The ciliary ganglion is a parasympathetic ganglion located just
behind the eye in the posterior orbit. It measures 1–2 millimeters in diameter
and in humans contains approximately 2,500 neurons. The oculomotor nerve
coming into the ganglion contains preganglionic axons from the
Edinger-Westphal nucleus which form synapses with the ciliary neurons. The
postganglionic axons run in the short ciliary nerves and innervate two eye
muscles: the sphincter pupillae constricts the
pupil, a movement known as Miosis. The opposite, Mydriasis, is the dilation of
the pupil. the ciliaris contracts, releasing
tension on the Zonular Fibers, making the lens more convex, also known as
accommodation. Both of these muscles are involuntary –
they are controlled by the autonomic nervous system.
It is one of four parasympathetic ganglia of the head and neck..
Anatomy Three types of nerve fibers run through
the ciliary ganglion: parasympathetic fibers, sympathetic fibers and sensory
fibers. Only parasympathetic fibers form synapses in the ganglion. The other two
types of nerve fibers simply pass through. In classical anatomy, the
ciliary ganglion is said to have three “roots:”
a parasympathetic root of ciliary ganglion
a sympathetic root of ciliary ganglion a sensory root of ciliary ganglion
Diseases = Adie tonic pupil=
Diseases of the ciliary ganglion produce a tonic pupil. This is a pupil that does
not react to light and has an abnormally slow and prolonged response to attempted
near vision. When a patient with an Adie pupil
attempts to focus on a nearby object, the pupil constricts slowly. On close
inspection, the constricted pupil is not perfectly round. When the patient
focuses on a more distant object, the pupil remains constricted for several
minutes, and then slowly dilates back to the expected size.
Tonic pupils are fairly common – they are seen in roughly 1 out of every 500
people. A patient with anisocoria whose pupil does not react to light most
likely has Adie syndrome – idiopathic degeneration of the ciliary ganglion.
Physiology The strange behavior of tonic pupils was
first explained by Irene Loewenfeld in 1979. The ciliary ganglion contain many
more nerve fibers directed to the ciliary muscle than nerve fibers
directed to the constrictor pupillae – roughly twenty times more. The ciliary
muscle is also more massive than the constrictor pupillae, again by a factor
of twenty. Based on these observations, Loewenfeld proposed an explanation of
the tonic pupil. She noted that pathological destruction of nerve cells
in the ciliary ganglion that is found in all cases of Adie pupil. In her own
words: Let’s say that in a given fresh Adie’s
pupil, a random 70% of the cells in the ciliary ganglion stop working; and that,
in a couple of months, these neurons re-grow and randomly re-innervate both
intraocular sphincters. Some parasympathetic light-reaction neurons
that were originally destined for the iris sphincter will end up innervating
the ciliary muscle. But there will not be enough of them to budge that big
muscle, so there will be no detectable accommodation with exposure to light.
The other way around, it is a different story. There will be plenty of
accommodative neurons re-growing into the iris sphincter, and it won’t take
very many of them to make a little muscle like the iris sphincter contract.
This means that every time the patient accommodates her gaze to a near object,
some of the innervation to the ciliary muscle will spill over into the iris and
constrict the pupil. Loewenfeld’s theory is now generally
accepted. It explains the defining features of a tonic pupil:
(1) The pupil does not react to light. The original light-reaction neurons have
been destroyed. (2) Tonic constriction with attempted
near vision. Aberrant regeneration of nerve fibers intended for the ciliary
muscle causes abnormal, tonic contraction of the pupil with
accommodation. (3) Segmental iris constriction. When
carefully examined under magnification, the iris does not constrict uniformly
with attempted near vision. Only the re-innervated segments contract,
producing a slightly irregular contour to the pupil.
(4) Denervation supersensitivity. Like any denervated muscle, the iris becomes
supersensitive to its normal neurotransmitter. Very weak solutions of
cholinergic substances such as pilocarpine cause the denervated iris to
constrict. Tonic pupils are usually due to Adie
syndrome, but other diseases can denervate the ciliary ganglion.
Peripheral neuropathies occasionally produce tonic pupils. Herpes zoster
virus can attack the ciliary ganglion. Trauma to the orbit can damage the short
ciliary nerves. Anything that denervates the ciliary ganglion will produce a
tonic pupil due to aberrant nerve regeneration.
= Adie syndrome= Adie syndrome is tonic pupil plus absent
deep tendon reflexes. Adie syndrome is a fairly common, benign, idiopathic
neuropathy that selectively affects the ciliary ganglion and the spinal cord
neurons involved in deep tendon reflex arcs. It usually develops in middle age,
although it can occur in children. A variant of Adie syndrome, Ross syndrome,
affects sweating as well. Early in the course of Adie syndrome the
pupil will be fixed and dilated. The sphincter pupillae will be paralyzed.
There will be no response to accommodation – the ciliary muscle is
also paralyzed. With aberrant nerve regeneration, the
pupil will remain fixed, but it will constrict with attempted near vision.
The constriction will be abnormal. Late in the course of Adie syndrome, the
pupil becomes small. It will still be “fixed” and it will continue to show
abnormal, tonic constriction with attempted near vision.
= Light-near dissociation= In some neurological disorders, the
pupil does not react to light, but it does react to accommodation. This is
called “light-near dissociation”. In Adie syndrome, damage involving the
ciliary ganglion manifests light-near dissociation and a tonically dilated
pupil. Other causes of light-near dissociation
involve damage to the brainstem, where a tonic pupil is not produced. Brainstem
causes of light-near dissociation include Argyll Robertson pupil and
Parinaud syndrome. Irene Loewenfeld is generally credited
for being the first physiologist to make this distinction.
References ^ Perez, GM; Keyser, RB. "Cell body
counts in human ciliary ganglia.". Investigative ophthalmology & visual
science 27: 1428–31. PMID 3744735. ^ Kawasaki, A. "Physiology, assessment,
and disorders of the pupil.". Current opinion in ophthalmology 10: 394–400.
doi:10.1097/00055735-199912000-00005. PMID 10662243.
^ Thompson, HS; Kardon, RH. "Irene E. Loewenfeld, PhD Physiologist of the
pupil.". Journal of neuro-ophthalmology : the official journal of the North
American Neuro-Ophthalmology Society 26: 139–48.
doi:10.1097/01.wno.0000222970.02122.a0. PMID 16845317.
^ Thompson, HS. "Adie's syndrome: some new observations.". Transactions of the
American Ophthalmological Society 75: 587–626. PMC 1311565. PMID 613531.
Additional images External links
Anatomy figure: 29:03-04 at Human Anatomy Online, SUNY Downstate Medical
Center - "A deeper dissection of the right orbit from a superior approach."
Atlas image: n2a4p2 at the University of Michigan Health System - "Branches of
Trigeminal Nerve, Lateral View" Cell Centered Database - Ciliary
ganglion lesson3 at The Anatomy Lesson by Wesley
Norman cranialnerves at The Anatomy Lesson by
Wesley Norman