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The techniques and results of the main percutaneous procedures performed using image guidance with computerized tomography, including cordotomy, trigeminal tractotomy-nucleotomy, and extralemniscal myelotomy, are presented. The advantages of image guidance for anatomical orientation during the procedures and the newly designed radiofrequency needle-electrode systems are stressed.

We present a new radiofrequency needle electrode system for use in pain-relieving procedures. The electrode system is used for computed tomography-guided percutaneous cordotomy, extralemniscal myelotomy, and trigeminal tractotomy. These special electrodes make it possible to perform selective cordotomies and selective trigeminal tractotomies under direct computed tomographic image control.

Using a chronically implanted telemetric pressure sensor, we have determined the quantitative relationship between changes in body position and ventricular fluid pressure in normal subjects and subjects with shunts. The method allows accurate, reliable measurement of negative as well as positive pressures. We describe the derangement of postural intraventricular pressure regulation caused by placement of a shunt, as well as the influence of various shunt systems and the antisiphon device on this problem. Ventriculoatrial, ventriculoperitoneal, and ventriculopleural shunts all caused similar severely abnormal postural intracranial pressure relationships. The antisiphon device was generally effective in restoring normal pressures in patients in the upright position. We discuss the implications of our findings for understanding the mechanisms of postural intracranial pressure regulation in patients without hydrocephalus.

Using a chronically implanted telemetric pressure sensor, we have determined the quantitative relationship between changes in body position and ventricular fluid pressure in normal subjects and subjects with shunts. The method allows accurate, reliable measurement of negative as well as positive pressures. We describe the derangement of postural intraventricular pressure regulation caused by placement of a shunt, as well as the influence of various shunt systems and the antisiphon device on this problem. Ventriculoatrial, ventriculoperitoneal, and ventriculopleural shunts all caused similar severely abnormal postural intracranial pressure relationships. The antisiphon device was generally effective in restoring normal pressures in patients in the upright position. We discuss the implications of our findings for understanding the mechanisms of postural intracranial pressure regulation in patients without hydrocephalus.

Percutaneous stereotactic rhizotomy (PSR) as a method of treatment of trigeminal neuralgia has gained popularity in recent years as techniques of electrode placement and lesion production have improved. However, undesirable side effects including major and minor paresthesias, trigeminal motor root weakness, diplopia, and keratitis continue to occur even in cases where the neuralgia is treated successfully. In an attempt to improve treatment further, we have developed an electrode with a flexible curved tip for PSR of the trigeminal nerve. Once the electrode and the cannula are positioned in the retrogasserian portion of the trigeminal nerve with a standardized technique, manipulation of the electrode about its 360° axis readily enables an infinite variety of position adjustments of the electrode tip. This capability enables easier and more precise electrode placement and lesion production. Undesirable lesions of the motor root may be avoided. A curved electrode has been used in 150 patients. The incidence of masseter weakness is 7.3% in this series, compared to 24% in our series of 700 patients treated with a straight electrode. The incidence of undesirable paresthesias has decreased from 27% to 10.6%. The immediate results obtained in patients with the curved electrode have improved. Excellent results (no pain, no side effects) have been achieved in 88% of patients, in contrast to 76% treated with the straight electrode. Application of stereotactic principles and the use of the curved electrode have enhanced the appeal of PSR for the treatment of trigeminal neuralgia.

The history and physical principles of radiofrequency (rf) lesion making are reviewed. The advantages of the rf lesion method are presented, with emphasis on its importance in small, critical regions such as the dorsal root entry zone (DREZ). The evolution and specifications of a satisfactory DREZ rf electrode are described. DREZ lesion sizes for this electrode at specific electrode tip temperatures were experimentally determined in animals and were used as a guide to determine acceptable clinical lesioning parameters. Emphasis is placed on lesion temperature monitoring and on the stability of electrode penetration into the spinal cord to achieve consistent and safe results.

A stereotaxic guidance system has been used in conjunction with a conventional CT unit to biopsy 26 consecutive thoracic lesions. Accurate needle placement with a single manipulation occurred in 24 instances and two lesions required second passes. The technique provided adequate pathologic material with an acceptable complication rate. System advantages include the ability to approach lesions along oblique paths, controlled approach in difficult locations (mediastinal, peripheral, subscapular), capacity to biopsy small nonfluoroscopically visualized lesions, and increased speed over manual techniques.

This article describes a new body stereotaxic system that defines a fiducial point by means of a skin localization device placed directly on the patient. The system uses a rectilinear stereotaxic frame to guide the needles along the calculated path. A method for calculating paths that require angulations from one scan slice to another is described, as well. The system was tested in a foam phantom and shown to be intrinsically accurate in vitro to within 2 mm in both the x and y axis.