WBR0532

Author	[[PageAuthor::Yazan Daaboul, M.D. (Reviewed by Serge Korjian and Yazan Daaboul, M.D.)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Pathophysiology
Sub Category	SubCategory::Neurology
Prompt	[[Prompt::A 57-year-old man, with a history of type II diabetes mellitus, hypertension, and hyperlipidemia, is brought to the emergency department in cardiac arrest. Following resuscitation and appropriate work-up, the patient is supported by venoatrial (VA) extracorporeal membrane oxygenation (ECMO) for salvage therapy. Several days later, the patient wakes up; and a neurological examination demonstrates early hypoxic brain injury. What are the most likely findings on neurological examination in this patient?]]
Answer A	AnswerA::Memory loss and dysmetria
Answer A Explanation	[[AnswerAExp::The hippocampus and cerebellum are 2 very vulnerable regions in the brain that are usually first affected by ischemic brain injury. Injury to the hippocampus causes memory loss, and injury to the cerebellum causes dysmetria (abnormal finger-to-nose test on physical examination).]]
Answer B	AnswerB::Broca's aphasia and vision loss
Answer B Explanation	AnswerBExp::Patients with lesions of the temporal lobe and the occipital lobe present with Broca's aphasia and vision loss, respectively. The temporal and occipital lobes are not the most susceptible areas in the brain to ischemic injury.
Answer C	AnswerC::Disorientation and bell's palsy
Answer C Explanation	[[AnswerCExp::Disorientation is common in injury to the hippocampus; but injury to the brainstem with involvement of cranial nerve (CN) VII (facial nerve) to cause Bell's palsy is not as common as hippocampal and cerebellar injuries in ischemic brain injury.]]
Answer D	AnswerD::Deviated uvula and positive Romberg sign
Answer D Explanation	AnswerDExp::Although Romberg sign suggests cerebellar injury, deviated uvula is a sign of CN X (vagal nerve) injury in the brainstem. The brainstem is not considered one of the most susceptible regions of the brain during ischemic injury.
Answer E	AnswerE::Positive Babinski sign and muscle fasciculations
Answer E Explanation	[[AnswerEExp::Positive Babinski sign signifies lesion of the upper motor neuron (UMN); whereas muscle fasciculations signify lesions of the lower motor neuron (LMN). There is no reason in this patient to have LMN injury. As such, muscle fasciculations are an unlikely finding in this patient.]]
Right Answer	RightAnswer::A
Explanation	[[Explanation::Extracorporeal membrane oxygenation (ECMO) is a short-term salvage technique whereby the cardiopulmonary circulation is bypassed by means of blood drainage from the circulation peripherally via a femoral vein or centrally via cannulation of the right atrium. ECMO has 2 configurations: First, a veno-venous (VV) configuration that provides adequate extracorporeal oxygenation in the case of respiratory failure; and second, a veno-arterial (VA) configuration to provide both cardiac and pulmonary support. ECMO is frequently used in post-cardiotomy patients who cannot get off cardiopulmonary bypass, in those with severe heart failure, in patients with cardiac arrest for a short period of time with likelihood of recovery, and in pediatric patients in cases of respiratory distress syndrome (RDS). The patient described above recovered following a cardiac arrest by means of ECMO support. Nonetheless, neurological damage following recovery from a cardiac arrest is not uncommon due to brain hypoxia that occurs very rapidly following cardiac arrest. The most susceptible regions in the brain that are often first affected by ischemic brain disease are the hippocampus, neocortex, the cerebellum, and watershed areas (border-zone areas in the brain that normally receive less blood supply and are thus more susceptible to injury). As a result, the patient is expected to have memory loss, due to ischemic injury to the hippocampus, and dysmetria, due to ischemic injury to the cerebellum. Educational Objective: The hippocampus, neocortex, cerebellum, and watershed areas in the brain are especially susceptible to ischemic brain injury and are often the first to be affected following brain hypoxia. References: Marasco SF, Lukas G, McDonald M, et al. Review of ECMO (Extra Corporeal Membrane Oxygenation) support in critically ill adult patients. Heart Lung Circ. 2008; 17 (Suppl 4):S41-7. First Aid 2014 page 463]]
Approved	Approved::Yes
Keyword	WBRKeyword::ECMO, WBRKeyword::Extra corporeal membrane oxygenation, WBRKeyword::Cerebellum, WBRKeyword::Hippocampus, WBRKeyword::Hypoxia, WBRKeyword::Ischemia, WBRKeyword::Neocortex, WBRKeyword::Brain
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::