Pain remains the most enigmatic of our perceptions. From a physiological point of view, it corresponds to the excitation of pain receptors and their propagation pathways to the central nervous system. It is produced as a consequence of tissue injury and corresponds to an essential defense system in the living being. But it is also an emotional experience, a feeling, which is immediately associated with the ‘sensation’ of pain. Often, pain does not even involve tissue damage and is only the emotional experience. Pain’ is therefore a word whose meaning groups together subjective phenomena that are usually of an unpleasant character. These phenomena are interpreted in the Pain Unit according to personal experience and cultural and social conditioning factors.
From a strict point of view, neuropathic pain represents a neurological lesion or dysfunction (central or peripheral nervous system), it is a manifestation of a disorder of nerve fibers but it is, in any case, a sensory phenomenon involving abnormal activity in the sensory transmission pathways in whose development shadows persist and where routine electrophysiological studies cannot help us. Neuropathic pain is extremely difficult to manage. It is chronic and cannot usually respond to treatment with standard analgesics.
Establishing the diagnosis of neuropathic pain is complicated even for the clinician, as patients have difficulty expressing the symptoms they suffer. Thus, there are multiple descriptive sensory terms that physicians can associate with such pain: electric shock, tingling, itching, numbness, prickling or stiffness, straining and cutting.
Neuropathic pain is associated with multiple diseases of very different causes; we could establish a classification of diseases related to neuropathic pain according to their location: peripheral nerve (acquired, inherited or entrapment neuropathies), dorsal root ganglion (Herpes Zoster), dorsal horn (avulsion lesions), spinal tracts (trauma, tumors, syringomyelia or cervical discopathy), trunk/bridge (stroke or demyelination), thalamus (stroke, tumor demyelination) and cortex (stroke or seizures).