Stereotactic neurosurgery is founded on the ability to accurately localize and safely access targets within the brain in a minimally-invasive manner. The stereotactic method was first described in 1908 by Sir Victor Horsley and Robert Clarke at University College London, where they developed an apparatus for animal experimentation that allowed them to establish a threedimensional Cartesian coordinate system for targeting. At that time, however, x-rays were the only available form of imaging the human body and as such, localizing intracranial targets relied on a combination of knowledge from anatomical atlases and the visualization of a few intracranial landmarks such as the pineal gland or the foramen of Monroe. These landmarks could be visualized by filling the ventricles with air (pneumoencephalogram) or a contrast medium (ventriculogram) [Figure 1]. In 1947, Ernst Spiegel and Henry Wycis created the first human stereotactic frame that allowed for lesioning of deep brain nuclei for the treatment of psychiatric disease.2

With imaging limited to x-rays alone, a need arose for another means of confirming the appropriate location where a lesion would be made or an electrode would be implanted. Nicholas Wetzel and Ray S. Snider have been accredited with performing the first microelectrode recording (MER) in humans in 1958 during a pallidotomy.3 Over time, particularly with the popularization of thalamotomy for the treatment of Parkinson’s disease and with a growing appreciation of characteristic recordings of specific nuclei, MER became commonplace in stereotactic neurosurgery.

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