Neuro Exam 2 Study Guide

What are the three parts of the brainstem?

-mesencephalon-midbrain

-pons

-myelencephalon: medulla

What are the superior and inferior borders of the brainstem?

Superior: mammillary bodies–posterior commissure; inferior: pyramidal decussation.

Which cranial nerves arise from the brainstem?

CN 3–12;

CN 1 and 2 do not arise from the brainstem.

What are the 3 internal longitudinal divisions of the brainstem (dorsal to ventral)?

Tectum, tegmentum, basis.

(rectum-middle-belly)

Where is the tectum, and what does it contain?

Dorsal to the cerebral aqueduct;

-contains superior and inferior colliculi

-some include roof of 4th ventricle

Where is the tegmentum, and what does it contain?

Between tectum and basis;

-contains main bulk of brainstem nuclei and reticular formation.

Where is the basis, and what does it contain?

Most ventral division, belly of pons; corticospinal and corticobulbar motor tracts.

what is the corticospinal tract

motor fibers that carry movement-related information from the primary motor cortex to the spinal cord (some from supplementary motor cortices)

what is the Corticobulbar tract

(brainstem=b) travels with the corticospinal tract but terminates on the cranial nuclei in the brainstem;

the cranial nuclei send axons (cranial nerves) to control the muscles of the head, neck, and face

How do corticospinal and corticobulbar tracts differ?

Corticospinal: cortex to spinal motor neurons;

corticobulbar: cortex to cranial motor nuclei controlling head/face/neck.

What does the optic groove (chiasmatic groove) house?

The optic chiasm.

What does the sella turcica contain?

The pituitary gland

(in the pituitary fossa of the sphenoid bone).

What skull-base structures are part of the sphenoid bone?

Sella turcica, optic groove, optic canal, superior orbital fissure, foramen rotundum, and foramen ovale.

Which structures pass through the optic canal?

transmits CN 2 (optic nerve) and ophthalmic artery.

Which structures pass through the superior orbital fissure (SOF)?

transmits CN 3, 4, 5 (V1), 6, and ophthalmic veins.

Which foramen transmits V2 and which transmits V3?

V2: foramen rotundum;

V3: foramen ovale.

What forms the clivus and where is it relative to the pons?

-Superior 1/3 of sphenoid bone

-inferior 2/3 of occipital bone

-lies anterior to the pons.

where is the pons relative to the clivus

posterior to clivus

Where are the petrous temporal bone and clivus located?

-At the skull base; petrous temporal bone lies laterally (Major landmark of the skull base.)

- clivus slopes centrally behind the sella toward foramen magnum.

Where is the optic chiasm relative to the pituitary gland?

Superior to the pituitary gland.

Where are the 4th ventricle and cerebellum relative to the pons?

4th ventricle is dorsal to pons; cerebellum lies posterior to it.

what foramins are part of the middle cranial fossa -slide 15

1. optic canal

2. superior orbital fissure (SOF)

3. foramen rotundum

4. formaen ovale

5. foramen spinosum

6. foramen lacerum

What cranial nerve goes through the:

cribiform plate

CN 1

What cranial nerve goes through the:

OPTIC CANAL

CN 2 (OPTIC) AND OPHTHALMIC ARTERY

What cranial nerve goes through the:

SUPERIOR ORBITAL FISSURE-SOF

CN 3-4 and opthalmic veins

1. CN 3- OCULOMOTOR

2. CN 4- TROCHLEAR

3. CN 5 (V1)- TRIGEMINAL; OPHTHALMIC DIV.

4. CN 6- ABDUCENS

5. OPTHALMIC VEINS

What cranial nerve goes through the:

FORAMEN ROTUNDUM

CN 5 (V2)- TRIGEMINAL; MAXILLARY DIVISION

What cranial nerve goes through the:

FORMAEN OVALE

CN 5(V3)-TRIGEMINAL; MANDIBULAR DIVSION

What foramens are in the posterior cranial fossa

1. internal acoustic meatus

2. jugular foramen

3. hypoglassal canal

4. foramen magnum

What cranial nerve goes through the:

INTERNAL ACOUSTIC MEATUS

CN 7 (FACIAL)

CN 8 (VESTIBULOCOCHLEAR)

Identify structures in Unit 6, slide 18:

Sphenoid sinus: Inferior to the pituitary fossa.

• Pituitary gland: Within the sella turcica (pituitary fossa).

• Anterior and posterior clinoid processes: Sphenoid landmarks surrounding the sella turcica.

• Clivus: Anterior to the pons.

• Optic chiasm: Superior/anterior to the pituitary gland.

• Mammillary body: Inferior aspect of the hypothalamus.

• Midbrain: Superior to the pons.

• Pons: Between the midbrain and medulla.

• Medulla: Inferior to the pons.

• 4th ventricle: Between the pons/rostral medulla and cerebellum.

• Cerebellum: Posterior to the brainstem.

• Foramen magnum: Opening where the medulla continues toward the spinal cord.

done

What is the reticular formation (RF)?

R=really important: basic life functions; alertness and vital autonomic functions.

-The portion of brainstem tegmentum where clearly defined nuclei are generally not visible with conventional staining

What do the rostral and caudal reticular formation (RF) primarily regulate?

superior: Rostral RF: alertness; (head)

inferior: Caudal RF: respiration and circulation (back= lungs/heart)

what is Neuromodulation:

Either facilitate or inhibit neurotransmission.

What is the difference between neurotransmission and neuromodulation?

Neurotransmission communicates signals between neurons;

neuromodulation facilitates or inhibits signaling over broader circuits.

NE, serotonin, histamine, dopamine, Ach neurotransmitters are mainly…

neuromodulatory

Which major CNS neurotransmitters mediate fast excitation and inhibition?

Glutamate (excitatory) and GABA (inhibitory).

Associated brain region and function of:

Norepinephrine (NE)

-Locus coeruleus (pons) produces it

-mostly excitatory effects on thalamus

-fx: Modulates attention, sleep-wake states and mood

Associated brain region and function of:

Serotonin

-Rostral raphe nucleus (brainstem):

Mood regulation, sleep-wake cycle

-depression, anxiety, OCD

-Caudal raphe nucleus: pain modulation, breathing, temperature regulation

Associated brain region and function of:

dopamine

-Substantia nigra and ventral tegmental area (midbrain)

-Reward, motivation, pleasure, movement, attention, working memory

-Parkinson's and hallucinations in schizophrenia

Associated brain region and function of:

histamine

-Tuberomammillary nucleus (hypothalamus)

-Wakefulness, arousal, attention, appetite suppression

What are the major functional cerebellar divisions?

1. Vermis,

2. intermediate hemispheres,

3. lateral hemispheres,

4. flocculonodular lobe.

What does the vermis control?

Trunk and proximal limb coordination; gait and posture.

What does the intermediate hemisphere control?

distal limb coordination

what does the lateral hemisphere control:

motor planning for extremities

What does the flocculonodular lobe control?

Vestibular functions (body balance & involuntary eye movements)

-eyes automatically move to contralateral side of head turn to maintain fixation of target (doll’s head)

Which cerebellar areas regulate saccades and smooth pursuit?

saccades: Vermis and fastigial nucleus:

smooth pursuit: flocculus (birds are smooth)

What enters the cerebellum through the inferior cerebellar peduncle (ICP)?

(3 INs) INferior CP receives INput INferiorly from:

1. Inferior olive: Motor learning

2. Spinal cord: Proprioception(where body is)

3. Vestibular nuclei: (where head is)

-also contains output from cerebellum to the vesti. nuclei

What enters the cerebellum through the middle cerebellar peduncle (MCP)?

• Input from contralateral pontine nuclei: (what the brain wants to do)

• Carries planned movement information from the cerebral cortex via the corticopontocerebellar pathway

Output from cerebellum is through…and what does it do

SCP (Superior Cerebellar Peduncle)

-SCP outputs to thalamus, which relays to the motor cortex

What is the major output pathway from the cerebellum?

Cerebellum → SCP → Thalamus → Motor cortex

Where do superior cerebellar peduncle fibers (SPC) decussate?

Midbrain at the level of the inferior colliculi.

Which deep cerebellar nuclei receive input from which regions?

Fastigial–vermis; interposed (emboliform/globose)–intermediate hemispheres; dentate–lateral hemispheres.

What is the exception to deep cerebellar nuclear output?

Flocculonodular lobe mainly projects directly to vestibular nuclei.

What is Chiari I malformation?

Downward displacement of cerebellar tonsils through foramen magnum, typically due to a congenitally small posterior fossa or pressure imbalance that pushes the cerebellum downward.

-cerebellum tonsil droops down thru foramen magnum, causing pressure

What visual/ocular findings can occur in Chiari I malformation?

1. Nystagmus (gaze-evoked most common; downbeat more characteristic/specific).

2. Sixth nerve palsy. (compressed abducens nerve= esotropia

3. Papilledema

4. Acute acquired comitant esotropia.

what is papilledema

the swelling of the optic disc caused by increased intercrainial pressure

what is Acute acquired comitant esotropia

a sudden-onset eye misalignment where one or both eyes turn inward (crossed) by an equal angle in all directions of gaze, frequently causing double vision (diplopia)

What is downbeat nystagmus, and where does it localize?

-a pathologic upward slow drift followed by corrective downward saccade; looks like nodding pupils

- localizes to cervicomedullary junction (e.g., Chiari I).

What are nystagmus and oscillopsia?

Nystagmus: uncontrolled repetitive eye movements;

oscillopsia: oscillating or moving environment.

Corticopontocerebellar fiber pathway:

1. Cerebral cortex →

2. anterior pons (pontine nuclei) →

3. cross the midline in the anterior pons →

4. contralateral cerebellum via MCP.

where is SCP decussation:

• Midbrain at the level of the inferior colliculi.

-Cerebellum–vestibular system communication thru__

-also contains output from____

-ICP;

-output from cerebellum to vestibular nuclei.

most cerebellar output is conveyed thru the…

deep cerebellar nuclei

The flocculonodular lobe projects primarily to the——, bypassing the——-

-vestibular nuclei

-deep cerebellar nuclei.\

what are the structures of the deep cerebellar nuclei and where do they receive input from?

Don’t Eat Greasy Food

1. Dentate- Lateral cerebellar hemisphere

2. Interposed (emboliform, globose)- Intermediate hemisphere

3. Fastigial-Vermis and small input from flocculonodular lobe

What is the vestibulo-ocular reflex (VOR)?

A gaze-stabilizing reflex during head movement.

-To maintain visual fixation on a target, eyes move in the opposite direction of the head movement. (doll’s head)

VOR is mediated by the …

flocculus and nodulus, the vestibular portion of the cerebellum

-flock=birds have stable head/eye movement

Which cerebellar structures control VOR, and what happens if damaged?

Flocculus/nodulus; inaccurate VOR causes unstable vision during head movements.

--flock=birds have stable head/eye movement

Why do unilateral cerebellar lesions cause ipsilateral signs?

Cerebellar motor circuit input/output are either ipsilateral or double-crossed.

describe and localize the lesion of:

truncal ataxia

-wide-based, unsteady, “drunk-like” gait; often unable to stand with feet together with eyes open

-vermis

describe and localize the lesion of:

Appendicular ataxia

-abnormal finger-nose-finger or heel-shin test;

-ataxia of limbs are ipsilateral to lesion

-lesion Lateral to vermis

What may occur in vestibular dysfunction and what structure is affected

-nystagmus, vertigo, postural instability; nausea/vomiting and oscillopsia

-Flocculonodular lobe

damage in what structures are involved in abnormal/inaccurate saccades

Vermis and fastigial nucleus

damage to what structures are involved in Abnormal smooth pursuit

Flocculus

Are ataxia and nystagmus specific to cerebellar lesions?

No; vestibular, proprioceptive and brainstem disorders can also cause them.

-Nystagmus may result from peripheral vestibular disorders or brainstem/cerebellar lesions.

-Ataxia may result from cerebellar dysfunction, impaired proprioception, or vestibular dysfunction.

cerebellar lesions can cause:

Speech problems

-Scanning or explosive speech (irregular fluctuations in rate and volume) or slurred speech

1. The tectum is also called

2. What comprises the midbrain tectum (aka:——)?

1. quadrigeminal plate

2. (corpora quadrigemina): composed of 4 bumps in the back: 2 superior and 2 inferior colliculi

What do superior vs inferior colliculi mediate?

Superior: visual orienting reflex center

inferior: auditory orienting reflex center

Superficial layers of superior colliculus receive…

DIRECT RGC axonal input.

Deeper layers of the superior collicus have…

Sensory (visual, auditory, somatosensory) and motor functions.

Some RGC axons branch off the optic tract to project to the superior colliculus and pretectal nucleus via the…

Brachium of superior colliculus

What is the brachium of the superior colliculus?

Pathway conveying retinal axons from the optic tract to superior colliculus/pretectal area.

How do tectobulbar and tectospinal pathways differ?

Tectobulbar projects to cranial motor nuclei (eye, lids, head); tectospinal to spinal cord for orienting movements.

Describe the Orientation reflex pathway of the:

tectobulbar

Superior (& inferior colliculus) → CN nuclei.

[contralateral motor nuclei of CN:]

• Eyelid closures (CN 7 facial).

• Eye movement (CN 3, 4, 6-oculomotor, trochlear, abducens).

-bulbar=brainstem

Describe the Orientation reflex pathway of the:

Tectospinal:

Superior (& inferior colliculus) → spinal cord.

[motor neurons of anterior gray columns of spinal cord]

• Body movements (C5 →).

What is the crus cerebri (basis pedunculi)?

Ventral midbrain descending fiber bundle containing corticospinal, corticobulbar and corticopontine fibers.

What are the 4 important nuclei in the midbrain?

Red, oculomotor, Edinger–Westphal, and trochlear nuclei.

Where are the midbrain nuclei relative to the cerebral aqueduct?

Ventral to the aqueduct, within tegmentum.

At what levels are the CN III and CN IV nuclei located?

CN III/Edinger–Westphal: superior colliculus; CN IV: inferior colliculus.

What is a major function of the red nucleus?

Motor coordination via connections with the cerebellum (motor modulation).

Which muscle is innervated by the trochlear nucleus versus the trochlear nerve?

Nucleus: contralateral superior oblique; exiting nerve: ipsilateral superior oblique.

What are the four CN III segments in order?

Fascicular, subarachnoid (cisternal), intracavernous, intraorbital.

Where does CN III exit the brainstem and travel in the subarachnoid space?

Exits ventral midbrain between cerebral peduncles; courses near PCA and PCom before cavernous sinus.

Which structures occupy the cavernous sinus?

CN III, IV, V1, V2, VI, cavernous internal carotid artery, and sympathetic fibers.

Which nerves are in the lateral wall of the cavernous sinus?

From superior to inferior: CN III, IV, V1, V2 (CAT OTOM mnemonic).

Which nerve runs beside the internal carotid artery within the cavernous sinus?

CN VI; sympathetic fibers travel with the carotid/VI.