Lectures 8, 10: Brainstem and Cranial Nerves Flashcards
The trochlear nerve emerges __________ and wraps around the brainstem at what junction?
Ventrally; at the junction b/t the midbrain and pons
Motor nuclei are _______ and sensory nuclei are _______
Medial; lateral
Cortical innervation of cranial nerves is bilateral in all cases except (2)
Portion of VII and XII
What is the significance of bilateral cortical innervation of cranial nerves?
Unilateral cortical lesion would not impact nerve function
What is the sole CN that crosses the midline?
IV
Discuss the anatomy of the olfactory nerve
Short primary sensory nerves (cranial nerves) –> (cribiform plate) –> Olfactory bulb –> primary olfactory cortex
What is one way to damage olfactory nerve fibers? What process of the cell is damaged?
Anterior cranial fossa fractures; primary axons
How do you test for CSF rinorrhea?
Glucose or beta 2 transferrin
Anosmia
Loss of sense of smell
Parosmia
Perverted sense of smell
Olfactory hallucinations are often caused by…
Temporal lobe (parahippocampal) seizures
How do you test olfactory nerve function?
Coffee/vanilla, one side at a tie; note: don’t use an irritating smell
Temporary anosmia caused by colds affects what level of the olfactory system?
The receptors
What are four ways to damage the central processing structures of the olfactory system?
Contusion/laceration of olfactory bulb, aneurysm, olfactory groove meningioma, frontal lobe tumor
What are the 3 trigeminal sensory nuclei and what do each control?
- Spinal trigeminal: crude touch; 2. Pontine Trigeminal (chief): discriminative touch; 3. Mesencephalic: proprioception from muscles of mastication
Where is the trigeminal motor nucleus?
The pons
What are the 3 branches of the trigeminal nerve and where does each exit the skull?
V1: Opthalmic, superior orbital fissure; V2: Maxillary, foramen rotundum; V3: Mandibular, foramen ovale
Where are the cell bodies of the sensory fibers of the trigeminal nerve?
Trigeminal ganglion
What is unique about the cell bodies that control the jaw jerk reflex?
They are located in the mesencephalic nucleus, not the trigeminal ganglion
What is one common condition associated with the trigeminal nerve? Describe this condition and a common cause
Trigeminal neuralgia; triggered by light touch/gustatory, rarely during sleep, pain-free intervals; common cause: vascular compression due to oligodendrocyte myelination
The jaw deviates to the ________ side
Affected
To test the 1st branch of the trigeminal ganglion, you can check which reflex?
Corneal
What virus often effects the trigeminal nerve? What is one complication that must be evaluated for?
Herpes zoster; herpes opthalmicus (if it affets the opthalmic division)
Why is the trigeminal nerve associated with an parasympathetic reflex?
Very close to superior salivatory nucleus –> sinus symptoms, watery eyes
Where is the facial motor nucleus? The part of the nucleus supplying forehead muscles gets what type of innervation? What about lower facial muscles? What two muscles besides muscles of facial expression?
Pons; bilateral; contralateral; stapedius (dampens sound) and part of digastric
Where are the cell bodies of the sensory fibers of the facial nerve? What nerve connects this ganglion to the brainstem nuclei?
Geniculate nucleus; nervous intermedius
What does the GSA section of the facial nerve control? What nucleus?
Ear sensations (concha, behind ear, external auditory canal); spinal trigeminal
What does the SVA section of the facial nerve control? What nucleus? What special nerve?
Taste from anterior 2/3 of tongue; solitary nucleus; chorda tympani
What does the GVE section of the facial nerve control? What two nerves? What nucleus?
Lacrimal gland via V2 branches; Submandibular and sublingual via chorda tympani; superior salivatory nucleus
Describe the basic anatomy of the facial nerve
Exits brainstem through cerebellopontine angle –> internal auditory meatus and facial canal –> stylomastoid foramen
A lower motor neuron lesion causes facial palsy where? What are three common causes?
Palsy on same side as lesion on upper and lower face; Bell’s palsy, meningeal process (Guillain-Barre), or a stroke involving the VII nucleus
An upper motor neuron lesion causes facial palsy where? What is a common cause?
Palsy on contralateral side as lesion on lower face only; stroke
Describe the fives types of information carried by the Glossopharyngeal nerve
SVE: stylopharyngeus (swallowing); GVE: parotid gland; GSA: middle ear; SVA: taste from posterior 1/3 of tongue; GVA: touch from pharynx and posterior 1/3 of tongue, afferent limb of gag reflex, carotid body/sinus
Describe the basic anatomy of the glossopharyngeal nerve. What are the associated nuclei?
Exits the brainstem ventrally from upper medulla –> jugular foramen; spinal trigeminal, nucleus ambiguus, solitary nucleus, caudal solitary nucleus, inferior salivatory nucleus
Lesions of the glossopharyngeal nerve can cause (5)
Difficulty swallowing, taste impairment, impaired gag refelx, reduced saliva, syncope
One condition unique to glossopharyngeal nerve
Glossopharyngeal neuralgia
Describe the basic anatomy of the vagus nerve
Exist the brainstem from the medulla –> jugular foramen –> carotid sheath (inbetween internal carotid and internal jugular)
The vagus nerve synapses on what four nuclei? Fiber type and functions?
- Dorsal nucleus of vagus nerve (GVE, parasympathetic output to viscera –> left colic flexure); 2. Nucleus ambiguus (SVE, brachial muscles of larynx/pharynx, upper esophagus, palate); 3. Solitary nucleus (SVA and GVA, epiglottal taste and sensation from mouth –> L colic flexure); 4. Trigeminal nucleus (GSA, dura, external ear and tympanic membrane)
Six main functions of vagal nerve
Phonation, swallowing, palate elevation, taste, cutaneous sesnastion from ear, and visceral innervation (neck –> L colic flexure)
What are some symptoms of vagal problems (4)
Loss of gag reflex, paralysis of soft palate (dyspnea, dysarthria, dysphagia), parasympathetic disturbances, lowering of palate and deviation of uvula
What is unique about the uvula?
Deviates TOWARD normal side
What are the two divisions of the spinal accessory nerve and how are they anatomically similar and different? What do they innervate?
Cranial division arises from the nucleus ambiguus –> jugular foramen –> intrinsic muscles of larynx but NOT cricothyroid; Spinal division arises from the ventral horn of C1 - C6 –> foramen magnum –> jugular foramen –> sternocleidomastoid and trapezius
Three clinical correlations of the spinal accessory nerve
- Difficulty turning head to contralateral side; 2. Shoulder droop; 3. Larynx paralysis
Describe the anatomy and basic function of the hypoglossal nerve
Mediates tongue movement; hypoglossal nucleus –> hypoglossal canal –> intrinsic and extrinsic tongue muscles
If LMNs are involved, the how does the tongue deviate? IF UMNs?
Toward lesion; away from lesion
What is Pseduobulbar palsy?
Bilateral corticobulbar tracts involved; inability to control facial movements, swallowing, spastic speech, emotional outbursts
