Thalamic alexia with agraphia

Abstract

Alexia with agraphia is defined as an acquired impairment affecting reading and writing ability. It can be associated with aphasia, but can also occur as an isolated entity. This impairment has classically been associated with a left angular gyrus lesion In the present study, we describe a case involving a patient who developed alexia with agraphia and other cognitive deficits after a thalamic hemorrhage. In addition, we discuss potential mechanisms of this cortical dysfunction syndrome caused by subcortical injury. We examined a patient who presented with alexia with agraphia and other cognitive deficits due to a hemorrhage in the left thalamus. Neuropsychological evaluation showed attention, executive function, arithmetic and memory impairments. In addition, language tests revealed severe alexia with agraphia in the absence of aphasia. Imaging studies disclosed an old thalamic hemorrhage involving the anterior, dorsomedial and pulvinar nuclei. Tractography revealed asymmetric thalamocortical radiations in the parietal region (left <right), and single photon emission computed tomography demonstrated hypoperfusion in the left thalamus that extended to the frontal and parietal cortices. Cortical cognitive deficits, including alexia with agraphia, may occur as the result of thalamic lesions. The probable mechanism is a diaschisis phenomenon involving thalamic tract disconnections.

Keywords: agraphia with alexia; diaschisis phenomenon; thalamic lesion; tract disconnection..

Figure 1

A dictation that was written by the patient before the injury.

Figure 2

Axial susceptibility-weighted image (A) discloses the old thalamic hemorrhage as diffuse hypointensity (arrow). Tractography obtained by placing seeds in the thalamus and the corresponding parietal lobe on each side, encompassing predominantly the posterior thalamic radiations, shows asymmetry, with decreased fibers on the left (dark orange) compared to the right (light purple) (B). Coronal T1-weighted inversion-recovery image (C) demonstrates the atrophy of the left mammillary body (arrow). 99mTc-HMPAO SPECT axial image (D) shows hypoperfusion in the left frontal and parietal cortices.

Figure 3

A) A note wrote by the patient 5 years before the lesion. B) The same words were dictated to the patient, showing her current impairment in writing.