Needle having multiple electrodes

Abstract

Embodiments of the invention generally relate to needles having more than one electrode and which are particularly suited for use in electromyography. One embodiment relates to a tripolar needle having three concentric electrodes. The tripolar needle is formed by providing a needle blank having first and second concentric electrodes and forming a third concentric electrode around the needle blank. The tripolar needle has an outer diameter which is substantially constant along the shaft of the needle, except at the tip, where the needle is sharpened.

1 . A method of forming a needle, comprising: 
 providing a needle blank having first and second concentric electrodes;    providing an insulation material around at least part of the needle blank;    providing a conductive material around at least part of the insulation material to form a third electrode; and    sharpening one end of the needle blank to form a sharpened tip portion of the needle.    
     
     
         2 . The method of  claim 1 , wherein the conductive material is plated or coated on the outside of the insulation material.  
     
     
         3 . The method of  claim 1 , wherein the conductive material comprises a conductive sheath of a substantially tubular form.  
     
     
         4 . The method of  claim 1 , further comprising the step of removing a portion of the second electrode before providing the insulation material.  
     
     
         5 . The method of  claim 1 , wherein the step of sharpening provides a substantially conical or frustoconical shape at the one end of the needle.  
     
     
         6 . The method of  claim 1 , wherein the step of sharpening provides a beveled tip shape at the one end of the needle.  
     
     
         7 . The method of  claim 1 , wherein the third electrode is formed along a shaft portion of the needle, proximally of the tip portion.  
     
     
         8 . The method of  claim 1 , wherein the needle is formed so that an outer diameter of the third electrode is substantially the same as an outermost diameter of the needle blank, which is substantially the same as an outermost diameter of the needle.  
     
     
         9 . A method of forming a needle, comprising: 
 providing a needle blank having first and second concentric electrodes;    providing a conductive material around at least part of the needle blank;    injecting an insulating material between the needle blank and the conductive material; and    sharpening one end of the needle blank to form a sharpened tip portion of the needle.    
     
     
         10 . The method of  claim 9 , wherein the conductive material comprises a conductive sheath of a substantially tubular form.  
     
     
         11 . A method of forming a needle, comprising: 
 providing a needle blank having first and second concentric electrodes;    forming an outer insulation layer around the needle blank;    forming a third concentric electrode around the outer insulation layer; and    sharpening one end of the needle blank to form a sharpened tip portion of the needle.    
     
     
         12 . The method of  claim 11 , further comprising the step of removing some of the outer insulation layer and some of the third electrode so that an outermost diameter of the needle is substantially constant along a shaft of the needle.  
     
     
         13 . The method of  claim 12 , wherein the outermost diameter of the needle is between 0.3 mm and 0.65 mm.  
     
     
         14 . The method of  claim 9 , wherein the third electrode is formed along a shaft portion of the needle, proximally of and adjacent to the tip portion.  
     
     
         15 . The method of  claim 12 , wherein the needle is formed so that an outer diameter of the third electrode is substantially the same as an outermost diameter of the needle blank, which is substantially the same as the outermost diameter of the needle.  
     
     
         16 . The method of  claim 9 , wherein the third electrode is plated or coated on the outside of the insulation layer.  
     
     
         17 . The method of  claim 9 , wherein the third electrode comprises a conductive sheath of a substantially tubular form.  
     
     
         18 . The method of  claim 12 , further comprising the step of removing a portion of the second electrode before forming the outer insulation layer.  
     
     
         19 . The method of  claim 11 , wherein the step of sharpening provides a beveled tip shape at the one end of the needle.  
     
     
         20 . The method of  claim 11 , wherein the step of sharpening provides a substantially conical or frustroconical tip shape at the one end of the needle.  
     
     
         21 . The method of  claim 20 , wherein the tip is sharpened so that the first and second electrodes have respective exposed portions on the tip separated by a substantially constant gap.  
     
     
         22 . A method of forming a needle, comprising the steps of: 
 providing a needle blank having first and second concentric electrodes, the first electrode being formed inwardly of the second electrode;    removing a portion of the second electrode along a shaft of the needle;    adding an insulation layer around the needle at least along the part of the shaft from which the portion of the second electrode was removed;    providing a conductive material to form a conductive layer around the insulation layer;    cutting excess added insulation material and conductive material from the needle so that an outer diameter of the needle is the same as an outer diameter of the needle blank, whereby a third concentric electrode is formed from the conductor layer at least partly along the portion of the shaft from which the portion of the second electrode was removed; and    sharpening one end of the needle blank to form a sharpened tip portion of the needle.