Historical controversies about the thalamus: from etymology to function.

The authors report on and discuss the historical evolution of the 3 intellectual and scientific domains essential for the current understanding of the function of the human thalamus: 1) the identification of the thalamus as a distinct anatomical and functional entity, 2) the subdivision of thalamic gray matter into functionally homogeneous units (the thalamic nuclei) and relative disputes about nuclei nomenclature, and 3) experimental physiology and its limitations.Galen was allegedly the first to identify the thalamus. The etymology of the term remains unknown although it is hypothesized that Galen may have wanted to recall the thalamus of Odysseus. Burdach was the first to clearly and systematically define the thalamus and its macroscopic anatomy, which paved the way to understanding its internal microarchitecture. This structure in turn was studied in both nonhuman primates (Friedemann) and humans (Vogt and Vogt), leading to several discrepancies in the findings because of interspecies differences. As a consequence, two main nomenclatures developed, generating sometimes inconsistent (or nonreproducible) anatomo-functional correlations. Recently, considerable effort has been aimed at producing a unified nomenclature, based mainly on functional data, which is indispensable for future developments. The development of knowledge about macro- and microscopic anatomy has allowed a shift from the first galenic speculations about thalamic function (the "thalamus opticorum nervorum") to more detailed insights into the sensory and motor function of the thalamus in the 19th and 20th centuries. This progress is mostly the result of lesion and tracing studies. Direct evidence of the in vivo function of the human thalamus, however, originates from awake stereotactic procedures only.Our current knowledge about the function of the human thalamus is the result of a long process that occurred over several centuries and has been inextricably intermingled with the increasing accumulation of data about thalamic macro- and microscopic anatomy. Although the thalamic anatomy can currently be considered well understood, further studies are still needed to gain a deeper insight into the function of the human thalamus in vivo.

Functional neurosurgery. The modulation of neural and mind circuits.

Different complex neuroanatomical and neurochemical circuits regulate a variety of neuronal behaviors and brain functions. Any disturbance in these circuits can generate functional disorders such as movement disorders, epilepsy, pain, memory disorders, and psychiatric disorders. Functional neurosurgery aims to restore these functions, either by removing or isolating the abnormally behaving neurons or by modulating the disturbed circuits. Neuromodulation is a fast-growing field, powered by the recent advances in neuroimaging and technology. Here, we discuss recent advances and new horizons in functional neurosurgery.

Hassler and Dieckmann's seminal paper on stereotactic thalamotomy for Gilles de la Tourette syndrome: translation and critical reappraisal.

Papers concerning the use of deep brain stimulation to the thalamus for relief of symptoms of Tourette syndrome have frequently cited a paper by Hassler and Dieckmann, published in 1970. We present a translation of this paper and discussion in English.

History repeats itself.

Although many advances in stereotactic surgery appear to be of recent origin, there are precedents in the literature documenting the planting of those seeds that eventually grew into common procedures. Pallidotomy was the first stereotactic procedure in humans that used the Spiegel-Wycis apparatus in 1947. Other targets for Parkinson's disease have their roots in the decade following that. Using stereotactic techniques to target solid or cystic lesions was introduced in the 1950's, when either calcification or pneumoencephalography were necessary to visualize the mass. One of the first uses of computers in surgery was in stereotaxis. Infusion of a neurotransmitter was first done over 30 years ago.

Lesions as therapy: surgical intervention in Parkinson's disease prior to L-dopa.

The study of Parkinson's disease has undergone vast changes across its almost 200 year history. Over this period, research scientists have added dramatic detail to their understanding both of the motor system in general and the etiology of Parkinson's disease specifically. This expanded understanding has been facilitated, particularly, by the work of clinicians with the goal of improving treatments designed to ameliorate its symptoms. This article examines the evolution of one particular clinical approach, the production of lesions to segments of the basal ganglia, from its inception, through its "golden era," disuse, and rebirth.

[History of stereotaxis]. / Quelques considérations sur l'histoire de la stéréotaxie.

The concept of stereotaxy is essentially based on functional topography, which continuously evolved from the first observation by Hippocrates of a motor deficit contralateral to an hemispheric wound, to the characteristic example of Broca's speech area. The fate of a method depends on the need for it. When an outsider phenomenon, such as a pharmacological newcomer, occurred, which brought, at least for a given period, a satisfactory solution, the need for the method disappeared and sent it in oblivion. At the same time, the understanding that some pathologies, such as brain tumors, were not adequately taken care of by classical surgery and could eventually respond correctly to general treatments, such as chemotherapy or radiotherapy, induced the application of this forgotten, or near to be abandoned, method to a totally new field: this is what Talairach and his associates did when they introduced the stereotactic biopsy, at a time where movement disorders needed less surgery as levodopa had come and provided a very attractive treatment. When, on the contrary, it appeared that some forms of Parkinson's disease less responded to the drugs or were plauged by motor fluctuations and dyskinesias, there could be a new need for surgery. However, complications became at that time unacceptable and the method was required to evolve towards new directions where efficacy goes with a negligible morbidity. This led eventually to new developments such as brain grafting or more recently high frequency deep brain stimulation. Stereotaxy, like other methods, has experienced this type of fluctuation in its history and has on each occasion progressed and acquired new skills and possibilities, far beyond what it was initially designed for.