An implantable cuff electrode and / or optrode adapted to encircle substantially cylindrical body tissue, which is a self-sizing cuff, said implantable cuff electrode and / or optrode comprising: • a support sheet which is non-conductive, and ∘ having an inner surface and an outer surface separated from the inner surface by a thickness, ∘ having a perimeter inscribed in an inscribing rectangle of length measured parallel to a longitudinal axis, and of width measured parallel to a transverse axis normal to the longitudinal axis, the perimeter being defined by an inner edge and an outer edge extending along the length of the inscribing rectangle, and by a first and second lateral edges extending along the width of the inscribing rectangle, wherein ∘ the support sheet curls around and wraps the cylindrical tissue about the longitudinal axis with N > 1 loops, forming a cuff of substantially cylindrical geometry extending over the length, along the longitudinal axis, such that at least a portion of the inner surface forms an interior of the cuff, and such that at least a portion of the outer surface forms an exterior of the cuff, and such that an inner diameter of the substantially cylindrical geometry can vary with variations of a diameter of the substantially cylindrical body tissue encircled thereby, • at least a first energy transfer unit including an electrode contact or an optical contact, which is exposed at the inner surface of the cuff, Characterized in that, an inner handling flap is provided which comprises • a coupled end belonging to a coupled portion which is fixed to a portion of the outer surface of the support sheet which is adjacent to the inner edge, and • a free end, opposite the coupled end, belonging to a free portion adjacent to the coupled portion and separated therefrom by a transition line, said free portion being loose from the outer surface of the support sheet. • a support sheet which is non-conductive, and ∘ having an inner surface and an outer surface separated from the inner surface by a thickness, ∘ having a perimeter inscribed in an inscribing rectangle of length measured parallel to a longitudinal axis, and of width measured parallel to a transverse axis normal to the longitudinal axis, the perimeter being defined by an inner edge and an outer edge extending along the length of the inscribing rectangle, and by a first and second lateral edges extending along the width of the inscribing rectangle, wherein ∘ the support sheet curls around and wraps the cylindrical tissue about the longitudinal axis with N > 1 loops, forming a cuff of substantially cylindrical geometry extending over the length, along the longitudinal axis, such that at least a portion of the inner surface forms an interior of the cuff, and such that at least a portion of the outer surface forms an exterior of the cuff, and such that an inner diameter of the substantially cylindrical geometry can vary with variations of a diameter of the substantially cylindrical body tissue encircled thereby, ∘ having an inner surface and an outer surface separated from the inner surface by a thickness, ∘ having a perimeter inscribed in an inscribing rectangle of length measured parallel to a longitudinal axis, and of width measured parallel to a transverse axis normal to the longitudinal axis, the perimeter being defined by an inner edge and an outer edge extending along the length of the inscribing rectangle, and by a first and second lateral edges extending along the width of the inscribing rectangle, wherein ∘ the support sheet curls around and wraps the cylindrical tissue about the longitudinal axis with N > 1 loops, forming a cuff of substantially cylindrical geometry extending over the length, along the longitudinal axis, such that at least a portion of the inner surface forms an interior of the cuff, and such that at least a portion of the outer surface forms an exterior of the cuff, and such that an inner diameter of the substantially cylindrical geometry can vary with variations of a diameter of the substantially cylindrical body tissue encircled thereby, • at least a first energy transfer unit including an electrode contact or an optical contact, which is exposed at the inner surface of the cuff, • a coupled end belonging to a coupled portion which is fixed to a portion of the outer surface of the support sheet which is adjacent to the inner edge, and • a free end, opposite the coupled end, belonging to a free portion adjacent to the coupled portion and separated therefrom by a transition line, said free portion being loose from the outer surface of the support sheet.