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ORIGINAL ARTICLE
Year : 2013  |  Volume : 61  |  Issue : 4  |  Page : 406-410

Spinal dural arterio-venous fistula: Clinico-radiological profile and outcome following surgical occlusion in an Indian neurosurgical center


1 Department of Neurosurgery, All India Institute of Medical Sciences, New Delhi, India
2 Department of Neuroradiology, All India Institute of Medical Sciences, New Delhi, India

Date of Submission07-May-2013
Date of Decision12-Jun-2013
Date of Acceptance21-Jul-2013
Date of Web Publication4-Sep-2013

Correspondence Address:
Aditya Gupta
Department of Neurosurgery, AIIMS, New Delhi
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.117616

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 » Abstract 

Background: Spinal dural arteriovenous fistula (SDAVF) is a common type of spinal vascular lesion. However, there has not been any published study on its clinico-radiological characteristics or surgical outcome from India. Aim: The aim of this study was to determine the clinico-radiological features of patients with SDAVF, outcomes following surgical ligation of the fistula and the various factors involved. Materials and Methods: Patients who were operated for SDAVF were studied for demographic details, symptoms, clinical severity, radiological features and neurological outcome in the form of improvement in gait disability grades. Appropriate statistical tests were performed. Results: There were 22 (19 males, 3 females) patients of SDAVF who underwent surgical ligation with a mean age of 55 years. The mean duration of symptoms at presentation was 15 months. Three patients had acute onset while the rest had insidious onset of symptoms. Out of the 22 patients, 11 (50%) had motor weakness as the first symptom, 13 (59%) were bedridden and 19 (86.4%) had bladder involvement at presentation. Thirteen patients had fistulae in thoracic spine, whereas eight had fistulae in the lumbar spine. All had a favorable outcome in the form of at least non-progression of gait disability (14 had improvement while 8 had stabilized). The improvement was non-significantly associated with younger age, acute onset, ambulant status and fistula below T9. It was inversely associated with pain as the first symptom and fluctuant clinical course. Conclusion: Surgical occlusion of SDAVF is usually associated with either improvement or stabilization of motor weakness.


Keywords: Gait disability, improvement, spinal dural arteriovenous fistula, surgical ligation


How to cite this article:
Dhandapani S, Gupta A, Singh J, Sharma B S, Mahapatra A K, Mehta V S. Spinal dural arterio-venous fistula: Clinico-radiological profile and outcome following surgical occlusion in an Indian neurosurgical center. Neurol India 2013;61:406-10

How to cite this URL:
Dhandapani S, Gupta A, Singh J, Sharma B S, Mahapatra A K, Mehta V S. Spinal dural arterio-venous fistula: Clinico-radiological profile and outcome following surgical occlusion in an Indian neurosurgical center. Neurol India [serial online] 2013 [cited 2018 Nov 20];61:406-10. Available from: http://www.neurologyindia.com/text.asp?2013/61/4/406/117616



 » Introduction Top


Spinal dural arteriovenous fistula (SDAVF) is frequently encountered accounting for around 70% of spinal vascular lesions. [1],[2] It is a network of acquired low-flow abnormal arteriovenous (AV) shunts in the dura covering spinal nerve roots, usually supplied by dural branch of a radicular artery and drained by the perimedullary venous system through a radicular vein. [2] Despite being a treatable cause of myelopathy, they are often underdiagnosed because of the non-specific nature of the clinical presentation and lack of awareness of the clinical condition among the practicing physicians. [3] Though first recognized in the late 19 th century, with advances in magnetic resonance imaging (MRI), superselective spinal angiography, microsurgical techniques and endovascular therapy, presently these lesions are potentially treatable. [3],[4] Even though embolization is increasingly being performed in these lesions, surgical disconnection of SDAVFs is still a treatment option with high success rates. [5],[6] However, there has not been any published study on the clinico-radiological characteristics or surgical outcome in patients with SDAVF from India.


 » Materials and Methods Top


The medical records of patients with SDAVF operated at the Department of Neurosurgery, All India Institute of Medical Sciences, New Delhi, between 1991 and 2005 were reviewed. The treatment modality was chosen after detailed discussions between neurosurgeons and interventional neuroradiologists, considering general physical condition, feasibility of embolization, affordability and patients' preference. Surgical occlusion was the only option in the presence of common origin of medullary artery and radiculomeningeal feeders due to the potential high risk of vascular insult to the cord with embolization and whenever the feeders were too small to be cannulated. Surgery was performed by laminectomy or hemi-laminectomy confined to the level of fistula based either on marker X-ray or image intensifier, followed by limited dural opening. The fistula was identified by tracing arterialized veins into nerve root sleeve, followed by coagulation and severance of arterialized vein. Patients were followed-up with the spinal digital subtraction angiography (DSA) if no improvement was noted.

Patients were studied for age at diagnosis, gender, first symptom, symptom onset, progression, history of subarachnoid hemorrhage, exacerbation of neurologic symptoms by physical activity, neurologic deficits, Aminoff-Logue scale (ALS) [7] and MRI findings. The angiographic studies were reviewed for the spinal level, number of feeding vessels and venous drainage. Patients were also studied for improvement in the gait disability following surgery and also for residual fistula in repeat check DSA. Patients were analyzed for demographic data, clinical and radiological features and neurological outcome in the form of improvement in gait disability grades.

Statistical analysis was performed using the SPSS 20 software (IBM Corp. New York). Proportions were compared by using the Chi-square test or Fisher's exact test whenever appropriate. Two sided significance tests were used throughout and the significance level was kept at P = 0.05.


 » Results Top


There were a total of 22 patients (19 males and 3 females) with SDAVF who underwent surgical ligation. The ages ranged from 30 to 75 years (mean age 55). Out of the 22 patients, 10 patients were in the sixth decade.

The duration of symptoms at presentation ranged from 3 to 24 months (mean duration 15 months). Three patients had acute onset while the rest had insidious onset of symptoms. Of the 22 patients, 11 (50%) patients had motor weakness as the first symptom while nine had pain and one each had numbness and urinary complaints as the first symptom. Three patients presented with remitting and relapsing symptoms and the rest had progressive symptoms. Overall 13 (59%) patients were bedridden (ALS grade 5) and 19 (86.4%) patients had bladder involvement at presentation. The summary of clinical profile is given in [Table 1].
Table 1: Clinical profile

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All patients had T2 cord hyper-intensity and subarachnoid flow voids in MRI [Figure 1]. Spinal DSA revealed SDAVF at thoracic level in 13 patients [Figure 2]a and in eight patients it was at lumbar location. Venous drainage was predominantly rostral in 18 patients. Of the 22 patients, 16 patients had the fistula on the right side. The radiologic profile is as shown in [Table 2].
Figure 1: T1 and T2 weighted sagittal images showing cord signal changes with dorsal subarachnoid flow voids

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Figure 2: (a) Spinal digital subtraction angiography (DSA) showing spinal dural arteriovenous fistula (SDAVF) at D10 level on the left. Same feeder gives rise to SDAVF and radiculo‑medullary artery (contraindicated for embolization). (b) Post‑operative check spinal DSA showing no fistula

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Table 2: Radiologic profile

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The mean follow-up period was 7 months. Outcome was assessed with respect to change in ALS gait disability grade. Overall all patients had favorable outcome in the form of at least non-progression. The 14 patients had improvement in gait disability grade; eight patients had stabilization of neurologic deficits. No one had worsening in the deficits. Of these patients, three patients had residual fistula [Figure 2]b necessitating re-surgery. The subgroup analysis under different categories is as shown in [Table 3]. The improvement was non-significantly greater in patients less than 50 years of age, those with acute onset of symptoms, ambulant at presentation and fistula below T9. There was lesser improvement in patients with pain as the first symptom and fluctuating clinical course with the periods of remission [Table 3]. Residual fistula needing re-surgery was noted in two patient of the three patients with intermittent symptoms, compared with one of the 19 patients with progressive symptoms (P = 0.04).
Table 3: Improvement across various subgroups

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 » Discussion Top


SDAVFs are the most frequently encountered spinal vascular lesions and one of the treatable causes of progressive myelopathy. [1],[2] The reported incidence is 5-10 cases/million people annually. [2] SDAVFs are acquired low-flow fistulae between dural branch of a radicular artery and a radicular vein along the inner dural sleeve of the dorsal spinal root at the intervertebral foramen. [2],[3] The pathologic AV shunt leads to arterialization of the valveless perimedullary venous plexus with resultant reduction in AV gradient and retrograde venous drainage. The resultant venous hypertension decreases spinal cord perfusion and leads to ischemia and edema, resulting in progressive myelopathy and sometimes, in the spinal cord infarction. [1],[2],[3] The natural history is one of progressive myelopathy, with 50% of untreated patients likely to be severely disabled at 3 years. [7]

Although, this condition was recognized as early as 1888 by Guapp and later noticed during surgery by Krause in 1911 [8] and excised first by Elsberg in 1916, [2] it was Foix and Alajouanine who first described the clinical entity of subacute myelopathy due to thrombosis of pathologic spinal cord vessels in 1926. [9] Di Chiro et al. proposed the most commonly accepted scheme of classifying them as Type I lesions in 1967. [10] It was Aminoff and Logue who were credited with the first large clinical series of patients with SDAVFs in 1974 with its pathophysiology of venous hypertension and proposal of the widely accepted disability scale. [7],[11] The classification and terminology of SDAVFs was further modified by Spetzler et al. in 2002 to dorsal intradural AV fistula, in contrast to the high flow (perimedullary) ventral intradural AV fistula. [12] It was also sub-classified into dorsal Type A with single feeding artery and dorsal Type B with multiple feeders. [12]

The most patients in our series were in the sixth decade with men affected 6 times more, these observation are similar to other studies. [2],[4],[5] The long delay of 15 months between the onset of initial symptom and the diagnosis of SDAVF in our study corroborates with a mean delay of 19-24 months in other series, [4],[5] with the resultant delay in definitive treatment. This is likely because of the nonspecific nature of clinical presentation, which may mimic more common entities such as degenerative spine disease, amyotrophic lateral sclerosis, transverse myelitis or peripheral vascular disease.

Acute onset myelopathy in the form of Foix-Alajouanine syndrome was noted in three patients (14%) in our series, much higher than 2-5% reported in the literature. [5],[13] The presenting symptom was motor weakness in 50% of our patients similar to other series. [2],[6],[14] Back or radicular pain was the presenting symptom in 41% in our study, higher than the 21% reported by others. [6],[14] Though urinary complaints were the presenting symptom in only 5%, it was noted at the time of diagnosis in 86% of patients similar to other studies. [2],[3],[6],[14] Fluctuant clinical course with periods of remission were noted in 14% as compared with 26% noted in other studies. [13] Of the 22 patients, all patients had a weakness at diagnosis and 13 (59%) were wheel-chair bound, which is much higher than 10-32% reported in other series. [2],[3],[5],[13],[15] The fistula was located between T9 and L5 in 73% of patients compared to 58% reported. [5],[ 6],[16]

Improvement in gait disability was noted in 64% and stabilization in 36% in our patients following surgery. Saladino et al. had 82% improvement and 14% stabilization in their series. [5] In the meta-analysis by Steinmetz et al., of the 16 surgical studies, clinical improvement ranged between 25% and 100%, with the pooled long-term surgical outcome favorable in almost 9 out of 10 patients, with clinical improvement in 55% and stabilization of the clinical condition in 34%. Re-surgery was needed in 14% compared to 5-17% in the literature. [5],[6]

While improvement was non-significantly greater in patients who are younger and those with acute onset and was lesser in patients with pain as the presenting symptom. However no prognostic factor was statistically significant, probably due to the small number of patients in our series. While Nagata et al. had noted significant impact of age on outcome, [17] this has not been replicated in many other studies and there is general agreement that patients should not be excluded from treatment solely based on advanced age. [16],[18] Early diagnosis had a better outcome in a study by Niimi et al., but not in most others. [19],[20],[21],[22] This may in part be explained by the variable progression of irreversible neurological injury, which occurs acutely in a minority of patients. Although few authors have demonstrated a correlation between severity of preoperative disability and lack of improvement after surgery, [20],[21] we were unable to demonstrate the same association. There was greater improvement in patients with lower thoracic and lumbar fistula, compared to those with mid-thoracic fistula, similar to the findings of Cenzato et al. [21] This may be due to the better vascularization of the lower thoracic cord than that of the upper thoracic cord. [21]

Complete and permanent fistula obliteration provides the best chance for symptomatic improvement and a favorable outcome. Previously endovascular treatment had lower initial success rates varying between 30% and 90%, depending upon penetration of the proximal vein. Recurrence had been reported to be as high as 23% in studies without occlusion of the proximal vein. [19],[23],[24],[25] Embolization became more effective with the embolic material successfully occluding proximal part of the draining vein. [3],[19] Song et al. in 2001 had noted gait improvement in 44% while 56% remained unchanged and none worsened after embolization. [24] A meta-analysis of 10 heterogeneous endovascular studies noted embolization to have 46% long-term effectiveness in achieving shunt occlusion with morbidity of lesser than 4% and no mortality. [16] In one of the largest series to report both endovascular and surgical treatments, Narvid et al. found no statistical difference in ALS scores between the two groups, with both groups showing a significant improvement in gait with intervention (65% vs. 50% respectively). These indicate that if a SDAVF is adequately treated with either surgery or embolization, the outcomes are probably similar.

Though minor invasiveness and higher comfort of endovascular treatment in the same setting as diagnostic angiography may appear advantageous in centers with technical expertise, factors such as severe arteriosclerosis, small arterial feeders, arterial dissection due to catheter manipulation and common origin of the anterior spinal artery from the same segmental artery as the feeding artery of the fistula make embolization feasible only in about three-quarters of patients. [26] In addition, the expense involved may not permit embolization in the large section of economically challenged patients from developing countries. However microsurgical ligation is a simple, straightforward, quick, economical, definitive and effective option with minimal morbidity.

 
 » References Top

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    Figures

  [Figure 1], [Figure 2]
 
 
    Tables

  [Table 1], [Table 2], [Table 3]

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