Thalamic stimulation and recording in patients with deafferentation and central pain

Thalamic exploration was carried out in 39 patients with central or deafferentation pain. Several patients were explored more than once or bilaterally; therefore, 52 explorations were carried out. In 16 cases, microelectrode recording and microstimulation were employed. In the deafferented thalamus, a phenomenon of central allodynia was identified, in which patients with hyperpathia experience pain on stimulation rather than the usual sensations. With microrecording, a distinct unit firing in bursts can be identified and classified into three types. In several patients, the thalamic somatotopic map is found to be altered, and this reorganization can be classified into four types.