Up to date, it is generally assumed that motor nervous system complication of herpes zoster can be occurred through the following several ways. First, it can be caused as infection that first begins in spinal dorsal root ganglion and then progresses to anterior horn through motor nerve root. Second, it can be a result of segmental myelitis. Third, it can be caused by secondary degeneration of affected motor nerve root. Fourth, it can be caused by inflammation of both sensory and motor nervous system.
3 Of neurological complications in herpes zoster, segmental paralysis is focal motor paralysis that occurs in a myotome corresponding to the dermatome having a skin eruption, which occurs in approximately 0.5-5% of all herpes zoster cases.
4 On the other hand, there have been six reports of non-segmental peripheral polyneuropathy to date. Mondelli and colleagues
6,
7 reported four cases of patients with peripheral polyneuropathy diagnosed as a complication with no relation to the dermatome, along with electrodiagnostic findings. However, in four cases, all patients were diagnosed with diabetes; so diabetic peripheral neuropathy had to be taken into consideration. Also, Dayan and colleagues
5 reported two cases of patients diagnosed through nerve biopsy and electrodiagnostic findings, but the electrodiagnostic finding was insufficient because there's only nerve conduction study. The pathophysiology of peripheral polyneuropathy secondary to herpes zoster is unclear, but the discovery of varicellar zoster virus and its products in endoneurium, perineurium and epineurium within the peripheral nervous system (PNS) shows that the virus itself or the viral infection causes neural damage as they move from spinal dorsal root ganglion to nerve root and PNS.
6,
8 In this case, a skin eruption occurred in the left T11 dermatome and the motor paralysis occurred symmetrically in both foot dorsiflexors and extensor halluces longus related to the L5-S1 myotome. Thus, the motor paralysis in this case is classified as non-segmental paralysis that is diagnosed as peripheral polyneuropathy by a electrodiagnostic study. Neurological complications caused by herpes zoster are difficult to notice by both patients and clinicians due to the presence of severe pain.
3 In this case, neurological complications were not detected in the early stages of disease because of the severe pain, and assessment during walking could not be carried out due to aspiration pneumonia. Generally, herpes zoster can be cured without any complications.
3 However, in this case, the patient had a compromised immune system that had been affected by CML. So, the varicella zoster virus might have a relatively strong pathogenicity. And due to the strong pathogenicity, the herpes zoster could not be cured as easily as other general cases, and even progressed to neurological complication. The typical chemotherapeutic agent for CML with a Philadelphia chromosome is Glivec®. In this case, the patient took Glivec®, therefore the possibility of neurological complications caused by Glivec® has to be taken into consideration. However, until now, neurological complications caused by Glivec® have been reported only once - in a patient who was administered Glivec® for 5.5 years.
9 In this case, the patient stopped Glivec® intake due to pancytopenia and the neurological complication occurred after a week of Glivec® intake. So it is very unlikely that Glivec® is the cause of the complication. In addition, since there had been remarkable improvement after antiviral agent intake, there is a higher possibility that the neurological complication was caused by invasion by varicella zoster virus into the peripheral nervous system. For patients with compromised immune systems due to CML, herpes zoster is difficult to cure and the disease can even progress to produce complications in the PNS. Therefore, we suggest that assessment and thorough treatment of herpes zoster infection in patients with compromised immune s y s t em, focus ing on ne r vous s y s t em complications (including peripheral polyneuropathy) as well as pain are essential.