Ideomotor Apraxia Due to Injury of the Superior Longitudinal Fasciculus

Does injury of the thalamocortical connection between the mediodorsal nucleus of the thalamus and the dorsolateral prefrontal cortex affect motor recovery after cerebral infarct?

We assessed the state of the thalamocortical connection between the mediodorsal nucleus (MD) and the dorsolateral prefrontal cortex (DLPFC) in patients with corona radiata infarct using diffusion tensor tractography (DTT). Altogether, 110 patients with corona radiata infarct were recruited, all of whom underwent DTT at an early stage following infarct onset. Based on the integrity of CST (CST+: CST was preserved around the infarct, CST-: CST was interrupted by the infarct) and the integrity of thalamocortical connection between the MD of thalamus and the DLPFC (DLPFC+: the connection was preserved, DLPFC-: the connection was interrupted), patients were divided into 4 groups: CST+/DLPFC+ (37 patients), CST+/DLPFC- (21 patients), CST-/DLPFC+ (25 patients), and CST-/DLPFC- (27 patients) groups. Motor function was evaluated using the upper Motricity Index (MI), lower MI, modified Brunnstrom classification, and the functional ambulation category at baseline and at 6 months post-onset. In patients with preserved CST integrity, the status of the thalamocortical connection had no impact on the assessed motor outcomes at 6 months post-stroke. However, in patients with disrupted CST integrity, those with preserved thalamocortical connection integrity had significantly higher motor function scores in all assessed outcomes 6 months post-stroke than those with disrupted thalamocortical connection integrity. The preservation or disruption of the thalamocortical connection between the MD of the thalamus and the DLPFC is an important factor for motor function recovery when CST integrity is also disrupted.

Prediction of Aphasia Severity in Patients with Stroke Using Diffusion Tensor Imaging

This study classified the severity of aphasia through the Western Aphasia Battery and determined the optimal cut-off value for each Language-Related White Matter fiber and their combinations, we further examined the correlations between Language-Related White Matter and Western Aphasia Battery subscores. This retrospective study recruited 64 patients with aphasia. Mild/moderate and severe aphasia were classified according to cut-off Aphasia Quotient score of 51 points. Diffusion tensor imaging and fractional anisotropy reconstructed Language-Related White Matter in multiple fasciculi. We determined the area under the covariate-adjusted receiver operating characteristic curve to evaluate the accuracy of predicting aphasia severity. The optimal fractional-anisotropy cut-off values for the individual fibers of the Language-Related White Matter and their combinations were determined. Their correlations with Western Aphasia Battery subscores were analyzed. The arcuate and superior longitudinal fasciculi showed fair accuracy, the inferior frontal occipital fasciculus poor accuracy, and their combinations fair accuracy. Correlations between Language-Related White Matter parameters and Western Aphasia Battery subscores were found between the arcuate, superior longitudinal, and inferior frontal occipital fasciculi and spontaneous speech, auditory verbal comprehension, repetition, and naming. Diffusion-tensor-imaging-based language-Related White Matter analysis may help predict the severity of language impairment in patients with aphasia following stroke.

Refining Surgical Corridors with Whole Brain Tractography: A Case Series

Recent advancements in automated diffusion tensor imaging (DTI) and whole brain tractography (WBT) may be of great use to the neurosurgeon in selecting surgical corridors that can minimize disruption of surrounding white matter tracts. This is especially important in cases where the lesion displaces white matter tracts and traditional operative approaches may inadvertently violate these fibers. Here, we present automated DTI seeding and WBT as a practical and efficient means for preoperative surgical planning, in an effort to spare white matter tracts that may be displaced by a variety of lesions and may be vulnerable during surgery. We retrospectively reviewed the records of seven patients with various intracranial lesions, who underwent preoperative magnetic resonance imaging (MRI) with automated DTI analysis. These images were used to guide operative planning so that we could select white matter corridors that would allow for minimal damage to vulnerable fiber tracts. The patients had various pathologies, ranging from neoplasms to intracranial hemorrhage, in a number of different intracranial locations. All the patients underwent preoperative intracranial imaging with post-processing of these images to generate white matter tracts. These images were then used to design an appropriate surgical approach that would minimize injury to white matter tracts. For the patients with neoplasms, all were totally or near-totally resected with a stability of symptoms postoperatively. In the case of the patient with intracranial hemorrhage, the hematoma was evacuated, with significant improvement in the postoperative period. Automated DTI seeding and WBT, which have become increasingly prevalent in recent years, can be of significant use to the neurosurgeon for preoperative planning. Their application is especially important in cases where white matter tracts are displaced by the lesion in question and are put at risk of injury during surgery. Using WBT to design customized surgical approaches appropriate to the case at hand can be of immense value in preserving these white matter tracts, minimizing postoperative deficits, and improving surgical outcomes. Further studies are needed to validate these results and better define their applicability to other regions and pathologies.