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362 Color Atlas of Ophthalm ology

Weber Syndrome

In Weber syn drom e th e lesion is in th e area of th e cor t icospin al (pyram idal) t ract . Th is leads to an ipsilateral th ird -n er ve paresis w ith con t ralateral h em iparesis.

Uncal Hernia tion Syndrome

As th e th ird cran ial n er ve goes tow ard th e cavern ous sin u s, it rests on th e edge of th e ten torium cerebelli. A supraten torial space-occu pying m ass located anyw h ere in or above th is cerebral h em isph ere m ay cau se a dow nw ard disp lacem en t an d h ern iat ion of th e u n cus across th e ten torial edge, th ereby com pressing th e th ird n er ve. Th is leads to a dilated an d fixed pu pil. Th is is called th e Hutch in son pu pil an d is th e first in dicat ion th at altered con sciousn ess is du e to a sp ace-occupying in t racran ial lesion (Fig. 13.1D).

Posterior Communicating Artery Aneurysm

As th e th ird cran ial n er ve m oves tow ard th e cavern ou s sin us, it t ravels alongside th e posterior com m un icat ing ar ter y. If th ere is an an eur ysm of th e posterior com - m u n icat ing ar ter y it can lead to com p ression of th e th ird n er ve. Th is leads to an isolated th ird -n er ve paresis w ith th e pu pil becom ing involved (Fig. 13.1E).

Cavernous Sinus Syndrome

In cavern ou s sin us syn drom e, th ere w ould be th ird -n er ve paresis w ith involve- m en t of oth er n er ves, such as cran ial n er ves IV, V, an d VI. Th ese p at ien ts h ave pain - ful oph th alm oplegia, possibly du e to t raum a, n eoplasm s, an eu r ysm s, or in flam m a- t ion s. Th is syn drom e can lead to aberran t regen erat ion of th e th ird cran ial n er ve.

Orbita l Syndrome

Proptosis can be an early sign . Th e fifth cran ial n er ve can also be involved, but th is w ou ld involve on ly th e oph th alm ic division .

Pupil-Spa ring Isola ted Third-Nerve Pa resis

Th e pu pillom otor fibers t ravel in th e th ird n er ve in th e outer layers an d are th erefore closer to th e n u t rien t blood su pply enveloping th e n er ve. Th is is th e reason w hy th e pu pillom otor fibers are gen erally spared in isch em ic th ird -n er ve paresis but are affected in com pressive lesion s su ch as t u m ors. Ocu lar m yasth en ia can m im ic a pu pil-sparing th ird -n er ve palsy, so on e can perform th e Ten silon test to differen t iate th e t w o.

Differential Diagnosis

Oth er causes of paralyt ic an d rest rict ive squ in t s

Management

Occlusion

On e can occlu de th e paret ic eye un t il th e h ealing occurs an d th e th ird -n er ve paresis is cu red .

Medica l Trea tment

On e can give th e pat ien t m ult ivitam in inject ion s an d t ablet s an d t reat th e cause, like diabetes or hyperten sion .

Surgica l Trea tment

Th e su rgical m an agem en t of a com plete th ird -n er ve paralysis is a difficult job. At th e ver y best , th e surgeon w ill succeed on ly in m oving th e paret ic eye in to th e prim ar y posit ion w ith ou t restoring adduct ion , elevat ion , or depression to a sig- n ifican t degree. A ver y good m eth od to t reat th is con dit ion is to do a ten otom y of th e lateral rect us an d th e su perior obliqu e com bin ed w ith a t ran sposit ion of th e

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A

B

13 Neuro-Ophthamology 365

C

D

Fig . 13.2 (A) Trochlear nerve anatomy. (B) Lesions of the trochlear nerve. (C) Bielschowsky’s head tilting test for R/L (right/left) hypertropia. (D) Bielschowsky’s head tilting test for L/R (left/right) hypertropia. LIO, left inferior oblique; LSR, left superior rectus; RIR, right superior rectus; RSO, right superior oblique.

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Ocular m ovem ents: Depression is lim ited in adduct ion . In torsion is also lim ited . Hom onym ou s vert ical diplopia occu rs on looking dow nw ard . Usually th e vision is single as long as th e eyes look above th e h orizon t al plan e. Th e pat ien t especially n ot ices diplopia w h en w alking dow n th e st airs.

Abnorm al head post ure: To avoid diplopia, th e h ead t akes an abn orm al post u re

tow ard th e act ion of th e superior oblique m u scle (i.e., th e face is sligh tly t u rn ed to th e opposite side, th e ch in is depressed, an d th e h ead is t ilted tow ard th e op - posite sh oulder).

Checking Fourth-Nerve Function in the Set ting of a Third-Nerve Pa resis

Th e problem w ith ch ecking th e four th cran ial n er ve fu n ct ion if a pat ien t also h as a th ird cran ial n er ve paresis is th at th e involved eye can n ot be adducted w ell because of th ird cran ial n er ve involvem en t . Because th e eye can n ot be adducted, on e can n ot test th e ver t ical act ion (depression ) of th e su perior obliqu e m u scle.

To solve th is problem , first of all w e sh ould n ote a lim bal or conjun ct ival lan d - m ark, such as a blood vessel or pter ygium . Th e pat ien t , on being asked to look dow n , w ill n ot be able to do so as th e eye is abdu cted an d n ot adducted (becau se of th ird -n er ve involvem en t). Bu t th e eye w ill in tor t as th e su perior oblique m u scle w orks. We sh ould th en ch eck from th e conjun ct ival lan dm ark if th e eye is in tor t- ing. If th e conju n ct ival lan dm ark is m oving, th e eye is in tor t ing, an d th at m ean s th e fou r th n er ve is in t act .

Bielschowsky Hea d-Tilting Test

Th e Bielsch ow sky h ead -t ilt ing test can diagn ose w h ich m uscle is paralyzed . Let us first look at a case of R/L hypert ropia in w h ich th e righ t eye is at a h igh er posit ion th an th e left eye (Figs. 13.2C,D).

R/L Hypertropia

If th e pat ien t h as an R/L hyper t ropia, th en it could m ean th at th e righ t eye is hypert ropic, in w h ich case th e depressors are paralyzed like th e righ t in ferior rect u s (RIR) or th e righ t superior oblique (RSO). It cou ld also m ean th at th e righ t eye is in th e n orm al posit ion but th e left eye is hypot ropic. Th is could be du e to th e elevators of th e left eye being paralyzed like th e left in ferior obliqu e (LIO) an d th e left su perior rect u s (LSR). Th is is th e first step of th e test . We h ave th u s n arrow ed dow n th e diagn osis to fou r of th e ext raocu lar m u scles.

Now w e perform th e secon d step of th e test . In th is w e ask th e pat ien t to perform dext roversion or levoversion . Th is m ean s w e ask th e pat ien t to look to th e righ t an d to th e left . If w e ask th e p at ien t to look to th e righ t , th e righ t eye cou ld be h igh er th an th e left eye. If th e righ t eye is h igh er on dext roversion , th en it could m ean th at th e RIR is involved or it cou ld m ean th at th e left eye is hypot ropic. Th is w ou ld be due to an LIO paralysis. In levoversion if th e righ t eye is h igh er, it could be du e to an RSO paralysis. Altern ately, it could m ean th at th e left eye is hyp ot ropic, an d th is w ou ld be due to LSR paralysis. Th us w e h ave n arrow ed dow n th e m uscles from fou r to t w o.

Fin ally, w e perform th e th ird step in w h ich w e t ilt th e pat ien t’s h ead to th e righ t an d th en to th e left . If w e t ilt th e h ead to th e righ t , th e righ t eye w ill in tor t an d th e left eye w ill extor t . Th is is becau se n er vou s im pu lses w ill be sen t from th e sem icircu lar can als to keep th e eyes in a st raigh t posit ion . Rem em ber, the superiors are intorters. So if th e righ t eye in tort s, it m ean s th e superiors in th at eye (RSR an d RSO) w ork, an d if th e left eye extort s it m ean s th e in feriors of th at eye (LIO an d LIR) w ork. W h en th is h appen s in th e righ t eye th e RIR w ill n ot be u sed at all because it is an extor ter, an d in th e righ t eye extor t ion is n ot t aking place. But in th e left eye, extor t ion w ill take place an d th e LIO an d LIR w ill w ork. Now as th e LIO is paralyzed, on ly th e LIR act s in th at eye. As a balan ce is n ot be m ain t ain ed bet w een th ese t w o m u scles, th e left eye m oves dow n as th e LIR is also a depressor. Th us, on e can diagn ose a pat ien t w ith LIO paralysis.

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If w e ask th e pat ien t to t ilt th e h ead to th e left , th e left eye w ill in tor t an d th e righ t eye w ill extort . In th e righ t eye th e extor ters w ill be th e RIR an d righ t in ferior obliqu e (RIO). Now th e RIR is paralyzed, an d so on ly th e RIO w ill w ork an d th e righ t eye w ill m ove u pw ard .

Sim ilarly, w e can differen t iate bet w een th e RSO an d th e LSR in th e th ird step . If w e t ilt th e h ead to th e righ t th e righ t eye w ill in tor t , an d th e m uscles th at w ill w ork are th e RSO an d RSR. Becau se th e RSO is paralyzed on ly th e RSR w ill w ork, an d th e righ t eye w ill m ove u pw ard .

If w e t ilt th e h ead to th e left , th e left eye w ill in tor t , an d th e m uscles th at w ill w ork are th e LSR an d LSO. If th e LSR is paralyzed th e LSO w ill w ork an d th e left eye w ill m ove dow n .

L/R Hypertropia

If w e n ow w ork on th e sam e prin ciple an d get th e m u scle involved in an L/R hyper- t ropia. If th e pat ien t h as an L/R hyper t ropia, th en it in dicates th at th e depressors are paralyzed like th e LIR or th e LSO. It cou ld also m ean th at th e left eye is in th e n orm al p osit ion bu t th e righ t eye is hypot ropic. Th is could be du e to th e elevators of th e righ t eye, n am ely, th e RIO an d th e RSR, being paralyzed . Th is is th e first step of th e test . Of th e ext raocu lar m u scles w e h ave n arrow ed th e diagn osis of ext raocu lar m u scle paralysis to fou r m u scles, th e t w o depressors of th e righ t eye, or th e t w o elevators of th e left eye.

Next , w e perform th e secon d step of th e test . In th is w e ask th e pat ien t to perform dext roversion or levoversion . Th is m ean s w e ask th e p at ien t to look to th e righ t an d to th e left . If w e ask th e pat ien t to look to th e righ t , th e left eye cou ld be h igh er th an th e righ t eye. If th e left eye is h igh er on dext roversion , th en it could m ean th at th e LSO is involved or it cou ld m ean th at th e righ t eye is hypot ropic. Th is w ou ld be due to an RSR paralysis. In levoversion if th e left eye is h igh er it cou ld be due to an LIR paralysis. Altern ately, it could m ean th at th e righ t eye is hypot ropic, w hich w ou ld be due to RIO paralysis. Th u s w e h ave n arrow ed dow n th e m uscles from fou r to t w o.

Fin ally, w e perform th e th ird step, in w h ich w e t ilt th e pat ien t’s h ead to th e righ t an d th en to th e left . If w e t ilt th e h ead to th e left , th e righ t eye w ill extort an d th e left eye w ill in tort . Th is is becau se n er vou s im pulses w ill be sen t from th e sem icircular can als to keep th e eyes in a st raigh t posit ion . Rem em ber th at th e superiors are in tor ters. So if th e righ t eye extor t s, it m ean s th e in feriors in th at eye (LIO an d LIR) w ork, an d if th e left eye in tor ts it m ean s th e su periors of th at eye (RSO an d RSR) w ork. W h en th is h appen s, in th e left eye th e LSO an d LSR sh ou ld w ork. Now th e LSO is paralyzed an d so can n ot w ork. Th erefore, on ly th e LSR w ill w ork to in - tort th e eye. An d becau se th e balan ce w ill n ot be m ain t ain ed bet w een th ese t w o m uscles, th e left eye w ill m ove u p given th at th e LSR is also an elevator. Th u s on e can diagn ose th e case of LSO.

If we ask the patient to tilt the head to the right, the left eye w ill extort and the right eye w ill intort. In the right eye the intorters w ill be the RSR and RSO. Since the RSR is paralyzed, only the RSO w ill work. This w ill cause the right eye to m ove dow nward.

Sim ilarly, w e can differen t iate bet w een th e LIR an d th e RIO in th e th ird step . If w e t ilt th e h ead to th e left , th e righ t eye w ill extor t an d th e m uscles th at w ill w ork are th e RIO an d RIR. Becau se th e RIO is paralyzed on ly th e RIR w ill w ork to extor t th e eye, th ereby m oving th e righ t eye dow nw ard .

If w e t ilt th e h ead to th e righ t , th e left eye w ill extort an d th e m u scles th at w ill w ork are th e LIR an d LIO. If th e LIR is paralyzed th e LIO w ill w ork an d th e left eye w ill m ove u p .

Differential Diagnosis

Prim ar y in ferior obliqu e over act ion

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Management

Occlusion

W h en double vision is rest ricted to dow nw ard gaze as in fou rth -n er ve paralysis, on e can occlu de th e low er th ird of th e spectacle len s in fron t of th e paret ic eye w ith sem iopaqu e tape. Th is can be perform ed if th e m edical con dit ion is n ot suitable for su rger y.

Surgery

Depen ding on th e class of su perior oblique (SO) paralysis, th e su rgical t reat m en t is based on th e class of paralysis as described by von Noorden (Table 13.1).

Table 13.1 Treatm ent of Superior Oblique Paralysis Based on Class

A

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Abducens (Sixth) Nerve Palsy

Th e abdu cen t (sixth cran ial) n er ve is a sm all, en t irely m otor n er ve th at supplies th e lateral rect u s of th e eyeball (Figs. 13.3A,B).

B

C

Fig . 13.3 (A) Nucleus of the abducent nerve and the brainstem syndromes. (B) Course of the abducent nerve. (C) Lesions of the abducent nerve.

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Presentation

In th e prim ar y posit ion th e eyeball is converged becau se of th e un opposed act ion of th e m edial rect u s m uscle. Abduct ion is lim ited du e to w eakn ess of th e lateral rect us m u scle. Un crossed h orizon tal diplopia occu rs, w h ich becom es w orse to- w ard th e act ion of th e paralyzed m u scle. Th e face is t urn ed tow ard th e act ion of th e paralyzed m u scle to m in im ize diplopia.

Lesions

Various lesion s of th e abducen t n er ve in it s cou rse can p rodu ce variou s syn drom es as described in th e follow ing sect ion s (Fig. 13.3C).

The Bra instem Syndrome

A brain stem lesion of th e sixth n er ve m ay also affect th e fifth , seven th , an d eigh th cran ial n er ves an d also th e cerebellu m . Th e sixth -n er ve n u cleu s also h as con n ec- t ion s via th e m edial longit u din al fasciculu s w ith th e th ird -n er ve n u cleu s, an d so a lesion h ere produces a gaze palsy. Th ree syn drom es can occu r in th e brain stem :

1. MillardGubler syndrom e: In th is th e lesion is ven t ral an d involves th e facial n er ve an d th e pyram idal t ract . Th us th ere is a sixth -n er ve paresis, ip silateral seven th -n er ve p aresis, an d con t ralateral h em iparesis.

2. Raym ond syndrom e: In th is syn drom e th e lesion involves on ly th e sixth cran ial n er ve an d th e pyram idal t ract . Th u s th e pat ien t h as a sixth -n er ve paresis an d con t ralateral h em iparesis.

3. Foville syndrom e: In th is th e lesion is dorsally. Because th e lesion is dorsal th e areas affected are th e m edial longit udin al fasciculus, th e pon t in e param edian ret icu lar form at ion , th e fifth n er ve, an d th e sym path et ic n euron s. Th u s th e pat ien t h as h orizon tal conjugate gaze palsy an d palsies of th e ipsilateral fifth , sixth , seven th , an d eigh th n er ves w ith ipsilateral Horn er syn drom e.

Subarachnoid Space Syndrome

Elevated in t racran ial p ressure m ay resu lt in dow nw ard displacem en t of th e brain - stem , w ith st retch ing of th e sixth n er ve, w h ich is teth ered at its exit from th e pon s an d in th e Dorello can al. Th is gives rise to n on localizing sixth -n er ve palsies of raised in t racran ial pressu re. Th ir t y p ercen t of pat ien ts w ith pseudot um or cerebri h ave sixth n er ve paresis, besides papilledem a an d it s visu al field ch anges.

Petrous Apex Syndrome

Th e sixth n er ve passes un der th e Gru ber ligam en t in th e Dorello can al. Th is m akes th e n er ve liable to paralysis due to a lesion of th e pet rou s apex.

Gra denigo Syndrome

Graden igo syn drom e is due to a localized in flam m at ion or ext radu ral abscess of th e pet rous apex follow ing com plicated ot it is m edia. Th is lesion can lead to th e follow ing:

Sixth -n er ve palsy

Ipsilateral decreased h earing (eigh th -n er ve involvem en t)

Pseudo-Gra denigo Syndrome

Th is syn drom e is seen in t w o con dit ion s:

Nasopharyngeal carcinom a: Th is m ay cau se serou s ot it is m edia due to obst ru c- t ion of th e eu stach ian t u be, an d th e carcin om a m ay su bsequen tly invade th e cavern ou s sin us, cau sing sixth -n er ve paresis.