Week 22 Brain Stem Flashcards
Long-tract findings
Motor or sensory symptoms in the extremities.
What do you suspect if your have CN deficits and long-tract findings?
Brainstem lesion
Brainstem rule of 4 for latitude
Midbrain/above : I, II, III, IV
Pons: V, VI, VII, VIII
Medulla: IX, X, XI, XII
Brainstem rule of 4 for longitude
Mediat tract = MOTOR:
Motor tracts
Medial Lemniscus (not motor, but M)
Median longitudinal fasciculus
Motor nuclei (III, IV, VI, XII)
Side (lateral tract) = SENSORY:
Spinothalamic
Spinocerebellar
Sensory nucleus CN V
Sympathetic pathway
What is the pneumonic for ocular mm innervation?
SO4, LR6, all the rest are 3
What is the pupil rule for CNIII palsies?
Pupil involvement with other CN III symptoms is usually d/t compressive lesion (aneurysm) rather than ischemia.
Alexander’s Law
Tells you the direction the nystagmus will be worse.
Name the nystagmus for the fast phase (eg down beat = fast phase down).
Slow phase is the pathologic portion (eg slow drift upward is pathologic, down beat is corrective saccade).
Therefore when you look in the direction where the problem is, the nystagmus will be worse.
Red flags for headaches
S Systemic symptoms
N Neuro symptoms
O Older age
O Onset
P Pattern change, pregnancy, positional, progressive
What structures pass through the optic canal?
Optic nerve
Opthalmic artery
What structures pass through the superior orbital fissure?
CN III, IV, VI
Nasociliary nerve
Lacrimal nerve
Frontal nerve
Opthalmic vein
**Tendonous ring
What structures pass through the inferior orbital fissure?
Infraorbital nerve (branch of CN V2)
Zygomatic nerve
What structures pass through the supraorbital fissure?
Supraorbital nerve
What structures pass through the infraorbital foramen?
Infraorbital nerve (branch of CN V2)???????
What structures are located in the fossa of lacrimal sac?
Nasolacrimal duct
Which artery supplies blood to almost all of the structures of the orbit, extraocular mm, and lacrimal gland?
Opthalmic artery
How is blood drained from the orbital region?
Through the opthalmic vein to the cavernous sinus.
Describe blood flow to the eye from the internal carotid
Internal carotid ->
Opthalmic artery ->
-lacrimal
-central retinal
-posterior ciliary
-supraorbital
What are the functions of the fat found within the orbital area?
- Stabilize position of the eyeball
- Acts as a socket for eyeball to rotate in.
Classic sign of hyperthyroidism
Exopthalmus.
Volume of orbital fat increases, causing eyeball to protrude outward (proptosis).
How can starvation affect the appearance of the eye?
Loss of orbital fat causes eye sockets to look hollow.
Discuss orbital fracture
Floor of orbit is extremely thin.
Can be fractured by blunt force trauma.
Inferior rectus and orbital fat may prolapse into maxillary sinus.
What is the function of Opthalmic nerve/CN V1?
Sensory from upper eyelid, cornea, conjunctiva, forehead, and scalp.
What is the pathway of the opthalmic nerve/CN V1?
Branches from the trigeminal ganglia and middle cranial fossa via superior orbital fissure.
What does the opthalmic nerve/CN V1 branch into?
Frontal nerve
Nasociliary nerve
Lacrimal nerve
Ciliary ganglion, CN III, and CN V
CN V1 sympathetic fibers -> ciliary ganglion **Synapse-> short ciliary nerves.
CN III parasympathetic fibers -> ciliary ganglion **Synapse -> short ciliary nerves.
Sensory fibers from eyeball through ciliary ganglion into CN V1 **No synapse.
Corneal blink reflex
Poke eye
Opthalmic nerve -> Trigeminal sensory nucleus -> Facial motor nucleus -> Facial nerve -> Orbicularis oculi muscle.
What does sympathetic innervation to the head result in?
Dilator pupillae.
Superior tarsal mm in eye.
Sweating when in hot environment.
Dilation of vessels in skin when in hot environment/emotion.
Constriction of vessels inside the skull.
Horner Syndrome
Loss of sympathetic innervation to the head:
Miosis (pupillary ctx)
Ptosis
Anhidrosis
Absence of flushing
Conjunctival injection (dilation of the vessels in the conjuctiva.
Components of the lacrimal apparatus
Lacrimal glands
Lacrimal ducts
Lacrimal canaliculi
Lacrimal sac
Nasolacrimal duct
What are the 4 supranuclear gaze systems?
Saccadic
Pursuit
Vergence
Non-optic reflex
Saccadic movements
Fast voluntary mvmts.
Contralateral frontal cortex.
Projects via internal capsule to brain stem gaze centres.
Commonly affected (MCA stroke),
Bilateral lesions = vertical gaze impairment.
Clinical: movement between targets on command.
Pursuit movements
Slow, involuntary mvmts.
Occipital-parietal cortex.
Tracks a moving object.
Project via internal capsule to brain stem.
Impairment results in “cogwheel” pursuit.
Clinical: tracking a slowly moving target.
Vergence
Slow disconjugate mvmts.
Occipital-parietal to mid brain pre-tectum.
Allows near focus.
Clinical: shift from distant to near.
Non-optic reflex
Slow eye mvmts.
Vestibular nuclei in medulla.
Inputs from labyrinth and neck.
Maintains fixation w/head mvmt.
Clinical: oculocephalic reflex and caloric responses.
Supranuclear anatomy
Frontal gaze centre.
Occipital gaze centre.
Descending pathways to brain stem.
Vergence centre.
Vertical gaze centre.
Horizontal gaze centre.
MLF.
Oculomotor nuclei
CN III oculomotor complex
CN IV trochlear nucleus
CN VI abducens nucleus
Oculomotor complex
CN III
Superior, medial, inferior, inferior oblique mm.
Levator palpabrae.
Parasympathetics to pupil and ciliary ganglion.
When is a CN III palsy never nuclear?
Unilateral ptosis and mydriasis (dilation).
Trochlear nuclei
Superior oblique.
Depresses and abducted eye.
Intorsion of abducted eye.
Abducens nuclei
Lateral rectus.
Abducts eye.
Infranuclear nerves
III, IV, VI
Progressive supranuclear palsy
Gradual impariment of supranuclear gaze.
Vertical > Horizontal.
Voluntary > Pursuit > Reflex.
Axial dystonia.
Dementia.
Dorsal midbrain syndrome
Vertical gaze palsy.
Light near dissociated pupils.
Lid retraction or ptosis.
Convergence-retraction nystagmus.
INO
Ipsilateral adduction weakness.
Contralateral abduction nystagmus.
MLF
Third nerve palsy/Oculomotor nerve palsy
Double vision d/t affected eye lacking adduction.
Ptosis.
Relative afferent pupillary defect.
