Lab and Imaging Studies
Lab Studies:
- No laboratory work is usually necessary.
- Results of cerebrospinal fluid (CSF) evaluation are abnormal in 61%.
- Pleocytosis is observed in 46%, elevated protein in 26%, and VZV DNA in 22%.
- These findings are not predictive of the PHN clinical course.
- Viral culture or immunofluorescence staining may be used to differentiate herpes simplex from herpes zoster in cases that are difficult to distinguish clinically.
- Antibodies to herpes zoster can be measured. A 4-fold increase has been used to support the diagnosis of subclinical herpes zoster (zoster sine herpete). However, a rising titer secondary to viral exposure rather than reactivation cannot be ruled out.
Imaging Studies:
- Magnetic resonance imaging (MRI) lesions attributable to HZ were seen in the brain stem and cervical cord in 56% (9/16) of patients.
- At 3 months after onset of HZ, 56% (5/9) of patients with an abnormal MRI had developed PHN.
- Of the 7 patients who had no HZ-related lesions on MRI, none had residual pain.
Read more about this topic: Postherpetic Neuralgia
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