3.3 | Early diagnosis procedure for SDAVF
The reason for the delayed diagnosis of SDAVF is that it is easily
misdiagnosed as another disease. Spinal degenerative diseases and
myelitis are particularly common misdiagnoses.
The initial symptoms of SDAVF are nonspecific motor and sensory deficits
in the lower extremities. Symptoms worsen with walking and improve with
rest. These symptoms are similar to those of intermittent cauda equina
claudication caused by lumbar spinal stenosis, which is a common
disease. The first investigation is often a lumbar MRI scan. If spinal
stenosis is suggested, it may be misdiagnosed as the cause. To avoid
this misdiagnosis, it is important to consider whether the symptoms can
actually be explained by lumbar spinal stenosis and to check for
abnormal conus medullaris signals on lumbar spine MRI.
SDAVF is worsened not only by walking but also by singing, the Valsalva
maneuver, and alcohol consumption 1, 3. Additionally,
it is crucial to remain vigilant for symptoms that may be challenging to
account for due to lumbar spinal lesions, such as weakness in the
iliopsoas muscle, sensory disturbances extending beyond the groin, and
the presence of the Babinski sign. Furthermore, SDAVF should be
considered if symptoms are slowly worsening. Attention should be paid to
the presence or absence of abnormalities in the thoracolumbar junction
(intramedullary high signal intensity, abnormal vascular images in the
subarachnoid space) on lumbar spine MRI.
SDAVF is easily misdiagnosed as myelitis because long intramedullary
hyperintensities are observed on T2-weighted images. When a long
intramedullary hyperintensity is observed, one should be aware of the
abnormal vascular image in the subarachnoid space that is characteristic
of SDAVF. The course of SDAVF is often progress slowly; however, it can
worsen rapidly with exercise. SDAVF is often misdiagnosed as myelitis,
which has an acute onset 13. SDAVF often has a mild
increase in the number of cells in the cerebrospinal fluid. The
administration of steroids has been documented to lead to sudden
clinical deterioration in individuals with SDAVF. When encountering a
patient with myelitis whose symptoms worsen with steroid administration,
SDAVF must be differentiated 7, 14.
SDAVF is suspected based on clinical and spinal MRI findings. Next,
minimally invasive 3D CT angiography or contrast-enhanced MRA is used to
detect abnormal blood vessels. Subsequently, selective spinal
angiography is employed to establish a conclusive diagnosis of SDAVF.