Cranial Nerves & The Special Senses

Cranial nerves are the pathways to perception of

•Olfaction

•Taste

•Visual system

•Hearing and balance

 

Cranial nerves reside in throughout the brain: cerebrum, and brain stem (midbrain, pons, and medulla oblongota). PTs will screen and assess gross cranial nerve function through observation of involuntary movement and simple motor commands.

Brainstem: connects spinal cord to brain; integration of reflexes necessary for survival

204LBrainstem.JPG

Cranial nerves (CN): part of peripheral nervous system which arises directly from brain. Two pairs of CN arise from cerebrum; ten pairs arise from brainstem. Indicated by

Roman numerals I-XII from anterior to posterior. CNs may have one or more of three functions

 

Subdivisions and Associated Cranial Nerves

Brain Subdivision

Associated Cranial Nerve

Major Function

cerebrum

I: Olfactory

Smell and taste

thalamus

II: Optic

Vision

midbrain

III: Oculomotor

IV: Trochlear

Eye movements (adduction, elevation, depression) and motor for eyelid

pons

V: Trigeminal

VI: Abducens

VII: Facial

VIII: Vestibulocochlear(part)

Face sensation and motor

Lateral eye movement

Face sensory and motor, taste

 

Hearing and balance

medulla oblongata

VIII: Vestibulocochlear (part)

IX: Glossopharyngeal

X: Vagus

 

XI: Spinal Accessory

XII: Hypoglossal

Hearing and balance

 

Taste posterior third of tongue and sensory/motor in throat

Autonomic functions for viscera, (BP, HR, RR), speech, breathing

Motor to SCM and trapezius

Motor function for tongue

 

Role of the PTA

PTAs can perform cranial nerve tests, document results, and communicate observations which may require further examination by the supervising PT or physician. Any patient who reports and/or demonstrates new signs and symptoms of brainstem dysfunction may be experiencing a medical emergency. PTAs may perform cranial nerve tests and report the results to the supervising PT. The role of the PT is to interpret the results, make changes to the treatment plan as needed, and consult with other health care personnel as needed.

Cranial Nerve Tests and Measures

The Wayne State Tutorial is highly detailed and includes a section on "interpretation" which is outside of the PTA scope of practice. We have narrowed the focused of the tutorial by linking the procedures for testing in the table below. A PTA should be able to select and perform tests for cranial nerve function. Specific cranial nerve testing procedures are linked below:

Cranial Nerve

Procedures

Video Demo of Normal Function

I - Olfactory

Testing Smell

Smell test video

II - Optic

Testing Visual Fields

Visual field test demo

III, IV, VI - Eye control

Tracking

Saccades

Convergence

Divergence

Eye motor control test demo

V - Trigeminal

Testing face sensation

Face sensation and motor test demo

VII- Facial

Testing face muscles

Facial motor testing and taste demo

VIII - Vestibulocochlear

Testing hearing function

Testing vestibular function

Hearing function test demo

IX, X - Gag Reflexes

Testing gag reflex

Testing vocal motor function

Gag reflex testing demo

XI - Spinal Accessory

Testing Trapezius and SCM function

Manual muscle testing demo

XII - Hypoglossal

Testing tongue movements

Tongue strength and motion testing demo

 

For your reference, you can link to the full Wayne State Cranial Nerve Tutorial

 

PTAs are aware of the functional deficits which may result from CN dysfunction, so the treatment area and treatment interventions are safe and effective for patient, PTA, and any caregivers/family members involved in the session. Examples of possible safety considerations include:

 

 

Abnormal Cranial Nerve Tests and Measures

Abnormal Cranial Nerve II

Recall that visual fields are dependent on individual eye function as well as convergence of both eyes on an object/image.

204LVisualfield.JPG

The video provides an example of a patient with a R visual field cut.

Abnormal CN V Sensory Exam

This patient demonstrates unilateral sensory dysfunction in the Trigeminal nerve. Recall that the the Trigeminal nerve is the primary nerve anesthetized during dental procedures.

Abnormal CN VII: Note the asymmetry in facial muscles

Abnormal CN XII (Hypoglossal)

The tongue will deviate toward the affected (weaker) side when the patient is prompted to stick out their tongue

Cranial nerve coordination examination

Sample of Normal VOR

The VOR is also referred to as the "Doll's Eye's" reflex. The examiner is assessing both eye motor function and coordination of eye and head motions which includes CN VIII