Abstract and Introduction
Intracranial hypotension may have variable clinical presentations, but has a rather uniform component of postural headache among its symptomatology. Its symptoms are explainable given the effects of the hypotension and attempts within the craniospinal axis to maintain volume homeostasis in the face of cerebrospinal fluid leakage (MonroKellie hypothesis). The imaging corollaries of the consequences of intracranial hypotension are especially well depicted on magnetic resonance imaging studies.
The syndrome of ICH is a single pathophysiological entity of diverse origin. Usually, it is characterized by an orthostatic headache, that is, one that occurs or worsens with upright posture, although patients with chronic headaches or even no headache have been described. The nature and location of the headache vary greatly from patient to patient; but consistently the pain is exacerbated by laughing, coughing, jugular venous compression, and Valsalva maneuver, and is resistant to treatment with analgesic agents.[24,42] In addition to headache, patients may experience nausea, vomiting, anorexia, neck pain, dizziness, horizontal diplopia, changes in hearing, galactorrhea, facial numbness or weakness, or radicular symptoms involving the upper limb, all of which are orthostatic in nature. Intracranial hypotension generally is considered to be a benign condition, and most cases resolve with conservative management. With advances in diagnosis, however, atypically disabling presentations are increasingly recognized including parkinsonism, frontotemporal dementia, syringomyelia, hypopituitarism, seizures, coma, and death.[4,11,16,18,24,49]
The diagnosis of ICH usually can be confirmed by demonstrating decreased CSF opening pressure, often less than 60 mm H20, on performing an LP. In some cases, spinal pressure may be so low that Valsalva maneuver or gentle aspiration with a syringe is required to produce CSF. Rarely, a "sucking noise" has been described to occur as the stylet is withdrawn and air enters the subarachnoid space, indicating subatmospheric pressure. Analysis of the CSF may show it to be entirely within normal limits, but more often increased protein concentration, lymphocytic pleocytosis, increased erythrocyte count, and/or xanthochromia are identified at some point during the patient's illness. Cultures of CSF are always nondiagnostic, and glucose levels are never low.
There is strong evidence indicating that most cases of ICH result from a persistent CSF leak. Such a leak most commonly occurs after dural puncture for a diagnostic LP, myelography, or spinal anesthesia. Nonetheless, symptoms of ICH may be experienced any time the dura mater is violated, such as after craniotomy, spinal surgery, craniospinal trauma, or placement of a ventriculoperitoneal shunt. In some cases, this syndrome may occur in the absence of an identifiable precipitant and, in fact, is believed to have developed spontaneously. Medical causes of ICH include dehydration, diabetic coma, hyperpnea, uremia, and severe systemic illness. Loss of CSF caused by the formation of a thoracomeningeal fistula is a rare complication of thoracic surgery.
Advances in neuroimaging have improved our ability to diagnose ICH. In particular, findings on MR imaging studies that are characteristic of this syndrome have allowed physicians to appreciate its true incidence as well as its varied modes of presentation. Here we review the role that imaging modalities play in the diagnosis of ICH and the pathophysiological mechanisms that underlie its symptomatology, clinical findings, and neuroimaging abnormalities. Specific causes as well as treatment options will also be considered.
Neurosurg Focus. 2003;15(6) © 2003 American Association of Neurological Surgeons
Cite this: Intracranial Hypotension Syndrome: A Comprehensive Review - Medscape - Dec 01, 2003.