Physiological Identification of The Thalamic Nucleus

Introduction  Stereotaxic operations on the ventrolateral nucleus (VL) of the thalamus are now the most commonly used surgical procedure for alleviating the parkinsonian syndrome and other extrapyramidal manifestations. Exact location of the nucleus is usually estimated on the basis of radiological measurements of the third ventricle, with special reference to the anterior and posterior commissures. Three-dimensional relationship of each basal structure is found in the brain atlases by Schaltenbrand and Bailey, Spiegel and Wycis, and Talairach,^20,22,24 which treat mostly of the normal adult brain.Some physiological techniques have also been used for determining the location of the electrode tip within the thalamus. For example, high-frequency stimulation of the VL is thought to cause increase or decrease of the tremorous movement^1,6,18; this technique naturally is inapplicable in the deeply narcotized state.Therefore, the methodological difficulties in actual surgery on the severely atrophied brain or in children under general narcosis