Journal of Neuro-Ophthalmology, June 1991, Volume 11, Issue 2

Does pupillary sparing oculomotor nerve palsy really spare the pupil?

We examined the pupillary cycle time (PCT) in eight elderly patients with isolated oculomotor nerve palsy (ONP) that was characterized by complete involvement of the extraocular muscles. In addition to advanced age, all patients had at least one other vasculopathic risk factor. Although in all cases the pupil was completely spared by clinical impression, the PCT was significantly prolonged compared with the other eye and well outside the normal range (mean 1590 +/- 212 msec on the involved side and 1076 +/- 110 on the uninvolved side). On re-examination, after an interval of 2-3 months, the PCT was either normal or markedly improved in all patients, paralleling the recovery of extraocular muscle function. These findings suggest that even in pure, noncompressive ONPs there is subclinical pupillary involvement. Repeated PCT examinations may provide an objective means to estimate recovery. Moreover, in the problematic subgroup of ""pupil sparing"" incomplete ONP, PCT monitoring during the first days may indicate possible progression of a compressive lesion.

( J 1991 Raven Press, Ltd., New ' 1' 0'" _' ues Pupillary Sparing Oculomotor Nerve Palsy Really Spare the Pupil? Sergiu C. Blumen, M. D., Vera Feiler- Ofry, Amos D. Korczyn, M. D., M. Sc. We examined the pupillary cycle time ( PCT) in eight elderly patients with isolated oculomotor nerve palsy ( ONP) that was characterized by complete involvement of the extraocular muscles. In addition to advanced age, all patients had at least one other vasculopathic risk. fac · tor. Although in all cases the pupil was completely spared by clinical impression, the PCT was significantly prolonged compared with the other eye and well outside the normal range ( mean 1590 .:!: 212 mscc on the in­volved side and 1076 .:!: 110 on the uninvolved side). On re- examination, after an interval of 2- 3 months. the PeT was either normal or markedly improved in all patients, paralleling the recovery of extraocular muscle function. These findings suggest that even in pure, noncompres­sive ONPs there is subclinical pupillary involvement. Re~ ated peT examinations may provide an objective means to estimate recovery. Moreover, in the problem­atic subgroup of " pupil sparing" incomplete ONP, PeT monitoring during the first days may indicate possible progression of a compressive lesion. Key Words: Oculomotor nerve palsy- Pupil- Pupillary cycle time- Parasympathetic nervous system- Auto­nomic innervation. From the Department of Neurology ( s. c. a., A. D. K.) and Ophthalmology ( V. F- O.), Tel- Aviv Sourasky Medical Center, Sackler Faculty of Medicine, Tel- Aviv University, Israel. Address correspondence and rt'prinl re'lut'sts to Prof. AD Korczyn at Sadder Faculty " I' M~,(! icin('. Tel · Aviv University, Ramal Aviv [, 9978. I~ r" el, M. D., and The assessment of pupillary involvement is cru­cial in the evaluation of patients presenting with oculomotor nerve palsy ( ONP). Patients with nerve compression, particularly due to posterior communicating artery aneurysms, are likely to have nonreacting--- or at least sluggish- pupils ( 1­3). On the other hand, when the GNP is due to ischemia, the pupils are rarely involved ( 4,5). The reason for the pupillary sparing is unknown, but it is speculated to be due to the more peripheral 10­cation of the parasympathetic fibers in the oculo­motor nerve ( 6). On the rare occasions in which compressive le­sions produce pupil- sparing ONP, these are usu­ally incomplete ( 3,7,8). As opposed to noncom­pressive lesions, these may progress over several days to produce the complete paralysis with pu­pillary involvement ( 7). Unfortunately, the bedside evaluation of pupil­lary reaction to light depends on clinical impres­sions and is qualitative rather than quantitative. In an attempt to evaluate whether a more sensitive, quantitative test will disclose some pupillary in­volvement in patients with ischemic ONP, we have utilized the edge- light pupil cycle time ( PCl) ( 9) in the evaluation of ONP. SUBJECTS AND METHODS Eight patients ( 6 men) with ONP were studied. They had acute onset of complete paralysis of all the muscles innervated by the oculomotor nerve, but an apparently normal pupillary reaction to light and accommodation. The clinical details, shown in Table 1, demonstrate that patients were of advanced age and had other vasculopathic risk factors. The remainder of the neurological and ophthalmological examination was also noncoo. tributory, although patients with diabetes mellitus 92 PCT IN OCULOMOTOR NERVE PALSY 93 TABLE 1. Pupillary cycle time ( peT) in eight patients with " pupil sparing" oculomotor nerve palsy 1st Examination 2nd Examination Abnormal Normal Abnormal Normal Age/ sex Risk factors side side side side E. O. M. 69/ M OM 1533 1000 1200 1000 improved 60/ F OM, HT, lHO 1733 1133 1133 1133 recovered 73/ F HT 1666 1266 1300 1266 recovered 74/ M OM 1266 966 966 966 recovered 74/ M OM, IHO 1933 1133 1200 1133 recovered 781M OM, HT 1533 966 1000 966 recovered 811M OM 1966 1066 1066 1066 recovered 771M OM 1733 1066 1066 1066 recovered Eight pts, mean: 1670 : t 212 1074.:!: 110 1116.:!: 120 1074: tll0 Values are given in milliseconds, mean : t SO. E. O. M" extraocular movements; OM, diabetes mellitus: HT, arterial hypertension: IHO, ischemic heart disease. had impaired vibration sense and no Achilles ten­don reflexes. In each case, the peT was measured bilaterally within 48 hours after the onset of GNP and was repeated 2- 3 months later. Pupillary cycle time was measured using a Haag- Streit slit lamp ( Berne, Switzerland), with a horizontal beam of light ( thickness, 0.5 mm) di­rected at the lower margin of the pupil ( 9,10). Three cycle rounds lasting 30 sec each were pro­duced in each eye, and the average peT was cal­culated by dividing the 90- sec time period by the total number of cycles elicited. Statistical evalua­tion was performed using Student's t test for paired samples, comparing the two eyes on the first examination, or the abnormal eye on the two tests. RESULTS When first examined, all patients had complete GNP with apparent nomnvolvement of the pupil. However, the peT was prolonged on the ophthal­moplegic side in each case ( Table l). The difference between the paretic and the uninvolved eye ranged from 300 to 900 msec and was statistically highly significant ( p < 0.01). At the time of the second exarrunation, all pa­tients showed Significant or complete improve­ment of their extraocular movements. The peT showed recovery or improvement ( Fig. 1). DISCUSSION The peT is an established method for the rapid, quantitative, accurate evaluation of function of the optic and pupillomotor pathways ( 9- 11). The slightly prolonged latencies on the clinically unin­volved side in our patients is consistent with their advanced age ( 11,12). In addition, 7 out of 8 sub­jects had underlying diabetes mellitus, which also prolongs the peT. The clinical presentation and eventual recovery suggest that in all of our patients ONP was due to ischemia; their age and vasculopathic risk factors are consistent with this diagnosis. All patients un­derwent brain computerized tomography which did not reveal any structural abnormality that could explain the patients' ophthalmoplegia. Our findings dearly demonstrate that in all eight cases there was subclinical involvement of the parasym­pathetic component of the oculomotor nerve. Exceptions to the " rule of the pupil" ( 7) are well known; as many as 25% of patients with ischerruc GNP may have clinical evidence of pupil involve­ment. The present results suggest that subclinical involvement is even more common. In some cases, in whom the rule of the pupil is not obeyed ( 3,7,8), repeated measurements of the peT may be helpful in establishing the diagnosis. For example, in an incomplete ONP, the progres­sive prolongation of the PCT may indicate an un­derlying compressive lesion and thus suggest the need for performing angiography. In others, grad- 2000 1800 u ell 1600 < II e - 1400 ~ Il.:. l. I 1200 1000 800 +- 7.":-==~~;;-::-~=-:-;--;:-::-------:---- Normal Rbnormfll Rbnormfll First Second FIG. 1. Pupillary cycle time in patients with " pupil sparing" third nerve palsy. , ( lin Neuro- ephlhalmol, Vol. 11, No, 2, 1991 94 S. C. BLUMEN ET AL. ual improvement of PCT may herald recovery of the ONP, and thus suggest a benign etiology. REFERENCES l. Rucker CW. 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