Herpes zoster peripheral nerve complications: Their pathophysiology in spinal ganglia and nerve roots

Varicella zoster virus (VZV) causes chickenpox at the primary infection and then becomes latent in the spinal dorsal root ganglia; VZV can reactivate with aging, immunosuppression, stress, and other factors, occurring as herpes zoster (HZ) at 1-2 skin segments. HZ peripheral nerve complications caused by VZV reactivation include Hunt syndrome, segmental HZ paresis, post-herpetic neuralgia, and Guillain-Barré syndrome (GBS). We have encountered the rare HZ complications of upper-limb paresis, myeloradiculitis, and polyradiculoneuritis: an adult woman with upper-limb paresis consistent with the nerve root on segments above the thoracic HZ dermatome; another woman exhibiting ascending myeloradiculitis originating at the Th11-12 roots; an elderly woman with ascending VZV polyradiculoneuritis resembling GBS; an adult with VZV quadriplegia with disseminated HZ; and an elderly patient with VZV-associated polyradiculoneuritis. The three polyradiculoneuritis cases may be a new subtype of HZ peripheral neuropathy, but the pathophysiology for these HZ peripheral nerve complications unrelated to HZ dermatomes is unclear. We analyzed host factors, skin lesions, neurological and virological findings, and MRI results including 3D NerveVIEW in 15 Japanese patients treated at our facility for HZ peripheral neuropathy, including six differing from the HZ dermatome. Based on the clinical findings including MRI results of spinal ganglia and roots, we identified four possible routes for the patterns of VZV spread: (i) ascending spinal roots, (ii) ascending spinal cord, (iii) polyradiculopathy, and (iv) intrathecal spread. The incidence of HZ is increasing with the aging of many populations, and clinicians should be aware of these HZ neuropathies.