A 55-year-old right-handed man comes to the emergency department due to persistent right arm tingling and numbness for the past several hours. The patient has no headache, muscle weakness, slurred speech, or difficulty ambulating. He has a history of hypertension, paroxysmal atrial fibrillation, and ischemic stroke without residual symptoms. Anticoagulation was discontinued 2 months ago after he developed a gastrointestinal hemorrhage. Blood pressure is 150/90 mm Hg, and pulse is 92/min and regular. While the patient is being evaluated, his right arm paresthesia spreads to the entire right side of the body and he develops right-sided convulsions, followed by a bilateral tonic-clonic seizure. Which of the structures in the left cerebral hemisphere is the most likely site of origin of this patient's seizure?

Question

A 55-year-old right-handed man comes to the emergency department due to persistent right arm tingling and numbness for the past several hours.  The patient has no headache, muscle weakness, slurred speech, or difficulty ambulating.  He has a history of hypertension, paroxysmal atrial fibrillation, and ischemic stroke without residual symptoms.  Anticoagulation was discontinued 2 months ago after he developed a gastrointestinal hemorrhage.  Blood pressure is 150/90 mm Hg, and pulse is 92/min and regular.  While the patient is being evaluated, his right arm paresthesia spreads to the entire right side of the body and he develops right-sided convulsions, followed by a bilateral tonic-clonic seizure.  Which of the structures in the left cerebral hemisphere is the most likely site of origin of this patient's seizure?

Quizplus · Accepted Answer

11ec160b_35c5_80f0_9249_cb27e1a16d35_MD0001_00 This patient with a history of paroxysmal atrial fibrillation was taken off anticoagulation following a gastrointestinal bleed and is likely suffering from a recurrent embolic stroke complicated by seizure. Stroke is one of the most common causes of seizure, which occurs due to the release of excitotoxic neurotransmitters in the ischemic brain region. Initial manifestations of a seizure vary based on which brain region is affected by the underlying pathology. The primary somatosensory cortex is responsible for processing all somatic sensory input from the contralateral side of the body; therefore, a seizure in this area of the cortex would result in contralateral sensory disturbances. This patient's initial right arm numbness and paresthesia was likely caused by a focal onset seizure originating in the left primary somatosensory cortex (postcentral gyrus). The patient subsequently developed right-sided convulsions due to spread of the seizure along the lateral brain convexity to the primary motor strip (precentral gyrus) (Choice C). Shortly after, the seizure activity spread to both cerebral hemispheres, resulting in tonic-clonic convulsions. (Choice A) The frontal eye field is the region of the cerebral cortex that controls horizontal eye movement. Activation of the left frontal eye field during a seizure would cause the eyes to deviate horizontally to the right. After the seizure, the patient's eyes may temporarily deviate to the left due to postictal neuroinhibition. (Choice B) The motor speech (Broca) area is located in the posterior inferior frontal gyrus of the dominant (usually left) hemisphere and is responsible for controlling expressive speech/language. A seizure involving this area of the brain would likely result in uncontrolled vocalization or expressive aphasia. (Choice E) The sensory speech (Wernicke) area is located in the posterior superior temporal gyrus of the dominant hemisphere and is responsible for language comprehension. A seizure in this area of the temporal lobe would likely result in fluent aphasia with impaired comprehension or auditory auras. (Choice F) The primary visual cortex in the occipital lobe is responsible for processing visual information from the contralateral homonymous visual fields. A seizure originating from the left primary visual cortex would likely result in visual hallucinations affecting the right homonymous visual fields. Educational objective: The primary somatosensory cortex (postcentral gyrus) is responsible for processing all somatic sensory input from the contralateral side of the body. A focal onset seizure originating in this region of the cerebral cortex often results in contralateral sensory disturbance (eg, numbness, paresthesia). __________ References: Symptoms in focal sensory seizures. Clinical and electroencephalographic features. (http://www.ncbi.nlm.nih.gov/pubmed/15642493)

A 55-Year-Old Right-Handed Man Comes to the Emergency Department Due