Thalamic pain syndrome of Dejérine-Roussy. Differentiation of four subtypes assisted by somatosensory evoked potentials data.

In 30 patients with a thalamic vascular lesion and clinical somatosensory disturbances in the opposite hemibody without hemiplegia, four nosological groups were identified: group 1 had no central pain but complete hemianesthesia and loss of cortical somatosensory evoked potentials (SEPs) on the affected side (analgic thalamic syndrome). Group 2 had central pain, severe hypoesthesia, and loss of cortical SEPs. Group 3 had central pain and hypoesthesia, with cortical SEPs present, although reduced or delayed on the affected side. Group 4 had central pain with preserved touch and joint sensations and normal SEPs (pure algetic thalamic syndrome). Clinical signs and SEP titration of the actual involvement of lemniscal pathways in these four groups of patients with thalamic syndrome are discussed in relation to current pathophysiology of central pain.