Microbiology
Infections
Question 67 of 77
Which of the following pathogens is the most common cause of infectious encephalitis:
Answer:
Herpes simplex virus is the most common cause of infective encephalitis.Infective Encephalitis
Microbiology / Infections
Last Updated: 18th June 2019
Encephalitis is inflammation within the substance of the central nervous system.
Infective Agents
- Herpes simplex virus (most common cause)
- Temporal lobe is most frequently affected
- Virus replication in neurons, followed by the oedema associated with the inflammatory response accounts for the haemorrhagic necrosis and space-occupying nature of this form of the disease
- Varicella zoster virus
- Cytomegalovirus
- Arbovirus
- Mumps
- Measles
Clinical Disease
- Fever
- Headache
- Neck stiffness
- Impaired consciousness
- Focal neurological signs
- Seizures
Diagnosis
- Lumbar puncture
- Viral encephalitis leads to a lymphocytosis with normal CSF/plasma glucose ratio
- Elevated CSF to serum antibody ratios indicate CSF infection with the respective organism
- PCR analysis of CSF can be used to diagnose most viral infections
- Blood FBC, biochemistry, film, serology and cultures
- CT/MRI head may demonstrate focal lesions
- EEG
Treatment
- Treatment of herpes simplex encephalitis is with intravenous aciclovir
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
