Myelography 9/30/10 online ed.

Central nervous system 2 basic parts- What are they? Brain Spinal Cord

The Brain Composed of outer portion of gray matter called? Cortex Inner portion- white matter

The Brain Forebrain-largest part of brain know as? Cerebrum Midbrain Divided into lobes and lobules by sulci Midbrain Connects cerebrum to pons and cerebellum

Hindbrain Cerebellum-largest part of hind brain Pons Medulla oblongata

Prefrontal Cortex Area “scrambled” during lobotomy

Spinal Cord Continuous with medulla oblongata Extends from brain to approximately L2 Connected to 31 pairs of spinal nerves

The Meninges Layered coverings of brain and spinal cord Pia mater- inner sheath Highly vascular Arachnoid- central sheath Separated from pia mater by subarachnoid space Dura mater- outer sheath Outermost, protective layer

Ventricles- 4 fluid-filled cavities within the brain What is that fluid? Cerebral spinal fluid (CSF) Two upper pair are identical, known as left and right lateral ventricals 3rd Ventrical- just inferior to body of lateral ventricals 4th Ventrical located in hindbrain All ventricles communicate with each other through special connecting channels known as interventricular foramina

R and L Lateral Ventricles located in forebrain Body anterior horn posterior horn inferior horn

Ventricles cont’d Lateral ventricles 3rd ventricle 4th ventricle Superior Aspect

Pneumoencephalography Introduced in 1919 Performed extensively throughout late 20th century Cerebrospinal fluid -a small amount drained from around brain and replaced with air, oxygen, or helium as contrast to allow the structure of brain to show up more clearly on an X-ray Derived from cerebral ventriculography- air is injected through holes drilled in skull Pt turned upside down in special chair that can rotate vertically 360 degrees to get air to fill ventricals

Pneumoencephalography cont’d Extremely painful, very dangerous Test was generally not well tolerated by pts- headaches and severe vomiting common side effects Replacement of spinal fluid was by natural generation- took as long as 2-3 months MRI and CT have largely replaced Pneumoencephalography.

Myelography- Radiographic exam of spinal cord X-ray examination performed by radiologist to detect abnormalities of the spine, spinal cord, or surrounding structures Contrast material is injected into the fluid-filled space around spinal cord X-rays are taken

Myelogram cont’d Air used for early myelograms Injected via lumbar puncture In 1922, iodized poppy seed oil was used Accidentally discovered with no apparent side effects Nonionic, water-soluble compounds now used Demonstrates a low neurotoxicity CT and MRI now chiefly used to image nervous system

Myelography Injections can be given at: Cistern (below occipital bone -can be hazardous because the needle is inserted close to brain stem) Cervical spine Thoracic spine lumbar region (most common) Injection is in subarachnoid space –which is? (space between arachnoid and pia mater)

Myelography Indications Intraspinal abnormalities Nerve root abnormalities Disk prolapse (slipped disk), herniation Spondylosis- degenerative arthritis of spinal vertebra and related tissue Spondylolisthesis Spinal stenosis (spinal canal narrows and compresses spinal cord and nerves) Tumors Metastases

Myelography Contraindications Central aneurysms-(balloon-like bulge in an artery caused by weakening of artery wall) Arterio-venous malformations lumbar puncture within one week Previous reaction to contrast

Preliminary Radiographs Purpose Determine accurate bony anatomy To exclude pathologies that wouldn’t need myelography Distinguish congenital abnormalities For correlation with myelography, MRI and CT images when reporting

Preliminary Radiographs Lateral Both anterior oblique views to demonstrate pars interarticularis (neck of Scotty dog) Lateral L5-S1

Contrast Media Iohexol – Nonionic, water-soluble contrast Iotrolan (Isovist) – More recent contrast agent Less toxic than Iohexol

Procedure Sequence Prepare room, sterile trays, and contrast Pt placed prone on table Area to be punctured is cleaned and prepped with sterile towels Local anesthetic injected in area of puncture

Procedure Sequence (cont’d) Lumbar puncture needle inserted under fluoroscopic guidance until fluid appears CSF may be taken for analysis

Procedure Sequence (cont’d) Contrast material injected Flow monitored fluoroscopically Pt. tilted into trendelenberg and reverse-trendelenberg to control flow of contrast during spot films Overheads

Radiographs taken during exam: Generally, cross table lateral and PA Why not routine views? Pt has needle in spine Don’t want to change contrast position by rotating pt

Lumbar Myelogram PA Lateral

Myelography accuracy rate When compared with surgical findings: MRI – 96% Myelography – 81% CT – 57% CT and Myelography together - 84%

Cervical Myelogram

Set-Up for Lateral Cervical Film

Cervical Radiographs Overheads PA PA Oblique projections Cross-table lateral films

Alternative Radiographs Lateral flexion/extension Demonstrates: Stenosis spinal instablility deg. of movement of disk protrusion

Patient Care Concerns Maintain head in acute extension during examination! Bedrest 8 – 24 hours after procedure with head elevated Encourage hydration

Possible Post-Procedure Complications Headache Hypotension- which is? Low blood pressure Convulsions Confusion/hallucinations!

Advanced Imaging Techniques

Diskography Radiographic exam of intervertebral disks Contrast is injected directly into disk Determines disk morphology Reproduces pain caused by disk disease itself

Diskogram Films

CT Brain Scan Very accurate diagnosis of acute intracranial injuries Often 1st to evaluate head and spine trauma Very accurate diagnosis of acute intracranial injuries Contusions Hemorrhage Fracture evaluation

MRI (Magnetic Resonance Imaging) In brain for assessing: Middle and posterior cranial fossa abnormalities Acoustic neuromas Pituitary tumors Primary and metastatic neoplasms Hydrocephalus AVMs Brain atrophy

MRI In spine-for assessing: Demyelinating disease- (any condition resulting in damage to the protective covering (myelin sheath) that surrounds nerves in brain and spinal cord) Spinal cord compression Paraspinal masses Postradiation therapy changes in spinal cord tumors Metastatic disease Herniated disks Congenital anomalies