Background context: Intracranial hypotension (IH) is a syndrome in which volume depletion of the cerebrospinal fluid (CSF) results in various neurological symptoms. Most commonly, a small tear or defect in the spinal dural sac is the underlying lesion that results in a CSF leakage and IH. Causes of IH can be classified as 1) spontaneous (primary), and 2) secondary. Knowledge of IH is essential to spine surgeons, because a small proportion of patients with spontaneous IH require spine surgery, and secondary causes of IH include spine trauma, various spine-related diagnostic/therapeutic procedures (iatrogenic), and degenerative spine disorders.
Purpose: The purpose of this review is to update knowledge of IH pertinent to spine surgery.
Study design/setting: Review of the literature.
Methods: A systematic review of the literature was conducted using PUBMED. The literature regarding IH with spinal pathology published from 1966 to 2005 was searched and reviewed comprehensively.
Results/conclusions: The lower cervical and upper thoracic spine are the predilection sites for a CSF leak in patients with spontaneous IH. Mechanical stress may have a role in the pathogenesis of spontaneous IH, and meningeal diverticula and connective tissue disorders may be important risk factors. Iatrogenic causes of IH include lumbar puncture, spine surgery, and chiropractic manipulation. Rarely, degenerative spine disorders are the secondary cause of IH. Although orthostatic headache is the characteristic symptom of IH, a small proportion of patients present with neck pain or radicular symptoms of the upper extremity. Imaging studies of the spine have contributed significantly to elucidation of the pathophysiology of IH as well as identification of the site of a CSF leak. Typical spinal radiographic findings of IH include extra-arachnoid or extradural fluid collections, meningeal enhancement, engorgement of the epidural venous plexus, and tonsilar descent into the foramen magnum. Most patients with spontaneous IH respond favorably to conservative management, including autologous epidural blood patch. Surgical intervention is reserved for those who fail the conservative management. Although immediate clinical improvement is usually achieved by surgery, the long-term outcomes of surgical patients need to be investigated further. In patients who have a secondary cause of IH, treatment of the underlying lesion or condition may terminate a CSF leak and result in reversal of symptoms.