A 64-year-old woman with a known history of myasthenia gravis comes to the emergency department with 2 days of fever and worsening headaches and neck pain. She was admitted to another hospital 12 days ago for myasthenic crisis precipitated by urinary tract infection. She was treated with ceftriaxone and intravenous immunoglobulin and discharged home 5 days ago. Her other medical problems include hypertension and type 2 diabetes mellitus. Her medications include metformin, glyburide, hydrochlorothiazide, lisinopril, and mycophenolate. The patient's temperature is 38.3 C (101 F), blood pressure is 110/70 mm Hg, pulse is 92/min, and respirations are 16/min. She is awake and oriented. Moderate neck pain and stiffness are present. She moves all extremities to command and has symmetrical deep-tendon reflexes. The remainder of the examination shows no abnormalities. Laboratory results are as follows: Cerebrospinal fluid Gram stain and culture show no organisms. Cerebrospinal fluid cryptococcal antigen is negative. Computed tomography scan of the head without contrast is normal. Which of the following is the most likely cause of this patient's symptoms?

Question

A 64-year-old woman with a known history of myasthenia gravis comes to the emergency department with 2 days of fever and worsening headaches and neck pain.  She was admitted to another hospital 12 days ago for myasthenic crisis precipitated by urinary tract infection.  She was treated with ceftriaxone and intravenous immunoglobulin and discharged home 5 days ago.  Her other medical problems include hypertension and type 2 diabetes mellitus.  Her medications include metformin, glyburide, hydrochlorothiazide, lisinopril, and mycophenolate.  The patient's temperature is 38.3 C (101 F), blood pressure is 110/70 mm Hg, pulse is 92/min, and respirations are 16/min.  She is awake and oriented.  Moderate neck pain and stiffness are present.  She moves all extremities to command and has symmetrical deep-tendon reflexes.  The remainder of the examination shows no abnormalities.  Laboratory results are as follows:  Cerebrospinal fluid Gram stain and culture show no organisms.  Cerebrospinal fluid cryptococcal antigen is negative.  Computed tomography scan of the head without contrast is normal.  Which of the following is the most likely cause of this patient's symptoms?

Quizplus · Accepted Answer

Explanation: 11ec2b69_c178_4d69_8f63_e3799c4b2b10_MD0005_00 This patient's clinical manifestations (fever, headache, neck stiffness) and cerebrospinal fluid (CSF) findings (high opening pressure, neutrophilic leukocytosis, high protein, low glucose) are concerning for bacterial meningitis. Even though the sensitivity of CSF Gram stain varies from 60%-90%, the yield of both Gram stain and culture may be reduced by prior antibiotic therapy. Antibiotic pretreatment also can cause higher CSF glucose and lower protein levels in bacterial meningitis. Patients with high suspicion of bacterial meningitis, even with negative Gram stain and culture, should receive a full course of antibiotic therapy. (Choice A) CSF findings in aseptic viral meningitis include cell count <500/µL, >50% lymphocytes, protein concentration <80-100 mg/dL, normal glucose concentration, and negative Gram stain. (Choice C) Cryptococcal meningitis has subacute onset of symptoms, CSF cell count of 20-200/µL, and mononuclear cells predominance. This patient has a negative CSF cryptococcal antigen test, which has a sensitivity of 93%-100%. (Choice D) Abnormalities in brain function, including altered mental status, hemiparesis, seizures, and aphasia, are common in herpes simplex encephalitis. CSF analysis shows lymphocytic pleocytosis, increased number of erythrocytes, and elevated protein. Temporal lobe abnormalities seen on brain imaging are considered strong evidence for herpes simplex encephalitis. (Choice E) Computed tomography scan is >92%-95% sensitive in diagnosing subarachnoid hemorrhage. If the suspicion is still high despite the negative scan, lumbar puncture is indicated to definitively rule out subarachnoid hemorrhage. CSF has a higher opening pressure and erythrocyte count, but CSF protein and glucose are normal. Xanthochromia confirms the diagnosis. Educational objective: Patients who received antibiotics prior to obtaining cerebrospinal fluid levels may have negative Gram stain and culture and altered cerebrospinal fluid glucose and protein. High suspicion of bacterial meningitis, even with negative Gram stain and culture, warrants a full course of antibiotic therapy. References: Effect of antibiotic pretreatment on cerebrospinal fluid profiles of children with bacterial meningitis. (http://www.ncbi.nlm.nih.gov/pubmed/18829794)

A 64-Year-Old Woman with a Known History of Myasthenia Gravis