5. Brainstem and Cerebellum

What are the 4 D’s of brainstem dysfunction?

• Dysphagia

• Dysarthria

• Diplopia

• Dysmetria

What is dysphagia?

Impaired swallowing

What are signs of dysphagia from brainstem dysfunction?

• Coughing or choking with eating or drinking

• Wet voice

• Drooling

• Aspiration risk

• Difficulty moving food

• Poor airway protection

Which cranial nerves are important for swallowing?

CN V, VII, IX, X, and XII

• 5, 7, 9, 10, 12

What is dysarthria?

Impaired motor speech or articulation from

• Weakness

• Incoordination

• Poor control of speech muscles

How can dysarthria present?

Garbled, slurred, slow, or poorly articulated speech

Which cranial nerves are often involved in dysarthria?

CN V, VII, X, and XII

• 5, 7, 10, 12

What is diplopia?

Double vision from impaired eye movement or alignment

Which cranial nerves are responsible for eye movement and can cause diplopia if damaged?

CN III, IV, and VI

• 3, 4, 6

What does CN III do?

Oculomotor control of eye movement

• 3 = oculomotor

What does CN IV do?

Trochlear control of eye movement

• 4 = trochlear

What does CN VI do?

Abducens control of eye movement

• 6 = abducens

What is dysmetria?

Poor judgment of distance or range during movement

• met → meter → distance

How does dysmetria present?

A patient may overshoot or undershoot a target during movement

• Can’t judge distance

What is an example of dysmetria?

Reaching for a pen and overshooting or undershooting it

• Can’t judge distance

What does dysmetria reflect?

Cerebellar error correction and motor coordination

What is the main connection role of the brainstem?

It connects the cerebrum with the spinal cord and cerebellum

What major pathways are found in the brainstem?

Major ascending and descending pathways

• brainstem = up + down pathways

What are the three parts of the brainstem?

1. Midbrain

2. Pons

3. Medulla

What are the main functions of the midbrain?

• Vision & auditory processing

• Alertness

• Motor pathway involvement

What is the main role of the pons?

Acts as a bridge between the cerebrum, cerebellum, and medulla

Why is the pons important?

• An important relay area

• Houses multiple cranial nerves

What are the main functions of the medulla?

Autonomic control of cardiac, respiratory, and vasomotor functions

What structure is the medulla continuous with?

The spinal cord

How does the brainstem regulate vital functions?

Through autonomic control centers, especially in the medulla

What is the cerebellum responsible for?

Coordinating:

• Voluntary movement

• Balance

• Posture

• Fine motor control

• Motor learning

• Equilibrium

What types of information does the cerebellum integrate?

Intended movement from frontal and motor regions with sensory feedback from:

• Proprioceptors

• Vestibular receptors

• Brainstem activity

• Spinal cord activity

What does the cerebellum compare during movement?

Intended movement with actual movement

• Cerebellum compares intended vs actual mvmt

What does the cerebellum do when intended movement and actual movement do not match?

It makes corrections to improve coordination

Does the cerebellum directly control lower motor neurons?

No, it influences lower motor neurons indirectly through upper motor pathways

What are climbing fibers?

Excitatory inputs to Purkinje cells that carry movement error signals so the cerebellum can correct movement

What do climbing fibers tell Purkinje cells?

That a movement needs correction

What are Purkinje cells?

Inhibitory cerebellar cells that use GABA to project to cerebellar nuclei and fine-tune motor output

What do Purkinje cells do?

Fine-tune and modulate motor output

What neurotransmitter do Purkinje cells use?

GABA

Are Purkinje cells excitatory or inhibitory?

Inhibitory

What neurotransmitter do climbing fibers use?

Glutamate

Are climbing fibers excitatory or inhibitory?

Excitatory

What can happen if Purkinje or climbing fiber systems are impaired?

• Poor movement correction

• Cerebellar ataxia

• Dysmetria

What is cerebellar ataxia?

Poorly coordinated movement due to cerebellar dysfunction

What is the easiest way to remember cerebellar function?

The cerebellum compares intended movement with actual movement and corrects errors

• Intended vs actual mvmt & makes corrections

What is the easiest way to remember the brainstem’s major role?

It connects the brain to the body and controls vital functions