Neuro Imaging & Testing

Why is imaging important and what can it reveal?

-Identify the location and extent of brain injury

-Predict possible impairments and functional outcomes

-Guides therapy planning

-Informs precautions related to bleeding and swelling

-Assists in setting realistic expectations and goals

-Communication with the medical team

-Helps recognize complications that require referral (hydrocephalous, midline shift, herniation risk)

Why should PTs know different modalities of imaging and a basic level of interpretation?

Imaging and electrophysiological testing provides structural and functional information on the spatial and temporal characteristics of the neurological system. PTs should know the indications and limitations of these modalities.

What is structural imaging and what is included?

Structural imaging shows the physical anatomy of the body and includes:

Radiography

Computed Tomography (CT)

Non-Contrast CT (NCCT)

Contrast CT w/ Angiography (CTA)

Myelogram

Discography

Magnetic Resonance Imaging (MRI)

Diffusion-weighted Imaging (DW-MRI)

Diffusion Tensor Imaging (DTI)

What is radiography and what can it reveal?

Radiation is projected through the body and received by a radiographic detector.

Metal and bone radiopaque will present as white/light grey. Air and fat radiolucent will present as black or dark gray

Use: To detect significant fractures, dislocations, compromised joint space, and erosion (can provide some soft tissue but not prioritized)

Need more than one view to be an effective modality

What is Noncontract Computed Tomography and what can it reveal?

Uses X-rays but uses computerized reconstructions of cross-sections

Use: Provides rapid and enhanced images of cortical bone, soft-tissue, and vascular structures following trauma.

Initial imaging technique for TBI and hemorrhagic vs ischemic strokes but can miss small infarcts, Diffuse axonal injuries (DAI), and subtle early ischemia

Contrast improves sensitivity

Children susceptible to radiation related cancer

What are found in abnormal CTs of head trauma?

Hyperdense: The areas are brighter and can reveal intracerebellar hemorrhage and subarachnoid hemorrhage. Signals urgent intervention

Hypodense: The areas appear darker and indicate tissue loss or cytotoxic edema. Can correlate with poor effusion, mass effect (mass displacing other brain structures), and need for activity

What is Contrast CT w/ Angiography? (CTA)

CT w/ contrast to visualize extra intracranial vessels and requires adequate renal function.

Use: Diagnose possible CVA, brain tumor, aneurysm, or vascular malformation.

What is a Myelogram and what is it used for?

Contrast dye and X-rays or CT to look for problems in the spinal canal and used when MRI cannot be used safely.

Use: Can show a disc herniation and if its compressing nerve roots or the spinal cord. Can also rule out abnormalities of subarachnoid space, spinal nerve injury, herniated discs, fractures, back or leg pathology, and spinal tumors

Lumbar Puncture:A needle is inserted below L1-L2 (where spinal cord ends) to receive a sample of CSF.

Use: Rule out hemorrhage, inflammation, infection, meningitis, and tumors.

What is a spinal headache, symptoms, accompanied by, and treatment?

A dull throbbing pain that varies in intensity and typically gets worse when you sit up or stand and decreases when you lie down.

Accompanied by dizziness, tinnitus, hearing loss, blurred or double vision, photophobia, nausea and vomiting, neck pain and stiffness

Cause: spinal fluid leaks out of the puncture hole and results in low CSF. Brain sags downward and nerves become stretched.

Treatment: Blood patch (patch over dural hole), resting horizontally, caffeine, OTC pain meds, and fluids

What is a discography and use?

Evaluates integrity and pathology of the spinal disc and can be used with contrast dye. Use x-ray or CT to access after dye is placed.

Use: Identify discs that need to be treated or removed often prior to a surgery

What is MRI and what is it used for?

Has no radiation exposure and is more sensitive to early ischemia. However, takes longer (45 mins to 2 hours) and more expensive with contraindications for metal.

Use: Preferred method for cortical imaging and most PNS/CNS conditions. Differentiate complex hemorrhagic and ischemic strokes

How to interpret MRI findings?

Hypointense: darker areas that may reflect chronic bleeding, calcified lesions or scar tissue. Older and less reversible injury

Hyperintense: Brighter areas that suggest edema, infarct or demyelination, active pathology and possible early infarct.

What is Diffusion-weighted imaging (DW-MRI) and what are its uses?

MRI sequence for the evaluation of acute ischemic strokes and sensitive to small infarcts. Conventional MRI sequences (T1W, T2W) may not detect an infarct for 6 hours. Shows restricted diffusion

What is Diffusion Tensor Imaging and its use?

A microscopic level assessment of water diffusion rate and orientation in white matter tracts.

Use: See areas of axonal injuries not visualized in MRIs and TBIs

Red: Transverse

Green: Anterior-Posterior or Posterior-Anterior

Blue: Craniocaudal

What is functional imaging and what are the types?

Shows how a body part is working rather than only what the anatomy looks like

Types:

CT Perfusion

fMRI

What is CT Perfusion and what is it used for?

Differentiates salvageable ischemic brain tissue (penumbra) from the irrevocably damaged infarcted brain.

Use: Access a patient for treatment (thrombolysis or clot retrieval.

Patients with small infarct core and large penumbra benefit the most.

What is a Functional MRI (fMRI) and its use?

Indirectly measures neural activity, assessing changes in blood flow, volume and local rate of metabolism of oxygen.

Use: Perform an activity (wiggling tongue) which will cause a notable increase in metabolic activity in the areas of the brain responsible

Used in PT studies, pain science and neuroplasticity

What is Molecular Imaging and what are the types?

The type of functional imaging that shows biological activity at the cellular or molecular level

Types:

PET scan

Amyloid PET scan

What is a PET/Single Photon Emission Computerized Tomography and uses?

They help reveal the metabolic or biochemical function of the body’s tissues and organs. Uses a radioactive drug called a tracer to show both typical and atypical metabolic activity

Use: detect atypical metabolism of the tracer in diseases before the disease shows up on other imaging

What is an Amyloid PET Scan and what is it used for?

Used to define the pathological accumulation of amyloid-B (AB) plaques and tau neurofibrillary tangles which are consistent with Alzheimer’s Disease (AD)

What are electrophysiological techniques and what are the types?

Tests that measure the electrical activity of nerves, muscles, the brain and other organs.

Types:

Nerve Conduction Studies

Electroencephalogram (EEG)

Evoked Potentials

What are Nerve Conduction Studies?

A brief millisecond electrical pulse that is applied to the skin near a peripheral nerve. You may get an action potential or muscle contraction.

Use: Renervation status (prognosis), entrapments, neuropathies, and used if therapy producing poor results

What are the different types of NCS and what do they evaluate?

Sensory NCS: evaluates sensory nerve conduction and used for CTS and polyneuropathy

Motor NCS: evaluates motor nerve conduction and used for neuropathy and entrapment

F-wave: evaluates entire motor nerve length and used for radiculopathy and GBS

H-reflex: evaluates the reflex arc and used for radiculopathy and neuropathy

Needle EMG: evaluates muscle activity and denervation and used for radiculopathy, myopathy, and motor neuron disease

What is an EEG and what is its use?

Tool for diagnosing/monitoring epilepsy, seizures, and other neurological conditions.

Use: Identifies the source of the seizures and assess the severity of brain damage, and monitor brain activity

What are Evoked Potentials and what are they used for?

Two electrodes record the time it takes for an impulse to reach the brain, and external stimuli are used to evoke electrical potentials within the brain.

Use: Used to rule out MS, brain tumor, acoustic neuroma, and SCI