Autonomic nerves and visual deficits Flashcards
What things does the autonomic nervous system control in the eye?
Intrinsic muscles of the eye
Vasomotor function
Secretion of tears
Sweat glands of the face
What is the 3 neuron pathway?
1st part= hypothalamus
2nd order neurons arise in brainstem and intermediolateral cell column of spinal cord
Synpases with 3rd order neurons which are outside the central nervous system
What are the key functions of the hypothalamus?
Detects changes in internal and external environment
Sexual activity
Endocrine secretion
Posterior- SNS Anterior-PNS
Where is the hypothalamus?
Anterior and lateral walls of 3rd ventricle Extends anteriorly to lamina terminalis Inferiorly to mammillary bodies Superior border=hypothalamic sulcus Lateral border=internal capsule
What are the nuclei of the hypothalamus?
Anterior group (supraoptic, paraventricular and suprachiasmatic) Middle group (tuberal, ventromedial, dorsomedial, lateral and arcuate) Posterior group (mamillary and posterior)
Where does the hypothalamus receive afferent connections?
Limbic Cortex Globus pallidus Amygdala Retina (influences photoendocrine function eg circadian rhythms) Brainstem Spinal cord
Where does the hypothalamus send its efferent connections?
Mamillothalaic tract
Periventricular nuclei
Supropticohypophyseal tract
What is the blood supply to the hypothalamus?
Anterior communication artery
Posterior communicating artery
Posterior cerebral artery
Venous drainage via internal cerebral vein
What is special about the PNS?
Tends to respond rapidly and locally
Less extensive than CNS
Ganglions are close to end organs
Cranial cervical and sacral outflow
Which 4 nuclei influence the eye?
Edinger Westphal nucleus (PNS)
Superior salivatory (PNS)
Inferior salivatory (PNS)
Superior cervical ganglion (SNS)
Which 4 ganglions influence the eye?
Ciliary (to the sphincter pupillae)
Pterygopalatine (to palate and lacrimal gland)
Submandibular (to floor of mouth)
Otic (to parotid)
All contain sensory, SNS and PNS but only PNS synapse
What are the differences between pre and post ganglionic fibres?
Preganglionic: cholinergic and myelinated
Postganglionic: unmyelinated (except short ciliary nerves), PNS fibres are cholingeric, SNS fibres are adrenergic
How are the fibres arranged in the occulomotor nerve?
CN III is parasympathetic
Cells associated with pupiloconstriction are located on more superficially and dorsomedially than those associated with ciliary contraction and accomodation
Describe the CN III pathway from ciliary ganglion
8-10 branches leave ciliary ganglion and divide into 15-20 short ciliary nerves (myelinated)
95% innervated ciliary muscle-> accommodation
5% innervate sphincter pupillae -> pupiloconstriction
What is the afferent stimulus to the edinger westphal nucleus?
Pupillary light reflex
Simultaneous and equal constriction to pupils in response to light
Synapse in pretectal nucleus
What is the pretectal nucleus?
Collection of small cells anterior to lateral margin of superior colliculus
Retinal fibres end in dorsomedial part so in dorsal compression there is loss of the light reflex but preservation of the near reflex ( Parinaud’s syndrome)
In light -near -dissociation which response is damaged?
Always the light response
What happens to parasympathetic fibres in the pretectal nucleus?
Decussate around periaquaductal grey matter
Half travel via posterior commisure to contralateral EWN
Half travel via medial longitudinal bundle to ipsilateral EWN
Which reflexes travel via cranial nerve III and EWN?
Pupillar light reflex
Accommodation convergence reflex (also with CNVI)
What is Adie’s syndrome and what causes it?
Pupillary response to light decreased/slow but accommodation is intact (absent acutely but recovers with abberant reinnervation of sphincter fibres)
Secondary to ciliary ganglionitis
90% have absent tendon reflexes but no peripheral neuropathy
Demonstrated with pilocarpine (anticholinergic)
Describe the course of parasympathetic fibres with the facial nerve
Start in superior salivatory nucleus-> CN VII exits pons -> geniculate ganglion (no synapse) -> facial canal of temporal bone -> splits into 2;
Some go via greater petrosal nerve-> medial cranial fossa.-> between 2 layers of dura-> foramen lacerum-> pterygopalatine ganglion
Some go via chorda tympani-> pars flaccida-> lingunal nerve-> submandibular ganglion
Where does the ptergopalatine ganglion send fibres to?
Via maxillary nerve-> zygomatic nerve-> zygomaticotemporal nerve-> lacrimal gland
Via rami orbitales-> cavernous sinus->retro-orbital plexus-> rami oculares-> superior orbital fissure-> ophthalmic +ciliary arteries
Why does intraocular pressure drop when the greater petrosal nerve/pterygopalatine ganglion is damaged?
All main orbital arteries are supplied by retroorbital plexus
Run in adventitia
10% are SNS but most are PNS (vasodilator)
What are the afferents to the superior salivary nucleus?
Nucleus of solitary tract (salivation to taste)
Nucleus of trigeminal nerve (tearing to eye irritation)
Limbic system (emotional tearing)
What role does CN IX have in the PNS?
Transports PNS to parotid gland (auricotemporal nerve), oropharynx (pharyngeal branch) and posterior 1/3 of tongue (lingual branch)
Where do primary neurons run in the SNS?
First order: hypothalamus-> midbrain -> inferior cerebellar peduncle-> lateral spinothalamic tract -> lateral part of ventral reticular formation and intermediolateral colums of cervical cord
Where do secondary neurons run in the SNS?
Arise in intermediolateral column (dilator centre of budge and waller)
Fibres to eye are T1
Travel through white rami to sympathetic trunk through stellate ganglion (no synapse) lies within C7 transverse process and the neck of the 1st rib
Ansa subclavia-> enclose subclavian artery-> inferior + middle cervical ganglion (no synapse)-> super cervical ganglion (synapse)
Then forms internal carotid nerve
Where is the superior cervical ganglion?
Between internal jugular vein and internal carotid artery
Where do 3rd order neurons run in the SNS?
Internal carotid nerve-> internal carotid plexus, splits into several branches;
Deep petrosal nerve/nerve of pterygoid canal
Branch for trigeminal ganglion,
Branch for abducens nerve
Branch for trochlear nerve
Branch for ophthalmic nerve/ nasociliary nerve
Short ciliary nerves
Branch for oculomotor> inferior orbital foramen -> Mullers muscle
Where do the corticotympanic nerves run?
Posterior wall of carotid canal gives off these nerves, they join tympanic plexus in the middle ear and joined by tympanic branch of CN IX rejoins the carotid plexus
What does the cavernous plexus supply?
SNS
Fibres are given to all nerves who enter
Goes to V1, and nasociliary nerve-> long ciliary nerve-> pupillodilator
What does the SNS twig to ciliary ganglion do?
Become short ciliary nerves (vasoconstrictor to blood vessels and innervate melanocytes of uvea)
And joins ophthalmic artery and CN III and mullers muscle
What are the external carotid fibres?
Post ganglionic fibres destined for facial structures
Where do 1st order neurons synapse?
Travel down midbrain, pons, cerebellum and spinal cord to synapse at intermediolateral nucleus of lower cervical and upper thoracic spinal cord
Describe the course of the deep petrosal nerve as it comes off the internal carotid plexus
Deep petrosal nerve becomes known as nerve of pterygoid canal, enters the pterygopalatine ganglion but does not synapse, joins the zygomatic nerve then the lacrimal nerve to supply the lacrimal gland
Describe the course of the ophthalmic branch of the internal carotid plexus
Joins the nasociliary nerve + enters the orbita via superior orbital fissure
Then becomes long ciliary nerve which supplies cornea, iris and ciliary body
Which receptors are present in the smooth muscle of sphincter pupillae?
Alpha 1 adrenoceptors
Atropine/phenylephrine dilate pupil by acting as sympathetic stimulants
What type of visual loss occurs with damage to the optic nerve?
Almost any kind of unilateral field loss
Optic neuritis: 48% diffuse visual loss, 20% altitudinal, 8% cecocentral
Peripheral field constriction with preservation of colour and vision= nerve sheath process
What type of visual loss occurs with damage to the optic chiasm?
Bitemporal loss, commonly incomplete and asymmetrical
Depends on pre/post fixed pituitary gland
Pre-fixed: homonymous hemianopia with central loss
Post fixed: Uniocular loss with RPAD
Lesion at junction of optic nerve and chiasm: junctional scotoma
Inferior chiasm: superior bitemporal field loss
Superior chiasm: Inferior bitemporal field loss
What is Wilbrand’s knee?
Junction of optic nerve and chiasm
Fibres from inferonasal retina and contralateral eye loop anteriorly in the ipsilateral optic nerve
What is band atrophy?
Temporal nerve fibres insert superiorly and inferiorly at the optic disc
Nasal fibres insert laterally to the optic disc
Nasal fibres are the temporal visual field
In bitemporal field defect, the nasal fibres of the optic disc atrophy
Causes band/bowtie pattern of atrophy
What are the other symptoms of a compressive lesion at the optic chiasm?
Hemi field slide- breakdown of phoria
Post fixational blindness
What are some causes of optic chiasm lesions?
Internal carotid artery aneurysm
Cavernous sinus mass
Meningiomas
Tuberculoma
What type of visual loss occurs with damage to the optic tract?
Incongrous homonymous hemianopia
Contralateral to lesion
More posterior the lesion the more congruous the field loss
What type of visual loss occurs with damage to the lateral geniculate nucleus?
Sectoranopia but very variable
What type of visual loss occurs with damage to the optic radiation ?
Temporal:Classically in Meyer’s loop. Pie in the sky wedge defect
Parietal: incomplete homonymous hemianopia more dense in lower quadrants
What type of symptoms occur with damage to the temporal lobe?
Auditory, memory processing
Contralateral hemisensory disturbance and mild hemiparesis
Taste smell and visual hallucinations
Complex partial seizures
Receptive dysphasia-wont understand instructions
What type of symptoms occur with damage to the parietal lobe?
Acalculia Agraphia Left-right disorientation Finger agnosia Spatial neglect
What type of symptoms occur with damage to the occipital lobe?
Congrupus homonymous hemianopia
Macular area has dual blood supply so is often spared in infarct (posterior cerebral and middle cerebral artery)
Unformed visual hallucinations
Denial of blindness (anton’s syndrome)
Charles Bonnet syndrome -formed or unformed hallucinations
What is posterior cortical atrophy?
Dementia beginning with visual symptoms
Difficulty reading and depth perception
Distortion of color and images
Get lost in familiar environments
What occurs with lesions of visual association cortex>
Inability to name objects, recognise faces
