Updated: 4/15/2019

Encephalitis

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Snapshot
  • A 46-year-old male is brought to the emergency department by his wife due to a seizure event. She reports that prior to the event, he complained of headache, fever, and nausea. She also reports her husband appeared confused. On exam, the patient cannot clearly answer questions. A CT of the head shows no evidence of a hemorrhage, or a space-occupying lesion. MRI of the brain is shown. A lumbar puncture is performed, and cerebral spinal fluid analysis shows a normal opening pressure, a lymphocytic pleocytosis, normal glucose, and elevated protein. PCR is positive for herpes simplex virus-1.
Introduction
  • Brain parenchymal infection
    • abnormalities in brain functioning are expected
      • e.g., altered mental status, changes in personality, problems with speech and movement
      • this distinguishes encephalitis from meningitis
  • Typically caused by infection
    • viral (most cases)
      • herpes simplex virus (HSV)
        • most common cause
      • varicella virus (VZV)
      • epstein-barr virus (EBV)
      • measles, mumps, rubella
      • HIV
      • Japanese encephalitis virus
      • St. Louis encephalitis virus
      • West nile virus
    • bacterial
      • toxoplasmosis
    • noninfectious
      • acute disseminated encephalitis
  • There can be both an infection of the brain parenchyma and meninges
    • leading to a meningoencephalitis
Presentation
  • Symptoms  
    • seizures
    • fever
    • headache
    • nausea
    • vomiting
  • Physical exam
    • altered mental status
    • personality changes
    • focal neurological deficits
      • cranial nerve palsies
      • hemiparesis.
    • meningsmus
      • only in pure encephalitis
 
Evaluation
  • CT scan of the head
    • performed first
    • rules-out space occupying lesions
    • normal CT does not rule-out encephalitis
    • MRI is the preferred imaging modality for HSV encephalitis
  • Lumbar puncture
    • perform after head imaging
    • cerebral spinal fluid analysis to determine etiology
      • bacterial, viral, fungal
    • PCR
      • most accurate for herpes encephalitis
    • culture
    • Gram stain
  • Brain biopsy
    • last resort
    • only if etiology is unknown
Differential
  • Intracranial malignancy
    • primary or metastatic
  • Medication side-effects
  • Paraneoplastic or autoimmune disease
    • anti-NMDA receptor encephalitis
Treatment
  • Supportive
    • assess airway, breathing, and circulation (ABCs)
    • initiate seizure precautions
    • manage fever and pain
  • Treatment is then dependent on etiology
    • HSV encephalitis
      • initiate acyclovir immediately  
        • if renal impairment must give IV fluids to prevent crystalline nephropathy 
      • can be considered with VZV encephalitis
      • associated with a reduction in morbidity and mortality
      • foscarnet in acyclovir-resistant herpes
  • Serial monitoring of intracranial pressure
Prevention, Prognosis, and Complications
  • 50 - 75% mortality in untreated HSV encephalitis
  • < 1 or > 55 years old, immunocompromised is associated with poorer outcome
 

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Questions (5)
Lab Values
Blood, Plasma, Serum Reference Range
ALT 8-20 U/L
Amylase, serum 25-125 U/L
AST 8-20 U/L
Bilirubin, serum (adult) Total // Direct 0.1-1.0 mg/dL // 0.0-0.3 mg/dL
Calcium, serum (Ca2+) 8.4-10.2 mg/dL
Cholesterol, serum Rec: < 200 mg/dL
Cortisol, serum 0800 h: 5-23 μg/dL //1600 h:
3-15 μg/dL
2000 h: ≤ 50% of 0800 h
Creatine kinase, serum Male: 25-90 U/L
Female: 10-70 U/L
Creatinine, serum 0.6-1.2 mg/dL
Electrolytes, serum  
Sodium (Na+) 136-145 mEq/L
Chloride (Cl-) 95-105 mEq/L
Potassium (K+) 3.5-5.0 mEq/L
Bicarbonate (HCO3-) 22-28 mEq/L
Magnesium (Mg2+) 1.5-2.0 mEq/L
Estriol, total, serum (in pregnancy)  
24-28 wks // 32-36 wks 30-170 ng/mL // 60-280 ng/mL
28-32 wk // 36-40 wks 40-220 ng/mL // 80-350 ng/mL
Ferritin, serum Male: 15-200 ng/mL
Female: 12-150 ng/mL
Follicle-stimulating hormone, serum/plasma Male: 4-25 mIU/mL
Female: premenopause: 4-30 mIU/mL
midcycle peak: 10-90 mIU/mL
postmenopause: 40-250
pH 7.35-7.45
PCO2 33-45 mmHg
PO2 75-105 mmHg
Glucose, serum Fasting: 70-110 mg/dL
2-h postprandial:<120 mg/dL
Growth hormone - arginine stimulation Fasting: <5 ng/mL
Provocative stimuli: > 7ng/mL
Immunoglobulins, serum  
IgA 76-390 mg/dL
IgE 0-380 IU/mL
IgG 650-1500 mg/dL
IgM 40-345 mg/dL
Iron 50-170 μg/dL
Lactate dehydrogenase, serum 45-90 U/L
Luteinizing hormone, serum/plasma Male: 6-23 mIU/mL
Female: follicular phase: 5-30 mIU/mL
midcycle: 75-150 mIU/mL
postmenopause 30-200 mIU/mL
Osmolality, serum 275-295 mOsmol/kd H2O
Parathyroid hormone, serume, N-terminal 230-630 pg/mL
Phosphatase (alkaline), serum (p-NPP at 30° C) 20-70 U/L
Phosphorus (inorganic), serum 3.0-4.5 mg/dL
Prolactin, serum (hPRL) < 20 ng/mL
Proteins, serum  
Total (recumbent) 6.0-7.8 g/dL
Albumin 3.5-5.5 g/dL
Globulin 2.3-3.5 g/dL
Thyroid-stimulating hormone, serum or plasma .5-5.0 μU/mL
Thyroidal iodine (123I) uptake 8%-30% of administered dose/24h
Thyroxine (T4), serum 5-12 μg/dL
Triglycerides, serum 35-160 mg/dL
Triiodothyronine (T3), serum (RIA) 115-190 ng/dL
Triiodothyronine (T3) resin uptake 25%-35%
Urea nitrogen, serum 7-18 mg/dL
Uric acid, serum 3.0-8.2 mg/dL
Hematologic Reference Range
Bleeding time 2-7 minutes
Erythrocyte count Male: 4.3-5.9 million/mm3
Female: 3.5-5.5 million mm3
Erythrocyte sedimentation rate (Westergren) Male: 0-15 mm/h
Female: 0-20 mm/h
Hematocrit Male: 41%-53%
Female: 36%-46%
Hemoglobin A1c ≤ 6 %
Hemoglobin, blood Male: 13.5-17.5 g/dL
Female: 12.0-16.0 g/dL
Hemoglobin, plasma 1-4 mg/dL
Leukocyte count and differential  
Leukocyte count 4,500-11,000/mm3
Segmented neutrophils 54%-62%
Bands 3%-5%
Eosinophils 1%-3%
Basophils 0%-0.75%
Lymphocytes 25%-33%
Monocytes 3%-7%
Mean corpuscular hemoglobin 25.4-34.6 pg/cell
Mean corpuscular hemoglobin concentration 31%-36% Hb/cell
Mean corpuscular volume 80-100 μm3
Partial thromboplastin time (activated) 25-40 seconds
Platelet count 150,000-400,000/mm3
Prothrombin time 11-15 seconds
Reticulocyte count 0.5%-1.5% of red cells
Thrombin time < 2 seconds deviation from control
Volume  
Plasma Male: 25-43 mL/kg
Female: 28-45 mL/kg
Red cell Male: 20-36 mL/kg
Female: 19-31 mL/kg
Cerebrospinal Fluid Reference Range
Cell count 0-5/mm3
Chloride 118-132 mEq/L
Gamma globulin 3%-12% total proteins
Glucose 40-70 mg/dL
Pressure 70-180 mm H2O
Proteins, total < 40 mg/dL
Sweat Reference Range
Chloride 0-35 mmol/L
Urine  
Calcium 100-300 mg/24 h
Chloride Varies with intake
Creatinine clearance Male: 97-137 mL/min
Female: 88-128 mL/min
Estriol, total (in pregnancy)  
30 wks 6-18 mg/24 h
35 wks 9-28 mg/24 h
40 wks 13-42 mg/24 h
17-Hydroxycorticosteroids Male: 3.0-10.0 mg/24 h
Female: 2.0-8.0 mg/24 h
17-Ketosteroids, total Male: 8-20 mg/24 h
Female: 6-15 mg/24 h
Osmolality 50-1400 mOsmol/kg H2O
Oxalate 8-40 μg/mL
Potassium Varies with diet
Proteins, total < 150 mg/24 h
Sodium Varies with diet
Uric acid Varies with diet
Body Mass Index (BMI) Adult: 19-25 kg/m2
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(M2.NE.69) A 32-year-old female who was previously healthy is brought to the emergency department by her concerned fiance who states that she is acting very abnormally. He states that over the past day she has developed a fever, become progressively more confused, and is "just not acting like herself." On exam, she exhibits altered mental status. Her vitals are demonstrated as: T: 39 deg C, HR: 102 bpm, BP: 130/90 mmHg, RR: 12, SaO2: 100%. The emergency physician obtains a lumbar puncture which demonstrates the following CSF analysis: normal opening pressure, elevated lymphocyte count, elevated protein, elevated RBCs, and normal glucose. An MRI is obtained to confirm the diagnosis and is illustrated in Figure A. Which of the following organisms is most likely responsible for this patient's presentation? Review Topic

QID: 103092
FIGURES:
1

C. neoformans

9%

(2/23)

2

JC virus

4%

(1/23)

3

S. pneumonia

0%

(0/23)

4

N. meningitidis

0%

(0/23)

5

HSV-1

83%

(19/23)

M2

Select Answer to see Preferred Response

PREFERRED RESPONSE 5

(M2.NE.72) A 22-year-old male with no prior medical history is brought to the emergency department by his college roommate after having a seizure. The roommate states that over the past day he seems to have gotten very confused, developed a fever, and then 1 hour ago had a seizure. On exam, the patient exhibits an altered mental status and his vitals are demonstrated as: T: 40 deg C, HR: 95, BP: 120/92, RR: 13, SaO2: 99%. The emergency physician obtains head CT as demonstrated in Figure A and a lumbar puncture which demonstrates the following CSF analysis: normal opening pressure, elevated lymphocyte count, elevated protein, elevated RBCs, and normal glucose. An MRI is obtained to confirm the diagnosis (Figure B) and appropriate treatment is initiated. Adequate hydration must be maintained during therapy to prevent which adverse effect of the treatment? Review Topic

QID: 103095
FIGURES:
1

Hypernatremia

13%

(3/23)

2

Nephrotoxicity

78%

(18/23)

3

Headache

0%

(0/23)

4

Nause and vomiting

0%

(0/23)

5

Stevens–Johnson syndrome

4%

(1/23)

M2

Select Answer to see Preferred Response

PREFERRED RESPONSE 2
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