[The use of transcranial focused ultrasound in CNS diseases]

Transcranial focused ultrasound is a modern medical technique, which provides non-invasive impact on the brain. Current development stage of this technique is no longer than 20 years and many possible applications of this technique are still at pre-clinical stage. The greatest progress has been made in the field of functional neurosurgery. Focused ultrasound enables non-invasive MRI-guided formation of small destruction foci in the relevant targets, providing therapeutic neuromodulating effects in patients with Parkinson's disease, essential tremor, pain syndromes, obsessive-compulsive disorders, and other diseases. So far, this treatment was carried out in more than 300 patients. Several cases of ultrasound thermal destruction of intracranial neoplasms were published. There are attempts to perform third ventriculostomy using ultrasound in animals. A separate area focuses on the enhancement of the permeability of the blood-brain barrier to various substances driven by focused ultrasound. The possibilities of enhancing the permeability to chemotherapeutic agents, immune drugs, and other substances are being investigated in laboratories. A large number of studies focus on treatment of Alzheimer's disease. clinical trials aimed at enhancing the permeability of the blood-brain barrier to chemotherapeutic agents have been initiated. Reversible neuromodulating, stimulating, and inhibiting effect of focused ultrasound on the nervous system structures is another non-destructive effect, which is currently being actively investigated in animals. Furthermore, laboratory studies demonstrated the ability of focused ultrasound to destroy blood clots and thrombi. Transcranial focused ultrasound provides numerous unique possibilities for scientific and practical medicine. Large-scale research is required prior to the widespread clinical implementation. Nevertheless, we can already state that implementation of this technique will significantly enhance diagnostic and therapeutic potential of neurosurgery and neurology.

Subthalamic nucleus targeting using interpeduncular cistern as an internal landmark

BACKGROUND

Internal landmarks for the subthalamic nucleus (STN) have been used in past. This study uses a yet-unused internal landmark to refine STN targeting.

OBJECTIVE

To determine the effect of the width of the interpeduncular cistern (IPC) on STN targeting during placement of deep brain stimulation (DBS) for Parkinson disease.

METHODS

Fifty consecutive patients with Parkinson disease underwent 90 STN DBS implantations. X, Y, and Z coordinates for the tip of the DBS electrodes and the active contact were recorded. Internal landmarks such as width of the third ventricle, width of IPC at a predefined point, and anterior commissure-posterior commissure length were measured. Statistical analysis was done using linear regression analysis and Pearson correlation coefficient.

RESULTS

The average IPC diameter at the predefined point was 7.59 mm (range, 5- to 14 mm). Average X, Y, and Z coordinates for the location of the tip of lead were 11.5, -3.5, -5.4, and those of the location of active contact were 12.5, -1.9, -1.4 from the midcommissural point. The mediolateral location of the tip of the DBS as well as the location of the active contact for long-term stimulation were greatly dependent on IPC width (r = 0.83) (P = .0022).

CONCLUSION

The width of the IPC is a strong predictor of laterality of STN DBS electrode placement in patients with Parkinson disease. It can be used as an additional internal landmark for refining STN targeting using the simple formula X coordinate for STN target = 0.6 × IPC width + 7 mm.

A stereotactic near-infrared probe for localization during functional neurosurgical procedures: further experience

OBJECT

The authors previously developed an optical stereotactic probe employing near-infrared (NIR) spectroscopy to provide intraoperative localization by distinguishing gray matter from white matter. In the current study they extend and further validate this technology.

METHODS

Near-infrared probes were inserted 203 times during 138 procedures for movement disorders. Detailed validation with postoperative imaging was obtained for 121 of these procedures and with microelectrode recording (MER) for 30 procedures. Probes were constructed to interrogate tissue perpendicular to the probe path and to incorporate hollow channels for microelectrodes, deep brain stimulation (DBS) electrodes, and other payloads.

RESULTS

The NIR data were highly correlated to imaging and MER recordings for thalamic targets. The NIR data were highly sensitive but less specific relative to imaging for subthalamic targets, confirming the ability to detect the subthalamic nucleus and to provide warnings of inaccurate localization. The difference between the NIR- and MER-detected midpoints of the subthalamic nucleus along the chosen tracks was 1.1 +/- 1.2 mm (SD). Data obtained during insertion and withdrawal of the NIR probe suggested that DBS electrodes may push their targets ahead of their paths. There was one symptomatic morbidity. Detailed NIR data could be obtained from a 7-cm track in less than 10 minutes.

CONCLUSIONS

The NIR probe is a straightforward, quick, and robust tool for intraoperative localization during functional neurosurgery. Potential future applications include localization of targets for epilepsy and psychiatric disorders, and incorporation of NIR guidance into probes designed to convey various payloads.