Abstract
BACKGROUND
Foix-Alajouanine syndrome (FAS) is a subacute, progressive spinal cord disorder that usually shows abnormalities on spinal cord MRI. Here, the authors report a case of FAS that showed no abnormalities on MRI and was treated.
OBSERVATIONS
A 64-year-old woman presented with progressive spinal cord damage in both lower limbs. Repeated hospitalizations for neurological examinations revealed no obvious abnormalities. MRI showed no obvious abnormalities, but angiography suggested a ventral arteriovenous fistula (AVF) in the thoracic spinal cord. A microcatheter confirmed the diagnosis of perimedullary AVF, and shunt occlusion was performed using a combination of a microscope and an oblique endoscope. After surgery, symptoms were mildly alleviated and progression was halted.
LESSONS
In patients with progressive FAS, spinal vascular disease should be investigated even if MRI findings are normal. In addition, combined endoscopic surgery is a promising tool for treating perimedullary AVFs in the ventral thoracic spinal cord.
Keywords: case report, Foix-Alajouanine syndrome, spinal perimedullary arteriovenous fistula, slowly progressive myelopathy, endoscope-assisted microsurgery, micro-spinal angiography
ABBREVIATIONS: ASA = anterior spinal artery, AVF = arteriovenous fistula, AVS = arteriovenous shunt, FAS = Foix-Alajouanine syndrome
Foix-Alajouanine syndrome (FAS) refers to progressive spinal cord damage and has been reported to involve lesions of unknown etiology without pathological evidence of thrombosis or hemorrhage. With the development of diagnostic equipment and spinal angiography, there are now increasing reports of spinal arteriovenous malformations and arteriovenous fistulas (AVFs).1 Therefore, it is important to recognize that FAS is a progressive necrotizing vascular spinal cord disorder.2
Here, we report a case in which spinal angiography was proactively performed in a patient with progressively worsening myelopathy, known as MRI occult myelopathy, whose cause was unknown even after MRI and other tests, leading to the diagnosis of an arteriovenous shunt (AVS).
Illustrative Case
The 64-year-old woman in this case had a past medical history of hypertension and surgery for trigeminal neuralgia. A few years earlier, she began to experience numbness in both legs and frequent urination, which gradually led to difficulty walking, leading to her referral to our clinic. Before visiting our hospital, the cause of her symptoms was unknown even after consultations with several neurologists. Neurological examination revealed hypoesthesia and numbness below L1, hyperreflexia in both lower limbs, and a negative Beevor’s sign. Mild bladder and rectal dysfunction were also observed, leading to a diagnosis of thoracic myelopathy. Spinal MRI showed no obvious abnormalities (Fig. 1A). No conservative treatment was effective, and due to the progressive nature of the disease, a dorsal spinal angiogram was planned. Right T10 intercostal artery imaging showed the artery of Adamkiewicz, the absence of an arterial basket in the conus medullaris, and abnormal enhancement of the vein of the filum terminale more caudally (Fig. 1B). Ventral perimedullary AVS was suspected, and selective spinal angiography using a microcatheter was performed later. After carefully inserting the microcatheter into the AVS area and performing angiography, a direct shunt from the anterior spinal artery (ASA) to the anterior spinal vein was observed, and reflux into the left radiculomedullary vein (T12) and vein of the filum terminale was confirmed (Fig. 1C). Similar findings were observed on the lateral view (Fig. 1D). Based on the above test results, the diagnosis was perimedullary AVS in the ventral region of T10–-11. Direct surgery was planned to prevent progression of the myelopathy.
FIG. 1.
A: Spinal MR image showing no obvious findings. B: Selective spinal angiogram revealing contrast enhancement from the left T10 intercostal artery to the artery of Adamkiewicz (white arrows). No conus basket was observed (double arrowheads), and mild flexion of the ASA was observed at the T11 level (yellow arrow). C: Microcatheter image (anteroposterior view; double asterisks) revealing an AVS at the T10–11 level (yellow arrow), the T12 radiculomedullary vein (single arrowhead), and the vein of the filum terminale (double arrowheads) beyond the conus tip. D: Microcatheter image (lateral view; double asterisks) demonstrating an AVS at the T10–11 level (yellow arrow) and the vein of the filum terminale (double arrowheads) beyond the conus tip (single asterisk).
To diagnose a ventral perimedullary AVF, we determined that it would be impossible to reach the lesion using only a microscope. Therefore, we devised a strategy to observe the ASA in the blind spot using an endoscope (45° oblique endoscope, Karl Storz). We prepared a UniARM system (Mitaka) to fix the endoscope.
Under general anesthesia, the patient was placed in the prone position, and an arcuate incision was made in the left T10–11 pedicle, marked with a C-arm (Fig. 2A). Partial hemilaminectomy and facetectomy of T10–11 were performed via an intermuscular approach, and the T10 root sleeve was exposed (Fig. 2B). The dura mater was incised and exposed, and the craniocaudal dentate ligament on the lateral side of the spinal cord was dissected. The inside of the dura mater was observed using a 45° endoscope, and the spinal cord was fixed with a UniARM (Fig. 2C). An endoscopic image of the left ventral side of the spinal cord is shown (Fig. 2D). When observing the ventral side of the spinal cord, the ASA was found, and a red vein was observed to the left side, leading to a diagnosis of a direct shunt (Fig. 2E). A vascular clip was inserted under a microscope (Fig. 2F), and the direct shunt site was identified with the aid of an endoscope (Fig. 2G). Then, clipping was performed under electrophysiological monitoring (Fig. 2H). Postoperative 3D-CT angiography showed AVF occlusion (Fig. 3A). After the surgery, the patient was transferred to another hospital for rehabilitation without any problems, and the progression of myelopathy stopped.
FIG. 2.
A: An arcuate incision was made from the left T10 pedicle to the T11 pedicle. B: A lateral laminectomy of T10–11 and a facetectomy of T10–11 were performed between the muscles to expose the dura mater and T10 nerve root (asterisk). C: The dura mater was incised and opened, and the inside of the dura mater was observed using a 45° endoscope fixed to a UniARM. D: Lateral view of the spinal cord from the left lateral side, confirming the posterior median septum (double asterisks). E: When the ventral side was unfolded, the ASA (white arrows) was found to be descended, and an abnormal red vein was observed, identifying the AVS point (yellow arrow). F: Endoscopic clipping was attempted. G: The AVS site (yellow arrow) was carefully dissected. H: The AVS was blocked with endoscopic assistance.
FIG. 3.
A: Postoperative 3D-CT angiogram showing that AVS clipping was performed, preserving the ASA up to the conus tip. B: Schematic of the surgical approach to the ventral thoracic AVF. DL = dentate ligament; Endo = endoscope; Exo = Exoscope; F = facet; Micro = microscope; P = pedicle; R = rib.
Informed Consent
The necessary informed consent was obtained in this study.
Discussion
Observations
Pathophysiology of FAS
FAS is a grouping of rare, progressive spinal arteriovenous malformations causing significant neurological morbility. A systematic review of 46 FAS cases showed that the mean age was 55 years, the incidence was higher among men, and all cases had progressive thoracic and lumbar spinal cord disorders.3 Imaging studies showed spinal cord hyperintensity in 82.1% of MRI studies and dural AVF in 70% of spinal cord angiography studies.3 Conservative treatment did not result in improvement, but surgical and/or endovascular treatment resulted in improvement in 58.7% of the 46 patients; 28.2% worsened or died, making this a far from benign disease.3 Meta-analysis of FAS indicates the need for early detection and early surgical intervention. In addition, FAS is easily mistaken for neurological disorders such as transverse myelotis in the early stages of the disease, and many cases are referred only after the disease has progressed. Even if MRI does not show spinal congestion, FAS should be suspected in cases of progressive paraplegia of unknown cause, and spinal angiography should be performed.4
Surgical Approach of Thoracic Ventral Spinal Cord
There is much debate about the surgical method for ventral thoracic spinal cord lesions, and methods such as adding unilateral pedicle and facet resection, and resection of the upper and lower dentate ligaments, followed by spinal cord retraction, have been reported.5 Furthermore, Angevine et al. successfully performed surgery on significant ventral lesions by rotating the spinal cord.6 However, spinal rotation has its limitations, and Acosta et al. reported a more ventral approach using transpedicular vertebrectomy from the outside.7 Giese et al. reported a successful case of a posterior transmedullary approach to a ventral perimedullary AVF at the T10 level.8 However, we believe that this should not be done in all cases. Recent improvements in endoscope imaging and intraoperative indocyanine green videoangiography have made it possible to treat vascular lesions on the ventral side of the spinal cord.9 This case report is the first to report endoscope-assisted surgery using an oblique endoscope for ventral AVS.
Figure 3B shows a schematic of the current surgical approach to ventral thoracic spinal cord lesions.
Lessons
In cases in which FAS is suspected, angiography should be performed proactively even if MRI findings are not abnormal. Lesions on the ventral side of the thoracic spinal cord are difficult to approach, but treatment is possible with the combined use of endoscopy.
Acknowledgments
We express our gratitude to the case patient and support staff of our institution.
Disclosures
Dr. Kiyosue reported grants from Phillips outside the submitted work.
Author Contributions
Conception and design: Uchikado, Ohkubo. Acquisition of data: Uchikado, Ohkubo, Kiyosue. Analysis and interpretation of data: Uchikado, Ohkubo, Morioka. Drafting the article: Uchikado, Ohkubo. Critically revising the article: Uchikado, Ohkubo. Reviewed submitted version of manuscript: Uchikado, Ohkubo, Takashima, Kiyosue, Nagase. Approved the final version of the manuscript on behalf of all authors: Uchikado. Statistical analysis: Uchikado, Ohkubo. Administrative/technical/material support: Uchikado, Ohkubo. Study supervision: Uchikado, Ohkubo, Nakamura, Morioka.
Correspondence
Hisaaki Uchikado: Uchikado NeuroSpine Clinic, Hakata, Fukuoka, Japan. uchikado@me.com.
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