In neurosurgery, trajectory often refers to the path or approach taken to access a target area in the brain or spinal cord during a surgical procedure. This term is crucial for ensuring precision and minimizing damage to surrounding tissues. Below are some key aspects of trajectory planning in neurosurgery:

### 1. Key Components of Trajectory Planning

1. Entry Point: The site on the skull, spine, or other anatomical location where the surgeon begins the approach.
2. Target Point: The specific area of interest (e.g., tumor, aneurysm, or lesion) that needs to be accessed.
3. Angle and Pathway: The route taken between the entry and target points, designed to avoid critical structures like blood vessels, functional brain areas, and cranial nerves.

### 2. Techniques for Planning

1. Neuronavigation Systems: These technologies use imaging (MRI, CT) to create a 3D map, allowing surgeons to plan and monitor trajectories in real time.
2. Stealth Guidance: Real-time feedback from systems like Medtronic's StealthStation ensures precise alignment with the planned trajectory.
3. Minimally Invasive Approaches: For surgeries such as endoscopic or stereotactic procedures, smaller entry points and shorter trajectories are prioritized.

### 3. Applications in Neurosurgery

1. Tumor Resection: The trajectory is chosen to maximize access to the tumor while preserving healthy tissue.
2. Deep Brain Stimulation (DBS): Electrodes are precisely implanted into deep brain structures like the subthalamic nucleus.
3. Stereotactic Biopsies: Precise trajectories allow small tissue samples to be taken from deep or sensitive areas safely.
4. Spinal Surgery: Trajectory planning is vital for pedicle screw placement and decompressive procedures.

### 4. Factors Influencing Trajectory Choice

1. Patient Anatomy: Individual variations in anatomy must be accounted for.
2. Lesion Characteristics: Size, location, and type of lesion guide trajectory decisions.
3. Surgical Goals: Priorities such as extent of resection, functional preservation, and cosmetic considerations.

### 5. Emerging Innovations

1. Robotic Assistance: Robots like the ROSA system enhance trajectory precision, particularly for complex cases.
2. Augmented Reality (AR): AR overlays anatomical and trajectory data onto the surgical field, aiding decision-making.
3. Artificial Intelligence (AI): AI algorithms help predict optimal trajectories and outcomes based on patient-specific data.