MYELOGRAPHY and CNS Exams using MRI & CT

1. MYELOGRAPHY and CNS Exams using MRI & CT Spring 2009 (DRAFT)

2. Meninges • Membranes that enclose the brain and spinal cord • Dura Mater- outer layer • Arachnoid = middle layer • Pia mater = innermost layer • Subarachnoid space = wide space between arachnoid and pia mater

3. Subarachnoid space • Wide space between arachnoid and pia mater • Filled with CSF • Bathes brain & spinal cord with nutrients • Cushions against shocks and blows • Where contrast is injected for myelograms

4. CSF Information • Total adult CSF volume is 150 ml • 50% intracranial • 50% spinal • Adult opening pressure is normally 7-15 cm fluid • >18 abnormal • Young adults slightly higher <18-20

5. Spinal Cord Diameter • AP diameter is 7mm through C7 • C7 to conus medullaris is 6mm • At conus it is 7mm • Cord size is considered abnormal if it is over 8mm or under 6mm

6. Myelography • General term applied to the radiologic examination of the CNS structures situated in the vertebral canal • Requires contrast introduction into the subarachnoid space by spinal puncture • Puncture made at L2-L3 or L3-L4 space • May also be introduced into cisterna magna at C1 and occipital bone

7. Myelography • Contrast is generally water-soluble, nonionic, iodinated medium OMNIPAQUE ISOVUE

8. Contrast Precautions • Verify it is the correct contrast • Non-ionic iodinated contrast • Omnipaque or Isovue • Correct concentration • 180 and 300 common • Check expiration date • Keep contrast vial in room until procedure is complete

9. Puncture made at L2-L3 or L3-L4 space

10. Spinal needle injection

11. MYELOGRAM WITH CONTRAST

12. Room should be prepared by RT before patient arrival • Table and equipment cleaned • Footboard and shoulder supports attached • Radiographic equipment checked • Image intensifier locked to prevent accidental contact with sterile field or spinal needle • Tray setup FOOT BOARD SHOULDER PADS Hand grips

13. MYELOGRAM TRAY

14. Additional items • Blankets • Sterile towels • Sodium bicarbonate (if not in tray) • Non-ionic iodinated contrast media • Sterile gloves for DR • Shields for PT, DR, anyone else in room, and yourself • Varying sizes of spinal needles and needles • Extra syringes and tubing • Cleaning liquid

15. Syringes and Spinal Needles Syringes Spinal Needles (covered) More Spinal Needles (uncovered)

16. PRE- Procedure :Myelography • Premedication rarely needed • Patient should be well hydrated • Check orders, obtain history, labs results (if necessary), and previous exams • Informed consent: • Risks, benefits alternatives • Procedural details, including table movement and sensations should be explained, and get pt into a gown

17. Contraindications and Considerations • PT < 15.0 seconds • Preferable to reschedule exam if below 15 • Platelets >100,000 • If below 50,000 a platelet transfusion may be indicated before procedure • Heparin stopped 4 hours before • Can be restarted 2 hrs after procedure • Usually given as IP • Coumadin stopped 3-4 days before • Usually OP • Labs usually indicated

18. Radiation Safety • Have shields for PT’s, DR and yourself • Question LMP and the possibility of being pregnant • Use cardinal rules • Time • Distance • Shielding • ALARA • Use pulse if possible • Save the last image on screen when possible

19. Prone & Lateral Flexion • Prone • Pillow under abdomen for flexion of spine • Lateral flexion is not commonly used • Widens interspace for easier introduction of needle

20. Scout Images • Cross table lateral • With grid • Closely collimated

21. Myelography • Local anesthesia given at puncture site • Lidocaine and sodium bicarbonate • Spinal needle inserted (pressure obtained) • CSF usually withdrawn and sent to laboratory • Contrast injected and needle removed • 9-12 ml • Table angle and gravity used to move contrast under fluoroscopy • Spot images taken as needed

22. Spot Films • Central ray vertical or horizontal using CR or film screen cassettes • Images are taken at • Site of blockage • Level of distortion • If conus medullaris is area of concern: • Lay pt supine • Central ray at T12- L1 • Use 10x12 cassette and collimate tightly

23. Myelogram overview

24. Myelography • If contrast is moved into cervical area, head is positioned in acute extension to prevent contrast from entering ventricular system • Acute extension compresses cisterna magna and is the only position that will prevent contrast from entering ventricles

25. Myelography • Usually performed as outpatient basis • Common for CT myelography (CTM) to be used with conventional Myelogram • MRI often used instead • Myelography and CTM still used for patients with contraindications for MRI • Pacemakers and metal fusion rods

26. Post procedure: Myelography • Monitoring required • Head and shoulders elevated 30 to 45 degrees • Bed rest for several hours • Fluid encouraged • Puncture site checked before release

27. Vomiting Vertigo Neck Pain Spinal Headache Due to loss of CSF during puncture Increased severity upright Decreased pain when recumbent. Possible Complications from Myelography

28. More Severe Complications • Nerve root damage • Meningitis • Epidural abscess • Contrast reaction (anaphylactic shock) • CSF leak • Hemorrhage

29. Initial treatment Tylenol Horizontal position Forced fluids Caffeine Persistent headache If a fever occurs, contact MD May be indicative of meningitis Beyond 48 hrs w/o fever (24 hrs if severe) Blood patch Treatment for Spinal Headache

30. Blood Patch • Sterily injecting a small amount of patient’s blood into the epidural space • Clot will occur over hole • Usually will stop headache immediately • 1st patch is 70% effective • 2nd patch is 95% effective

31. Myelogram radiographs

32. Myelograms Images

33. CTM • Performed after intrathecal injection • Can be performed at any level of vertebral column • Multiple slices taken (1.5 – 3mm) • Gantry is tilted • Windowing allows for density and contrast changes • Can obtain images with small amounts of contrast • Can be done 4 hours after initial injection

34. CTM

35. MRI of Spinal Cord and CSF flow • Non-invasive • Provides anatomic detail of brain, spinal cord, intravertebral disc spaces, and CSF within subarachnoid space • Does not require intrathecal injection • Does not have bone artifacts

36. MRI basics • T1 & T2 images can be taken • Head coil for brain • Body coil and surface coil form spine • IV contrast can be used to enhance tumor • Gadolinium

37. Contraindications to MRI • Pacemakers • Ferromagnetic aneurysm clips • Metallic spinal fusion rods

38. Myelography Using MRI and Conventional methods MYELOGRAM

39. Preference of MRI • MRI is the preferred modality for middle and posterior cranial fossa of brain. • In CT these structures are obscured by bone artifacts • Spinal cord • Allows direct visualization of spinal cord, nerve roots, and surrounding CSF • Can be done in various planes • Aid in diagnosis and treatment of neurodisorders

40. Assessing demyelinating disease Such as MS Spinal cord compression Postradiation therapy changes of spinal cord tumors Herniated disks Congenital abnormalities of vertebral column Metastatic disease Paraspinal masses Usefulness of MRI

41. MRI and Brain imaging • Middle and posterior fossa abnormalities • Acoustic neuromas • Pituitary Tumors • Primary and metastatic neoplasms • Hydrocephalus • AVM’s • Brain atrophy

42. Not valuable for diagnosing: • Osseous bone abnormalities of skull • Intracerebral hematomas • Subarachnoid Hemorrhage • CT preferred for these 3 illnesses

43. CT of Brain basics • Useful for demonstrating size, location and configuration of mass lesions and surrounding edema • Assessing cerebral ventricle or cortical sulcus enlargement • Shifting of midline structures caused by mass lesions, cerebral edema, or hematoma

44. Indications for Pre and Post contrast Imaging using CT • Suspected Neoplasms • Suspected metastatic disease • Arteriovenous malformation (AVM) • Demyelinating disease (MS) • Seizure disorder • Bilateral isodense hematomas

45. Indications for Brain scans without Contrast media • Dementia • Craniocerebral trauma • Hydrocephalus • Acute infarcts • Post evacuation follow up of hematomas

46. CT Brain imaging • Most often Axial orientation • Gantry 20-25 degrees to OML • Allows lowest slice to provide an image of both the upper cervical, foramen magnum, and roof of orbit • 12-14 slices • 8-10 mm slices • 3-5 mm slices through post fossa • Depending of PT size • Slice thickness

47. CT Brain imaging (cont) • Coronal imaging • Helpful in evaluation of • Pituitary gland • Sella turcica • Facial bones • Sinuses

48. Modality of choice for the following” Hematomas Suspected aneurysms Ischemic or hemorrhagic strokes Acute infarcts Used as initial diagnostic modality for: Craniocerebral trauma CT: Modality of choice

49. CT of Spine • Useful in diagnosis of vertebral column hemangiomas and lumbar spine stenosis • Often used post-trauma to assess Axis and Atlas fractures and for better demonstration of C7-T1 • Clearly demonstrates size, number and locations of fracture fragments of C, T and L spine.

50. Surgery Applications of CT imaging • Greatly assists surgeons in distinguishing neural compression by soft tissue from compression by bone • Post-op • Useful in assessing outcome of surgical procedure