In rare cases, the patient might also experience muscle weakness, tremor, or paralysis if the nerves involved also control muscle movement. Pathophysiology
Postherpetic neuralgia is thought to be due to nerve damage caused by herpes zoster. The damage causes nerves in the affected dermatomic area of the skin to send abnormal electrical signals to the brain. These signals may convey excruciating pain, and may persist or recur for months, years, or for life.A key factor in the neural plasticity underlying neuropathic pain is altered gene expression in sensory dorsal root ganglia neurons. Injury to sensory nerves induces neurochemical, physiological, and anatomical modifications to afferent and central neurons, such as afferent terminal sprouting and inhibitory interneuron loss. Following nerve damage, NaCl channel accumulation causes hyperexcitability, and downregulation of the TTX-resistant Nav1.8 (sensory neuron specific, SNS1) channel and upregulation of TTX-sensitive Nav1.3 (brain type III) and TRPV1 channels. These changes contribute to increased NMDA glutamate receptor-dependent excitability of spinal dorsal horn neurons and are restricted to the ipsilateral (injured) side. A combination of these factors could contribute to the neuropathic pain state of postherpetic neuralgia. Diagnosis
Lab Studies:
No laboratory work is usually necessary. Results of cerebrospinal fluid evaluation are abnormal in 61%. Pleocytosis is observed in 46%, elevated protein in 26%, and VZV DNA in 22%. These findings are not predictive of the clinical course of postherpetic neuralgia. Viral culture or immunofluorescence staining may be used to differentiate herpes simplex from herpes zoster in cases that are difficult to distinguish clinically. Antibodies to herpes zoster can be measured.
Doxercalciferol (or 1-hydroxyergocalciferol,  trade name Hectorol) is drug for secondary hyperparathyroidism and metabolic bone disease. It is a synthetic analog of ergocalciferol (vitamin D2). It suppresses parathyroid synthesis and secretion.Docercalciferol is the vitamin D2 analogue of alfacalcidol. It undergoes 25-hydroxylation in the liver to become the active ercalcitriol, without the involvement of kidneys. == References ==