Brain Stem and Cranial Nerves

Brainstem connects

brain and spinal cord

Brainstem contains

cranial nerve nuclei

Brainstem controls

autonomic and motor functions

brainstem is important for

consciousness (reticular formation)

Brainstem regions

- midbrain

- pons

- medulla oblongata

Brainstem each region contains

specific cranial nerve nuclei

Midbrain Cranial nerves

- CN III

- CN IV

Pons Cranial Nerves

- CN V

- CN VI

- CN VII

- CN VIII

Medulla Cranial Nerves

- CN IX

- CN X

- CN XI

- CN XII

CN I - Olfactory: function

smell

CN I - Olfactory: Pathology

- Head trauma

- Neurodegenerative Disease

CN I - Olfactory: Signs

Loss of smell (anosmia)

CN II - Optic: function

vision

CN II - Optic: pathology

- optic neuritis

- MS

- tumors

CN II - Optic: Signs

- vision loss

- visual field defects

CN III - Oculomotor: function

- eye movement

- pupil constriction

CN III - Oculomotor: Pathology

- aneurysm

- diabetes neuropathy

CN III - Oculomotor: Signs

- Ptosis

- dilated pupil

- down and out eye

CN IV - Trochlear: function

superior oblique muscle

CN IV - Trochlear: Action

eye down and inward

CN IV - Trochlear: signs

- vertical diplopia

- difficulty looking down

CN V - Trigeminal: function

- facial sensation

- mastication

CN V - Trigeminal: Branches

V1, V2, V3

CN V - Trigeminal: Pathology

trigeminal neuralgia

CN V - Trigeminal: Signs

- facial pain

- facial numbness

CN VI - Abducens: Function

lateral rectus muscle

CN VI - Abducens: action

eye abduction

CN VI - Abducens: signs

- medial eye deviation

- diplopia

CN VII - Facial: function

- facial expression

- taste

CN VII - Facial: pathology

bell's palsys

CN VII - Facial: Signs

- facial droop

- inability to close eye

CN VIII - Vestibulocochlear: Function

hearing and balance

CN VIII - Vestibulocochlear: Pathology

acoustic neuroma

CN VIII - Vestibulocochlear: Signs

- vertigo

- hearing loss

CN IX - Glossopharyngeal: function

- posterior tongue taste

- swallowing

CN IX - Glossopharyngeal: Signs

- dysphagia

- loss of gag reflex

CN X - Vagus: Function

- parasympathetic control

- voice swallowing

CN X - Vagus: Signs

- hoarseness

- dysphagia

CN XI - Spinal Accessory: function

SCM and trapezius

CN XI - Spinal Accessory: Signs

- shoulder weakness

- difficulty turning head

CN XII - Hypoglossal: function

tongue movement

CN XII - Hypoglossal: Signs

- tongue deviation

- speech difficulty

Clinical Examination of Cranial Nerves I-VI

- CN I: Smell

- CN II: Vision

- CN III, IV VI: Eye movement

- CN V: Facial Sensation

Clinical Examination of Cranial Nerves VII - XII

- CN VII: Facial Expression

- CN VIII: hearing/balance

- CN IX,X: gag reflex

- CN XI: Shoulder Shrug

- CN XII: tongue movement

Major pathologies affecting Cranial Nerves

- Stroke

- Multiple Sclerosis

- Tumors

- Trauma

- Neurodegenerative disesases

A stroke can damage

brainstem or cortical areas controlling cranial nerves

Stroke mechanism

Loss of blood supply --> neuron death in CN nuclei or pathways

Possible Cranial nerve Effects of Stroke

- CN III: Double vision, ptosis

- CN VII: facial droop

- CN IX and X: difficulty swallowing (dysphagia)

- CN XII: tongue deviation

- CN V: Facial sensory loss

Clinical signs of stroke in CN

- dysarthria

- dysphagia

- diplopia

- Facial asymmetry

MS is a

demyelinating disease of the CNS

MS mechanism

immune system attacks myelin in CNS pathways, including those controlling CN

MS common CN involvement

- CN II: optic neuritis -> vision loss

- CN III, IV, VI: eye movement abnormalities

- CN V: trigeminal neuralgia

- CN VII: facial weakness

MS clinical signs of CN

- blurred vision

- Pain w/ eye movement

- double vision

- facial pain

Tumors can

compress CN or brainstem nuclei

Tumor mechanisms

- direct compression

- Increased Intracranial pressure

- Invasion of nerve pathways

Tumor example, Acoustic Neuroma

(vestibular schwannoma) affects CN VIII

Tumors possible effects

- hearing loss

- balance problems

- facial numbness

- vision problems

- difficulty swallowing

Head injuries may

stretch, compress or sever cranial nerves

Head injuries mechanisms

- skull fractures

- brainstem injury

- direct nerve damage

head injuries common CN injuries

- CN I: loss of smell

- CN VII: Facial paralysis

- CN III: pupil dilation and eye movement issues

- CN VIII: hearing loss or vertigo

Head injuries clinical signs

- loss of smell

- facial paralysis

- double vision

- hearing loss

Neurodegenerative Diseases cause

progressive neuronal degeneration

Neurodegenerative Diseases examplles

- ALS

- Parkinsons

- Alzheimers

Neurodegenerative Diseases mechanism

gradual degeneration of neurons in the brainstem

Neurodegenerative Diseases possible CN effects

- CN IX, X: swallowing difficulty

- CN XII: tongue weakness

- CN VII: Facial Weakness

- CN III, IV, VI: impaired eye movement

Neurodegenerative Diseases Clinical Signs

- dysphagia

- dysarthria

- facial masking

- tongue atrophy

Clinical relevance for PTs

- balance disorders

- dysphagia

- facial weakness

- vestibular dysfunction

- neurological rehabilitation

Key takeaways

- Brainstem controls CN nuclei

- CN control sensory, motor, and autonomic functions

- pathology can cause significant neurological deficits