Neurologic Imaging

Brain Anatomy Gyri

(convolutions) = Elevations

Patient Education - Includes explaining:

* Need to keep head extended during exam * Local anesthetic used for comfort * Expect table to tilt during procedure * Head must be elevated 30-45 degrees after the procedure

Cross-table lateral cervical spine

- 1st image of choice if CNS involvement of neck is suspected - Shows fractures & misalignment - Must show C7-T1 - Upright lat C-S shows alignment

Single Photon Emission Computerized Tomography (SPECT)

- A nuclear medicine exam where 3-D images (axial, coronal, sagital images can be obtained using radionuclides & a computer.

Brainstem

- Aids in basic operations related to living breathing, swallowing - contains the 12 cranial nerves

Acquiduct of sylvius (cerebral acquiduct)

- Allows CSF to travel from the 3rd to 4th ventricle

Positron Emission Tomography (PET) used in cases of

- Alzheimer's - drug abuse - mental disease (schizophrenia) - seizures - tumors - many investigational studies

Medulla oblongata -

- Attaches the brainstem to the spinal cord - assists with basic autonomic functions controlling breathing and heart rate.

Spinal Cord Tumors

- Can be benign or malignant - Most are metastatic tumors, especially from bone cancer.

Midbrain (mesencephalon)

- Connects the cerebellum and cerebrum - aids in body movement - visual and auditory relay station

Pons -

- Connects the midbrain to the medulla oblongata. - assists with motor control and relays sensory information.

Cerebellum

- Coordinates voluntary movements, balance and posture

Magnetic Resonance Imaging shows:

- Demyelinating diseases - Tumors - Hydrocephalus - Arteriovenous malformations - Brain atrophy - Middle and posterior fossa of brain

Hydrocephalus

- Enlargement of the ventricles due to excess CSF. - 2 types

Meningitis Bacterial Symptoms

- Fever and chills - Nausea and vomiting - Sensitivity to light (Photophobia) - Severe headache - Stiff neck - Mental status change

Typical Contrast Agents for myelography include:

- Iohexol (Omnipaque) - Iopamidol (Isovue et. al) - Metrizamide (Amipaque)

Glioma

- Malignant tumor of CNS

dura mater ("hard mother")

- Outer layer to protect brain and spinal cord

Magnetic Resonance Angiography (MRA)

- Referred to as time-of-flight Use of a magnet and RF signal to image arteries and veins - better than conventional arteriography in demonstrating the carotids and circle of willis.

Degenerative Disk Disease

- Refers to a breakdown of the intervertebral disks

Skull Images

- Shows fractures, pathologic processes

CT Head Shows:

- Tumors - Demyelinating diseases (MS) - Hematomas - Dementia causes - Hydrocephalus - Infarcts - Aneurysms - Strokes

Arteriovenous malformations (AVMs)

- a snarled tangle of arteries and veins. - They are connected to each other, with no capillaries. - interferes with the blood circulation in an organ.

schwannoma

- benign nerve sheath tumor composed of schwann cells - schwann cells normally produce the insulating myelin sheath covering peripheral nerves.

Pituitary Adenoma

- benign tumor of the pituitary gland - interferes with production of the pituitary gland

Magnetic Resonance Imaging has excellent detail of

- brain, - spinal cord, - intervertebral disks - cerebrospinal fluid.

Astrocytomas

- cancer of the brain that originates in the astrocytes - occur in most parts of the brain and the spinal cord. - most common glioma - malignant

arachnoid layer

- delicate membrane

Ventricular shunt surgery

- divert CSF into another region of the body where it can be absorbed, such as the peritoneal (abdominal) cavity or into a vein just above the heart.

Meninges

- dura mater - subdural space - arachnoid layer - subarachnoid space - pia mater

subdural space

- extends below the spinal cord to the 2nd sacral segment

Hydrocephalus communicating

- free flow b/w the ventricles and subarachnoid space about the cauda equina. - Head is of normal size

Hydrocephalus Symptoms

- gait disturbance/imbalance - urinary frequency/incontinence - cognitive slowing/short term memory difficulty/dementia

Before the SPECT scan, you are injected with a chemical that is radiolabled, it emits

- gamma rays that can be detected by the scanner. - The computer collects the information emitted by the gamma rays and translates them into two-dimensional cross-sections. - These cross-sections can be added back together to form a 3D image of your brain.

pia mater ("tender mother")

- innermost layer (very vascular)

5. Trigeminal Nerve:

- largest cranial nerve - consists of ophthalmic, maxillary and mandibular nerves - facial sensation and chewing

Nerve sheath tumors

- made up primarily of the myelin surrounding nerves - May be malignant or benign

Glial cells

- maintain homeostasis, - form myelin, - provide support and protection for neurons in the brain

Conditions that can be discovered during a myelogram are

- meningitis, - West Nile virus, - herpes virus, - encephalitis - tumors or cancers of the nervous system - syphilis, - bleeding (hemorrhaging) - multiple sclerosis, - Guillain-Barr syndrome, - Early-onset Alzheimer's

subarachnoid space

- separates arachnoid and pia mater - myelogram injections occur here

Myelography visualizes the

- spinal cord, nerve roots and disk spaces - where spinal cord compression may result from herniated disks, tumors or bony fragments.

Spine Images

-Shows narrowed disk space, post-op changes & osteopetrosis/osteoporosis, compression fractures etc.

Stereotactic Surgery consists of

-a frame with localizers imaged with CT or MRI. -After localization, patient is taken to surgery where localizer is removed & a stereotactic guidance system is placed on the patient.

Single Photon Emission Computerized Tomography (SPECT) is used with

-with brain seizures, hemorrhagic strokes & ischemia diseases

Myelography Room prep:

1) Aseptic (Surgical Asepsis) necessary 2) Sterile tray and supplies 3) Lidocaine anesthetic 4) Table with shoulder support

Magnetic Resonance Imaging disadvantages

1) Cannot be used with ferromagnetic materials 2) Does not show bone as well as CT 3) Does not show bleeds as well as CT 4) More costly than CT

Three Primary Structures in the Brain

1) Cerebrum 2) Cerebellum (little brain) 3) Brainstem

The Myelogram Procedure

1) Injection is done in the prone, lateral or sitting upright position. 2) Needle is inserted and inner part of needle withdrawn to check for CSF return. 3) CSF withdrawn and sent for lab analysis 4) 9 - 12 ml of contrast injected 5) Table angled & contrast observed with fluoroscopic x-rays with patient prone & obliqued 6) Cross-table lateral obtained with a grid

The Spinal Cord Consists of:

1) Inner gray matter 2) Outer white matter

Myelography Most common sites of injection:

1) L3 - L4 interspace (most common) 2) L2 - L3 interspace 3) cisterna cerebellomedullaris

MRI Principles of Operation

1) Magnetic field lines up hydrogen protons parallel ) of magnetic field. 2) Radiofrequency pulse causes hydrogen protons to line up perpendicular to the magnetic field. - causes them to absorb energy & resonate at the RF frequency. 3) When the RF signal is stopped, the protons reorient parallel to the magnetic field and emit an electrical signal in the receiving antenna 4) The electrical signal is amplified into an MRI signal used by a computer to create sectional images

Myelography Patient Prep:

1) NPO for 8 hrs. 2) Well hydrated 3) No pre-medication necessary

Ventricles (four ventricles filled with CSF)

1) Two lateral ventricles 2) Third ventricle 3) Fourth ventricle

Lumbar Vertebrae

1) bigger than thoracic vertebrae 2) no rib articulations

Thoracic Vertebrae

1) have attachments for ribs 2) kyphotic curvature

computerized tomography myelography (CTM) Shows:

1) nerve root compressions 2) size, shape & position of spinal cord/nerve roots 3) dural tears - * must be done within 4 hrs of injection

Indications for Myelography

1)HNP 2) Tumors 3) Trauma to spinal cord 4) Stenosis of vertebral foramina 5) Bone Fragments

Parameters Effecting MRI Images:

1. Nuclear (proton) density 2) Relaxation rates 3) Flow - Moving substances

Myelography was first discovered in

1913

when was Air used for 1st time for myelography

1918

when was thorium dioxide (Thorotrast) used

1932

when were Oil-based agents used such as Pantopaque used

1940's - 1980's

when was Water-based iodinated contrast used

1980's - Today

what size needle is used for myelography

20 - 22 gauge needle.

How many pairs of spinal nerves are there?

31

Stereotactic Surgery

A 3-D guidance system used with CT or MRI to localize and biopsy or ablate tissue.

Myelography

A radiographic examination of the CNS structures within the vertebral column

Foramen of Monro (interventricular foramen)

An opening that allows CSF to travel from the lateral ventricles to the third ventricles

Zygoapophyseal (apophyseal) joints

Articulation between the superior and inferior articular processes.

C1

Atlas (has no body)

C2

Axis (has a dens for rotation)

Concussion

Blow to the skull resulting in a brief or prolonged loss of consciousness

Tomography

Compliments plain films (replaced by CT)

Cerebrum

Control of voluntary movements and mental activity

Pituitary gland -

Endocrine gland located in sella turcica

Pineal gland

Endocrine gland setting at the base of the 3rd ventricle in the midline. - function not well understood - calcifies in 35% of people and may indicate a shift in cerebra swelling

8. Vestibulocochlear Nerve:

Equilibrium and hearing

3. Oculomotor Nerve:

Eyeball and eyelid movement

What is the most common radionuclide used in a PET scan

Fluorodeoxyglucose (FDG)

Cervical Intervertebral foramina

For spinal nerves, exit at 45 degree angle to MSP.

Brain Anatomy Sulci

Furrows

Positron Emission Tomography (PET)

Injection of a proton rich nuclide to image physiologic activity of organs using a computer and gamma camera.

- Bulging disk

Irritation on the disk causes the nucleus pulposus to bulge into the annulus fibrosis

Most common site of herniation is

L4/L5 or L5/S1 due to load-bearing

Third ventricle - Located in

Midsaggital plane just below the ventricles

11 Accessory Nerve:

Movement of neck and shoulders

12 Hypoglossal Nerve:

Movement of tongue, swallowing, and speech

Commissures

Nerve fiber bands between cerebral hemispheres (ie., corpus collosum)

Positron Emission (Pair Production)

Positron (1.02 MeV) - splits into a .511 MeV photon and a .511 MeV photon

Choroid plexus

Present in all 4 ventricles

Longitudinal Sulcus -

Separates brain hemispheres

Fourth ventricle

Sits in the midline just anterior to the cerebellum

Spondylolithesis

Subluxation of one vertebra over another. - This most commonly occurs at L-5/S-1

9. Glossopharyngeal Nerve:

Swallowing, sense of taste, and saliva secretion

Ventricular shunt

The shunt is a soft tube that is just over 2mm (less than 1/8 inch) in diameter.

Radionuclide Brain Scans

Use of radionuclides to image the brain

- ruptured (herniated) disk

When an intervertebral disk protrudes out of place and causes pressure on the spinal nerve.

Menigioma

a benign tumor of the meninges

subdural hematoma

a slow, leaking type of venous hemmorhage between dura and arachnoid membrane

Seizure

a sudden, uncontrolled burst of electrical activity in the brain

epidural hematoma

accumulation of blood in temporal region as a result of middle meningeal artery

Lateral skulls shows

air/fluid levels in sphenoid sinuses (assoc. w/ basilar fxs.)

Spinal stenosis

an abnormal narrowing of the spinal canal or neural foramen that results in pressure on the spinal cord or nerve roots

Lumbar Vertebrae zygoapophyseal joints

angled 30 - 50 degrees to MSP (imaged in 45 degree obl.)

how does a computer create sectional images

based on energy transfer among and between hydrogen protons in tissue.

Hematoma

blood clot on the brain

Spondylosis

breakdown of the pars interarticularis

Spinal nerves below conus medullaris are called

cauda equina (horses tail)

A SPECT scan integrates two technologies to view your body such as:

computed tomography (CT) and a radioactive material (tracer). - The tracer is what allows doctors to see how blood flows to tissues and organs.

descending tracts of the spinal cord

deliver motor information to the periphery

Ascending tracts of the spinal cord

deliver sensory information to the brain

The purpose of a CSF analysis is to

diagnose medical disorders that affect the central nervous system

Thoracic Vertebrae zygoapohyseal joints

exit at 70-75 degree angle to the MSP (requires pt to be positioned at 20 degree angle from lateral to visualize)

4. Trochlear Nerve:

eye movement

6. Abducens Nerve

eye movement

7. Facial Nerve:

facial expressions, taste

Encephalitis

inflammation of the brain

Meningitis

inflammation of the meninges - can occur from bacteria or a virus.

where is contrast injected during a myelogram

into the subarachnoid space

what type of injection is a myelogram

intrathecal injection

pars interarticularis

lamina between superior and inferior articular processes

The Spinal Cord Extends from the

medulla oblongata to L1 - L2 (conus medullaris)

Brainstem consists of:

midbrain, pons, medulla oblongata

10 Vagus Nerve:

muscle sensory and motor control in throat, lungs, heart and digestive system

Myelography requires the use of what contrast

nonionic, water-soluble contrast media

Spin lattice (T1) relaxation

nuclei releasing energy to the general tissue environment.

Spin-spin (T2) relaxation

nuclei releasing energy among themselves

Degenerative Disk Disease symptoms

numbness, tingling, pain and muscle cramps

Hydrocephalus non-communicating

obstruction (usually tumor) between the ventricles and cauda equina.

Hematoma subdural

occurs in the subdural space below the dura mater.

Brain Anatomy Cortex

outer portion (gray matter)

Spinal stenosis symptoms

pain, numbness, or weakness in the arms or legs

Lumbar Vertebrae intervertebral foramina

perp. to MSP, best imaged in lateral position

Thoracic Vertebrae intervertebral foramina

perpendicular to MSP (seen on true lateral)

1. Olfactory Nerve:

sense of smell

Hematoma epidural

situated b/w the skull and brain

The RF signal rate can be varied & determines the

the T1 (fast) or T2 (slow) given to the image to bring out certain weight details

Relaxation rates are different for chemical environments in

various organs.

2. Optic Nerve:

vision

The Midbrain (mesencephalon) is associated with

vision, hearing, motor control, sleep/wake, arousal (alertness), and temperature

epidural hematoma often occurs due to

•blunt head trauma and recent skull fracture