CRANIAL NERVE TESTING Flashcards
Sniffing forces a lot of air into the nostrils at once, creating _______ in the nasal cavity. This allows the fragrance to get to the _________ mucosa in the superior nasal cavity.
Turbulence;
Olfactory epithelium/ mucosa
A patient is told to powerfully sniff a vial of cinnamon from a foolish physician. What nerve was stimulated before she sneezed on his face?
Maxillary division of trigeminal nerve (V-2)
When testing the extent of a patient’s visual field, the patient is asked to look _____ _____ while the physician assesses his or her _______ vision.
Straight ahead;
Peripheral vision assessed
Temporal fibers detect light from the _______ field of view and (do/do not) cross the optic chiasm. This differs from nasal fibers that detect light from the ________ field of view and (do/ do not) cross the optic chiasm.
Temporal fibers = Nasal field = Do Not Cross chiasm;
Nasal fibers = Temporal field = Cross chiasm
Describe the features of Bitemporal (heteronymous) hemianopsia and what causes it.
Aka “tunnel vision” is the loss of peripheral vision from a cut or compressed optic chiasm. This can be due to a pituitary adenoma that pushes up against the optic chiasm leading to a loss of detection of the temporal fields of view.
A patient has his right optic nerve cut from a fracture in the optic canal. What visual defect may he experience?
Right Anopsia features the loss of both nasal and temporal fields, meaning blindness, in the right eye.
A patient has been diagnosed by an ophthalmologist with Left Homonymous Hemianopsia. What structure in the cranium may have been affected?
The right optic tract posterior to the optic chiasm may be compressed or cut since the left field of view in both eyes is absent. The right optic tract contains temporal fibers of the right eye and the nasal fibers of the left eye are affected.
Each optic tract contains fibers detecting the nasal visual field of the __________ eye and nerve fibers detecting the temporal visual field of the ___________ eye.
Ipsilateral eye - temporal fibers that pick up nasal field;
Contralateral eye - nasal fibers that pick up temporal field.
A cut at the right optic tract would lead to ….
Left Homonymous Hemianopsia
A lesion at the optic chiasm would present as…
Bitemporal heteronymous Hemianopsia (tunnel vision)
A CT indicates an aneurysm of the right internal carotid artery near the optic chiasm. How would this present in a patient?
Right nasal hemianopsia that affects the nasal visual field of the ipsilateral eye. The aneurysm compressed the right temporal optic fibers that detect the nasal field of view in the right eye.
Describe the cause of Papilledema.
Elevated CSF pressure can compromise the venous return from the retina through the Canal of Schlemm. This leads to visual obscurity in the affected eye since the retina is compressed.
Define the Pupillary Light Reflex.
Light is shown in one eye to cause direct pupil constriction of that eye and consensual constriction of the contralateral eye. This tests both the optic nerve and motor branch of oculomotor nerve for the reflex.
If light is shown in the right eye and ONLY the left pupil constricts, the right optic nerve _______ but the right CN III ______.
CN II works, but the CN III is out.
Light is shown in the left eye and neither pupil constricts. This sign is ________. The left CN II is ______ OR both CN’s III are _______.
Inconclusive;
Left optic nerve is defective OR both CN III’s are not working.
Define Uncal Herniation and why it can be lethal.
This is caused by increased intracranial pressure which pushes down the cortex. The uncus goes over the edge and the CN III can be compressed. This causes dilated pupils (lowered PSNS) and increased pressure on the brainstem which can lead to a coma or death.
A common cause of Uncal Herniations can be _________ hematomas, which can be caused by a rip in the ___________ ________ artery, thus increasing ________ pressure.
Epidural hematomas;
Rip in Middle Meningeal Artery;
intracranial CSF pressure.
The occulomotor nerve can be tested with the ________ for ocular movement and _______. Somatic innervation is tested by the ______ rectus and the PSNS autonomic is tested by the __________ ________.
H in Space, Convergence;
Medial Rectus, Constrictor Pupillae
Define Oculomotor Palsy. What muscles still work?
The affected eye is abducted and depressed leading to Lateral Strabismus. The superior oblique and lateral rectus still work.
Define Abducens Palsy. What muscle still works?
Adduction of the eye leads to Medial Strabismus. The medial rectus is normal.
How can the trigeminal nerve (CN V) can be tested (along the sensory and the motor branches).
The physician can stimulate the senses of the face that were derived from the 1st pharyngeal arch. The motor branch can be tested by palpation of the mastication muscles and the anterior digastrics.
List what features define Facial Palsy.
There is a loss of the nasolabial fold, drooping of the mouth, loss of wrinkles and no blink reflex on the affected side.
How does a physician elicit the Corneal Blink Reflex and what does it mean?
Have the patient look away and gently stroke the cornea to elicit the reflex.
If a physician touches the left eye cornea and neither eye blinks, then she touches the right eye cornea and ONLY the right eye blinks, this means…
The Left CN V and left CN VII are both not working.
