Clinical Tests
Asking a patient to say “ahh” while you observe soft palate elevation assesses the motor function of this nerve.
What is CN X, vagus?
This cranial nerve carries visual information from the retina to the lateral geniculate nucleus of the thalamus.
What is CN II, optic?
A patient’s right eye cannot move medially when attempting to look left. Which cranial nerve or structure is most likely affected?
What is the right oculomotor nerve (CN III)?
A patient can clench their jaw and sense facial touch normally, but jaw deviation occurs when opening the mouth — revealing weakness in this nerve’s motor branch.
What is the trigeminal nerve (mandibular branch, CN V₃)?
Before the neuron doctrine was accepted, this theory proposed that the nervous system was one continuous network rather than a collection of individual cells.
What is the reticular theory?
The tongue-deviation test—asking a patient to stick out their tongue—checks for damage to this cranial nerve.
What is CN XII, hypoglossal?
Sound vibrations in the cochlea are transformed into electrical signals that travel through this cranial nerve to the brain.
What is CN VIII, vestibulocochlear?
When you stick out your tongue and it deviates to the right, this cranial nerve is likely damaged on that same side.
What is the right hypoglossal nerve (CN XII)?
A dilated pupil that doesn’t respond to light, while eye movements remain mostly intact, points to damage in this cranial nerve.
What is the oculomotor nerve (CN III)?
This lobe of the cerebral cortex lies inferior to the Sylvian fissure and is important for auditory processing and memory.
What is the temporal lobe?
Having a patient smile, raise their eyebrows, and puff out their cheeks tests the motor function of this nerve.
What is CN VII, facial?
Somatosensory input from the posterior third of the tongue reaches the brainstem via this cranial nerve.
What is CN IX, glossopharyngeal?
Coordinated downward gaze—like when reading or looking down a microscope—depends on this cranial nerve and its control of the superior oblique muscle.
What is the trochlear nerve (CN IV)?
A lesion in this cranial nerve produces both hoarseness and difficulty swallowing, owing to weakness in the laryngeal and pharyngeal muscles.
What is the vagus nerve (CN X)?
Alongside the mesencephalon and rhombencephalon, this embryonic vesicle forms the forebrain region of the developing nervous system.
What is the prosencephalon?
Touching each side of the face with a cotton swab tests the sensory component of this cranial nerve.
What is CN V, trigeminal?
Axons from the taste buds on the anterior two-thirds of the tongue project through this cranial nerve to the nucleus of the solitary tract.
What is CN VII, facial?
This muscle, controlled by the abducens nerve, moves the eye directly outward.
What is the lateral rectus?
Hearing remains intact, but balance is impaired and vertigo occurs after a peripheral lesion in this cranial nerve.
What is the vestibulocochlear nerve (CN VIII, vestibular branch)?
Composed of the midbrain, pons, and medulla, this region connects the cerebrum to the spinal cord and regulates vital functions like breathing and heart rate.
What is the brainstem?
Asking a patient to follow your finger in an H pattern evaluates these cranial nerves
What are CN III (oculomotor), CN IV (trochlear), and CN VI (abducens)?
Parasympathetic fibers from the Edinger–Westphal nucleus travel with this cranial nerve to reach the ciliary ganglion, where they synapse before innervating the pupillary sphincter.
What is CN III, oculomotor?
Damage to the accessory nerve causes weakness in these two muscles, which rotate the head and elevate the shoulder.
What are the sternocleidomastoid and trapezius muscles?
Rightward gaze palsy with preserved convergence localizes the lesion to this cranial nerve or its nucleus.
What is the right abducens nerve (CN VI)?
Camillo Golgi and Santiago Ramón y Cajal shared the Nobel Prize in Physiology or Medicine in this year for their work on the structure of the nervous system.
What is 1906?