A 7-year-old girl is brought to the emergency department by her parents in August due to fever and lethargy. The patient has had intermittent fevers and a headache that has persisted for the last few days. Her headache has worsened in the last 24 hours, and she has vomited twice. She has been sleeping more than usual, and her parents brought her to the hospital after she was difficult to rouse from a nap. She has had no seizures, sore throat, or abdominal pain. The family recently returned from a week-long camping trip. Her 3-year-old sister is recovering from a recent upper respiratory tract infection. The patient has no chronic medical conditions, and her immunizations are up to date. Temperature is 38.9 C (102 F), blood pressure is 100/60 mm Hg, pulse is 118/min, and respirations are 24/min. She is currently disoriented and unable to recognize her parents. There is nuchal rigidity but cranial nerves are intact. Mucous membranes are moist and the oropharynx is clear. Cardiopulmonary examination is normal. The lower extremities have 3+ patellar reflexes and positive Babinski sign. Several excoriated insect bites are seen on the extremities. Which of the following is the most likely etiology of this patient's condition?

Question

A 7-year-old girl is brought to the emergency department by her parents in August due to fever and lethargy.  The patient has had intermittent fevers and a headache that has persisted for the last few days.  Her headache has worsened in the last 24 hours, and she has vomited twice.  She has been sleeping more than usual, and her parents brought her to the hospital after she was difficult to rouse from a nap.  She has had no seizures, sore throat, or abdominal pain.  The family recently returned from a week-long camping trip.  Her 3-year-old sister is recovering from a recent upper respiratory tract infection.  The patient has no chronic medical conditions, and her immunizations are up to date.  Temperature is 38.9 C (102 F), blood pressure is 100/60 mm Hg, pulse is 118/min, and respirations are 24/min.  She is currently disoriented and unable to recognize her parents.  There is nuchal rigidity but cranial nerves are intact.  Mucous membranes are moist and the oropharynx is clear.  Cardiopulmonary examination is normal.  The lower extremities have 3+ patellar reflexes and positive Babinski sign.  Several excoriated insect bites are seen on the extremities.  Which of the following is the most likely etiology of this patient's condition?

Quizplus · Accepted Answer

Explanation: 11ec2b69_c17f_5254_8f63_a5f9f4f78462_MD0005_00 Viral infections of the central nervous system (CNS) can cause inflammation of the meninges (ie, meningitis), the brain parenchyma (ie, encephalitis), or both (ie, meningoencephalitis). This patient has nuchal rigidity (meningeal sign) as well as altered mental status (encephalopathy), consistent with viral meningoencephalitis. In children, enteroviruses (eg, Coxsackievirus, Echovirus) are the most common cause of viral CNS infections, followed by herpesviruses and arboviruses. West Nile virus is an arbovirus transmitted by mosquitoes, causing infection in the summer and early fall, as seen in this patient. Patients with neuroinvasive disease typically present with manifestations of meningitis, including fever, headache, photophobia, nuchal rigidity, and/or signs of encephalitis, such as confusion and focal neurologic findings (eg, hyperreflexia). A maculopapular rash is common with West Nile virus but not always present, and patients may have excoriated mosquito bites, as seen on this patient. Detection of West Nile IgM antibody in the cerebrospinal fluid is diagnostic, and treatment is generally supportive. (Choice A) Borrelia burgdorferi is a spirochete responsible for Lyme disease. Typical CNS manifestations include meningitis, cranial nerve palsies, and peripheral neuropathies; encephalitis is rare. (Choice B) Cytomegalovirus infection of the CNS occurs almost exclusively in HIV-infected patients with AIDS or post-transplant patients. (Choice C) Herpes simplex virus is a common viral CNS infection and presents suddenly with fever, headache, seizures, and focal neurologic deficits. However, this patient's insect bites make West Nile infection more likely. (Choice D) Measles encephalitis typically occurs following the initial illness with fever, cough, coryza, conjunctivitis, and diffuse maculopapular rash. Measles is unlikely in this patient who is fully immunized. Educational objective: West Nile virus can cause meningoencephalitis, inflammation of the meninges and brain parenchyma, following a bite from an infected mosquito. Infection typically occurs in the summer and presents with fever, headache, vomiting, nuchal rigidity, and altered mental status. References: Emerging vector-borne diseases. (http://www.ncbi.nlm.nih.gov/pubmed/27929218) Fever of unknown origin in a patient with confirmed West Nile virus meningoencephalitis. (http://www.ncbi.nlm.nih.gov/pubmed/25580318) Differential virulence and pathogenesis of West Nile viruses. (http://www.ncbi.nlm.nih.gov/pubmed/24284878)

A 7-Year-Old Girl Is Brought to the Emergency Department by Her