Neuro II - First Aid Flashcards
A 33 year old male presents with left-sided hearing loss. Symptoms began shortly after going to the shooting range for the first time, he didn’t have ear plugs. What results would you expect to see from the Rinne and Weber tests?
He’s got conductive hearing loss from a popped ear drum. The Rinne test will be abnormal, with left-sided bone hearing better than left-sided air hearing. The Weber test will cause the sound to localize to the left ear.
A 27 year old female presents with right-sided hearing loss and vertigo. You think she had a viral infection that caused these symptoms. What results would you expect to see from the Rinne and Weber tests?
She likely has vestibular labrynthitis. This causes sensorineural hearing loss. Her Rinne test will be normal, with right-sided air hearing better than right-sided bone hearing. Her Weber test will cause localization of the sound to her good ear, the left side.
A 79 year old man presents with bilateral hearing loss. You determine that this is a result of aging. What region of the cochlear duct is most likely causing hearing loss in this patient?
The part of the basilar membrane that vibrates most with high frequency sounds is the base (closest to the oval and round windows). This region becomes stiff and vibrates less with age, causing hearing loss of high-frequency sounds first.
A patient presents to the clinic complaining of difficulty standing, he keeps falling to his left. He says that he feels like the left side of his body is completely uncoordinated and he overshoots grabbing things with his left hand. Where in the cerebellum does he likely have a lesion?
The left lateral cerebellar hemisphere is responsible for receiving right cortical input. Input is received through the middle cerebellar peduncle. The cerebellum then relays feedback via the dentate nuclei to the right cortex. Deficits in this system will cause problems with modulation and coordination of motor movements because the cortex and cerebellum are no longer in communication. Lesions could be anywhere along this tract. Note that input is received from the contralateral cerebral cortex and output sent to the same contralateral cortex.
A patient presents to the clinic with difficulty standing upright and maintaining his gaze in a single direction. Where in the cerebellum might this patient have a lesion?
Vestibulocerebellum. This region of the cerebellum receives direct input from the vestibular nerves. It is responsible for suppressing the vestibuloccular reflex and allowing eyes to stay fixed on an object while the head is rotating. Additionally, the medial region of the cerebellum is responsible for balance and truncal coordination, which is why the patient can’t stand upright.
What would happen if you had a genetic mutation that eliminated connections between granule cells and Purkinje cells in cerebellar gray matter?
Mossy afferent fibers enter the cerebellum and some synapse directly on the deep nuclei (dentate, emboliform, globose, fastigial), exciting them. Some continue to synapse on the granule cells to excite them. Granule cells then excite Purkinje cells, which in turn inhibit the deep nuclei. Normally this excitation and inhibition of the deep nuclei allows us to fine tune movements. Without the inhibitory Purkinje cell action, movements would be uncoordinated.
What is the sole cerebellar input that provides climbing fibers?
Inferior olive. These are thought to inhibit incorrect movements because they synapse directly on the Purkinje cells and thus cause rapid inhibition.
A patient presents with right-sided proprioceptive deficits. MRI reveals a lesion that prohibits proprioceptive fibers from entering the cerebellum. Where is the likely location of the lesion?
Inferior cerebellar peduncle, this is the location of ipsilateral proprioceptive cerebellar input.
A patient presents to the clinic complaining of rapid onset eye problems. On forward gaze the patient’s eyes deviate to the left. Physical exam reveals inability to produce voluntary horizontal saccades to the patient’s right side. When the patient’s gaze is directed to the left, nystagmus is greatest. Where does he most likely have a lesion?
The left frontal eye field (FEF) or the right paramedian pontine reticular formation (PPRF). When you decide to voluntarily look RIGHT, the LEFT FEF initiates the command. The command then travels to the RIGHT PPRF. The PPRF transmits the signal to the RIGHT CN VI nucleus causing contraction of the right lateral rectus. The signal from the CN VI nucleus also travels to the LEFT CN III nucleus via the MLF, causing the LEFT medial rectus to contract.
If a patient presents with a frontal eye field lesion, will the eyes deviate towards or away from the side of the lesion? What if the lesion was in the paramedian pontine reticular formation?
FEF: eyes deviate toward the side of the lesion on forward gaze. PPRF: eyes deviate away from the side of the lesion on forward gaze.
A patient presents with an inability to look up over the past few days. MRI reveals a pineal gland tumor. What is causing her to present this way?
The pinealoma can compress the superior colliculi of the midbrain, which is the conjugate vertical gaze center.
Your grandma has a stroke that diminishes the activity of every single cranial nerve except for one. What portion of her brain was affected by the stroke?
Probably the thalamus. CN I is the only cranial nerve without thalamic relay to the cortex.
A patient comes to see you for a routine eye exam. You report that conjugate gaze was normal in all cardinal directions and that pupils were equal, round, reactive to light and accommodation. What parts of your report tell us that cranial nerve III is fully in tact?
1) Cardinal directions tell us the SR, IR, MR & IO are all functioning. 2) Equally reactive to light and accommodation tells us that the pathway from retinal ganglion cells -> Edinger-Westphal nucleus -> parasympathetic fibers that innervate the sphincter pupillae and ciliary muscles are in tact on both sides. 3) The fact that the patient’s eyes are open tells us CN III innervation of levator palpebrae is unaffected.
A patient presents to the ED with a stroke. Imaging reveals infarction of areas in the midbrain. What cranial nerves may be affected?
III and IV nuclei are located in the tegmentum of the midbrain
A patient presents to the ED with a stroke. Imaging reveals infarction of areas in the pons. What cranial nerves may be affected?
V, VI, VII and VIII nuclei are located in the tegmentum of the pons.
A patient presents to the ED with a stroke. Imaging reveals infarction of areas in the medulla. What cranial nerves may be affected?
IX, X and XII nuclei are located in the tegmentum of the medulla.
After a terrible motorcycle accident, you rush to the scene with your pen light. Pupils are equal and reactive to light, however, the patient only closes the right eye when you touch his left cornea. What cranial nerve is affected in this patient?
CN VII on the left, after the facial motor nucleus. The afferent limb of the corneal reflex is V1. V1 travels up to the spinal Vth nucleus where it synapses. The spinal Vth nucleus then activates bilateral facial motor nuclei to fire the palpebral part of the orbicularis oculi.
Afferent and efferent pathways in the jaw jerk reflex
Afferent = V3 muscle spindle fiber from masseter. Efferent = V3 motor neuron to masseter
A patient comes to see you after hitting his head on the diving board. When you shine your light into this left pupil, it stays dilated and the right pupil constricts. What cranial nerve is likely affected?
Left CN III. When you shine the light in the left eye, the retinal ganglion cells transmit the signal up CN II. CN II sends some fibers to the pretectal nucleus. The pretectal nucleus sends fibers to the Edinger-Westphal nucleus. The Edinger-Westphal nucleus sends out parasympathetic fibers that synapse in the ciliary ganglion. The ciliary ganglion sends out fibers that cause the sphincter pupillae to fire.
A patient comes to the ED suffering from a terrible bout of impetigo on his face. You send him home with some topical antibiotics. Two days later he returns complaining of double vision and decreased sensation on his upper lip and nose. Physical exam reveals absence of corneal reflex when the right eye is touched and complete paralysis of the right extra-ocular muscles (opthalmoplegia). What is causing his symptoms?
Veins of the face drain through the cavernous sinus. His impetigo infection spread into the cavernous sinus and caused thrombosis of the veins in there, compressing extra ocular CNs III, IV and VI and sensory CNs V1, V2.
Is the right or left trigeminal nerve lesioned in this patient?
Right. The weak pterygoid muscles are overcome by the normal pterygoid muscles on his left side, causing the jaw to deviate toward the side of the lesion.
A patient presents to your clinic looking like this. What cranial nerve is affected and where is the lesion?
Note that his forehead is flattened out, this indicates a CN VII LMN lesion because the forehead has bilateral UMN input and would maintain tonicity if an UMN were lesioned.
A patient presents to the clinic complaining of a dry right eye because he cannot close it. He also says that food has lost some taste. Physical exam reveals a drooping left corner of the mouth. What are possible etiologies of this condition?
This patient is presenting with symptoms of facial nucleus damage. When idiopathic, this is called Bell’s Palsy. It can also be a complication of AIDS, Lyme, HSV, HZV, Sarcoidosis, Tumors or Diabetes.
You take a big bite of your wife’s ice cream cone while she isn’t looking. When she notices she tells you to open your mouth so she can see if you are the culprit. What muscles did you use to bite and what ones do you use to expose yourself as the culprit?
Bite muscles: Masseter, Medial Pterygoid and Temporalis. Open muscle: Lateral pterygoid. “Lateral Lowers the jaw, all the rest bite”
