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Ovid: Fifty Neurologic Cases from Mayo Clinic

Editors: Noseworthy, John H. Title: Fifty Neurologic Cases from Mayo Clinic, 1st Edition Copyright ©2004 Oxford Unversity Press (Copyright 2004 by Mayo Foundation for Medical Education and Research) > Table of Contents > Case 8: “Spaghetti legs,” numb feet, and constipation Case 8: “Spaghetti legs,” numb feet, and constipation CASE 8 History A 59-year-old man presented with a 6-year history of progressive leg weakness. He needed to interrupt his exercise to sit because his legs felt “like spaghetti.” A neurologist diagnosed chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). He received 46 plasmaexchange treatments with apparent partial benefit. However, his condition worsened. Subsequently, he received a brief course of intravenous immunoglobulin and long-term treatment with prednisone in combination with several immunosuppressive drugs, including cyclophosphamide, azathioprine, mycophenolate mofetil, and tacrolimus. Despite treatment, his condition worsened, and he recently noted numbness in the soles of his feet, bladder hesitancy, constipation, and impotence. Examination The patient required a cane to ambulate, and he was unable to walk on heels or toes. Neurologic examination demonstrated moderate weakness of ankle dorsiflexors and plantar flexors and mild distal sensory loss affecting light touch, joint position, and vibration sense in the feet and impairment of pin sensation over the feet and sacral area. Deep tendon reflexes were absent in the lower extremities. Muscle strength and sensation were normal in the upper extremities. Investigations Hematologic and biochemical tests, the erythrocyte sedimentation rate, and tests for vitamin B12, human immunodeficiency virus, Lyme disease, monoclonal proteins, hepatitis, and human T-cell leukemia viruses I/II were normal. Electromyography (EMG) showed chronic, severe mid-thoracic through sacral radiculopathies on the right without evidence of diffuse polyradiculoneuropathy. Cerebrospinal fluid analysis demonstrated only an elevated protein level (twice normal) and one oligoclonal band. Spinal magnetic resonance imaging (MRI) showed diffuse thickening and enhancement of the lumbosacral nerve roots and a thickened conus medullaris. The results of sural nerve and muscle biopsies and spinal angiography performed elsewhere were unrevealing. Repeat spinal MRI demonstrated enlargement with enhancement of the caudal 4 cm of the spinal cord and conus medullaris, with slight contrast enhancement in the cauda equina. P.30
DIAGNOSIS CASE 8 Spinal dural arteriovenous fistula (SDAVF)
Commentary by Drs. Guillermo A. Suarez and William E. Krauss Spinal cord and nerve root biopsy specimens showed changes consistent with a vascular malformation. A second spinal angiographic study was performed, and at a second operation, a right T7 SDAVF was obliterated. SDAVF is a rare and treatable cause of myelopathy. The patient presented here had suggestive, evolving MRI findings with abnormal T2-signal changes involving the lower thoracic spinal cord and conus medullaris (Figure). However, abnormal vasculature was not seen on several studies and was documented with certainty only during a second spinal angiographic study and with spinal cord biopsy. These findings underscore the difficulty in making the diagnosis of SDAVF and the importance of including SDAVFs in the differential diagnosis of myelopathy and lower motor neuron syndromes, particularly those involving the lower thoracic spinal cord and conus medullaris. Several atypical features led to reconsideration of the original referring diagnosis of CIDP. These included 1) predominant involvement of the lower extremities, 2) electrodiagnostic features showing a thoracolumbar polyradiculopathy without multifocal conduction slowing, conduction block, or temporal dispersion, 3) abnormal MRI findings, with enlargement and enhancement of the caudal thoracic spinal cord and conus medullaris, and 4) lack of definite improvement after prolonged treatment with several immunomodulatory agents. SDAVF typically presents in the early 60s and has a male predominance. Diagnosis is often delayed. Patients describe lower extremity weakness, leg fatigue, and lower extremity or perineal numbness or burning pain as the initial manifestations. Symptoms are asymmetric in up to one-half of patients. Leg weakness (sometimes with low back pain) while maintaining an erect posture or exercise intolerance is seen in many patients. Symptoms worsen with standing and improve with rest. Upper extremities are involved in only a small proportion of cases (e.g., SDAVFs at the foramen magnum or petrous ridge). Symptoms of sphincter dysfunction are usually a late manifestation. In order of frequency, the following initial symptoms predominate: lower extremity weakness, lower extremity fatigue, and lower extremity or perineal numbness (or both). Upper and lower motor neuron signs are found in 70% of patients and lower motor neuron signs alone occur in about 30%. Symptoms progress slowly or with stepwise worsening until the P.31
diagnosis and treatment are established. Occasional subacute exacerbations have been described. EMG localizes the abnormality to the spinal nerve roots or anterior horn cells and excludes other conditions. EMG findings may be entirely normal in the early stages of the disease or show segmental nerve root (polyradiculopathy) or anterior horn cell involvement, especially in the thoracolumbar region. Neuroimaging of the spinal cord with MRI or computed tomographic (CT) myelography demonstrates intramedullary T2-signal abnormalities, especially in the lower thoracic spinal cord and conus medullaris, associated with abnormal dorsal vessels. CT myelography with prone and supine images reveals dilated vessels on the dorsal surface of the spinal cord. SDAVFs are confirmed and localized by spinal angiography. MRI of the entire spinal cord is the initial diagnostic method of choice because it is noninvasive and allows visualization of the spinal cord and adjacent structures, with high definition. Spinal magnetic resonance angiography can sometimes localize the fistula, directing and streamlining subsequent angiography. The fistula results from an abnormal connection between a dural artery and a radiculomedullary vein in the dura mater near a nerve root, usually in the thoracolumbar region. The suspected pathogenesis involves venous hypertension leading to neuronal and central nervous system damage. The cause of SDAVFs is unknown, but they are thought to be acquired. Currently, there are two treatments. Endovascular embolization of acrylic material has a good success rate in experienced centers but is associated with a higher complication rate, a higher rate of treatment failure, and a higher recurrence rate than microsurgical obliteration. We favor surgical intradural disconnection of the fistula because the procedure directly reverses the pathophysiologic mechanism by isolating and disconnecting the proximal draining vein of the SDAVF. In experienced hands, surgery has very low failure and complication rates. P.32

FIGURE. A, T1-weighted sagittal image with contrast showing enlargement and abnormal enhancement of the distal thoracic spinal cord and conus medullaris (thick arrow). Thin arrow, Dilated vessels on posterior surface of the spinal cord. B, Spinal angiogram demonstrating a dural arteriovenous fistula at T7 on the right.

REFERENCE Atkinson JLD, Miller GM, Krauss WE, et al. Clinical and radiographic features of dural arteriovenous fistula, a treatable cause of myelopathy. Mayo Clin Proc 2001;76:1120-30.

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