Introduction: Based on numerous preclinical studies and a few successful case reports, the nucleus basalis of Meynert (NBM) has drawn attention as a potential target for neuromodulation in degenerative dementia disorders. The NBM has a clear role in cognition, including attention, arousal, memory, and perception. The loss of cholinergic neurons in this nucleus directly correlates with the level of cognitive impairment in both Parkinson’s disease (PD) dementia and Alzheimer’s disease.
The NBM is a thin flat irregular structure in the axial plane of the basal forebrain. The diffuse NBM projections originate from MRI-invisible subnuclei that are “subspecialized” to serve certain domains of cognition. The detailed diffusion tensor imaging (DTI) maps of NBM subnuclear connectivity, that are necessary for DBS targeting, are currently unavailable. Our pilot study was designed to help address this challenge in preparation for the investigation of the effects of NBM deep brain stimulation (DBS) for the treatment of PD dementia.
Methods: We studied the diffusion-weighted MR of 9 patients who underwent DBS surgery for PD. We divided NBM area into 15 segments with 4 mm diameter each and DTI seedings were done from each segment. The projections were quantified by their volume and fractional anisotropy index. A probability map for different types of projections was created and the resultant patterns were analyzed and correlated with dementia rating scores.
Results: We developed the reproducible methodology to visualize strong parieto-occipital, frontal, and temporal projections of NBM. The lack of consistent forniceal and cingulate projections can be attributed to the limitations of deterministic DTI tractography. Several patterns in the NBM DTI probability map were recognized and are presented.
Conclusions: Our study illustrates, that DTI, at its current stage, is not a perfect but still a powerful and practical tool for fine tuning the coordinates of complex novel neuromodulation targets.
Patient Care: Understanding of patient’s NBM subnuclear connectivity will help to refine the coordinates of complex novel neuromodulation target.
Learning Objectives: By the conclusion of this session, participants should be able to: 1) Describe the neurosurgical role in the management of cognitive disorders associated with Parkinson’s disease; 2) Discuss, in small groups, the surgical and projectional anatomy of NBM region; 3) Identify the strengths and drawbacks of DTI as a surgical tool.
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