Anatomy-Upper Brainstem Flashcards
Where is the visual field motion detector located in the brainstem?
Superior colliculus, in the rostral posterior midbrain
Where is the structure located in the midbrain that excites upper limb flexors and routes input from the cerebral cortex and cerebellum?
Red nucleus, in the center of the rostral midbrain.
Where is the structure located in the midbrain that deals with motor movements and has dopaminergic neurons?
The pars compacta and pars reticulate of the substantia nigra, in the rostral ventral midbrain.
Where is the structure located in the midbrain that sends preganglionic parasympathetic fibers to the ciliary ganglion?
The Edinger-Westphal nucleus sends the parasympathetic fibers that innervate the ciliary muscle and constrictor papillae. Note that it resides in the same nucleus as CN III, which is what the preganglionic parasympathetic fibers run on.
Where is the structure located in the midbrain that is the major relay point for the auditory system before information is sent to the medial geniculate body?
The inferior colliculus, in the posterior caudal midbrain.
Where in the midbrain is the nucleus of the cranial nerve that innervates superior oblique located?
The trochlear nucleus, in the central caudal midbrain.
Where are afferent fibers coming into the inferior colliculus coming from?
Lateral lemniscus
Where in the upper pons is the structure involved in focusing attention on stimuli and initiating sleep located?
Locus ceruleus in the dorsal part of the upper pons.
Where is the structure located in the brainstem that receives 2 point tactile discrimination and vibration sensation for the face?
Principal sensory nucleus in the dorsal middle pons.
Where is the structure located in the brainstem that innervates the muscles of mastication?
Motor nucleus of V in the dorsal middle pons.
Where is the structure located in the brainstem that innervates the lateral rectus muscle?
Abducens nucleus located in the dorsal lower pons, just anterior to the 4th ventricle. Note that its nerve goes through the tegmentum and basilar pons (inferior pontine sulcus) as it exits the brainstem.
Where is the structure located in the brainstem that innervates muscles of facial expression?
Facial nucleus, in the middle lower pons. Note that it slingshots its axons around the abducens nucleus before exiting the anterior lower pons.
Where is the structure located in the pons that receives pain, light tough and temperature signals from the face?
Spinal Vth nucleus and tract in the lower pons.
Follow the corticospinal tract from the frontal & parietal cortex down.
Cortex -> Internal capsule -> Crus cerebri -> Medullary pyramids -> Pyramidal decussation -> Contralateral muscles
Follow the corticobulbar tract from the motor cortex down.
Motor cortex for face & head -> CNs V, VII & XII
What causes your right pupil to constrict when you shine light into the right eye?
Light hits photoreceptors -> Retinal ganglion cells fire -> Some fibers go to lateral geniculate body, others go to the pre-tectal nucleus -> Pre-tectal axons go to the Edinger-Westphal nucleus (CN III) -> Bilateral Ciliary ganglion -> Bilateral sphincter pupillae
A patient comes to see you with vision problems in clinic. When you shine the light in the right eye there is no direct or consensual pupillary light reflex. The left eye has a direct and consensual pupillary reflex when you shine light in it. What is wrong with this patient’s right eye?
CN II. They are completely blind in the right eye. Light has no ability to stimulate photoreceptors in that eye.
A patient comes to see you with vision problems in clinic. On physical exam you notice that when you shine the light in the right eye, there is no direct pupillary reflex in the right eye, but consensual pupillary reflex is present in the left eye. When you shine the light in the patient’s left eye, direct pupillary reflex is present but consensual reflex by the right eye is absent. What is wrong with the patient’s right eye?
CN III. The eye is able to sense the light but not able to elicit the motor arm of the pupillary light reflex (Edinger-Westphal nucleus and beyond)
What cranial nerves are you testing when you do the corneal light reflex?
Touch cornea -> Long ciliary nerve -> Nasociliary nerve -> V1 (opthalmic) -> Trigeminal ganglion -> Trigeminal nerve -> Spinal Vth tract -> Spinal Vth nucleus -> Bilateral secondary axons to facial motor nucleus -> CN VII upper division -> Zygomatic nerves -> Palpepral part of orbicularis oculi -> Bilaterl blinking
What cranial nerve is likely to be injured in a patient who only has consensual corneal reflex but not direct corneal reflex?
The motor limb (VII)
What cranial nerve are you testing when you do the jaw-jerk reflex?
Afferent V3 fibers -> Mesencephalic nucleus -> Motor nucleus of V -> Efferent V3 fibers closes jaw
What 4 symptoms would a patient present with who has Tegmental (Benedikt’s) Syndrome?
This is due to lateral tegmental vascular infarction that damages the red nucleus & superior cerebellar peduncle (ipsilateral intention tremor), medial lemniscus (contralateral 2 pt tactile/vibration), spinothalamic (contralateral pain, temp, light touch) and interpeduncular fossa (ipsilateral oculomotor nerve palsy).
Superior Alternating Hemiplegia (Weber’s Syndrome) symptoms?
Contralteral hemiparesis (corticospinal tract), contralateral hemiparesis of face (corticobulbar tract) and ipsilateral oculomotor nerve palsy (CN III fibers near interpeduncular fossa)
Middle Alternating Hemiplegia symptoms?
Contralateral hemiparesis (corticospinal tract), contralateral hemiparesis of lower face (corticobulbar tract) and medially deviated eye (abducens fibers)
Millard-Gubler Syndrome symptoms?
Middle alternating hemiplegia + facial nerve. Contralateral hemiparesis (corticospinal), contralateral lower face paralysis (corticobulbar), ipsilateral medially deviated eye (abducens nerve) and ipsilateral motor impairment of lower face (facial nerve)
Inferior Alternating Hemiplegia symptoms?
Contralateral hemiparesis (corticospinal tract) and ipsilateral tongue atrophy (hypoglossal nerve)
