various aspects of the invention will now be described with reference to the figures . for the purposes of illustration , components depicted in the figures are not necessarily drawn to scale . instead , emphasis is placed on highlighting the various contributions of the components to the functionality of various aspects of the invention . a number of possible alternative features are introduced during the course of this description . it is to be understood that , according to the knowledge and judgment of persons skilled in the art , such alternative features may be substituted in various combinations to arrive at different embodiments of the present invention . in particular , intracranial access systems ( ias ) 10 that can facilitate the movement of a larger diameter catheter through sections of a patient &# 39 ; s vasculature having a high curvature are described . in a first embodiment , as shown in fig3 , the intracranial access system 10 comprises a distal tip section 12 , an expanded section 14 and a proximal support section 16 . the ias may include a distal access catheter 18 . as described in greater detail below , a middle portion of the ias 14 b is of a diameter that fits into and supports a distal end 18 a of the dac . the ias will typically have a total length of about 2 m . the distal tip section 12 is generally a thin wire having a pre - formed or formable tip 12 d enabling intracranial access . the wire will have an appropriate atraumatic coating 12 e for intracranial use and will typically have an outer diameter a of 0 . 014 - 0 . 016 inch . the length b of distal tip section will be in range of 12 - 24 cm . the internal wire may extend the entire length of ias . the expanded section 14 provides a tapered transition from the narrower distal tip section 12 to the wider inner diameter c of a dac 18 . in the context of this description , a “ taper ” is generally referred to as a change in diameter from one section of the ias to another . that is , a taper implies a narrowing of diameter from a thicker region or a widening of diameter from a narrower region to a thicker region . the purpose of the expanded section is to prevent separation of the distal edge 18 a of the dac from the narrower distal tip section 12 as the distal region is being advanced and particularly as the distal region and dac are being moved through areas of high vascular curvature . as shown , the expanded section 14 includes a distal tapered section 14 a , a cylindrical central section 14 b and a proximal tapered section 14 c . the central section 14 b will have an outer diameter d generally corresponding to the inner diameter c of the distal end of the dac . as shown , the dac may also include a dac tapered section 18 b that transitions the dac from a narrower distal diameter c to a wider proximal diameter f . importantly , the ias ( namely the distal tip , expanded and proximal support sections ) and dac can move independently of each other . the ias is steerable . it would be expected that a skilled operator would advance the ias first and subsequently advance the dac over the ias . the configuration would be maintained in a way that generally the distal end of the dac would remain fixed in relation to expanded section 14 of the ias to allow for smooth transition . as can be seen , the central section 14 has a length g sufficiently long to enable this coaxial movement without causing the separation of the expanded section 14 from the distal inner diameter c of the dac . in practice , the central section with have a length g of approximately 8 cm . the total length of the expanded section 14 between the distal tip section 12 and proximal support section 16 will be about 12 - 15 cm . thus , each of the tapered sections 14 a and 14 c will be about 2 - 4 cm long . the outer diameter d of the central section 14 b will be approximately 0 . 058 inches and will be capable of moving through a curve having a 1 - 1 . 5 cm diameter . the central section 14 b is sufficiently strong in the radial direction while being bent to prevent separation of the dac distal end 18 a from the expanded section while moving around a tight curve . the central portion may have additional coating such as a hydrophilic coating to reduce friction . the central section 14 b and tapers may be a spiral wire and / or a plastic / rubber section having sufficient flexibility to enable bending and movement through a tight curve and sufficient radial strength to prevent separation as described above . in the case of a spiral wire , the central section may be formed from the same wire as the distal tip section or be a separate wire co - axially wound on an inner wire . in the case of a plastic / rubber section , the central section may be cast on an inner wire . in some embodiments , the central section and taper may be a combination of both coaxially wound wire and cast plastic / rubber . the proximal support section 16 will typically have an outer diameter h of about 0 . 035 inches and have sufficient axial compressive strength enable the distal tip section 12 to be pushed forward and sufficient torsional strength for turning of the distal tip section 12 . as shown in fig4 , in an alternate embodiment , the distal tip region 12 and proximal support region 16 can be additionally coaxially moved relative to the expanded section 14 . thus , in this embodiment , the expanded region 14 forms a cover over the proximal support region having a tapered region proximal support section 14 e that extends proximally and that enables the physician to independently slide these separate components relative to one another . in this embodiment expanded section 14 may be made of metal or polymers or a combination ( using technologies used in making wires and microcatheters and dacs ). as in the embodiment illustrated by fig3 , in this alternate embodiment , a dac may be preloaded onto the inner components . further , the underlying wire 12 a can be exchangeable so that if needed , once the distal access catheter is in place , the outer thicker part of the wire 12 a can be removed and the underlying thinner wire could still be used for stentriever purposes if needed . fig3 a shows an assembly of an ias with fig3 b , 3 c and 3 d showing an outer dac 18 , expanded section 14 and inner wire 12 a . as described above , the ias may be used to access an intracranial occlusion through a patient &# 39 ; s vasculature . generally , after the surgeon has gained access to the patient &# 39 ; s vasculature , the following general steps are followed : a . advancing an inner guide and support system having a distal tip region and an expanded section wherein the expanded section has a distal tapering surface connecting the distal tip region to the expanded section and wherein the expanded section proximal to the distal tapering surface has a cylindrical surface having an outer diameter greater than the diameter of the distal tip region through the patient &# 39 ; s vasculature together with a distal access catheter having a distal inner diameter substantially corresponding to the diameter of the cylindrical surface and wherein the distal access catheter can move coaxially relative to the cylindrical surface . b . manipulating the inner guide and support system and distal access catheter through the patient &# 39 ; s vasculature by a combination of torsional movements of the inner guide and support system and coaxial movements of the inner guide and support system relative to the distal access catheter to move the distal access catheter through regions of the patient &# 39 ; s vasculature having a high tortuosity . a . as noted , if the ias is preloaded into the distal access catheter , preparation time for surgery will be reduced . b . the system precludes the need for using a microcatheter or microwire thus saving money . c . if the clot can be successfully removed just by sucking through the distal access catheter , it would obviate the need for an expensive stent retriever . d . the ias system overcomes the current problem of distal access catheters getting caught in tortuous curves especially in older patients with atherosclerotic vessels . units of measure used in this specification are consistent with the units used in the field of endovascular surgery . that is , both imperial and metric units are used where lengths are typically expressed in metric units while diameters are expressed in imperial units . although the present invention has been described and illustrated with respect to preferred embodiments and preferred uses thereof , it is not to be so limited since modifications and changes can be made therein which are within the full , intended scope of the invention as understood by those skilled in the art .
the invention relates to systems and methods for intracranial vessel access . in particular , a system including a co - axial combination of a steerable variable thickness microwire operatively supporting a tapered larger bore support and larger bore distal access catheter is described . methods of advancing the intracranial access system through the vasculature are also described .