7.1 Cranial Nerve III (Oculomotor) Palsy
7.2 Cranial Nerve IV (Trochlear) Palsy
7.3 Cranial Nerve VI (Abducens) Palsy
7.4 Cranial Nerve VII (Facial) Palsy
7.5 Optic Nerve Function
7.6 Visual Fields to Confrontation
7.8 Horner’s Syndrome
7.10 Neuro-Ophthalmic Differential Diagnoses and Aetiologies
Cranial nerve IV palsies are extremely common in examinations. Although it is the most common cause of a vertical strabismus, the examiner should remember other causes (e.g. TED, orbital fractures) and not rush into Parks 3 step test unless the clinical picture is suggestive of CNIV palsy. Care should be taken to identifying bilateral CNIV palsies and signs indicating a congenital (versus traumatic) aetiology.
Congenital: abnormal head position
Congenital: vague, intermittent vertical diplopia
History of trauma, torsional diplopia
Often complain of difficulty reading (not diplopia)
(RRR: Right hypertropia worse on Right head turn and Right head tilt; LLL).
Figure 7.2.3 Parks-Bielschowsky Three-Step Test
1. Right hypertropia can be due to weakness of the right depressors or left elevators
2. Right hypertropia that increases on right head turn isolates the pathology to the right superior oblique or left superior rectus
3. Right hypertropia that increases on right head turn and right head tilt isolates the pathology to the right superior oblique
Look for a “falling eye”:
Traumatic CNIV are often bilateral
10° of excyclotorsion on Double Maddox rod (NB: Skew deviation gives incyclotorsion)
SO Underaction (SO UA)
Ipsilateral SO UA
Bilateral SO UA
IO Overaction (IO OA)
Ipsilateral IO OA
Bilateral IO OA
<10 PD (eso)
>10 PD (eso)
<5 PD (except asymmetric paresis)
Head Tilt Test
Increasing hypertropia on ipsilateral head tilt
Positive head tilt test to both sides (right hypertropia on right tilt and left hypertropia on left tilt)
Reversing hypertropia on R and L gaze
Objective Torsion on Fundus
Extorsion on Double Maddox Rod
<10 degrees (congenital usually do not have subjective extorsion)
>10 degrees (congenital usually do not have subjective extorsion)
Figure 7.2.5 Double Maddox Rod Test
Maddox rods are placed vertically in front of each eye. In a CNIV palsy the (horizontal) line image of one will not be parallel to the other because of excyclotorsion of the eye. The amount of excyclotorsion can be measured by rotating the lens until the images of the two lines are parallel. In a bilateral CNIV palsy the amount of excyclotorsion is typically >10°.
Usually unilateral with decompensation.
Usually an abnormal tendon:
3Δ vertical fusional amplitude (however, fusional amplitudes are also increased in long-standing acquired deviations e.g. TED)
NB: Remember that a Hess chart does not measure torsion.
Indications for Treatment:
Wait at least 6 months and until measurements are stable.
In addition to the above consider the Harada-Ito procedure (move the SO insertion anterior and temporal).
NB: It is debatable whether torsion is a barrier to fusion and should be treated.
NB: Avoid over-correcting CNIV palsies.
The Harada-Ito Procedure
The superior oblique is split and the anterior portion moved anteriorly and temporally to just posterior to the insertion of the lateral rectus. This improves excyclotorsion.
Superior Oblique Tendon Tuck
For marked superior oblique underaction.
The trochlear nerve is the only cranial nerve to exit the brainstem from the dorsal side and the only one to originate entirely from a contralateral nucleus. It is the most slender, longest cranial nerve and therefore is prone to traumatic injury
Nuclear lesions are rare but can give a contralateral CNIV palsy + ipsilateral Horner’s.
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