Review on Factors Affecting Diagnostic Yield in Stereotactic Biopsy for Brain Lesions: A 5-Year Single-Center Series.

Objective: To determine the factors that are associated with the diagnostic yield of stereotactic brain biopsy. Materials and Methods: A retrospective analysis was performed on 50 consecutive patients who underwent stereotactic brain biopsies in a single institute from 2014 to 2019. Variables including age, gender, lesion topography and characteristics, biopsy methods and surgeon’s experience were analyzed along with diagnostic rate. Results: This study included 31 male and 19 female patients with a mean age of 48.4 (range: 1-76). Of these, 25 underwent frameless brain-suite stereotactic biopsies, 15 were frameless portable Brain-lab® stereotactic biopsies and 10 were frame-based CRW® stereotactic biopsies. There was no statistical difference between the diagnostic yield of the three methods. The diagnostic yield in our series was 76%. Age, gender and biopsy methods had no impact on diagnostic yield. Periventricular and pineal lesion biopsies were significantly associated with negative diagnostic yield (p=0.01) whereas larger lesions were significantly associated with a positive yield (p=0.01) with the mean volume of lesions in the positive yield group (13.6cc) being higher than the negative yield group (7cc). The diagnostic yields seen between senior and junior neurosurgeons in the biopsy procedure were 95% and 63% respectively (p=0.02). Conclusion: Anatomical location of the lesion, volume of the lesion and experience of the surgeon have significant impacts on the diagnostic yield in stereotactic brain biopsy. There was no statistical difference between the diagnostic yield of the three methods, age, gender and depth of lesion.

Stroke Lesion Impact on Lower Limb Function

The impact of stroke on motor functioning is analyzed at different levels. ‘Impairment’ denotes the loss of basic characteristics of voluntary movement. ‘Activity limitation’ denotes the loss of normal capacity for independent execution of daily activities. Recovery from impairment is accomplished by ‘restitution’ and recovery from activity limitation is accomplished by the combined effect of ‘restitution’ and ‘compensation.’ We aimed to unravel the long-term effects of variation in lesion topography on motor impairment of the hemiparetic lower limb (HLL), and gait capacity as a measure of related activity limitation. Gait was assessed by the 3 m walk test (3MWT) in 67 first-event chronic stroke patients, at their homes. Enduring impairment of the HLL was assessed by the Fugl–Meyer Lower Extremity (FMA-LE) test. The impact of variation in lesion topography on HLL impairment and on walking was analyzed separately for left and right hemispheric damage (LHD, RHD) by voxel-based lesion-symptom mapping (VLSM). In the LHD group, HLL impairment tended to be affected by damage to the posterior limb of the internal capsule (PLIC). Walking capacity tended to be affected by a larger array of structures: PLIC and corona radiata, external capsule and caudate nucleus. In the RHD group, both HLL impairment and walking capacity were sensitive to damage in a much larger number of brain voxels. HLL impairment was affected by damage to the corona radiata, superior longitudinal fasciculus and insula. Walking was affected by damage to the same areas, plus the internal and external capsules, putamen, thalamus and parts of the perisylvian cortex. In both groups, voxel clusters have been found where damage affected FMA-LE and also 3MWT, along with voxels where damage affected only one of the measures (mainly 3MWT). In stroke, enduring ‘activity limitation’ is affected by damage to a much larger array of brain structures and voxels within specific structures, compared to enduring ‘impairment.’ Differences between the effects of left and right hemisphere damage are likely to reflect variation in motor-network organization and post-stroke re-organization related to hemispheric dominance. Further studies with larger sample size are required for the validation of these results.

Abstract WP90: Voxel-Based Lesion Symptom Mapping (VLSM) of NIH Stroke Scale Subscore Deficits

Background: Studies identifying brain regions required to preserve specific neurologic functions after stroke typically analyze infarct volume or location. Lesion topography studies have found that, independent of volume, involvement of specific regions have greater impact on clinical outcome than others, suggesting location-determined differences in eloquence. However, most anatomy-based studies define location broadly. VLSM is an imaging analysis technique that establishes a relationship between precise lesion location and clinical deficit. A group of patients with a symptom (e.g. aphasia) is analyzed; every voxel on each patient’s MRI is evaluated for lesion presence or absence. Each voxel is assigned a t-statistic, and a statistical map of all lesioned voxels is generated to pinpoint regions most strongly associated with the deficit; a high t-score indicates a lesion in that voxel has a significant effect on the specified symptom. We generated VLSM maps for 6 NIHSS subscores (aphasia, right- and left-limb weakness, and sensory loss) in a novel characterization to be used in future research. Methods: 172 acute ischemic stroke (AIS) patients with large vessel occlusions (LVOs) were analyzed. Binary masks of infarcts on D5 FLAIR sequences were created. Lesions were coregistered to standard MNI atlas space. VLSM V2.55 was used to generate statistical maps of lesion contribution to clinical deficit. Maps were thresholded to p<0.001 on basis of cluster size and permutation method. A symptom reference area was defined as a region on which voxels had a t-score >3.14. Results: VLSM maps with voxelwise thresholds of p<0.001 were generated for 6 NIHSS categories (examples in figure). Conclusions: VLSM successfully generated unique maps of 6 NIHSS subscore deficits. These maps will be used to study patients presenting with perfusion/diffusion mismatch to predict the potential for resolution of specific deficits with reperfusion therapy and aid in prognostication.

Foix-Chavany-Marie Syndrome due to Unilateral Anterior Opercular Damage with Contralateral Infarction of Corona Radiata

Foix-Chavany-Marie syndrome (FCMS) is a rare type of pseudobulbar palsy characterized by automatic-voluntary dissociation of movements of the face, tongue, pharynx, and masticatory muscles. Most cases are due to bilateral ischemic lesions of the anterior operculum, but the syndrome has also been described after unilateral opercular damage, either isolated or associated with contralateral cortico-nuclear tract involvement. We report a patient with FCMS due to right anterior opercular lesion with contralateral infarction of the corona radiata. The patient presented with paralysis of the face and tongue with automatic and voluntary dissociation. To our knowledge, FCMS with this peculiar lesion topography has rarely been reported. We discuss the underlying mechanism with reference to MRI and diffusion tensor imaging.