Editing Expressive aphasia (section)

==== Common causes ====
The most common cause of expressive aphasia is [[stroke]]. A stroke is caused by hypoperfusion (lack of oxygen) to an area of the brain, which is commonly caused by [[thrombosis]] or [[embolism]]. Some form of aphasia occurs in 34 to 38% of stroke patients.<ref name="Bakheit">{{cite journal|last1=Bakheit|first1=AMO|last2=Shaw|first2=S|last3=Carrington|first3=S|last4=Griffiths|first4=S|year=2007|title=The rate and extent of improvement with therapy from the different types of aphasia in the first year of stroke|journal=Integumentary Rehabilitation|volume=21|issue=10|pages=941–949|doi=10.1177/0269215507078452|pmid=17981853|s2cid=25995618}}</ref> Expressive aphasia occurs in approximately 12% of new cases of aphasia caused by stroke.<ref name="Pedersen">{{cite journal|last1=Pedersen|first1=PM|last2=Vinter|first2=K|last3=Olsen|first3=TS|year=2004|title=Aphasia after stroke: Type, severity, and prognosis - The Copenhagen aphasia study|journal=Cerebrovascular Diseases|volume=17|issue=1|pages=35–43|doi=10.1159/000073896|pmid=14530636|s2cid=11754713}}</ref>

In most cases, expressive aphasia is caused by a stroke in Broca's area or the surrounding vicinity. Broca's area is in the lower part of the [[premotor cortex]] in the language dominant hemisphere and is responsible for planning motor speech movements. However, cases of expressive aphasia have been seen in patients with strokes in other areas of the brain.<ref name=":1" /> Patients with classic symptoms of expressive aphasia in general have more acute brain lesions, whereas patients with larger, widespread lesions exhibit a variety of symptoms that may be classified as [[global aphasia]] or left unclassified.<ref name="Bakheit" />

Expressive aphasia can also be caused by trauma to the brain, [[tumor]],  [[cerebral hemorrhage]]<ref name="Ozeren">{{cite journal|last=Orzeren|first=A|author2=F Koc|author3=M Demirkiran|author4=A Sonmezler|s2cid=23023504|year=2006|title=Global aphasia due to left thalamic hemorrhage|journal=Neurology India|volume=54|issue=4|pages=415–417|doi=10.4103/0028-3886.28118|pmid=17114855|doi-access=free}}</ref> and by [[extradural abscess]].<ref name="Commondoor">{{cite journal|author1=Commondoor, R.|author2=Eisenhut, M.|author3=Fowler, C.|author4=Kirollos, R. W.|author5=Nathwani, N.|name-list-style=amp|year=2009|title=Transient Broca's Aphasia as Feature of an Extradural Abscess|journal=Pediatric Neurology|volume=40|issue=1|pages=50–53|doi=10.1016/j.pediatrneurol.2008.06.018|pmid=19068255}}</ref>

Understanding [[lateralization of brain function]] is important for understanding which areas of the brain cause expressive aphasia when damaged. In the past, it has been believed that the area for language production differs between left and right-handed individuals. If this were true, damage to the homologous region of Broca's area in the right hemisphere should cause aphasia in a left-handed individual. More recent studies have shown that even left-handed individuals typically have language functions only in the left hemisphere. However, left-handed individuals are more likely to have a dominance of language in the right hemisphere.<ref name="Purves" />