SHS 485: methods for investigating speech/language disorders & etiologies of acquired speech disorders

Four main causes of acquired language disorders

1. Stroke

2. Trauma

3. Tumor

4. Degenerative disease (ie: Alzheimer’s, Parkinson’s, Huntington’s)

Note: The more focal the lesion, the more specific the behavioral deficit

What is a stroke (and a Transient Ischemic Attack)? What are the 2 types?

Definition:

• Disruption of blood flow to the brain

  • Ie) Transient Ischemic Attack (TIA): ministroke. Leads to specific neurological deficits that resolve within 24 hrs.

Types

• Ischemic: blockage of blood flow in artery

  • ie) Cerebral infarction (fat breaks off to clog artery)

    • “Brain block”

• Hemorrhagic: rupture of artery

  • Aneurysm: bulging artery that may lead to rupture/bleed

    • “Brain bleed”

What is the leading cause of serious long-term disability in the U.S.? Statistics?

Stroke

• ~795,000 ppl effected per year

• 60% non-comatose stroke survivors suffer some kind speech/lang impairment

What causes a TBI? 2 types (with examples)?

Definition:

• Injury caused by blow to the head or violent head movement

  • Note: “TBI” label only applied when evidence of total/partial functional/psychological disability.

Types

• Open Head Injury: Focal injury. Penetrating wound, (i.e. skull is opened/cracked)

• Closed Head Injury: Diffuse injury. skull remains intact, but brain is damaged due to:

  • Compression

  • Stretching

  • Shearing (Tearing)

What is a Tumor? 2 most common types?

Definition:

• Abnormal tissue growth

Types:

• Gliomas: develop from glial (support) cells

• Meningiomas: develop in the meninges (3 membrane layers protecting brain and spinal cord)

3 ways tumors cause language deficits?

• Compression

• Disrupting blood flow to healthy cells

  • Subsequently, Tumor resection may need to include removal of some healthy tissue

2 types of degenerative diseases? 4 examples of diseases?

2 types

• Progressive OR Diffuse

4 Examples

• Parkinson’s

• Alzheimer’s

• Dementia (several types)

• Primary Progressive Aphasia - widespread diffuse aphasia. Damage to communication functions.

3 major neurological methods for investigating speech/lang disorders? Used for?

Methods

• Highly Invasive Techniques (neurosurgical methods)

• Slightly less invasive techniques (more minor surgical procedures)

• Non-Invasive techniques (brain imaging)

Use

• Understand underlying neuro-biological cause of deficits (guides treatment approaches)

• Determine effects of possible (neurosurgical) treatments

Give (2) examples for highly invasive techniques for determining brain region functions). How do they work and what are they used for?

Direct Cortical Stimulation

• Mechanics

  • Pulls open meninges, Delivers small electric current on cortical surface. —> Temporarily disrupts/facilitates functions in the specific cortex it stimulates

• Use

  • Presurgical mapping of function (to avoid hitting critical regions during tissue resection)

Implanted Electrode Grids

• Mechanics

  • Measures electrical signals correlated with neuron activity

• Use

  • Identify abnormal/ missing signals during tasks the patient performs

Give (2) examples for invasive techniques for determining brain region functions). How do they work and what are they used for?

Wada Procedure

• Mechanics

  • Injects sodium amytal into one carotid artery + then the other. Puts respective hemisphere to sleep (5-10min)

• Use

  • Allows neurologists to assess function in the awake side.

Brain Angiogram

• Mechanics

  • Inject dye to highlight arteries in brain.

• Use

  • Shows any damage or occlusion in arteries (usually after a stroke)

Give (2) examples for non-invasive techniques for determining brain region functions). How do they work and what are they used for?

Brain imaging

• Electromagnetic (related to electrical activity)

  • Electroencephalography (EEG)

    • Mechanics: Electrodes on scalp measure total electrical activity of large amts of active neurons

    • Use: Looks at changes in brain activity in response to mental activity + language tasks

• Hemodynamic (related to blood flow)

  • Magnetic Resonance Imaging (MRI)

    • Mechanics: Highlights different tissue types based on density. Uses constant radio waves and magnets to view a captured image of the inside of the body (the cylinder youre put in that spins)

      • Another example —> computed tomography scan (CT) scan: 360 xray view of brain

    • Use: Takes high resolution picture (structural brain image)

  • Functional magnetic resonance imaging (fMRI)

    • Mechanics: measures regional changes in blood flow based on oxygen concentration.

      • Another example —> PET scans: uses radioactive substances known as radiotracers to visualize and measure changes in metabolic processes, and in other physiological activities including blood flow, regional chemical composition, and absorption

    • Use: Takes structural brain image

Transcranial Magnetic Stimulation: What does it do? What can it be used for? Why could it be useful to study language function?

Method for producing…

• if strong magnetic field —> producing temporary focal brain “lesion” (disruption)

• if milder field —> produces “excitation” (facilitation)effects.

Use

• procedure that uses magnetic fields to stimulate nerve cells in the brain to improve symptoms of major depression

Middle Cerebral artery: feed most of cortex (parietal, frontal, temporal). Stroke occurs in this artery.