An unusual case of Brown-Sequard syndrome

Abstract

Idiopathic spinal cord herniation (ISCH) is a rare condition presenting as progressive Brown-Sequard syndrome in 66% of patients [1]. Other presentations include symmetrical spastic paraparesis (30%) or less commonly, pure sensory or motor deficits. The spinal cord protrudes through a ventral or ventrolateral dural defect, causing unilateral distortion to the lateral funiculus and giving rise to progressive neurological symptoms. The mean age at presentation is 53 years with a 2:1 female preponderance. First described by Wortzmann in 1974, there are now over 120 cases reported in the literature, however its pathogenesis remains unknown [1]. Postulated pathogenic mechanisms include both congenital dural abnormalities and acquired dural injury leading to cord herniation, exacerbated by cerebrospinal fluid pulsations during the cardiorespiratory cycle. The progressive nature of symptoms may be explained by the intra-operative observation of tethering of the cord at the margins of the dural defect [1–3]. The anatomy of the thoracic spinal cord is thought to contribute to the predisposition of ISCH to the thoracic cord. The thoracic kyphosis and the natural ventral position of the cord in themid-thoracic levels, combined with repeated flexion and extension movementare believed to aggravatedural injury in the thoracic region [4]. Diagnosis of ISCH ismadebyMRI.Diagnostic features includeventral displacementor ‘‘kinking’’ of the spinal cordat the level of thedural defect, enlargement of the dorsal subarachnoid space, cord signal changes and atrophic changes with thinning of the cord. Phase contrast MRI can be helpful in differentiating from an arachnoid cyst [5]. Surgical management of this patient involved a T6–T7 laminectomy and durotomy (Fig. 1). The herniated cord was gently retracted and the hernial orifice obliterated using a dural patch. At discharge on post-operative day 4, weakness was markedly improved with nearly full power, and sensation and reflexes were normal. The patient returned 3 months post-operatively for follow-up MRI (Fig. 2).