Author(s): Ramon Go, Joshua Lantos, and Jeffrey Ngeow
Here we present a case of a 77-year-old man who underwent an epidural steroid injection complicated by delayed monoplegia and urinary incontinence. An MRI showed T2 hyperintensity at the conus along with small serpentine vessels surrounding the spinal cord. An angiogram was performed which showed a spinal dural arteriovenous fistula (SDAVF) with prominent draining vein at the right L3 level. The patient underwent repeat laminectomy and disconnection of spinal dural fistula after failed endovascular repair. His symptoms slowly improved after the lumbar decompression and physical therapy. SDAVF remains a diagnostic challenge. Epidural injection is contraindicated in these patients due to venous hypertension resulting in possible conus ischemia. SDAVF must be considered in the differential diagnosis when unexpected neurological complications occur after epidural steroid injection.
Spinal dural arteriovenous fistula (SDAVF) is a rare malformation resulting in abnormal connections between arterial and venous networks in the spinal column. Although rare, SDAVF comprises 60 to 80% of spinal vascular malformations [1]. The etiology of these lesions are unclear although they appear more likely to form in older male patients. In SDAVF, an abnormal connection is present between radicular artery and medullary vein, resulting in the arterialization of perimedullary veins. Diagnosis remains challenging as MRI findings may be subtle. Congestive myelopathy occurs resulting in progressive weakness which may be acutely exacerbated with injection into the epidural space [2, 3]. Here we present a case of delayed monoplegia after a right sided transforaminal epidural steroid injection (TFESI) in a patient with an undiagnosed SDAVF. A literature review on this diagnostically challenging pathology is also provided.
A 77 year-old 79 kg man with a history of degenerative spondylosis status post decompression of the lumbar spine at the L3 and L4 levels one year prior presented to the pain clinic for recurrent radiating right leg pain following the right L4 dermatome. MRI of the lumbar spine with contrast performed 3 months after lumbar decompression showed degenerative disc and hypertrophic osteophyte at L4/5 and L5/S1 level. The patient underwent a right L4-L5 TFESI under fluoroscopic guidance with a mixture containing 80 mg of triamcinolone and 0.25% bupivacaine injected. The patient tolerated the procedure and after one hour, the patient was discharged with no procedural complications.
About 12 hours later, the patient reported weakness in the right lower extremity which progressively worsened. The patient also reported inability to control bowel movements and urinary retention. This progressed to complete paralysis of the right lower extremity a few hours later. An MRI with contrast was obtained showing hyperintensity at the conus along with small serpentine vessels surrounding the spinal cord seen in sagittal but not axial views (Figure 1). The patient was immediately admitted to the Neuro ICU, but about 10 hours upon symptom onset, the patient?s paralysis began to improve. A few hours later the patient was able to walk with assistance and able to void. After careful history taking, the patient endorsed history of voiding difficulty over the past month. A spinal angiogram showed a dural arteriovenous fistula with prominent draining vein at the right L3 level and was supplied primarily by the L2 lumbar radicular arteries through collateral flow, since the L3 radicular lumbar arteries were found to be occluded at their aortic origin level (Figure 2). The patient underwent repeat laminectomy and disconnection of SDAVF under microscope after failed endovascular embolization of the vessels. Multiple dilated vessels were noted on the surface of the nerve roots during the surgical procedure. A large arterialized vessel entering through the right L3 root sleeve and going into the canal heading towards the conus was identified. This was dissected free of its surrounding and transected. Immediately after transection, the dilated vessels on the surface of the nerve rootlets were noted to decrease significantly in caliber. The patient was discharged two days after surgical procedure to rehabilitation. Three months postprocedure, the patient continued to improvement in neurological symptoms.
Figure 1: A) T2-weighted MRI axial image of the lumbar spine showing hyperintensity (blue arrow). B) Flow void pattern on sagittal image is seen along the L2 vertebral body.
Figure 2: A spinal angiography showing a dural arteriovenous fistula with prominent draining vein at the right L3 level.
Epidural steroid injection remains a mainstay treatment for lumbar radiculopathy. Complications from epidural steroid injection are rare, but catastrophic outcomes have been reported when ESI is performed in patients with SDAVF. Fortunately, recovery is possible with appropriate treatment. Epidural steroid injection is contraindicated in patients with SDAVF but diagnosis is often missed. Paralysis from ESI in patients with undiagnosed SDAVF has been described by several case reports (Table 1).
Table 1: Published cases of epidural steroid injection in patients with SDAVF. Ten out of eleven patients with SDAVF experienced neurological complications after ESI
| Report | Intervention | Injectate mixture at each site | Total volume injected (mL) | Procedure Outcome | Onset of symptoms post-injection | SDAVF Treatment and outcome |
|---|---|---|---|---|---|---|
| Kim et al Case 1 (2016) | TFESI (bilateral) L5 and S1 | Dexamethasone (1.25mg), lidocaine, bupivacaine, normal saline | 20 | CES, bilateral lower extremity paraplegia | 8 hours | Endovascular embolization; incomplete recovery |
| Kim et al Case 2 (2016) | Caudal ESI | Dexamethasone (unknown dose) | Not described | CES, bilateral lower extremity paraplegia | Not reported | Endovascular embolization; incomplete recovery |
| Kim et al Case 3 (2016) | Right L5-S1 TFESI | Dexamethasone (10mg), ropivacaine, normal saline | 3 | Pain relief, no weakness | N/A | N/A |
| Annaswamy & Worchel (2016) | Left L2-L3 Interlaminar ESI | Betamethasone (12mg), bupivacaine | 6 | CES, bilateral lower extremity paraplegia | 4 hours | Endovascular embolization; incomplete recovery |
| Sharma & Sharma (2016) | L2-L3 Interlaminar ESI | Betamethasone (12mg), bupivacaine | 4 | CES | 4 hours | Endovascular embolization; incomplete recovery |
| Oliver et al (2012) | L5-S1 Interlaminar ESI | Not described | Not described | CES, bilateral lower extremity paraplegia | 3 hours | Endovascular embolization; near complete recovery |
| Owen et al Case 1 (2011) | L4-L5 ESI | Triamcinalone (80mg), 8ml lidocaine | Not described | Temporary CES, monoplegia | 12 hours | Surgery; recovery not described |
| Owen et al Case 2 (2011) | L4-L5 ESI | Triamcinalone (80mg), 7ml lidocaine | Not described | bilateral lower extremity paraplegia | 24 hours | Endovascular embolization; incomplete recovery |
| Hetts et al Case 1 (2006) | L2-L3 ESI | 12 mL ropivacaine 0.2%, 2 mL methylprednisolone 80 mg/mL | 14 | CES, Progressive paraparesis, | 7 hours | Surgery; incomplete recovery |
| Hetts et al Case 2 (2006) | Lumbar ESI | Not described | Not described | CES, complete paralysis | ~24 hours | Surgery after failed endovascular embolization; partial recovery |
| Hetts et al Case 3 (2006) | Lumbar ESI | Not described | Not described | CES, Bilateral lower extremity paraparesis | ~24 hours | Endovascular embolization; partial recovery |
Iatrogenic formation of arteriovenous fistula after lumbar microdiscectomy or other spine surgeries have been described in the literature [4, 5]. Our patient could tolerate epidural steroid injections prior to his initial laminectomy, suggesting that SDAVF may have formed as a complication of the surgery. Review of the initial lumbar laminectomy operative note did not reveal any report of abnormal vasculature, although this does not exclude its pre-existence
Diagnosis of SDAVF is challenging as symptoms are non-specific, MRI findings are often subtle, and spondylopathy is often a comorbidity [6, 7]. Paraparesis has been found to be the most common initial presenting symptom in patients with SDAVF but variability exists in the severity of this symptom [7]. The presence of flow voids in the subarachnoid space is a feature seen on MRI but is not specific to SDAVF. Flow voids may be seen in spinal dural arteriovenous malformations or epidural arteriovenous fistula. Cord edema may also be seen on MRI as a result of venous congestion [8]. In a study of 40 patients with known SDAVF, 34 of the patients showed cord signal changes. Nevertheless, mean time to diagnosis has been found to be one year with about 18% of patients misdiagnosed. Angiography is the gold standard for diagnosis [7].
The normal epidural space can tolerate injection of volume as the pressure is zero or slightly negative, however in the setting of SDAVF, venous hypertension occurs resulting in further compressive ischemia of the spinal cord [9]. Diagnosis is often challenging as symptoms often are similar to lumbar radiculopathy, lumbar stenosis, polyneuropathy, demyelinating disease, and intramedullary tumor. Injection of solution into the epidural space may acutely worsen venous congestion causing spinal cord or nerve root impingement resulting in cauda equina syndrome (CES). Paraplegia after epidural steroid injection have been reported in caudal, interlaminar, and transforaminal approaches to the epidural space [10-15]. Therefore, caution dictates that epidural steroid injection should not be performed in patients with SDAVF due to the significant risk of paraplegia [10]. Injection of a small volume may result in significantly elevated hypertension in the epidural space with as little as 4 mL of volume causing cauda equina syndrome. Reported cases of ESI in patients with SDAVF demonstrates that the onset of symptoms is variable (Table 1). Systemic steroid administration alone has shown to cause aggravation of SDAVF symptoms potentially due to water retention and engorgement of the SDAVF [16, 17]. This may also explain the variable time in the onset of symptoms in patients receiving ESI. Concomitant injection of local anesthetic which have arterial vasodilatory properties may also explain the variability of symptom onset [18].
Endovascular transarterial embolization of SDAVF is often technically challenging with success ranging from 25-75% [7, 8]. Although more invasive, surgical repair reaches 100% successful treatment. A meta-analysis performed by Steinmetz et al shows 98% success rate and 1.9% complication rate for surgical repair [19]. A minimally invasive approach using tubular retractor has been suggested but needs further studies [20]. The utility of a lumbar drain in the setting of acute exacerbation of SDAVF induced myelopathy has been demonstrated and should be considered [13]. Effective treatment of the venous congestion caused by SDAVF has been shown to arrest or reverse the changes caused by myelopathy, therefore efficient diagnosis and treatment is recommended.
Spinal dural arteriovenous fistula is a rare condition with potentially devastating consequences if unrecognized. Unfortunately, SDAVF remains a diagnostic challenge due to multiple factors. Epidural injection of steroids is contraindicated with this pathology. Any unexplained neurological complications from epidural injection should alert one to include SDAVF in the differential diagnosis. Interventional pain specialists should be aware of SDAVF and pursue further evaluation including neurological consult as well as angiography should MRI suggest the presence of this pathology.
