A 56-year-old right-handed man comes to the physician with right-sided weakness and speech difficulty. He speaks in short sentences with considerable effort. He fully follows written and verbal commands but has difficulty writing and repeating. Which of the following lesion locations is most likely responsible for the observed findings?

Question

A 56-year-old right-handed man comes to the physician with right-sided weakness and speech difficulty.  He speaks in short sentences with considerable effort.  He fully follows written and verbal commands but has difficulty writing and repeating.  Which of the following lesion locations is most likely responsible for the observed findings?

Quizplus · Accepted Answer

This patient most likely has an ischemic stroke affecting the dominant frontal lobe (left) in the left middle cerebral artery (MCA) territory. Nearly 95% of right-handed and up to 70% of left-handed people are left-hemisphere dominant for verbal and written language function. Patients with lesions affecting the posterior inferior frontal gyrus (Broca's area) can comprehend and follow commands but are unable to verbalize or write properly (expressive aphasia). Broca's lesions can also affect the neurologic pathway from that brain region to the motor function of the larynx and mouth. 11ec25c8_d5ac_5380_bc81_ef05dd81c880_MD0003_00 In rare instances, the lesions can extend and affect the arcuate fasciculus to impair the patient's ability to repeat phrases (conduction aphasia). An easy way to remember is that Broca's aphasia often represents a broken speech system. Patients with injury to the lateral frontal lobe can also develop contralateral weakness of the face and extremities (motor cortex) and conjugate gaze deviation to the side of the lesion (contraversive frontal eye fields). In contrast, patients with Wernicke's aphasia have difficulty comprehending and following commands but are able to speak fluently. However, their speech tends to be rambling without concrete meaning. (Choices B and E) Dominant parietal lobe lesions can present with contralateral sensory loss (eg, pain, vibration, agraphesthesia, astereognosis) and contralateral inferior homonymous quadrantanopsia due to superior optic radiations involvement. Nondominant parietal lobe lesions typically cause anosognosia (denial of one's disabilities) and contralateral apraxia (inability to carry out learned purposeful movements). (Choice C) Dominant temporal lobe lesions can affect comprehension (receptive aphasia), ability to speak nouns (anomic aphasia), repetition (conductive aphasia) due to arcuate fasciculus involvement, and contralateral superior homonymous quadrantanopsia due to inferior optic radiations (Meyer's loop) involvement. However, patients usually have intact expressive speech, motor, and primary sensory functions. (Choice D) Nondominant frontal lobe lesions typically affect the way a person conveys emotion through speech (motor aprosodia), contralateral weakness, and apraxia. However, these lesions do not cause expressive aphasia, as seen in this patient. (Choice F) Nondominant temporal lobe lesions can impair ability to comprehend emotional gestures (sensory aprosodia). These patients can also develop a contralateral homonymous quadrantanopsia due to the inferior optic radiations involvement. Educational objective: Dominant frontal lobe lesions can cause expressive (Broca's) aphasia, contralateral hemiparesis due to involvement of the primary motor cortex, and contralateral apraxia due to involvement of the supplementary motor cortex. References: Broca's area: rethinking classical concepts from a neuroscience perspective. (http://www.ncbi.nlm.nih.gov/pubmed/21239364)

A 56-Year-Old Right-Handed Man Comes to the Physician with Right-Sided