Brain : a journal of neurology
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In the syndrome of post-herpetic neuralgia (PHN), the nature of the sensory disturbance and its relationship both to the severity and cause of the pain is controversial. To address these issues, sensory mapping and quantitative thermal sensory testing was carried out four times in separate sessions on 35 subjects with established PHN. All subjects had pain affecting the torso or extremities and brush-evoked allodynia. ⋯ This implies that there is no simple relationship between loss of peripheral nerve function and spontaneous or evoked pain. Rather, the preservation of several sensory modalities in their area of maximal pain suggests that in some PHN patients, activity in primary afferent nociceptors that remain connected to both their peripheral and central targets contributes significantly to ongoing pain. Although other mechanisms are likely to contribute to the pain, the demonstrated responsivity of PHN to topical agents including local anaesthetics, capsaicin, and non-steroidal anti-inflammatory drugs, supports this proposed mechanism of pain generation.