrome: Similar to lateral medullary but with cranial nerves 5-8 involvement, facial sensory loss, hearing loss, caused by anterior inferior cerebellar artery (AICA) stroke.
- Medial Pontine Syndrome: Facial asymmetry, horizontal gaze palsy, internuclear ophthalmoplegia, caused by basilar artery branch occlusion.
- Medial Midbrain Stroke (Weber Syndrome): Ipsilateral oculomotor palsy and contralateral hemiplegia, involves the midbrain.
- Basilar Artery Stroke: Can cause “locked-in syndrome” with total body paralysis but preserved awareness and possible eye movement for communication.
Key Terms & Definitions
- Crossed Findings — Opposite-side deficits in face and body suggesting brainstem lesion.
- Medial/Lateral — Refers to lesion location within brainstem (middle vs. side).
- Protopathic Sensation — Crude touch, pain, temperature.
- Epicritic Sensation — Fine touch, vibration, proprioception.
- Locked-In Syndrome — Complete paralysis with intact consciousness due to pontine damage.
Action Items / Next Steps
- Practice knowledge using case questions.
- Review brainstem cranial nerve nuclei and their functions.
- Memorize artery-syndrome associations for exams.