Gamma knife radiosurgery for primary orbital varices: a preliminary report
- 1Gamma Knife Center, Department of Neurosurgery, Tianjin Medical University Second Hospital, Tianjin, PR China
- 2Gamma Knife Center, Department of Ophthalmology, Tianjin Medical University Second Hospital, Tianjin, PR China
- Correspondence to Professor Dong Liu, Gamma Knife Center, Department of Neurosurgery, Tianjin Medical University Second Hospital, 23# Pingjiang Road, Hexi District, Tianjin, PR China, 300211;
- Accepted 25 September 2010
- Published Online First 22 October 2010
Aim The aim of this retrospective study is to evaluate the authors' experience using gamma knife radiosurgery in the management of primary orbital varices.
Methods Fourteen patients, six males and eight females, with ages ranging from 7 to 56 years of age, were treated with gamma knife radiosurgery from April 2001 to June 2005 for primary orbital varices. The median prescription peripheral dose was 16 Gy, ranging from 15 to 20 Gy, and the median maximum dose was 32 Gy, ranging from 30 to 40 Gy. The median volume of the lesion at radiosurgery was 4.5 ml (range 1.9 ml to 9.0 ml). The mean dose to optic nerve was below 10 Gy. A mean of 10 isocentres (range 8 to 13) were used for treating these lesions.
Results At a median follow-up period of 36 months (range 18 to 66 months), recurrent exophthalmos and diplopia resolved in 10 patients. Two of the remaining four patients showed evidence of decrease in distensibility, while the other two remain unchanged. The median time of their presenting symptoms resolving was 7 months (range 3 to 18 months). One patient lost her sight 18 months after gamma knife radiosurgery. No patient had intraorbital haemorrhage after treatment.
Conclusion Gamma knife radiosurgery provides effective long-term relief of symptoms in selected patients with primary orbital varices.
Primary orbital varices (POVs) are infrequent congenital venous malformations composed of venous channels of abnormal calibre and distribution as either a single vessel with segmental outpouchings or multiple tangled venous channels. Clinical presentation of the affected patients is typical with intermittent positional exophthalmos, which could occur by increasing venous pressure through jugular vein compression, Valsalva manoeuvre, coughing or placing the head in a dependent position.1 2 As a common cause of retrobulbar haemorrhage, POVs can cause severe visual function impairment because of optic nerve atrophy.
Conventional management involves observation, local pharmacotherapy and microsurgery, which sometimes cause vision loss.3 Recently, ophthalmologists and patients seem to prefer less invasive treatments.4 We performed a review of 14 patients with POVs from our institution to assess the results following gamma knife radiosurgery (GKRS).
Materials and methods
Between April 2001 and June 2005, 14 patients with POVs underwent GKRS at our centre. When our project began, there was no previous radiosurgical experience with POVs to which we could refer. Patients were referred to us after first being seen by an ophthalmologist, who could make the clinical diagnosis according to their typical ophthalmological and radiographic findings, or prior treatment history. The last detailed eye examination before GKRS was available on all patients. Visual acuity was measured in each patient using a standard logarithmic visual acuity chart. Seven of the affected eyes had a visual acuity of 1.0 or better, three eyes had a visual acuity of 0.6∼ 1.0, and four eyes had a visual acuity below 0.5. All patients may have presented with intermittent proptosis as they dilated secondarily to valsalva-induced increased venous pressure.
GKRS was performed as the initial treatment in 10 patients, and as the adjunctive treatment after prior resection in four patients. All of the patients underwent an axial MRI/CT scan. During the image scanning, the position of 10 patients was supine with the head in a dependent position, and that of four patients was prone with neck hyperextension. Patients were followed with serial imaging (MRI/CT at 6-month intervals) when possible, and with periodic clinical examination. Quality-assurance telephone interviews were used to assess clinical response to GKRS (table 1).
Gamma knife radiosurgery
Stereotactic radiosurgery was performed using the Leksell Gamma Knife unit (model B; Elekta Instruments AB, Stockholm, Sweden). After administration of local anaesthesia (a mixture of xylocaine and normal saline), the stereotactic head frame was applied, and imaging was performed on the day of GKRS. Children under the age of 10 years had GKRS under general anaesthesia. Stereotactic MR images were obtained with the head in a neutral position. The position of 10 patients was supine, and that of other patients was prone. The digitised images were then transferred to the Leksell GammaPlan (Elekta, Stockholm) workstation for use in dose planning. After target delineation by the neurosurgeon and ophthalmologist, the physicist placed some isocentres as needed to create isodose contours conforming to each target using GammaPlan planning software. The GKRS prescription dose was chosen at the discretion of the treating physicians. The prescribed peripheral dose to 50% isodose line varied from 15 to 20 Gy (median 16 Gy); the corresponding central dose was between 30 and 40 Gy (median 32 Gy). The dose plans were created with high conformality and selectivity, especially at the margin adjacent to optic nerve, by optimising the weight, position and plug pattern of each shot with small collimators. The intraorbital portion of the optic nerve had received a mean dose of less than 10 Gy. We tried to limit the maximum point dose of optic nerve to no more than 12 Gy, and the volume receiving 12 Gy to less than 5% of the intraorbital portion of optic nerve. The median volume of the lesion pre-GKRS was 4.5 ml (range 1.9–9.0 ml). A median of 10 isocentres (range 8–13) were used for treating these lesions.
Statistical analysis was performed using commercially available statistical software (SPSS, version 10.0).
Patients underwent a follow-up examination at 6-month intervals for the first 2 years after GKRS and then every 1–2 years thereafter. At a median follow-up period of 36 months (range 18 to 66 months), intermittent positional exophthalmos and diplopia resolved in 10 patients reviewed in this study. Two of the remaining four patients showed evidence of a decrease in distensibility, while the other two remain unchanged. The median time of their presenting symptoms resolving was 7 months (range 3 to 18 months). Thirteen patients had stable visual acuity after GKRS (table 2).
Except for reversible conjunctival oedema in two cases, no other serious acute side effect was observed. Within the median follow-up of 36 months, only one 7-year-old girl suffered form deterioration of visual function at 18 months post-GKRS because of amotio retina. No patient had an intraorbital haemorrhage after GKRS.
Radiological treatment response
Following MRI or CT in 10 (71.4%) patients, there was no evidence of orbital varices, which was generally observed 6 to 18 months after GKRS (figure 1). For these patients, we usually suggested that an MRI/CT be performed after jugular vein compression or lying prone on the bed to ensure the embolisation of the POVs. No further recurrance was identified 1 to 6 years after GKRS.
Orbital varices are vascular hamartoma typified by a plexus of low pressure, low flow, thin-walled and distensible vessels that intermingle with the normal orbital vessels.3As orbital and jugular veins do not have valves, systemic venous pressure changes occur during coughing, forced expiration, bending forward or the Valsalva manoeuvre, or jugular vein compression may lead to variable engorgement of varices. Orbital haemorrhage or thrombosis may cause acute, painful proptosis, sometimes with decreased orbital motility.3 5 Although the visual prognosis for orbital varix is relatively good, visual function impairment is severe if there is a rupture or thrombosis because of optic nerve atrophy.
Rootman and Graeb3 have stated that spontaneous haemorrhages may occur in all types of orbital venous anomalies but are more common in non-distensible anomalies, and none of the distensible orbital anomalies had any episodes of orbital haemorrhage or thrombosis. However, Wright et al6 found no statistically significant difference between the frequencies of haemorrhages between lesions with a positive Valsalva test and those without. On the other hand, the distension of orbital varix results in an intermittent increase in intraorbital pressure and may result in atrophy of the surrounding orbital fat.7
Most POVs patients will try to remit intermittent proptosis by avoiding jugular vein compression, coughing or placing the head in a dependent position. Observation is usually warranted for small POVs, but surgical intervention may be necessary in advanced cases. Surgery can be extremely difficult, as POVs are very friable and intimately intermixed with normal orbital structures. Conventional treatment sometimes fail, and a progressive optic neuropathy develops. A new effective method of treatment is needed for such cases.
Stereotactic radiosurgery for POVs has been carried out, since similar vascular anomalies such as AVM have shown excellent results. In the majority of cases presented herein, embolisation of the varices can be marked as early as 6 months after GKRS. However, for the patients with rapid aggravation leading to visual deterioration, indications for GKRS include progressive symptomatic POVs, recurrent/residual POVs after prior surgical resection and patients with contraindications to surgery. Evaluation by an ophthalmologist and neurosurgeon is strongly recommended prior to referral to the Gamma Knife Center.
The distensibility of POVs is determined by the size of functioning connections to the venous system.3 Lesions with large connections respond to venous pressure changes, are readily distensible and evidence distensibility both clinically (intermittent exophthalmos) and radiologically. Therefore, it is very important to keep the patient's head in the same position during the course of GKRS, especially when performing stereotactic MRI/CT and gamma knife treatment. For patients whose orbital varices cannot be visualised on MRI/CT in a supine position, requiring them to lie in a prone position may solve the problem, but there should be a fixed delay before starting an MRI scan and GKRS so that the POVs may distend sufficiently.
The prescribed dose for intraorbital disease should be chosen according to the dose-volume effect, pathology, location of intraorbital disease with eyeball and optic nerve, visual acuity and its radiosensitivity.4 In MRI/CT studies, the morphology of POVs manifests as a triangular configuration tapering towards the apex and the convex anterior margin. Since POV is that of a venous malformation with abnormal uni- and bilateral dilation of one or more orbital veins, 15–20 Gy at the margin of the lesion seems enough. In this study, we found that GKRS provided a dramatic achievement in POVs control. The median prescription peripheral dose was 16 Gy (range 15 to 20 Gy). In 10 patients, recurrent exophthalmos and diplopia resolved. The median time of their presenting symptoms resolving was 7 months.
POVs are contiguous to the intraorbital portion of optic nerve. For those with good visual acuity on the affected side, it is important to consider how to control the POVs as well as to avoid the severe optical pathway neuropathy. Leber et al8 retrospectively analysed optic nerve toxicity after GKRS in 50 patients with various types of tumours. They reported an optic neuropathy actuarial incidence of 0, 26.7% and 77.8%, in patients who received radiation doses of less than 10 Gy, 10–15 Gy and more than 15 Gy, respectively, to the optic pathways. Mayo et al9 found that the risk of toxicity increased markedly at doses >60 Gy at 1.8 Gy/fraction and at >12 Gy for single-fraction radiosurgery. Multisession GKS may be an effective and safe alternative for treatment in POVs that are unsuitable for single-session radiosurgery. In our series, only one patient suffered from loss of sight 18 months later because of amotio retina.
Acute reactions rarely occurred in the patients with orbital region who adopted gamma knife radiosurgery treatment, which generally happened in 24 h after treatment. Acute reactions always included headache, orbital pain and nausea, and sometimes vomitting. Such symptoms resolve in a short time without special treatment. No patient in our study developed a delayed, radiation-associated malignant tumour.
Stereotactic gamma knife radiosurgery provides effective long-term relief of symptoms in selected patients with primary orbital varices.
We thank L Zheng, Y Li, X Liu and Q Jia, for their assistance with this project.
DX and DL contributed equally to the work and should be considered equivalent first authors.
Competing interests None.
Patient consent Obtained.
Provenance and peer review Not commissioned; externally peer reviewed.