Psychophysical Assessment of Patients with Posttraumatic Neuropathic Trigeminal Pain

This article reviews the utility of psychophysical approaches in the assessment of posttraumatic neuropathic trigeminal pain. Methods of quantitative sensory testing are derived from psychophysical principles and provide a widely accepted means for characterizing sensory dysfunction in patients who experience injury to the trigeminal nerve. No published study, however, has sought to compare sensory findings from trigeminal nerve-injured patients who develop neuropathic pain with those from trigeminal nerve-injured patients who remain pain-free. Moreover, sensory testing data from trigeminal nerve-injured patients with pain have been published in only a few reports. As a result, remarkably little is known about sensory factors associated with the development of posttraumatic trigeminal neuralgia. Review of the separate literatures suggests that both trigeminal nerve-injured patients with pain and pain-free trigeminal nerve-injured patients exhibit grossly similar impairments in sensory function. In addition, trigeminal nerve-injured patients with pain may be more likely to report cold allodynia than patients without pain and to exhibit signs of central sensitization such as allodynia to light brushing tactile stimuli and abnormal temporal summation of pain. New studies using state-of-the-art psychophysical methods are needed to search for sensory markers that bear on the development of pain. Moreover, the relationship between psychophysical indices of central sensitization and measures of clinical pain should be addressed to obtain a better understanding of the underlying pathophysiology. Keywords: allodynia, neuropathic pain, sensitization, sensory testing, trigeminal nerve injury