Infections Flashcards

Question

145. The medication most appropriate in patients with CNS involvementby B. burgdorferi is a. Streptomycin b. Ceftriaxone c. Gentamicin d. Isoniazid e. Rifampin

Answer 1

145. The answer is b. (Victor, pp 768–770.) If there is meningeal involvement,high-dose penicillin or ceftriaxone must be given intravenously for 10 to 14 days. Tetracycline qid for 30 days should be used for patients who are allergic to the intravenous treatments.

Answer 2

146. The answer is a. (Victor, pp 752–756.) There are many bases forabscess formation in the brain, but the most frequent causes are blood-borneinfections from sources in the lung, heart, sinuses, and ears. Extension ofinfection from a chronic otitis or mastoiditis was much more common before the introduction of antibiotics. Facial or dental infections may spread to the brain through valveless veins draining about the muscles of mastication andcommunicating with the venous drainage of the brain.

Answer 3

147. The answer is d. (Victor, pp 752–756.) Brain abscesses usually startfrom a microscopic focus of infection at the junction of gray matter and white matter. As the infection develops, a cerebritis appears, and subsequentlythis focus of infection becomes necrotic and liquefies. Around the enlarging abscess there is usually a large area of edema.

Answer 4

148. The answer is a. (Victor, pp 752–756.) Both aerobic and anaerobicstreptococcal bacteria occur in more than half of all brain abscesses. Staphylococcus aureus most often occurs in patients who have had penetratinghead wounds or have undergone neurosurgical procedures. Entericbacteria (e.g., Escherichia coli, Proteus, and Pseudomonas) account for twiceas many abscesses as S. aureus.

Answer 5

149. The answer is b. ( Bradley, pp 1410, 1415.) Fungal abscesses developwith unusual frequency in patients with AIDS, but T. gondii, an obligate intracellularparasite, is considerably more common than fungi as the cause of abscess formation. The fungi that do produce abscesses in persons with AIDSare most often Cryptococcus, Candida, Mucor, and Aspergillus. Mycobacteriaand atypical mycobacteria are also common causes of abscess formation insome populations.

Answer 6

150. The answer is c. (Victor, p 754.) Three-fourths of patients with brainabscess have headache. This usually develops within a few weeks of theappearance of the abscess. Only one-third of patients present with seizuresor focal neurologic deficits. Only one-fourth exhibit papilledema. Brain abscesses may produce remarkably few changes in the CSF until the abscess penetrates into the subarachnoid or intraventricular space. Abscesses that have not yet communicated with the CSF will usually produce only a moderate elevation in the CSF protein content. If the abscess is unsuspected and untreated, it will usually extend to the ventricles. With perforation into the ventricle, the abscess usually proves fatal. The treatment of choice for brain abscess is surgical resection.

Answer 7

151. The answer is d. (Rowland, pp 127–128.) Patients with brainabscesses may exhibit focal signs, seizures, delirium, or less specific neurologic findings. These patients often have fever, but the CSF may not reflectthe infectious basis of the fever until the abscess ruptures into the ventriclesor subarachnoid space. Although Aspergillus is the most common cause offungal abscesses, it is a relatively uncommon cause of fungal meningitis ormeningoencephalitis. Nocardia is not classified as a fungus despite its resemblance to a fungus.

Answer 8

152. The answer is d. (Bradley, pp 1334–1336.) General paresis is a slowlyevolving process that may require years to produce substantial disability. The early symptoms are a subtle dementia, characterized by memory loss and impaired reasoning, with later development of dysarthria, myoclonus, tremor, seizures, and upper motor neuron signs, leading to a bedridden state. Both the meninges and the parenchyma of the brain are involved bythis chronic infection. The meninges are thickened and opaque, and a granularependymitis characteristically develops. Degenerative changes occurthroughout the cerebral parenchyma. Penicillin is the treatment of choicefor this disease. The damage done to the brain is not mediated by autoimmuneor adverse drug reaction mechanisms. This infection produces widespreadinjury to the brain, rather than the restricted brainstem damage thattypically occurs with infections that attack structures arising from the embryonic rhombencephalon. With a rhombencephalitis, the pons and medulla oblongata are the principal targets of disease.

Answer 9

153. The answer is b. (Bradley, pp 1334–1336.) A gumma is a largely orentirely avascular granuloma. It rarely develops intracranially, but when itdoes, it may grow to several centimeters across. The lesion starts as aninflammatory process but becomes fibrosed as it evolves. The term gummahas traditionally been reserved for granuloma-like lesions caused by spirochetal infection.

Answer 10

154. The answer is e. (Victor, p 796.) Mumps, measles, and varicella zoster infection appear to be acquired primarily by way of the respiratory tract. The poliovirus is an enterovirus, which means it enters primarily through the gastrointestinal tract. Rabies is transmitted by animal bites and reaches the CNS by migration in neuronal processes, presumably as it is swept along by retrograde axoplasmic flow. This is believed to be an unusual method of viral spread to the CNS. Most viruses that do produce CNS disease are carried to the CNS in the bloodstream rather than along neuronal processes with infected axoplasm.

Answer 11

155. The answer is e. (Bradley, pp 1362–1363.) Rabies is usually spreadthrough the saliva of an infected animal. Introduction of saliva into a bitewound allows the virus to inoculate muscles or subcutaneous tissues. Afterintroduction of the virus, the incubation period until fulminant infection appears extends from a few days to over 1 year, but usually ranges from 1 to 2 months. Bites of the head and face carry the greatest risk of causing fatal disease. Early after exposure, the patient will often complain of pain or paresthesias at the site of the animal bite. Animals transmitting the virus include dogs, bats, skunks, foxes, and raccoons. Dehydration as a complication of rabies is no longer likely because intravenous fluids can be given to completely replace what the hydrophobic patient cannot consume bymouth. Other complications of rabies include a paralytic form of the diseasethat progresses to quadriplegia (dumb rabies) in 20% of patients. With the classic form of the disease, the patient will also exhibit intermittent hyperactivity.

Answer 12

156. The answer is a. ( Bradley, pp 1362–1363.) No antiviral therapy affectsthe course of rabies. Immunization against rabies after exposure has occurredis essential, though even this may not substantially improve the outlook ofthis almost invariably fatal disease. The infected patient must receive intensivecare with precautions taken to prevent spread of the virus through contactwith body fluids, such as saliva. Transmission of the virus through casualcontact does not seem to occur, but it may be transmitted through cornealtransplantation when the donor has been infected. Zidovudine (azidothymidine,AZT) is an antiretroviral drug useful in slowing the progression of HIV-1 infection. Ganciclovir has found increasing use in the management of cytomegalovirus (CMV) infection, especially when CMV involves the eye in a chorioretinitis. Amantadine was developed as an anti-influenzal agent, but it is used primarily to reduce the symptoms of Parkinson’s disease. The reason for its antiparkinsonian action is unknown.

Answer 13

157. The answer is e. ( Bradley, pp 1424–1425.) This patient has a subacuteto chronic progressive disease characterized by a combination of dementia, tremor, ataxia, and myoclonus. The EEG and MRI findings are typical of aspongiform encephalopathy. Multi-infarct dementia and subarachnoid hemorrhagewould be expected to produce at least one very discrete event, and the imaging studies would be expected to show evidence of infarcts or other vascular abnormalities. Friedreich’s disease may produce some dementia, but it is not a prominent part of the clinical deterioration. This patient is also much older than would be consistent with Friedreich’s disease.

Answer 14

158. The answer is a. (Bradley, p 1425.) The spinal fluid examination in a patient with spongiform encephalopathy, or Creutzfeldt-Jakob disease, is typically normal. On occasion, the protein level may be mildly elevated, and, in up to 20% of cases, there may be an increase in immunoglobulin G–to–total protein ratio, occasionally with oligoclonal bands. Studies have indicated that a protein highly sensitive and specific for prion disease, a 14-3-3 proteinase inhibitor protein released from neurons, may be found in patients with this illness.

Answer 15

159. The answer is e. (Bradley, p 1427.) The most likely cause of spongiformencephalopathy in this middle-aged woman is Creutzfeldt-Jakob disease.This is classified as a prion disease and can be transmitted via infected nervous system tissue, including dura mater grafts, and occasionally via growth hormone preparations acquired from cadaver pituitary glands. A similar disease (kuru) occurs in Fore Islanders of New Guinea and is presumed to spread through the ritual handling or eating of human brain tissue. As of 1999, 113 cases due to growth hormone preparations had been reported, with incubation periods ranging from 5 to 30 years.

Answer 16

160. The answer is c. ( Bradley, pp 1413–1414.) This patient probably hadAIDS with PML as a complication of that disease. The inclusion bodies in theoligodendrocyte nuclei are JC virus, a papillomavirus. Primary infection withJC virus is universal and asymptomatic. Immunosuppression leads to reactivationof the virus. Diagnosis is typically made by MRI, which shows multiple focal well-defined white matter lesions that do not enhance or have mass effect. Cerebrospinal fluid PCR for JC virus is also available, obviating the need for brain biopsy in most cases. Treatment with cytarabine arabinoside has not been shown to be effective in clinical trials. Less than 10% of patients may experience spontaneous remission. PML may also develop with lymphomas, leukemias, or sarcoid, but the incidence of this disease in the U.S. population has expanded greatly since the dissemination of HIV in the population.

Answer 17

161. The answer is e. (Victor, pp 1380–1387.) The loss of strength associated with Guillain-Barré syndrome usually reaches a nadir within 2 weeks ofthe onset of symptoms. Sensation is usually preserved except for paresthesiasin the feet or lower legs. Weakness is usually symmetric and often followsan ascending pattern of involvement. Tendon reflexes in the weak limbs are usually hypoactive or absent. Bladder and bowel control remain intact, but the patient usually exhibits some autonomic dysfunction, such as tachycardia and excessive sweating, which is rarely life-threatening. Eye muscles may be affected with Guillain-Barré syndrome, particularly in the condition called the Miller-Fisher variant. Before artificial ventilators were available, these patients often died from respiratory complications. The CSF with this disease typically reveals an elevated protein content with a relatively normal or only slightly abnormal white cell count and an invariably normal glucose content. This helps to distinguish it from poliomyelitis, a cause of paralysis that produces an alteration in both the protein and WBC content of the CSF consistent with a viral meningitis.

Answer 18

162. The answer is f. (Victor, pp 766–767.) Tabes dorsalis is caused by Treponema pallidum, the agent responsible for all types of neurosyphilis, but it is a disease entity distinct from general paresis, the form of neurosyphilis in which personality changes and dementia do occur. With tabes dorsalis,the patient develops a leptomeningitis. The posterior columns of the spinal cord and the dorsal root ganglia are hit especially hard by degenerativechanges associated with this form of neurosyphilis. Tabes dorsalis is a formof neurosyphilis that usually becomes symptomatic decades after the initialtreponemal infection. The gait ataxia and positive Romberg sign in this patient are manifestations of absent position sense. Bladder and bowel control may be profoundly disturbed, presumably on the basis of dorsal spinal root disease. The bladder is usually hypotonic (flaccid), and megacolon may develop. Patients with tabes dorsalis routinely exhibit abnormal(Argyll Robertson) pupils and optic atrophy. The glucose and glycohemoglobin should be checked to eliminate the more common cause of impaired position sense in the United States, diabetes mellitus. That this patient is from a part of the world that has relatively poor health care is relevant because this form of syphilis is rarely seen in persons who have spent most of their lives in countries with easy access to antibiotics.

Answer 19

163. The answer is b. (Victor, pp 810–811.) Subacute sclerosing panencephalitisusually develops in children and is rarely seen after the age of 18. Most affected children have had a bout of measles (rubeola) that occurred before they were 2 years old. SSPE may not appear for as long as 6 to 8 years after the episode of measles. Death usually occurs within 1 to 3 years after the onset of symptoms. SSPE produces a CSF pattern similar to that seen with multiple sclerosis, whose features include an increase in the gamma globulin fraction and the presence of oligoclonal bands. The measles virus appears to be directly responsible for this demyelinating disease, and the oligoclonalbands that appear in the CSF include a substantial proportion of measlesspecificantibody. Eosinophilic inclusions are typically present in the cytoplasmand nuclei of neurons and glial cells.

Answer 20

164. The answer is h. (Bradley, p 1347.) Cat-scratch disease produces aregional adenitis, frequently involving epitrochlear nodes due to scratcheson the patient’s arm from an infected animal. The causative agent is B.henselae (rarely Afipia felis). In immunocompetent hosts, it may produce aself-limited aseptic meningitis. In HIV-infected individuals, it may producea more virulent encephalitis associated with status epilepticus. Typically,these patients have disseminated disease, including distinctive skin lesionscomposed of neovascular proliferation (bacillary angiomatosis). On rareoccasions, immunocompetent patients may have encephalitis as well. AnMRI may show a characteristic increased signal intensity in the pulvinar,suggesting a tropism of the organism or immune response to this particularstructure in the posterior thalamus.

Answer 21

165. The answer is g. (Bradley, pp 1394–1396.) Cysticercosis is producedby the larval form (cysticercus) of the pork tapeworm, Taenia solium. This is the most common neurological infection throughout the world, occurring most commonly in South America, Southeast Asia, and Africa. It is transmitted by fecal-oral contact; tapeworm eggs hatch in the human GI tract, invade the bowel mucosa, and migrate throughout the body, particularly into CNS, muscle, eye, and subcutaneous tissues. Cysticercal infection of muscles produces a nonspecific myositis. Brain involvement may lead to seizures. The lesions in the brain may calcify and often appear as multiple small cysts spread throughout the cerebrum.

Infections Flashcards

(45 cards)