Journal of Neurology J Neurol (1989) 236:21-25 © Springer-Verlag 1989 Thalamic aphasia A conceptional critique R. P. M. Bruyn Department of Neurology, Free University Hospital, 1007 MB Amsterdam, de Boelelaan 1117, The Netherlands Summary. Four patients with aphasia due to small circumscribed thalamic lesions are presented. A review of the literature on thalamic aphasia revealed 16 similar cases. While the general consensus that only left-sided thalamic lesions are associated with aphasia is confirmed, analysis of the sites of the thalamic infarctions and the dysphasia elements did not reveal an unequivocal correlation. The explanation of this finding is that (a) disruption of any circuit, whether taking place in the connections or in the nuclei, leads to dysfunction and (b) thalamofrontal connections are not topographically arranged according to the thalamic nuclei, but show a frontal rostrocaudal/thalamic mediolateral interrelationship irrespective of thalamic nuclear masses. Key word: Thalamic aphasia Introduction The use of the CT in clinical practice has established that thalamie lesions of whatever nature may form the structural basis of speech dysfunction [1, 2, 4, 5, 8, 9, 12, 16, 18, 21-30, 33]. This fact has been noted in stereotaxic thalamotomy for parkinsonism [3, 13, 31], as well as in clinical reports [6, 7, 10, 11, 14, 20, 32]. The question whether the observed speech defect is attributable to disruption of the cortico-thalamo-cortical connections or to a lesion in one or more of the thalamic nuclei proper has been the subject of clinical-anatomical correlation studies [1, 12, 24, 29]. Given the intricate composition of the thalamus, in which nuclei and fibre systems are interwoven to such a complex degree that any lesion other than a selective neurotoxic or neurodegenerative one will involve both the fibre systems and the neuronal elements, this question is probably superfluous. Because language implies the activity of a cognitive semantic system, whereas speech is more an instrumental function, the present analysis of four cases with small and well-circumscribed lesions aimed to examine the relationship between speech dysfunction and small thalamic lesions. The results argue that speech dysfunction cannot be unequivocally tied to involvement of specific thalamic nuclei and underline from a clinical point of view the relevance of the anatomical data provided by Kievit and Kuypers [15, 17], who, by means of horseradish peroxidase injection in different parts of the frontal cortex in the rhesus monkey, showed that the Fig. la-f. CT scans showing the extent of the thalamic lesions in the four personal cases. Top line from left to right: a case 17, b case 18 2.5 months before the thalamic infarct, c case 18 at the time of the speech dysfunction. Bottom line from left to right: d, e case 19 at two levels; lease 20. The left side of the picture is the left side of the patient 22 t.., g + I + + Z + + +-+> N ,~ a : = o >~ ~+ ~ z z + z + + 4 . ++~ + + + 1 + + ~.~ _~ E d ~ + + + 1 1 + e'~ V. g-" eo < ~.~ > va + z + + + + + z + ~ :~ ~ b9 "-G c~, o~ X e'> II + ¢',,I :: c..) i+< + + + + 1 + ~ > m. =,~ff -g > .~ ea = g "G ~D D d~ + z z z z >~x.~ c,.) + + + +>4=~ff I I + + l l + cq eo ,.c; l-~ c q ~ c.;, ~ 0o + z ~ z z + ~ i + > :~ ~ Z Z ~= Z + + + + + + + > II d > ca ~g .-d e- e~ d + Z + + Z + I + Z + + + + + Z --~ @ + Z + + Z + + + ---+~ "a g g ,'~ © .= > >- d g: '~. Z Z + + Z + + + ---~> II 7 = O © ¢D "-G ~.~ d Z Z + + + + Z Z + > Z > + + + + z z z Z >> g~ .=_ .a [,- > + + + z z + I Z + > e~ O © ca It g. ~> + Cat) ~= 3 = + + Z Z + t + ---~> d© 0o c> 4-:, + + + + + + Z + + + ~ I + Z Z + + + ~ > II O e~ oa ¢0 Ca >~ >~ ~ ~..~ t.., O o =d e-, t,.a © O g ~a J ~<~ ,.-a .o ~ Z ~