Subtle Sensory Abnormalities Detected by Quantitative Sensory Testing in Patients with Trigeminal Neuralgia.

BACKGROUND Trigeminal neuralgia (TN) is characterized by paroxysmal pain attacks affecting the somatosensory distributions of the trigeminal nerve. It is thought to be associated with a neurovascular conflict most frequently, but pathomechanisms have not been fully elucidated. In general, no sensory deficit is found in routine clinical examination. There is limited data available, however, showing subtle subclinical sensory deficits upon extensive testing. OBJECTIVE We used quantitative sensory testing (QST) to detect abnormalities in sensory processing in patients with TN by comparing the affected and non-affected nerve branches with their contralateral counterparts and by comparing the results of the patients with those of controls. STUDY DESIGN Observational study. SETTING University Hospital, Departments of Neurosurgery, Institute for Cognitive and Clinical Neuroscience. METHODS QST was conducted on 48 patients with idiopathic TN and 27 controls matched for age and gender using the standardized protocol of the German Neuropathic Pain Network. Stimulations were performed bilaterally in the distribution of the trigeminal branches. The patients had no prior invasive treatment, and medications at the time of examination were noted. RESULTS In patients with TN deficits in warm and cold sensory detection thresholds in the affected and also the non-affected nerve branches were found. Tactile sensation thresholds were elevated in the involved nerve branches compared to the contralateral side. LIMITATIONS More data are needed on the correlation of such findings with the length of history of TN and with changes of the morphology of the trigeminal nerve. CONCLUSIONS QST shows subtle sensory abnormalities in patients with TN despite not being detected in routine clinical examination. Our data may provide a basis for further research on the development of TN and also on improvement after treatment. KEY WORDS Quantitative sensory testing, trigeminal neuralgia, facial pain, neuropathic pain, microvascular decompression, cranial nerve.