Thalamic pain: anatomical and physiological indices of prediction

Abstract

Thalamic pain is a severe and treatment-resistant type of central pain that may develop after thalamic stroke. Lesions within the ventrocaudal regions of the thalamus carry the highest risk to develop pain, but its emergence in individual patients remains impossible to predict. Because damage to the spino-thalamo-cortical system is a crucial factor in the development of central pain, in this study we combined detailed anatomical atlas-based mapping of thalamic lesions and assessment of spinothalamic integrity using quantitative sensory analysis and laser-evoked potentials in 42 thalamic stroke patients, of whom 31 had developed thalamic pain. More than 97% of lesions involved an area between 2 and 7 mm above the anterior-posterior commissural plane. Although most thalamic lesions affected several nuclei, patients with central pain showed maximal lesion convergence on the anterior pulvinar nucleus (a major spinothalamic target) while the convergence area lay within the ventral posterior lateral nucleus in pain-free patients. Both involvement of the anterior pulvinar nucleus and spinothalamic dysfunction (nociceptive thresholds, laser-evoked potentials) were significantly associated with the development of thalamic pain, whereas involvement of ventral posterior lateral nucleus and lemniscal dysfunction (position sense, graphaesthesia, pallaesthesia, stereognosis, standard somatosensory potentials) were similarly distributed in patients with or without pain. A logistic regression model combining spinothalamic dysfunction and anterior pulvinar nucleus involvement as regressors had 93% sensitivity and 87% positive predictive value for thalamic pain. Lesion of spinothalamic afferents to the posterior thalamus appears therefore determinant to the development of central pain after thalamic stroke. Sorting out of patients at different risks of developing thalamic pain may be achievable at the individual level by combining lesion localization and functional investigation of the spinothalamic system. As the methods proposed here do not need complex manipulations, they can be added to routine patients' work up, and the results replicated by other investigators in the field.

Intracerebral hemorrhage location and outcome among INTERACT2 participants

“…Strokes in the thalamus have a high incidence of residual sensory disability and are traditionally associated with pain syndromes, 19 while lesions of spinothalamic afferents to the posterior thalamus are associated with development of central pain. 20 This effect seems small in ICH.…”

Evidence‐based source modeling of nociceptive cortical responses: A direct comparison of scalp and intracranial activity in humans

“…Nociceptive laser‐evoked potentials (LEPs) are an important tool both in basic research and in the clinics, where they play a major role in neuropathic pain diagnosis (reviews in Cruccu et al [] and Garcia‐Larrea []), and possibly prediction (Vartiainen et al, ). This study proposes a source model of LEPs using a resolutely different approach to previous work, by seeding sources of high‐density EEG at locations gathered from other neuroimaging data.…”

Clinical evoked potentials in neurology: a review of techniques and indications

“…The identification of patients who are at risk of developing poststroke pain is important to insure rapid treatment, especially for those who are unable to communicate. LEP abnormalities were associated with abnormal heat/pain ratings and anterior pulvinar nucleus lesions in 27/31 patients, rendering a positive predictive value of 87% for thalamic poststroke pain 37. Interestingly, SEPs can be normal in these patients.…”