The anatomy and its relations of the various
portions of the third cranial nerve accounts
for the clinical features of third cranial nerve
1)Nuclear portion: situated in the midbrain.
2)Fascicular portion : situated ventrally to the mid brain
3)Fascicular subarachnoid portion: situated anterior to the
midbrain and in close proximity to the posterior
4)Fascicular cavernous sinus portion:
Runs through the lateral wall of the cavernous sinus and
enters the cavernous sinus
5)Fascicular orbital portion: situated in the posterior part
of the orbit
oIII portion: Fascicular subarachnoid portion:
Clinical significance: Berry aneurysm
at the junction between the posterior
communicating artery and the internal
oIV Portion: Fascicular cavernous sinus portion:
Clinical significance: Masses invading
the cavernous sinus are likely to cause third
cranial nerve dysfunction
1. direct trauma,
2. demyelinating diseases (e.g., multiple sclerosis)
3. increased intracranial pressure (leading to uncal herniation)
1. due to a space-occupying lesion (e.g., brain cancer) or a
2. spontaneous subarachnoid haemorrhage (e.g., berry
4. microvascular disease, e.g., diabetes.
1) Diplopia from misalignment of the visual axes
2) Symptomatic Glare in bright light (if the ptotic lid does
not cover the pupil)
1) Involved eye usually is deviated down and out
2) Ptosis (differentiated from myasthenia gravis by
3) Pupillary Dilatation
4) Paralysis of Accommodation causes blurred
vision for near objects
1) Symptomatic cases can be treated with
2) Surgical correction of Ptosis: Ptosis surgery
Innervation: the Superior oblique muscle
1) Primarily Intort the eye (such that the top of the eye
rolls toward the nose),
2)Secondary actions of depression (down gaze) and
abduction (looking away from the nose).
Clinical features in Palsy:
1) The affected eye Extorts,
2) Deviate Upwards (Hypertropia),
3) Drift Inward.
Aetiologyof IV Cranial Nerve Palsy:
1) Usually neurogenic
2) Dysgenesis of the IV CN nucleus or nerve,
3) Clinically similar palsy may result from
absence or mechanical dysfunction
(e.g., abnormal laxity) of the superior oblique tendon
Congenital IV cranial nerve palsy:
1) It may not become symptomatic until later
childhood or adulthood.
2) Young children adopt a compensatory
position head tilt (Torticollis) in order to
compensate for the underacting superior
oblique muscle (towards contralateral side)
3) Facial asymmetry due to chronic head tilt.
4) Vertical diplopia
1) Lack of subjective symptoms of torsion
(Torsion -rotation of vertical corneal meridians)
- following Cataract surgery
- manifest transiently during pregnancy
3) Neck Pain after years of head tilting.
1. Symptomatic cases can be
treated with Strabismus surgery
2. Prism lenses set to make minor
optical changes in the vertical
alignment may be prescribed
instead of or after surgery to fine-tune
Isolated lesions of the VI nerve nucleus will not give rise to an isolated VIth neve palsy because
paramedian pontine reticular formation fibers pass through the nucleus to the opposite IIIrd nerve
nucleus. Thus, a nuclear lesion will give rise to an ipsilateral gaze palsy. In addition, fibers of the seventh
cranial nerve wrap around the VIth nerve nucleus, and, if this is also affected, a VIth nerve palsy with
ipsilateral facial palsy will result. In Millard Gubler syndrome, a unilateral softening of the brain tissue
arising from obstruction of the blood vessels of the pons involving sixth and seventh cranial nerves and
the corticospinal tract, the VIth nerve palsy and ipsilateral facial paresis occur with a contralateral
hemiparesis.. Foville's syndrome can also arise as a result of brainstem lesions which affect Vth, VIth and
VIIth cranial nerves.
2. Sub arachnoid space
As the VIth nerve passes through this space it lies adjacent to anterior inferior and posterior inferior
cerebellar and basilar arteries and is therefore vulnerable to compression against the clivus. Typically
palsies caused in this way will be associated with signs and symptoms of headache and/or a rise in ICP.
3. Petrous Apex
The nerve passes adjacent to the mastoid sinus and is vulnerable to mastoiditis, leading to inflammation
of the meninges, which can give rise to Gradenigo's syndrome. This condition results in a VIth nerve palsy
with an associated reduction in hearing ipsilaterally, plus facial pain and paralysis, and photophobia.
Similar symptoms can also occur secondary to petrous fractures or to nasopharyngeal tumours.
4. Cavernous sinus/Superior orbital fissure
The nerve runs in the sinus body adjacent to the internal carotid artery and oculo-sympathetic fibres
responsible for pupil control, thus, lesions here might be associated with pupillary dysfunctions such as
Horner's syndrome. In addition, III, IV, V1, and V2 involvement might also indicate a sinus lesion as all run
toward the orbit in the sinus wall. Lesions in this area can arise as a result of vascular problems,
inflammation, metastatic carcinomas and primary meningiomas.
The VIth nerve's course is short and lesions in the orbit rarely give rise to isolated VIth nerve palsies, but
more typically involve one or more of the other extraocular muscle groups.
The first aims of management should be to identify
and treat the cause of the condition, where this is
possible, and to relieve the patient's symptoms, where
present. In children, who rarely appreciate diplopia,
the aim will be to maintain binocular vision and, thus,
promote proper visual development.
Thereafter, a period of observation of around 9 to 12
months is appropriate before any further intervention,
as some palsies will recover without the need for
Fresnel prisms: slim flexible plastic prisms can be
attached to the patient's glasses, or to plano glasses if the
patient has no refractive error, and serve to compensate
for the inward misalignment of the affected eye.
Use of Botulinum toxin
◦ helps to prevent the contracture of the medial rectus which might
result from its acting unopposed for a long period.
◦ reduces the size of the deviation temporarily it might allow
prismatic correction to be used where this was not previously
◦ removes the pull of the medial rectus it may serve to reveal
whether the palsy is partial or complete by allowing any residual
movement capability of the lateral rectus to operate
Vertical muscle transposition procedures such as
Jensen's, Hummelheim's or whole muscle transposition
Eye Movements ,
Pupil: Size, Symmetry, Reactions.
IV and VI NERVE:
Sensation to face