Post-herpetic neuralgia in unusual anatomic area
A 55-year-old female presented with a small bullous lesions on the left sole of the foot, being prescribed antibiotics and non-steroid anti-inflammatory drug (NSAID). The patient has been diagnosed with herpes zoster in the healing phase of the lesions and had severe burning pain throughout the left lower limb (LLL). She was taking amitriptyline (75 mg/day) with no relief. Patient referred persistent severe pain = 10 by the visual analog scale (VAS); burning pain in shock which would worsen at night.
The most likely diagnosis of this presentation is
- Post herpetic neuralgia
The reactivation of the varicella-zoster virus in cranial nerves and spinal root ganglia causes herpes zoster (HZ), in general triggered decades after the primary varicella infection.1,2 The signs and symptoms start with a mild to moderate skin burning prodrome, often followed by fever, chills, headache and malaise1 which is observed from 1-4 days before skin lesions. Most common HZ complication is post-herpetic neuralgia (PHN).3 HZ is treated with antiviral drugs which accelerate skin rash healing, decrease pain intensity2 and the incidence of post-herpetic neuralgia (PHN).4,5-8 PHN is characterized by chronic neuropathic pain starting from 1-6 months after skin rash healing and may last for years. PHN is a common cause of chronic pain in elderly individuals and incidence varies from 10% to 20% in immunocompetent adults.9,10,11. In 50-60% cases, HZ affects chest and face and sacral dermatomes are involved in just 5%.12 PHN pain is chronic and there can be pain-free periods, milder symptoms, alternating with exacerbation episodes. First line drugs for PHN treatment are: anticonvulsants and tricyclic antidepressants. Opioids may also be used as analgesics.2
The patient did not have any prior medical history
Examination and Laboratory Investigations
She had allodynia and hyperalgesia in LLL until the root of the thigh. There were few crust-type skin lesions, restricted to the sole of the left foot.
Carbamazepine (400 mg/day) and codeine (30 mg) were started every 6 hours and patient returned with no improvement. So, carbamazepine was replaced by gabapentin (900 mg/day) and a series of sciatic nerve peripheral blocks was performed. There has been clinical improvement with decreased pain intensity (VAS = 7) and restriction of the affected area to dorsum and sole of left foot. Pain was restricted to left foot toes, however with allodynia and shock in this region, especially at night. Gabapentin was replaced by pregabalin (150 mg/day), however pain intensity and characteristics have not changed. Symptoms were totally resolved with analgesic block by the pentablock technique with 0.25% bupivacaine (10 mL) and clonidine (75 µg), but returned in 48-72 hours. After 6 months of treatment, duloxetine (60 mg/day) was introduced, showing significant improvement (VAS = 2). Pregabalin was withdrawn and patient was maintained under observation with weekly visits.
Being a self-limited disease HZ, there may be severe complications. In the prodromic period, its diagnosis is difficult because it may take up to three weeks for the appearance of skin lesions. The most common affected areas are lower limbs, chest and face. 13 In this case, the anatomic HZ manifestation in an unusual area was critical for the late diagnosis, which has prevented the treatment with antiviral drugs in the acute phase. HZ is treated with antiviral drugs which accelerate skin rash healing, decrease pain intensity and the incidence of PHN, the most common HZ complication.2, 13 However, some patients shall develop PHN even after having adequately received antiviral drugs.3
PHN treatment difficulties and negative impact are considerable for the personal and social life of patients because they affect sleep and the ability to work and perform physical activities, thus affecting their quality of life. So, one must pay attention to signs and symptoms in unusual locations for HZ, since early diagnosis and treatment are critical in the attempt to optimize pain approach during the acute phase and to prevent its chronicity.
- Pearce JM. Post herpetic neuralgia. J Neurol Neurosurg Psychiatry 2005;76(4):572
- Wu CL, RAJA SN. An update on the treatment of postherpetic neuralgia. J Pain 2008;9(1):19-30
- Gilden DH, Kleinschmidt-DeMasters BK, LaGuardia JJ, et al. Neurologic complications of the reactivation of varicella-zoster virus. N Engl J Med 2000;342(9):635-45
- Schmader KE, Dworkin RH. Natural history and treatment of herpes zoster. J Pain 2008;9(1 Suppl 1):S3-9
- Hall GC, Carroll D, McQuay HJ. Primary care incidence and treatment of four neuropathic pain conditions: descriptive study, 2002-2005. BMC Fam Pract 2008;9(26):1-9
- Johnson RW, McElhaney J. Postherpetic neuralgia in the elderly. Int J Clin Pract 2009;63(9):1386-91
- Ursini T, Tontodonati M, Manzoli L, et al. Acupuncture for the treatment of severe acute pain in herpes zoster: results of a nested, open-label, randomized trial in the VZV pain study. BMC Complement Altern Med 2011;11(46):1-8
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- Bjekic M, Markovic M, Sipetic S. Penile herpes zoster: an unusual location for a common disease. Braz J Infect Dis 2011;15(6):599-600
- Opstelten W, Eekhof J, Neven AK, et al. Treatment of herpes zoster. Can Fam Physician 2008;54(3):373-7