Neuroanatomy and Motor Control Quiz

The Brain

• Components: Cerebrum, Cerebellum, Brainstem.
• Lobes:
  • Parietal Lobe: Responsible for sensory perception.
  • Temporal Lobe: Influences emotions and memory.
  • Occipital Lobe: Primarily responsible for vision.
  • Frontal Lobe: Linked to personality, behavior, and motor control.

Stroke

• Clinical syndrome
  • Caused by abnormal cerebral blood circulation.
  • Leads to persistent neurological deficit.

Arteries

• Responsible for delivering blood to the brain.
• The brain requires oxygenated blood.
  • Internal carotid arteries (anterior):
    • Provide blood to the front of the brain.
  • Vertebral arteries (posterior):
    • Provide blood to the back of the brain.
• The two pathways function independently, ensuring blood supply even if one is compromised.

Mechanisms

• Ischemic stroke: Caused by a blockage of a blood vessel, interrupting blood flow.
• Hemorrhagic stroke: Caused by bleeding into the brain tissue.

Risk Factors

• Atherosclerosis: A condition characterized by the build-up of fatty plaques in the arteries.
  • Can result in ischemia or blockage of the arteries.

Ischemic Cascade

• Clot Stops Blood Supply:
  • Ischemia: Lack of blood flow to the brain.
  • Release of Excess Neurotransmitters: Neurotransmitters are released in large quantities due to lack of blood flow.
  • Disruption of Energy Metabolism: Increased energy demands that can't be met.
  • Increased Calcium Ions:
  • Formation of Substances that Damage the Brain: Release of harmful substances that further damage brain tissue.

Cerebral Thrombosis

• A blood clot that forms in a cerebral artery

Cerebral Embolism

• A blood clot that travels from elsewhere in the body to the brain

Hemorrhagic Cascade

• Primary Nontraumatic Cerebral Hemorrhage:
  • Atherosclerosis and Hypertension: Weakened blood vessels are unable to manage high blood pressure.
  • Increased Blood Pressure: Microaneurysms, small bulges in blood vessels, can rupture.
  • Microaneurysms/Arterial Necrosis:
    • Bleeding: Increased fluid in the space between brain and skull (intracranial pressure).
    • Adjacent brain tissue displaced: Leads to compression and ischemia.

Categories of Stroke

• Major stroke: Significant neurological impairment.
• Deteriorating stroke: Progressive worsening of symptoms.
• Yang stroke: A variant with a higher risk of death.
• Transient ischemic attack: Temporary blockage of blood flow to the brain, often a precursor to a major stroke.

Transient Ischemic Attacks (TIAs)

• Involve retinal or cerebral ischemia.
• Last less than 24 hours.
• Don't usually cause permanent brain damage though they are a predictor of future stroke risk.

Anterior Cerebral Artery Syndrome

• Cerebrovascular Accident (CVA) in the Anterior Cerebral Artery (ACA): Blockage of blood flow in the ACA.
  • Contralateral Hemiparesis: Weakness or paralysis on the opposite side of the body.
    • Primarily affects the lower extremity, especially the leg.
  • Contralateral Hemisensory: Loss of sensation on the opposite side of the body.
    • Primarily affects the lower extremity, especially the leg.

Anterior Cerebral Artery

• Supplies the medial frontal and parietal lobes.
  • Primary Motor Cortex: Responsible for voluntary movements.
  • Primary Sensory Cortex: Responsible for sensory perception.

Primary Sensory Cortex

• Receives sensory input from the opposite side of the body.

2 Pathways Sensory (Ascending)

• Posterior Column Pathway:
  • Second-order neurons cross to the opposite side of the brain in the medulla.
  • Responsible for transmitting proprioception (sense of body position) and fine touch.
• Anterior Column Pathway:
  • Sensory neurons cross to the contralateral side in the spinal cord.
  • Primarily responsible for transmission of pain, temperature, and pressure.

2 Pathways Motor (Descending)

• Anterior Corticospinal Tract:
  • Upper motor neurons (CNS) cross to the opposite side of the spinal cord.
  • Contribute to the control of voluntary movements of the trunk and proximal limbs.
• Lateral Corticospinal Tract:
  • Upper motor neurons cross to the opposite side in the medulla, then descend in the lateral white matter.
  • Primarily responsible for controlling voluntary movements of the limbs, especially fine movements of the hands.

Middle Cerebral Artery Syndrome

• Most common location for stroke blockage.
• Leads to cerebral edema and swelling.
• Contralateral Hemiparesis: Weakness on the opposite side of the body.
• Contralateral Sensory Loss: Loss of sensation on the opposite side of the body.
  • Affects the face and upper extremity more than the lower extremity.

Face and UE More Than LE

• The Middle Cerebral Artery supplies blood to the frontal, temporal, and parietal lobes.
  • These areas of the brain are responsible for controlling facial movements and voluntary movements of the upper extremity.

Frontal Lobe

• Contains the Primary Motor Cortex - responsible for voluntary movements.

Parietal Lobe

• Contains the Primary Sensory Cortex, responsible for sensory input from the opposite side of the body.

Aphasia

• Wernicke's Aphasia (left):
  • Receptive speech impairment.
  • Affects comprehension and language expression.
  • Associated with stroke damage posterior to the central fissure.
• Broca's Aphasia (left):
  • Expressive speech (motor) impairment.
  • Non-fluent aphasia, characterized by difficulties with word finding.
  • Stroke damage anterior to the central fissure.
  • Individuals struggle to express thoughts, with limited vocabulary.

Homonymous Hemianopia

• Visual field cut in half either on the left or the right side of both eyes.

Functional Independence Measure (FIM)

• Used to assess neurological damage in individuals with stroke.
• Measures functional skills and independence:
  • 1 = Total Assistance.
  • 7 = Complete Independence.

Posterior Association Areas

• These areas integrate incoming sensory information.
  • Somatosensory association area:
    • Integrating information from senses to make sense of touch, pressure, and temperature.
  • Visual association area:
    • Integrating information from visual input.
  • Auditory association area:
    • Integrating information from auditory input.

Perceptual Impairments

• Posterior Association Areas:
  • Lesion can cause agnosia.
  • Agnosia: Inability to recognize incoming sensory information.
    • Tactile Astereognosis: Difficulty identifying objects by touch.
    • Prosopagnosia: Difficulty recognizing people by their faces.
• Posterior Cerebral Artery:
  • Involved in memory processing.

Cognitive Impairments

• Executive Functioning: Enables purposeful behaviors.
  • MCA: Supplies the lateral frontal cortex.
  • ACA: Supplies the frontal cortex, including areas important for executive function.
• Prefrontal Cortex:
  • Lesion can impact executive functioning, potentially resulting in impulsivity and decreased judgment.
• Association Cortex:
  • Integrates sensory information from different sources, forming the basis for cognition.
    • Damage to visual association cortex leads to difficulty recognizing objects even though the person can still 'see' them.
    • Damage to the auditory association cortex can impact the processing and understanding of sound.
    • Lesions to the somatosensory association area can lead to attentional deficits for tactile and visual stimuli on the contralateral side of the body, as well as neglect syndrome.

Posterior Cerebral Arteries

• Supplies blood to the occipital, medial, and inferior temporal lobes.
  • Temporal Lobe Ischemia: Can lead to memory deficits, particularly amnesia.
  • Hypothalamus: Also supplies the hypothalamus, which is a key structure involved in memory.

Dysphagia

• Impaired swallowing: Difficulty swallowing.
• Patients with Medullary Brainstem Lesions:
• Vertebrobasilar Artery Syndrome:
  • Can manifest as dysphagia as this artery supplies cranial nerves involved in swallowing.

Pain

• Thalamic Nuclei: Responsible for regulating pain signals and transmitting them to the cortex.
• Posterior Cerebral Artery (PCA): Supplies the thalamus.
  • Stroke in PCA:
    • Central Post Stroke Pain Syndrome: Intense, spontaneous pain.
    • Hyperalgesia: Exaggerated pain in response to normal stimuli.
    • Allodynia: Pain in response to non-painful stimuli, such as touch.

Lacunar Stroke Syndromes

• Strokes in the small arteries that penetrate deep brain structures.
• Associated with: Diabetes and hypertension.

Symptoms

• Pure Motor Hemiplegia:
  • Paralysis or weakness on one side of the body.
  • Usually due to lesions in the pons or internal capsule.
• Pure Sensory Stroke:
  • Loss of sensation on one side of the body.
  • Usually due to lesions in the thalamus.
• Consciousness/Language Impairment: Higher-order cortical areas are typically spared in lacunar stroke.
• Faster Recovery is common as these strokes often involve smaller areas of brain tissue.

Paresis

• Weakness of voluntary movement:
  • Often resulting from upper motor neuron lesions (UMNS).
  • Increased Tone:
  • Non-antigravity Muscles Weakened:
    • Muscles responsible for specific movements.
  • Antigravity Muscles: Muscles that counteract gravity.
    • Increased Tone: Often leading to spasticity (increased resistance to movement).

Arms

• Flexed and Pronated:
  • Common after stroke due to the influence of the upper motor neuron system (CNS) on ascending pathways.

Legs

• Extended: After stroke, the legs will likely be extended due to the influence of UMN and descending pathways.

Hyperactive Reflex

• Increased reflex response:
  • Passive Stretch:
    • Occurs due to lesions affecting lower motor neurons (LMNS) and their influence on the ventral spinal cord (VSC).

UMNL

• Lesions affecting the upper motor neuron pathway above the anterior horn of the spinal cord:
  • Impacts the UMN, often leading to spasticity and weakness.

Direct Motor Control

• Corticospinal Tract:
  • Responsible for precise voluntary movements.
    • Upper Motor Neuron (UMN): - Collateral motor neurons:
      - Impart signals to the brainstem. - Influences motor nuclei.
    • Pathway Starts at Cerebral Cortex:
    • Terminates at Lower Motor Neurons: In the spinal cord. - Influences distal extremity muscles.
  • Lateral Corticospinal Tract: Primarily controls limb movements.
  • Anterior Corticospinal Tract: Primarily controls proximal muscles (trunk).

Indirect Motor Control:

• Corticospinal Tract:
  • Influences UMN innervating distal extremity muscles (specifically fingers and feet).
• Medullary Control Brainstem Motor Centers:
  • This pathway is influenced by collateral motor neurons, regulating tone and movement.

Spasticity

• Increased muscle tone.
• Impacts Movement: Difficult to move normally.

Rate Dependent

• The faster the movement, the greater the resistance (spasticity)

Hypertonicity

• Increased resistance to passive movement.

Rigidity

• Another type of hypertonicity, but not rate-dependent.
• Consistent resistance throughout the entire range of motion.
• Often associated with basal ganglia disorders.

Knee Jerk Reflex

• Tendon Tapped:
  • Stimulus creates a stretch in the muscle.
• Stretch Recognized by Receptors:
  • Sensory receptors send signals to the spinal cord.
• Spinal Cord Connects:
  • The spinal cord synapses with motor neurons.
• Motor Neurons Signal Muscle:
  • The muscle contracts.
• Lower Leg Extension:
  • Results in a kick forward.

Characteristics of Spasticity

• Resistance to Passive Movement: The faster the joint is moved, the greater the resistance felt.
• "Clasp-Knife" Phenomenon: Significant resistance, followed by a sudden letting go.

Stiffness

• Increased Muscle Tone
• Hyperactive Stretch Reflex: Overactive reflex response to stretching.

Rigidity

• Consistent hypertonicity that is not rate-dependent.
• Resistance to passive movement is unchanged throughout the range of motion.
• Often associated with basal ganglia disorders.

Motor Impairment Stroke Sequence

• Flaccidity: (Immediately after stroke):
  • Hypotonicity: (Short-lived): Flaccid paralysis, usually lasting several days.
  • Immediately After Stroke Due to Cerebral Shock: The brain is temporarily unable to regulate motor output.
• Spasticity:
  • Develops in Majority: Begins to set in days or weeks following stroke.
  • Abnormal Limb Synergies: Difficulty isolating muscle movements, limbs move in patterns.
• Relative Recovery:
  • Some Voluntary Control of Synergies:
  • Spasticity Declines:
  • More Control Over Challenging Movements:

Abnormal Muscle Synergies

• Inability to Move One Part of a Limb Without Moving Other Parts: Movement becomes coupled and less independent.

Review of Anatomical Terms

• Shoulder:
  • Flexion: Lifting the arm forward.
  • Extension: Moving the arm backward.
  • Abduction: Moving the arm away from the body.
  • Adduction: Moving the arm toward the body.
  • External Rotation: Rotating the arm outward.
  • Internal Rotation: Rotating the arm inward.
  • Protraction: Moving the shoulder blade forward.
  • Retraction: Moving the shoulder blade backward.
• Elbow:
  • Flexion: Bending the elbow.
  • Extension: Straightening the elbow.
  • Pronation: Rotating the forearm so the palm faces down.
  • Supination: Rotating the forearm so the palm faces up.
• Wrist:
  • Flexion: Bending the wrist.
  • Extension: Straightening the wrist.
  • Ulnar Deviation: Moving the wrist toward the little finger (pinky).
• Radial Deviation: Moving the wrist toward the thumb.
• Hip:
  • Flexion: Bending the hip.
  • Extension: Straightening the hip.
  • Abduction: Moving the leg out to the side.
  • Adduction: Moving the leg towards the midline.
  • External Rotation: Rotating the leg outward.
  • Internal Rotation: Rotating the leg inwards.
• Knee:
  • Flexion: Bending the knee.
  • Extension: Straightening the knee.
• Ankle:
  • Plantarflexion: Pointing the toes down.
  • Dorsiflexion: Pointing the toes up.
  • Inversion: Lifting the medially edge of the foot (toward the midline).
  • Eversion: Lifting the lateral edge of the foot (away from the midline).

Abnormal Synergy Patterns (LE)

• Flexion Synergy:
  • Everything flexed (UE).
  • Hip: Flexion, abduction, and external rotation.
  • Knee: Flexion.
  • Ankle: Dorsiflexion.
  • Toes: Dorsiflexion.
• Extension Synergy:
  • Hip: Extension, adduction, internal rotation.
  • Knee: Extension.
  • Ankle: Plantarflexion.
  • Toes: Plantarflexion.

Abnormal Synergy Patterns (UE)

• Flexion Synergy:
  • Scapular Retraction: Shoulder blades pulled backward.
  • Shoulder: Abduction and external rotation.
  • Elbow: Flexion.
  • Forearm: Supination.
  • Wrist and Fingers: Flexion.
• Extension Synergy:
  • Scapular Protraction: Shoulder blades moved forward.
  • Shoulder: Forward.
  • Arm Rotates: Inward.