Ocular pulse amplitude measured by PASCAL dynamic contour tonometry in patients with a cavernous sinus dural arteriovenous fistula

Abstract

Editor, Cavernous sinus (CS) dural arteriovenous fistula (CSDAVF) is an abnormal connection between the CS and the extradural branches of the internal and external carotid artery. A possible increase in the ocular pulse amplitude (OPA), the difference between the systolic and diastolic intraocular pressure (IOP)s, has been reported in cases with a CSDAVF with the OPA measured by Schiötz tonometer, pneumotonometer or ocular pneumoplethysmography (Birch-Hischfeld 1930; Gee et al. 1983; Golnik & Miller 1992). PASCAL dynamic contour tonometer (DCT; Ziemer, Port, Switzerland), a novel nonapplanation contact tonometer, records systolic and diastolic IOP simultaneously, allowing an easy and noninvasive determination of OPA. Previously, the increase in the OPA was determined in only one case of a CSDAVF using an earlier model of DCT (Kaufmann et al. 2004). We report three cases of a CSDAVF in which the OPA was measured using a current model of DCT before and after surgery. From the observations, we found that effect of ipsilateral CSDAVF can affect contralateral orbital venous system, and clinical findings can be noted as changes in DCT-measured OPA. A 69-year-old woman (Case 1) was referred to Shimane University hospital for a 3-week history of ocular redness and proptosis in the left eye (OS) and binocular diplopia. Her best-corrected visual acuity (BCVA) was 1.0 bilaterally. Using DCT, the IOP values were 19.1 and 26.3 mmHg in the right (OD) and OS, respectively, and the OPAs were 3.2 mmHg OD and 9.3 mmHg OS. Magnetic resonance imaging (MRI) showed dilation of the left superior ophthalmic vein (SOV) (Fig. 1A). Cerebral angiography (CAG) showed a left CSDAVF, blood reflux to the left SOV and occlusions of the left superior and inferior petrosal sinuses (PSs) (Fig. 1B). Ten days after the diagnosis, the patient underwent transvenous embolization (TVE) for a left CSDAVF because of the gradual deterioration of diplopia. Postoperative CAG showed closure of CSDAVF shunt (Fig. 1C). The sustained preoperative IOP increase in the left eye normalized after TVE (Fig. 1D). Interestingly, before TVE, a gradual decrease in the OPA OS was accompanied by a gradual increase in the OPA OD despite symptom deterioration during this period. The symptoms resolved promptly after TVE, which was accompanied by normalization of the OPAs bilaterally (Fig. 1E). (A) Presurgical magnetic resonance imaging (MRI) of case 1. Compared to opposite side, dilation of the superior ocular vein is seen on the left side (arrow). (B) Presurgical Cerebral angiography (CAG) of case 1. Blood reflux to the left cavernous sinus (CS) is seen (arrow). (C) Postsurgical CAG of case 1. The shunt was occluded by the coil embolization (arrow). (D) Changes in the IOP in case 1. (E) Changes in the ocular pulse amplitude in case 1. (F) Presurgical MRI of case 2. Dilation of the superior ocular vein is seen on the right side (arrow). (G) Presurgical MRA of case 2.A Cavernous sinus dural arteriovenous fistula (CSDAVF) is seen on the left side (arrow). (H) Presurgical CAG of case 2. Blood reflux to the right CS from the left CSDAVF through the intercavernous sinus is seen (arrow). A 76-year-old woman (Case 2) was referred to our hospital for a 6-month history of ocular redness and proptosis OD and binocular diplopia. Her BCVA was 1.0 bilaterally. The IOP was 24.8 mmHg OD and 17.4 mmHg OS, and the OPAs were 5.5 mmHg OD and 1.6 mmHg OS. MRI showed dilation of the right SOV (Fig. 1F); however, MRA showed formation of a left CSDAVF (Fig. 1G). CAG showed a left CSDAVF, occluded left superior and inferior PSs and a left SOV, and blood reflux to the right SOV through the intercavernous sinus (ICS) (Fig. 1H). Her symptoms remained after transarterial embolization for the left CSDAVF; the IOP and OPA OD were 27.8 mmHg and 5.4 mmHg, respectively, 2 weeks postoperatively. Postoperative CAG showed a residual left CSDAVF and blood reflux to the right SOV through the ICS. An 84-year-old woman (Case 3) was referred to our hospital for a 1-month history of ocular redness, ptosis, and severe proptosis OS and limited ocular movement bilaterally. Her BCVA was 0.2 bilaterally. Her IOP was 14.8 mmHg OD and 17.7 mmHg OS, and the OPAs were 2.4 mmHg OD and 5.6 mmHg OS. CAG showed blood flow to the right and left CS from the shunt point at the ICS and blood reflux to both SOVs. The OPAs decreased to 1.5 mmHg OD and 1.4 mmHg OS at 1 week after the TVE for a shunt point at the ICS, and her symptoms resolved at 3 weeks. Using pneumotonometry, Golnik & Miller (1992) reported that a difference in the OPAs between both eyes (ΔOPA) of more than 1.6 mmHg was 100% sensitive and 93% specific for identifying patients with a CSDAVF and a direct cavernous carotid fistula. Using DCT, the median OPA and ΔOPA were reported to be 3.0 mmHg and virtually 0 mmHg, respectively, in normal eyes (Kaufmann et al. 2006). In the current report, the ΔOPAs were 6.1, 3.9 and 3.2 mmHg for cases 1, 2 and 3, respectively, at the initial tonometry session, with all cases exceeding the cut-off of 1.6 mmHg determined by Golnik and Miller, although the suitability of this cut-off value has not been tested in DCT. In cases with a CSDAVF, intrasinus thrombi and thickening of the sinus wall caused by abnormal arteriovenous flow could occlude the existing venous drainage routes. In case 2 with a relatively longstanding left CSDAVF was accompanied by blood reflux to the opposite SOV through the ICS. Accordingly, gradual development of an ICS channel toward the contralateral CS because of a continuous hemostatic pressure increase in the ipsilateral CS of the fistula, which is augmented by subsequent occlusion of physiologic drainage routes of CS, may explain the gradual decrease in OPA OS and reciprocal increase of the OPA OD after the initial tonometry session in case 1. In addition, drainage of the postcanalitic venous system, i.e. the episcleral veins, and the choroidal venous system, i.e. the vortex veins, the status of which mostly reflect the IOP and OPA (Bynke & Schéle 1967), respectively, into the SOV could be affected to varying degrees in each subject. Thus, the discrepancy in the kinetics between the preoperative IOP and OPA in case 1 may be explained by the difference in blood reflux between the postcanalitic and choroidal venous systems. Accordingly, the OPA may be an independent indicator from the IOP for assessing the hemodynamic status of CSDAVFs.