Dear Editor,


We read with interest the narrative review by Fan et al. [1] on the early diagnosis of herpes zoster neuralgia by different approaches. It was concluded that early diagnosis of herpes zoster neuralgia before the onset of shingles is recommended in order to initiate early treatment and thereby reduce the incidence of post zoster neuralgia (PZN) [1]. The review is excellent but has limitations that are cause of concerns and should be discussed.

The major limitation of the study is that the wording is inconsistent or confusing. It is unclear whether the authors use the term “herpes zoster neuralgia” to mean local pain before or during shingles or neuropathic pain associated with PZN. This distinction is important because the pathophysiology and therapeutic management of both phenomena can be different.

There is a discrepancy between the goals formulated in the abstract (early diagnosis of PZN) and the goals formulated in the method section (early detection of herpes zoster) [1]. It is unclear whether the authors mean the same thing with herpes zoster and PZN. PZN can occur after the pain from the acute infection has completely resolved. It is also possible that the herpes zoster infection is completely painless.

With regard to herpes zoster neuralgia, it is not comprehensible how neuralgia can be diagnosed before the onset of symptoms, as stated in the abstract [1]. There is also a contradiction between saying that PZN can be prevented if diagnosed early. If a PZN already exists, it can no longer be prevented. It is also not possible for PZN to “erupt” [1].

It is also unclear how patients can develop PZN before onset of the rash, as stated in the Discussion [1]. Rash and shingles should have resolved before the beginning of PZN [2].

We disagree with the statement that CSF testing for varicella zoster virus (VZV) is not suitable for ordinary patients with shingles [1]. Single patients may have shingles and central nervous system (CNS) involvement at the same time [3]. Therefore, it is recommended to perform a lumbar puncture as early as there is suspicion of CNS involvement in all patients with or without shingles. Lumbar puncture is a simple, routine diagnostic procedure and, if carried out adequately, with a low risk of complications.

Because the pathophysiology of PZN neuralgia is unclear, it is questionable whether early diagnosis and treatment of herpes zoster will actually prevent the development or severity of PZN.

In summary, the interesting study has limitations that put the results and their interpretation into perspective. It is crucial to discriminate between pain that occurs together with the efflorescences and pain developing after resolution of the shingles.