Spinal dural arteriovenous fistula (SDAVF), a rare disease presentation in a young adult

Clinical History

A 25-year-old man presented with complaint of progressively worsening upper backache for 2 years and recent onset of progressive paraparesis and bladder dysfunction.

Imaging Findings

MRI dorsal and lumbosacral spine with T1 and T2 weighted axial and sagittal sequences were obtained.
MRI findings were cord enlargement in the lower thoracic region and conus with diffuse multilevel intramedullary abnormal signal intensity area extending from T7 to L1 vertebral levels in craniocaudal extant. It appears low on T1 and high on T2 weighted images representing cord oedema / myelomalacia (Fig. 1, 2)
Abnormal vessels appearing as multiple innumerable flow voids are seen in the thoracic spinal cord on the dorsal aspect in perimedullary location, representing spinal dural arterovenous malformation (Fig. 1)
The likelihood of a diagnosis of spinal dural arterovenous malformation was aided by DSA and angioembolization, followed by some improvement in patient’s paraparesis with persistent bladder dysfunction.

Discussion

Spinal dural arteriovenous fistulas (SDAVFs) are the most frequent vascular malformation of the spine and account for approximately 70% of all vascular spinal malformations [1, 2]. In a SDAVF, typically one (but sometimes multiple) feeding radiculomedullary artery enters the dura mater of the spinal cord at the dural root sleeve and forms a fistula with a medullary vein, thus arterializing the corona venous plexus surrounding the spinal cord. The resistance to venous outflow results in chronic venous hypertension/ stagnation leading to chronic medullary ischaemia [3]. Most fistulas are solitary lesions and are found in the thoracolumbar region, 80% in between T6-L2 level, 4% in sacral [4] and 2% in high cervical location (at the level of the foramen magnum) [5], while low cervical SDAVFs (below C2 and above T1) are extremely rare [6, 7].
SDAVFs become symptomatic in elderly men, mean age at the time of diagnosis is 55–60 years. Men are affected 5 times more often than women. Patients younger than 30 years of age constituted less than 1% of patients with a SDAVF, whereas, to our knowledge, no patient younger than 20 years of age has ever been reported [8]. Usually patients present with nonspecific symptoms of venous congestion like difficulty in climbing stairs, gait disturbances, patchy paraesthesia and backache. Bowel and bladder incontinence, erectile dysfunction, and urinary retention are more often seen late in the course of the disease.
The diagnosis of SDAVF is made on MR imaging, is guided by MR angiography (MRA) and is confirmed by DSA [9]. On T1-weighted images, the swollen cord is slightly hypointense and enlarged. On T2-weighted sequences, the cord oedema is depicted as a multilevel centromedullary hyperintensity. The second finding on the T2-weighted images is flow voids, which are often more pronounced on the dorsal surface compared with the ventral surface. The noninvasive evaluation of the shunt location is extremely helpful to guide the invasive conventional angiography [10].The aim of the treatment in SDAVF is to occlude the shunting zone (i.e., the most distal part of the artery together with the most proximal part of the draining vein. [11, 12]. There are two options in the treatment of SDAVFs, either surgical occlusion or endovascular therapy.
As SDAVF has a better outcome when diagnosed earlier in the disease course, it should be considered in the differential diagnosis of selected patients, such as older patients (particularly men) with progressive myelopathy. High clinical suspicion for SDAVF when neuroimaging is ambiguous should prompt angiography to avoid delay in this treatable condition.

Differential Diagnosis List

Final Diagnosis

Spinal dural arterovenous fistula

URL:	https://eurorad.org/case/12331
DOI:	10.1594/EURORAD/CASE.12331
ISSN:	1563-4086