Improvement of Brown-Sequard syndrome after surgical repair of an idiopathic thoracic spinal cord herniation

Abstract

Sirs: Idiopathic spinal cord herniation (ISCH) through an anterior or anterior-lateral dural defect is a rare cause for progressive myelopathy, but has become more recognized during recent years with the routine use of MRI. Nevertheless in most cases the patients present with a long lasting history of a progressive Brown-Sequard syndrome. In the following we describe our experience with the case of an ISCH, the clinical and radiological signs and the surgical therapy via dorsal foraminotomy. A 50-year-old man presented with a four year history of a slowly progressing loss of temperature and pain sensation in the sense of a Brown-Sequard syndrome in the right side of the body beginning at dermatome T 2/3 down to the level of T 5/6. For two years he had developed a more rapid progressive spastic paresis of the left leg. There were no vegetative symptoms or pain. He had no history of spinal trauma or other relevant diseases. MRI showed herniation of the spinal cord through the left ventrolateral dura at the level of T 2/3 with adherence to the dorsal spinal ligament (Fig. 1a, b). The somatosensory evoked responses showed a lesion of the dorsal column. Surgery was performed via dorsal foraminotomy at the level T 2/3. After opening of the dura numerous adhesions were removed, the spinal cord was carefully replaced into the dural sleeve and the dural defect was closed with a patch of two Gore-Tex strips from the intradural side. From the extradural side the patch was strengthened with a collagen fleece. The postoperative magnetic resonance imaging scans showed a correct position of the spinal cord without edema and the patch at T 2/3 (Fig. 2a, b). Four weeks after surgery the weakness in the patient’s left leg had significantly decreased although there was a remnant of the spastic paraparesis. The loss of temperature and pain sensation in the right leg remained unchanged. ISCH is a rare pathological entity with only about 110 cases being reported so far. The initially unspecific symptoms and the slow progression of the disease make the clinical diagnosis rather difficult. The diagnosis can be made by MRI which shows ventral displacement of the spinal cord with dorsal widening of the subarachnoid space. The etiology of the disease has been hypothesized to be congenital [5, 7], traumatic [1, 8], spontaneous [2, 4, 9], iatrogenic and inflammatory; however, no proof exists for any of these explanations. In most of the cases the affected levels range between T 4 and T 7. Many patients are of middle age with a female predominance. In the beginning the symptoms are unspecific. The symptoms progress slowly over years. In more than 70 % a slowly progressing Brown-Sequard syndrome or spastic asymmetric paraparesis can be found. Only a few cases reported in the literature were treated conservatively [1, 3, 6]. These patients refused surgery LETTER TO THE EDITORS