Apparatus and method for expanding a stimulation lead body in situ

Abstract

An implantable lead is provided with at least one extendable member to position therapy delivery elements, which may be electrodes or drug delivery ports, after the lead has been inserted into the body. The lead may formed as a resilient element which is contained in a retainer tube that may be removed to permit the lead to deploy. Alternatively, a non-resilient lead may be provided with a slotted retainer tube. A series of mechanical linkages for expanding and retracting the lead within the human body may be actuated with various mechanisms. A control system may be provided for closed-loop feedback control of the position of the extendable members. The invention also includes a method for expanding an implantable lead in situ.

1 . An implantable medical device fbr providing therapy to a body comprising:
 an elongate central portion;   at least one extendable member having a tip, the extendable member depending from the central portion and being adapted to assume a range of positions, including a compact position, in which the tip is disposed in close proximity to the central portion, and an extended position, in which the tip is disposed at a location distal from the central portion;   at least one therapy element disposed on the extendable member for delivering therapy to the body;   a linkage assembly for position adjustment of the extendable member in situ, the linkage assembly comprising a first strut and a second strut pivotally linked to one another at a first point, the first strut pivotally connected to a first actuator link at a second point, the second strut pivotally connected to a second actuator link at a third point, the second and third points moveable in relation to each other and cause the first point to move towards the second actuator link to compact the extendable member, and cause the first point to move away from the second actuator link to expand the extendable member;   wherein the extendable member is a span fastened to the linkage assembly, the span adapted to contract when the second point and the third point are moved away from each other, and expand when the second point and the third point are moved towards each other.   
     
     
         2 . The implantable medical device of  claim 1 , wherein the span comprises a folded stack when the span is in the compact position. 
     
     
         3 . The implantable medical device of  claim 1 , wherein the span is adapted to coil around the central portion when the span is in the compact position. 
     
     
         4 . The implantable medical device of  claim 1 , further comprising a sheath that surrounds the span when the extendable member is in the compact position. 
     
     
         5 . The implantable medical device of  claim 4 , wherein the sheath is removeable after the extendable member has been expanded to the extended position. 
     
     
         6 . The implantable medical device of  claim 1 , further comprising a locking mechanism to keep the extendable member at a constant position. 
     
     
         7 . The implantable medical device of  claim 6 , wherein the locking mechanism comprises a sheath compressed over the first link and the second link. 
     
     
         8 . The implantable medical device of  claim 1 , wherein the first actuator link and the second actuator link are adapted to move in a direction substantially parallel to an axis of the central portion. 
     
     
         9 . The implantable medical device of  claim 1 , further comprising a mechanism for adjusting the relative positions of the second point and the third point. 
     
     
         10 . An implantable medical device fbr providing therapy to a body comprising:
 an elongate central portion;   at least one extendable member having a tip, the extendable member depending from the central portion and being adapted to assume a range of positions, including a compact position, in which the tip is disposed in close proximity to the central portion, and an extended position, in which the tip is disposed at a location distal from the central portion;   at least one therapy element disposed on the extendable member for delivering therapy to the body;   a linkage assembly for position adjustment of the extendable member in situ, the linkage assembly comprising a first strut and a second strut, the first and second struts each having a first end, a second end, and a center between the respective first and second ends, the first strut and the second strut pivotally linked to one another at their respective first ends at a first point, a first link pivotally connected to the respective first ends of the first strut and the second strut at the first point, and a second link pivotally connected to the center of the first strut and the second strut at a second point, the first point and second point adapted to move away from each other to compact the extendable member, and move towards each other to expand the extendable member;   wherein the extendable member is a span fastened to the linkage assembly, the span adapted to contract when the first point and the second point are moved away from each other, and expand when the first point and the second point are moved towards each other.   
     
     
         11 . The implantable medical device of  claim 10 , wherein the span comprises a folded stack when the span is in the compact position. 
     
     
         12 . The implantable medical device of  claim 10 , wherein the span is adapted to coil around the central portion when the span is in the compact position. 
     
     
         13 . The implantable medical device of  claim 10 , further comprising a sheath that surrounds the span when the extendable member is in the compact position. 
     
     
         14 . The implantable medical device of  claim 13 , wherein the sheath is removeable after the extendable member has been expanded to the extended position. 
     
     
         15 . The implantable medical device of  claim 10 , further comprising a locking mechanism to keep the extendable member at a constant position. 
     
     
         16 . The implantable medical device of  claim 15 , wherein the locking mechanism comprises a sheath compressed over the first link and the second link. 
     
     
         17 . The implantable medical device of  claim 10 , wherein the first actuator link and the second actuator link are adapted to move in a direction substantially parallel to an axis of the central portion. 
     
     
         18 . The implantable medical device of  claim 10 , further comprising a mechanism for adjusting the relative positions of the first point and the second point. 
     
     
         19 . An implantable medical device for providing therapy to a body comprising:
 an elongate central portion;   at least one extendable member having an end, the extendable member depending from the central portion and being adapted to assume a range of positions, including a compact position, in which the end is disposed in close proximity to the central portion, and an extended position, in which the end is disposed at a location distal from the central portion, wherein the extendable member is formed as a series of telescoping elements;   at least one therapy element disposed on the extendable member for delivering therapy to the body;   a linkage assembly for position adjustment of the extendable member in situ, and   a mechanism for adjusting the relative positions of the extendable member and the central portion.