Anatomy of a Stroke Barb Merriman, D.O. PGY-4 Neurology Resident 11/4/2016

Transcription

1 Anatomy of a Stroke Barb Merriman, D.O. PGY-4 Neurology Resident 11/4/2016 1

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6 ASPECT Score A way to assess the size and potential outcome of stroke in Middle Cerebral Artery territory Perfect score = 10. One point is subtracted for early ischemic change in each of 10 defined regions on head CT Normal CT Score = 10 Stroke of entire MCA territory Score = 0 The lower the score, the more likely patient will have a poor outcome 6

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9 Admission to MICU Discussion with family about unfortunate realities: Core infarct to Left MCA Superior division Irreversible, permanent loss of language Further intervention = high risk of hemorrhage Mortality: Hemorrhage > infarction Morbidity: Infarction > hemorrhage Likely unable to understand speech, or to speak, read, and write Possible right-side hemiparesis and hemi anesthesia Loss of both personal and Commercial Driver s License 9

10 Definition: Language Noun: A shared code for representing concepts through the use of symbols, and includes spoken, written, and non-verbal/gestural components. Verb: The act of executing complex mental processes to communicate. Language Components Language Components Speaking Listening Reading Writing are heavily influenced by a person s Attention Memory Executive function Life experiences Age Personality 10

11 Language and the Dominant Hemisphere Primary Motor and Primary Sensory Cortex Unimodal Motor, Unimodal Sensory Cortex Heteromodal Association Cortices Motor and Sensory Cortices 11

12 Localization Basic Language Centers Damage to Broca s Area = a motor impairment Impairment to complex speech formulation, planning, and grammer Listeners hear impaired speech fluency Phrase length = 1-4 words, mostly nouns, lacking functional words Comprehension of language is relatively intact Speech is effortful, with a lack of grammatical structure and monotonous sound Localization Basic Language Centers Damage to Wernicke s Area = A sensory impairment Markedly impaired comprehension of language Do not respond appropriately to questions Do not follow commands Often make paraphasic errors Often give irrelevant responses Speech is fluent, but empty, meaningless, nonsensical. Patient may appear unaware of their deficit despite markedly abnormal speech full of paraphasic jargon. 12

13 Language: Multiple Integrated Centers To hear a word and repeat it: Hear sound with ears Sound transmitted to Wernicke s Area Transmitted to Broca s Area via Arcuate Fasciculus (subcortical interconnecting pathway) white matter tract Transmitted to primary motor cortex where words converted to sound by the diaphragm, tongue, and mouth Broca s and Wernicke s Interconnection 13

14 Lateralization: Dominant vs Non-dominant Hemispheres Dominant (usually left hemisphere) language functions: Language comprehension and production Skilled language planning/formulation Grammatical structure of sentences Non-dominant (usually right hemisphere) language functions: Prosody (variation in pitch, melody, cadence, loudness/softness, and pauses when we speak) Interprets subtle voice inflections (sarcasm, joy, anger) and body language/gestures Left to right bi-directional pathway: Corpus Callosum Heavily myelinated (insulated) interconnecting tracts Integrate all language functions from both hemispheres Left and Right Hemisphere Interconnection 14

15 Putting it all Together Speech production depends on complex interactions between many focal regions of the brain, connected by widely distributed multi-directional interconnecting pathways throughout both hemispheres. The direction and coordination of these pathways is done by sophisticated planning centers in the dominant hemisphere. Following Left MCA stroke, studies show its not as simple as nearby brain regions taking over for lost functional areas. Some studies show that left to right connecting tracts may allow right side mirror image regions to take over some of the functions damaged in left brain strokes to facilitate partial recovery. More recent studies suggest that remaining language-specific networks learn to interact differently with remaining domain-general systems, with highly variable degrees of functional recovery. Language: Summary Large amount of the brain s surface area dedicated to language (left hemisphere + right hemisphere + interconnecting white matter tracts). Much of the size difference between human brain vs. other animals can be attributed to the sophistication of language function found in both cerebral hemispheres. Aphasia occurs when hemispheric strokes disrupt the overlapping and interconnecting language circuits between focal language centers and domaingeneral regions. Outcomes vary widely as a result and prognosis difficult to predict. 15

16 References 1. Blumenfeld H. Neuroanatomy through Clinical Cases. 2nd ed. Sunderland, Massachusetts: Sinauer Associates, Murray L, Clark H. Neurogenic Disorders of Language and Cognition: Evidencebased Clinical Practice. 2nd ed. Austin, Texas: Pro-Ed, Inc., Caplan LR, Van Gijn J. Stroke Syndromes. 3rd ed. Cambridge, United Kingdom: Cambridge University Press,