Anatomico-clinical correlation in focal thalamic lesions

Summary The authors emphasize the interest of certain observations on account of the specificity of the symptoms and the discreteness of the lesions. In these cases, pathology in man can be considered acting as stereotaxic targets, and therefore valuable for the understanding of thalamic functions.Vascular lesions are the most useful being topographically precise. Observations which can be used are indeed rare, but their value is incontrovertible. The authors describe successively partial sensory syndromes, cerebellar ataxia and mental disorders, which are in fact the only parts of thalamic symptomatology in which exceptional cases permit clinico-anatomical focal correlation.Partial sensory disorders can be localized to the face, the upper limb, the lower limb; they can have a cheiro-oral, cheiro-podo-oral, or pseudo-radicular topography. Their study leads to a somatotopical mapping of the sensory relay nuclei of the thalamus in man. In some cases taste disorders are added to somatosensory disorders. This has been explained by a gustatory thalamic center (in the medial part of the posterior ventral nucleus) close to the representation of the tongue in the somatosensory center.Certain observations prove the existence of a cerebellar component in thalamic ataxia. These cases corroborate what is known of the fan-like termination of cerebellar (brachium conjunctivum) afferents in the thalamus. The somatotopical organisation of the afferents may be discussed.As far as mental disturbances are concerned, clinico-anatomical correlation can not have such a pin-point precision. They have, however, confirmed the existence of a thalamic dementia especially when medial nuclei are interested. Moreover it can be demonstrated that Papez's hippocampo-mammillary circuit has an important relay in nucleus ventralis anterior. The lesions giving rise to mental disorders are particularly important, insofar as no such conclusive evidence can be elicited from experimental observations.Translated from a paper presented at the Joint Meeting of the German and French Neurological Societies, Munich 1970.