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Show ]. Clin. Neuro-ophthalmol. 1: 199-208, 19tH. Diagnosis of Superior Oblique Palsy* WAYNE W. BIXENMAN, M.D. Abstract Superior oblique muscle palsy is not only the most frequent cause of acquired vertical strabismus, anomalous head posturing and torsional diplopia, but also the most common isolated oculomotor paralysis seen n everyday ophthalmic practice. Adults typically present to the ophthalmologist with asthenopic symptoms of long duration, while children present with objective clinical signs. An understanding of the available subjective and objective examination techniques will enable the c1iniciDl to diagnose the presence of this cyclovertical muscle paralysis. There are clues from the examination that suggest a superior oblique palsy of long duration, which may save the patient a needless neurological workup and a 6-month wait before surgical options can be considered. There are also clues from the examination that suggest the presence of a "masked" bilateral superior oblique palsy. . Most cases of previously diagnosed skew deviation, If examined closely, will actually tum out to be mild trochlear nerve pareses. Superior oblique muscle palsy is the most frequent cause of acquired vertical strabismus, anomalous head posture, and torsional diplopia. All clinicians, especially ophthalmologists, neurologists and neurosurgeons, should be familiar with the techniques of patient examination required to properly diagnose this cyclovertical muscle palsy. Superior oblique palsies are of special interest to the ophthalmologist. For 40 years, it has been well known that superior oblique palsies account for over 90% of acquired vertical strabismus. I In addition, superior oblique palsies are the most frequent isolated oculomotor palsy seen in practice. 2 This ophthalmic experience, however, is seldom reported in neurologic practice and does not appear to be substantiated in recent reviews where isolated fourth nerve palsy accounted for only 170/0 of paralytic strabismus.3 • 4 This is probably due to the fact that the symptoms of a superior oblique palsy may be subtle, variable or even absent, and that • Presented at the Tucson Ophthalmological Society Meeting, St. Joseph's Hospital, Tucson, Arizona, March 24, 1981. September 1981 patients are not often as handicapped as with third or sixth nerve palsies. Because of the often incipient presentation of fourth nerve palsies, the diagnosis is missed, overlooked, or ignored. Clinical Presentation Adults with superior oblique palsy typically present to the ophthalmologist with subjective asthenopic symptoms. Childhood superior oblique palsies are usually diagnosed on the basis of objective clinical signs. The age at diagnosis will vary from 6 months to 60 years, but an average of 24 years has been reported. 2 Patients with acquired superior oblique palsy on the average have been symptomatic for 4-5 years, while congenital cases usually h~ve had signs or symptoms for 10-11 years. ThiS remarkable time interval probably reflects not only the subtle mode of presentation and a delay in diagnosis, but also conservatism in management on the part of the ophthalmologist with a reluctance to consider surgical options. The neurologist and the neurosurgeon are more likely to see the acutely ill patient in a hospital setting. Here the superior oblique palsy is usually overshadowed by the associated neurological presentation, becoming manifest only in the convalescent period. Diplopia when present, is classically torsional with a variable vertical component. In long-standing or congenital superior oblique palsies, diplopia is a very uncommon complaint, with the single exception being "decompensated congenital paresis." Patients are troubled most in downgaze, 50 that asthenopic symptoms when reading or with the first pair of bifocals is a common outpatient presentation. A good correlation has been found to exist between the age of onset of a cyclodeviation, the presence of symptoms, and the results of subjective testing.' Patients with cyclodeviations that onset in early age are not likely to be symptomatic, and there is often a discrepancy between the amount of cyclotorsion subjectively reported and the amount objectively found. On the other hand, cyclodeviations of recent onset show a good correlation between the severity of symptoms and the degree of subjective and objective cyclotorsion. 199 Superior Oblique I'.llsy This phenomenon of sensory .1daptations to cyc1odeviations has been reviewed'; and includes sensory cyclofusion, a reordering of spatial response of ;etinal elements along new horizontal and vertical meridians .1S well as various empirical factors. The results of these unique sensory adaptations is the elimination of visual discomfort in patients with long-st.mding cyclodeviations. Presumably these me.lsures may be only temporizing. With adv.1l1cing age or in periods of stress or illness, the patient may decompensate ("decompensated congenital paresis") and become symptomatic years after the actual onset of the palsy. Etiology of Superior Oblique Palsy Congenital Superior Oblique Palsy In childhood, two-thirds of superior oblique palsies are "congenital,"" while when considering superior oblique palsies in all ages, one-third are of "indeterminate" etiologl and are often presumed to be of "congenital" origin, especially if a longstanding head tilt can be documented. Superior oblique palsy of congenital origin may present in childhood with anomalous head posturing (Fig. 1), often as an incidental finding during a routine examination. As previously noted, congenital superior oblique palsies may present in adulthood ("decompensated congenital paresis") during a concurrent illness or with a long history of intermittent asthenopia. Frequently patients are referred for assessment because they are requiring Figure 1. A 7-year-oJd child demonstrating typic. hudtilt.of ,I ""ht ,upNior oblique palsy. greater vertical prism strength in their spectacles. Old photographs help to document the chro~icity of the torticollis, quite often to the total surprIse of the patient! Traumatic Superior Oblique Palsy I suspect that trauma is likely the most common etiology, as one can never entirely rule out a traumatic cause in some"congenital" cases. A clearcut history of trauma precipitating the superior oblique palsy is available. only in one-third of patients reviewed, however,'l.4 . . Typically the patient has sustamed ~ concussIOn from a minor closed-head trauma WIth a fall or motor vehicle accident, usually unassociated with other central nervous system signs, although not invariable so. The patient may then have noted periodic, annoying diplopia weeks to months after the accident, which "recovered" only to reappear months to years later. Others have noted symptoms immediately after the incident which progressively worsened with time. The reader should recall that it is the trochlear (fourth) nerve and not the abducens (sixth) nerve that has the longer intracranial course. The fourth nerve exits dorsally from the midbrain, decussating in the anterior medullary velum (the site of presumed predisposition to the effects of trauma) prior to passing anteriorly toward the superior orbital fissure. The left fourth nerve motor nucleus supplies the right superior oblique muscle, and vice versa. Other Causes of Superior Oblique Palsy Superior oblique palsy due to vascular, demyelinating, or neoplastic disease is virtually nonexistent in childhood.3 In adults, such superior oblique palsies are usually seen in conjunction with other cranial nerve involvement or in the context of the underlying neurological or medical disease process. 4. 7 Exceptions to this generalization occur with regularity, and an acquired superior oblique palsy in adulthood mar be the presenting feature of a systemic disease. Physiology of the Superior Oblique Muscle Understanding the physiology of the superior oblique is the basis for understanding the various diagnostic techniques. The tendon of the superior oblique approaches the globe obliquely at an angle of 540 from the visual axis. The tendinous insertion fans out under the superior rectus muscle and is on the average, 10-11 mm wide. The anterior portion of this tendinous insertion is primarily responsible for incyclotorsion, while the posterior portion is primarily responsible for depression. In primary position, the primary function of the superior oblique is incycJotorsion (agonist = superior rectus; antagonist = inferior oblique), the secondary function is depression (agonist = inferior rectus; antagonist = superior rectus) and the tertiary function is abduction (agonists = lateral rectus and inferior oblique). With increasing adduction, the superior oblique becomes more of a depressor but, regardless of gaze position, the inferior rectus remains the primary depressor of the globe. The action of the superior oblique is most evident in total third nerve palsies. When the ptotic lid is elevated and the patient is asked to look down from the exotropic position, a modest depression is witnessed associated with a pronounced incyclotorsion (watch the conjunctival vessels). In combined third and fourth nerve palsies, this incyclotorsion is not seen. Patient Examination Ocular Torticollis The classical posture is a head tilt to the opposite shoulder with a chin depression (Fig. 1). This finding is by no means invariable. Of the 25 cases of superior oblique palsy seen over the last 2 years, 21 (84%) have had anomalous head posturing. Of these, 19 (76%) were "typical" head tilts, one (4%) was"atypical" (to the ipsilateral side) and one (4%) had a chin down position (bilateral superior oblique palsies). Four cases (16%) had normal head posture. Of these, one (4%) had bilateral fourth nerve palsies, two (8%) had fusional control of a minimal hyper- Bixenman deviation in primary position, and one (4%) had "supranormal" fusional amplitudes. Hence, the absence of a torticollis does not rule out a superior oblique muscle paralysis. The patch test may be useful in assessing torticollis cases. Head tilts of nonocular origin will not be affected by occlusion of either eye. If the torticollis is of ocular origin, then occluding the offending eye may allow assumption of normal head posture, while occlusion of the normal eye would not be expected to affect the torticollis. Unfortunately this test is not foolproof, but may on occasion provide useful information, especially when confronted with a case of idiopathic torticollis in childhood. Subjective Clinical Tests The red lens test to determine the gaze position of maximal separation of images (i.e., where the diplopia is greatest) is seldom useful to the ophthalmologist who typically sees these patients months to years after the onset of the palsy (see Knapp Classification). Neurologists and neurosurgeons who see patients in the acute setting place greater emphasis on this technique and will often "rule out" a fourth nerve palsy solely on the basis of this test. The red glass test has many shortcomings and all clinicians should be aware that this is not the proper manner to diagnose fourth nerve palsies. The double Maddox rod test is the most valuable subjective test. An average of 6_80 of excyclotorsion is typicaIlr found with unilateral superior oblique palsies. This technique is reviewed elsewhere. a I prefer to use the white and red Maddox Figure 2. Double Maddox rod test. While and red B& L Maddox rods in lriallens frame with axes set at 12 o'clock (i.e., 90°). September 1981 201 Superior Oblique Palsy rods available from Bausch & Lomb which have the axis indicated on the lens. These are placed in the trial lens frame with the axes at 12 o'clock (Fig. 2). The reader should recall that in- and ex-cyclotorsion refer to the relative movement of the 12 o'clock meridian of the cornea medially (incyclotorsion) or laterally (ex cyclotorsion). Instead of the confusing interpretation of what the patient actually sees, permit the patient to adjust the two Maddox rods himself until both lines appear horizontal and parallel. Then read the number of degress of excyclotorsion in one or both eyes directly from the trial lens frame. It is important to check the degree of excyclotorsion not only in primary position but also in downgaze, where a marked increase in the amount of excyclotorsion may be found (up to 12-16°). Ophthalmologists who prefer to use the Maddox rods in their Bausch & Lomb phoroptor should note that the axes of these Maddox rods are located at 6 o'clock, which affects the interpretation accordingly. Clinicians who use Maddox rods from other trial lens sets will note that the axes are not indicated, while those in other phoroptors are fixed in position. The problem with these is fourfold. First of all, one has to interpret what the patient actually sees to make sure that the subjective cyc1otorsion reported is actually excyclotorsion (patients with fourth nerve palsies never note incyclo-torsion). Second, it is hard to check for cyclotorsion in downgaze when using a phoroptor. Third, it is difficult sometimes to tell whether or not the patient actually has bilateral subjective excyclotorsion. Fourth, since the axes are not indicated or the lenses are fixed in position, one can not quantitate the amount of subjective excyclotorsion present. Plotting diplopia fields (i.e., where the patient has single and double vision) with the Goldmann or Aimark perimeter is very useful in assessing the range of single vision that the patient enjoys, as well as for documentation of improvement on serial follow-up. Showing the diplopia field to the patient frequently is of considerable psychological benefit for he can actually "see" the extent of his problem and how much he has improved on follow- up or with therapy. There are other subjective tests, including the Hess screen examination, tangent screen examination (plotting the position of the blind spot), Maddox double prism test, etc., that may be useful on occasion but are in general, time-consuming and seldom provide the clinician with information of additional value. Objective Clinical Tests The objective assessment of ductions and versions is the most critical part of the examination, as in any case of paralytic strabismus. These can Figure 3. Diagnostic gaze positions in a case of traumatic bilateral superior oblique palsies Note the unde t' f b h . bl'. h' . . '" . rae Ion 0 ot supenor o "!u', (-3). t "mInimal overacllon of both mfenor obhques (+/-), and the V pattern to the strabismus. 202 Journal of Clinical Neuro-ophthalmology Bixenman Figure 4. Steps #1 and #2 of the three-step test of Parks in a case of a right superior oblique palsy. Note the small right hyperdeviation in primary position (step #1-center photo), that increases markedly on left gaze (step #2-right photo). Figure s. Step #3 of the three-step test of Parks (same case as in ,fig. 4). Note that head tilt to the right (left photo) results in marked increase in the right hyperdeviation. be subjectively graded by the individual examiner as to the amount of underaction (0 to -4) and overaction (0 to +4). The typical pattern seen is an underaction of the paretic superior oblique with an overaction of the antagonist inferior oblique. For follow-up as well as for legal purposes, it is helpful to document the versions in the nine diagnostic gaze positions by external ocular photography. It is not necessary to go to the trouble to make up the familiar collage of the cardinal gaze positions (Fig. 3). The clinical assessment of the saccadic eye movements is not as important here as it is in other causes of paralytic strabismus. The three-step test of Parks 9 must be mastered by all clinicians who follow these patients. This test incorporates the principle of lateral gaze incomitance with the Bielschowsky head tilt test. Through each step, one progressively eliminates the various diagnostic possibilities. Step #1: Is a hyperdeviation [HT] present? (Is it a right hypertropia [R-HT] or a left hypertropia [L-HT] 7) Step #2: Does the HT increase on gaze left or right? September 1981 Step #3: Does the HT increase on head tilt to the left or right shoulder? The following is a case example of the patient shown in Figures 4 and 5. Step #1: A patient is found to have a right hypertropia [R-HT]. [Diagnostic possibilities = depressor paralysis of the higher RIGHT eye (i.e., RIR or R-SO), or elevator paralysis of the lower LEFT eye (i.e., L-SR or L-IO).] Step #2: The HT is found to increase on gaze left (Fig. 4). [Diagnostic possibilities = paralysis of the depressor in adduction of the right eye (i.e., R-SO), or paralysis of the elevator in abduction of the left eye (i.e., LSR).] Step #3: The HT is found to increase on head tilt to the right (Fig. 5). [Diagnosis = paralysis of the incyclotortor of the right eye (i.e., R-SO).] Note: (a) The R-SR, the other incyclotortor of the right eye, was eliminated as a diagnostic possibility 203 Superior Oblique Palsy in step #1. (b) The only excyclotortor of the left eye that was considered a diagnostic possibility in step #1 (i.e., L-lO), was eliminated in step #2. A useful rule to remember is that superior oblique palsies are" marching" palsies, i.e., "leFtright- left" (a L-SO palsy produces a left hyperdeviation, that increases on gaze right and head tilt to the left), or "right-left-right" (a R-SO palsy produces a right hydeviation, that increases on gaze left and head tilt to the right). The clinician should recall the principle of the head tilt test. Head tilt to one shoulder will elicit a cycloversional response in the opposite direction, with incyclotorsion of the ipsilateral eye and excyclotorsion of the contralateral eye. The superior rectus and the superior oblique muscles are agonists with regard to incyclotorsion but are antagonists with regard to their vertical action. Head tilt to the side of the superior oblique palsy will thus result in the unchecked, vertical action of the superior rectus as compensatory incyclotorsion is elicited, so that the hyperdeviation increases. When measuring the vertical deviation by prismcover testing, always keep the base of the prism parallel to the floor of the orbit. The prism is correspondingly tilted as the patient's head is tilted. 10 This cyclovertical response is a static otolithic reflex that is an attempt to maintain the proper vertical orientation of the retinal meridians with head tilt to either side. This reflex cyclotorsion is elicited only when the patient is erect. When the patient is recumbent, as when lying on a stretcher in the emergency room, this reflex is absent. In trauma cases, always make sure that a cervical fracture has been ruled out first! Even in patients with superior oblique palsy but without torticollis, the head tilt test may still be positive.2 Patients with bilateral superior oblique palsies are likely to have bilaterally positive head tilt tests. Do not be confused when you see these patients. The"marching" rule remains; i.e., a hyperdeviation mayor may not be present in primary position, but a left hyperdeviation is present on gaze right, and head tilt to the left, and a right hyperdeviation is present on gaze left and head tilt to the right. Prism-cover testing in the nine diagnostic gaze positions with either eye fixing (recall primary and secondary deviations) is essential for documentation if you are to follow these patients. It may also be used as the basis for determining the surgical approach (see Knapp Classification). A deviometer is very useful for this purpose (Fig. 6), permitting a constant reproduction of gaze deviations for prism-cover testing on serial follow-up. Vertical fusional amplitudes, measured with a rotary prism (hand-held or in the phoroptor), may provide additional information in some patients. Superior oblique palsies of long duration or congenital origin often have supranormal vertical fusional amplitudes, in clear distinction to superior oblique palsies of recent onset. II The range of the normal variation of the relative position of the fovea with respect to the optic nerve head has been documented and will be presented elsewhere. 12 The clinician can use the indirect fun- 2.04 Figure 6. The Henry Deviometer. Available in variable working distances and arm s"ttinRs. with or without accommodative targets. Write: Robert H. Henry, 3735 Knollwood Circle, Tucson, AZ 85715. Journal of Clinical Neuro-ophthalmology doscopic examination to determine the presence of objective excyclotorsion (Fig. 7). We have found that if the relative horizontal position of the fove,l is below the lower edge of the optic nerve he'ld, this is out of the range of normal and objective excyclotorsion is present. If a fundus camerJ is available, this can be documented by fundus photography. Knapp Classification Dr. Philip Knapp h,lS provided a useful classification of superior oblique palsies depending on the gaze position of maximal hyperdeviation.1:1 This can be employed to determine the proper surgical approach. Paralytic strabismus will become increasingly comitant with the passage of time, and it is this "spread of comitance" that creates the various clinical types. The spread of comitance may be- Figure 7. Fundus drawing demonstrating range of normal of the foveal position with respect to the optic nerve head. Bixenman come app.uent within a matter of weeks, does not appear to depend on which eye is used for fixation, and does not preclude eventual recovery. I.) The most common presentation seen by ophthalmologists is with the hyperdeviation greatest in the field of action of antagonist inferior oblique,ll thJt is, up and in (Knapp Class I). The second most common is with the hyperdeviation equal in adduction (Knapp Class III), while the third is with the hyperdeviation greatest in the field of action of the paretic superior oblique, that is, down and in (Knapp Class II) (Fig. 8). Hence the reason that the red lens test cannot be relied on as the sole basis to "rule out" a superior oblique palsy. Knapp Classes IV (l-shaped deviation) and V ("double depressor paralysis") are quite uncommon, while Knapp Class VI (bilateral superior oblique palsies) is probably much more common than previously recognized (Figs. 3 and 9). "Masked" Bilateral Superior Oblique Palsies Bilateral superior oblique palsies may present clinically with a predominance of one-sided fea- E lOA E 8 A ET lOA RH 4 A ET 204 ET 254 ET 204 LH 6 4 RH 2A RH 104 ET 254 ET 354 ET 304 LH 8 4 RH 24 RH 13 6 Figure 9. Cardinal gaze position measurements of a case of traumatic bilateral superior oblique palsy. Note (i) the small left hyperdeviation in right gaze with a larger right hyperdeviation in left gaze, (ii) the V pattern with the esodeviation increasing on downgaze. RHT RHT RHT 7° 10° 22° RH(T) RHT RHT 5° 12° 19° RH RHT RHT 4° 10° 10° RH RH RHT 4° 4° 16° RH RHT RHT 1° 5° 13° RH RHT RHT 3° 5° 15° 0 RH(T) RHT 6° 10° RH RHT RHT 2° 9° 20° RH RHT RHT 4° 10° 22° Figure 8. Examples of right superior oblique palsies, demonstrating the most common clinical presentations. Left: most common presentation (Knapp Class I). Center: second most common presentation (Knapp Class III). Right: third most common presentation (Knapp Class II). September 1981 205 Superior Oblique Palsy tures, to the extent that one is occasionally confronted with "typical" unilateral superior oblique palsy with contralateral palsy only evident postoperatively after the first was treated! It has been stated that 16% of all unilateral superior oblique paralyses are in fact "masked" bilateral paralyses.'~ The following should arouse suspicion that a bilateral palsy in fact exists: (a) patients presenting with a chin depression; (b) over 13-150 of excyclotorsion on double Maddox rod testing in primary position; (c) bilateral underacting superior obliques on version testing (Fig. 3); (d) a V pattern strabismus (Figs. 3 and 9); (e) alternating hyperdeviations on lateral gaze of any amount (i.e., a R-HT on left gaze but a small L-HT on right gaze) (Fig. 9); (f) bilaterally positive head tilt tests (i.e., a R-HT on right head tilt and L-HT on left head tilt); (g) a superior oblique palsy of definite traumatic etiology. Cyclotropia without a Vertical Deviation This is a very uncommon presentation but one that every clinician should be aware of. These patients typically have had closed-head trauma, had transient diplopia which abated with time, have no vertical deviation when examined but have considerable excyclotorsion, especially in downgaze. 11 These patients appear to have a selective paralysis of the cyclotorsional function of the superior oblique muscle. The therapy is surgical. By recalling the different physiological functions of the anterior and posterior portions of the tendinous insertion of the superior oblique muscle, the clinician can predict which portion of the tendon should be tucked! Is the Superior Oblique Palsy of Recent Onset? Once the diagnosis of a superior oblique palsy is made, the clinician must decide whether it is a long-standing palsy or a palsy of recent onset. If recent, the patient should be referred for a neurological and medical workup. In addition, consideration for surgical management should be delayed for at least 6 months to allow for spontaneous recovery. The following will often help in making this distinction. Old Photographs These are very often the only proof that a torticollis is long-standing. Every patient should be urged to produce a family photo album. Patient History A long history of periaiIiC"henopia is certainly ~l!"."!,,.<;ti"e but not diagnostic: ,)f a long-standing 206 problem. Diplopia onsetting during the stress of a systemic illness or with the first pair of bifocals suggests a "decompensated congenital paresis." It is certainly helpful if the patient can provide a clear-cut history of problems brought on by a documental fall or auto accident many months or years previous. Vertical Fusional Amplitudes Supranormal vertical fusional amplitudes, a feature of long-standing or congenital superior oblique palsies, will not be found with a superior oblique palsy of recent onset. Unfortunately, not all long-standing palsies have such amplitudes. In this instance, if the angle can corrected with prisms and if some degree of fusional motor control can be measured from this orthophoric position, then the problem is likely of recent onset. 1l In longstanding cases, unless the deviation is quite small or supranormal fusional control has been achieved, all fusional vergences will wither away. State of Comitance In general, it is true that the very incomitant deviation is likely to be of recent onset while the more comitant the deviation, the older it is. As noted, there are exceptions to this rule as comitance may begin to appear within 3 weeks after onset. 13 Discrepancy between Results As noted, superior oblique palsies of recent onset typically demonstrate a good correlation between the severity of the symptoms, the degree of subjective excyclotorsion reported and the amount of objective excyclotorsion seen. In long-standing or congenital superior oblique palsies, there is often a discrepancy in the findings. The patient may have a torticollis and have objective excyclotorsion, yet be asymptomatic and note only 2_30 of excyclotorsion (and occasionally no excyclotorsion) on double Maddox rod testing. If any doubt exists, consider the superior oblique palsy to be of recent onset and follow the patient for 4-6 months to see if any improvement is forthcoming. Superior oblique palsies of definite traumatic origin are likely to be permanent, however.7 During this interval, there are a number of nonsurgical methods of treatment that may provide the patient symptomatic relief. In adults with acquired superior oblique palsy of unknown origin who present 6-9 months after onset, neurological and medical workups are generally unproductive.2 "Idiopathic" acquired superior oblique palsies are known to occur/' 4, 25 but the diagnosis must remain one of exclusion. How far to pursue each case remains the decision of the individual clinician. Journal of Clinical Neuro-ophthalmology Differential Diagnosis of Superior Oblique Palsy Because superior oblique palsies constitute over 90% of acquired vertical strabismus, there is seldom a problem with differential diagnoses. In the field of neuro-ophthalmology, the single exception remains skew deviation. Skew deviation, an acquired vertical strabismus due to supranuclear or vestibulo-ocular disruption, is a fascinating clinical entity and the reader is referred to standard neurological texts for a detailed review. The hypotropic eye is reported to be ipsilateral to the pathology in two-thirds of cases, Ili and other than indicating posterior fossa pathology, skew deviations have no consistent localizing value to a specific portion of the brain stem. Any acquired vertical strabismus in the context of brainstem disease should raise the possibility of a skew deviation. There is no consistent pattern to the hyperdeviation of skew deviations, which have varying degrees of comitancy and a variable torsional component. Any single cyclovertical muscle paresis may be mimicked at first glance. The first clue to the diagnosis is inconsistency in that the hyperdeviation does not follow a recognized pattern of a cyclovertical muscle palsy as one proceeds through the subjective tests step-by-step, the assessment of the ductions and versions, the measurements in the cardinal gaze positions and the three-step test, as previously outlined. Ophthalmologists in general tend to overlook the possibility of a skew deviation when working up a case of acquired vertical strabismus. Labels such as "atypical," "partial," or "incomplete" cyclovertical muscle palsies often appear in the literature and in charts. On the other hand, neurologists and neurosurgeons tend to overlook the possibility of a trochlear (fourth) nerve palsy, favoring the more "exotic" diagnosis of a skew deviation. This is especially true when a long-standing torticollis cannot be clearly established, when there is any degree of spread of comitance, when the patient fixates with the paretic eye and when the vertical diplopia is no longer maximal in the "expected" field of gaze for a superior oblique palsy with the red lens test (i.e., down and in). Often these patients are quite ill due to the underlying neurological disease process and it is difficult to do a detailed assessment. However, when a detailed examination is possible of patients previously labeled as having a skew deviation, more times than not one finds that the hyperdeviation clearly fits the pattern of a mild superior oblique muscle palsy. For the ophthalmologist, there are infrequent vertical strabismus cases which initially may be confused as a superior oblique palsy. This has September 1981 Bixenman recently been mentioned I? with unwarranted criticism leveled at the Bielschowsky head tilt test. The astute clinician recognizes that a diagnosis in medicine is never made by a single test, but rather on the basis of the clinical presentation as a whole. The same is true for superior oblique palsies. None of the aforementioned tests is diagnostic in itself. The clinician must interpret the test results in light of the overall presentation, and he must not indiscriminately rely on any single test to make or rule out the diagnosis. If there are inconsistencies, he must look for the unusual and employ other methods (e.g., forced duction testing, force generation testing, orbital x-rays, CT scans, etc.) to help make the proper diagnosis. Summary Adults with superior oblique palsy present with subjective asthenopic symptoms, often of long duration. Superior oblique palsies in children are usually diagnosed on the basis of objective clinical signs. Most cases have anomalous head posturing, which has often gone unnoticed by the patient. The double Maddox rod test and diplopia fields are the most useful subjective tests. Of the objective tests, the examination of the ductions and versions (preferably documented by external ocular photography), the three-step test of Parks, prism-cover testing in the diagnostic gaze positions, fundoscopic examination and occasionally vertical fusional amplitudes are the most useful. Sixteen percent of all unilateral superior oblique palsies may be "masked" bilateral palsies, and the examiner should be aware of the clues from the examination which might suggest this possibility. The patient with a cyclotropia but without a vertical deviation presents a challenge, not only for diagnosis but also for management. As in any case of paralytic strabismus, once the diagnosis is made, the clinician must decide whether or not it is a palsy of recent onset or of long duration. If it can be proved to be longstanding, the patient may be spared an unnecessary referral and neurological massage as well as an unnecessary 4- to 6-month wait for spontaneous recovery which will not be forthcoming. There is usually no problem with differential diagnoses when confronted with a patient with a superior oblique palsy. If the clinician takes the time to examine closely patients previously diagnosed as having "skew deviation," most will tum out to have mild trochlear nerve pareses. No single clinical test is pathognomonic of a superior oblique palsy. It is the clinical presentation as a whole that makes the diagnosis. Editorial Note: I quite agree with the primary thrust of this paper. However, I personally have found the red glass test quite helpful, and also the Lancaster red green 207 ~upenor Ubllque I'alsy test is useful-both in adults, primarily. Dr. Walsh demonstrated this to me years ago in a patient with diplopia that was difficult for me to interpret. He turned on the muscle light at the end of the room, put a red glass before the patient's right eye, and asked the patient to show how far apart the two lights were by simply putting his fingers in the same positions as the two lights. He then tilted the patient's head to the opposite shoulder, and when the patient showed a dramatic increase in the vertical deviation as evidenced by the separation of the patient's fingers, Dr. Walsh promptly told me this was a fourth nerve paresis! A reference on patients with superior oblique palsies presenting as isolated problems in neuro-ophthalmologic practice is: Acquired lesions of the fourth cranial nerve. Brain 93: 567, 1970. J.L.S. References 1. Bielschowky, A.: Lecture notes on motor anomalies, 1940. Cited in Young, B.R., and Satula, F.: Mayo Clin. Proc. 52: 11-18, 1977. 2. Ellis, FD., and Helveston E.M.: Superior oblique palsy: Diagnosis and classification. Int. Ophthalmol. Clin. 16(3): 127-135, 1976. 3. Harley RD.: Paralytic strabismus in children. Ophthalmology 87: 24-43, 1980. 4. Rush, J.A. and Younge B.R.: Paralysis of nerves III, IV and VI. Arch. Ophthalmol. 99: 76-79, 1981. 5. Guyton, D.L., and von Noorden, G.K.: Sensory adaptations to cyclodeviations. In Strabismus, RD. Reinecke, Ed. Grune & Stratton, New York, 1978, pp. 399-403. 2U8 6. von Noorden GK.: Clinical observations in cyclodeviations. Ophthalmology 86: 1451-1461, 1979. 7. Younge, B.R., and Satula, F.: Analysis of trochlear nerve palsies. Mayo Clin. Proc. 52: 11-18, 1977. 8. von Noorden, GK.: Atlas of Strabismus (3rd I'd.). C.V. Mosby, St. Louis, 1977, pp. 56-57. 9. Parks, M.M.: Isolated cyclovertical muscle palsy. Arch. Ophthalmol. 60: 1027-1035, 1958. 10. von Noorden, G.K.: Atlas of Strabismus (3rd I'd.). C.V. Mosby, St. Louis, 1977, pp. 146-155. 11. von Noorden, GK.: Superior oblique paralysis. Aust. f. Ophthalmol. 7: 45-50, 1979. 12. Bixenman, W.W., and von Noorden, GK.: Apparent foveal displacement in normal subjects and in eyclotropia. Presented at the 7th Annual AAP.O.s. Meeting, Orlando, Florida, May 7-10, 1981. 13. Knapp, P., and Moore, S.: Diagnosis and surgical options in superior oblique surgery. Int. Ophthalmol. Clin. 16(3): 137-149, 1976. 14. Hermann, J.5.: Masked bilateral superior oblique paresis. Presented at 6th Annual AA.P.o.S. Meeting, San Diego, California, April 2-5, 1980. 15. Nemet, P., Godel, V, Baruch, E., and Lazan, M.: Benign palsy of the superior oblique. Jr. Pediatr. Ophthalmol. Strab. 17: 320-322, 1980. 16. Keane J.R.: Ocular skew deviation. Arch. Neuro/. 32: 185-190,1975. 17. Kushner, B.].: Simulated superior oblique palsy. Ann. Ophthalmol. 13: 337-343, 1981. Write for reprints to: Wayne Bixenman, M.D., 1500 North Wilmot Road, Suite 130 a, Tucson, Arizona 85712. Journal of Clinical Neuro-ophthalrnology |
