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Chapter
t3
Cranral Nerve Palsy Update
Christopher S. Wolfe, O.D., F.A.A.O.
Updated 2016 by: Philip Roels, O.D., F.A.A,O
177
CHAPTER 13. CRANIAL NERVE PALSY UPDATE
178
13,1
Oculomotor Nerve Palsy
o The oculomotor nucleus in the midbrain consists of subnuclei responsible
for inner',?tion of the individual extraocular muscles, the levator palpebrae, and the iris sphincter muscle. The third nerve leaves the midbrair
and enters the subarachnoid space before entering the cavernous sinus
It then splits into superior and inferior branches when entering the orbit
l,hrough l,he superior orbihal fissurc.
-
The superior division of the oculomotor nerve supplies the ipsilateral
levator and the contralateral superior rectus.
-
The inferior division of the oculomotor nerve innervates the ipsilateral medial rectus, inferior rectus, inferior oblique, and the iris
sphincter muscle.
.
Common causes of an oculomoto! nerve pa,lsy iDclude an aneurysm
to the posterior communicating artery, tumor, trauma, pituitary
apoplexy, orbital inflammation or masses, herpes zoster, Ieukemia, and
uncal herniation.
. It
occurs most often in patients over age 50 with microvascular
factors.
risk
Symptoms:
Depending on the severity of the upper eyelid ptosis, the patierrt
may or m8y not notice diplopia due to the upper eyelid blocking the
visual axis of the affected cye. Patients may also conrplail of nrild or
moderate pain in ischemjc lesions, or severe pain in cases of a ruptured
ancrrrysm, innammatory lcsions, or pitujLary apoplexv (6).
Signs: A complete palsy will have an ipsilateral ptosis with an eye tllat rs
down and out. Incomplete palsy is anything less thaD a complete palsy.
Exatnples include the following:
.
A riAht inferior oblique palsy will present with a right hypotropia
in primary gaze and vertical diplopia that is y/orse on gaze up and to
the left and worse with head tilt to the teft
13
1,
OCULOMOTOR NERVE PALSY
179
Inferior oblique muscle entrapment ard Brown's syndrome may present
with Endings sirnilar to a right inferior oblique palsy, Forced duction
testing may be used to diEerentiate between these conditions. An inferior oblique palsy is chara.te zed by a negative forced duction test
(the eye will mo\re when forced), while Bro{,'n's s}.ndrome and an inferior oblique muscle entrapment are characterized by a positive forced
duction t€st (the eye will not move when forced).
o Right medial rectus palsy will present with horizontal diplopia that
is worse on
left gaze, and a negative forced duction test.
. RiBht supetior rectus
palsy will present with right hypotropia in
prima.ry gaze that is worse on gaze right and head tilt to the right, as
well as a negative forced ductio[ test.
.
Superior division palsy
is chara.terized by significant ptosis and limited ability to look up, a.s this division of CN 3 contrcls both the superior
rectus and the le\Btor palpebra€ muscle.
o Inferior division palsy will present with poor a.dduction
a.nd limited
ability to look down, a.s this division of CN 3 inrlenBte6 the medial rectus,
inferior rectus, and the inferior oblique-
I\eatment will depend on the extent of EOM and pupil involvement
. If the palsy is incomplete or if the pupil is involved (dilated),
an imme.
diate MRI/MRA is indicated.
.
If the palsy is complete, the pupil is NOT involved, the patient is over
the age of 40 with known \,rscula.r disease (e.g., diabetes rnellitus, hypertension, smoking), there are no other neurological abnormalities, and
there ale no new s],.mptorna on subsequent exams, the palsy is considered
ischemic in nature. Tlestment includes:
-
Flesnel prism or petching os symptoms dictate
Check blood plessure, blood sugar, and hemoglobin A1c
-
Abefiant regeneration never occurs in ischemic CN 3 palsies.
Monitor for resolution; if there is no resolution by 3 months, an
MRI/MRA is indicated.
.
Third nerve palsies that are NOT isolated, and/or are accoopa.ried by
othe! neurologic sitns or symptoms require prompt neuroimaging with
MRI/MRA.
.
Patients older tha.n 55 years of age should be evaluated for symptorrrc
ard signs of giant cell arteritis, including ordering a CBC, er).throclte
sedimentation rate (ESR), and C reactive protein (CRP).
o An orbital CT scan
is indicsted if orbital dis€a.se is suspected as the cause
of a third nerve palsy due to proptoois and/or resistance of the globe to
retropulsion.
CHAPTER 13, CRANIAL NERVE PALSY UPDATE
180
13.2 Tlochlear Nerve
.
Palsy
CN 4leaves the midbrain dorsally and then decussates to the contralateral side of the brainstem; thus, the right superior oblique is innervated
by the right CN 4, with its nucleus on the left side of the brainstern.
Because CN 4 has the lontest course, it is most susceptible to trauma.
Symptoms: vertical diplopia without
ptosis
Signs: head tilt and turn away from the involved
eye, and
limited depression
on adduction
1. Congenital CN 4 palsy:
.
Long history of head
tilt
(refer to old pictures)
o F\ller face on the opposite side of the head
paretic muscle)
tilt
(sarne side &s the
.
No torsional diplopia complaints, and may not see a torsional conrponent with Ma.ddox rod
.
Large yertical vergence ranges:
sional amplitude
> 3 prism diopters of vertical
fu-
2. Acquired CN 4 palsy (trauma, vascular, iatrogenic (e.g., sinus surgery,
orbital surgery), or tumor):
o No facial asymmetry
.
.
Acute ons€t
Torcional diplopia - perform a double Maddox rod test if a bilateral
CN 4 palsy is suspected
3. Park's Thrcc Stcp can be uscful lor confirnring a CN 4 palsy, :s only a
single muscle is responsible for a yertical deviation. The test involves
the following questions (2):
a) Which
.
eye is highest in the primary position of gaze?
The afiected muscle could be the inferior-acting muscles (inferior rectus or superior oblique) in the hyper eye OR the
superior-acting muscles (superior rectus or inlerior oblique) in
the h)?o eye.
b) Is the hyper worse when the patient looks in left or irr right gaze?
c) Is the hyper worse when the patient tilts his head to the left or to
the right?
]3.3. ABDUCENS NERVE PALSY
181
try to rninimize the eflects of a superior oblique palsy by
tilting their head away from the afrected side. One of the actions
Patients will
of the superior oblique is incyclotorsion; by tilting their head away fronr
the aflected side, patients minimize incyclotorsion of the affected eye,
resulting in a decrease in diplopia.
o Che& blood pressure, blood sugar (BS), and hemo8lobin AIC if miclovascular disease is suspected.
.
An orbital CT is indicated if orbital disease is suspected due to proptosis
snd/or resistence to retropulsion.
.
Order er,'throc)'te sedimentation rate (ESR), C reactive protein (CRP),
and platelets if GCA is suspected.
. If the patient has large vertical
fi$ional vergence ranges, or old pictures
show a head turn, consider prescribing vertical prism based on the asso
ciated phoria findings.
o If the CN 4 palsy is progressive, other neurological findings are present,
the patient is younger than 40 without a history of head trauma, or the
patient is 4G55 years of age with no microlascular risk factors, consider
neurcimaging.
13,3
.
Abducens Nerve Palsy
CN 6 fibers leave the nucleus in the pons by Lraversing between the
pons and the medulla before making a tight bend over the petrous
ridge of the temporal bon6 to enter the cavernous sinus (3). Within
the cavernous sinus, CN 6 trsvels near the lateral wall of the internal
carotid artery. Lesions along the course of CN 6 can lead to tnpaired
function.
.
Common causes of CN 6 palsy include:
-
Microvascular: patients with undiagnosed or uncontrolled DM or
HTN
Ttmors or pseudotumor cerebri
* An increase in intracranial pressure will ptrch CN 6 down onto
the petrous portion of the temporal bone, resulting in decreosed
innervation of the lateral rectus (12).
,r A tumor involving the ca\.€rnous sinus or brainstem rnay present
with Ilorncr's syndrome in addition to an abduction dcficit
CHAPTER 13. CR,4NIAL NERVE PALSY UPDATE
182
- tatrma
- lnternal carotid
adery sreurysm
Symptoms: horizontal diplopia
Signs: limited ABduction
.
If patients
.
.
Orde! an ESR, CRP, and platelets if GCA is suspected.
present with symptoms or signs of increased intracranial pressure (e,g., postural headache, papilledema, neurological symptonls), or
llvith multiple cranial nerve involvement, irrrnediate neulo-imaging with
an MRI/MRA is vrarranted.
Order an RPR, FTA-ABS, and Lyme titer if syphilis or Lyme disease is
suspected.
. If
patients have a history of micro!"scular disease, communicate with
their PCP to ensure adequate control of blood sugar, blood pressure, or
any other relerant measures. If DM and HTN are controlled, and the
CN VI palsy does not resolve within 3 months, consider neuro-ilnaging.
.
Consider Fresnel prism or occlusion for temporary relief of diplopia Once
the ocular deviation has stabilized, consider ground-in prism in spectacle
Ienses.
13.4
Facial Nerve Palsy(CN
VII)
o The faciol nerve is lesponsible for voluntary motor inneE€tion to the
muscles of facial expression and eyelid closure, as well as involuntary
motor innervation to the inner ear (stapedius muscle), and parasympathetic supply to the facial glands (including the lacrimal gland) The
facial nerve also co.rries taste sensations from the anterior 2/3 of the
tongue.
.
CN 7 travels near CN 6 and CN 8. If a patient presents with a palsy
of one of those crarial nerves, check the aations of the other 2 cratial
nerves to determine whether all three axe involved
.
The following is a description of the neurological path of CN 7:
-
Movements are initiated in the precentral motor cortex irr the
lob€ ( l1).
frontal
Fibers descend within the corticobulbar tract to the nuclei of CN 7
in the pons
(
11).
13.4. FACIAL NERVE PALSY(CN VII)
-
-
183
Fibers leave the nucleus by arching arouDd the abducens nucleus; any nuclear lesion of CN 6 could also afrect CN 7.
Fibers then travel with CN 8 through the temporal bone (12).
Within the temporal bone, the greater petrosal nerve breaks
away,
carrying parasympathetic innenation to the lacrimal gland. As the
fibers leave the temporal bone, CN 7 departs from CN 8 and enters
the fallopian ca.nal.
Withir tle canal, CN 7 Sives ofl a motor trranch to the stapedius
rnuscle (to dampen sound) and the chorda tyrnpari nerue (carries
taste from the anterior two-thirds of the tongue and parasympathetic 6bers to the submandibular and sublingual glands).
CN 7 leaves the fallopian canal and exits the skull via the stylom&stoid foramen, then divides irrto terrninal branches within the parotid
gland. These branches inner%te the muscles of facial expression;
they do not inneF'ate the parotid gland (receives innen?tion lrom
cN
e).
Symptoms: Iack of lower and/or upper facial expression, reduction in taste,
and decreased Iacrimation and sali%tion
Signs: exposure keratitis, incomplete lid closure, facial asyrnmetry
.
A supranuclear lesion results in impaired inneruation to the Iower
facc on the contralateral sidc. The contralatcral fibers that arc rG
sponsible for eyelid closure and wrinkling of the forehead a.re spared;
therefore, stroke patients should be able to wrinkle their forehead
and lirrnly close their eyes. Damage on one side of the l:rain contributes to contralateral muscle weakness of the lower face, which
can manifest as mouth drooping.
. A lower motor neuron lesion (i.e., Bell's
palsy) results in impaired iunervation to the entire side of the face on the ipsilateral
side. Paticnts will not bc ablc to lirmly closc thcir eye and Lhcir
mouths will droop on the affected side. A lower motor neuron lesion can result in paralltic lagophthalmos, the most common form
of lagophthalmos ( 1).
Bell's Palsy will completely
resolve without treatment in 70-80% of cases (8).
o If Bell's palsy is present without sny other craoial nerve defects or other
neurological symptoms, and without a history of facial spasm, teuroimaging is not necessary (8).
.
If the patient presents within
(l
10 days of onset, consider oral prednisone
mg/kg of body weight, dosed in the morning) for 7-10 days, with a
short taper after 10 days (4).
.
Consider sdding an oral antiviral (800 mg acyclovir 5X/day, 500 rrrg
famciclovir TID, or 1,000 mg relacyclovir TID) for 7-10 days if a herpetic
infection is suspected (4).
CHAP'TER 13, CRANIAL NERVE PALSY UPDATE
184
.
Bell'B palsy may be the initial s],mptom of a more serious underlying
disease. Therefore, if the palsy wonens or do€s not improve within 6
weeks, neuro-imaging is indicated (11).
1. How often is an isolat€d cranial nerve palsy due to an etiology
other than microvascular disease?
.
.
A prospectile observation case series of 109 patients older than age
50 was performed to estimate the proportion of patients with isG
lated third, fourth, or sixth cranial nerve palsies of presumed microaascular origin veNus other caused (15):
- 62 patients had cranial nerve 6 palsy
- 25 patients had cranial nerve 4 palsy
- 22 patients had cra al nerve 3 palsy
18 patients had a cronial nerve palsy caused by an etiolo6/ other
than presumed microvascular ischemia (e.g., midbrain infarction,
neopla.srns, iDflarnmation, pituitary apoplexv, and giant cell arteritis).
2.
15 of these 18 patients had either GCA or a cranial nerve 3
palsy.
The incidence of non-miclov'ascular causes for isolated fourth
and sixth cranial nerve palsies \rvas 4.770 (3164).
Wlat is the most common cause of a CN 4 patsy?
. In a study of 190 patients with a superior oblique palsy,
72% of
p8lsieg were congenital, arld 28ya werc acquired. Of the acquired
CN 4 palsies, 54% were due to trauma (per history), 23%
were
iatrogenic, 13% were vascular, and 10% were caused by a tumor.
Of the 1S0 patients with a supe or oblique palsy, only 2.8% of
cases were due
to a tumor (16).
3. 'What are the rnost common risk factors associated with microvasculaf cranial nerve palsies?
.
A study of 54 patients wa6 pelformed to investigate the risk factors
ond prognoEis for ischemic cra.nial nerve 3, 4, and 7 palsies (9):
- Out of microaescul$ sk factors including diabetes mellitus
(DM), hypertension (HTN), hlperlipidemia, ischemic heart disease, left ventricular hlpertrophy (LVH), aad smoking, DM,
HTN and hyperlipidemia were much more likely to be the
u[derlying cause of the cranial nerve palsy compared to the
other risk factors.
- The average recovely time for patients with 2 or more risk factors was 9.0 +/- 5.1 week.
- The average lecol€ry time for patients with 1 risk factor wa.9
6.1 t/- 2.2 weks.
4. Does aspirln play a role in preventing cranial nerve palsies?
. A study of 100 patients that eraluated whether aspirir helped to
prevent ischemic CN palsies associated with DM a.nd/or HTN
found no siSnificant difference in the incidence of CN palsies in patients who took aspirin compared to those who did not (7)
13.4. FACIAL NERVE PALSY(CN Vrr)
185
5. Do oral steroids or oral antivirals improve resolution of Bell's
palsy?
. A study of 551 patients older than
16 yearc of age with unilateral, idiopathic facial nerve weakness (Bell's pa-lsy) seer within 72
hours after the onset of symptoms evaluated whether early treatment with oral prednisone (25 mg BID) or oral a.yclovir (400 mg
5X/day) improves the chance of recovery in Bell's palsy compared
to a placebo (14). Patients were randomized into I of 4 treatment
groups and were followed for I months:
a) Acyclovir (400 mg 5X/day for 10 days) + placebo
b) Acyclovir (400 mg SX/day for 10 days) + prednisone (25 mg
BID for
10 days)
Prednisone (25 mg BID for 10 days)
Placebo + Placebo
3 month study results:
c)
d)
.
-
. I
+
placebo
83% of patients who received oral predlisone demonstrated
complete recovery compared to 63.6% ofpatients who do not receive oral prednisone (Absolute risk reduction (ARR) : l9-4%,
Number needed to treat (NNT) : 6).
71.2% of patients taking acyclovir demonstrated complete recovery compared to 75.7% of patients who did not receive acy-
clovir (not a statistically sigrifrcart difierence).
64.7% of patients who received double plaaebo demonstrated
complete recovery.
month study results:
- 94.4% of patierlts who received ora,l prednisone demoostrated
complete recovery compared to 81.6% of patients who did not
-
receive prednisone (ARR : 12.8%, NNT = 8).
85.4% ol patients who received acyclovir demonstrated complete recovery compared to 90.8% of patients who did not receive a.yclovir (nob a statistically significant difierence).
a5.2% of patients who received double placebo demonstrated
complete recovery.
6. Does the addition of valacyclovir to oral prednisone aid in the
resolution of Bell's palsy?
o A study of
296 patients older than 15 years of age with unilateral,
idiopathic facial nerve weaftness (Bell's palsv) seen within 7 davs
after the oruet of symptoms evaluated whethei treatment with oral
prednisole and oral va.lacyclovir improved resolution conpared to
oral prednisone alone (5). Patients were randomized into I of 2
.
treatment groups and were followed untjl recovery or 6 months:
a) Valacyclovir (500 mg BID for 5 days) * prednisone (60 mgld
for 5 days, 30 mg/d for 3 days, 10 mg/d for 2 days) (VP)
b) Placebo + prednisone (60 mg/d lor 5 days, 30 mg/d for 3 days,
10 mg/d for 2 day$ (PP)
Complete recovery occurred in 96.5% of patients in the VP group
compared to 89.7% of patients in the PP group (ARR = 6.8%, NNT
:
.
15).
Patients treated with Iacyclovir within 3 days after the onset of
symptoms were siSnificantly more likeLy to recover.
CHAPTER 13, CRANIAL NER]/E PALSY UPDATE
r86
.
For patients treated 4 days or more afler the onset of symptoms,
there was no significant diflerence in recovery between treatmenL
SrouPs.
KMK Clinicat
.
Pearls
In patients with an isolated CN 3 palsy, have a heightened suspicion
of other underlying diseases, even in the presence of microvascular
disease. Consider ordcting an MRI/MRA, CBC with differential, DSR,
and CRP, even when the pupil is not involved, in a patient with a complete CN 3 palsy.
o A microrarular CN palsy is expected to completely resolve by 3 rnonths;
neuro-imaging should be performed (or repeated) at 3 months if resolution has not occurred. Also recall that the greatpr the rumber of
microvascular risk fa.tors, the longer it may take a CN palsy to resolve;
it is unlikely for patients with I micro\,ascular risk factor to have a CN
palsy that does rot resolve withil 2 months, so it may be prudent
to consider neurGimaging in patients with presumed ischemic
CN palsies at 2 months if resolution has not occurred by that
tiIne.
o Aspirin appears to be ineffective at preventing ischemic third,
fourth, sixth, and seventh cranial nerve palsies. There are no
clinical trials that have investigated whether aspirin prescribed at the
initial onset of a CN palsy results in faster resolutiorr.
.
Acute, unilateral facial paralysis can occur from damage to the facial
nerve secondary to infcctiolr, inflafiunation, compression, or trauma. T]rc
diagnosis of Bell's palsy is reserved for those cases in which the precipitating event cannot be identified (i.e, idiopathic CN 7 palsy)
.
Patients presenting with a new onset Bell's palsy within 72 hours should
be educated that there is an approximately 65% chance of complete recovery in 3 months, and an 85% chance of complete recovery in I months
without treatment.
.
The use of oral prednisone in previous studies has been shown to
increase the likelihood of complete recovery to 83% by 3 months and
94% by 9 months.
.
Oral prednisone should be used with caution in patients with poorly
controlled diabetes mellitus or hypertension, or a comprornised imnrune
system. Oral prednimne shor.rld also be avoided in patients who are
pregnant o! breast-feeding.
.
For those patients with s complete Bell's palsy, the addition of vala-
cyclovir (50O mg BID for 5 days) can signiffcantly improve the
likelihood of a complete recovery by 6 months. This statistical difference was not seen if the patient was siarted onT.alacyclovir 4 days or
more after the onset of symptoms.
.
Treating BelJ's palsy with oral acyclovir docs not significanhly improvc
the likelihood of recovery,
.
Consider testing for herpes zoster (VZV), as it is the cause of facial
paJal)sis similax to Bell's palsy in up to 870 of patients with presumed
Bell's palsy (5).
13.4. FACIAL NER\E PALSY(CN VIt)
.
VZV faaial paralysis is often more
r87
severe and has a wolse recovery rate
compaxd to Bell's palsy. Due to the Iow incidence of VZV facial paralysis, the low complication rate associa,ted with treatment, and the need
to quickly start treatment, patients should be treated empirically as a
Bell's palsy without waiting for the results of serologic testing for VZV.
.
Additional testing and neuro-irnaging should be considered in patients
whose Bell's palsy has a slow onset (longer than 10 days), occurs bilaterally, or is associated with other syrptonrs (13).
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