Postherpetic Neuralgia - Lab and Imaging Studies

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.