Discussion
In our study, it was observed that the patients with HP had lower vitamin B 12 values than the control group and the patients with HI. In addition, also the vitamin B12 values of the patients with HI did not differ from the control group.
The relationship between HP and HI, which are two symptoms whose etiopathogenesis is not fully understood, has inspired many studies before8-10. Diagnostic biopsies show that epidemal innervation is almost completely lost in HI while excessive electrical activity of peripheral nociceptive neurons in sensory ganglia or distal axon ends is the main cause for HP8. In a study conducted with 586 shingles patients, it was reported that HI accompanies both acute zoster and post herpetic neuralgia, and although increased age is a risk factor for HP, no relation was found between HI and age9. In the study conducted by Ishikawa et al., although HI accompanies 44% of patients with post herpetic neuralgia and regresses with HP treatment, no relation was found between itching and pain intensity, and emphasizing that there is no major neuropathic component for and HI, they reported that HP and HI may have different mechanisms10.
There are limited studies examining the relationship between vitamin b 12 and HP and HI 11,12. The study of Chen et al. reported that vitamin B12 values of the shingles patients with HP were lower than the control group11. In the study investigating the effect of local injections of B vitamins on HP and HI, Xu et al. reported that Vitamin B1 has a significant atipruritic effect, while vitamin B12 has an analgesic effect, and reported that combinations of these vitamins have both antipruritic and analgesic dual effects 12.
In our study, while the level of vitamin b12 was found to be low in HP, we did not find a relationship with HI. Our findings contradict the previous literature examining the relationship between vitamin B12 and HI and HP, supporting the idea that HI has a different pathway than other HP.
Both HP and HI are two important symptoms of shingles that negatively affect the quality of life13. In the treatment of HP; gabapentin, pregabalin, tricyclic antidepressants, lidocalin, and capsaicin can be used, but satisfactory results cannot be obtained14. Antihistamines and corticosteroids are ineffective for HI, and although pain and itching are thought to have similar pathways, many drugs effective in relieving neuropathic pain are ineffective in relieving neuropathic itching, nor even opioid analgesics used for treating HP can cause HI9. HI is not uncommon among zona patients, althougt it is not be elucidated in literature yet, and this reveals the fact that a separate treatment modality required for HI10.
According to our study, while vitamin B 12 deficiency is associated with HP formation, there is no relationship between it and HI formation. Further studies focusing on HI etiopathogenesis may contribute to the treatment of this symptom that negatively affects the quality of life.