Diagnostic Tests
Questions
1. Which of the following scenarios would a computed tomography (CT) scan of the head be most indicated?
A. A 32-year-old woman with progressive leg weakness over the past 3 months
B. A 35-year-old woman with a history of multiple sclerosis presenting for a new onset of right leg sensory loss
C. A 70-year-old man with a known brain tumor who presents for routine follow-up
D. An 80-year-old man on heparin drip for pulmonary embolus who had an acute mental status change
E. An 80-year-old woman with progressive memory loss over the past 3 years
View Answer
1. Answer D. (MN-21) Common indications for urgent CT head imaging include head or facial trauma, mental status change, new-onset seizure, or new-onset headache with red flag features. A CT head is unlikely to be indicated for routine surveillance of a known brain lesion in the absence of a clinical change. MRI is the preferred imaging modality for progressive neurological problems, including neurodegenerative or spinal disease.
Multiple sclerosis and related CNS neuroimmune diseases are covered in Chapter 71, tumors in Section XIV, and dementia in Section VII.
2. A 65-year-old man presents to the emergency department for new-onset right-sided weakness and speech difficulty. In evaluating the patient, you are concerned for an acute ischemic stroke. He is sent for urgent computed tomography (CT) imaging including CT angiogram of his head and neck. Review of his medical record shows he has an allergy to shellfish. Which of the following strategies should be taken prior to CT imaging?
A. Defer CT imaging acutely given risk of contrast allergy
B. Premedicate the patient with intravenous (IV) diphenhydramine and steroids prior to contrast exposure
C. Premedicate the patient with IV diphenhydramine alone prior to contrast exposure
D. Premedicate the patient with IV diphenhydramine, steroids, and epinephrine prior to contrast exposure
E. Proceed with immediate CT imaging without premedication
View Answer
2. Answer E. (MN-21) Shellfish allergy is no longer considered a risk factor for contrast allergic reaction. This patient should proceed with CT and CT angiography imaging immediately without premedication. In patients at increased risk for allergic reaction, premedication strategies (Table 3.2.1) involve the use of intravenous diphenhydramine plus a corticosteroid (methylprednisolone, hydrocortisone) or oral prednisone, given in certain dose and time before imaging pending urgency of study. Epinephrine is used only if the patient develops anaphylaxis and should not be used to premedicate patients.
TABLE 3.2.1 Premedication Strategies for Patients With Known Risk Factors to Intravenous Iodinated Contrast Agents | ||||||||
|---|---|---|---|---|---|---|---|---|
| ||||||||
3. The same patient undergoes stat computed tomography (CT) head imaging with CT angiogram of his head and neck and CT perfusion. What would you expect to see on CT perfusion imaging if the patient’s brain injury largely reflected an ischemic penumbra, as opposed to already-infarcted tissue?
A. Elevated mean transit time and cerebral blood flow, reduced cerebral blood volume
B. Elevated mean transit time, cerebral blood flow, and cerebral blood volume
C. Elevated mean transit time, reduced cerebral blood flow, elevated cerebral blood volume
D. Reduced mean transit time, elevated cerebral blood flow and cerebral blood volume
E. Reduced mean transit time, cerebral blood flow, and cerebral blood volume
View Answer
3. Answer C. (MN-21) Ischemic penumbra on CT imaging is best exemplified by elevated mean transit time, reduced cerebral blood flow, and elevated to unchanged cerebral blood volume. Elevated mean transit time with reduced cerebral blood flow and cerebral blood volume is indicative of core infarct and likely irreversibly injured tissue.
Acute ischemic stroke: the first hour is covered in Chapter 16 and further in Chapter 36.
4. A 32-year-old woman presents with internuclear ophthalmoplegia following a period of hemisensory disturbance, which occurred 2 years prior. Multiple sclerosis is suspected. Which neuroimaging sequence or study would be most helpful in securing the diagnosis?
A. MRA head
B. MRI brain fluid-attenuated inversion recovery (FLAIR) sequence
C. MRI brain susceptibility-weighted imaging (SWI)
D. MRI brain T1 sequence
E. Noncontrast CT head
View Answer
4. Answer B. (MN-22) MRI T2 FLAIR sequence, which would be expected to demonstrate multiple periventricular and subcortical white matter hypertensities, likely more than clinically suggested by the history supporting multiple sclerosis (MS). While a contrast T1 MRI sequence would be expected to highlight the most recent event, with a paramedian contrast-enhancing lesion in the pontomesencephalic region, it is not an option, and would only inform the current clinical diagnosis. A noncontrast T1 sequence may demonstrate voids/regions of focally absent white matter, but this is more often seen in more advanced stages of established patients in multiple sclerosis. SWI is useful in patients with suspected hemorrhagic or calcifying lesions but would be unlikely to be abnormal in this patient. Computed tomography is unnecessary in this case unless the patient appears acutely or morbidly ill, which also is unlikely in most cases of MS, or if MRI is not feasible. In this case, the CT would be most capable of ruling out an alternative explanation, with the clinical history being most supportive of MS. Moreover, this would expose a young person to unnecessary ionizing radiation. CTA and MRA are not indicated in suspected MS.
Multiple sclerosis and related CNS neuroimmune diseases are covered in Chapter 71.
5. A 21-year-old man was concussed while playing football, with a brief period of loss of consciousness. He has been playing contact football since age 8 years and has had multiple concussions. Which neuroimaging study is currently being used in the research setting to better evaluate white matter tract injury?
A. MRI brain/diffusion tensor imaging (DTI)
B. MRI brain diffusion-weighted imaging (DWI)
C. MRI brain fluid-attenuated inversion recovery (FLAIR) sequence
D. MRI brain susceptibility-weighted imaging (SWI)
E. Noncontrast CT head
View Answer
5. Answer A. (MN-22) Large case series of sports-related concussion suggest less than 0.1% of sports-related concussion has demonstrable imaging abnormalities on conventional MRI. The definition of concussion is mild TBI without structural imaging abnormalities. DTI and functional MRI are currently being used in the research setting to better understand how concussion and mild TBI affect the white matter tracts.
Concussion and chronic traumatic encephalopathy are covered further in Chapter 46.
6. A 58-year-old man presents with acute right hemiparesis and speech difficulty. Which of the following is the most appropriate neuroimage to be ordered first?
A. Digital subtraction angiography
B. MRI brain + MRA head and neck
C. MRI brain + MRV head
D. Noncontrast CT head
E. Noncontrast CT head + CTA head and neck
View Answer
6. Answer E. (MN-22) A CT head + CTA head and neck should be performed on all patients who present with acute focal neurological weakness concerning for stroke. Moreover, given the presence of cortical signs (aphasia), a CTA should be performed in this patient to rule out large vessel occlusion. While increased availability and speed of MRI has increased its use, CT head remains a fast radiologic option for distinguishing ischemic versus hemorrhagic stroke, which remains the initial decision point in activating acute stroke treatments. Moreover, the acute onset of symptoms makes venous sinus thrombosis less likely in this scenario. Digital subtraction angiography would be a part of treatment, as well as diagnosis, particularly if the patient receives mechanical thrombectomy; however, the patient requires noninvasive imaging first to rule out hemorrhage.
Acute ischemic stroke is covered further in Chapters 16 and 36. Cerebral venous and sinus thrombosis is covered further in Chapter 41.
7. A 23-year-old woman presents with 3 years of medically refractory, focal-onset seizures with auras of fear, followed by impaired consciousness and automatisms. She continues to have daily seizures despite multiple antiseizure medications. Which of the following imaging modalities would most likely locate the lesion responsible for her symptoms?
A. Axial FLAIR
B. Axial TI postcontrast
C. Coronal FLAIR
D. MRA head
E. Sagittal FLAIR
View Answer
7. Answer C. (MN-22) The clinical syndrome supports medial temporal lobe epilepsy, and this patient may be a candidate for a surgical intervention. Given the chronicity of the syndrome, an MRI will spare this young patient ionizing radiation. Coronal MRI sequences, particularly fine cuts through the temporal lobes, are optimal in identifying structural abnormalities and asymmetries in the medial temporal lobe, including mesial temporal sclerosis. MR angiography is not indicated in this patient as it will not show any structural brain pathology.
Temporal lobe epilepsy is covered in Chapter 60, Classification of Seizures and Epilepsy.
8. A 33-year-old morbidly obese woman presents with a progressive headache syndrome and vision loss. She is not hypertensive. Examination is notable for papilledema and visual field loss in the periphery but is otherwise unremarkable. Which of the following imaging modalities is most likely to support her diagnosis?
A. CTA head
B. CT head
C. Digital subtraction angiography
D. MRA head
E. MRI brain and MR venography (MRV) of the head
View Answer
8. Answer E. (MN-22) The most common abnormality in a patient with idiopathic intracranial hypertension (pseudotumor cerebri) is narrow or “slit-like” ventricles, best seen on axial neuroimaging such as FLAIR MRI and T1 MRI. Appropriate concern may be raised for posterior reversible encephalopathy syndrome, also identifiable on FLAIR, but she is not known to have hypertension or take medications associated with this condition. Given the presence of papilledema, an MRV should be performed in conjunction with the MRI to rule out venous sinus thrombosis. Vessel imaging alone is not appropriate as it will not identify potential mass lesions nor findings associated with idiopathic intracranial hypertension (with findings potentially limited to slit-like ventricles, empty sella, and/or flattening of the posterior aspect of the globe).
Intracranial hypertension is covered in Chapter 9 (within Secondary Causes of Headache) and Chapter 111 (Brain Edema and Increased Intracranial Pressure).
9. A 54-year-old man is brought by EMS to the emergency department for an episode of generalized tonic-clonic shaking with loss of awareness. In the emergency department, his fingerstick and drug screen are unremarkable and he denies alcohol use and prior episodes of similar loss of awareness. On exam, he is notes to move his right arm slower than his left. Which of the following is the most appropriate first neuroimaging study?
A. Digital subtraction angiography
B. MRI brain and MRA head and neck
C. MRI brain and MRV head
D. MR spectroscopy
E. Noncontrast CT head
View Answer
9. Answer E. (MN-22) Common indications for emergency CT head include acute focal neurological deficit, head trauma, change in mental status, and new-onset seizure (Table 3.9.1). The patient in this scenario is an adult with new-onset seizure and no prior seizure history. Moreover, he is noted to have some focality on exam with slight right arm weakness. Emergent CT head should be performed to rule out life-threatening conditions such as hemorrhage, herniation, or hydrocephalus. Further advanced imaging (CTA, MRI/MRA/MRV) should be performed as the clinical history evolves.
The approach to new-onset seizures is covered in Chapter 7 and further in Chapter 60.
TABLE 3.9.1 Common Indications for Emergency Computed Tomography Examination | ||||||
|---|---|---|---|---|---|---|
|
10. A 65-year-old man is brought to the clinic by his wife. She reports he has been increasingly forgetful over the last year. She also reports personality changes, in that he has become more easily upset and yells at other people for seemingly trivial events. He denies having any cognitive difficulties and does not understand why his wife brought him to the appointment. His general neurological examination is unremarkable. A brain MRI shows diffuse mild atrophy. Which diagnostic test is likely to help distinguish between Alzheimer disease and frontotemporal dementia as the cause of this patient’s symptoms?
A. FDG-PET scan
B. [18F] Florbetapir (Amyvid) PET scan
C. Perfusion SPECT scan
D. All of the above
View Answer
10. Answer D. (MN-23) The patient demonstrates both memory and behavioral symptoms at a relatively young age, with poor insight. Both Alzheimer disease and behavioral variant frontotemporal dementia are diagnostic considerations. Both FDG-PET (Figure 3.10.1) and perfusion SPECT can help distinguish these two disorders by identifying topographical patterns of neurodegeneration that may not be obvious on MRI. Reduced FDG metabolism or cerebral perfusion in a temporoparietal distribution is more likely in Alzheimer disease, while a frontotemporal distribution is more likely in frontotemporal dementia. The presence of frequent neuritic plaques on an amyloid PET scan (such as [18F] florbetapir, Figure 3.10.2) is suggestive, but not conclusive, of a diagnosis of Alzheimer disease. However, a negative amyloid PET scan is not compatible with a diagnosis of Alzheimer disease and warrants consideration of other causes such as frontotemporal dementia.
Additional coverage on the workup dementia is included in Section VII: Dementia.
 FIGURE 3.10.1 (Image courtesy of Robert Innis and William Charles Kreisl, Molecular Imaging Branch, National Institute of Mental Health.) |
 FIGURE 3.10.2 (Louis ED, Mayer SA, Noble JM, eds. Merritt’s Neurology. 14th ed. Wolters Kluwer; 2022.) |
11. A 55-year-old woman presents to a memory clinic complaining about recent forgetfulness. She is particularly concerned because her mother and maternal grandmother were diagnosed with dementia prior to death. Which of the following is an example of appropriate use of amyloid PET imaging in clinical practice?
A. An amyloid PET scan would not be appropriate in this patient because the chance of incidental amyloid positivity is very high
B. If the patient has cognitive impairment, an amyloid PET scan can distinguish Alzheimer disease from frontotemporal dementia
C. If the patient has impairment on cognitive testing, an amyloid PET scan can determine whether she has early-stage or more advanced Alzheimer disease
D. The patient has normal results on cognitive testing, but because of her strong family history, an amyloid PET scan should be ordered
View Answer
11. Answer B. (MN-23) The patient is under 65 years of age, and therefore younger than the typical age of onset of Alzheimer disease. Frontotemporal dementia and Alzheimer disease occur with approximately equal frequency in this age range. Therefore, an amyloid PET scan would be helpful to distinguish these two disorders if cognitive impairment is present. Amyloid PET imaging is not recommended in individuals with normal cognition and cannot be used to determine severity of Alzheimer disease. Prevalence of incidental amyloid positivity increases with advanced age.
Additional coverage on the workup dementia is included in Section VII: Dementia.
12. In which of the following situations is amyloid PET imaging most appropriate?
A. A 50-year-old executive without memory symptoms wants to know his risk of Alzheimer disease because both parents died from complications of dementia
B. A neurologist is deciding whether to start a cholinesterase inhibitor in a 60-year-old patient with mild dementia who has memory and behavioral symptoms
C. A patient has been showing signs of memory impairment for 5 years and the clinician wants to know whether the underlying Alzheimer disease is in a mild, moderate, or severe stage
D. A patient has features of both Alzheimer disease and dementia with Lewy bodies and the clinician wants a test to distinguish between the two
View Answer
12. Answer B. (MN-23) Amyloid PET scans can show evidence of frequent neuritic plaque deposition when cognitive symptoms are mild (and even prior to symptoms onset). Therefore, an amyloid PET scan should not be used to determine severity of Alzheimer disease. Patients meeting clinical criteria for dementia with Lewy bodies frequently have amyloidosis on PET imaging. Therefore, amyloid PET is unlikely to be useful in distinguishing this disorder from Alzheimer disease, as a positive scan could be seen in either diagnosis. Amyloid PET can distinguish between frontotemporal dementia and Alzheimer disease, as the former is not associated with cerebral amyloidosis, and this distinction can aid the clinician’s decision whether to start cholinesterase inhibitors, which are indicated in Alzheimer disease but not frontotemporal dementia. As no effective preventative therapy for Alzheimer disease exists at present, and the prognostic value of a positive scan in the cognitively normal elderly remains unclear, amyloid PET imaging is not recommended in asymptomatic individuals.
13. Which of the following choices is not an indication for 18F-fluorodeoxyglucose (FDG)-PET imaging?
A. Differentiating high-grade gliomas from other types of brain tumors
B. Distinguishing between Alzheimer disease and frontotemporal dementia
C. Distinguishing between essential tremor and parkinsonism
D. Surgical planning for patients with medication-refractory epilepsy
View Answer
13. Answer C. (MN-23) Ioflupane I123 (DaT scan), not FDG-PET, can help distinguish between essential tremor and parkinsonism but evaluating the integrity of presynaptic dopamine transporters in the striatum (Figure 3.13.1). The other choices represent indications for FDG-PET.
Movement disorders are covered further in Section XII.
 FIGURE 3.13.1 (Reprinted with permission from Louis ED, Mayer SA, Noble JM, eds. Merritt’s Neurology. 14th ed. Wolters Kluwer; 2022.) |
14. Which of the following statements about amyloid PET imaging is most correct?
A. A negative scan is incompatible with Alzheimer disease
B. A positive scan reflects a definitive diagnosis of clinical Alzheimer disease
C. If a patient is worried about inheriting a mutation that causes Alzheimer disease but genetic testing is not available, an amyloid PET scan can be used to determine if the patient is a mutation carrier
D. Screening PET scans are recommended for patients with a positive family history of Alzheimer disease even if cognitive symptoms are not present
View Answer
14. Answer A. (MN-23) Alzheimer disease is pathologically defined by the presence of amyloid plaques and neurofibrillary tangles. Therefore, an absence of radioligand binding on amyloid PET rules out the diagnosis of Alzheimer disease. Positive amyloid scans can be found in a small proportion of cognitively normal elders, and in more than half of patients with dementia with Lewy body disease. Therefore, a positive scan should not be used in isolation to diagnose Alzheimer disease. Amyloid PET is not recommended in individuals without cognitive impairment and should not take the place of genetic testing for autosomal mutations that cause Alzheimer disease.
15. Carotid duplex shows >70% diameter reduction in proximal internal carotid artery lumen with an elevated peak systolic velocity of 290 (normal <125) and end-diastolic velocity of 105 (normal <40). This pattern of findings is most likely consistent with which disease?
A. Carotid occlusion
B. Carotid stenosis
C. Fibromuscular dysplasia
D. Normal variant
E. Sickle cell disease
View Answer
15. Answer B. (MN-24) Elevated peak systolic velocity and end-diastolic velocity with visible diameter reduction in the carotid artery is indicative of carotid stenosis (Table 3.15.1). In cases of complete carotid occlusion, the internal carotid artery peak systolic velocity would be undetectable and there would be no discernible lumen of the internal carotid artery. Fibromuscular dysplasia is characterized by multiple lesions (not by a single calcified plaque) and often appearing as a “string of beads,” which is caused by alternating areas of widening and narrowing along the artery. Elevated flow velocity of the intracranial vasculature through transcranial ultrasonography is indicative of active sickle cell disease and increased stroke risk, not elevated velocities of the extracranial vasculature.
TABLE 3.15.1 Consensus Panel Gray-Scale and Doppler US Criteria for Diagnosis of ICA Stenosis | |||||||||||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| |||||||||||||||||||||||||||||||||||||||||||||||||
16. What is the pooled sensitivity and specificity of carotid ultrasonography for carotid stenosis when compared to carotid angiography?
A. 50% to 60%
B. 60% to 70%
C. 70% to 80%
D. 80% to 90%
E. 90% to 99%
View Answer
16. Answer D. (MN-24) A large meta-analysis of 17 studies comparing carotid ultrasonography to angiography showed that carotid ultrasonography had a pooled sensitivity of 86% and pooled specificity of 87%.
17. Transcranial Doppler ultrasonography (TCD) is most likely to be helpful in which of the following conditions?
A. Adjunct testing to confirm drain death
B. Detection and monitoring of vasospasm in patients with subarachnoid hemorrhage
C. Detection of right-to-left shunts
D. Detection of stenosis or occlusion in a major intracranial artery in patients with stroke
E. Diagnosis of intracranial occlusive carotid artery disease
F. All of the above
View Answer
17. Answer F. (MN-24) TCD is useful for all of the answers. Of note, in contrast to carotid ultrasonography, the yield of TCD to detect extracranial occlusive carotid artery disease is very low and cannot be used to diagnose extracranial carotid disease.
18. Which of the following is the most common complication of diagnostic cerebral angiography?
A. Arterial dissection
B. Contrast-induced nephropathy
C. Groin site hematoma
D. Intracerebral hemorrhage
E. Ischemic stroke
View Answer
18. Answer C. (MN-25) Groin site hematoma was found to be the most common complication of diagnostic cerebral angiogram in a retrospective study of over 19,000 patients, occurring in 4.2%. All other potential complications occur less often. Contrast-induced nephropathy occurs at a rate of 0.5% to 6%. Overall neurological complications occur in approximately 2.6% of people undergoing cerebral angiography and include ischemic stroke and arterial dissection.
19. Which of the following is not a proposed strategy for preventing contrast-induced nephropathy?
A. Avoiding perioperative hypotension
B. Encouraging oral and intravenous hydration
C. Holding blood pressure medications the day of the procedure
D. Limiting the amount of contrast administered
E. All of the above
View Answer
19. Answer E. (MN-25) All answer choices are recommended strategies to prevent contrast-induced nephropathy.
20. Taking into consideration medical and procedural perspectives, which of the following is the best advantage of radial access over femoral access for angiography?
A. A longer time of observation required prior to discharge in outpatients
B. Higher rate of arterial vasospasm
C. Lower rate of access site complications
D. More difficult arterial cannulation
E. Patient preference
View Answer
20. Answer C. (MN-25) Radial access has a lower rate of access site complications overall, but vasospasm occurs more often; it may be treated with a “cocktail” of intra-arterial lidocaine and verapamil. Observation times are shorter for radial access and arterial cannulation is considered easier. Although patients prefer radial access, this is not an advantage of the procedure itself.
21. A patient presents with a 5-mm unruptured wide-neck aneurysm of the middle cerebral artery bifurcation and elects for endovascular treatment. The patient has robust superior and inferior M2 divisions. Which of the following is most likely to be successful?
A. Balloon-assisted coil
B. Coiling alone
C. Flow diversion
D. Intrasaccular disruption with the Woven EndoBridge (WEB) device
E. Stent-assisted coil
F. Choices A, C, D, and E are all correct but B is incorrect
G. Choices A through E are all correct
View Answer
21. Answer F. (MN-25) Coiling alone would be unlikely to be successful in a wide-neck bifurcation aneurysm due to the risk of prolapse of the coil into the parent vessel lumen. Strategies to mitigate this would be using a temporary balloon beneath the aneurysm during coiling, placing a stent and utilizing coils to assist in aneurysm thrombosis, flow diverting stent to cause flow stagnation within the aneurysm wall, or using an intrasaccular device.
22. A 1-year-old boy is seen in the ER for new-onset behavioral issues where he refuses to eat, holds his breath, and becomes unresponsive. He is otherwise developmentally normal, achieving all expected milestones to date. His pediatrician refers him to a child neurologist who orders an outpatient EEG, which is read as normal with synchronous sleep spindles.
What frequency (cycles per second [cps] or Hertz) is his posterior dominant rhythm (PDR)?
A. 4
B. 5
C. 6
D. 7
E. 8
View Answer
22. Answer C. (MN-26) A PDR that is reactive to eye opening becomes visible in most children by 4 months of age. With increasing age, the frequency of the PDR progressively increases, reaching 6 cps in most children at 1 year and 8 cps in most children at 4 years. In adults, PDR ranges from 8 to 13 cps and is known as alpha rhythm. Fast activity of 14 to 30 cps, known as beta activity, is seen in adults during wakefulness. Sleep spindles appear at 2 months but do not become synchronous in most children until the age of 2 years. Normal delta activity persists during wakefulness through childhood, adolescence, and early adulthood but becomes progressively less prominent and more intermittent and restricted to the posterior regions (posterior slow wave of youth).
23. A 22-year-old woman was celebrating her graduation from university with friends over weekend. She had several alcoholic beverages and did not sleep. While getting ready to head to work on Monday, her roommate hears her fall and finds her shaking in all four limbs on the ground. EMS is called and she is transferred to a local hospital for further evaluation and management. On arrival to the ER, she becomes more responsive and is able to answer questions and follow basic commands. She is admitted to the hospital for observation and as part of her evaluation, she undergoes a routine EEG.
What percentage of similar patients who undergo an initial routine EEG obtained after an inaugural seizure exhibit epileptiform discharges?
A. 10% to 20%
B. 30% to 50%
C. 60% to 70%
D. 70% to 90%
E. >90%
View Answer
23. Answer B. (MN-26) After first seizure of life, around 30% to 50% of patients will have epileptiform discharges (EDs), which increases to a maximum of 80% to 90% after the third routine EEG, and subsequent EEGs do not raise this proportion further (Figure 3.23.1). Longer recordings, sleep recordings, and the so-called activation procedures, such as hyperventilation, intermittent photic stimulation, and sleep deprivation, can be performed to increase the sensitivity of the EEG. Conversely, EDs are seen in 1% to 2% of EEGs of individuals without a history of epilepsy. This proportion is higher in children and in siblings of patients with epilepsy.
 FIGURE 3.23.1 (Reprinted with permission from Louis ED, Mayer SA, Noble JM, eds. Merritt’s Neurology. 14th ed. Wolters Kluwer; 2022.) |
24. A 61-year-old man with hypertension and diabetes who works as an electrician has developed progressive neurologic deterioration over the last 3 months to the point that he can no longer perform his job and manage his personal finances. He was seen by his PMD who diagnosed him with depression, but referred him to a neurologist for further evaluation. He underwent a routine EEG, which was notable for generalized periodic discharges. His brain MRI reveals cortical diffusion abnormalities.
What is his most likely diagnosis?
A. Creutzfeldt-Jakob disease
B. Huntington disease
C. Lithium toxicity
D. NMDA receptor antibody-mediated encephalitis
E. Whipple disease
View Answer
24. Answer A. (MN-26) In Creutzfeldt-Jakob disease (Chapter 55), severe disruption of the background and periodic discharges (LPDs or more commonly GPDs) occur, usually within 3 months after the onset. Huntington disease is associated with a progressive attenuation of cerebral activity. At least 50% of patients with anti–N-methyl-D-aspartate (NMDA) receptor encephalitis show a typical pattern of rhythmic delta activity overridden by beta activity, which has been termed extreme delta brush due to its resemblance to normal delta brushes of neonates.
25. A 79-year-old woman with mild cognitive impairment, HTN, and HL developed fever, chills, and confusion. In the ED, she is hypotensive to the 80s/40s and unresponsive to intravenous fluids, thus requiring pressors and admission to the ICU. Despite starting antibiotics, she becomes progressively stuporous requiring intubation. Her initial workup is notable for urosepsis. Continuous EEG monitoring is ordered to evaluate for subclinical seizures.
What percentage of critically ill patients who are monitoring with continuous EEG will have seizures?
A. 5% to 10%
B. 15% to 20%
C. 25% to 30%
D. 35% to 50%
E. >50%
View Answer
25. Answer B. (MN-26) Based on prior observational cohort studies, between 15% and 20% of critically ill patients develop seizures during their acute illness. Half of them will develop status epilepticus. Risk factors include acute brain injury, a chronic seizure disorder, younger age, sepsis, and severe alteration of consciousness (ie, stupor and coma). Up to 90% of these seizures are nonconvulsive and will be missed if EEG monitoring is not performed. There is mounting evidence that nonconvulsive seizures have detrimental metabolic and hemodynamic effect and contribute to secondary brain injury and poorer outcome. A monitoring period of 24 hours is required to detect 90% of these seizures. A longer period is required in comatose patients and in patients with LPDs.
26. A 23-year-old woman was assessed for progressive gait disturbance and urinary retention. On examination, her neurologist found slightly decreased visual acuity and papillary atrophy of her right eye. Her left eye was normal. Her MRI of the spinal cord showed acute T8-T9 partial transverse myelitis and her brain MRI showed several nonenhancing white matter lesions, including in the corpus callosum and surrounding the lateral ventricles, and enhancement of right optic nerve. She was referred for visual evoked potentials (VEPs). Which of these VEPs findings are the most likely?
A. Absent P100 with stimulation of the right eye and normal P100 with stimulation of the left eye
B. Decreased P100 amplitude with stimulation of the right eye and normal P100 with stimulation of the left eye
C. Increased P100 latency with stimulation of both eyes
D. Increased P100 latency with stimulation of the right eye and normal P100 with stimulation of the left eye
E. Normal latency and amplitude of P100 with stimulation of both eyes
View Answer
26. Answer D. (MN-26) Abnormal VEPs are found in 70% of patients with MS, even in the absence of a history of optic neuritis. In the acute phase of optic neuritis, the occipital P100 may be absent or have attenuated amplitude with stimulation of the affected eye, but in the chronic phase (in this case suggested by papillary atrophy), the most common finding is increased P100 latency (Figure 3.26.1). VEPs abnormalities are not specific for MS and other conditions affecting the optic nerve may also alter the P100 latency and amplitude. An abnormal P100 after stimulation of both eyes implies either a singular retrochiasmal lesion or bilateral prechiasmal lesions.
 FIGURE 3.26.1 (Courtesy of Nicolas Mavroudakis, MD, PhD.) |
27. A 65-year-old man was admitted to the cardiac ICU with postanoxic coma after cardiac arrest from acute myocardial infarction. He was assessed by a neurologist 3 days after the arrest and found to be deeply comatose with a GCS score of 3 and lack of pupillary and corneal responses. Somatosensory evoked potentials were requested. Which of the following findings would be most likely associated with a low chance of recovery of consciousness?
A. Absence of N9, P14, N13, and N20 after stimulation of both median nerves
B. Increased N20 latency with stimulation of both median nerves
C. Presence of N9, P14, N13, and N20 after stimulation of both median nerves
D. Presence of N9, P14, N13, and N20 after stimulation of the right median nerve, and presence of N9, P14, and N13 but absence of N20 after stimulation of the left median nerve
E. Presence of N9, P14, and N13 but absence of N20 after stimulation of both median nerves
View Answer
27. Answer E. (MN-26) Bilateral absence of cortical N20 responses in patients who remain comatose after cardiac arrest is almost invariably associated with lack of neurological recovery (Figure 3.27.1). Prolonged N20 latency or asymmetrical responses are equivocal findings. Absence of all potentials, including Erb N9 potential, should raise suspicion about the technical quality of the recording and be interpreted with caution. When present, N20 represents the negative physiological peak over the primary somatosensory (parietal) cortex, which predictably occurs at 20ms after median nerve stimulation.
 FIGURE 3.27.1 CHN, channels; Parc, parietal contralateral; Pari, parietal pisilateral. (Courtesy of Nicolas Mavroudakis, MD, PhD.) |
28. Which finding is most supportive of a severe L5 radiculopathy?
A. Complex repetitive discharges in the tibialis anterior muscle
B. Delayed fibular nerve F-wave minimal latency
C. Fibrillation potentials in the tibialis posterior muscle
D. Low-amplitude compound muscle action potential in the extensor digitorum brevis (EDB) muscle
E. Normal sural sensory nerve action potential
F. All of the above
View Answer
28. Answer F. (MN-27) Compressive radiculopathy typically affects the nerve root proximal to the dorsal root ganglia neuron. Regardless of the severity, the distal sensory axon remains intact and sensory nerve action potentials remain normal. Motor fibers and muscle denervation may occur depending on the severity and compression timing.
29. Which finding is most expected during testing with abnormally low limb temperature?
A. Enhanced decremental response on repetitive nerve stimulation
B. Increased motor conduction velocity
C. Reduced resting spontaneous activity
D. Reduced sensory nerve action potential amplitude
E. Shorter F-wave minimal latency
View Answer
29. Answer C. (MN-27) Temperature affects most electrophysiological measures. Decremental responses are blunted in cold muscles and may demonstrate falsely negative results. Sensory nerve action potential amplitude is typically increased in reduced nerve temperature. Sensory and motor conduction velocity is reduced and F-wave minimal latency is increased in cold nerves. Fibrillations and positive sharp waveforms of abnormal spontaneous activity are reduced in cold muscles.
30. Which activity is generated by excess peripheral nerve excitability?
A. Early recruitment
B. Fibrillation potentials
C. Myokymic discharges
D. Myotonic discharges
E. Polyphasic motor unit potentials
View Answer
30. Answer C. (MN-27) Nerve hyperexcitability may be a benign process or result from various autoimmune or hereditary conditions. The primary motor nerve hyperexcitability forms are fasciculations, myokymic discharges, and neuromyotonic discharges. Myotonic discharges are muscle fiber generated. Fibrillation potentials occur from denervated single muscle fibers. Polyphasic motor unit potentials can occur in limited numbers in normal muscle and excessive numbers in both neurogenic and myopathic conditions. Early recruitment is a hallmark of myopathic processes.
31. Which finding is most specific for a myopathic process?
A. Abundant fibrillation potentials
B. Full recruitment in a weak muscle
C. High-amplitude motor unit potentials
D. Increased recruitment ratio
E. Polyphasic motor unit potentials
View Answer
31. Answer B. (MN-27) Myopathic features include short duration, low-amplitude motor unit potentials, early recruitment, full recruitment in weak muscles or reduced effort, and reduced envelope amplitude (Figure 3.31.1). Polyphasic motor unit potentials occur in limited numbers in normal muscle and excessive numbers in both neurogenic and myopathic conditions. High-amplitude motor unit potentials typically occur in neurogenic conditions but can occur in chronic myopathic conditions, especially longstanding myositis. Fibrillation potentials occur in any situation that muscle fibers are separated from nerve supply, including myositis, muscle injury, and muscular dystrophies. Increased recruitment ratio is typical of neurogenic processes; myopathic conditions typically show reduced or normal recruitment ratio (Figure 3.31.2).
 FIGURE 3.31.1 (Reprinted with permission from Louis ED, Mayer SA, Noble JM, eds. Merritt’s Neurology. 14th ed. Wolters Kluwer; 2022.) |
 FIGURE 3.31.2 (Reprinted with permission from Louis ED, Mayer SA, Noble JM, eds. Merritt’s Neurology. 14th ed. Wolters Kluwer; 2022.) |
32. An example of spontaneous activity that occurs in normal muscle is?
A. Endplate spikes
B. Fibrillation potentials
C. Myokymic discharges
D. Myotonic discharges
E. Neuromyotonic discharges
View Answer
32. Answer A. (MN-27) All choices are examples of abnormal rest activity except for endplate spikes. Recording near the endplate zone shows normal rest activity that may include endplate spikes and endplate noise. Often the site is more painful for the patient than other muscle locations.
33. Which characteristic best describes single-fiber EMG (SFEMG)?
A. Abnormal results are seen in multiple conditions
B. High specificity for neuromuscular junction disorders
C. Low filter is set to very low frequency
D. Results are not affected by medication effects
E. Simple procedure that requires no special equipment
View Answer
33. Answer A. (MN-27) Single-fiber EMG (SFEMG) is a specialized procedure to assess for muscle depolarization variability (jitter). The technique is highly sensitive but not highly specific for myasthenia gravis. Other causes of denervation, neuropathy, motor neuron disease, chemodenervation, or myopathy can affect results. In order to optimize recordings, the low filter is set to a higher value than other measures, typically 500 to 1000 Hz. Medications such as anticholinergic agents or chemodenervation affect results. The technique requires a specialized electrode or a pediatric concentric needle and special software that permits data capture and analysis.
34. Which autonomic test is most reproducible and reliable for parasympathetic function assessment?
A. Heart rate variability to deep breathing
B. Serum catecholamine levels
Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
