Exam 2: Section 3

Abstract

This practical question and answer book contains two full-length practice exams that mimic the tone and scope of the American Board of Psychiatry and Neurology’s certifying exam in neurocritical care. It covers aspects of neurology, neurosurgery, general critical care, and emergency medicine, with rationale and discussion provided in the answers section at the end of each exam. This useful study guide will help prepare critical care fellows and residents from a variety of backgrounds for the ABPN exam, and help test their critical care competencies in general.

Section 3: Answers

• 1. The correct answer is D. This patient’s CT scan demonstrates bilateral thalamic infarcts. The artery of Percheron is an anatomic variant in which a single vessel arises from the posterior cerebral artery to feed the bilateral thalamic and midbrain structures, and an occlusion of this vessel would explain this patient’s presentation. The artery of Adamkiewicz is a large anterior medullary artery that supplies blood to the thoracolumbar spinal cord, and an occlusion here can result in an anterior cord syndrome. The artery of Drummond is a colonic vessel that connects the superior and inferior mesenteric arteries, and provides collateral blood flow. The recurrent artery of Heubner is a branch of the anterior cerebral artery that supplies blood to the caudate and internal capsule, and an occlusion here may result in contralateral hemiparesis. Finally, the artery of Samson is a uterine vessel of little clinical significance.

• 2. The correct answer is E. The RASS score is used as an objective measure of a patient’s level of either agitation or sedation, and ranges from +4 to −5. The scores are as follows: +4, combative and frankly violent; +3, aggressive behavior and pulling on tubes/lines; +2, agitated with frequent non-purposeful movements; +1, restless and anxious; 0, alert and calm; −1, drowsy, but with sustained (>10 s) eye contact to voice; −2, drowsy, with only brief (<10 s) eye contact to voice; −3, drowsy, with no eye contact to voice; −4, no response at all to voice, but moves with physical stimulation; −5, unarousable.

• 3. The correct answer is A. The Monro-Kelly doctrine states that intracranial volume is fixed, and is comprised of three components blood, cerebrospinal fluid, and brain tissue. Any increase in one of those components is accompanied by a decrease in one or both of the other two.

• 4. The correct answer is B. Depressed skull fractures are associated with a number of potential complications. There is, however, no evidence that post-traumatic epilepsy can be prevented by immediate dural repair. All of the other answer choices are correct [1].

• 5. The correct answer is D. Although cerebral venous sinus thrombosis is usually diagnosed via CT or MR venography, conventional angiography remains the diagnostic gold standard. Transcranial doppler is primarily used to measure flow velocities in the proximal anterior and middle cerebral arteries, particularly in the setting of suspected vasospasm [2].

• 6. The correct answer is C. Even brief exposures to excessive tidal volumes have been shown to be related to the development of ventilator associated lung injury and ARDS; this patient is currently hypocarbic, and is receiving >8 cc/mL tidal volume. While it would certainly be reasonable to examine whether her fraction of inspired oxygen or PEEP should be titrated down, the most important first step would be to adjust her tidal volume appropriately [3].

• 7. The correct answer is E. Aerophobia (and more notoriously, hydrophobia) are common symptoms of rabies encephalitis, along with myoclonic jerking, altered mental status, and coma. The disease is fatal in a majority of patients, though there are an increasing number of survivors reported in the literature [4].

• 8. The correct answer is E. There is no reliable serum alcohol cutoff that will ensure a patient will not experience alcohol withdrawal seizures. Furthermore, patients with a history of chronic and severe alcohol abuse may go into withdrawal at serum levels which would be otherwise incapacitating to average individuals.

• 9. The correct answer is E. The vasculitides are a broad class of diseases that involve the inflammatory destruction of both arterial and venous blood vessels. All of the disease listed may present with central nervous system involvement.

• 10. The correct answer is B. Though SIADH and cerebral salt wasting may be seen in brain injury, the most likely cause of polyuria in this patient is diabetes insipidus. Ischemia of the supraoptic nuclei and posterior pituitary lead to loss of intrinsic vasopressin, and results in central diabetes insipidus.

• 11. The correct answer is C. Although this patient’s overall prognosis is poor, the presence of the IDH1 mutation actually confers a slightly better outcome as compared to the wild-type IDH gene. The remainder of the answer choices are correct [5].

• 12. The correct answer is B. Introduction of PEEP increases end-expiratory intrathoracic pressure, which impedes venous return and may cause a reduction in cardiac output. A decrease in urine output caused by PEEP has been attributed to multiple factors, such as decreases in cardiac output and renal blood flow, reduced intravascular volume, activation of sympathetic and renin-angiotensin-aldosterone-antidiuretic hormone systems, and suppression of atrial natriuretic peptide. Addition of PEEP decreases left-ventricular afterload by increasing intrathoracic pressure, thereby reducing transmural left ventricular pressure and afterload. Elevated intrathoracic pressures due to PEEP may also lead to compression of alveolar blood vessels and a rise in right ventricular afterload due to an increase in pulmonary vascular resistance. PEEP also leads to increased alveolar recruitment and opening of dependent lung units, leading to an increase in FRC.

• 13. The correct answer is B. The free water deficit for an adult female is as follows: (0.5 × weight in kg) × [(serum sodium/140) -1]. For adult males, the initial multiplier is 0.6. In this case: (0.5 × 60) × [(160/140) – 1] = ~4.2 L.

• 14. The correct answer is A. Light’s criteria favoring transudative effusion are as follows: pleural fluid protein to serum protein <0.5, pleural fluid LDH to serum LDH <0.6, or pleural fluid LDH <2/3rd upper limit of normal for serum level. In this case, the fluid sample indicates this is likely a transudative effusion.

• 15. The correct answer is B. Amphotericin B, ceftriaxone, and erythromycin do not require a change in drug dosing during renal replacement therapy. Vancomycin, however, requires dosing adjustments during both continuous renal replacement therapy and intermittent hemodialysis. Catecholamines, such as norepinephrine, can be initiated at normal doses and titrated to effect.

• 16. The correct answer is B. The majority of cases of diverticulitis are uncomplicated. Complicated diverticulitis refers to cases of abscess formation, fistulization, stricture, and perforation. Gross hematochezia can be seen in simple diverticulosis and is one of the most common causes of lower GI bleeding [6].

• 17. The correct answer is B. Muromonab is an anti-CD3 monoclonal antibody, and the most commonly encountered adverse reactions are aseptic meningitis and a flu-like illness. Cyclosporine and tacrolimus are calcineurin inhibitors; both are associated with fine motor tremor, seizures, and a number of other neurologic adverse events. Mycophenolate commonly causes headaches.

• 18. The correct answer is B. Patients with central (non-infectious) fever may pose both a diagnostic and therapeutic dilemma for ICU providers. Intraventricular hemorrhage, subarachnoid hemorrhage, and traumatic brain injury are well-described causes. The use of external cooling blankets, cold-water adhesive pads, and acetaminophen may prove sufficient in most cases. Bromocriptine, a dopamine agonist that acts to control hypothalamic dysfunction, has also been reported to be effective in cases of recalcitrant central fever. Octreotide, a somatostatin analog, has no antipyretic effect.

• 19. The correct answer is E. The patient has severe community acquired pneumonia and several risk factors for ICU admission; his CURB 65 score is 4. Noninvasive positive pressure ventilation may be used to successfully treat patients with respiratory failure from a COPD exacerbation provided they are hemodynamically stable, alert, and able to protect their airway. While there are several possible reasons for his clinical deterioration including hypercapnia and primary cardiac pathology, he is now hemodynamically unstable and minimally responsive, and requires urgent intubation and mechanical ventilation [7].

• 20. The correct answer is B. Of the options listed, T wave inversions are the most commonly seen EKG abnormality in patients with a myriad of primary neurological diseases, including intracerebral hemorrhage. Cerebral T waves are classically defined as T-wave inversions of ≥5 mm in depth in ≥4 contiguous precordial leads [8].

• 21. The correct answer is E. All of the following are correct regarding the NEXUS criteria for cervical spine clearance, with the exception of an age requirement. This is in contrast to the Canadian cervical spine rule, although both are used in clinical practice [9, 10].

• 22. The correct answer is C. Although treatment with dexamethasone has been found to be associated with decreased recurrence of chronic SDH, it is not associated with improved mortality, and patients on dexamethasone may experience significant adverse events. A combination of inflammatory changes, dural cell proliferation, angiogenesis, and fibrinolysis play a crucial role in the development and growth of chronic SDH. Maturation of membranes is associated with bleed hypodensity [11].

• 23. The correct answer is E. In males who are unable to void, a urine volume of greater than or equal to 300 mL suggests urinary retention. All of the other answer choices are below this threshold.

• 24. The correct answer is B. The focused assessment with sonography in trauma (FAST) is an integral component of the rapid assessment of the patient with thoraco-abdominal trauma. FAST provides the ability to rapidly identify hemothorax, hemoperitoneum, hemopericardium and pneumothorax. This ultrasound image of the right upper quadrant demonstrates fluid within the hepatorenal recess (Morrison’s pouch). While ascites and fresh blood are indistinguishable on ultrasound, in the setting of thoraco-abdominal trauma, one must assume that peritoneal free fluid represents blood.

• 25. The correct answer is C. Mycotic cerebral aneurysms may form as a consequence of infectious processes such as endocarditis or meningitis. Despite their name, they can be caused by bacterial, viral, fungal, or parasitic infections—Osler’s initial description of a “mushroom” shaped aneurysm in the 1800s can be blamed for the confusion. Unruptured aneurysms can be monitored with serial imaging after the infectious process has been treated appropriately. Ruptured aneurysms generally require either surgical or endovascular treatment [12].

• 26. The correct answer is A. Reduction of compound muscle action potentials reflects a loss of motor axons. The findings in CIP are usually symmetrical. Conduction velocities are usually normal or slightly reduced, and F-wave latencies are usually normal or near normal. Sensory action potential amplitude is significantly reduced in CIP [13].

• 27. The correct answer is E. Seizure activity may result from a toxic ingestion of a variety of substances. This paradoxically include medications that are central nervous system depressants and more traditionally associated with sedative properties at standard doses, including clonidine, meperidine, and baclofen.

• 28. The correct answer is A. The injury above is consistent with a Brown-Sequard lesion (cord hemisection). Specifically, the lesion refers to an injury of the left half of the spinal cord, with impaired ipsilateral motor function and contralateral nociception.

• 29. The correct answer is B. Patients on oral vitamin K antagonists with traumatic subarachnoid hemorrhage are at significant risk of deterioration, re-bleeding, and death. Resuscitative targeting of an INR < 1.5 is appropriate to reduce this risk.

• 30. The correct answer is A. Dural arteriovenous fistulae (AVF) may present with pulsatile tinnitus, particularly if they drain into the transverse or sigmoid sinus. The Barrow classification system is used to describe cavernous carotid fistulae (CCF), not dural AVF. CCF may present with vision loss and the presence of an orbital bruit. Dural AVF may be treated surgically, endovascularly, or via stereotactic radiosurgery. They may also recur after treatment.

• 31. The correct answer is C. A significant number of patients with TCD elevation will never develop ischemia, even in the absence of any intervention. Given the lack of clinical symptoms, aggressive fluid resuscitation and blood pressure augmentation may harm this patient. Instead, volume repletion as needed based on hemodynamic monitoring is preferred. Conventional angiography is traditionally reserved for significant delayed ischemic neurologic deficits with intention to treat vasospasm intra-arterially.

• 32. The correct answer is C. Bougie-guided intubation may be necessary in the absence of an adequate view of the vocal cords. The upturned end is slid under the epiglottis, feeling for the tracheal rings and eventual resistance when the bougie hits the carina. The laryngoscope blade can then be removed, and an endotracheal tube can be advanced along the bougie into the trachea.

• 33. The correct answer is E. Intraventricular hemorrhage without involvement of the parenchyma is relatively uncommon, and may be related to the presence of an aneurysm, vascular malformation, or tumor contiguous with the ventricles. Far more common is intraventricular hemorrhage as a result of extension of a parenchymal lesion [14].

• 34. The correct answer is B. Renal replacement therapy should be initiated early in the critically ill patient as it is dangerous to wait for complications to appear before intervening. Criteria for initiation of renal replacement therapy for chronic renal failure may be inappropriate in critically ill patients. Current evidence does not support the view that continuous renal replacement therapy is superior to peritoneal dialysis and conventional intermittent hemodialysis. Continuous renal replacement therapies allow lower average serum urea levels compared to intermittent therapies and avoids dangerous peaks of solute increase. The removal of unwanted solvent or water is done through the process called ultrafiltration, whereas removal of unwanted solutes is achieved through the process of diffusion [15].

• 35. The correct answer is C. The cuff leak test involves deflating the endotracheal balloon, followed by measuring the volume of air that escapes from the otherwise-closed ventilator circuit. It is intended to be a surrogate measure of laryngeal edema. The maneuver is far from perfect when it comes to predicting which patients will and will not be successfully extubated, and several confounding variables may exist (such as the presence of crusted secretions around the endotracheal tube). However, a number of studies have repeatedly demonstrated a high negative predictive value for post-extubation stridor when the cuff leak exceeds 100 ml [16].

• 36. The correct answer is A. This patient has central neurogenic hyperventilation (CNH), which is a rare condition that results in hyperventilation persisting in sleep and resulting in low PaCO₂, high PaO₂, and a high pH in the absence of any pharmacologic or metabolic conditions. It has been hypothesized that CNH results from uninhibited stimulation of both the inspiratory and expiratory centers in the pons and medulla. Cheyne-Stokes respiration is a more regular crescendo-decrescendo breathing followed by periods apnea. Apneustic breathing is a sustained deep inspiration lasting few seconds followed by rapid exhalation and a brief post expiratory pause. Ataxic breathing is another rare breathing pattern consisting of erratic rate and depth of breathing, interspersed with episodes of apnea. Ataxic breathing is one of the few true localizing breathing patterns, and should always raise the suspicion of a medullary infarct. Cluster breathing consists of irregular clusters of breaths followed by apneic periods of variable duration.

• 37. The correct answer is D. This patient has experienced an aneurismal subarachnoid hemorrhage, and is within the first 24 h of symptom onset. Rebleed, hydrocephalus and seizures are all reasonable explanations for her decline. The risk of vasospasm, on the other hand, generally does not occur until at least 3 days after ictus, peaks around 7 days, and fades around day 14. Hyperacute vasospasm has been described in both animal models and case series of intraoperative aneurysm rupture, but this occurs within minutes of ictus, not 18 h later [17].

• 38. The correct answer is B. This patient is in status asthmaticus and severe respiratory distress. These patients will often present with hypocapnia secondary to hyperventilation. “Normalization” of the pCO₂ is an ominous sign, and portends impending respiratory failure. Therefore, this patient should be intubated immediately and admitted to the ICU.

• 39. The correct answer is C. Posterior fossa hemorrhage is a life-threatening condition, secondary to the small, tight spaces involved. About 15% of hemorrhages in the posterior fossa also involve some component of the brainstem [18].

• 40. The correct answer is E. All of the choices listed represent the postulated mechanisms for the development of increased ICP during RRT. Choices A to D describe the reverse urea hypothesis, idiogenic osmole hypothesis, rapid infusion of bicarbonate hypothesis and intradialytic hypotension hypothesis respectively. Another mechanism postulated that the dialysate temperature may increase body temperature and worsen intracranial hypotension. The exact mechanisms for this phenomenon have not yet been elucidated.

• 41. The correct answer is B. Resection of pituitary adenomas is associated with a risk of long-term HPA axis dysfunction. A morning serum cortisol level below 15 μg/dL the next day after surgery is associated with a significantly increased risk of requiring long-term glucocorticoid therapy [19].

• 42. The correct answer is E. As a rule of thumb, the average glucose can be roughly estimated by the formula (serum A1c × 29) – 47, assuming the A1c is accurate (i.e. no condition that significantly increases or decreases red cell lifespan). In this case, the answer is (10 × 29) – 47, or 236 mg/dL.

• 43. The correct answer is D. This patient is newly diagnosed with HIV. The decision to initiate antiretroviral (ARV) treatment includes reviewing resistance patterns, as well as determining the patient’s ability to adhere to ARV regimen, as initiating ARV regimen in a non-compliant patient may lead to the emergence of resistant strains. ARV treatment is not emergent, and should be initiated in stable patients; therefore, treatment can be deferred to the outpatient setting post-discharge. Viral load is used to determine treatment success while on ARV therapy, and so is not needed during this hospitalization. ARV treatment can be initiated for patients with CD4⁺ < 500 cells/mm³ [20].

• 44. The correct answer is D. The classic diagnostic features of TTP are thrombocytopenia (with or without purpura), fever, altered mental status (which may range from mild confusion to frank hallucinations), hemolytic anemia (including the presence of schistocytes on the peripheral smear), and fever. It is rare, however, for a patient with TTP to present with all 5 elements of the “pentad”. The INR is usually normal, which may help to differentiate TTP from disseminated intravascular coagulation (DIC).

• 45. The correct answer is E. Andexanet alfa is a recombinant modified factor Xa protein approved by the FDA in May 2018 as an antidote to apixaban and rivaroxaban in patients with life-threatening or uncontrolled bleeding. Use of andexanet alfa is associated with reversed inhibition of factor Xa, correction of clotting times, restoration of hemostasis, and a reduction in acute blood loss [21].

• 46. The correct answer is D. While esophagitis can occasionally lead to GI bleeding, it is most commonly associated chest pain and/or dysphagia. The other options listed are far more common causes of bleeding.

• 47. The correct answer is B. The image below demonstrates an MCA arrow sign, which is the result of blood pooling in ipsilateral Sylvian fissure of a ruptured MCA aneurysm. The spot sign refers to a focus of enhancement within an intracerebral hemorrhage indicating contrast extravasation and continued active bleeding. Westermark sign is a dilated pulmonary artery adjacent to a collapsed vessel in the setting of pulmonary embolism seen on plain x-rays of the chest. A dural tail sign represents thickening of the dura adjacent to a mass, most commonly a meningioma. A hyperdense MCA is seen in the setting of an acute infarct, and represents clot within the vessel [22].

• 48. The correct answer is C. Communication is key in the ICU, especially with multi-disciplinary care teams. The terms drowsy, lethargic, encephalopathic, stuporous, and comatose are usually not precisely used, and can be equivocal. Noting which stimulus (auditory, tactile, repeated vigorous tactile, noxious) led arousal is more useful, in addition to eye tracking and attention span. Aphasic or intubated patients with eye opening apraxia who are localizing to painful stimuli score 7 on the GCS, but are definitely not comatose, as they have cortically mediated responses.

• 49. The correct answer is E. In a recent large prospective trial of MSUs compared to standard EMS models for the treatment of stroke, patients treated with MSUs had slightly better dichotomized modified Rankin scores at discharge. There were no significant differences in mortality or ICH noted. The costs of implementing MSUs are significant, and it remains to be seen whether the benefits are worth the required resources [23].

• 50. The correct answer is B. The ABCD² score estimates the risk of stroke at 90 days for patients presenting with TIA. Patients get 1 point for age ≥60, 1 point for systolic blood pressure ≥140 or diastolic blood pressure ≥90, 1 point for aphasia without limb weakness, 2 points for aphasia with limb weakness, 1 point for diabetes requiring insulin or oral medications, 1 point for duration of 10–59 min, and 2 points for duration ≥60 min. The estimated risk of stroke at 90 days for a score of 0-7 is, respectively, 0%, 2%, 3%, 3%, 8%, 12%, 17%, and 22%. This patient’s ABCD² is 2 points -- 1 point for duration of 30 min and 1 point for aphasia only. This corresponds to a 2-day risk of stroke of 1%, and a 90-day risk of stroke of approximately 3%. It should be noted, however, that a recent systematic review has concluded that the ABCD² score potentially lacks the ability to accurately differentiate high-risk versus low-risk patients [24].

• 51. The correct answer is B. The ARUBA trial evaluated the benefit of preventive eradication of unruptured brain AVMs. This trial compared the risk of death and symptomatic stroke in patients with unruptured brain AVMs who are allocated to medical management with interventional therapy (i.e., neurosurgery, embolization, or stereotactic radiotherapy, alone or in combination) or medical management alone. The trial found that medical management alone is superior to medical management with interventional therapy for the prevention of death and stroke [25].

• 52. The correct answer is D. Carotid artery injury due to blunt head injury has a strong association with petrous bone fractures traversing the carotid canal. A petrous bone fracture requires considerable force, and a high index of suspicion for carotid artery injury is necessary. Distal ischemia can occur by thrombosis or hemodynamic insufficiency caused by luminal narrowing. The described right acute SDH is a result of counter-coup injury, and it does not require urgent surgical intervention. The possibility of spinal fluid leak and facial nerve injury are important considerations, but can be addressed later [26].

• 53. The correct answer is C. While discontinuing feeds and tapering the propofol would indeed address the issue of phenytoin absorption and allow for a better neurologic assessment, the patient is still seizing, and still has a high risk of deterioration from hematoma expansion or increase in perihematomal edema. Increasing the phenytoin will still lead to erratic absorption given the continuous feeds; additionally, it may be the etiology of her fevers. It is likely more judicious to switch from phenytoin to a different agent, such as valproate. Recurrent seizure activity should always prompt a dose of benzodiazepine to prevent recurrence. Adding a midazolam infusion to her current regimen may result in prolonged mechanical ventilation, especially considering her LPDs may simply be markers of her ICH. Clot evacuation can be considered in extreme cases, but not before addressing her ongoing seizure activity.

• 54. The correct answer is E. Single-fiber EMG offers the best sensitivity at approximately 95%. The ice-pack test has limited sensitivity. The tensilon test is 80–90% sensitive, and is most helpful when there is clear ptosis or ophthalmoparesis. The AChR antibody is present in about 85% of those with generalized disease; of the remaining 15%, approximately 40–50% will be MuSK-positive. Of note, almost all patients with both myasthenia and a thymoma are AChR-Ab positive [27].