Brain retraction sensor

• US 6,916,294 B2
• Filed: 07/09/2002
• Issued: 07/12/2005
• Est. Priority Date: 07/09/2002
• Status: Active Grant

• Current Assignee: Michael Ayad
• Original Assignee: George Washington University
• Inventors: Ayad, Michael
• Primary Examiner(s): Hindenburg, Max F.
• Assistant Examiner(s): SZMAL, BRIAN SCOTT
• Application Number:
  US10/190,638
• Publication Number:
  US 20040010208A1
• Time in Patent Office: 1,099 Days
• Field of Search: 600/547, 600/587, 600/372, 600/300, 600/544
• US Class Current: 600/587
• CPC Class Codes: A61B 2562/0215 Silver or silver chloride containing
• CPC Class Codes: A61B 5/031 Intracranial pressure
• CPC Class Codes: A61B 5/291 for electroencephalography [EEG]
• CPC Class Codes: A61B 5/4076 Diagnosing or monitoring particular conditions of the nervous system A61B5/4821, A61B5/4824 take precedence

Abstract

An electrode grid device is disclosed comprising a deformable envelope, further comprising non-polarizable electrodes and a pressure recording port. The device is designed to allow for monitoring of brain retraction pressure and local cortical electrical activity including DC potential, as well as to redistribute the force applied during retraction and thereby diminish the chance of focal brain injury during surgery. Retraction pressure recorded is equal over the full area of contact, providing a more meaningful measurement than simply at one point on the retractor. A means is disclosed for evacuation of air from the system to improve accuracy and fidelity of the pressure measurements. It is a further aspect of the device to allow for measurement of intracranial pressure, DC potential and EEG in epileptic and severe head trauma patients for management of edema and injury, respectively.

Claims

1. A sub-dural sensor device comprising:

an elongated first end comprising a substantially inextensible cavity, wherein said first end is configured to be placed sub-durally;

a plurality of non-polarizable electrodes exposed along at least one surface of said first end,

and

an electric conduit and a hydraulic conduit comprising an exit port at a shortened second end, wherein said first end engages said second end at said exit port, and further wherein one end of said electric conduit and one end of a remote reference electrode electrically connect to a differential DC amplifier.

2. The device of claim 1, wherein said first end comprises substantially flat, smooth atraumatic faces.

3. The device of claim 1, wherein said first end comprises a thin, elastically deformable, bio-compatible material that conforms to contours of the brain.

4. The device of claim 1, wherein said electric conduit comprises at least one tail at an end distal to said first end, wherein said at least one tail allows for communications between the device and at least one peripheral apparatus.

5. The device of claim 1, wherein said cavity comprises a bladder or a network of interconnected lumens internal to a flat matrix.

6. The device of claim 1, wherein said hydraulic conduit comprises a flexible, noncompliant material having at least two lumenal surfaces.

7. The device of claim 6, wherein said hydraulic conduit comprises a double lumen catheter.

8. The device of claim 7, wherein one end of each separate lumeral surface comprising said double lumen catheter engages separate fluid-flow directing connectors.

9. The device of claim 8, wherein said fluid flow connectors are female luer-lock connectors.

10. The device of claim 9, wherein said connectors are affixed in a single unit.

11. The device of claim 1, wherein said cavity comprises a fluid selected from the group consisting of normal saline, buffered salt solution, Ringer'"'"'s solution, Elliott'"'"'s B solution, and mock cerebrospinal fluid.

12. The device of claim 1, wherein said first end can accommodate pressures of between about one mm Hg and about 120 mm Hg.

13. The device of claim 1, wherein the outer surface flanking the cavity of said elongated first end further comprises a plurality of perforations, wherein said perforations allow liquids to flow into a cistern or lumenal surface below said outer surface for the collection of residual fluids.

14. The device of claim 13, wherein said cistern or lumenal surface channels said residual fluids to one end of said elongated first end, wherein said cistern or lumenal surface engages a conduit, and further wherein said conduit engages an apparatus for collecting said fluid.

15. The device of claim 13, wherein said residual fluids are serosanguineous wound fluid or cerebral spinal fluid (CSF).

16. The device of claim 14, wherein said residual fluid flows into said apparatus by gravity flow.

17. The device of claim 14, wherein said apparatus is a bag.

18. The method of measuring intracranial pressure and cortical electrical activity comprising:

situating at least one device of claim 1 underneath the dura mater of the brain through at least one burr hole in the calvarium;

contacting said device on the surface of a brain; and

recording intracranial pressure and cortical DC potential and/or EEG.

19. The method of claim 18, wherein said measuring comprises application of said at least one device to a patient with intractable epilepsy, wherein placement of the device localizes focal seizures identified by EEG monitoring.

20. The method of claim 19, wherein said placement of the device allows for concurrent monitoring of intracranial pressure (ICP) and prompt administration of medicaments when ICP reaches critical values.

21. The method of claim 19, wherein said critical ICP is between about 20 and about 30 mm Hg.

22. The method of claim 19, wherein said measuring comprises application of said at least one device to a patient with severe closed head injury, wherein placement of the device is at the surface of the brain to permit assessment of swelling postoperatively.

23. A brain retractor sensor (BRS) device comprising:

an elongated first end comprising a substantially inextensible cavity;

a plurality of non-polarizable electrodes exposed along a front face of said first end;

at least one releasable coupling projection comprising a back face of said first end;

and

an electric conduit and a hydraulic conduit comprising an exit port at a shortened second end, wherein said first end engages said second end at said exit port, and further wherein one end of said electric conduit and one end of a remote reference electrode electrically connect to a differential DC amplifier.

24. The device of claim 23, wherein said first end comprises substantially flat, smooth atraumatic faces.

25. The device of claim 23, wherein said first end comprises a thin, elastically deformable, bio-compatible material that conforms to shaped angles of a retractor blade.

26. The device of claim 23, wherein said electric conduit further comprises at least one tail at an end distal to said first end, wherein said at least one tail allows for communication between the device and at least one peripheral apparatus.

27. The device of claim 23, wherein said projection is selected from the group consisting of a sleeve and a pocket.

28. The device of claim 25, wherein said cavity comprises a bladder or a network of interconnected lumens internal to a flat matrix.

29. The device of claim 25, wherein said bio-compatible material is selected from a group consisting of silicone-based materials, thermoplastic elastomer, low density polyethylene, and polyurethane.

30. The device of claim 23, wherein said hydraulic conduit comprises a flexible, noncompliant material having at least two lumenal surfaces.

31. The device of claim 30, wherein said hydraulic conduit comprises a double lumen catheter.

32. The device of claim 31, wherein one end of each separate luminal surface comprising said double lumen catheter engages separate fluid-flow directing connectors.

33. The device of claim 32, wherein said fluid flow connectors are female luer-lock connectors.

34. The device of claim 33, wherein said connectors are affixed in a single unit.

35. The device of claim 23, wherein said cavity comprises a fluid selected from the group consisting of normal saline, buffered salt solution, Ringer'"'"'s solution, Elliott'"'"'s B solution, and mock cerebrospinal fluid.

36. The device of claim 23, wherein said cavity can accommodate pressures of between about one mm Hg and about 120 mm Hg.

37. A method of averting brain injury during neuro-surgical retraction comprising:

a) situating the BRS of claim 23 between the brain and a retractor blade;

b) supplying a physiologically inert fluid throughout said elongated end;

c) recording retraction pressure and cortical electrical activity;

and

d) communicating to a surgeon performing said retraction abnormal recordings from step (c),

wherein said surgeon adjusts retractor position to avoid brain injury based on said abnormal recordings.

38. The method of claim 37, wherein said situating of the BRS comprises releasably coupling said BRS to said retractor blade.

39. The method of claim 38, wherein said releasably coupling comprises contacting said blade with a projection from a back surface of said BRS.

40. The method of claim 39, wherein said projection is selected from the group consisting of a sleeve and a pocket.

41. The method of claim 37, wherein said non-polarizable electrodes are selected from the group consisting of platinum and Ag—

AgCl.

42. The method of claim 37, wherein said physiologically inert fluid is selected from the group consisting of normal saline, buffered salt solution, Ringer'"'"'s solution, Elliott'"'"'s B solution, and mock cerebrospinal fluid.

43. The method of claim 37, wherein said recording in step (c) comprises referencing cortical DC potential at a remote site via a needle electrode.