Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5507_Библиотеки_им_академика_М_И_Перельмана.pdf
326 Theory and Practice of Squint and Orthoptics
passes through pyramidal tracts and is
characterized by:
• Ipsilateral 6th nerve palsy,
• Contralateral hemiplegia, and
• Variable number of signs of dorsal pontine
lesions.
iii. Millard-Gubler syndrome. It results due to
lesions similar to Raymond's syndrome and is
characterised by the same features with addition
of ipsilateral 7th nerve palsy.
3. Lesions involving the 6th cranial nerve trunk
anywhere are as follows:
a. Infections and immunological processes may
involve the sixth cranial nerve trunk. A benign
and occasionally recurrent form of 6th nerve
palsy occurs in children, usually following
upper respiratory infections, other forms of mild
viral illness, including immunization. The
spontaneous benign lesions usually resolve
over several months.
b. Vascular disorders such as hypertension and
diabetic microangiopathy can also cause 6th
nerve palsy specially in elderly due to
ischaemic infarction.
c. Multiple sclerosis is an important cause of
6th nerve palsy in patients below 40 years of
age.
d. Idiopathic sixth cranial nerve palsy has been
labelled as a major group in most of the series
of isolated sixth nerve palsy. Some of such
cases might be due to undiagnosed vascular
ischaemic infarcts.
• Deafness
• Neuralgias in the distribution of first division
of trigeminal nerve.
• Facial weakness.
v. Involvement in raised intracranial pressure. Sixth
nerve paralysis is one of the commonest false
localizing sign in cases with raised intracranial
pressure. Its susceptibility to such damage is due
to its long course in the cisterna pontis, to its
sharp bend over the superior border of the
petrous temporal bone and the downward shift
of the brainstem (towards the foramen
magnum) produced by raised intracranial
pressure (Fig.12.22).
5. Lesions of the intracavernous part of 6th
nerve. Since the sixth nerve runs through the
middle of the cavernous sinus, it is more prone
to damage than the other nerves from the
intracavernous lesions such as aneurysms,
meningioma, carotid cavernous fistulae and
Tolosa-Hunt syndrome (granulomatous inflammation). In contrast to third nerve, aneurysms
rarely cause a sixth nerve palsy. Vascular causes
such as diabetes and hypertension are, however,
common causes of sixth nerve palsy.
Since in its intracavernous part, the sixth nerve
is joined by the sympathetic branch from
paracarotid plexus; so occasionally sixth nerve
palsy may be accompanied by Horner's
syndrome.
4. Lesions of the basilar part of sixth nerve. The
important causes which may damage the basilar
part of the sixth nerve include:
i. Acoustic neuroma. It should be emphasized that
the first symptom of acoustic neuroma is hearing
loss and the first sign is diminished corneal
sensations. Therefore, hearing and corneal
sensations should be tested in all patients with
sixth nerve palsy.
ii. Nasopharyngeal tumours
iii. Fracture base of the skull, and
iv. The involvement of petrous bone from otitis
media may cause Gradenigo syndrome,
characterized by the following:
• Ipsilateral 6th nerve palsy
Fig. 12.22 Mechanism of sixth nerve palsy resulting from
raised intracranial pressure.
Incomitant Strabismus
327
6. Lesions of the intraorbital part of sixth nerve.
Isolated sixth nerve palsy due to intraorbital
lesions is not so common. However, it is
involved in the lesions producing orbital apex
syndrome and superior orbital fissure syndrome.
Causes of acquired 6th nerve palsy in
descending order of frequency are:
• Tumours (45%)
• Raised intracranial pressure (such as from
idiopathic intracranial hypertension or
hydrocephalus)
• Trauma
• Inflammations
• Vascular disorders, e.g. hypertensive and
diabetic microangiopathy causing diabetic
mononeuropathy
• Idiopathic, i.e. cause not known
Clinical features
Clinical features in an isolated 6th nerve palsy
are as follows:
1. Incomitant esotropia. Initialy esotropia occurs
in the involved eye (Fig. 12.23A) due to
unopposed action of the medial rectus muscle
and is proportional to the loss of LR function.
The esotropia increases in gaze towards the
paretic lateral rectus muscle (Fig. 12.23B) and
patient becomes orthotropic in the opposite gaze
(Fig. 12.23C). When tested with cover test,
secondary deviation in the uninvolved eye is
larger than the primary deviation.
Later on due to secondary MR contracture, the
weaken abduction function is further limited and
esotropia occurs in contralateral gaze too. Ocular
deviation should be measured with face turn with
forced primary position and in lateral gaze. Vpattern may result from lessened abduction and
unopposed action of MR in downgaze. There
may be presence of vertical deviation less than
3 PD due to removal of inhibitory effect of LR on
vertical movements. If hyperdeviation is larger
than 5 PD, rule out 4th nerve palsy too.
2. Abnormal head posture is frequently associated
with incomitant esotropia. Face is turned towards
the action of the paralysed lateral rectus.
3. Diplopia may not be a problem in visually
immature children. However, visually mature
old patients have an uncrossed horizontal
diplopia with maximal image separation at
distance and to the side of involvement
(Fig. 12.24).
Fig. 12.23 A patient with left lateral rectus palsy having left
esotropia in primary gaze (A) which increases in left lateral
gaze (B) and becomes orthotropic in right gaze (C).
Fig. 12.24 Diplopia chart of a patient with right lateral
rectus palsy.
328 Theory and Practice of Squint and Orthoptics
Initially with near fixation, equilibrium in
convergence can occur without diplopia but
later on with greater and older deviations and
with secondary contractures permanent diplopia
occurs for distance and near.
4. Ocular movements in a patient with lateral
rectus muscle paralysis (e.g. of right eye) are
affected as below:
• Abduction in right eye is limited due to
paralysis of lateral rectus muscle.
• Overaction of right eye on levoversion.
• Overaction of left eye on dextroversion.
• Underaction of left eye on levoversion.
Differential diagnosis
Sixth cranial nerve palsy should be differentiated
from:
i. Duane's retraction syndrome (see page 351).
ii. Congenital esotropia with crossed fixation—
pseudoabducens paralysis (see page 243), and
iii. Nystagmus blockage syndrome.
Management
I. Clinicoinvestigative work-up and treatment of
the cause
The diagnosis of 6th cranial nerve palsy as such
does not pose any problem. However, aetiological diagnosis especially in cases of isolated
lateral rectus muscle palsy may not be possible
in many a cases.
• Careful history should be taken to define
antecedent infections, head trauma, or other
possible inciting factors for sixth nerve paresis.
• In children less than 16 years with no neurological
signs and symptoms, no work up is required.
Close follow-up every 2 weeks initially and
then monthly is required. Persistent palsy
after 3 months requires evaluation.
• In young adults, 16 to 40 years, risk factors
should be ruled out.
• In older patients more than 40 years, look for
vascular causes such as hypertension, diabetes,
atherosclerosis.
• If more than 55 years, giant cell arteritis should
be ruled out.
• Haematological investigations like fasting blood
glucose, complete blood count, ESR, ANA
titres, RPR test, FTA-ABS, TFT should be
carried out.
• Lumbar puncture is required in cases of raised
intracranial tension.
• Orbital ultrasound should be performed to rule
out enlarged extraocular muscles.
• Binocular diplopia free fields to be evaluated
by Goldmann perimeter using III 4e target
size.
• Neurological evaluation with computerized
tomography or magnetic resonance imaging is
indicated:
– When neurological signs or symptoms are
present.
– In the presence of multiple cranial nerve
palsies, and
– In younger patients without muscular causes.
Note. After an exhaustive investigative workup, if some cause is found and when treatable,
appropriate measures should be taken; which
by and large are the domain of neurophysicians
and/or neurosurgeons.
II. Conservative measures
A wait and watch for a minimum period of 6–8
months is must, when self-improvement is
expected, especially in idiopathic cases and cases
with benign palsies. Following conservative
measures may be useful during this period:
1. Measures to expedite recovery from palsy
i. Vitamin B-complex may be used as a neurotonic.
ii. Systemic steroids may hasten the recovery in
patients with non-specific inflammations.
2. Measures to prevent amblyopia and relieve
diplopia. The main aim of conservative
measures while waiting for spontaneous
recovery is to provide relief from diplopia and
additionally in children to prevent amblyopia
and preserve binocular vision. Following
measures may be useful:
i. Patching or occlusion is advised as below:
• In cases with mild esodeviation and residual
LR function intact, occlusion of the unaffected
eye is advised to stimulate fixation of affected
eye in abduction and relaxation of ipsilateral
MR, to prevent contracture of medial rectus.
• In cases with severe palsy alternate occlusion
is preferred as it alternates fixation, relieves
diplopia prevents medial rectus contracture,
and prevents amblyopia.
Incomitant Strabismus
329
ii. Fresnel press-on prisms are useful to correct the
diplopia in primary position.
iii. Botulinum toxin injection into the antagonist
medial rectus causes its paralysis and is thus
useful for a temporary alignment of the eyes in
the primary position. Such injections are also
useful in preventing the contracture of the
medial rectus muscle, while the patient is
observed for several months prior to surgical
intervention. The effect lasts for 2–3 months.
May be repeated if necessary.
3. Observation and monitoring. Spontaneous
resolution of the sixth nerve paresis, sometimes
occurs, making the surgery unnecessary.
• Hess screen charting (Fig. 12.25) is useful for a
meticulous follow-up and monitoring of the
patients during this waiting period.
III. Surgical treatment
Surgery is indicated, when spontaneous
resolution does not take place after 6 months or
more of follow-up and after exclusion of the
intracranial lesions.
Aim of surgical treatment is to correct the
incomitant esotropia, improve abduction,
provide a useful field of binocular single vision
and to eliminate the abnormal head posture.
Recommended surgical measures are as below:
I. Recess-resect operation. A supramaximal
(12–16 mm) recession of the antagonist medial
rectus with about 8–10 mm resection of the
lateral rectus muscle is often a successful first
operation in most patients with incomplete
paralysis. This procedure often provides a useful
field of binocular single vision and eliminates
the abnormal head posture.
• In case a mild paresis is still present, weakening
of the contralateral medial rectus muscle with or
without Faden procedure may be considered
as a second operation.
• Adjustable suture surgery may be helpful for
final adjustments in co-operative patients with
paralytic squint.
II. Muscle transposition procedures recommended
for a complete paralysis of lateral rectus muscles.
Medial rectus recession should also be combined
especially, when there is medial rectus
contracture. Forced duction test is useful in
discovering MR contracture.
1. Jensen's procedure combined with the medial
rectus recession is useful by balancing the
partially active forces. In the Jensen's
procedure, the superior rectus, inferior rectus
muscles and the paralysed lateral rectus muscle
are split for 8–10 mm from their insertion
backwards with the help of a muscle hook.
Then the superior half of the lateral rectus is
united with the lateral half of the superior
rectus and the inferior half of the lateral rectus
Fig. 12.25 Hess chart of a patient with paralysis of right lateral rectus muscle.
330 Theory and Practice of Squint and Orthoptics
with the lateral half of inferior rectus with the
help of a non-absorbable suture (e.g. 5–0
Mersilene). The knot should be tied near the
equator (Fig. 15.22).
2. Hummelsheim operation. In this procedure,
after splitting the superior and inferior recti,
their lateral halves are disinserted and sutured
to the tendon of lateral rectus muscle. This
operation is rarely done nowadays and is thus
mainly of historical interest.
3. Berens and Girard procedure. In this
procedure, the full inferior and superior rectus
tendons are disinserted and sutured with the
tendon of lateral rectus at its insertion. This
procedure combined with a recession of the
medial rectus is recommended by von Noorden
in children with complete paralysis of sixth
cranial nerve.
4. Carlson and Jampolsky transposition
procedure. In this procedure, medial rectus
muscle is spared. After splitting the vertical
recti, their temporal halves are inserted under
the lateral rectus. It is essential to separate the
halves of the vertical recti to the deepest point
toward the apex of the orbit, allowing the
transposed parts of the vertical recti to slide
toward the LR, which also minimises vertical
deviations. This procedure reduces the angle
of deviation below 10PD, improves abduction,
prevents relapses, and also prevents anterior
segment ischemia.
5. Superior rectus transposition with MR
recession have also shown good results in
literature. This procedure is successfully tried in
lateral rectus palsy and also in abduction deficit
conditions like Duane’s syndrome and Mobius
syndrome, especially if hypertropia is also
associated. It may induce vertical deviation also.
III. Contralateral medial rectus muscle
recession with or without Faden operation can
be considered an option for the residual lateral
rectus abduction deficit and/or residual
esotropia, often the above surgical measure.
Summary of surgical guidelines
Based on the above discussion surgical
treatment guidelines are summarized in
Table 12.9.
MEDIAL RECTUS PARALYSIS
Isolated medial rectus paralysis is extremely
rare, yet do occur, often without any satisfactory
explanation.
Etiology
Exact etiology of this rare entity is not known.
However, trauma and vascular disorders may
be implicated in occasional cases.
Table 12.9 Summary of surgical guidelines for treatment of sixth nerve palsy
Clinical presentation Surgery
Excellent lateral rectus function (90–100%) Recess contralateral medial rectus 5–6 mm (adjustable
Ductions = trace limitation suture optional)
ET in primary position = 2 to 8 PD
Diplopia to the side of the palsy
Good lateral rectus function (80–90%) Bilateral medial rectus recessions, but recess the
Ductions = –1 contralateral medial rectus muscle 6 mm and the
ET in primary position = 10 to 20 PD ipsilateral medial rectus muscle 3–5 mm (adjustable
suture advised)
Fair lateral rectus function (60–80%) Ipsilateral medial rectus recession 6 mm (adjustable
Ductions = –2 suture advised), lateral rectus resection or Wright
plication 5 mm and contralateral medial rectus
recession
ET in primary position = 20 to 30 PD 3–5 mm (with optional Faden)
Poor lateral rectus function (<60%) Ipsilateral medial rectus recession 6–7 mm (adjustable
Ductions = –3 to –4 suture in adults or cooperative children), and vertical
ET in primary position = 30 + PD rectus partial-Tendon transposition to the lateral
rectus muscle (either Jensen or Hummelsheim), author
prefers modified Hummelsheim
Fig. 12.26 A patient with right medial rectus paralysis
having right exotropia in primary gaze (A) which increases
in left gaze (B) and the patient becomes orthotropic in right
gaze (C).
Incomitant Strabismus
Fig. 12.27 Diplopia chart of a patient with right medial
rectus palsy.
331
5. Hess screen charting is as shown in
Fig. 12.28.
Clinical features
1. Incomitant exotropia occurs in the primary
position in the involved eye (Fig. 12.26A) due
to unopposed action of the lateral rectus. The
exotropia increases in gaze towards the
paralysed medial rectus (Fig. 12.26B). The
patient becomes orthotropic in the opposite gaze
(Fig. 12.26C).
• Secondary deviation in the uninvolved eye,
when the patient fixates with the paretic eye
is larger than the primary deviation.
2. Abnormal head posture is frequently associated
with incomitant exotropia. Face is turned towards
the action of the paralysed medial rectus.
3. Diplopia. A crossed horizontal diplopia with
maximal image separation while looking
towards opposite side and during near fixation
is appreciated (Fig. 12.27).
4. Ocular movements in a patient with paralysis
of medial rectus (e.g. of right eye) affected are
as below:
• Adduction in right eye is limited.
• Overaction of right eye on dextroversion
• Overaction of left eye on levoversion
• Underaction of left eye on dextroversion.
Differential diagnosis
Isolated medial rectus palsy should be differentiated from internuclear ophthalmoplegia (see
page 389).
Treatment
1. Conservative treatment is similar to that of
lateral rectus palsy (see page 328).
2. Surgical treatment, when indicated, consists
of:
• Recession of the antagonist lateral rectus
combined with resection of the involved
medial rectus. The amount of surgery depends
upon the size of deviation.
• Vertical rectus transposition to the medial rectus
muscle is also recommended as an alternative
procedure.
ISOLATED INFERIOR RECTUS MUSCLE PALSY
An isolated paralysis of the inferior rectus
muscle is extremely rare condition.
Etiology
1. Congenital. Inferior rectus palsy, a rare entity,
is often congenital.
332 Theory and Practice of Squint and Orthoptics
Fig. 12.28 Hess chart of a patient with right medial rectus paralysis.
2. Acquired. Occasionally, inferior rectus palsy
may be due to an injury of the orbit (either at
the time of injury or at the time of repair of the
orbital floor fracture), myasthenia gravis,
vascular diseases and following a peribulbar or
retrobulbar anaesthesia for any intraocular
surgery.
Clinical features
1. Deviation. In primary position, the involved
eye is hypertropic and slightly intorted due to
the unopposed action of the antagonistic superior
rectus muscle (Fig. 12.29A). When patient fixates
with the paretic eye, secondary deviation in the
opposite eye consists of depression and intorsion
more than the primary deviation.
2. Pseudoptosis can be appreciated in the normal
eye, when patient fixates with the paretic eye.
This occurs because of the drooping of the upper
lid associated with moving down of the globe.
3. Widening of palpebral fissure may be seen in
the paretic eye, when patient fixates with the
normal eye. This occurs due to upward
movement of the upper eyelid associated with
the elevation of the globe.
4. Abnormal head posture is often present and
consists of slight chin depression, face turn and
head tilt towards the affected side (Fig. 12.29B).
5. Diplopia (Fig. 12.30). Image seen by the
involved eye is lower, crossed and extorted;
vertical separation increases, when looking
down and to the same side; extorsion increases,
when looking towards the opposite side.
6. Ocular movements in a patient with inferior
rectus palsy (e.g. of right eye) are affected as
below (Fig. 12.29 I to IX):
• Movements of right eye are limited, when
looking down and right (Fig. 12.29 VII).
• Overaction of right eye on looking up and to
right (Fig. 12.29 I).
• Overaction of left eye on looking down and to
right (Fig. 12.29 VII).
• Underaction of left eye on looking up and to
right (Fig. 12.29 I).
7. Hess screen pattern seen in right inferior
rectus palsy is shown in Fig. 12.31.
Treatment
1. Conservative treatment is similar to as
described for lateral rectus palsy (see page 328).
2. Surgical treatment, when indicated should be
planned depending upon the size of the
deviation and results of forced duction test
(FDT) as below:
i. Recession of the superior rectus should be
performed, if FDT shows restriction of this
muscle.
Incomitant Strabismus
333
Fig. 12.29 A patient with right inferior rectus paralysis: (A) Right hypertropia with left eye fixating; (B) Abnormal head
posture; and I to IX, Ocular movement in nine positions of gaze (Courtesy: Dr Subhash Dadeya).
ii. Resection of inferior rectus is preferred, when
FDT is negative and deviation is small.
iii. Resection of inferior rectus and recession of the
superior rectus should be combined, if the
deviation is large. This surgery can correct
up to 30–40D of vertical deviation in the
primary position.
iv. Other options include IR plication, reverse
Knapp, IO anterior transposition.
ISOLATED SUPERIOR RECTUS PARALYSIS
An isolated paralysis of superior rectus muscle
is a rare entity. Since the superior division of
the third cranial nerve innervates both superior
rectus and levator muscle, so weakness of
superior rectus may be associated with
Fig. 12.30 Diplopia chart of a patient with right inferior
rectus paralysis.
weakness of levator and thus a ptosis in the
affected eye.
334 Theory and Practice of Squint and Orthoptics
Fig. 12.31 Hess chart of a patient with right inferior rectus paralysis.
Etiology
1. Congenital. Isolated superior rectus muscle
palsy is usually congenital.
2. Acquired. SR palsy may be secondary to
trauma (e.g. after a bridle suture during cataract
surgery) or occasionally be associated with
vascular disorders and viral infections.
A
Clinical features
1. Deviation. When the normal eye is fixing, the
paretic eye is hypotropic in primary position
(Fig. 12.32A). Usually, there is no vertical
deviation in adduction. The inferior rectus
overacts and consequently objective excyclodeviation develops which can be detected by indirect
ophthalmoscopy or by plotting the blind spot in
the visual field. Subjective cyclodeviation is
typically absent, since in most cases the condition
is congenital. When patient fixates with the
paretic eye the normal eye is hypertropic, slightly
abducted and slightly extorted; more than the
primary deviation (Fig. 12.32B).
2. Ptosis may be associated in the affected eye,
if LPS is also weak.
3. Pseudoptosis may be associated with the
hypotropic globe in primary position (Fig. 12.32A).
It must be differentiated from the true ptosis.
Pseudoptosis disappears, when the patient
fixates with the paretic eye.
B
Fig. 12.32 A patient with right superior rectus paralysis and
pseudoptosis and hypotropia in the affected eye while
fixating with the left nonaffected eye (A). When fixating with
the paretic right eye, pseudoptosis disappears and the
nonparetic left eye becomes hypertropic (B).
4. Abnormal head posture is not always present
in patients with superior rectus palsy. However,
in some recent cases, chin may be elevated, face
turned to the same side and head tilted towards
the normal side. In most patients, after
sometimes, head is tilted towards the same side
due to overaction of the yoke muscle (opposite
inferior oblique).
5. Diplopia may be present in recent cases only.
For example, in a patient with paralysis of right
superior rectus, image seen by the involved eye
is higher, crossed and intorted (Fig. 12.33).
Vertical separation increases, when looking up
and to the right; intorsion increases, when
looking to left.
6. Ocular movements in a patient with right sup-
erior rectus muscle paralysis are affected as
below:
• Movements of right eye are limited, when
looking towards up and right.
• Overaction of right eye on looking down and
to right.
• Overaction of left eye on looking up and to
the right.
• Underaction of left eye on looking down and
to right.
7. Hess screen charting pattern seen in right
superior rectus palsy is shown in Fig. 12.34.
Differential diagnosis
1. Primary superior rectus palsy needs to be
differentiated from the inhibitional palsy of the
superior rectus (contralateral antagonist)
secondary to weakness of the superior oblique
muscle of the opposite eye.
Incomitant Strabismus
Fig. 12.33 Diplopia chart of a patient with right superior
rectus palsy.
335
2. Paretic weakness of the superior rectus
should be differentiated from the restrictive
limitation of movements following entrapment
of inferior rectus and/or soft tissue in fracture
floor of the orbit and contracture of inferior
rectus following myositis, after cataract surgery,
ocular epibulbar anaesthesia.
Fig. 12.34 Hess chart of a patient with right superior rectus palsy.